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diff --git a/darwin/biblio/.SeekingWisdom.txt.swp b/darwin/biblio/.SeekingWisdom.txt.swp Binary files differ. diff --git a/darwin/biblio/Darwin et l’après Darwin_ Une histoire de l’hypothèse de -- Jean Gayon -- Histoire des idées, Paris (2, Impasse des Peintres 75002), -- EDITIONS KIME -- 9782841748372 -- 2a79d021c197ad6d3c.ds8skgMI.epub.part b/darwin/biblio/Darwin et l’après Darwin_ Une histoire de l’hypothèse de -- Jean Gayon -- Histoire des idées, Paris (2, Impasse des Peintres 75002), -- EDITIONS KIME -- 9782841748372 -- 2a79d021c197ad6d3c.ds8skgMI.epub.part Binary files differ. diff --git a/darwin/biblio/Darwin et l’après Darwin_ Une histoire de l’hypothèse de -- Jean Gayon -- Histoire des idées, Paris (2, Impasse des Peintres 75002), -- EDITIONS KIME -- 9782841748372 -- 2a79d021c197ad6d3c.epub b/darwin/biblio/Darwin et l’après Darwin_ Une histoire de l’hypothèse de -- Jean Gayon -- Histoire des idées, Paris (2, Impasse des Peintres 75002), -- EDITIONS KIME -- 9782841748372 -- 2a79d021c197ad6d3c.epub diff --git a/darwin/biblio/SeekingWisdom.txt b/darwin/biblio/SeekingWisdom.txt @@ -0,0 +1,11354 @@ +Seeking Wisdom: From Darwin to Munger Peter Bevelin PCA Publications L.L.C. (2007)/Riddler Rating: **** + +[1mPeter Bevelin begins his fascinating book with Confucius' great wisdom: [0m[1m[3m"A man who has committed a mistake and doesn't correct it, is committing another mistake." [0m[0mSeeking Wisdom is the result of Bevelin's +learning about attaining wisdom. + +His quest for wisdom originated partly from making mistakes himself and observing those of others but also from the philosophy of super-investor and Berkshire Hathaway Vice Chairman Charles Munger. A man +whose simplicity and clarity of thought was unequal to anything Bevelin had seen. In addition to naturalist Charles Darwin and Munger, Bevelin cites an encyclopedic range of thinkers: from first-century BCE +Roman poet Publius Terentius to Mark Twain-from Albert Einstein to Richard Feynman-from 16th Century French essayist Michel de Montaigne to Berkshire Hathaway Chairman Warren Buffett. In the book, he +describes ideas and research findings from many different fields. This book is for those who love the constant search for knowledge. It is in the spirit of Charles Munger, who says, "All I want to know is +where I'm going to die so I'll never go there." + +There are roads that lead to unhappiness. An understanding of how and why we can "die" should help us avoid them. We can't eliminate mistakes, but we can prevent those that can really hurt us. Using exemplars +of clear thinking and attained wisdom, Bevelin focuses on how our thoughts are influenced, why we make misjudgments and tools to improve our thinking. + +Bevelin tackles such eternal questions as: + +Why do we behave like we do? What do we want out of life? What interferes with our goals? Read and study this wonderful multidisciplinary exploration of wisdom. It may change the way you think and act in +business and in life. + +[1mSEEKING WISDOM [0m + +FROM DARWIN + +TO MUNGER + +PETER BEVELIN + +CONTENTS + +Part One One + +Two + +Three + +Part Two One Two + +Part Three One + +Two + +Three Four Five Six Seven Eight Nine + +Part Four One + +Two Three Four Five Six Seven Eight Nine Ten Eleven Twelve + +WHAT INFLUENCES OUR THINKING + +Our anatomy sets the limits for our behavior Evolution selected the connections that produce useful behavior for survival and reproduction Adaptive behavior for survival and reproduction + +THE PSYCHOLOGY OF MISJUDGMENTS + +Misjudgments explained by psychology Psychological reasons for mistakes + +THE PHYSICS AND MATHEMATICS OF MISJUDGMENTS + +Systems thinking Scale and limits Causes + +Numbers and their meaning + +Probabilities and number of possible outcomes Scenarios + +Coincidences and miracles Reliability of case evidence Misrepresentative evidence + +GUIDELINES TO BETTER THINKING + +Models of reality Meaning Simplification Rules and filters Goals Alternatives Consequences Quantification Evidence + +Backward thinking Risk + +Attitudes + +Charles T. Munger speech on prescriptions for guaranteed misery in life Wisdom from Charles T. Munger and Warren E. Buffett + +Probability Checklists + +To my two children, Victor and Sonia + +SEEKING WISDOM + +From Darwin to Munger + +By Peter Bevelin Third Edition + +Copyright© 2003, 2005, 2007 by Post Scriptum AB. All rights reserved. + +For permission to use copyrighted material, grateful acknowledgment is made to + +the copyright holders on next page, which is hereby made part ofthis copyright page. The author and publisher extend their apologies for any errors ofomissions and encourage any copyright owners inadvertently +missed to contact them. Any errors, oversight or omissions will be corrected in subsequent editions. + +Original publisher Post Scriptum AB + +Stora Nygatan 25, S-211 37 Malmo Sweden Fax + 46 40 97 42 66 + +PCA Publications L.L.C. Published under license from Post Scriptum AB, copyright owner. + +Disclaimer ofWarranties and Exclusions ofDamages: The author and publisher make no representations or warranties with respect to the accuracy or completeness ofthe contents ofthis book and specifically +disclaim any implied warranties ofmerchantability or fitness for a particular purpose. The advice and strategies contained herein may not be suitable for your situation. You should consult with a professional +advisor before making any financial or life style decisions. Neither the publisher nor the author shall be liable for any loss of profit or any other commercial damages, including but not limited to special, +incidental, consequential, or other damages. + +Some ofthe names, characters, places and incidents in this book are products of the author's imagination or are used fictitiously. Any resemblance to actual events, locales, or persons, living or dead, is +entirely coincidental. + +Printed in the United States ofAmerica by Walsworth Publishing Company. ISBN-13: 978-1-57864-428-5 (hard cover: alk. paper) + +ISBN-IO: 1-57864-428-3 (hard cover: alk. paper) + +For more information, please contact Peter Bevelin, AB Possessor Stora Nygatan 25, S-211 37 Malmo, Sweden or by e-mail to p.bevelin@possessor.se + +- PERMISSION ACKNOWLEDGMENTS - + +Excerpt from "Track record is everything." From Across the Board, October 1991. Copyright + +© 1991 by Across the Board. Reprinted by permission of The Conference Board Review; all rights reserved. + +Excerpts from Berkshire Hathaway Inc. Annual Reports and An Owner's Manual. + +Copyright © 1977-2006 by Warren E. Buffett. Reprinted by permission of Warren E. Buffett; all rights reserved. + +Excerpts from Darwin, C.R. 1871. lhe decent of man, and selecion in relation to sex. + +London: John Murray, 1st edition. Volume 1. Copyright © 2002-2007 lhe Complete Work of Charles Darwin Online - University of Cambridge - CRASSH 17 Mill Lane - Cambridge; all rights reserved. + +Excerpt from Forbes Magazine. "The not-so-silent partner" by Robert Lenzner and David + +S. Fondiller, January 22, 1996. Copyright © 1996 by Forbes Inc. Reprinted by permission of Forbes Magazine© 2009 Forbes Media LLC; all rights reserved. + +Excerpt from Cheating Monkeys and Citizen Bees: lhe Nature of Cooperation in Animals and + +Humans, by Lee Dugatkin. Copyright © 1999 by Lee Dugatkin. Reprinted with the permission of The Free Press, a Division of Simon & Schuster, Inc. + +Excerpt from Living Within Limits: Ecology, Economics, and Population Taboos, by Garrett Hardin. Copyright © 1995 by Oxford University Press, Inc. Reprinted by permission of Oxford University Press, Inc.; all +rights reserved. + +Excerpt from The Ostrich Factor: Our Population Myopia, by Garrett Hardin. Copyright + +© 1999 by Oxford University Press, Inc. Reprinted by permission of Oxford University Press, Inc.; all rights reserved. + +Excerpt from lhe Psychology ofSpeculation, by Henry Howard Harper. Copyright© 1966 + +by Fraser Publishing Company. Reprinted by permission of Fraser Publishing Company. Excerpt from "Speed, Simplicity, Self-Confidence: An Interview with Jack Welch." + +Reprinted by permission of the Harvard Business Review. From "Speed, Simplicity, Self Confidence: An Interview with Jack Welch" by N. Tichy & R. Charan, Sept/Okt 1989. Copyright© 1989 by the Harvard Business +School Publishing Corporation; all rights reserved. Excerpt from OfPermanent Value: lhe Story ofWarren Buffett, by Andy Kilpatrick. Copyright + +© 2000 by Andrew Kilpatrick. Reprinted by permission of Andrew Kilpatrick; all rights reserved. + +Charles T. Munger. + +Excerpts from Outstanding Investor Digest (OID) are reprinted by permission from Outstanding Investor Digest, Inc. Copyright © 1986-2006; 295 Greenwich Street, Box 282, New York, NY 10007. All rights +reserved. Telephone: (212) 925 3885. Website: www.oid.com. Excerpts from "What is science?" by Richard Feynman. Reprinted with permission from lhe Physics Teacher, Vol. 7, Issue 6, Page 313-320, 1969. +Copyright © 1969, American + +Association of Physics Teachers, all rights reserved. + +Excerpt from transcript #105 of Adam Smith®'s Money Game. Copyright© 1998 by Adam Smith® Educational Productions Ltd. Reprinted by permission of Adam Smith® Educational Productions Ltd.; all rights reserved. + +Excerpt from lhe lheory of Investment Value, by John Burr Williams. Copyright © 1938 by John Burr Williams Jr. and John Burr Williams Family Trust. Published in 1997 by Fraser Publishing Company. Reprinted by +permission of John Burr Williams Jr. and John Burr Williams Family Trust; all rights reserved. + +- ACKNOWLEDGMENTS - + +Thanks to Charles Munger and Warren Buffett for their kind permission to quote extensively from their work. Thanks to Charles Munger who generously took the time to read the whole original manuscript. Thanks +to Warren Buffett for his early encouragement of my first private memorandum - the foundation for this book - and his compliments on this work. I am deeply grateful to Peter Kaufman for his generosity in +helping me getting this Third Edition into wide circulation. I am delighted to partner with him. + +Thanks also to Jim Ross at Hudson BookSellers in Omaha for his fine job in promoting the earlier editions of this book. Thanks also to Rose-Marie Strandberg at Printing. Thanks to Henry Emerson who permitted +me to quote from Outstanding Investor Digest. Thanks to Ralph Greenspan at the Neurosciences Institute for many fruitful discussions. Thanks also to Gerald Edelman. Always a source of knowledge and joy. I +would also like to thank the following people who kindly commented on some of the issues covered in this book: Tom + +Ackerman, Edward Beltrami, Charles Brenner, Nico Bunzeck, Bent Flyvbjerg, Daniel Gilbert, Mark Graber, Peter Gardenfors, Tom Hamill, Mathew Hayward, Vibeke Horstmann, John Ioannidis, Andrew Kilpatrick, Frank +Lambert, Chris Landsea, Jennifer Lerner, Richard Lucas, Ronald Newburgh, Robert Rauber, Robert Sapolsky, Kaveh Shojania, + +Maria Stromme, Philip Swigard, Nassim Taleb, W illiam Thompson, and Carl Zimmer. The reader shouldn't assume that any of these people agree with what I have written in this book. Any misconceptions, +deficiences or errors are mine alone. + +Thanks to JoAnna Barrett who gave valuable editing advice. + +Finally, I wish to thank my wife, Monica, who read every sentence with critical eyes. Whatever I have achieved in life I owe her. She is the wind beneath my wings. Monica, you are the best. + +Peter Bevelin + +INTRODUCTION + +PART ONE + +- CONTENTS - + +WHAT INFLUENCES OUR THINKING? + +1 + +One + +Our anatomy sets the limits for our behavior + +3 + +Two + +Evolution selected the connections that produce useful behavior + +for survival and reproduction + +11 + +Three + +Adaptive behavior for survival and reproduction + +21 + +PART Two + +THE PSYCHOLOGY OF MISJUDGMENTS + +37 + +One + +Misjudgments explained by psychology + +39 + +Two + +Psychological reasons for mistakes + +42 + +PART THREE + +THE PHYSICS AND MATHEMATICS OF MISJUDGMENTS + +115 + +One + +Systems thinking + +120 + +Two + +Scale and limits + +129 + +Three + +Causes + +135 + +Four + +Numbers and their meaning + +141 + +Five + +Probabilities and number ofpossible outcomes + +144 + +Six + +Scenarios + +158 + +Seven + +Coincidences and miracles + +165 + +Eight + +Reliability of case evidence + +169 + +Nine + +Misrepresentative evidence + +176 + +PART FouR + +GUIDELINES TO BETTER THINKING + +187 + +One + +Models of reality + +189 + +Two + +Meaning + +Three + +Simplification + +212 + +Four + +Rules and filters + +218 + +Five + +Goals + +223 + +Six + +Alternatives + +225 + +Seven + +Consequences + +228 + +Eight + +Quantification + +231 + +Nine + +Evidence + +238 + +Ten + +Back ward thinking + +244 + +Eleven + +Risk + +248 + +Twelve + +Attitudes + +252 + +Appendix One + +Charles T. Munger speech on prescriptions for + +guaranteed misery in life + +260 + +Appendix Two + +Wisdom from Charles T. Munger and Warren E. Buffett + +264 + +Appendix Three + +Probability + +278 + +Appendix Four + +Checklists + +287 + +Source Notes + +297 + +199 + +Bibliography 307 + +- INTRODUCTION - + +A man who has committed a mistake and doesn't correct it, is committing another mistake. + +- Confucius (Chinese thinker, 6th to 5th Century BC) + +Why do we behave like we do? American writer Mark Twain once wrote: "The character of the human race never changes, it is permanent." Why is it so? + +What do we want out of life? To be healthy, happy with our families, in our work, etc? What interferes with this? Isn't it often emotions like fear, anger, worry, disappointment, stress, and sadness caused by +problems, mistakes, losses, or unreal expectations? Maybe we misjudged people, situations, the time or some investment.We chose the wrong occupation, spouse, investment, or place to live. Why? + +This book is about searching for wisdom. It is in the spirit of Charles Munger, Vice Chairman of Berkshire Hathaway, Inc. who says, ''All I want to know is where I'm going to die so I'll never go there." +There are roads that lead to unhappiness. An understanding of how and why we can "die" should help us avoid them. + +This book focuses on how our thoughts are influenced, why we make misjudgments and tools to improve our thinking. If we understand what influences us, we might avoid certain traps and understand why others +act like they do. And if we learn and understand what works and doesn't work and find some framework for reasoning, we will make better judgments. We can't eliminate mistakes, but we can prevent those that +can really hurt us. + +How do we achieve wisdom? It is hard to improve ourselves simply by looking at our own mistakes. The best way to learn what, how and why things work is to learn from others. Charles Munger says, "I believe in +the discipline of mastering the best that other people have ever figured out.I don't believe in just sitting down and trying to dream it all up yourself Nobody's that smart. " + +The 16th Century French essayist Michel de Montaigne said: ''Anyone who + +wishes to be cured of ignorance must first admit to it." My quest for wisdom originates partly from making mistakes myself and observing those of others but also from the philosophy of Charles Munger. A man +whose simplicity and clarity of thought is unequal to anything I have seen. What especially influenced me + +were his lectures on worldly wisdom, many of them reproduced in the newsletter Outstanding Investor Digest. In one speech, he said that the best way to achieve wisdom was to learn the big ideas that underlie +reality. In another, he referred to Charles Darwin as one of the best thinkers who ever lived. Darwin's lesson is that even people who aren't geniuses can outthink the rest of mankind if they develop certain +thinking habits. + +To learn more about Darwin's habits, I started to read his autobiography and other writings about him. I found him to be a fascinating character and a wonderful lesson on objectivity. In his autobiography, +Darwin said: + +I think that I am superior to the common run of men in noticing things which easily escape attention, and in observing them carefully. My industry has been nearly as great as it could have been in the +observation and collection of facts. What is far more important, my love of natural science has been steady and ardent... From my early youth I have had the strongest desire to understand or explain whatever +I observed, that is, to group all facts under some general laws. These causes combined have given me the patience to reflect or ponder for any number of years over any unexplained problem. As far as I can +judge, I am not apt to follow blindly the lead of other men. I have steadily endeavoured to keep my mind free so as to give up any hypothesis, however much beloved (and I cannot resist forming one on every +subject), as soon as facts are shown to be opposed to it. + +Darwin reinforced my interest in understanding human behavior. To improve my own thinking, I read books in biology, psychology, neuroscience, physics, and mathematics. fu the 17th Century French philosopher +Rene Descartes said: "The reading of all good books is like conversation with the finest minds of past centuries." + +I started to write down what I learned. The result is this book. The ideas in it are built largely from the works and thoughts of others. fu the Roman poet Publius Terentius (c.190-159 BC) wrote: "Nothing has +yet been said that's not been said before." I have condensed what others have written in a usable form and added my own conclusions. + +In this book you find a broad-based collection of wisdom from outstanding scientists like Darwin, Albert Einstein, Richard Feynman, and two of the world's most successful businessmen and investors, Charles +Munger and the Chairman of Berkshire Hathaway, Warren Buffett. Albert Einstein once said that there are only a few enlightened people with a lucid mind and good taste within a century. Warren Buffett and +Charles Munger are such people. I owe a great debt to them whose messages have been instructional as well as encouraging. lfl had listened + +11 + +to them earlier in my life - so many expensive mistakes would have been avoided. They are my heroes! + +I advise all of you to read the annual reports of Berkshire Hathaway and Wesco Financial (Charles Munger is chairman). These reports are the best educational tools about how to think about investing and +business. The lessons also show us how to behave in life. + +This book has four parts. First, I explore what influences our thinking. This serves as a foundation. In the second part, I give examples of psychological reasons for misjudgments. The third part explores +reasons for misjudgments caused both by our psychology and a lack of considering some basic ideas from physics and mathematics. In the final part I reveal tools for better thinking. The appendix contains a +speech from Charles Munger and quotes from Munger and Warren Buffett. It also contains checklists. Checklists often eliminate biases and make it easier for us to be sure we've covered the important things. + +Why spend time studying wisdom? Charles Munger gives a compelling reason: "I think it's a huge mistake not to absorb elementary worldly wisdom if you're capable of doing it because it makes you better able to +serve others, it makes you better able to serve yourself and it makes life more fun.. .I'm passionate about wisdom. I'm passionate about accuracy and some kinds of curiosity." + +This book is for those who love the constant search for knowledge. I have focused on explaining timeless ideas. The number of pages I have devoted to each idea does not reflect on its importance. My goal is +to lay the foundation. + +16th Century Spanish writer Miguel de Cervantes said: "He that publishes a book runs a very great hazard, since nothing can be more impossible than to compose one that may secure the approbation of every +reader." You may feel that much has been ignored and what is left has been exaggerated. Since I am writing this, I take full responsibility for the content. Any mistakes or inaccuracies are my responsibility. +If you, the reader, are convinced that I am dearly wrong about anything in this book, please send me an e-mail at the address given in the beginning of the book. + +I have cited quotations from a wide range of sources. Some books and material have been especially useful. Obviously, books about Charles Darwin. Also speeches and reports from Charles Munger and Warren +Buffett. Most of these quotes are excerpted text from the excellent newsletter, Outstanding Investor Digest. The reader should refer to the source note section for the source of the excerpt. Robert Cialdini, +Regents Professor of Psychology at Arizona State University, gives an excellent summary of findings in social psychology in his great book Influence. Psychology Professors Daniel Kahneman and the late Amos + +lll + +Tversky's work on decision-making has also been useful. Richard Feynman (1918-1988), perhaps the most brilliant and influential physicist of modern times, was also a spellbinding teacher. I love his books and +autobiographies. The late Human Ecology Professor Garrett Hardin is one of my favorites. His books are treasures and offer many ways for dear thinking. I have also been fortunate to visit the Neurosciences +Institute in California. Every time I'm there, I learn something new about how our brain works. + +I sometimes write in terms of "we", and other times I address "you", the reader. Just remember, "you" includes me, the writer. Italian mathematician and philosopher Gian-Carlo Rota's said in Indiscrete +Thoughts: "The advice we give others is the advice that we ourselves need." + +Instead of writing "he" or "she", I have used "he". To quote the British zoologist, Professor of the public understanding of Science at Oxford University, Richard Dawkins from The Blind"Watchmaker: "I may +refer to the 'reader' as 'he', but I no more think of my readers as specifically male than a French speaker thinks of a table as female." + +Let's start the journey for wisdom. I hope it will be inspiring. + +Peter Bevelin April 2003 + +The Second Edition + +The Second Edition has no major changes. Two short paragraphs have been added to Part One regarding sources of genetic variation and the benefits of bacteria. Otherwise, there are only minor clarifications. I +have also corrected a few mistakes in the text. + +January 2005 + +The Third Edition + +The Third Edition has been revised. Some of the content in Part Two has been rearranged. New material has been added to all Parts. + +February 2007 + +IV + +- PART ONE - + +[1mWHAT INFLUENCES OUR THINKING? [0m + +And men should know that from nothing else but from the brain come joys, laughter and jests, and sorrows, grief, despondency and lamentations. And by this ... we acquire wisdom and knowledge, and we see and +hear and know what are foul and what are fair, what sweet and what unsavory... and by the same organ we become mad and delirious and fears and terrors assail us. + +- Hippocrates (Greek physician 460-377 BC) + +- ONE - + +OUR ANATOMY SETS THE LIMITS FOR OUR BEHAVIOR + +To understand the way we think and why we make misjudgments, we must first determine what influences our behavior. + +Why can't we fly? + +To do what we do today demands the proper anatomical foundation. To fly we need wings. To walk we need legs, to see we need eyes, and to think we need a brain. Our anatomy, physiology and biochemistry are the +fundamental bases for our behavior. + +If we change anatomy, we change behavior. Birds can't fly if their wings are + +located in an area where no bones are present to anchor them. Apes can't talk because they need speech organs and these must be positioned in a certain way. For example, a small change in how our speech +organs are positioned could make speech impossible. + +Another example on how a change in anatomy changes behavior comes from the Neurosciences Institute in California. In one experiment, scientists took a small portion of developing brain tissue from a quail and +put it into the same spot of a chicken embryo. When the chick hatched, it had both quail and chicken nerve cells. Depending on what cells were transplanted, the results were either a chicken that crowed like +a quail or a chicken that bobbed its head like a quail. + +Studies have also shown that damage to a part of the brain, the prefrontal cortex (lying behind the forehead and eyes), results in a tendency to show a high degree of disrespect for social norms, including +violent behavior. A classic example is that of railway construction foreman Phineas Gage. In 1848, he was victim of an explosion that drove an iron rod through the frontal region of his brain, damaging his +prefrontal cortex. Before the accident he was considered stable, dependable, industrious, and friendly. Phineas survived the accident, but his personality changed. He became a drifter who was unreliable, +arrogant, impulsive and inconsiderate. + +Other studies show that damage to the amygdala- a region of the brain, linked with emotional states and social behavior - reduces the tendency to feel and + +3 + +respond to fear. Stimulating the amygdala can elicit intense emotional reactions. In 1966, Charles Whitman killed 14 people and wounded 38 from the clock tower at the University of Texas, Austin. An autopsy +revealed he had a tumor pressing against his amygdala. + +It is our brain, its anatomy, physiology and biochemistry and how these parts function that set the limits for how we think. But since our brain's parts also interact with our body's anatomy, physiology and +biochemistry, we must see brain and body together. They are part of the same system - us. + +Let's consider the anatomy of our brains to get a better understanding of what influences our behavior. + +What we feel and think depends on neural connections + +A lot is known about the brain, but far from everything. There are many controversies and unanswered questions. + +Nobel Laureate Dr. Gerald Edelman, director of the Neurosciences Institute says: + +The brain is the most complicated material object in the known universe. If you attempted to count the number of connections, one per second, in the mantle of our brain (the cerebral cortex), you would finish +counting 32 million years later. But that is not the whole story. The way the brain is connected - its neuroanatomical pattern - is enormously intricate. Within this anatomy a remarkable set of dynamic events +take place in hundredths of a second and the number oflevels controlling these events, from molecules to behavior, is quite large. + +Weighing only three pounds, the brain is composed of at least 100 billion nerve cells or neurons. It also contains tens of billions of other cells called glial cells supporting neurons. Neurons are connected +to other neurons and interact. Each neuron has a cell body with tiny branches called dendrites that receive information from other neurons. Extending from the cell body is long fibers called axons that send +information to other neurons. + +Since it is the connections between neurons that cause our mental capacities, it is not the number of cells that is important but the number of potential connections between them. + +How do neurons connect and communicate? + +Every neuron can connect with other neurons at contact points, the space between one neuron and another, called synapses. When a neuron fire an electrical impulse down the axon, the impulse is released as a +chemical substance + +4 + +called a neurotransmitter. When this chemical reaches the dendrite of another neuron it triggers an electrical impulse. Thereafter a series of chemical reactions begins. Some stimulation must happen for the +neuron to fire. The strength of this firing and what kind of neurotransmitter is released depends on the incoming stimuli. + +How does the neurotransmitter cause the electrical impulse? On the surface of the receiving neuron are proteins called receptors and every receptor is tailor made for a specific chemical. The chemical acts as +a key, and the receptor, or the lock, only "lets in" the right chemical. + +Why does it feel good when our loved ones give us a kiss or a compliment? + +It is the neurotransmitter dopamine that is being released. Dopamine is involved in the brain's reward and motivation system, and in addiction. High levels of dopamine are believed to increase feelings of +pleasure and relieve pain. + +Another neurotransmitter is serotonin. Serotonin is linked with mood and emotion. Too much stress can lead to low levels of serotonin and low levels are associated with anxiety and depression. What happens +when we take an antidepressant drug? The drug increases the amount of serotonin in our brain. The drug mimics the structure of serotonin. Antidepressants don't make us happy; they just treat the state of +unhappiness. Observe that even if neurotransmitters and the drugs that affect them alter our mental functions, they are part of a complicated system of interactions between molecules, cells, synapses, and +other systems, including life experiences and environmental factors. + +So far we know that the brain is a chemical system, and that neurons commu nicate with each other through the release of neurotransmitters (chemicals that carry messages between neurons). What we think and +feel depends on chemical reactions. And these chemical reactions are a function of how our neurons connect. What determines how these neurons connect and their patterns? Our genes and life experiences, +situational or environmental conditions, and a degree of + +randomness. + +Genes control brain chemistry but are turned on and off by the environment + +What is a gene? What does it do? + +Genes are what makes an individual, for example, to be built with two blue eyes, two arms, one nose, and a brain with certain architecture. + +Our body is made up of different types of interconnected cells functioning together. Each cell has 46 chromosomes or a chain of genes. 23 chromosomes come from each parent. Every chromosome is made up of the +chemical DNA or + +5 + +deoxyribonucleic acid. DNA is our inheritance; half is from our father and half from our mother. Genes are segments of our DNA and the units of our inheritance. A gene consists of four chemical molecules: +adenine, cytosine, guanine, thymine or A, C, G and T joined together in a chain. The short chemical name for a chain of any number of these molecules, in any order, is DNA. The order of these molecules +provides coded instructions for everything a cell does. + +The job of genes is to make proteins - the building blocks oflife. Proteins are molecules that carry out most of our biological functions and are made up of amino acids. There are twenty kinds of amino acids +that can be used to make our skin, hair, muscles, etc. Some proteins called enzymes cause certain chemical reactions. One example is neurotransmitters. Proteins are also hormones that act as messengers +between our cells. + +Sometimes a gene is "switched off" and can't make proteins. Messenger RNA is a genetic material that translates DNA into specific proteins. The Laureates of the Nobel Prize in Medicine, 2006, discovered a +mechanism called RNA interference that could "switch off" a gene by blocking this process. RNA interference plays a key role in our defenses against viral infections. + +Recent studies also suggest that genes do more than make proteins. For example, there is a gene in yeast that turns on and off another protein-producing gene without making any protein itself + +Every living thing uses the same genetic code - from cats to humans. This means we can transfer a single human gene into a cat and the cat "can read it" and follow its instructions. But no individual has the +same DNA or the same versions of genes (except for identical twins). Not all things are "spelled" alike. That's why people differ in eye color, height, etc. The closer related one living thing is to another, +the fewer spelling differences. But even if the differences are small, gene expression - where and when they are turned on or off and for how long - is the key. As an example take our closest relative - the +chimpanzee. Genetic studies show that humans and chimpanzees share at least 94% of their DNA sequences. This means that less than 6% of our DNA is responsible for the traits that make us different from +chimpanzees. What causes the large difference in behavior? Studies show that the human brain shows strikingly different patterns of gene expression compared to the chimpanzee's brain. + +Since we inherit all of our genes from our parents, why don't we look like a mixture of them? + +In most organisms, genes come in pairs. We inherit two versions of each gene for + +a particular trait (for example one version for blue eyes and one for brown eyes) + +6 + +from each parent. When a father and mother's genes combine, the effect of one gene may dominate the effect of the other. Certain characteristics are dominant. This is why a child who has one parent with blue +eyes and one with brown doesn't have eyes that are a blend of blue and brown. The child has brown eyes because the brown-eyed gene won the race. Blue eyes are recessive. But since the child inherited the +blue-eyed gene, it could still be passed on to future generations. Since the recombination of the versions happens by chance, they can always produce a new combination. On the other hand, if both the child's +parents have blue eyes, the child has no choice but to be blue-eyed. + +Some versions of genes are dominant, in some cases they blend, and sometimes we'll see an equal expression of both versions. Since several pairs of genes govern most traits, lots of combinations are possible. + +Interaction and flexibility characterize our biological functions + +Does each gene have its own specific part to play? + +No, we can't isolate one gene as causing something or arrange them in order of importance. They are part of an interconnected system with many possible combinations. And most genes contribute to more than one +characteristic. Genes can have different effects, depending on where, when and how they are switched on. Interaction is a fundamental property in biology. There are interactions between molecules, genes, +neurons, brain regions, cells, organs and among these individual systems. Each system does its own job but they are all coordinated to produce a functional and unique individual. + +But doesn't the left and right side of the brain have different functions? Dr. Ralph Greenspan at the Neurosciences Institute says: + +... although in some sense it's poetic to speak of a "right brain/left brain'' difference. The fact of the matter is that things that are "right brain" are really happening everywhere and things that are +"left brain" are really happening everywhere. There are certain aspects ofit that may be more biased to one side versus another, but the brain is not highly localized in any sense at all. Everything that ever +happens in your brain is happening as a unification of many, many, many areas at once. + +He continues: + +Isaac Newton might have liked the neat view of biological systems made up of dedicated components, with causal roles that can be studied in isolation, and in which particular conditions give rise to uniquely +predictable responses. Charles Darwin, by contrast, might + +7 + +have felt more at home with the idea of a complex, emergent system made up of many non-identical components, with non-exclusive roles, non-exclusive relationships, several ways of producing any given output, +and a great deal of slop along the way. + +The most striking result of our interactive network is flexibility. A flexibility to take on new roles as conditions changes and an ability to produce the same result in different ways. For example, studies +show that different configurations between neurons can achieve the same result. The configuration depends on which alternatives that are available at a given moment in a given situation (since behavior +depends on context or situation), an individual's life experiences and an element of chance. Having alternative ways of producing the same outcome gives us a great benefit. For example, we can compensate for +injuries and readapt to new conditions. + +Do our genes have a lift of their own? + +No, gene expression depends on environmental conditions. Genes control the chemistry in the brain but need to be activated by the environment. An environmental event must switch them on, or modify their level +of activity, before they can start making proteins that influence neural connections. Our genes determine if we inherit a particular characteristic but it is the environment that causes our genes to make +proteins that produce certain "response tendencies." So our behavior emerges from the mutually dependent activity of genetic and environmental factors. + +Neural connections are shaped by life experiences + +The brain changes continually as a result of our experiences. Experiences produce physical changes in the brain either through new neural connections or through the generation of new neurons. Studies suggest +that the brain can change even during the course of a day. This means that the anatomy of the brain varies from individual to individual. Even identical twins with identical genes don't have identical brains. +They have had different life experiences. + +Experiences are the reason that all individuals are unique. There are no individuals with exactly the same upbringing, nutrition, education, social stamping, physical, social and cultural setting. This +creates different convictions, habits, values and character. People behave differently because differences in their environment cause different life experiences. This is why it is sometimes hard to understand +other people's behavior. To do that, we must adapt to their environment and share their experiences. This is often impossible. + +8 + +If we encounter a stressful situation, how we respond depends on what we were born with, what we have experienced, and the specific situation. Assume that a person "Sam" and you both have genes for "being +fearful." You are standing in a Savannah in Africa and are approached by a lion. Do both of you show the same reaction when exposed to the same situation? You are afraid but not Sam. Sam either knows that +this lion is tame or Sam is a lion tamer. Sam's reaction comes from his life experiences. Sam may also be genetically predisposed to react differently to certain dangers. But even if Sam has a low genetic +vulnerability to fear, he can develop a fear of the lion. One horrifying experience with a lion may be enough. + +Behavior is influenced by our state of mind + +Our life is what our thoughts make it. + +Marcus Aurelius Antoninus (Roman emperor and philosopher, 121-180) + +Our state of mind is a function of our life experiences and the specific situation. Assume (1) we are eating tasty chocolate, listening to wonderful music and feeling relaxed or (2) we suffer from a cold, +feel stressed and just ate a bad meal. If we have to make a judgment, will it be the same in both cases? Probably not, since our state of mind is different in case 1 and 2. + +Can our state of mind influence our biochemistry and immune system? + +It's not just what happens to us that counts - it's what we think happens to us. We convert our expectations to a biochemical reality meaning that our mental state and physical well-being are connected. + +A placebo effect is a positive therapeutic effect that has nothing to do with the efficiency of a treatment, only with a patient's belief in the treatment. Whenever patients believe that a treatment will have +a particular physiological, behavioral, or psychological effect, they are susceptible to placebo effects. + +The doctor gave me a pain-relief drug (when in fact it was a sugar pill) and after a short time I experienced significantly less pain. + +A placebo is an inactive or ineffective treatment or substance (for example, sugar pills or injections with saline solution) that is often used in comparison with active treatments. Studies show that a +placebo can improve a patient's condition simply because the patient expects it will work. Clinical evidence shows placebos to have physical effects on the brain, just as drugs do. Studies in Sweden show that +a placebo activates the same brain circuits as painkilling drugs. Nine male + +9 + +students were asked to voluntary participate in a study of painkilling drugs. Researchers first tested for the degree of pain the subjects would experience when a 48-degree Celsius metal surface was pressed +to the backs of their hands. The test was repeated after the subjects were given a painkilling drug. + +Later the subjects were told to test two new painkilling drugs and that one of these drugs was similar to the one they earlier tested. Once more the 48-degree metal surface was pressed to the backs of their +hands. A man in a white coat, carrying a badge that said "professor", then entered the room. The "professor" gave the subjects intravenous injections of either an opioid (a drug acting like a drug made from +opium) painkiller or a placebo. During the experiment researchers scanned the subjects' brains and compared brain responses. Both the painkiller and the placebo produced the same effect. Both increased blood +flow in areas of the brain known to be rich in opioid receptors. Eight of the nine subjects said that the placebo produced a clear relief from the pain. + +Other studies show that people who take sugar pills as a treatment for depression and other ills can undergo striking, although temporary, changes in brain activity and neural chemistry as their condition +improves. It has also been shown that placebos can improve blood pressure, cholesterol level and heart rate. It's like a pharmacy inside the body that has evolved during million of years of evolutionary time. + +What happens when a healthy person finds out he may die? + +Studies show that if people expect something to go wrong with their health, it often does. Negative expectations can influence our bodies and cause symptoms that over time may cause our body harm. In one +study, women who expected that they were inclined to heart attack were nearly four times as likely to die as women with similar risk factors but without these expectations. Another study found that patients +who were warned about the gastrointestinal side effects of taking aspirin were three times more likely to feel them. Other studies show that if people worry about drug side effects, they are more likely to +get them. Beliefs have biological consequences - good and bad. + +Our genes and life experiences determine how neurons connect thereby influencing and setting the limits for our behavior. We were born with the basics of life. We had neural connections that regulated our +breathing, heartbeat, temperature, etc. How does our brain select those neural connections that produce useful behavior? Our brain is a product of evolution. + +10 + +- Two - + +EVOLUTION SELECTED THE CONNECTIONS THAT PRODUCE USEFUL BEHAVIOR FOR SURVIVAL AND REPRODUCTION + +What do we mean by evolution? + +Evolution is change (structural, physiological, behavioral) - which occurs over time through interaction with the environment. Paleontology Professor John Horner says in Dinosaur Lives: "When you flip through +the pages of the family album you're witnessing evolution at work." + +The theory behind evolution is that all individuals alive today have evolved from simpler, more primitive forms oflife. Since every living thing uses the same genetic code, it is likely that life descended +from a distant common ancestor that had that code. If a monkey and we and any other organism trace our ancestors back far enough, we eventually find a common ancestor. + +What major mechanisms are responsible for evolution and for how our brain evolved? Mutation and natural selection. + +Mutations cause variations + +Mutations are caused by a copying error in the sequence of A, C, G and T molecules when DNA is copied. This error in the genes "spelling" may cause a change in a protein leading to a modification in the +individual that inherits the gene. For example, the new instruction could be"build Peter with adifferent eye-color." Since the change is random and unpredictable, no one can tell which gene(s) may be +involved. + +Natural selection + +I have called this principle, by which each slight variation, + +if usefol, is preserved, by the term Natural Selection. + +Charles Darwin (British naturalist, 1809-1882) + +Charles Darwin, and independently the British naturalist Alfred Russell Wallace, discovered the theory of evolution by natural selection. Darwin called his work On the Origin of Species by Means of Natural +Selection, or the Preservation of Favoured Races in the Struggle for Life. + +Darwin was inspired by the Reverend Thomas Malthus's An Essay on the + +11 + +Principle of Population in which Malthus wrote: "Human population grows exponentially, like compound interest in a bank account, but farm output rises at a slower, arithmetic rate; the result, human +population will inevitably and repeatedly outstrip its food supply." Malthus noted that population can always outstrip resources but are held in check by diseases, war, predators, and by limited resources +like food. + +Darwin made the following three observations: + +[3m(I) [0mCompetition and environmental change. In most species (a species is a group of individuals capable of producing fertile offspring; like snakes, lion, humans) there are always more offspring born than can +survive to adulthood and reproduce. Darwin saw two reasons for this: (1) Since there is a limited amount of resources (like food, space, mates) there is competition between individuals for these resources, +and (2) Since the environment changes over time and from one region to another, there are threats (predators, change in climate, isolation, diseases, change in the physical environment) to the children's +survival and their reproductive success. + +Individual variability. Within a species, there is an enormous amount of + +individual variation. No two individuals of the same species are alike in their anatomical structure, physiology or behavior (we're not an exact copy of our parents). Individuals vary in their cell structure, +fighting ability, and social skills. Variations make every individual unique and that variation must in some way be heritable otherwise children wouldn't resemble their parents more than they resemble other +individuals. + +The world is not fixed but evolving. Species change, new ones arrive and + +others go extinct. + +Darwin called his principle natural selection. Any slight variation in traits that gives an individual an advantage in competing with other individuals of the same or different species or in adapting to +changes in their environment increases the chance that the individual will survive, reproduce, and pass along its characteristics to the next generation. Maybe they have greater resistance to disease, or can +run faster, or survive climate changes better. + +Darwin used the word "selection," but nature doesn't care who gets selected for survival. Evolution has no goal. Another way to describe natural selection is as a process of elimination. Certain individuals +survive because they have structural, physiological, behavioral or other characteristics that prevent them from being eliminated. Those that don't have these characteristics are eliminated. Heredity enhances +the likelihood that the non-eliminated or "selected" variations + +12 + +are preserved. Darwin didn't know about genetics. Therefore he couldn't know that these characteristics were caused by mutations and that they could be passed on through the genes. + +After a mutation changes an individual, the environment determines if the change gives the individual an advantage. If the new trait is helpful, the mutated individual is more likely to survive, reproduce and +pass the new trait to his children. Take a poisonous spider as an example. Assume that a population (a group of individuals belonging to one species that occupy the same geographic/ecological niche at the +same time) of black widows differs in how toxic their venom is. If some spiders (mutants) are born with more toxins than others, two things could happen over time. If more toxins give an advantage in the +spiders' environment, more toxins might be "selected" for and the "more-toxins" characteristic might be passed to children. If the more toxic black widow spiders survive and reproduce better than the less +toxic ones, then black widow spiders, will, over time, evolve more toxic venom. The frequency of the "more-toxic" spiders in the population increases over time. If there is no advantage, the trait disappears +and + +the population of less toxic spiders increases. + +When organisms undergo selection, some characteristic may be carried along that wasn't selected. Even if some trait didn't provide an advantage it could still be carried along as long as it isn't harmful, +i.e., doesn't negatively influence survival and reproduction. But a situation may arise in the future when that trait can become useful. + +What happens when the environment changes? + +Since environments change over time and with geography, different variants are "selected" under different conditions. Characteristics that are successful in one environment may be unsuccessful in another. +This is well expressed by the late American paleontologist Stephen Jay Gould in Wonderful Life: "Even if fishes hone their adaptations to peaks of aquatic perfection, they will all die if the ponds dry up." + +Studies show that different organisms respond differently to environmental stress. But there seems to be one creature that survives and reproduces independent of changes and stresses in the environment - the +cockroach. Writer Richard Schweid says in The Cockroach Papers, "If there is a God that made all life forms, a particularly rich blessing was bestowed on the roach, because it got the best design of all." + +The cockroach is the oldest insect on our planet as evidenced by fossil records dating back 325 million years. It can eat almost anything, live 45 days without + +13 + +food, and has an effective reproductive system with female sperm storing capabilities lasting a lifetime and a great defense system. The cockroach is about the same organism it was millions of years ago +because its characteristics were adaptive then and now. + +Often a new trait or a change in an individual doesn't occur through a single step but through a gradual accumulation of small mutations being selected over a long period of time. By dating meteorites, most +scientists say that the earth is about 4.6 billion years old. The oldest bacteria fossils go back 3.5 billion years. Given enough variation and time, even such a complicated thing as the eye hasgradually +developed. Evolutionary changes can act fast. Studies of fruit flies show that differences in wing size could take place in as little time as adecade. A change in a species' territory (e.g. climatic) can also +bring on rapid structural changes (variation). Other studies show that a change that involves few genes could come about faster (and cause large + +behavioral changes) than one that depends on small changes in many genes. + +Mutation is not the only source of genetic variation. Other mechanisms (sometimes interacting) are genetic drift, gene flow, and symbiosis. Genetic drift happens when random events cause gene frequencies to +vary between generations (more important in small populations). Gene flow or migration is the movement of genes in a species from one population to another as the result of interbreeding. For example, there +is evidence of gene flow between cultivated plants and their wild relatives. Symbiosis is the cooperative interaction between different organisms that can produce genetic changes. There is also co-evolution +or the parallel evolution of two species. Another source of variation is gene duplication or the accidental duplication of entire genes. So natural selection is not the only mechanism that changes organisms +over time. But it is the only known process that seems to adapt organisms over time. + +The evidence for evolution + +There is fossil, anatomical and molecular evidence of evolution. The fossil record shows how morphology was modified. Similarities of organs in related organisms show common ancestry. There is also DNA +fossils evidence where human relative relatedness can be measured by DNA sequencing. + +One example of evolution is industrial melanism. Before the Industrial Revolution in England, the color of the peppered moth was mainly light. When there was no industrial pollution, the darker moth cropped +up by mutation. But since the darker moths were easier to spot against the tree bark, hungry birds snapped them up. Only when the environment changed, when soot from new factories covered the tree trunks, did +darkness became an advantage. Selection + +14 + +began to favor the darker moth. Darker moths were better disguised on tree trunks covered by soot. The lighter moths were eaten and the darker ones increased in numbers. Around 1950 the environment started +changing again. A decrease in the use of coal and better filtering equipment in the factories produced a cleaner environment and the peppered moth is in the process of returning to its lighter color. + +Why aren't antibiotics as effective against dangerous bacteria as before? + +Evolution is at work today. Evidence of evolution is seen in pesticide resistance among insects and the antibiotic resistance of bacteria. + +There are a lot of bacteria around, and they can divide several times an hour. In any population of bacteria, there are some individuals that through mutations have developed genes causing them to escape +elimination. The more non resistant bacteria that are eliminated, the more opportunities for the resistant to reproduce and spread. Over time, the resistant bugs win the race, meaning the antibiotics become +less and less effective. Until someone develops a new type of antibiotic and then the race starts all over again. + +Bacteria are immensely adaptable. Expose them to antibiotics long enough, they adapt and find a way to survive. This also means that the more we use antibiotics, the faster resistance spreads. And any method +we use to kill bugs will, unless it completely wipes out a species, cause a population of resistant bugs. + +Just as we can't blame an animal for eating another animal to survive, we can't blame bacteria for giving us an infection. They have no intention of harming us. Bacteria do what comes natural to all of us - +survive and reproduce. + +Are bacteria always bad far us? + +No, they are important for our digestion and immune system. They are also vital for life on earth. Without them we wouldn't exist. In order to generate energy, we need oxygen. This oxygen is assumed to have +been generated by a group of bacteria called cyanobacteria (or blue-green algae), the light-harnessing microbes that live primarily in seawater. + +The key source of energy for nearly all life is sunlight. This light energy is transformed into chemical energy in plants, algae and certain bacteria by photosynthesis. For example, plants make their food- +usually glucose-from carbon dioxide (through leaves) and water (mainly through roots). Sunlight provides the energy needed to run the biochemical process that yields sugar and the by-product oxygen (that +water molecules contain) which is released into the atmosphere. When we eat plants (or animals that eat plants), we take in their stored energy. + +15 + +In plants, photosynthesis is handled by chloroplasts. They contain the molecule chlorophyll, allowing plants to absorb the energy from the sun. Chloroplasts may have evolved from cyanobacteria that were +fusioned with plants a long time ago. Fossil evidence shows that there were cyanobacteria-like microbes on earth 3.5 billion years ago. It is also believed that mitochondria (the non-bacterial cell structures +where oxygen is used to burn food for energy) evolved as a result from a fusion of different kind of bacterial cells. + +Another activity of some cyanobacteria is nitrogen fixation. For example, in plants from which beans or peas are taken, bacteria live in the roots and chemically convert (fix) atmospheric nitrogen into +ammonia useful to other organ1sms. + +Why isn't the world covered with dead plants and animals? + +Partly because bacteria breaks down the tissue of dead plants and animals into nutrients like carbon and nitrogen that are then released back into the environment. + +Go out and look at a recently dead bird. Then look at it a month later. There are only bones left. + +Thus, evolution selected the behavior that made our ancestors survive and reproduce. What guidance system has evolution selected to help us make better decisions for survival and reproduction? + +Guidance through values and life experiences Human beings are pulled forward toward and by nature seek pleasure, whereas they flee from and reject pain. + +- Epicurus (Greek philosopher, 341-270 BC) + +What drives us? + +The 17th Century English philosopher John Locke said: "Good and evil, reward and punishment, are the only motives to a rational creature: these are the spur and reins whereby all mankind are set on work, and +guided." We are driven by our need to avoid pain (and punishment) and a desire to gain pleasure (and reward). Evolution has made any behavior that helps us survive and reproduce feel pleasurable or rewarding. +Behavior that is bad for us feels painful or punishing. Feelings of pain and pleasure are a useful guide to what is good or bad for us. If we eat, we feel pleasure. If we starve ourselves, we feel pain. + +Harm avoidance first. Our brain is equipped to register pain more sensitively than any other emotion. We also remember negatively arousing stimuli better. + +16 + +Neurology Professor Antonio Damasio says in Descartes' Error that "it is the pain related signal that steers us away from impending trouble." It makes evolutionary sense that we have the desire to avoid pain. +Psychology Professor Randolph Nesse and Biology Professor George Williams say in Why We Get Sick: "Pain is the signal that tissue is being damaged. It has to be aversive to motivate us to set aside other +activities to do whatever is necessary to stop the damage." + +That we are sensitive to events or stimuli that have painful implications for us, explains why we have such an aversion to loss. Richard Dawkins says in The Blind Watchmaker: "However many ways there may be +of being alive, it is certain there are vastly more ways of being dead, or rather not alive." The fear ofloss is much greater than the desire to gain. Research shows that we feel more pain from losing than we +feel pleasure from gaining something of equal value and that we work harder to avoid losing than we do to win. That we pay more attention to possible losses than gains makes sense. In Steven Pinker's book, +How The Mind Works, social psychologist Timothy Ketelaar says, ''As things get better, increases in fitness show diminishing returns: more food is better, but only up to a point. But as things get worse, +decreases in fitness can take you out of the game: not enough food and you're dead." + +Our aversion to pain also encourages a certain human behavior: to take the most rewarding view of events. We interpret choices and events in ways that make us feel better. We often prefer to hear supporting +reasons for our beliefs; think of ourselves as more talented than others, and make the best of bad situations. + +How are certain connections strengthened? + +If certain connections help us interact with our environment, we use them more often than connections that don't help us. Since we use them more often, they become strengthened. + +Evolution has given us preferences that help us classify what is good or bad. When these values are satisfied (causing either pleasure or less pain) through the interaction with our environment, these neural +connections are strengthened. These values are reinforced over time because they give humans advantages for survival and reproduction in dealing with their environment. + +For example, light is preferred to darkness, eating certain food is better than not eating, etc. When we drank our mother's milk, our brains told us that "eating" was pleasurable. Our chance of survival +increased. If we didn't eat after we were born, the feedback from our brain would be that "not eating" was painful. The chances are that we ate in the future. Since the feedback from eating + +17 + +was pleasurable, certain neural connections were strengthened. In the future, when we were exposed to the same stimuli, this group of neurons reacted stronger. Any behavior that we find rewarding, either +pleasurable or less painful, are strengthened. + +The connections in our brain are constantly strengthened and weakened, developing and changing. The more we are exposed to certain experiences, the more the specific connections are strengthened, and the +better we learn and remember those experiences. We then use these stored representations of what works when we respond to people and situations. Essentially what we do today is a function of what worked in +the past. We adapt to our environment by learning from the consequences of our actions. We do things that we associate with pleasure and avoid things that we associate with pain. + +Does the brain work like a computer - systematically and logically? + +No, it is a selection system that puts together patterns among neurons. Dr. Ralph Greenspan says: + +In no sense does the brain work like a computer. Computers record, and computers have things stored in specific places that are stable. Our brains do none of that. When the great chess master Gary Kasparov +lost to Big Blue everybody said "Aha, this machine can think!" Big Blue was not thinking. Big Blue was simply replaying the entire history of chess. That's not the way that Gary Kasparov or any human being +plays chess. We do pattern recognition. Even though we are capable of logic, our brain does not operate by the principles oflogic. It operates by selection of pattern recognition. It's a dynamic network. It's +not an "if-then" logic machine. + +A chess computer has no pattern-recognizingability. Instead, it explores all the possible moves on a given chessboard. Chess-masters look for patterns and decide what to do based on what have worked well in +the past. Why? Because what worked in the past is most likely to work in the future. Warren Buffett follows up with: + +There was a great article in the New Yorker magazine ... when the Fischer/Spassky chess matches were going on. And it got into this speculation of whether or not humans would ever be able to take on computers +in chess. Here were these computers doing hundreds of thousands of calculations a second. And the article asked, "When all you're really looking + +at is the results from various moves in the future, how can a human mind deal with a computer that's thinking at speeds that are so unbelievable?"... + +18 + +Well, it turns out a mind like... that of a Fischer or a Spassky essentially was eliminating about 99.99% of the possibilities without even thinking about 'em. So it wasn't that they could outthink the +computer in terms of speed, but they had this ability of what you might call "grouping" or "exclusion", where essentially they just got right down to the few possibilities out of these zillions of +possibilities that really had any chance of success. + +Now we reach a key question: What part of the value system is called "human nature?" + +So far we've learned that connections between neurons determine how we think and behave. Our genes provide us with the framework for neural development and our life experiences and our environment shapes our +brain. + +Since the brain is formed by life experiences and since an individual doesn't keep doing what doesn't work (learns through trial and error), evolution has reinforced the behavior and values that help us +survive and reproduce. This behavior must be the behavior that was adaptive in the environment in which humans spent most of their evolutionary history. The question then becomes: What was the operating +environment in which the human brain evolved? + +The hunter-gatherer environment has formed our basic nature + +Human evolution started about 4 to 7 million years ago and today's "modern" human brain appeared on the scene some 150,000 to 200,000 years ago. For most of that time our ancestors lived in primitive +hunter-gatherer societies. These societies existed until the end of the last Ice Age, around 13,000 years ago. Soon thereafter, some 10,000 years ago, agriculture was developed. + +This means that humans have spent more than 99% of their evolutionary history in the hunter gatherer environment. If we compress 4 million years into 24 hours, and if the history of humans began at midnight, +agriculture made its appearance on the scene 23 hours and 55 minutes later. + +If the conditions and challenges of the hunter gatherer environment is the + +environment in which natural selection has selected the adaptive traits for survival and reproduction, we must find out what the environment looked like back then. What drove our ancestors' evolution? What +were the characteristics of the environment that have shaped today's brains? What were the environmental conditions in which the hunter-gatherers lived? What was the availability of resources like food and +mates? How was the climate and the geography? Social environment? Size of population? What enemies, predators, and dangers existed? There is no observational evidence from the hunter-gatherer environment. It +seems likely though, that the environment of our ancestors represented + +19 + +ecological, social and human conditions that are quite different from today. People were living in small villages where everyone knew everyone else and strangers didn't show up often. There were enemies, +predators and diseases. Limited resources created competition for food and mates. + +What different roles did men and women likely play? Men were responsible for hunting, and defending the group from predators and enemies. Women gathered and prepared food near the home, and cared for the +children. + +If this were the environment, what would be appropriate behavior to increase the likelihood for survival and reproduction? What behavior has been natural during 99% of our history? + +20 + +- THREE - + +ADAPTIVE BEHAVIOR FOR SURVIVAL AND REPRODUCTION + +The individual comes first + +There's no such thing as society. There are individual men and women, and there are families. + +- Margaret Thatcher (Former British Prime Minister) + +Do people do what they perceive is in their best interest? + +Yes, one basic trait that all individuals share is self-interest. We are interested in protecting our close family and ourselves. Why? + +Since natural selection is about survival and reproduction, and individuals either survive or die and reproduce or not, it makes sense that individuals are predisposed to act in ways that enhance their own +prospects for survival and reproduction. The ancestral environment consisted of limited resources, including reproductive resources, and fierce competition. Self-interest came naturally. + +What if our ancestors were composed of altruists - individuals that helped others at their own expense? Altruistic individuals are at a disadvantage. They are always vulnerable to some mutants that take +advantage of them. Altruistic behavior cannot evolve by natural selection since natural selection favors individuals that are best at promoting their own survival and reproductive success. Only behavior that +is selfish or for the mutual good is in an individual's self-interest and therefore favored by natural selection. Some behavior may under certain conditions look like altruism but can often be explained by +self-benefit. Social recognition, prestige, fear of social disapproval, shame, relief from distress, avoidance of guilt, a better after-life or social expectations are some reasons behind "altruistic" acts. + +But how did our social and moral qualities develop? As Charles Darwin wrote in + +chapter four of The Descent ofMan: "Whyshould a man feel that heought to obeyone instinctive desire rather than another? Why does he bitterly regret if he has yielded to the strong sense of self-preservation, +and has not risked his life to save that of a fellow creature; or why does he regret having stolen food from severe hunger?" In chapter five of the book, Darwin wrote that there is a: "powerful stimulus to +the development of the social virtues, namely, the praise and the blame of our fellow-men." + +21 + +The love of approbation and the dread ofinfamy, as well as the bestowal of praise or blame, are primarily due... to the instinct of sympathy; and this instinct no doubt was originally acquired, like all the +other social instincts, through natural selection ... We may therefore conclude that primeval man, at a very remote period, would have been influenced by the praise and blame of his fellows. It is obvious, +that the members of the same tribe would approve of conduct which appeared to them to be for the general good, and would reprobate that which appeared evil. To do good unto others -to do unto others as ye +would they should do unto you, - is the foundation-stone of morality. It is, therefore, hardly possible to exaggerate the importance during rude times of the love of praise and the dread of blame. A man who +was not impelled by any deep, instinctive feeling, to sacrifice his life for the good of others, yet was roused to such actions by a sense of glory, would by his example excite the same wish for glory in +other men, and would strengthen by exercise the noble feeling of admiration. He might thus do far more good to his tribe than by begetting offspring with a tendency to inherit his own high character. + +A high standard of morality would also benefit a tribe. Darwin continues: + +It must not be forgotten that although a high standard of morality gives but a slight or no advantage to each individual man and his children over the other men of the same tribe, yet that an advancement in +the standard of morality and an increase in the number of well endowed men will certainly give an immense advantage to one tribe over another. + +Often cooperation is in our best interest + +If people aren't altruistic by nature, are they cooperative? + +Mutual aid has tremendous survival value. But under what conditions do people cooperate? The game of the Prisoner's Dilemma may shed light on this: Suppose you and a partner commit burglary. Both of you are +picked up by the police who then question you one by one. There is not enough evidence to convict you unless one of you confesses. The interrogator gives you a choice to cooperate or not. + +''Jfyou both deny the crime, there is still enough evidence to put you both in jail for 1 year." + +"If you both confess, you both go to jail for 3 years. " + +''Jfyou confess but your partner denies, you will be free and your partner will go to jail for 10 years. " + +''Ifyou deny but your partner confesses, you will go to jail for 10 years. " + +What should you do? The consequences for you depend on what your partner + +22 + +does. From an outsider's perspective, it seems that both of you would be better off denying the crime (1 year). But from your point of view, it seems best to confess (freedom). The problem is that you don't +know what your partner will do. If your partner betrays you, it is better that you also betray him and get 3 years in prison, instead of the 10 years you get if you deny, but your partner ends up confessing. +If on the other hand your partner denies, it is still better that you confess because this way you will be free, instead of the 1 year you get if you deny. Since both you and your partner follow this "logic" +and confess, you will both go to jail for 3 years. Doing what you believe is in your best interest leads to a worse outcome than if you cooperate and deny. But here is the dilemma. You don't know if you can +trust your partner. Cooperation only works if you and your + +partner can trust each other. + +Tests show that if people play the game over and over, they learn that it is more profitable to cooperate. Repetition tests trust. Trust is key and fragile. It can vanish in a moment. As the 19th Century +American President Abraham Lincoln wrote: "If you once forfeit the confidence of your fellow citizens, you can never regain their respect and esteem." + +Another way to create cooperation is to let the partners communicate during the game. Talking encourages cooperation. Since people are social animals, they may change their behavior to keep others goodwill. +In the end, it's a matter of trust and giving individuals an incentive to cooperate. + +In chapter three of The Descent of Man, Charles Darwin wrote: + +At the moment of action, man will no doubt be apt to follow the stronger impulse; and though this may occasionally prompt him to the noblest deeds, it will far more commonly lead him to gratify his own +desires at the expense of other men. But after their gratification, when past and weaker impressions are contrasted with the ever-enduring social instincts, retribution will surely come. Man will then feel +dissatisfied with himself, and will resolve with more or less force to act differently for the future. This is conscience; for conscience looks backwards and judges past actions, inducing that kind of +dissatisfaction, which if weak we call regret, and if severe remorse. + +But we also have to recognize that communication may be deceptive. People may bluff Also, communications are imperfect- mistakes are made or intentions are misunderstood. + +The strategy that is effective in the long run is a modern version of"a tooth for a tooth" or TIT-FOR-TAT. It says that we should cooperate at the first meeting and then do whatever our "opponent" did the +last time. When our opponent + +23 + +cooperates, we should cooperate. When our opponent doesn't cooperate, we should retaliate. Then forgive and go back to cooperating next round. This rewards past cooperation and punishes past defection. This +assumes that the game is repeated time after time. In reality we never know if we meet our opponent again in the future. As long as neither our opponent nor we knows when the game ends, it pays to be nice. Of +course, the game of the Prisoner's Dilemma is only a two-player game. Reality often involves many-person interactions. + +There is one group that scientists say we treat better than others - our close genetic relatives. This is kin selection. We act altruistic to our kin because they share our genes. Studies show that in all +social species, relatives are more likely to help each other. The greater degree ofgenetic relatedness between two individuals, the more likely it is that an individual treats the other individual better. If +you sacrifice something for your children, it may harm you but since your children share your genes, the overall effect is positive. Scientists say that one test of kin selection is what we would do if a +relative and a good friend were both close to drowning. We can only save one of them. What if oneof them was adistant cousin that you'd seen only twice in your life and the friend was a person you spent every +day with? Who would you save? + +What other behavior was appropriate for our ancestors? + +A tendency for fear + +Our fears are always more numerous than our dangers. + +- Lucius Annaeus Seneca (Roman philosopher, c.4 BC-65 AD) + +The passengers boarded flight 651 to Chicago. Two hours after takeoff, the flight attendant heard suspicious noise ftom the lavatory. The passengers started to talk among themselves. Panic erupted. + +We fear dramatic and threatening events. We fear the loss of our health, family, friends, security, money, social status, power, or jobs. We also fear violence, crime, punishment, rejection, failure, the +unknown, the immediate, the unpredictable or the uncontrollable. Studies show that even witnessing a traumatic event can produce the same fear response as experiencing the event ourselves. + +Fear is our most basic emotion. Fear has evolved to help us anticipate danger and avoid pain. As science writer Rush Dozier writes in Fear Itself "Fear is fundamental because life is fundamental. If we die, +everything else becomes irrelevant." + +Humans have developed a strong emotion for fear. Our ancestors environment was fraught with dangers. Fear of physical danger, social disapproval, lack of food, + +24 + +no mate, predators, etc. Self-survival was a powerful incentive. Mistakes could be extremely costly. Assume two individuals heard a strange sound behind the bushes. One of them looked behind the bushes, was +bit by a poisonous snake and died. The other one saw what happened, ran away and survived. To always assume there was a threat behind the bushes and run away could save an individual's life. The cost of being +wrong and running when there was no snake was minimal. But the cost of staying around when there was a snake could be life threatening. Failure to detect threats is often more costly than false alarms. Our +ancestors learned through trial and error that in the long run, pain could be avoided if they were fearful. They survived the dangers because they learned how to respond. + +If pain and pleasure are guides to the behavior that leads to survival and + +reproduction, fear is our biological warning signal for avoiding pain. Fear warns us of potential harm and keeps us from acting in self-destructive ways. It helps us avoid threats and makes us act to prevent +further damage. Fear guides us to avoid what didn't work in the past. Fear causes worry and anxiety, a normal response to physical danger. It activates hormones like adrenaline and cortisol, which keeps us +attentive to harm since we need full attention to escape from a threat. + +The degree of fear we feel depends on our interpretation of the threat and our perception of control. The more helpless and vulnerable we feel, the stronger our emotion for fear becomes. + +Assume that you are walking alone late at night on a deserted street in New York City. Suddenly, you hear steps behind you. What happens? Immediately you fear the worst - robbery, assault, etc. Your autonomic +nervous system takes over and prepares you for fight or flight. Your response begins in your brain and activates a biochemical process. Your heart rate, breathing, blood pressure, pulse and blood sugar +increase. Normal behavior when you are the victim of stress, either perceived or real. You reacted with fear on the deserted street because evolution equipped your brain to register pain more sensitively than +any other emotion. You were using the "memory" of your ancestral past - your primitive fear system of fight or flight. + +What we fear and the strength of our reaction depend on our genes, life experiences, and the specific situation. You may react instinctively at first, but if the situation is one that you've experienced +before (since our brain is continuously being "rewired" with life experiences), the final reaction may be to calm down. You could turn around to find an old lady walking her dog. Or you may run away, because +you avoid situations that in the past have been painful. The more we are exposed to a stimulus, even a terrifying one, the higher our + +25 + +threshold of fear becomes. If you for example had walked the same deserted street many times before but found out each time that the noise was the old lady walking her dog, you would be less careful. Until +something terrifying happened. Often our emotions provide affective information that helps us make better decisions. For example, guilt may make us regret doing wrong things, and correct them. It may also +induce cooperation. Disgust seems to be a response to danger to protect us from disease or harm. Shame may help us avoid certain temptations or reduce the risk of group-conflict. People who can't experience +emotional responses because of brain damage seem unable to learn from their mistakes or + +to make choices in a coherent manner. + +Seeking explanations + +'1 ate a plant and now I feel sick. Therefore, I believe the plant was not good for me. " In chapter two of The Descent of Man, Charles Darwin wrote: ''As soon as the important faculties of the imagination, +wonder, and curiosity, together with some power of reasoning, had become partially developed, man would naturally have craved to understand what was passing around him." + +We don't like uncertainty or the unknown. We need to categorize, classify, organize, and structure the world. Categorizing ideas and objects helps us to recognize, differentiate and understand. It simplifies +life. To understand and control our environment helps us to deal with the future. We want to know how and why things happen and what is going to happen in the future. To understand how an event happened helps +us predict how it could happen again. This is why we always look for patterns and causal relationships among objects, actions, and situations. This makes it easier to identify and understand things and to +make predictions based on similarities in patterns. Finding and recognizing connections between things and events in our environment helps us to learn what does and does not work. Patterns also give us +comfort, making our need to find them even more important. + +To learn what works and does not and what is good or bad for us means we have to explore. Exploring our environment successfully enables our survival and reproduction. + +Remembering places, facts and events is important. But sometimes, the brain seems particularly attracted to new information and novel experiences. Recent studies suggest that the brain responds to novelty. +The unknown is potentially rewarding, thereby motivating us to explore our environment and learn for the future. + +We must be flexible in order to deal with constant change and unpredictability. We often explore the unknown in a random fashion. For example, many animals, + +26 + +when foraging, start with a random search, and only change their behavior when they find a rewarding stimulus. Then they move towards it. + +Being flexible and learning a variety of options to choose from to deal with the world is of great value. This implies that finding new ways to deal with the world is superior to overtraining old patterns. +For example, studies of honeybees show that they navigate according to a map-like organization of spatial memory. When bees are over-trained to find a single nectar site, it is easy for them to find their way +back to the hive from that site, but not very well from other sites. But when the same bees are trained to many nectar sites, they are much better in finding their way home to the hive from a range of +different locations. Further studies suggest that we learn better when we mix new information with what we already know. + +Making fast classifications + +There is a story about a man who went to visit a professor at his home. Outside the house a dog was playing on the lawn. When the professor opened the door to let the man in, the dog ran into the house. Later +the professor asked the man, "Do you always travel with your dog?" The man replied, "It's not my dog. I thought it was yours." + +Our brain is wired to perceive before it thinks - to use emotions before reason. fu a consequence of our tendency for fear, fast classifications come naturally. Limited time and knowledge in a dangerous and +scarce environment made hasty generalizations and stereotyping vital for survival. Waiting and weighing evidence could mean death. Don't we often draw fast conclusions, act on impulse and use our emotions to +form quick impressions and judgments? + +We are especially wary of things that move. They may imply danger. That is why we automatically assume agency - someone was responsible - when we detect motion. Better safe than sorry. + +Males and females have different priorities + +"What is the brain for?" asked Neuroscience Professor Michael Gazzaniga in [3mThe [0mMind's Past. "The smart-aleck answer to the question is sex. Put more completely, the brain exists to make better decisions about +how to enhance reproductive success." Reproduction is the central act in the life of every living thing. Once an individual has survived past the age of reproduction, the individual is evolutionarily useless. + +The struggle to reproduce can sometimes have peculiar effects. In nature, things are not always what they seem. + +27 + +An ant climbs to the top ofa grass stem, falls down and tries again and again... until a sheep comes along and eats the grass (and the ant}. WHY does the ant persist in climbing the grass? How does the ant +benefit? + +There is no benefit to the ant. Its behavior was manipulated by a parasitic flatworm that needed to get into the gut of the sheep in order to reproduce. By commandeering its intermediate ant host to climb to +the tips of the grass blades, the parasite increased the ant's chances of being eaten by a grazing animal. The benefit was to the reproductive success of the parasite, not the ant. Another parasite, +Toxoplasma, can only reproduce within cats. It causes rats to lose their inherited fear of cats (cat scent) and thereby makes the rat more likely to end up as cat dinner. Another parasite causes fish to swim +in shallow waters so birds can eat them, this parasite's final host. + +Most animals (including humans) do something to attract the opposite sex. Since natural selection is ultimately about reproduction in a world of limited mates, some individuals were better at getting mates +than others. The individuals that had an advantage in attracting prospective mates were "selected." What characteristics gave them the advantage? What anatomical features or behavioral traits attract the +opposite sex or intimidate rivals? + +Darwin realized that many anatomical and behavioral characteristics didn't have any survival value but could play an important role in attracting mates. Strength and beauty were such signals. He called this +mechanism sexual selection. It has for example been shown that colors spark sexual interest among butterflies. And peahens prefer peacocks with big, colorful tails. + +In Parental Investment and Sexual Selection, biologist Robert Trivers says that + +the force behind sexual selection is parental investment, or "any investment by the parent in an individual offspring that increases the offspring's chance of surviving (and hence reproductive success) at the +cost of the parent's ability to invest in other offspring." + +Men need to attract women. But they also need to keep other men away from "their" woman. A woman must invest in each of her children. There is a nine month pregnancy and thereafter many years of child-caring. +She invests time, energy and increases her chance of earlier death. There are limits to how many children she can produce during her lifetime. A man has less costs of reproduction. He can interact with many +women and produce an enormous amount of children. He doesn't need to be around all the time. Many women can raise their children without help. + +Since the goal of evolution is reproduction, a man should want to have sex with as many women as possible. This causes competition among men for women. + +28 + +How does a man eliminate this competition? He can either make himself more attractive to the woman or he can eliminate or reduce the competition. + +The reproductive success of women doesn't depend on how many men she has sex with, but on her ability to get access to resources (like food, shelter, and protection) for herself and her children. Women are +therefore more discriminating than men. She won't pick the first guy around. This causes women to compete with each other for access to resources. A man that is perceived as wealthy and having status has an +advantage. So mating choices (showing up as unconscious preferences) are influenced by the fact that women have more at stake than men do. + +In 1989, Psychology Professor David Buss published a study of thousands of men and women from 37 cultures around the world showing the ranking of qualities that are most important in choosing someone to date +or marry. Women placed more emphasis on a potential mate's financial prospects. Women also preferred ambitious and industrious men. Women preferred older men. Men preferred younger women. Men ranked physical +attractiveness higher than women did. The study also showed that a man felt most jealous when his woman was having sex with someone else. A woman felt most jealous when her man became emotionally attached to +someone else. + +Studies show other differences between the sexes. Women are less inclined to take risks. They are more influenced by the chance of loss. They are less competitive and status-conscious. Other studies show that +men and women differ in their behavioral and cognitive capabilities. Some of this reflects varying hormonal influences on brain development. Like most things, this is context dependent. + +The Social Animal + +We do not care about our reputation in towns where we are only passing through. But when we have to stay sorne tirne we do care. How rnuch tirne does it take?A tirne proportionate to our vain and paltry +existence. + +- Blaise Pascal (French mathematician and philosopher, 1623-1662) + +Isn't it likely that a good reputation, status, resources and being socially accepted helped our ancestors survive, get a mate, and reproduce? + +In a small hunter-gatherer society, what was good for the group often paid off for the individual. Cooperation was critical in an environment with limited resources, individual weaknesses and many dangers. +Isolation from a group or society could mean destruction. There was safety in numbers. The group protected the individual against predators, hunted together, exchanged + +29 + +information about where food was, cooperated to defend food from enemies, and was a key resource for mates and help with infants. Together the group stood a greater chance of survival. + +If we help another member of the small society, he may help us when we need it. If he doesn't, we may never help him again. This behavior is called reciprocation + +- the idea of "I scratch your back and you scratch mine." A reputation for being reliable and trustworthy is important because how we acted in the past is the only guide to how we act in the future. Ifwe fool +someone, he tells his friends, destroying our future possibilities for cooperation with others. Isn't that why we trust our friends but are careful when we meet strangers whom we know nothing about? + +We have a strong concern for fairness. We get upset when things are unfair. We sometimes even punish others at a cost to ourselves. Maybe we don't want to appear weak or easily taken advantage 0£ Since we +evolved in small communities with repeated interactions, it made sense to build up a reputation for not appearing weak. We wanted to encourage people to treat us better the next time around. + +What happens if we help someone but the next time we need help, this person conveniently disappears? What about people who don't return favors? True reciprocity only works if (1) we live in the same small +society so we recognize each other, can keep track of "services" given and received, and have future opportunities to interact, and (2) the cost of the act is pretty much the same as the future favor the +recipient receives. One-shot encounters encourage selfishness as told by Biology Professor Lee Alan Dugatkin: + +At a small dinner gathering... one of the dinner guests noted that when he looked for a mechanic, he always stayed away from garages on big highways and near "strips." Such mechanics, he said, knew that they +were never going to see you again and were notorious shysters. Go to a neighborhood garage, where word of mouth serves as advertising, and they know you will be a long-term customer. + +''Do good when others can see it. " + +Reputation matters. Do we behave differently when we are watched or when our identities are made public? It pays to be nice when others are watching. One lab study showed that people gave much more to charity +when they were "watched" by images of a robot. A real-world setting showed that people nearly trebled the amount of money they put in a psychology department coffee room box when they were watched by a pair +of eyes on a poster, compared with a poster with an image of flowers. Further studies have shown that we donate more when we get public recognition for our good deeds. American 20th Century writer Henry + +30 + +Louis Mencken said: "Conscience is the inner voice that tells us someone might be looking." + +Traits like fear of failure, losing social status or reputation were important because they affected an individual's standing in the ancestral hunter-gatherer society. Access to food and sex depended on it. +Survival and reproduction could be threatened. Social punishment was dangerous. It could lead to exile. According to Human Ecology Professor Garrett Hardin, it is the same today: + +Fear of disapproval is the major force that keeps a society intact: fear of God, fear of the police, and fear of the judgment of neighbors. Religious authorities want the fear of God + +to be the predominant controller. Civil authorities want fear of police and court to + +dominate. But, says Locke [John], the opinion of one's neighbors trumps all others. + +Providing resources is another behavior that increases chances of survival and getting a mate.The better our ability to provide, the higher our status would be in the community. + +As we saw earlier there is competition among men for women. Women compete with each other for access to resources.Women wanted males who could take care of the children. Resources like food, lodging, and +status attracted them. Striving for authority, dominance, esteem, position, and respect were advertisements for wealth. Charles Darwin said: "Man admires and often tries to exaggerate whatever characteristics +nature may have given him." + +What other evidence is there that humans are social animals? One study of a group of men whose wives suffered fatal cases of breast cancer showed that the widowers had lower immune system activity. Another +study showed that men who were socially isolated were more likely to die than more socially integrated people were. It has also been shown that social rejection feels similar to physical pain. Rejection +hurts! + +Pecking order also matters. As we strive for status, hierarchies emerge. + +Norwegian zoologist Thorleif Schjelderup-Ebbe discovered that in the world of hens there is a linear hierarchy where every hen knows its place. Science writer Robert Wright says in The Moral Animal: "Throw a +bunch of hens together, and, after a time of turmoil, including much combat, things will settle down. Disputes...will now be brief and decisive, as one hen simply pecks the other, bringing quick deferral." + +The pecking order determines who gets the first chance to eat, and which hen can peck the other hens.Each hen knows who it can dominate, and in turn, who will dominate it. + +31 + +Status hierarchies aren't only valid for hens. Studies show that when we put a group of children together, they will shortly fall into separate grades. The ones at the top are best liked, most often imitated, +and most obeyed. It is painful to lose status once it has been obtained. + +Studies show that where we stand on the social ladder influences our health, well-being and length of life. The higher our status in the pecking order, the healthier we are likely to be. + +We must be careful not to carry these evolutionary explanations about adaptive behavior too far. There are many causes for behavior. We can't extrapolate the conditions of the ancestral environment to explain +every behavior. No one knows what the ancestral environment was like. Unlike bone and tissue, there is no fossil evidence of behavior. Neither is there any neurological or genetic evidence for or against +certain behavior. And evolutionary explanations about the brain can't be experimentally tested. A trait that is found everywhere isn't necessarily genetically specified. But much of the behavior described is +consistent with evidence we have from other organisms and documented human history. + +Let's go back one million years and assume you were living in a small community with 150 people where everybody knew each other, and where the mating opportunities were limited. The environment was fraught +with danger and challenges. The key was to avoid danger, get food and attract a partner. What behavior was critical to survival and reproduction? + +Isn't it rewarding to make fast judgments?- "If noise behind the bush, then run." It is a natural tendency to act on impulse - to use emotions before reason. The behavior that was critical for survival and +reproduction in our evolutionary history still applies today. Wouldn't being fearful help you survive? Social failure be costly? Maintaining status, resources and social approval help you survive and get a +mate? Wouldn't you present yourself as honest, nice and trustworthy so others will cooperate with you? Wouldn't a common threat or a common goal make people cooperate? Wouldn't following social norms make +sense? Wouldn't you have a strong aversion to losses and only take big risks when you were threatened? Wouldn't you be concerned with the short-term interest of yourself and loved ones? + +Much of our psychology is the result of cultural influences + +Human society is not only shaped by the evolution of genes, but also by cultural evolution. Practices, methods, tools, myths, ethics, and social norms that are important in the evolution of our behavior. +Customs that we learn from the experience of our parents and others - either by teaching or observation. + +32 + +Cultural evolution is faster than genetic evolution since it allows much of what we learn to be passed on and combined with what others around us have learned. Unlike biological evolution, cultural evolution +is not inherited. We don't inherit our parents' habits. We learn from them. + +In a sense, genetic and cultural evolution interact. Biology influences our culture. Take language as an example. We come equipped with an anatomy, physiology and biochemistry that give us the ability to +learn a language. But we are not born with a language. The language we speak is a product of our culture. Our culture also influences our biology by creating the environment in which natural selection is +tested. If a certain behavior proves to be beneficial generation over generation, that behavior is favored by natural selection. Assume individuals over time make certain social behavior choices. These +choices were transmitted through learning and culture. Over time, they will be favored by natural selection + +since they positively influence survival and reproduction. + +Our basic nature + +Men's natures are alike; it is their habits that carry them far apart. + +- Confucius + +What is our basic nature? + +Our nature is a product of our biological and cultural history. Evolution explains how we are shaped and biologically constrained. Like our bones, kidney, eyes, and legs, our brain has been shaped by natural +selection. Natural selection equipped us with traits that increase our chances for survival and reproduction. It then follows that we consciously or unconsciously behave according to what we perceive is in +our own best interest. This is our biological base nature. It is strengthened or weakened depending on our life experiences. If we assume that people on average act out of self-interest we'll be less +disappointed than if we assume that people on average act out of altruism. This does not mean that we can't make things better. But doing so demands that we first understand why we are the way we are. Richard +Dawkins said in The Selfish Gene: "Be warned that if you wish, as I do, to build a society in which individuals cooperate generously and unselfishly towards a common good, you can expect little help from +biological nature. Let us try to teach generosity and altruism, because we are born selfish." + +Let's summarize the forces that influence and set the limits for our judgments. Genes- environmental stimuli cause response tendencies from our genes. Our genes have evolved and their functions are primarily +based on what was beneficial in the hunter-gatherer environment - the environment where humans spent + +33 + +most of their time. To survive, we must avoid all perceived threats to our survival and reproduction. Evolution has developed a value system based on pain and pleasure that help us deal with the environment. +Since the ancestral environment consisted oflimited resources and danger, we developed a strong aversion for loss and a tendency for fear. We made fast evaluations and became social animals. We were +predisposed to evaluate situations by being fearful. To not respond with fear could be more costly than responding with fear and being wrong. We also acted in ways where the reward was important and the cost +was minimal. + +Life experiences - upbringing, nutrition, education, social stamping, physical, + +social and cultural settings create certain convictions, habits, values, attitudes and character traits. This in turn creates our individual beliefs and assumptions. Our judgments are influenced by our state +of mind. + +Present environment - outside factors like the environment, the context or circumstances, or the specific situation. + +Randomness - we are prepared to be open minded to new experiences since environments vary; handling new challenges is a means of adaptation. + +The consequences of our actions reinforce certain behavior. If the consequences were rewarding, our behavior is likely to be repeated. What we consider rewarding is individual specific. Rewards can be +anything from health, money, job, reputation, family, status, or power. In all of these activities, we do what works. This is how we adapt. The environment selects our future behavior. But it's not just what +happens to us that counts. It's what we think happens. + +When we face a situation, our brains create an expectation. We can act in ways contrary to our self-interest if we don't understand the consequences. + +Our behavior creates feedback from our environment. If we do dumb things and suffer the consequences, we may still do dumb things in the future even if it causes pain. Either because we don't understand the +cause of our mistake, or the pain is less painful than other behavior. + +Our experiences are stored in the brain and influence us in the future. New connecting patterns between neurons are created. + +Some decisions are not in our best interest + +There must certainly be a vast fond of stupidity in human nature, else men would not be caught as they are, a thousand times over, by the same snare, and while they yet remember their past misfortunes, go on +to court and encourage the + +causes to which they are owing, and which will again produce them. + +- Marcus Porcius Cato (Roman statesman and writer, 234-149 BC) + +34 + +If we often act out of self-interest, why do we make decisions that are clearly not in our best interests? + +There is a disconnect between the ancestral world to which our brains adapted and today's world. Many of our traits are better adapted for the demands of the ancestral world such as: keeping away from +predators, risking social exclusion, finding mates, getting enough food, maintaining relationships, acquiring status and a safe place to live, and bearing children. + +Genetic and cultural evolution equipped us with behavioral tendencies (like the tendency for fear, reciprocal cooperation, fast classifications, concern for social approval, etc.) that help us interact with +our environment. These tendencies are on average more helpful than not (otherwise we wouldn't be here today). Sometimes they lead us astray and cause us to make misjudgments. + +For example, we may be biased by our automatic tendency to trust the people we like. Liking is often based on first impressions. We are superbly equipped to read other people for signs of trustworthiness. We +look at their emotional state - their voice and general expression. However, it is often difficult to spot the difference between a good and bad actor. An individual may be secretive and hostile, or warm and +open. What consequences would these different behaviors have on our perception of that individual? We forget to think about other factors that are important in evaluating a person or a situation. Appearances +may be deceiving. The best con artists always behave as though they are not acting in their best interest. The 16th Century Italian political philosopher Niccolo Machiavelli said in The Prince: "Princes who +have achieved great things have been those who have given their word lightly, who have known how to trick men with their cunning, and who, in the end, have overcome those abiding by honest principles." + +In Part One we have learned about our nature and our limitations. With this background let us now look at how our psychological abilities affect our decision making. + +Warren Buffett gives us some introductory remarks on why even smart people get bad results: + +It's ego. It's greed. It's envy. It's fear. It's mindless imitation of other people. I mean, there are a variety of factors that cause that horsepower of the mind to get diminished dramatically before the +output turns out. And I would say if Charlie and I have any advantage it's not because we're so smart, it is because we're rational and we very seldom let extraneous factors interfere with our thoughts. We +don't let other people's opinion + +35 + +interfere with it... we try to get fearful when others are greedy. We try to get greedy when others are fearful. We try to avoid any kind of imitation of other people's behavior. And those are the factors +that cause smart people to get bad results. + +I always look at IQ and talent as representing the horsepower of the motor, but then in terms of the output, the efficiency with which the motor works, depends on rationality. That's because a lot of people +start out with 400-horsepower motors and get a hundred horsepower of output. It's way better to have a 200-horsepower motor and get it all into output. So why do smart people do things that interfere with +getting the output they're entitled to? It gets into the habits, and character and temperament, and it really gets into behaving in a rational manner. Not getting in your own way. + +In Part Two, Three, and Four we use two fictional characters named John and Mary. At 40, John is a senior executive ofTransCorp; a US company engaged in widely varied businesses. John is married to Mary, a +part-time schoolteacher. + +36 + +- PART Two - + +[1mTHE PSYCHOLOGY OF MISJUDGMENTS [0m + +Why oh why are human beings so hard to teach, but so easy to deceive. + +- Dio Chrysostom + +(Greek philosopher and orator, 2nd Century) + +37 + +- ONE - + +MISJUDGMENTS EXPLAINED BY PSYCHOLOGY + +I came to the psychology of human misjudgment almost against my will; I rejected it until I realized that my attitude was costing + +me a lot of money, and reduced my ability to help everything I loved. + +- Charles Munger + +Part One gave us a background of our behavior, psychology and limitations. We learned how pain and pleasure guide our behavior, how we tend to take the most rewarding view of events, how we make quick +judgments, and are social animals. We also saw how we have developed a strong aversion to loss and uncertainty, and how it is natural for people to behave in ways they perceive is in their best interests. +Charles Munger says, "If you want to avoid irrationality, it helps to understand the quirks in your own mental wiring and then you can take appropriate precautions." This part explores 28 reasons for +misjudgments that can be explained by our psychological make-up. Many of the reasons are rooted in psychological tendencies and biases that often influence us subconsciously. The more emotional, confused, +uncertain, insecure, excited, distracted, tired or + +stressed we are, the easier we make mistakes. Geniuses aren't excluded. + +Below is a list of 28 reasons for misjudgments and mistakes. It can be used as a checklist to explain or predict behavior or as a pilot's checklist to avoid fooling ourselves. Each item on the list will be +explained in the next chapter. + +Bias from mere association - automatically connecting a stimulus with pain or pleasure; including liking or disliking something associated with something bad or good. Includes seeing situations as identical +because they seem similar. Also bias from Persian Messenger Syndrome - not wanting to be the carrier of bad news. + +Underestimating the power of rewards and punishment - people repeat actions that result in rewards and avoid actions that they are punished for. + +Underestimating bias from own self-interest and incentives. + +Self-serving bias - overly positive view of our abilities and future. Includes over-optimism. + +39 + +Self-deception and denial - distortion of reality to reduce pain or increase pleasure. Includes wishful thinking. + +Bias from consistency tendency - being consistent with our prior commitments and ideas even when acting against our best interest or in the face of disconfirming evidence. Includes confirmation bias - looking +for evidence that confirms our actions and beliefs and ignoring or distorting disconfirming evidence. + +Bias from deprival syndrome - strongly reacting (including desiring and valuing more) when something we like and have (or almost have) is (or threatens to be) taken away or "lost." Includes desiring and +valuing more what we can't have or what is (or threatens to be) less available. + +Status quo bias and do-nothing syndrome -keeping things the way they are. Includes minimizing effort and a preference for default options. + +Impatience -valuing the present more highly than the future. + +Bias from envy and jealousy. + +Distortion by contrast comparison - judging and perceiving the absolute magnitude of something not by itself but based only on its difference to something else presented closely in time or space or to some +earlier adaptation level. Also underestimating the consequences over time of gradual changes. + +Bias from anchoring - over-weighing certain initial information as a reference point for future decisions. + +Over-influence by vivid or the most recent information. + +Omission and abstract blindness - only seeing stimuli we encounter or that grabs our attention, and neglecting important missing information or the abstract. Includes inattentional blindness. + +Bias from reciprocation tendency- repaying in kind what others have done for or to us like favors, concessions, information and attitudes. + +Bias from over-influence by liking tendency - believing, trusting and agreeing with people we know and like. Includes bias from over-desire for liking and social acceptance and for avoiding social +disapproval. Also bias from disliking - our tendency to avoid and disagree with people we don't like. + +Bias from over-influence by social proof - imitating the behavior of many others or similar others. Includes crowd folly. + +Bias from over-influence by authority - trusting and obeying a perceived authority or expert. + +Sensemaking - Constructing explanations that fit an outcome. Includes + +40 + +being too quick in drawing conclusions. Also thinking events that have happened were more predictable than they were. + +Reason-respecting - complying with requests merely because we've been given a reason. Includes underestimating the power in giving people reasons. + +Believing first and doubting later - believing what is not true, especially when distracted. + +Memory limitations - remembering selectively and wrong. Includes influence by suggestions. + +Do-something syndrome - acting without a sensible reason. + +Mental confusion from say-something syndrome - feeling a need to say something when we have nothing to say. + +Emotional arousal- making hasty judgments under the influence of intense emotions. Includes exaggerating the emotional impact of future events. + +Mental confusion from stress. + +Mental confusion from physical or psychological pain, the influence of chemicals or diseases. + +Bias from over-influence by the combined effect of many psychological tendencies operating together. + +These psychological tendencies (that also interact) have been verified by a number of experiments. Some people are more vulnerable to them than others. But we can't study them independent of an individual's +values and the situation. Behavior that seems irrational may be fully rational from the individual's point of view. There is always some background within which behavior makes sense. Behavior can't be seen as +rational or irrational independent of context. We are created with a series of emotions that are appropriate depending on + +circumstances. If we change context or environment, we change behavior. + +The next chapter describes the 28 psychological reasons why we make misjudgments and mistakes. Observe that these biases and tendencies are often not independent of one another. There is some overlap. Observe +also that there are many reasons for a given behavior. Many of the real-world illustrations can be explained by more than one tendency and also by non-psychological factors. Misjudgments are often caused by +many factors working together. + +Most of the explanations are based on work done by Charles Munger, Psychology Professor Robert Cialdini, Behavioral Science and Economics Professor Richard Thaler, Psychology Professor Robyn Dawes, Psychology +Professor Daniel Gilbert, and Psychology Professors Daniel Kahneman and the late Amos Tversky. + +41 + +- Two - + +PSYCHOLOGICAL REASONS FOR MISTAKES + +Man is, and always was, a block-head and dullard, much readier to feel and digest than to think and consider. + +-Thomas Carlyle (Scottish historian, 1795-1881) + +MERE Assoc1ATION + +Inside the jewelry boutique, surrounded by enchanting music and gorgeous women, how could John resist not buying Mary the $5,000 necklace? + +We automatically feel pleasure or pain when we connect a stimulus - a thing, situation or individual - with an experience we've had in the past or with values or preferences we are born with. As we've +learned, we move towards stimuli we associate with pleasure and away from those we associate with pain. We most easily associate to the events whose consequences we have experienced most often and the ones we +easily remember. The more vivid or dramatic an event is, the easier we remember it. + +Every time Mary served bacon for breakfast, she sung a special melody. After awhile, + +if john heard her singing the melody, he expected bacon. + +The Russian scientist Ivan Pavlov studied the digestive system of dogs when he observed that a stimulus unrelated to food made the dogs salivate. In one experiment he rang a bell just before giving food to +the dog. He repeated this several times until the dog salivated at the sound of the bell alone. No sight or smell of food was present. The sound of the bell produced the same response as the food. The dog +learned to associate the bell with food. + +Experiments have shown that we can learn to fear a harmless stimulus if it is paired with an unpleasant one. If for example rats consistently receive mild electrical shock after hearing a tone, the rats learn +to develop a fear of the tone alone. Association can influence the immune system. One experiment studied food aversion in mice. Mice got saccharin-flavored water (saccharin has incentive value due to its +sweet taste) along with a nausea-producing drug. Would the mice show signs of nausea the next time they got saccharin water alone? Yes, but the mice also + +42 + +developed infections. It was known that the drug in addition to producing nausea, weakened the immune system, but why would saccharin alone have this effect? The mere pairing of the saccharin with the drug +caused the mouse immune system to learn the association. Therefore, every time the mouse encountered the saccharin, its immune system weakened making the mouse vulnerable to infections. + +john's supplier took him to the best steakhouse in town andpicked up the check. The next time it was time to buy new supplies, john associated the supplier with pleasant feelings. People can influence us by +associating a product, service, person, investment, or a situation with something we like. Many times we buy products, enter relationships, and invest our money merely because we associate them with positive +things. No wonder advertisers or politicians connect what they want to sell with things we like and avoid associating themselves with negative events. Pair a sports car with something that produces a positive +feeling- a beautiful and sexy model - and we automatically associate the car with pleasure. + +john was afraid to deliver bad news to the CEO. + +Whether we like someone is influenced by the events with which an individual is associated. Bad news isn't welcome. We tend to dislike people who tell us what we don't want to hear even when they didn't cause +the bad news i.e., kill the messenger. This gives people an incentive to avoid giving bad news. To protect themselves, they tell the news in a way they believe we want to hear it. This tendency is called the +Persian Messenger Syndrome and traces its origins back to ancient Greece. In Antigone, a messenger feared for his life since he knew the king would be unhappy with the news he brought. + +Warren Buffett says on being informed of bad news: "We only give a couple of instructions to people when they go to work for us: One is to think like an owner. And the second is to tell us bad news +immediately - because good news takes care of itself. We can take bad news, but we don't like it late." + +Seeing the fish salad, john remembered the time when he'd eaten fish salad andgotten sick, and once more felt nauseous. + +We see similar situations where they don't exist because a situation resembles an earlier experience. We therefore believe that the future mirrors the past and that history will repeat itself. + +Keep in mind + +Evaluate things, situations and people on their own merits. + +43 + +Individuals are neither good nor bad merely because we associate them with something positive or negative. + +Encourage people to tell you bad news immediately. + +Merely because you associate some stimulus with earlier pain or pleasure doesn't mean the stimulus will cause the same pain or pleasure today. Past experiences are often context dependent. + +Create a negative emotion if you want to end a certain behavior. If you want + +someone to stop smoking, one way could be to show them what they stand to lose. Terrifying pictures may cause them to associate smoking with death. + +REWARD AND PUNISHMENT + +The iron rule of nature is: you get what you reward for. + +Ifyou want ants to come, you put sugar on the floor. + +Charles Munger + +[3mjohn's actions brought him praise and money, making him continue his behavior. [0mWe do what is rewarding and avoid what we are punished for. We learn - right and wrong- from the consequences of our actions. +Whatever causes us to repeat a certain behavior is reinforcing and whatever makes us stop is punishing. Behavior that is rewarding or feels pleasurable tends to be repeated. We don't continue doing what we're +being punished for. Give people what they desire (or take away something undesirable) and their behavior will repeat. Give them something undesirable (or take away what they desire) and their behavior will +stop. In the beginning, rewarding (or punishing) people is most effective when it is administered without delay and each time the behavior is repeated. + +Once a behavior becomes learned, variable rewards strengthen the behavior. Behavior that is rewarded on an unpredictable basis has the highest rate of response and is the most difficult to extinguish. This +is, for example, how gamblers are rewarded. When they don't know when the reward will arrive, they try again and again. Furthermore, the greater the reward, the more resistant the behavior is to extinction. + +We base what is rewarding or punishing on our associations to past experiences and their consequences or with values or preferences we are born with. + +An action that is reinforced becomes stronger over time. This is how habits, superstitions and addictions are created. Both are hard to change. As the great 18th Century English writer Samuel Johnson said: +"The chains of habit are too weak to be felt until they are too strong to be broken." + +What does all this mean? It means that people do what works. Like bees to + +44 + +honey, they go where there is a reward. This also implies that if we reward what we don't want, we get it. As Garrett Hardin says in The Ostrich Factor: "If the laws of society reward for bank robbing, +society will get more bank robbing. If our methods of winnowing candidates for high positions favor stupidity, we will get stupid politicians." + +Studies in Sweden show that changes in the sickness insurance system affect sick leave behavior. Reforms implying more generous compensation for sick leave tenq to be associated with permanent increases in +total sick leave per person employed. Other studies from the U.S. regarding health services have shown that in cases where someone else picks up the costs, patients tend to over-consume the health services. + +Why do people abuse the health care and welfare system? Isn't it natural that people use the system if they don't have to pay anything? And if people don't have to pay for a benefit, they often overuse it. +The more people that benefit from misusing the system, the less likely it is that anyone will draw attention to what really happens. Individually they get a large benefit and it's a small loss for society. +Until everyone starts thinking the same. The ancient Greek philosopher Aristotle said: "That which is common to the greatest number gets the least amount of care. Men pay most attention to what is their own; +they care less for what is common." + +Why do people steal? + +Studies show that 23% of people say they would steal if they couldn't get caught. It is estimated that U.S. businesses lose $400 billion a year from fraud and about a third of that is from employees stealing +from their employer. Why? Opportunity and reward. In Charles Munger's words: ''The worst abuses come where people have the greatest temptations." If we make it easy for people to steal, they steal (and bad +behavior will spread). + +Charles Munger tells us how a bad policy can become the norm: + +In the New York Police Department, they have a simple system. Your pension is based on your pay in your final year. So when anyone reaches the final year, everybody cooperates to give him about 1,000 hours of +overtime. And he retires - in some cases after a mere 20 years of service - with this large income. Well, of course his fellow employees help him cheat the system. In substance, that's what's happened. But +the one thing I guarantee you is that nobody has the least sense of [3mshame. [0mThey soon get the feeling they're [3mentitled [0mto do it. Everybody did it before, everybody's doing it now - so they just keep doing it. + +45 + +Why does a tennis player always wear his lucky shirt in the finals? + +In one experiment, American psychologist B.F. Skinner fed pigeons small quantities of food at regular intervals. After some time the pigeons began to behave superstitiously. If a pigeon was bobbing its head +when food appeared, it got the idea that bobbing its head must have made the food appear. The pigeons continued with the behavior that worked - every time they performed the behavior, food appeared. But food +appeared independent of what the pigeons did. Skinner wrote in "Superstition" in the pigeon: "There are many analogies in human behavior... A few accidental connections between a ritual and favorable +consequences suffice to set up and maintain the behavior in spite of many nonreinforced instances." + +Are the right incentives important? + +Incentives act as reinforcers. Charles Munger tells a story about the importance of getting the incentives right: + +From all business, my favorite case on incentives is Federal Express. The heart and soul of their system -which creates the integrity of the product- is having all their airplanes come to one place in the +middle of the night and shift all the packages from plane to plane. If there are delays, the whole operation can't deliver a product full of integrity to Federal Express customers. And it was always screwed +up. They could never get it done on time. + +They tried everything- moral suasion, threats, you name it. And nothing worked. Finally, somebody got the idea to pay all these people not so much an [3mhour, [0mbut so much a [3mshift [0mand when it's all done, they can +all go home. Well, their problems cleared up overnight. + +john invested in a biotech start-up that went sour and he lost money. + +After a success, we become overly optimistic risk-takers. After a failure, we become overly pessimistic and risk-averse - even in cases where success or failure was merely a result of chance. Good +consequences don't necessarily mean we made a good decision, and bad consequences don't necessarily mean we made a bad decision. + +The next time someone presents John an investment opportunity in a biotech start-up the chances are he will decline. He associates the new proposal to his earlier experience. And since people tend to believe +that the future mirrors the past, he declines. But what happens if John's first investment made him a lot of money? Wouldn't John associate the new proposal to his old pleasurable experience? Isn't he +therefore more likely to invest? This automatic association to what worked in the past causes people to under-react to new conditions and circumstances. + +46 + +Mark Twain understood the dangers of blindly trusting past experience for dealing with the future. "We should be careful to get out of an experience only the wisdom in it, and stop there, lest we be like the +cat that sits down on a hot stove-lid. She will not sit down on a hot stove-lid again - but also she will never sit down on a cold one anymore." + +Does it matter in which size or order rewards or punishments arrive? + +Mary never wraps the kids Christmas presents in one box. + +Since our experiences seem longer when broken into segments, we like to have pleasurable experiences broken into segments but painful ones combined. That is why Mary puts presents in many boxes. Frequent +rewards feel better. For example, it feels better to gain $50 twice than $100 once since every gain is rewarding. It feels better to lose $100 once than $50 twice since every loss is painful. + +We prefer a sequence of experiences that improve over time. Losing $100 first and then gaining $50 seems more rewarding than gaining $50 and then losing + +$100. We want to get rid of the bad experiences first. Immediate losses are preferred over delayed ones. Just as we don't like bad experiences, we also don't like waiting for them. We like to get over them +fast. + +Mere association and reinforcement are both examples of conditioned reflexes. Charles Munger gives an example how these forces can be used as he describes the invention of non-alcoholic drinks: + +The food value and so forth of the beverage is the reinforcer. And the trade dress, trade name and look of the beverage is the stimulant... + +Then, you go on to the second kind of conditioned reflex- and that's straight Pavlov... Well, how do you get Pavlovian mere-association effects? Obviously, you associate this beverage and its trademarks with +every good thing that people like generally: exalting events, sex objects, happy times - you name it. + +How can we lose a conditioned reflex that's working for us? Charles Munger continues: + +Well, the customer tries something else and discovers that it's a big reinforcer. So he shifts brands. We know, in matrimony, that if you're always available, the spouse is less likely to shift brands. And +people don't tend to organize marriage to include permanent long separations. Similarly, if you're selling a product and it's always available, people are less likely to shift to some other product and get +reinforced by it. + +47 + +Keep in mind + +American statesman, scientist and philosopher Benjamin Franklin tells us that: ''A spoonful of honey will catch more flies than a gallon of vinegar." Praise is more effective in changing behavior than +punishment. It is better to encourage what is right than to criticize what is wrong. + +Set examples. Michel de Montaigne said: "It is a custom of our justice to punish some as a warning to others. For to punish them for having done wrong would, as Plato says, be stupid: what is done cannot be +undone. The intention is to stop them from repeating the same mistake or to make others avoid their error. We do not improve the man we hang: we improve others by him." + +Don't over-learn from your own or others bad or good experience. The same action under other conditions may cause different consequences. + +Separate between skill and chance. Charles Munger says, "As you occupy some high-profit niche in a competitive order, you must know how much of your present prosperity is caused by talents and momentum +assuring success in new activities, and how much merely reflects the good fortune of being in your present niche." + +American novelist Upton Sinclair said: "It is difficult to get a man to understand something when his salary depends upon him not understanding it." Since people do what works, be sure to make the incentives +right. Tie incentives to performance and to the factors that determine the result you want to achieve. Make people share both the upside and downside. And make them understand the link between their +performance, their reward and what you finally want to accomplish. For example, tie a manager's compensation to gain in business value (of the unit under his control) minus a cost factor for capital that is +used to produce this value. The auto insurer GEICO's plan exemplifies Berkshire Hathaways's incentive compensation principles. Warren Buffett says: + +Goals should be (1) tailored to the economics of the specific operating business; (2) simple in character so that the degree to which they are being realized can be easily measured; and + +(3) directly related to the daily activities of plan participants. As a corollary, we shun "lottery ticket" arrangements, such as options on Berkshire shares, whose ultimate value + +which could range from zero to huge - is totally out of the control of the person whose behavior we would like to affect. In our view, a system that produces quixotic payoffs will not only be wasteful for +owners but may actually discourage the focused behavior we value m managers. + +48 + +Reward individual performance and not effort or length in organization and reward people after and not before their performance. + +Don't let money be the only motivation. If we reward people for doing what they + +like to do anyway, we sometimes turn what they enjoy doing into work. The reward changes their perception. Instead of doing something because they enjoy doing it, they now do it because they are being paid. +The key is what a reward implies. A reward for our achievements makes us feel that we are good at something thereby increasing our motivation. But a reward that feels controlling and makes us feel that we are +only doing it because we're paid to do it, decreases the appeal. Blaise Pascal said: "We are generally the better persuaded by the reasons we discover ourselves than by those given to us by others." + +Install systems and rules that encourage the behavior you want. Never let it pay someone to behave in a way you don't want. Have systems that make it hard for people to get away with undesirable behavior. +Make undesirable behavior costly. The painful consequences of undesirable behavior must outweigh its pleasurable consequences. For example, the consequences of spending time in jail ought to be more painful +than the pleasure of getting away with burglary. + +Systems can be hard to change as Warren Buffett observes, "It's very hard to change a system when the guy whose hand is on the switch benefits enormously and, perhaps, disproportionately from that system." + +Decision-makers should be held accountable for the consequences of their actions. In The Case for Modern Man, American philosopher Charles Frankel defines responsibility: ''A decision is responsible when the +man or group that makes it has to answer for it to those who are directly or indirectly affected by it." Charles Munger adds, ''An example of a really responsible system is the system the Romans used when +they built an arch. The guy who created the arch stood under it as the scaffolding was removed. It's like packing your own parachute." + +SELF-INTEREST AND INCENTIVES + +"Damn it all, we want to get at the truth" [said Lord Peter Wimsey}"Do you" said Sir Impey dryly. "I don't. I don't care two pence about the truth. I want a case." + +Dorothy Sayers (British writer, 1893-1957) + +The organizers of a tennis tournament needed money. They approached the CEO of TransCorp and asked him to sponsor the tournament. + +49 + +"How much?" asked the CEO. "One million,"said the organizer. + +"That is too much money," said the CEO. + +''Not if you consider the fact that you personally can p/,ay one match, sit at the honorary stand next to a member of the presidential family and be the one that hands over the prize,"said the organizer. + +"Where do I sign?" said the CEO. + +People do what they perceive is in their best interest and are biased by incentives. For example, when the first Dead Sea scrolls were discovered and the archeologists wanted more fragments of the scrolls to +be found, they offered a reward per fragment. The result: the fragments were split into smaller pieces before they were turned in. + +The comedian Groucho Marx once interviewed a U.S. Senator about a miracle cure-all vitamin and mineral tonic that the Senator had invented. When Groucho asked him what it was good for, the Senator answered: +"It was good for five and a half million for me last year." + +Incentives for the decision-maker determine behavior. This means that we have to recognize self-interested behavior in others. + +Are advisors always to be trusted? + +There is an old saying: "Never ask the village barber if you need a haircut." We are biased by our incentives as are others including lawyers, accountants, doctors, consultants, salesmen, organizations, the +media, etc. What is good for them may not be good for us. Advisors are paid salesmen and may trick us into buying what we don't need. + +For an attorney, litigation is often more lucrative than settlement. Lawyer William F. Coyne, Jr. says in The Case for Settlement Counsel there are "significant incentives for lawyers not to embrace early +settlement ... These incentives include the need to market services, the desire not to appear weak, the obligation to represent a client zealously, the thirst for justice, but perhaps not least, the desire to +maximize income." + +Warren Buffett tells us that one of Berkshire's compensation arrangements was worked out: "without the "help" of lawyers or compensation consultants. This arrangement embodies a few very simple ideas - not +the kind of terms favored by consultants who cannot easily send a large bill unless they have established that you have a large problem (and one, of course, that requires an annual review)." + +Charles Munger tells us about the common tendency of salesmen: + +50 + +All commissioned salesmen have a tendency to serve the transaction instead of the truth. + +...I put consultants in the same category, sometimes even lawyers - sometimes especially lawyers. + +Many years ago, a Pasadena friend of mine made fishing tackle. I looked at this fishing tackle - it was green and purple and blue - I don't think I'd ever seen anything like them. I asked him "God! Do fish +bite these lures?" He said to me, "Charlie, I don't sell to fish." + +Let's look at the brokerage and investment banking business. Brokers have a strong incentive to get us to trade. They advise us what to buy and sell. Volume creates commissions. Investment bankers encourage +overpriced acquisitions to generate fees. Investment bankers have every incentive to get initial public offerings (IPO) deals done, regardless of the company's quality. Their compensation is tied to the +revenues the deal brings in. Analysts are rewarded for helping sell the IPO. Brokers want to move the stock. What did Groucho Marx say? "I made a killing on Wall Street a few years ago.. .I shot my broker." + +Similarly, in the medical field, some psychologists ensure themselves successive + +paydays by telling their patients that another visit is required. And they don't talk about the limits of their knowledge. Their careers are at stake. As American actor Walther Matthau said, "My doctor gave +me six months to live. When I told him I couldn't pay the bill, he gave me six more months." + +Why do bankers approve risky loans? + +People who are rewarded for doing stupid things continue to do them. From their frame of reference, they acted logically based on how they were rewarded. The incentive system paid them to do the wrong thing. +So if market share rather than profits pay a banker, he will write as many loans as possible. He is being rewarded every year while the net consequences of the bad loans won't be realized for a long time. + +Charles Munger gives an example of how Lloyd's Insurance rewarded their people: + +They were paid a percentage of the gross volume that went through. And paying everybody a percentage of the gross, when what you're really interested in is the net, is a system - given the natural bias of +human beings toward doing what's in their own interest even though it has terrible consequences for other people - that really did Lloyd's in. + +Be carefal what you pay for, you may get it. + +The city of New Orleans introduced a program under which districts that + +51 + +showed improvement in cnme statistics received awards that could lead to bonuses and promotions, while districts that didn't faced cutbacks and firings. What happened? In one police district, nearly half of +all serious crimes were reclassified as minor offences and never fully investigated. + +Studies show that teachers help students cheat on standardized tests when their jobs or pay increases depend on the outcome of the tests. + +john knew that if he didn't show good figures, his project wouldn't be fonded so he cooked the books. + +Why do people give a biased picture of reality? Why do they make figures look better than they are or fake data to support something? Behavior that is not acceptable but results from the tendency of people +doing what they perceive is in their best interest. + +There may be powerful economic and prestige-related incentives to underestimate costs and overestimate benefits when people try to sell projects. For example, studies based on data from several hundred large +transportation infrastructure projects in twenty nations and five continents found evidence that in a number of cases, project promoters and forecasters of billion-dollar projects intentionally misrepresented +the costs, benefits and risks of projects in order to get them approved. + +Charles Munger says that projections should be handled with care: + +Mark Twain used to say, "A mine is a hole in the ground with a liar on the top." And a projection prepared by anybody who stands to earn a commission or an executive trying to justify a particular course of +action will frequently be a lie - although it's not a deliberate lie in most cases. The man has come to believe it himself. And that's the worst kind. Projections should be handled with great care - +particularly when they're being provided by someone who has an interest in misleading you." + +Warren Buffett adds: + +I have no use whatsoever for projections or forecasts. They create an illusion of apparent precision. The more meticulous they are, the more concerned you should be. We never look at projections, but we care +very much about, and look very deeply at, track records. If a company has a lousy track record, but a very bright future, we will miss the opportuniry... I do not understand why any buyer of a business looks +at a bunch of projections put together by a seller or his agent. You can almost say that it's naive to think that those + +projections have any utiliry whatsoever. We're just not interested. + +52 + +If we don't have some idea ourselves of what the future is, to sit there and listen to some other guy who's trying to sell us the business or get a commission on it tell us what the future's going to be - +like I say, it's very naive. + +Buffett also gives us a test: + +When they make these offerings, investment bankers display their humorous side: They dispense income and balance sheet projections extending five or more years into the future for companies they barely had +heard of a few months earlier. If you are shown such schedules, I suggest that you join in the fun: Ask the investment banker for the one-year budgets that his own firm prepared as the last few years began +and then compare these with what actually happened. + +The consultant to TransCorp was hired and paid by the company to advise the CEO on how he should be paid. "If I tell the CEO what he wants to hear, he will pay me well, rehire me and recommend me to other +CEOs. And if I make it sound complicated it will be easier to send a larger bill " + +How do we act as an employee? If our boss wants a particular answer, do we give it? To quote the German proverb: "Whose bread I eat, his song I sing." Warren Buffett says: + +I would say that the typical corporate organization is structured so that the CEOs opinions, biases and previous beliefs are reinforced in every possible way. Staffs won't give you any contrary +recommendations - they'll just come back with whatever the CEO wants. And the Board of Directors won't act as a check, so the CEO pretty much gets what he wants. + +"I don't like to be embarrassed and have my name and reputation threatened with disgrace," said the CEO ofTransCorp. + +How can we change people? Benjamin Franklin said: "Would you persuade, speak of interest not of reason." Since the risk of losing is more motivating than the chance of gaining, we stand a better chance +changing people if we appeal to their fear oflosing something they value - job, reputation, status, money, control, etc. + +It is often better to avoid situations where we need to change people. Changing people is hard as Warren Buffett says, "I'd say that the history that Charlie and I have had of persuading decent, intelligent +people who we thought were doing unintelligent things to change their course of action has been poor.. . When + +53 + +people want to do something, they want to do something." + +Changing people affects their motivation, feelings of responsibility, and tendency to reciprocate. It is better when people act out of their own free will. Warren Buffett illustrates: + +We want the manager of each subsidiary to run their business in the way they think is best for their operation we'll never tell a subsidiary manager which vendor to patronize or + +anything of that sort. Once we start making those decisions for our managers, [3mwe [0mbecome responsible for the operation and they're no longer responsible for the operation. And they're responsible for their +operations. That means that they get to make the call, that it's up to them to do what's best for their subsidiary and that it's up to any other company that wants to do business with their operation to prove +to them why it's best That's the + +Berkshire approach. I think, on balance, our managers like it that way - because they're + +not going to get second-guessed and nobody will go over their heads. + +Keep in mind + +Don't automatically trust people who have something at stake from your decision. Ask: What are the interests? Who benefits? + +Understand people's motivations. Money, status, love of work, reputation, position, power, envy? What are they rewarded or punished for? Are they benefiting or losing from the present system? + +People's interests are not only financial. They could also be social or moral. For example, public embarrassment, social exclusion, conscience, shame or guilt may cause people to stop some undesirable +behavior. For example, by requiring restaurants to post hygiene quality scores in their front windows, the Los Angeles county health department caused a dramatic improvement in restaurant hygiene and a +reduction in food-related illnesses. + +The ancient Greek philosopher Plato said: "Do not train boys to learning by force and harshness, but lead them by what amuses them, so that they may better discover the bent of their minds." Pressuring people +or giving them orders often doesn't work. It is better to convince people by asking questions that illuminate consequences. This causes them to think for themselves and makes it more likely that they discover +what's in their best interest. + +SELF-SERVING TENDENCIES AND OPTIMISM + +Man suffers much because he seeks too much, is foolishly ambitious and grotesquely overestimates his capacities + +Isaiah Berlin (Russian-British philosopher, 1909-1997) + +54 + +"Things that happen to others don't happen to me. " + +We see ourselves as unique and special and we have optimistic views of ourselves and our family. We overestimate the degree of control we have over events and underestimate chance. + +The 18th Century English poet Edward Young said: "All men think all men are mortal but themselves." Most of us believe we are better performers, more honest and intelligent, have a better future, have a +happier marriage, are less vulnerable than the average person, etc. But we can't all be better than average. + +We tend to overestimate our ability to predict the future. People tend to put a higher probability on desired events than on undesired events. For example, we are over-optimistic about the outcome of planned +actions. Optimism is good but when it comes to important decisions, realism is better. + +After making a huge mistake, john said· "I was arrogant. My past success caused me to believe I could do anything. " + +Marcus Porcius Cato said: "Men's spirits are lifted when the times are prosperous, rich and happy, so that their pride and arrogance grow." We tend to over-estimate our abilities and future prospects when we +are knowledgeable on a subject, feel in control, or after we've been successful. As financial writer Roger Lowenstein writes in When Genius Failed· The Rise and Fall of Long-Term Capital Management: "There is +nothing like success to blind one of the possibility of failure." + +What tends to inflate the price that CEO's pay for acquisitions? Studies found evidence of infection through three sources of hubris: 1) overconfidence after recent success, 2) a sense of self-importance; the +belief that a high salary compared to other senior ranking executives imply skill, and 3) the CEO's belief in their own press coverage. The media tend to glorify the CEO and over-attribute business success to +the role of the CEO rather than to other factors and people. This makes CEO's more likely to become both more overconfident about their abilities and more committed to the actions that made them media +celebrities. + +'1t worked because we made the right decisions. " '1t didn't work because of a bad business climate. " + +Experiments show that when we are successful (independent ifby chance or not), we credit our own character or ability. Warren Buffett says: + +Any investor can chalk up large returns when stocks soar, as they did in 1997. In a bull market, one must avoid the error of the preening duck that quacks boastfully after a + +55 + +torrential rainstorm, thinking that its paddling skills have caused it to rise in the world. A right-thinking duck would instead compare its position after the downpour to that of the other ducks on the pond. + +When we fail, we blame external circumstances or bad luck. When others are successful, we tend to credit their success to luck and blame their failures on foolishness. When our investments turn into losers, +we had bad luck. When they turn into winners, we are geniuses. This way we draw the wrong conclusions and don't learn from our mistakes. We also underestimate luck and randomness in outcomes. + +When using advisers and if something turns out well, we take the credit, assigning the outcome to our skill. But if something turns out bad, we blame the advisor. + +Charles Munger tells us about the toast we seldom hear: + +... Arco was celebrating their huge triumph of making a lot of money out of the North Slope oilfields in Alaska. And the house counsel there was an Irishman who was very outspoken and had a fair amount of +charm. And he was highly regarded. So he could get by with talking frankly. And the whole group was toasting one another: "Aren't we great people for having done this great thing?" and this Irish house +counsel raised his glass and said "Well, I'd like to toast the man who really caused our triumph." He said, "Here's to King Faisal ... Every calculation we made was off by 200%. All the costs were way higher, +and the difficulties way greater than we ever conceived. All the predictions we made were totally asinine and wouldn't have worked with the oil prices we projected. But along came King Faisal and the oil +cartel and raised the price of oil so high that they made us all look good. Let's honor the proper man here tonight. " + +This is the kind of toast you will seldom hear in corporate life - because for most people, a toast like that will get you fired. And a guy who's bringing reality into a pleasant party, and making people face +their own limitations and errors, will have poor prospects. + +Bill is a surgeon who always uses surgery to handle health problems even if they could be cured by a less invasive procedure. + +As the old saying goes: "If the only tool you have is a hammer, you approach every problem as ifit were a nail." The more we know or think we know about a subject, the less willing we are to use other ideas. +Instead, we tend to solve a problem in a way that agrees with our area of expertise. And the more useful a given idea is + +-whether or not it's appropriate to the problem at hand- the more overconfident we are about its usefulness. In Bill's case, there may also be financial incentives to recommend a medical procedure. + +56 + +Experts love to extrapolate their ideas from one field to all other fields. They define problems in ways that fit their tools rather than ways that agree with the underlying problem. Give someone a tool and +they'll want to use it, and even overuse it, whether it's warranted or not. + +Why is man-with-a-hammer syndrome always present? Charles Munger answers: "Well if you stop to think about it, it's incentive-caused bias. His professional reputation is all tied up with what he knows. He +likes himself and he likes his own ideas, and he's expressed them to other people - consistency and commitment tendency [see 6. Consistency]. + +'1 hired heras my assistant since she was good-looking, articulate and hada university degree. She gave a great first impression. " + +How good are we at judging personalities? Sherlock Holmes says in Arthur Conan Doyle's The Sign of Four that: "It is of the first importance not to allow your judgment to be biased by personal qualities. I +assure you that the most winning woman I ever knew was hanged for poisoning three little children for their insurance-money, and the most repellent man of my acquaintance is a philanthropist who has spent +nearly a quarter of a million upon the London poor." + +We immediately classify people which brings to mind a host of associations. We often allow one trait to color all other characteristics and therefore judge people as better or worse than they really are. +Preconceived ideas about certain people, races, religions, or occupations cause us to automatically assume that an individual from a particular group has special characteristics. + +Physics Professor Roger Newton observes in The Truth of Science: "Scientists are human... they sometimes succumb to weaknesses such as jealousy, vanity, and, on very rare instances, even dishonesty." +Gian-Carlo Rota says in Indiscrete Thoughts: "A good mathematician is not necessarily a nice guy." + +"When I interview someone I have already formed an impression from reading the job applications. Then I just try to find confirming evidence at the interviews. " Interviews are often of limited use to predict +a potential employee's future behavior. As Psychology Professor Robyn Dawes notes in Rational Choice in an Uncertain World· "What can an interviewer learn in a half-hour to an hour that is not present in the +applicant's record?" + +An articulate person may be more persuasive than a reserved person, but the latter may know what he is talking about. + +Why do some people seem to have an intuition for evaluating people? Maybe + +57 + +their life experiences gives them the ability (by asking questions and observing behavior) to look for clues to an individual's character. + +Warren Buffett says on how to identify people that may cause problem: ''I'm not saying that you can take 100 people and take a look at 'em and analyze their personalities or anything of the sort. But I think +when you see the extreme cases + +- the ones that are going to cause you nothing but trouble and the ones that are going to bring you nothing but joy - well, I think you can identify those pretty well." Charles Munger adds, ''Actually, I +think it's pretty simple: There's integrity, intelligence, experience, and dedication. That's what human enterprises need to run well." + +Keep in mind + +German missionary Dr. Albert Schweitzer said: "An optimist is a person who sees a green light everywhere, while the pessimist sees only the red stoplight. The truly wise person is colorblind." + +Overconfidence can cause unreal expectations and make us more vulnerable to disappointment. + +Recognize your limits. How well do you know what you don't know? Don't let your ego determine what you should do. Charles Munger says, "It is remarkable how much long-term advantage people like us have gotten +by trying to be consistently not stupid, instead of trying to be very intelligent. There must be some wisdom in the folk saying: 'It's the strong swimmers who drown."' + +Warren Buffett says: "We won't do anything that we don't think we understand ourselves." + +Focus on what can go wrong and the consequences. Build in some margin of safety in decisions. Know how you will handle things if they go wrong. Surprises occur in many unlikely ways. Ask: How can I be wrong? +Who can tell me ifl'm wrong? + +By developing only a handful of strengths, we have an impoverished toolbox + +only hammers. We need a full toolkit. Since problems don't follow territorial boundaries, we must compensate for the bias of one idea by using important ideas from other disciplines. + +Consider people's actual accomplishments and past behavior over a long period of time rather than first impressions. Since people leave track records in life, an individual's paper record is often predictive +of future performance and behavior. + +When comparing records or performances, remember that successes draw far more attention than failures. + +58 + +SELF-DECEPTION AND DENIAL + +Nothing is easier than self-deceit. For what + +each man wishes, that he also believes to be true. + +Demosthenes (Greek statesman, 384-322 BC) + +john couldn't admit to others that he'd made a bad deal. "I was almost right! I lost money, but others lost more. It wasn't my fault. It was outof my control! You win some, you lose some. " + +We deny and distort reality to feel more comfortable, especially when reality threatens our self-interest. To quote the Austrian psychologist Sigmund Freud: "Illusions commend themselves to us because they +save us pain and allow us to enjoy pleasure instead." We view things the way we want to see them. We hear what we want to hear and deny what is inconsistent with our deeply held beliefs. We deny unpleasant +news and prefer comfort to truth. We choose the right people to ask. We make sense of bad events by telling ourselves comforting stories that give them meaning. + +'1 hope the project succeeds in time and on budget. " + +In relating the events of the 5th Century B.C. war between the main adversaries Athens and Sparta, the Greek historian Thucydides wrote: "... their judgment was based more upon blind wishing than upon any +sound prediction; for it is a habit of mankind to entrust to careless hope what they long for, and to use sovereign reason to thrust aside what they do not desire." Wishful thinking is rooted in denial, +offering us a more pleasant reality. In business, this is one reason for project delays and cost overruns. + +We believe something is true because it sounds believable or we want to believe it, especially with issues of love, health, religion, and death. This is one reason why people follow gurus. They encourage +followers to trust their hearts and forget their heads. Philosopher and mathematician Bertrand Russell said in Skeptical Essays: "What is wanted is not the will to believe, bur the will to find out, which is +the exact opposite." + +Keep in mind + +In his famous 1974 commencement address at Caltech, American physicist Richard Feynman warned against self-deception: "The first principle is that you must not fool yourself- and you are the easiest person to +fool." + +Austrian philosopher Ludwig Wittgenstein said in Culture and Value: + +"Nothing is so difficult as not deceiving oneself." We have to see the world as + +59 + +it is. Not for what it was or for what we want it to be. Refusing to look at unpleasant facts doesn't make them disappear. Bad news that is true is better than good news that is wrong. + +Denial must be weighed against social, financial, physical and emotional costs. When the cost of denial is worse than the benefit of facing reality, we must face reality. + +CONSISTENCY + +The difficulty lies not in the new ideas, but in escaping the old ones, which ramify, for those brought up as most of us have been, into every corner of our minds. + +John Maynard Keynes (British economist, 1883-1946) + +Once we've made a commitment - a promise, a choice, taken a stand, invested time, money or effort - we want to remain consistent. We want to feel that we've made the right decision. And the more we have +invested in our behavior the harder it is to change. + +'1 can't behave in a way that is inconsistent with my self-image. I have a reputation to uphold I don't want to look weak, dumb or lose face. I want to be seen as nice, smart and in control " + +Scottish philosopher and economist Adam Smith said in The Theory of the Moral Sentiments: "The opinion which we entertain of our own character depends entirely on our judgments concerning our past conduct. It +is so disagreeable to think ill of ourselves, that we often purposely turn away our view from those circumstances which might render that judgment unfavorable." + +We want to maintain a positive self-image. When that is violated, we use different defenses in order to justify our behavior. We also behave in ways that are consistent with how others see us. If people label +us as talented, we try to appear talented whether or not it is true. + +Why do we hang on to a bad idea, an unhappy relationship or a losing investment? Why do politicians continue fighting wars long after it is clear the war is a bad idea? + +The more time, money, effort or pain we invest, the more we feel the need to continue, and the more highly we value something - whether or not it is right. We don't want to waste our efforts. This way we +protect our reputation and avoid the pain of accepting a loss. If people challenge our decisions, we become even + +60 + +more committed we are right. And the more individual responsibility we feel for a commitment, the harder it is to give up. + +In Too Much Invested to Quit, psychologist Allan Teger said about the Vietnam War: "The longer the war continued, the more difficult it was to justify the additional investments in terms of the value of +possible victory. On the other hand, the longer the war continued, the more difficult it became to write off the tremendous losses without having anything to show for them." + +John wanted to employ a new vice president. He told everyone that the guy was terrific but the new employee turned out to be a disaster. Instead of dealing with the mistake, john kept the guy, costing him +much money and aggravation. + +We tend to make fast judgments. It is hard to change a first conclusion since a change implies we may be wrong (especially if we need to explain the change to others). We associate being wrong with a threat +to our self-interest. + +Warren Buffett says: "What the human being is best at doing is interpreting all new information so that their prior conclusions remain intact." The 17th Century English philosopher Francis Bacon adds: "it is +the peculiar and perpetual error of the human intellect to be more moved and excited by affirmatives than by negatives; whereas it ought properly to hold itself indifferently disposed towards both alike." We +look for evidence that confirms our ideas, beliefs, and actions. Devising reasons why we might be wrong doesn't come easily. For example, when we've made an investment, entered into a relationship, or made +other types of commitments, we tend to seek out evidence confirming that it was the right decision and to ignore information that shows it was wrong. + +'1 don't want to sell this declining stock and face a loss. I put $100,000 into this. I must prove to others and myself I made the right choice. " + +After we buy a stock, we are more confident it was a good buy than before the investment. We want to feel we did the right thing and keep our beliefs consistent with what we've done. But nothing has changed. +It is the same business before and after. + +'1 think it's foolish to abandon a project on which $10 million has been sunk,"said the CEO ofTransCorp. + +Why do we do things merely because we've paid for them? + +Assume John paid a $1,000 non-refundable fee for a conference, but he no longer wants to participate. He feels he can't afford to waste the already spent + +$1,000. Should he go to the conference because he already spent $1,000? Should + +61 + +he pay $1,000 to do something he doesn't want to do? The money is lost forever. Isn't it better to say that the already spent $1,000 is the cost of doing what he really wants to do? Isn't it better to pay to +do what you want? + +John and Mary sit through a lousy movie simply because they bought the tickets. They can't get the eight dollars they spent back so it shouldn't make a difference whether they leave or not. The consequences +are the same - the money has already been spent. The choice is between having a good time or a lousy time. + +"We invested in a new machine based on the volume-increase set out in the strategic plan. Unfortunately, volume decreased. " + +We are most consistent when we have made a public, effortful or voluntary commitment. The more public a decision is, the less likely it is that we will change it. Written commitments are strong since they +require more effort than verbal commitments and can also be made public. + +Isn't it better to do what makes sense than to stay consistent with a strategic plan that isn't working? Warren Buffett says, "We do have a few advantages, perhaps the greatest being that we don't have a +strategic plan. Thus we feel no need to proceed in an ordained direction (a course leading almost invariably to silly purchase prices) but can instead simply decide what makes sense for our owners." + +Charles Munger says on the value oflong-term plans: + +We have very much the philosophy of building our enterprise that Sir William Osler had when he built the John Hopkins Medical School from a very poor start into a model medical school for the whole world. And +what Sir William Osler said - and he quoted this from Carlyle - was: "The task of man is not to see what lies dimly in the distance, but to do what lies clearly at hand." + +We try to respond intelligently each day, each week, each month, each year to the information and challenges at hand - horrible assaults that have to be deflected, things that have to be scrambled out of, the +unusual opportunities that come along- and just do the best job we can in responding to those challenges. Obviously, you look ahead as far as you can. But that's not very far. But if you respond intelligently +and diligently to the challenges before you, we think you'll tend to end up with a pretty good institution. + +In his Scientific Autobiography and Other Papers, German physicist Max Planck said: "A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its +opponents eventually die and a new generation grows up that is familiar with it." + +62 + +Warren Buffett adds: + +I think it was Keynes who said, "Most economists are [3mmost [0meconomical about [3mideas [0m- they make the ones they learned in graduate school last a lifetime." What happens is that you spend years getting your Ph.D. +in finance. And [in the process], you learn theories with a lot of mathematics that the average layman can't do. So you become sort of a high priest. And you wind up with an [3menormous [0mamount of yourself in +terms of your ego - and even professional security- invested in those ideas. Therefore, it gets very hard to back off after a given point. + +'1 have invested 15 years of my life in this, so I won't walk away now. " + +Let's say that a couple is in a bad marriage but have spent 15 years together. Should they get a divorce or should they "stay in there" and remain unhappy because they have invested 15 years of their life? + +What other traps may consistency cause us to fall into? + +John and his family decided to buy a new car. They chose a dealership that agreed to sell the car $1,000 below the competition. Then the salesman changed the terms. He had discovered an error. In the end, the +price ended up $200 above competition. + +In the low-ball technique, the salesperson gives the customer an incentive to enter into an agreement with the intention of changing the terms to the seller's advantage (either by removing the advantage or +adding something undesirable). Once John made the decision and took the time and effort to buy a new car, he committed to the purchase. Otherwise he would appear inconsistent. Instead of backing out of the +deal, he found new reasons to justify his purchase of the car. Low-ball is often used by politicians in elections. + +"What a great deal for a refrigerator,"Mary said, reading the advertisements. When she gets to the store, the salesperson tells her that they ran out of the advertised specials. But they have a similar one in +stock. And it is only $150 more. She buys the refrigerator. She is already committed to buying a refrigerator and the salesperson only forces her to be consistent. + +Sitting at the negotiation table, the opponent asked John, ''Did you know that you and the managers ofTransCorp are widely known to be cooperative and fair?" + +In the labeling technique, people try to get us committed by first applying a label to our personality or values that is consistent with the behavior they want us to take. We often comply to later requests +that are consistent with the label. That is why John's opponent gave John a reputation to uphold. + +63 + +"Will you take my kids to school today?" Mary's neighbor asked One month later, Mary found herself still driving her neighbors' kids to school and even to the movies. How do people seduce us financially, +politically or sexually? They make us first agree to a small request, so small that no one would refuse. This way they create a commitment. Then they make a second and larger request (the one they wanted all +along). We are then more likely to comply. This "foot-in-the-door technique" is based on the principle that if people ask us to make a small commitment, we are more likely to agree to a larger request because +we want to appear consistent. One study showed that 76% of a group of homeowners agreed to put a large billboard on their front lawn, saying "Drive Carefully." Two weeks earlier, the homeowners had been +approached by other researchers, asking them to place a tiny sign saying "Be a Safe driver" on their car windows. They now saw themselves as concerned citizens and people who care enough about driver safety +to take a stand. They also believed that was how other people saw them. When they were later approached, 76% agreed putting up the large sign just to be consistent. In contrast, only 17% of subjects who +hadn't received the earlier visit agreed to put + +up the large sign. + +When people get us to commit, we become responsible. One experiment staged a theft to find out if onlookers would risk personal harm to stop a crime. A researcher sat on a beach blanket and listened to his +portable radio five feet from the blanket of a randomly chosen person. After awhile, the researcher left the blanket to stroll the beach. A few minutes later a second researcher, pretending to be a thief, +grabbed the radio and ran away. Four people out of twenty put themselves in harm by challenging the thief. But when the procedure was tried somewhat differently, nineteen people became vigilantes, and tried +to stop the thie£ The difference? Before taking his stroll, the researcher asked the subject to "please watch my things" which they all agreed to do. + +The 17th Century English poet Samuel Butler wrote: "He that complies against his will, is of his own opinion still." How do we get people to take inner responsibility for their actions? Make it voluntary. We +take responsibility for our behavior in cases when we are internally motivated by satisfaction or interest, when we feel in control, and when we are free from incentives or outside pressure. + +Strong convictions can be dangerous. + +The German philosopher Friedrich Wilhelm Nietzsche wrote: "Convictions are more dangerous enemies of truth than lies." Intense commitments for political, religious or philosophical ideas create an ideological +bias. People with various political, religious, and philosophical interests are motivated to seek the truths that + +64 + +confirm these interests. Never underestimate the power of ideology. They can act as a device for justifying war and violence. As Blaise Pascal wrote: "Men never do evil so completely and cheerfully as when +they do it from religious conviction." + +Charles Munger tells us about the danger of ideology: + +Heavy ideology is oneof the most extreme distorters of human cognition. Look at these Islamic Fundamentalists who just gunned down a bunch of Greek tourists shouting, "God's work!" + +Ideology does some strange things and distorts cognition terribly. If you get a lot of + +heavy ideology young - and, then, you start expressing it - you are really locking your brain into a very unfortunate pattern. And you are going to distort your general cognition. There's a very interesting +history if you take Warren Buffett as an example of worldly wisdom: Warren adored his father - who was a wonderful man. But he was a very heavy ideologue, (right wing, it happened to be), who hung around with +other very heavy ideologues, (right wing, naturally). Warren observed this as a kid. And he decided that ideology was dangerous - and that he was going to stay a long way away from it. And he has throughout +his whole life. That has enormously helped the accuracy of his + +cognition. + +I learned the same lesson in a different way. My father hated ideology. Therefore, all I had to do was imitate my father and, thereby, stay in what I regard as the right path. People like Dornan on the right +or Nader on the left have obviously gone a little daft. They're extreme examples of what ideology will do to you - particularly violently expressed ideology. Since it pounds ideas in better than it convinces +out, it's a very dangerous thing to do. + +Keep in mind + +A decision must be active. Lucius Annaeus Seneca said: "There is nothing wrong with changing a plan when the situation has changed." Irish writer Jonathan Swift said: ''A man should never be ashamed to own +that he has been in the wrong, which is but saying, in other words, that he is wiser today than he was yesterday." J.M. Keynes said: "When somebody persuades me that I am wrong, I change my mind. What do you +do?" Sometimes things don't go the way we believe they will. The solution is to face it and act. Charles Munger says: "We've done a lot of that - scrambled out of wrong decisions. I would argue that that's a +big part of having a reasonable record in life. You can't avoid wrong decisions. But if you recognize them promptly and do something about them, you can frequently turn the lemon into lemonade." + +If we can get people committed in advance, they tend to live up to their + +commitment. For example, make people take a voluntary and public position on some issue. + +65 + +Don't force people to publicly make commitments that you don't later want the opportunity to change. + +When you are asked to perform a future action but are uncertain, ask yourself: Would I do this ifI had to do it tomorrow? + +Warren Buffett says, "The most important thing to do when you find yourself in a hole is to stop digging." Merely because you've spent money or time on some project or investment doesn't mean you must +continue to spend it in the future. Time, effort, and money spent are gone. Decisions should be based on where you want to be. Not where you've been. Base decisions on the present situation and future +consequences. What happened in the past may be a guide for estimating how likely something is to happen in the future. Ask: What do I want to achieve? What causes that? Considering what I know today and what +is likely to happen in the future, how should I act to achieve my goal? Will new money and time invested achieve my goal? Assume I never invested in this and it was presented to me for the first time, would I +invest in it today? If not, then stop and do something about it. As Charles Munger says: + +Berkshire extracted a lot of capital out ofit [the textile business] and put it elsewhere. And if Berkshire had tried to keep fighting the decline of that business with more and more money, it would have +blown most of its capital. There's a time to fight and there's a time to run away. One of my favorite stories, relevant to this story, involves a town in the South. There was this huge grocery store owned by +one of the great national chains. They're a formidable competitor and they had the dominant big grocery store in this town for many, many years doing big volume. Sam Walton of Wal-Mart announced that he was +opening a much bigger, better grocery store with a lot of other wonderful products at incredibly low prices. And the existing very experienced and successful chain, did not wait for Sam Walton's store to +open. They just closed their store right away. + +Let someone who wasn't committed to an earlier decision take over the issue. + +"Facts do not cease to exist because they are ignored," said British novelist Aldous Huxley. If we only look to confirm our beliefs, we will never discover if we're wrong. Be self-critical and unlearn your +best-loved ideas. Search for evidence that disconfirms ideas and assumptions. Consider alternative outcomes, viewpoints, and answers. Have someone tell you when your thinking is wrong. Warren Buffett says, +"Charlie and I believe that when you find information that contradicts your existing beliefs, you've got a special + +obligation to look at it - and quickly. " + +Follow the advice of the Italian artist and scientist Leonardo da Vinci: "We + +66 + +know well that mistakes are more easily detected in the works of others than in one's own. When you are painting you should take a flat mirror and often look at your work within it, and it will then be seen +in reserve, and will appear to be by the hand of some other master, and you will be better able to judge of its faults than in any other way." + +DEPRIVAL SYNDROME + +You don't change something people love. + +Faith Popcorn (American futurist) + +As we've seen in Part One, we have an aversion to loss. We dislike losing the things we have more than we appreciate gaining the things we don't have. + +When something we like is (or threatens to be) taken away, we often value it higher. Take away people's freedom, status, reputation, money or anything they value, and they get upset. We don't like to lose the +freedom to choose how to act or believe or what to have. For example, people are likely to fight a restrictive law that takes away a benefit they have enjoyed for a long time. The more we like what is taken +away or the larger the commitment we've made, the more upset we become. This can create hatred, revolts, violence and retaliations. + +How do people react when we try to lower their income? + +Charles Munger illustrates the power of deprival when negotiating takeaways in labor negotiations: + +You're facing deprival super-reaction syndrome - people just go bananas. And (B) the union representative has to bring his members the deprival message and endure the Pavlovian mere-association hatred that +results. Therefore, he won't do it - largely for that reason. So you have [3mtwo [0mpowerful psychological effects making it hell. + +All of those strikes in the late 1800s and the early 1900s where Pinkerton guards were shooting people were about takeaways. Arriving immigrants were willing to work cheap. And capitalist proprietors tried to +reduce wages - sometimes because they felt they had to because their competitors were doing it and sometimes because they simply wanted to make more money. At any rate, all of that murder and mayhem was the +result of deprival super-reaction syndrome plus the reality that nobody wanted to be the carrier of bad news. + +'1 shou/,d take the conservative approach. Failure is embarrassing and mayget me fired " People's aversion to losing may make people overly conservative or engage in cover-ups. + +67 + +The doctor told Mary: "You may die ifyou do not change your behavior. " + +Our loss aversion makes us more sensitive to information that has negative implications for us. For example, health-related messages can either focus on the benefits of performing an act (gain) or the +possible costs of not doing it (loss). One study showed that women were more likely to engage in breast self examination when they were presented with information emphasizing the possible negative +consequences (loss of good health, longevity) of not performing self-examination compared to information that focused on the benefits of doing it. Other studies show that when persuading people to undergo +risky medical procedures, it is more effective to focus on positive outcomes (e.g. survival rate) than negative ones (e.g. mortality rate). + +john tells Mary: '1 can't sell the stock now. I have to wait until it gets back up to what I paid for it. Anyway, I don't realize a loss unless I sell. " + +We hate to admit we've lost money. Our loss aversion contributes to status quo bias - we prefer to hang on to what we have. We even put a higher value on the things we already own than we are willing to pay +for the same things if we didn't own them (giving them up feels like a loss). This is why many companies offer money-back guarantees on their products. Once we have taken possession of some item, we are not +likely to return it. + +Charles Munger says, "The deprival super-reaction syndrome of man helps cause much ruin as people's cognition is distorted as a result of their suffering losses and seeing near misses." We hate to sell losing +stocks. It is the same as admitting to others and ourselves that we've made a mistake. We therefore hold on to our losers too long and sell our winners too soon. A realized loss feels worse than suffering the +same loss on paper. The pain of feeling responsible for making a bad decision also plays a role (regret). The stock may bounce back after we've sold. And the more money and effort we've put in, the harder it +is to let it go. + +We also feel that losing the opportunity to make money is less painful than losing the same amount of money. But a lost opportunity of making $100 has the same value as a real loss of $100. + +john's friend Allan bought a house five years ago for $200,000. + +Four years later, Allan's company moves to another city. The local real estate market is depressed. He is offered $170,000 but feels he can't afford a loss. So he waits another year and this time the offered +price is $150,000. + +Isn't it better for Allan to concentrate on what the house is worth rather than on what he paid? + +68 + +John kept pouring dollars in the machine. ''I got Cherry, Cherry, Bar. Tm close now. " We want and place higher value on something when we almost have it and lose it. Charles Munger says, "One reason why +horse races, bingo and these things have always been so popular is because of all these near misses." Frequent near misses are like small reinforcements and make us want to try again and again. + +Just as people take larger risks when threatened, after a loss, we want to catch up, so we end up taking more risks to get even. But as Warren Buffett and Charles Munger say: + +Buffett: A very important principle in investing is that you don't have to make it back the way you lost it. In fact, it's usually a mistake to try to make it back the way you lost it. + +Munger: That's the reason so many people are ruined by gambling - they get behind and then they feel like they have to get it back the way they lost it. It's a deep part of human nature. It's very smart just +to lick it - by will... + +Buffett: One of the important things in stocks is that the stock does not know that you own it. You have all these feelings about it: You remember what you paid. You remember who told you about it - all these +little things. And it doesn't give a [3mdamn. [0mIt just sits there. If a stock's at $50, somebody's paid $100 and feels terrible; somebody else has paid $10 and feels wonderful - all these feelings. And it has no +impact whatsoever ... + +John and Mary's daughter didn't want the toy they gave her; she wanted the toy they didn't give her. + +Michel de Montaigne said: "To forbid us something is to make us want it." We want what we can't have. Forbidden fruit tastes best. Mark Twain said, "It was not that Adam ate the apple for the apple's sake, +but because it was forbidden. It would have been better for us - oh infinitely better for us - if the serpent had been forbidden." Forbid someone to do something and they find it more attractive than they did +before it was forbidden. For example, when Miami banned the use of phosphate-based detergents, people turned to smuggling in supplies and hoarding (since fear of scarcity encourages hoarding) and even rated +the banned products as better than before. + +"Since a real estate lot in this area is both rare and hard to obtain, I want it. " + +We want and value more what is scarce or unique. We want what is (or threatens to be) less available. The less available it is, the more we desire it. That's why we subscribe to newsletters containing +exclusive and restricted information. And why we participate in initial public offerings and buy stocks on hot tips. + +We value higher what has recently been less available than things that have + +69 + +been scarce all along. We fall for limited offers and deadlines like, "The offer ends at midnight. We only have a few left. This is the last chance. "By making things less available, merchants make them seem +more valuable. + +lot of people are competing for this lot at the auction." + +How do we create demand? Create competition. Make people perceive there is a huge competition for the item and limit the number of people that can participate in the bidding. If others want what's scarce, we +want it even more. + +When we can't get something, we lower our opinion of it. When we can get something that others don't want, we don't want it either. + +Keep in mind + +Know your goals and options. Ask: Why do I want this? For emotional or rational reasons? + +What you paid for your house, stock, or car has no relevance to its value. If the + +value is below what you paid, you don't have to get even. If you bought a stock for $100 and it is now $50, you should sell it, if it is not worth more than $50. Ask: Suppose I hadn't made the investment, +would I make this investment today at today's price? + +Remember that people respond to immediate crisis and threats. Anything that happens gradually, they tend to put off. If we want people to take a risk, we should make them feel behind (losing). If we want them +to stay with the status quo or reject risk, we should make them feel safe. + +Charles Munger shows how we can use the force of deprival to persuade (for a reputable reason): + +In Captain Cook's day, he took these long voyages. At the time, scurvy was the dread of the long voyage. And in scurvy, your living gums putrefy in your mouth - after which the disease gets unpleasant and +kills you. And being on a primitive sailing ship with a bunch of dying sailors is a very awkward business. So everybody was terribly interested in scurvy, but they didn't [3mknow [0mabout Vitamin C. Well, Captain +Cook, being a smart man with a multiple-model kind of approach, noticed that Dutch ships had less scurvy than English ships on long voyages. So he said, "What are the Dutch doing that's different?" + +And he noticed they had all these barrels of sauerkraut. So he thought: 'Tm going on these long voyages. And it's very dangerous. Sauerkraut may help." So he laid in all this sauerkraut which, incidentally, +happens to contain a trace of vitamin C. But English sailors were a tough, cranky and dangerous bunch in that day. They hated "krauts". And they were used to their standard food and booze. So how do you get +such English sailors to eat sauerkraut? + +70 + +Well, Cook didn't want to tell 'em that he was doing it in the hope it would prevent scurvy - because they might mutiny and take over the ship if they thought that he was taking them on a voyage so long that +scurvy was likely. + +So here's what he did: Officers ate one place where the men could observe them. And for a long time, he served sauerkraut to the officers, but not to the men. And then, finally, Captain Cook said, "Well, the +men can have it one day a week." + +In due course, he had the whole crew eating sauerkraut. I regard that as a very constructive use of elementary psychology. It may have saved God knows how many lives and caused God knows how much achievement. + +STATUS Quo AND Do-NOTHING SYNDROME + +Nothing will ever be attempted if all possible objections must first be overcome. + +Samuel Johnson + +When john and Mary bought their new car, they stuck to their usual brand. + +We prefer to keep things the way they are. We resist change and prefer effort minimization. We favor routine behavior over innovative behavior. + +The more emotional a decision is or the more choices we have, the more we prefer the status quo. This is why we stick with our old jobs, brand of car, etc. Even in cases where the costs of switching are very +low. + +'1 fear the social consequences if I make the wrong choice, so I decide to do nothing. " We want to feel good about the choices we make so we can justify our actions for others and ourselves. We are more +bothered by harm that comes from action than harm that comes from inaction. We feel worse when we fail as a result of taking action than when we fail from doing nothing. + +We prefer the default option, i.e., the alternative that is selected automatically unless we change it. In a real-life experiment on auto insurance rates, car drivers in New Jersey and Pennsylvania were given +the choice ofa limited right to sue for pain and suffering in exchange for lower insurance rates. But the default option was different for each state. Car owners in New Jersey were automatically given the +limited right unless they made an active decision and said differently. In Pennsylvania, the default option was the full right to sue. What happened? Citizens of both states preferred the default option. 79% +of New Jersey drivers preferred the limited right to sue, whereas 70% of Pennsylvania drivers preferred the full right to sue. The difference in amount spent on insurance in the two states was about $200 +million. The preference for defaults has also been found in decisions about organ donation, health care plans, and pension savings. + +71 + +Sometimes we don't act when we know we should. We ignore Warren Buffett's Noah principle: "Predicting rain doesn't count; building arks does." + +"Why invest resources in something today since we don't get any credit for preventing something we don't even know will happen. " + +We often ignore distant problems and we are reluctant to prevent future threats. Warren Buffett says: "It took Noah 20 years to build an ark. And people said he was being silly because the skies were +beautiful. And of course, the whole time, he looked stupid- until it started raining. You can spend a long time building an ark while everybody else is out there enjoying the sun." + +Keep in mind + +Deciding to do nothing is also a decision. And the cost of doing nothing could be greater than the cost of taking an action. + +Remember what you want to achieve. + +Once we know what to do, we should do it. The 19th Century British biologist Thomas Henry Huxley said: "Perhaps the most valuable result of all education is the ability to make yourself do the thing you have +to do when it ought to be done whether you like it or not. It is the first lesson that ought to be learned and however early a person's training begins, it is probably the last lesson a person learns +thoroughly." + +IMPATIENCE + +The CEO ofTransCorp wants his bonus today and therefore he makes a decision that increases this year's profit at the cost of a possibly larger profit in the foture. + +We give more weight to the present than to the future. We seek pleasure today at a cost of what may be better in the future. We prefer an immediate reward to a delayed but maybe larger reward. We spend today +what we should save for tomorrow. This means that we may pay a high price in the future for a small immediate reward. For example, we buy things we can't afford on credit cards. + +We are impatient in the short run and patient in the far away future. Studies show that we tend to become less patient when rewards are more immediate. Our discount rates (the values we assign to something) +are higher in the short run than in the long run. For example, when a small reward is due tomorrow and a larger reward is due in one year, people often prefer the small immediate reward. But when the small +reward is due in one year and the larger reward in two years, people tend to prefer the larger long-term reward. Studies show that one explanation for this is that outcomes occurring in the future are +perceived as less certain. + +72 + +Keep in mind + +Michel de Montaigne said: "I conceive that pleasures are to be avoided if greater pains be the consequence, and pains to be coveted that will terminate in greater pleasures." Consider both the short and +long-term consequences of a decision. Weigh present good/bad against future good/bad. Short-term suffering may lead to long term pleasure. + +IO. ENVY [1mAND JEALOUSY [0mMan will do many things to get himself loved; he will do all things to get himself envied. + +-MarkTwain + +Aristotle said: "Envy is pain at the good fortune of others." We evaluate our own situation by comparing what we have with what others have. Aristotle continues: "We envy those who are near us in time, place, +age or reputation." It is people similar to us we envy most. Financial historian Charles P. Kindleberger says in Manias, Panics, and Crashes: "There is nothing so disturbing to one's well-being and judgment +as to see a friend get rich." For example, studies show that how happy we are is partly determined by where we stand in relation to similar others. The 19th Century German philosopher Arthur Schopenhauer +said: ''As Hobbes observes, all mental pleasure consists in being able to compare oneself with others to one's own advantage." + +We are jealous when we perceive a threat to a valued relationship. Studies show that jealousy is ranked among the top three motives for murder. + +Keep in mind + +Bertrand Russell said that envy is one of the fundamental causes of human suffering. The 18th Century French philosopher and mathematician Marquis de Condorcet said: "Enjoy your own life without comparing it +with that of another." As long as you achieve your goals, it shouldn't matter if someone else does better. + +Studies show that it matters whether we believe that others deserve their success. Aristotle said: "The best way to avoid envy is to deserve the success you get." + +On the other hand, the 18th Century Dutch physician Bernard de Mandeville said that vices such as greed, envy, and vanity all lead to public benefits by encouraging enterprise. + +73 + +II. CONTRAST COMPARISON + +Fill one bucket with cold water, another with hot water, and a third with water at room temperature. Put one hand in the bucket of cold water and the other hand in the bucket of hot water. Then put both your +hands in the bucket of room temperature water. What happens? You will feel that your cold hand feels warmer and that your warm hand feels colder. + +We judge stimuli bydifferences and changes and not absolute magnitudes. For example, we evaluate stimuli like temperature, loudness, brightness, health, status, or prices based on their contrast or difference +from a reference point (the prior or concurrent stimuli or what we have become used to). This reference point changes with new experiences and context. + +This means that how we value things depend on what we compare them with. + +The grossly overpriced $100 tie seemed reasonable after john bought the fairly priced + +$1,500 suit. + +The order in which something is presented matters. Sales people often try to sell the more costly item first. We are out buying a computer and some diskettes. In comparison to $1,500 computer, diskettes at +$10 seem like a bargain. After we buy the big ticket items, the add-ons seem cheap in comparison. + +Experiments have shown that we go across town to save $10 on a clock radio but not to save $10 on a large-screen TV. The difference between $100 and $110 seems like a larger saving than the difference between +$2850 and $2860. But it's the same $10 saving. + +"What I am used to getting in social benefits is the norm against how I measure fairness,"says john's friend Mark. + +A hotel has been renting rooms for $100 a night. The day after a hurricane, the hotel raises its prices to $150. Studies show that we consider this unfair. We determine what is fair or not in reference to +what we have been used to. This means that policies that have habit-forming consequences may be hard to reverse if they are seen as a loss. + +One ofTransCorp's subsidiaries developed a high-priced version of the machine. Even if it doesn't sell well, it will help induce customers to buy their cheaper (but still expensive) version. + +The same thing may appear attractive when compared to less attractive things and unattractive when compared to more attractive things. For example, studies show that a person of average attractiveness is seen +as less attractive when + +74 + +compared to highly attractive others. Charles Munger gives another example: "In my generation, when women lived at home until they got married, I saw some perfectly terrible marriages made by highly desirable +women because they lived in terrible homes. And I've seen some terrible second marriages which were made because they were slight improvements over an even worse first marriage." + +In one experiment, a group of people was asked to choose between $6 and an elegant pen. Most choose the cash. Another group of people was asked to choose between $6, the elegant pen, or an inferior pen. Most +choose the elegant pen. By adding an inferior option, another option seemed more attractive. + +Mary is looking at houses. The real estate broker knows that the house he is trying to sell Mary is in poor shape and a bad area. He starts by showing Mary bad properties in an ugly neighborhood. Afterwards, +he takes her to the house he wanted to sell all along. Suddenly this house and the area seem great in comparison to the other houses she saw. + +Another example of contrast comparison is when we interview one job candidate after another. + +"If we slowly and gradually over time manipu/,ate the numbers, the auditors won't notice it." + +Contrasts may blind us to change until it's too late. For example, we often don't notice the bad behavior of others if it goes sour gradually over time. + +Often we see reality as constant, although it gradually changes. A stimulus must reach an absolute threshold before we can detect it. Before we notice a change in a stimulus, a certain relative change most +occur. If the change is slow enough, we don't notice the change. Our ability to detect and react to changes in a stimulus decreases as its magnitude increases. To a small stimulus, only a small amount must be +added. To a larger stimulus, a large amount must be added. + +Sometimes it is the small, gradual, invisible changes that harm us the most. Warren Buffett says: "One of the problems in society is that the most important issues are often these incremental type things." He +continues: + +The world is not going to come to an end because tomorrow there are 200 or 250 thousand more people on the planet than there were today. That's about the number it grows every day... it is like eating about +300 calories more each day than you burn up; it has no effect on you today. You don't get up from the table and all of a sudden everybody says, "My God, you look fat compared to when you sat down!" But, if +you keep doing it over time, the incremental problems are hard to attack because that one extra piece of piedoesn't really seem to make a difference. The 250,000 people tomorrow don't seem to make any +difference, but + +75 + +the cumulative effects of them will make a huge difference over time, just like overeating will make a huge difference over time. The time to attack those problems is early. + +Keep in mind + +Evaluate people and objects by themselves and not by their contrast. + +12 . .ANCHORING + +The CEO informs john what he told the board members of TransCorp: "Our costs were one million over budget but I told them we were three million over. They were thrilled when I later told them it was only one +million. I always set low targets to exceed expectations. " + +We are over-influenced by certain information acting as a reference "anchor" for future judgments. + +'1 made a bad investment, paying $50 for something now worth $40,"says John. We don't price a thing according to its value but its relative price. If we for example bought a stock for $50 with a present price +of $40, we judge how good our decision was in reference to our purchase price. Or if a stock we consider buying trades around $50 for some time and drops to $35, we tend to get anchored on the $50 and +automatically assume that $35 is a bargain. The present + +price of a stock in relation to some past quote doesn't mean anything. The underlying business value is what matters. + +One of TransCorp's employees was on trial for backdating options. '1 demand a sentence of 5 years,"said the prosecutor. '1 suggest 4.5 years,"countered the defense. The initial figures being presented can +also influence legal decisions. For example, the value at which a lawsuit settles or the damages a judge awards in a civil case. Having the last word in court is sometimes disadvantageous. Studies show that +the defense's sentencing recommendation is strongly influenced by the prosecutor's demand, which in turn drives judicial sentencing. + +Studies also show that even randomly determined numbers may influence experienced legal professionals. + +John's friend said· /ls a used car salesman, I anchor a potential buyer to a high price and then slowly reduce it. This way I get a good final price and the customer perceives he got a good deal. " + +A friend of John and Mary was selling his chain of ice cream stores. The buyer had discussed a price of $10 million. But the seller researched prices of similar + +76 + +businesses. He outlined his research for the buyer and told him his target price of $15 million. Then the seller started to negotiate on his methodology, not on the price. The $15 million got anchored with +the buyer as the basis for further discussion. The seller finally sold his stores for $13 million. + +Keep in mind + +• Consider choices from a zero base level and remember what you want to achieve. + +• Adjust information to reality. + +VIVIDNESS AND RECENCY + +The attention which we lend to an experience is proportional to its vivid or interesting character; and it is a notorious fact that what interests us most vividly at the time is, other things equal, what we +remember best. + +William James (American psychologist and philosopher, 1842-1910) + +John invests in a company based on a beautifully written quarterly earnings report and an entertaining presentation. + +The more dramatic, salient, personal, entertaining, or emotional some information, event or experience is, the more influenced we are. For example, the easier it is to imagine an event, the more likely we are +to think that it will happen. + +We are easily influenced when we are told stories because we relate to stories better than to logic or fact. We love to be entertained. Information we receive directly, through our eyes or ears has more +impact than information that may have more evidential value. A vivid description from a friend or family member is more believable than true evidence. Statistical data is often overlooked. Studies show that +jurors are influenced by vivid descriptions. Lawyers try to present dramatic and memorable testimony. + +"Seeing the face of a 9-year old girl who is suffering feels awful. " + +Joseph Stalin said: ''A single death is a tragedy; a million deaths is a statistic." Information that moves us emotionally makes us pay greater attention to the event itself than to its magnitude. Statistics +rarely spark our emotions. An individual face and name will. + +A Chinese proverb says: "Kill one, frighten ten thousand." We often overestimate events that are unlikely to happen merely because they receive attention in the news. Drama and danger sells. The media +capitalizes on fear because there is money in it. Major accidents, such as airplane crashes or shark attacks, grab people's attention and make headlines regardless of their probability. This causes us to +believe a problem is + +77 + +larger than it really is. Sometimes we believe an event has increased in frequency because we see it more. But the media may only cover it more. + +john sold every stock he owned since the media reported bad economic news. + +We give too much weight to information we've seen, heard, read or experienced most recently. For example, when judging performance, we overweigh what happened most recently and underweigh or ignore the long +term evidence or what on average happens (assuming those are representative of reality). + +We make predictions by extrapolating recent trends and conditions. The stock market falls into nose bleed territory and we assume the world is going under. After a bad event happens, we tend to overestimate +the likelihood of it happening again. For example, studies show that after an earthquake, the number of people carrying earthquake insurance rises sharply. + +Keep in mind + +• The media has its weaknesses, biases and vulnerability to manipulation and deception. Consider what is relevant and the normal outcome in similar situations. + +• Accurate information is better than dramatic information. Back up vivid stories with facts and numbers. + +• Separate noise and chance events from what is important. Ask: Is it relevant? Does it make sense? Is it representative evidence? Was it a random event? + +• Trends may be wrong. Ask: Is it a permanent or temporary effect? + +OMISSION AND ABSTRACT BLINDNESS + +We react to stimuli that we personally encounter or that grabs our attention. We react more strongly to the concrete and specific than to the abstract. We overweigh personal experiences over vicarious. We see +only what we have names for. We tend to focus only on the present information rather than what information may potentially be missing. For example, when planning, we often place too much importance on the +specific future event and not enough on other possible events and their consequences that can cause the event to be delayed or not happen. + +Today 14 million people didn't win the lottery. + +We base what is likely to happen on what we see. Not on what we don't see. We don't see what could have happened. We see the winners because they are vocal or visible and get media coverage. We don't see the +quiet losers. We see the successful forecasters. We don't see those who didn't predict well. We see the kind + +78 + +of risk that makes headlines. We don't see the statistical risk. We see the benefits of government expenditure. We don't see the costs and benefits of resources alternative use. We don't see the alternative +uses of taxpayers money for consumption, saving or investing. + +We see the available information. We don't see what isn't reported. Missing information doesn't draw our attention. We tend not to think about other possibilities, alternatives, explanations, outcomes or +attributes. When we try to find out if one thing causes another, we only see what happened, not what didn't happen. We see when a procedure works, not when it doesn't work. When we use checklists to find out +possible reasons for why something doesn't work, we often don't see that what is not on the list in the first place may be the reason for the problem. + +john asks his son Adam which university he would like to attend. Mary instead asks Adam which university he doesn't like. Adam both selects and rejects university B. Why would Adam both like and not like +university B? Because when we choose, we compare positive attributes but when we reject, we compare negative attributes. Since university B had more positive and negative qualities than the other schools, +Adam picked B. + +Studies show that when deciding which parent should receive sole custody of a child, juries focus on information that makes one parent seem better than the other. But when deciding which parent should be +denied custody, juries focus on information that makes one parent seem inferior to the other. This means that if one parent has average economic, social and emotional features and the other parent more +striking positive and negative features, we will both choose and reject the same parent. This means that we often both choose and reject options that are of a more striking or complex nature over average +ones. + +John's mother was concentrating on talking on her cell phone so she didn't see the other car coming. + +We don't see much of what passes our eyes when we are focused on something else. We only see what we focus our attention on. Sometimes we don't see what is right in front of us. One study showed that a few +experienced pilots trying to land a plane in a flight simulator were so concentrated on the flight information display, they didn't see that a second plane was blocking their runway. Until it was too late to +avoid a collision. + +Keep in mind + +• Look for alternative explanations. + +79 + +• Consider missing information. Know what you want to achieve. + +• Compare both positive and negative characteristics. + +REc1PROCATION + +There is no duty more indispensable than that of returning a kindness. All men distrust one forgetful of a benefit. + +Marcus Tullius Cicero (Roman statesman and writer, 106-43 BC) + +In return for his loyalty to the CEO, John received a promotion. + +We tend to repay in kind what others have done for us - good or bad. + +Do you return Christmas cards? In one study a researcher sent out cards to strangers. Dozens of people sent back cards, even though they'd never heard of the person. Whenever someone does something for us we +want to do something back. No wonder companies use free trials and send out free samples. A gift with our name on it is hard not to reciprocate. + +'1 praised him for a job well done, and I received a motivated employee. " + +'1 told him about his mistake, and he became hostile towards me. " + +We respond the same way as we are treated. If we are unfair to others, people are unfair back. If people trust us, we tend to trust them. If people criticize us, we criticize them back. If people we don't +like do us a favor or an uninvited favor, we reciprocate anyway. + +Warren Buffett tells us how Berkshire treats management: + +Three quarters of our managers are independently wealthy. They don't need to get up and go to work at all. Most of them have tens and tens of million of dollars. So I've got to create or I've got to maintain +an environment where the thing they want to do most in the world is to go to work that day and the next day. And, I say to myself, "What would make me feel that way?" One way is to feel you are running your +own show. If I had people second guessing me all day, I would get sick of it. I would say, "What the hell do I need this for?" And, that's exactly the way our managers would feel if I went around +second-guessing them or telling them how to run their business. + +A woman in Houston caught her husband and his mistress in a hotel parking lot, and proceeded to run the husband down with her car. + +We reciprocate unfair behavior even if it costs us. Some examples are: ugly divorces that cost people large sums, trade retaliations, costly strikes in connection with union negotiations, sabotage by a +mistreated employee or failure to agree in legal nuisance cases. + +80 + +John is negotiating to buy a small business. The seller asks a higher price than john is prepared to pay, so he declines. The seller then makes a concession and reduces the price. We make a concession to +people who have first made a concession to us. Since John views the lower price as a concession, he feels a need to reciprocate and accepts the lower price. This price was what the seller wanted in the first +place. Contrast comparison is also involved - the seller's second request seems smaller and therefore much better. This method of making an exaggerated request and settling for a smaller one is often used in +negotiations. It also increases the chance that John will live up to the deal since he feels responsible for having "dictated" the final terms. + +The "that's-not-all" technique is related to reciprocal concessions and often used in infomercials. For example, a company presents a product at $49.00, and before the customer can respond, they add an +additional product "for free." + +Keep in mind + +• People don't want to feel indebted. We are disliked if we don't allow people to give back what we've given them. + +• A favor or gift is most effective when it is personal, significant, and unexpected. + +• Before you make concessions, think about what you want to achieve. + +• The American car manufacturer Henry Ford said: "If there is any one secret of success, it lies in the ability to get the other person's point ofview and see things from his angle as well as from your own." + +• Follow Confucius: "What you don't want yourself, don't do to others. Reward hostility with justice, and good deeds with good deeds." Give people what you want in return from them. Ask: Assuming others are +like me, how would I like to be treated if the roles were reversed? + +• Set the correct example. In Confucius words: "Example is better than law. For where the laws govern, the people are shameless in evading punishment. But where example governs, the people have a sense of +shame and improve." + +LIKING AND SOCIAL ACCEPTANCE + +The deepest principle in human nature is the craving to be appreciated. + +William James + +"john likes his colleague, Ted, because they share the same values and prefer the same type of suits. " + +We want to be liked and accepted. We believe, trust and agree with people we know and like. We do things for people we like. We like the people who like us + +81 + +(because we like to be liked.) And if we feel that a person likes us, we tend to like them back. + +What can people do to make us like them? We tend to like our kin and romantic partners and people who are similar to us in background, opinion, lifestyle, interest, attitude, looks, values, and belief. Also, +those who are physically attractive, popular, cooperative, or people we have positive associations with. We also like and trust anything familiar. + +Aristotle said: "Personal beauty is a greater recommendation than any letter of introduction." Studies show that we believe that physically attractive people have a more desirable personality than +average-looking or unattractive people. Experiments show that attractive criminals are seen as less aggressive and get a milder punishment than ugly criminals. But like the 6th Century Greek writer Aesop +wrote, "Appearances often are deceiving." + +'1 am a sucker far flattery. " + +We like people who compliment us - true or not - and make us feel special. To quote the British Prime Minister and novelist Benjamin Disraeli: "Talk to a man about himself and he will listen for hours." We +also like the people who give us what we are missing in life. + +"To get them to do business with me, I associate myself with powerfal friends and disassociate myself from losers. I also try to get introduced by someone of established credibility. " + +People believe we have the same personality as those we associate with. Credibility leads to trust. + +"We have a common enemy. By cooperating we both gain. " + +We like people who cooperate with us. How do we get people to cooperate? Create an external common threat or an opportunity for mutual gain. + +'1 believe she likes me, so I like her to. " + +We reciprocate the way others see us. If we perceive others dislike us, we tend to dislike them. + +"I won the respect and friendship of my opponent by asking him to do me a favor. " Asking a favor of someone is likely to increase that person's liking for us. Why? Because people want to be seen as +consistent with their behavior. Benjamin Franklin tells us about an old maxim: "He that has once done you a kindness + +82 + +will be more ready to do you another, than he whom you yourself have obliged." + +"Since I want to be accepted, I always focus on the way I appear to others. " + +We want to be socially accepted and not disliked or rejected. We have a strong desire for avoiding social disapproval, exclusion, humiliation, public shame and losing status. This contributes to conformity. +William James says: ''A man's Social Self is the recognition which he gets from his mates... No more fiendish punishment could be devised... than that one should be turned loose in society and remain +absolutely unnoticed by all the members thereo£" + +The French 17th Century writer Francois Due de la Rochefoucauld wrote: "We only confess our little faults to persuade people that we have no big ones." We adapt what we say and do to suit our audience and +create a desired impression. We behave like others do and don't speak the truth or openly question people for fear of the consequences. We don't want to be the person who stands out. This is one reason why +people who are overly concerned about what others think about them prefer to be around like-minded people. It's more comfortable than standing out and risking social disapproval. + +'1 don't like him because he is egoistic, defensive, always complains and has a bad temper." + +We don't learn from people we don't like and we don't want to be associated with them. The people we don't like are the ones we perceive as dissimilar to us, people we are in competition with, those we +perceive as threatening, or people that are self-absorbed, complaining, greedy, etc. We tend to dislike people who have been dehumanized - for example, people who have been described as evil or animals. + +Keep in mind + +• Concentrate on the issue and what you want to achieve. + +• Don't depend on the encouragement or criticism of others. Marcus Aurelius Antoninus said: "How much time he gains who does not look to see what his neighbor says or does or thinks." + +• Don't automatically mistake people's appearance for reality. It may be a social mask. + +• Social approval is an effective way to make people behave correctly. Why do people avoid certain actions? Because they are afraid of the social punishment these actions may cause. + +• Benjamin Franklin wrote: "Love your enemies, for they tell you your faults." + +83 + +Francois Due de la Rochefoucauld adds: "Our enemies' opinion of us comes closer to the truth than our own." + +SOCIAL PROOF + +If 40 million people say a foolish thing, it does not become a wise one. + +Somerset Maugham (British novelist, 1874-1965) + +"But everybody else is doing it." + +Do you rely on others for advice and actions? Most people do. In True Believer, American philosopher Eric Hoffer wrote, "When people are free to do as they please, they usually imitate each other." We are +social animals, influenced by what we see other people doing and believing. We believe that others know more than we do. + +We want what others want. Since everybody else wants it, we assume there has to be a reason. We avoid what others avoid. We imitate without thinking. Especially when many or similar people do it, when we are +uncertain, in an unfamiliar environment, in a crowd, lack knowledge, or if we suffer from stress or low self esteem. + +Sellers of fashion, books, movies, etc., know that if enough people like something, others will eventually follow. We trust testimonials from people that we see as similar to us. + +Warren Buffett says: ''As happens in Wall Street all too often, what the wise do in + +the beginning, fools do in the end." He tells an instructive story: + +This friend, who ran a property-casualty insurer, was explaining to his directors why he wanted to acquire a certain life insurance company. After droning rather unpersuasively through the economics and +strategic rationale for the acquisition, he abruptly abandoned the script. With an impish look, he simply said: "Aw, fellas, all the other kids have one." + +'1 don't understand why they don't listen to me," said the CEO ofTransCorp. When we are uncertain, we are most likely to follow what people similar to us do. The CEO would therefore be more likely to have his +message heard ifhe used a spokesperson who already supported the CEO's ideas and who the audience saw as similar to themselves, such as a colleague. + +john's stockbroker recommends the same stock as other brokers. When john asked him why, he replied '1'd rather be wrong in a group than right by myself" + +We feel more comfortable as part of a majority. It acts as a protection from criticism. If we are wrong and everybody else is too, we get less blame. To quote + +84 + +J.M. Keynes: "Worldly wisdom teaches that it is better for reputation to fail conventionally than to succeed unconventionally." Warren Buffett adds: + +Most managers have very little incentive to make the intelligent-but-with-some-chance of-looking-like-an-idiot decision. Their personal gain/loss ratio is all too obvious: if an unconventional decision works +out well, they get a pat on the back and, if it works out poorly, they get a pink slip. (Failing conventionally is the route to go; as a group, lemmings may have a rotten image, but no individual lemming has +ever received bad press.) + +john invested in an exclusive oil project since a group of sophisticated, wealthy investors were involved. They promised that he would quadruple his money in one year. A year later, he'd lost it all. + +Former chairman of the U.S. Securities and Exchange Commission, Arthur Levitt, Jr. says, "If you are dumb enough to invest based on a lavatory wall, you deserve to lose money." + +In the early 1900s, Italian immigrant Charles Ponzi, took investors for $10 million by promising 40% returns on International Postal Reply Coupons. What he didn't tell newer investors was that their money was +being used to pay off earlier investors. In the end, the house of cards collapsed. + +In the Foundation for New Era Philanthropy, some of the U.S.'s leading charities and donors believed they could double their money in six months. New Era used contributions from one group to pay off another - +until there was no money left. New Era was a $350 million Ponzi Scheme. Charles Munger says, "Grown-up people actually believed that there was a tooth fairy out there that would double their money in six +months provided they agreed to give it to charity." + +Blindly following the lead of others can have dangerous consequences. + +"Oh my God, he stabbed me. Please help me!" + +We have a tendency to not act in situations where we are uncertain if there is danger and when we don't feel individual responsibility. Also when we want to avoid embarrassment and when we're among strangers. +The more people, the more reduced we see our own responsibility. + +Just after 3 a.m., March 13, 1964 in New York City, Catherine Genovese, a 28-year old woman, was stabbed to death as she returned from her job. 38 people witnessed at least one of her killer's three attacks +from the safety of their apartment windows for 25 minutes without calling the police.. + +Why didn't the neighbors help? Were they indifferent? Frightened? Why should they be afraid of calling the police from the safety of their own homes? A + +85 + +pair of psychology professors found the answer. No one had helped [3mjust [0mbecause thirty-eight witnesses were present. A bystander to an emergency is unlikely to help when there are other people around. Why? +They saw two reasons for this. + +First, we must interpret an event as an emergency. When we are uncertain, we have a tendency to look at people around us to see how they react. If others don't react, we interpret that as evidence that it is +not an emergency, and we therefore don't react. We don't want to be the ones that stand out in a crowd and risk embarrassment for acting in a non-emergency situation. But here comes the problem. If each +person reasons the same way, everyone draws the same conclusion. "Since nobody is concerned, nothing is wrong. It can't bean emergency." This is called pluralistic ignorance. + +The second reason is called diffusion of responsibility. The more people there are, the less personal responsibility we feel. We often rationalize by saying, "Someone else probably called the police. "If we +all think that way, no one will help. The more people we see around us, the less likely we are to help. We can't force people to help. If we punish people for not helping in an emergency, we will only create +an incentive for people to avoid the punishment by not getting involved. + +This will cause them to interpret a situation as a non-emergency. + +So, how should we act if we are involved in an accident in a public place and need help? We should be specific. "You there, in the blue shirt. This is an emergency. Please help me!" + +The board members ofTransCorp were asked if they had any questions. They looked around at the other members. All appeared confident. '/1m I the only one confased?" wondered John and kept quiet. + +"Since no one disagrees, my idea seems to have everyone's support,"the CEO said. + +If we believe that we are the only one who doesn't understand, we may keep quiet. Speaking up may lead to embarrassment. Group pressure may contribute to our silence. + +Sometimes mutual friendship and loyalty override our motivation to seek alternative courses of action. This type of group thinking has been found to be a factor in many historical events including the Bay of +Pigs invasion, the Vietnam War and Pearl Harbor. + +In the late economist Peter F. Drucker's The Effective Executive, the former + +chairman of General Motors, Alfred P. Sloan, Jr., is reported to have said at the dosing of a management meeting: "Gentlemen, I take it we are all in complete agreement on the decision here". Everyone around +the table nodded assent. "Then," continued Mr. Sloan, "I propose we postpone further discussion of this + +86 + +matter to give ourselves time to develop disagreement and perhaps gain some understanding of what the decision is all about." + +John attended a meeting where an investment proposal promising a 200% return was presented All 30 people present at the meeting invested and all lost money. + +How could 30 smart individuals be fooled? Some basic math would have told them that the project was doomed to fail. Each individual automatically assumed that the other 29 individuals present at the meeting +had evaluated the proposal. If there was something bad, someone else would have said so. "And since they invest, I invest." It turned out that no one had taken the time to read through the proposal. + +"I flattered them and made them feel special. I gave them purpose and hope, and they ate out of my hand " + +In a group we are easily seduced because of our need for social acceptance. The French social psychologist Gustave Le Bon said in The Crowd, "The masses have never thirsted after truth. They turn aside from +evidence that is not to their taste, preferring to deify error, if error seduce them. Whoever can supply them with illusions is easily their master; whoever attempts to destroy their illusions is always their +victim." + +German-Swiss philosopher Friedrich Nietzsche said: "Madness is a rare thing in individuals - but in groups, parties, peoples, and ages it is the rule." In a group, we feel anonymous, which reduces our +feelings of responsibility. We can't be blamed. This can lead to overconfident, risky behavior. We may also become impulsive and destructive. Especially in situations of severe stress. Benjamin Franklin said: +"A mob has heads enough but no brains." + +Imitation, obedience to authority, and the fear of being different are forces that drive crowds. Groups don't encourage differences of opinion. If a member of the group disagrees, he may be seen as disloyal. +Unanimity is better than independent thought. Individuals in the group reinforce each other into believing that they collectively are right. They focus on favorable consequences and ignore the downside. + +Is the tendency for imitating the group so strong it can make people commit collective suicide? + +In 1978, 913 followers of the cult leader Jim Jones and his People's Temple organization died during a mass suicide and murder in a place called Jonestown in Guyana, South America. Among the dead: more than +270 children. Why? + +The People's Temple started in San Francisco and moved to Guyana in 1977. + +87 + +Armed guards surrounded the settlement in Jonestown, food was scarce, and the members of the cult were forced to work long hours and follow strict codes of behavior. Cult leader Jim Jones committed his +followers one step at a time. He controlled the information, the rewards, and the punishment. In 1978, an American congressman and three others went on a fact-finding mission to Jonestown and were murdered. +Jim Jones thought that he would be implicated in the killings and that the isolation ofJonestown would result in the end of the cult. So he gathered the community to participate in an act of mass suicide by +drinking a fruit drink mixed with poison. + +Psychology Professor Robert Cialdini writes: + +His Uones] masterstroke was the decision to move the People's Temple community from its roots in urban San Francisco to the remoteness of equatorial South America, where the conditions of uncertainty and +exclusive similarity would make the principle of social proof operate for him as perhaps nowhere else. + +Cialdini continues: "In a country like Guyana, there were no similar others for a Jonestown resident but the people of Jonestown itself." + +Keep in mind + +The 19th Century American poet Ralph Waldo Emerson said: "It is easy in the world to live after the world's opinion; it is easy in solitude to live after our own; but the great man is he who in the midst of +the crowd keeps with perfect sweetness the independence of solitude." What is popular is not always right. If you don't like what other people are doing, don't do it. Warren Buffett says: "We derive no +comfort because important people, vocal people, or great numbers of people agree with us. Nor do we derive comfort if they don't." + +Disregard what others are doing and think for yourself. Ask: Does this make sense? Remember the advice from Benjamin Graham, the dean of financial analysis: + +Have the courage of your knowledge and experience. If you have formed a conclusion from the facts and if you know your judgment is sound, act on it - even though others may hesitate or differ. (You are +neither right nor wrong because the crowd disagrees with you. You are right because your data and reasoning are right.) + +A lot of our children's personality traits and habits are shaped outside the home. Children learn from their friends what is acceptable or not so make sure + +88 + +the right "peer group" surrounds them. + +When part of a group, remember that the participants may have different goals, information, and interpretations. Seek out alternative points ofview and encourage people to openly disagree. Appoint someone in +the group to question things and point out risks and pitfalls. Use ballots to reduce the risk of social pressure. + +Make people responsible for their actions. Remember though, when all are accountable, no one is accountable. + +AUTHORITY + +In questions of science, the authority ofa thousand is not worth the humble reasoning of a single individual + +Galileo Galilei (Italian astronomer and physicist, 1564-1642) + +After the break-in at john's office, he said: "Of course, I believed he was a security guard, since he had a uniform. " + +We tend to obey an authority, especially when we are uncertain, supervised, or when people around us are doing the same. We are most easily influenced by credible authorities, those we see as both +knowledgeable and trustworthy. + +'1 read it in the New England journal of Medicine, so it must be correct. " + +Names and reputation influence us. And symbols of power or status like titles, possessions, rank, uniforms, or a nice suit and tie. For example, in one study 22 hospital nurses got a telephone call from an +unknown physician and were ordered to administer an obvious overdose of an unauthorized drug. All but one nurse obeyed. + +Another example is when advertisers use famous people to endorse their products. But being famous doesn't give people special expertise. + +"The more I didn't understand, the more I believed the expert. " + +Experts are sometimes more convincing when we don't understand them. Sometimes we are too impressed by something that sounds clever. For example, some people buy into investments just because they don't +understand them. They assume it must be something unique. As Warren Buffett says, "Techniques shrouded in mystery clearly have value to the purveyor of investment advice. After all, what witch doctor has ever +achieved fame and fortune by simply advising 'Take two aspirins'?" + +89 + +'1 was only following orders. " + +Blind obedience is sometimes a way to rationalize dumb actions. + +'1 believed he was making a mistake, but Ididn't dare tell him. After all, heis the expert. " A study involving airline pilots cited conflict avoidance as a contributing factor to crashes. Officers are +reluctant to disagree with the authority of pilots. For example, in a crash of a DC-8 in 1978, the flight engineer told the captain that they were running out of fuel. The captain dismissed the warning and +the plane crashed. + +In 1997, a female police officer in Scotland was assigned to a murder investigation. Forensic investigators later found her thumbprint in the house where the murder victim was found. But the woman insisted, +under oath, she had never been inside the house. Four experts from the Scottish Criminal Record Office said that the print was hers. She was suspended and accused of perjury. Subsequent events showed that the +fingerprint was neither hers nor from a thumb, but from a forefinger. Thus, experts make mistakes. + +Authority is so powerful that we may cause pain to other people to comply. The British novelist and scientist Charles Percy Snow said in The Two Cultures and the Scientific Revolution: "When you think of the +long and gloomy history of man, you will find more hideous crimes have been committed in the name of obedience than have ever been committed in the name of rebellion." + +In one experiment at Yale University, Psychology Professor Stanley Milgram tricked people by posing as an authority and caused normal people to impose what they had every reason to believe was intense pain to +other people. The participants in the experiment were instructed to shock another person if they answered a question wrong. No real pain was delivered during the experiment. But it showed that when we are +given orders from what we believe to be a legitimate authority, we obey even if the result is that we end up hurting others. In later studies Milgram showed that obedience was maximized by first observing +peers obey but dramatically reduced when peers rebelled, or when the victim acted like a masochist asking to be shocked. Milgram said in Obedience to Authority: "It is psychologically easy to ignore +responsibility when one is only an immediate link in a chain of evil action." + +Keep in mind + +Evaluate the truth of a statement on the basis of its underlying facts, without regard to the authority's personal qualities or social status. + +Anyone can call themselves an expert. Separate between real and false experts. + +An authority may have an interest in persuading you to believe something that + +90 + +is in their interest. Always consider reliability, credibility, sensibility and bias. To insure their trustworthiness, authorities often mention weaknesses before strengths and provide information that seems +contrary to their interests. This technique is often used by salesmen and negotiators. + +SENSEMAKING + +"We understand life backwards but live it forwards. " + +Soren Aabye Kierkegaard (Danish philosopher and theologian, 1813-1855) + +"There has to be a reason!" + +The 19th Century playwright and poet Oscar Wilde said: "The public have an insatiable curiosity to know everything, except what is worth knowing." + +We don't like uncertainty. We have a need to understand and make sense of events. We refuse to accept the unknown. We don't like unpredictability and meaninglessness. We therefore seek explanations for why +things happen. Especially if they are novel, puzzling or frightening. By finding patterns and causal relationships we get comfort and learn for the future + +TransCorp hired a team of people to find out why the new product failed. + +What did we do wrong in this case? There is a difference between: "Why did it happen?" and "What can cause this to happen?" The team looked for the specific factors that caused their new product to fail. They +may learn more from asking: Why do new products fail? What general reasons are there? What key factors influence product failures? + +"It is easy to be wise after the event, "says Sherlock Holmes in The Problem of Thor Bridge. We read the present into the past. After an event, we know how things turned out. When trying to make sense of what +has happened, we construct a plausible story or explanation that fits the outcome. But there are many ways an event or behavior can later be understood. There may be many contributing factors that fit the +outcome, chance may be involved, or our guessed causes may also be consistent with other outcomes, including the opposite or prevention of the outcome. Ask: Could our explanation of the event help us predict +future similar events? + +This is the danger of relying on case-based stories. Stories may be selected to prove something and may give us a delusional sense of clarity. Knowledge about outcomes may also cast some doubt on +reconstructions of historical events (given that the historian was not there). History is often composed of various events all coming together. + +91 + +History is also explained by what has survived into the historian's present. Not all sources survive. Not everything gets recorded, memories are unreliable, evidence may be destroyed or deliberately ignored, +and some things may be too embarrassing to mention. When Oliver Cromwell's portrait was painted, he told the artist. "Remark all these roughnesses, pimples, warts, and everything as you see me, otherwise I +will never pay a farthing for it." + +We also seem to have a tendency for romanticizing past achievements. John Waller, Lecturer in the History of Medicine at the University of Melbourne, says on scientific discoveries in Einstein's Luck: "Many +biographies seem to have been written to glorify idols, ancestors, disciplines, or even the nations in which the scientists lived and worked." + +"Why was he so stupid? How could hehavedone that? It was obvious it would happen. " The 19th Century Russian writer Fyodor Dostoevsky said: "Everything seems stupid when it fails." In hindsight, everything +seems obvious. But we should look at earlier decisions in the context of their own time. Perhaps the actions made sense at the time. We don't know what uncertainties, conditions, or situational factors faced +the decision-maker. Good decision-making can lead to bad outcomes and vice versa. If we believe that we predicted the past better than we did, we may also believe that we can predict the future better than we +can. The Romanian dramatist Eugene Ionesco said: "You can only predict things after they've happened." + +"The oil price will stabilize at $60." + +How do they know that? In the Cato journal Distinguished Professor Deirdre McCloskey said: "If you desire a ride to Baghdad, here is a magic carpet; if you desire your enemy dead, here is a magic doll; if you +desire unlimited riches, here is a forecast of interest rates." We like it when people tell us what the future will look like. It reduces uncertainty. It doesn't matter that no once can predict the future, we +willingly pay for the existence of future-tellers. + +Charles Munger says: ''Around here I would say that if our predictions have been a little better than other people's, it's because we've tried to make fewer of them." + +'1t couldn't have happened by chance. There must be a reason. " + +We see faces in inkblots and patterns in the movements of stocks. We find meaning in coincidences. We underestimate the influence of chance. We want to find reasons for all kind of events - random or not. And +if we don't find any, we construct them. We then choose the things that fit an intended pattern and + +92 + +ignore the rest. Studies show that we even try to figure out a pattern when we are told a process is random. + +In one experiment, two lights were set up and flashed in a random sequence. Before each trial, research subjects tried to guess which of the two lights would appear. The studies showed that they tried to +match the frequency of previous occurrences in their guesses. Similar studies showed that rats or pigeons instead chose + +the alternative that came up most frequently. If we assume that a red light occurs + +with a frequency of 80% and a green light with a frequency of 20%, we should bet on the most likely outcome every time: red. We then guess right 80% of the time. Trying to match the frequency only gave the +right answer 68% of the time. + +An example of our tendency to see patterns that aren't there is when we use unreliable tests for evaluating people. A test is reliable if it gives about the same result when repeated assuming the test +measures a characteristic that is stable over time. A test is valid if it accurately measures what it claims to measure. Take the Rorschach inkblot test as an example. One problem is that the test classifies +a large percentage of normal individuals as psychologically disordered. Can we evaluate personality by studying how an individual perceives a series of inkblots? Interviewers can read into it whatever they +wish to see. This test is still used today although research has shown that it allows for countless interpretations and has no predictive value. + +"Once upon a time in the land of .. " + +We are quick to draw conclusions. Author and entrepreneur Seth Godin tells a true story in his bookAllMarketersAre Liars. In the 1980s, some businessmen bought some branded stereo speakers and packed them +into a truck. They parked the truck behind a dorm at Harvard and started whispering "Pssst... Hey! You wanna buy some speakers?" They never said that the speakers were stolen but passersby assumed they were. +They therefore had to be a bargain. The businessmen sold out in no time. Even if the speakers cost a little more than they did in the local store. + +We love stories and story-telling. Good stories and drama get our attention. They give meaning to events. We rationalize decisions and justify choices by telling ourselves comforting stories. We use stories +to understand, remember and make sense of events. But sometimes we have a hard time separating a true story from a false one. After an event a story is created so that the event makes sense. Remember that a +story can have many possible beginnings (and endings). + +Keep in mind + +Look for alternative explanations and what normally happens. Think about general reasons. + +93 + +Consider how other possible outcomes might have happened. Don't underestimate chance. + +In hindsight, everything seems obvious. If we look forward, there are many + +possible outcomes. + +REASON-RESPECTING + +"Please would you tell me," said Alice, a little timidly, "why your cat grins like that?" "It's a Cheshire Cat,"said the Duchess, "and that's why. " + +Lewis Carroll (British mathematician and writer, 1832-1898, from Through the Looking Glass) + +Our need for making sense makes us even believe in nonsense. + +In one experiment a social psychologist asked people standing in line to use a copying machine if she could go in front of them, "Excuse me, I have 5 pages. May I use the Xerox machine because I have to make +some copies?"Nearly all agreed. + +When people ask us for a favor we are more likely to comply if they give us a reason - even if we don't understand the reason or it is wrong. Often it isn't the reason itself that is important, but the way +the reason is phrased. Sometimes the word "because," without a sensible reason, is all that matters. We want explanations and the word "because" imply an explanation. + +Carl Braun, the creator of CF Braun Engineering Company, understood the importance of telling people "why." Charles Munger tells us the story: + +His rule for all the Braun Company's communications was called the five W's - you had to tell who was going to do what, where, when and why. And if you wrote a letter or directive in the Braun Company telling +somebody to do something, and you didn't tell him why, you could get fired. In fact, you would get fired if you did it twice. + +You might ask why that is so important? Well, again that's a rule of psychology. Just as you think better if you array knowledge on a bunch of models that are basically answers to the question, why, why, why, +if you always tell people why, they'll understand it better, they'll consider it more important, and they'll be more likely to comply. Even if they don't understand your reason, they'll be more likely to +comply. + +So there's an iron rule that just as you want to start getting worldly wisdom by asking why, why, why in communicating with other people about everything, you want to include why, why, why. + +"Why should we do this? Why should we do it this way?" ''Because this is how we always have done it. " + +94 + +We should not only give people reasons for what to do but should also encourage flexibility. Ask them to question procedures and whether what appear to be self evident truths are really good for the business. +Ask why, ask why, and ask why again. The third why often gets down to the real issue. + +"How can I use what I don't understand?" + +Understanding reasons is an important factor in learning. To learn, remember, organize, and use ideas, we must understand the "why" and "how." There's no use memorizing what we don't understand. If we don't +understand the meaning of an idea, we don't use it. What we don't use, we forget. We also need to be motivated to learn. And we can't be motivated if we don't understand why we need to learn something. We +need to see its practical use. + +Understanding is about the ability of seeing patterns - how ideas and things relate and hang together. Knowledge that can be used in a variety of situations. + +Our brains favor the concrete and practical over the abstract and theoretical. We are especially good at remembering images and spatial information. We therefore learn better if the use of ideas and patterns +are illustrated through pictures and simple, clear and vivid real-life stories. Stories on what works and what doesn't work increase our ability to retain what we've learned. + +Aristotle said: "For the things we have to learn before we can do them, we learn by doing them." This means we need to practice what we have learnt in various situations. + +We also need an organizing framework in order to better retrieve and use knowledge. Charles Munger adds: "You can't really know anything if you just remember isolated facts and try and bang 'em back. If the +facts don't hang together on a latticework of theory, you don't have them in a usable form." + +Keep in mind + +People can't be persuaded by what they don't understand. We underestimate the importance of giving people a reason. It is often easier to get people to change with a well-explained reason backed by solid +evidence. Tell them so they understand why a specific action is needed, what the expected objective is, and why you think the action is right. + +Of course, this doesn't work in every case. Sometimes you don't change people's opinions by showering them with logic. In Jonathan Swift's words: "You cannot reason a person out of a position he did not +reason himself into in the first place." Aristotle adds: "For argument based on knowledge implies instruction, and there are people whom one cannot instruct." Sometimes it is + +95 + +better to appeal to emotions than to reason since people are more moved by what they feel than by what they understand. + +BELIEVE FIRST AND DOUBT LATER + +"Our new product is very good for you for the following reasons. .. " + +We start assuming that the product is good for us and look for evidence that confirms it. We believe people when they give us reasons. We believe that people are telling us the truth, even when they are not. + +We are not natural skeptics. We find it easy to believe, but difficult to doubt. Doubting is active and takes effort. Bertrand Russell said: "Believing seems the most mental thing we do." Why? Because we have +to believe in order to understand. + +Studies show that in order to understand some information we must first accept it as true. The 17th Century philosopher Benedictus de Spinoza argued that understanding and believing are simply two different +words for the same mental process. We first believe all information we understand and only afterwards and with effort do we evaluate, and if necessary, un-believe it. Studies show that Spinoza was right. We +automatically and effortlessly believe what we see and hear and only afterwards (sometimes) with effort do we doubt and ask questions. Psychology Professor Daniel Gilbert says in his study How Mentals Systems +Believe: "Having comprehended and accepted an idea, Spinoza considered persons entirely free either to unaccept or to certify it." + +Studies also show that the more distracted or pressured we are (and therefore prevented from thinking things through), the more likely we believe in something we normally would find dubious. Whether we think +things through or not depends on our motivation and ability. + +Believing something that is false may sometimes come with a benefit. For example, studies show that if students are told they are above average on a subject, they will do better. + +How successful are people at deceiving us? + +Can we catch a liar? We don't seem to be good at telling a truth from a lie. Studies show that people - even professionals - are slightly better than chance at distinguishing truths from lies. We seem to be +better at judging when people are telling the truth than when they are telling a lie. Michel de Montaigne said: "If falsehood, like truth, had only one face, we would be in better shape. For we would take as +certain the opposite of what the liar said. But the reverse of truth has a hundred thousand shapes and a limitless field." + +96 + +Keep in mind + +When dealing with important issues think things through and avoid distraction. + +MEMORY LIMITATIONS + +Everyone complains of his memory, and no one complains of his judgment. + +Francois Due de la Rochefoucauld + +Our memory is selective. We remember certain things and distort or forget others. Every time we recall an event, we reconstruct our memories. We only remember fragments of our real past experiences. Fragments +influenced by what we have learned, our experiences, beliefs, mood, expectations, stress, and biases. Certain experiences create strong feelings and are therefore more memorable than others. Dramatic or +fearful experiences or events stick in our memories. Emotional events are better remembered than unemotional ones. That is why we learn better if information is tied to a vivid story. Learning is also tied to +mood. + +We learn better in a positive mood. That is why teaching should be performed in a way that creates powerful positive emotions among students. + +Psychology Professor Daniel Schacter, proposes in The Seven Sins of Memory + +that our memory's malfunctions can be divided into seven "sins." + +(1) Our memory weakens and we lose memory over time. (2) We are preoccupied with distracting issues and don't focus attention on what we need to remember. (3) We search for information that we may be +desperately trying to retrieve - something we know that we know - but are blocked. (4) We assign memory to the wrong source. (5) Memories are implanted as a result of leading questions, comments, or +suggestions when we try to call up a past experience. (6) Our present knowledge influences how we remember our pasts. We often edit or entirely rewrite our previous experiences. (7) We recall disturbing +events that we would prefer to eliminate from our minds altogether: remembering what we cannot forget, even though we wish that we could. + +Individuals remember the same things differently. We remember events that never happened or assign what happened to the wrong place, time or person. Studies show that memories of emotional experiences are +often different from what actually happened. We misinterpret what we saw. That is why there are variations in eyewitness accounts. Many cases show that eyewitness identification evidence has been a +significant cause of wrongful convictions. Especially the accuracy of eyewitness identification of strangers. + +97 + +"/ [3mnever forget a face. [0m" + +Australian psychologist Donald Thomson appeared on a live TV debate about the unreliability of eyewitness testimony. He was later picked up by the police, placed in a lineup, and identified by a victim as the +man who had raped her. But Thomson has an airtight alibi. The rape had occurred while he was on TY. It later turned out that the rapist had attacked the woman as she was watching the very show on which +Thomson had appeared. + +Studies show that we remember a face but wrongly remember the time and place we saw it. Leading and suggestive questions can cause misidentification, and influence by information obtained after the event. +Studies show that it is easy get a witness to believe they saw something when they didn't. Merely let some time pass between their observation and the questioning. Then give them false or emotional +information about the event. Psychology Professor Elisabeth Loftus' work has shown that people can be led to remember rather familiar and common experiences, even when they had not happened. For example, her +studies show that people can believe that a childhood experience had happened when it never happened. + +Studies show that jurors believe witnesses even when they are later shown to have made an incorrect identification. Eyewitnesses can be highly inaccurate but appear confident. The more confident people are +when they appear as witnesses, the more believable the jurors will find them. The more detailed their memory of a situation is, the more the jurors trust them. Testimonial evidence is vivid and therefore more +believable. + +Is a child witness always to be trusted in a courtroom? + +Can a psychologist who interviews a troubled child falsely implant the idea that a bad event happened to them? + +Childhood memories are unreliable and influenced by fantasies and suggestions. Experiments have shown how normal children behave in response to suggestions. Implanted false stories can have a huge impact. +Children can actually believe an event that never happened or produce false narratives for the event. Over time, their stories may become elaborate and filled with vivid details, making them more believable. + +Keep in mind + +Keep records of important events. + +98 + +Do-SOMETHING SYNDROME + +I have often said that the sole cause of man's unhappiness is that he does not know how to sit quietly in his room. + +Blaise Pascal + +When John asked why the company continued making acquisitions when so many of them turned sour, the CEO replied: "All my colleagues do deals like this. Plus how can I keep my job and all my perks if I don't +keep busy?" + +Blaise Pascal said: "Man finds nothing so intolerable as to be in a state of complete rest, without passions, without occupation, without diversion, without effort." We sometimes act because we can't sit +still. We feel bored, impatient, threatened or pressured or we simply desire excitement and stimulation. We act without a sensible reason. It seems easier to explain doing something than actively doing +nothing. + +Warren Buffett tells why CEOs like acquisitions: + +The sad fact is that most major acquisitions display an egregious imbalance: They are a bonanza for the shareholders of the acquiree; they increase the income and status of the acquirer's management; and they +are a honey pot for the investment bankers and other professionals on both sides... often the CEO asks a strategic planning staff, consultants or investment bankers whether an acquisition or two might make +sense. That's like asking your interior decorator whether you need a $50,000 rug. + +The acquisition problem is often compounded by a biological bias: Many CEO's attain their positions in part because they possess an abundance of animal spirits and ego. If an executive is heavily endowed with +these qualities - which, it should be acknowledged, sometimes have their advantages - they won't disappear when he reaches the top. When such a CEO is encouraged by his advisors to make deals, he responds +much as would a teenage boy who is encouraged by his father to have a normal sex life. It's not a push he needs. + +Warren Buffett also provides an example from the insurance world on why it is more important to do what is right than to simply do something: + +We hear a great many insurance managers talk about being willing to reduce volume in order to underwrite profitably, but we find that very few actually do so. Phil Liesche [manager National Indemnity +Company's insurance operation] is an exception: if business makes sense, he writes it; if it doesn't, he rejects it. It is our policy not to lay off people because of the large fluctuations in work load +produced by such voluntary volume changes. We would rather have some slack in the organization from time to + +99 + +time than keep everyone terribly busy writing business on which we are going to lose money. + +Continuous reorganization may be dangerous. The Roman satirist Petronius Arbiter said in the 1st Century: "We trained hard, but it seemed that every time we were beginning to form into teams we would be +reorganized. I was to learn later in life that we tend to meet any new situation by reorganizing, and what a wonderful method it can be for creating the illusion of progress while producing confusion, +inefficiency, and demoralization." + +Keep in mind + +The 19th Century American writer Henry David Thoreau said: "It is not enough to be busy; so are the ants. The question is: What are we busy about?" Don't confuse activity with results. There is no reason to +do a good job with something you shouldn't do in the first place. + +Charles Munger says, "We've got great flexibility and a certain discipline in terms of not doing some foolish thing just to be active - discipline in avoiding just doing any damn thing just because you can't +stand inactivity." + +What do you want to accomplish? As Warren Buffett says, "There's no use running if you're on the wrong road." + +SAY-SOMETHING SYNDROME + +Wise men talk because they have something to say; fools, because they have to say something. + +Plato + +'1 am a big shot; people expect me to comment on all kind of things." + +People tend to speak even if they have nothing to contribute. Mark Twain wrote: + +"If you have nothing to say, say nothing." + +Why do we always need to give an answer? Isn't it better to say, "I don't know?" Greek philosopher Socrates said that awareness of ignorance is the beginning of wisdom. + +Keep in mind + +Wisdom is a two-headed beast. Roman dramatist Publilius Syrus wrote in 1st Century BC: "I have often regretted my speech, never my silence." + +Benjamin Franklin said: "He that would live in peace and at ease, must not speak all he knows, nor judge all he sees." + +100 + +25. EMOTIONS + +The heart has its reasons of which reason itself knows nothing. + +- Blaise Pascal + +'1 got married in the heat of passion. Sorry dad,"John's daughter said + +Francis Bacon said: "The guilt of Senses is of two sorts, either it destitutes us, or else deceives us." Emotions come before reason. Often when we make a decision our feelings take over. We hear bad news +first. Under the influence of intense emotions we sometimes make hasty judgments and choices we would normally never do. For example, we buy things we can't afford, we have unprotected sex, we overeat, and +use drugs. Studies also show that when we are in a state of more rational calm, we underestimate how we will feel and act when we experience intense emotions. + +'1 had a really bad day today,"said Mary, "So Tm going shopping now. " + +One study tried to find out how disgust and sadness influenced economic decisions. All participants in the study watched a movie immediately before conducting financial transactions. Some watched a sad movie. +Others a disgusting movie and a third group an emotionally neutral movie. Participants insisted that their feelings didn't affect what they were willing to pay for something or what price they were willing to +accept. The study showed otherwise. Disgust reduced their selling and buying prices. Sadness cut their selling prices but raised their buying prices. + +We saw under loss aversion and deprival that we put a higher value on things we already own than on the same things if we don't own them. Sadness reverses this effect, making us willing to accept less money +to sell something that we would pay for the same thing. + +This means, that when we feel sad, which often reflects helplessness and loss, we may want to change our circumstances so we feel better. This may cause us to overpay for something or buy things we don't +need. That is why Mary went on a shopping spree. She needed some retail therapy. When we feel disgust we may be reluctant to buy anything new unless we find it is a real bargain. When we feel sadness or +disgust we may want to get rid of things we have and sell them for less than what they are worth. + +'1t doesn't matter how large the problem is. It doesn't feel good " + +Risk is a feeling. We automatically judge how good or bad a stimulus is based on how we feel about it. When something produces strong emotions, we overweigh + +101 + +its consequences and underweigh its chance of happening. We associate gains with great feelings. For example, studies show that our feelings toward winning the lottery are the same whether the chance of +winning is one in 10 million or one in 10,000. + +John is buying a new sports car. He is all excited. But how will he feel one year from now? + +We expect that if good or bad things happen to us in the future, they will make us feel better or worse much longer and more intensively than they actually turn out to be. So John's new car will probably be +less exciting than John expects. Neither will it excite John as long as he expected. Why? Because we tend to adapt to most good and bad things and circumstances and make them ordinary (adaptation is not +inevitable - individual differences and conditions matter and some major life events produce long lasting or enduring changes in life satisfaction). Our feelings are also influenced by so many other things +and people than the specific future event itself. Furthermore, the comparisons we make when we think about our future feelings are often not the comparisons we make when we experience the event. + +What about if we instead use our past good experiences to decide what we want? Can we trust our memories to guide us? Memories can be deceptive. We also underestimate how our tastes and preferences will +change. The Roman poet Titus Lucretius Cams said: "As long as we do not have it, the object of our desire seems greater than anything else; as soon as we enjoy it, we long for something different with an +equal craving." + +What could we do instead? When we make big decisions, we could compare our expected feelings with those of people who have similar experiences today. In that sense, we are not as unique as we think we are. + +Keep in mind + +• Understand your emotions and their influence on your behavior. Ask: Is there a rational reason behind my action? + +• Remember the proverb: ''A wise man controls his temper. He knows that anger causes mistakes." + +• When we have just gone through an emotional experience, we should hold off on important decisions. + +• The benefits of cooling-off periods force us to think things through. + +102 + +26.STRESS + +You can't change the cards life has dealt you, but you can determine the way you'll play them. + +- Ty Boyd (American motivational speaker) + +Too much information, lack of predictability or control, too many choices, lack of sleep, social isolation, job status, crisis, catastrophes, fear, etc. cause stress. The less control we perceive we have over +our lives, the easier we fall victim to stress. The more stress we experience, the more we tend to make decisions that are short term. + +Everything our brain interprets as a threat influences our biology. Our ancestors didn't suffer less stress than we did. But their stress was different. They met dangers that demanded fast physical reactions. +Our stress is more social and psychological in nature. + +The fear of losing both her job and social position caused Mary to suffer constant headaches. + +Stress affects concentration and memory. Long-term stress exposure upsets the brain's chemical balance. Stress may cause high blood pressure, heart disease, diabetes, back and stomach problems, headache, and +depression. Studies show that when we feel stress the concentration of cortisol rises in the bloodstream. One effect of cortisol is to suppress the workings of our immune system. This makes us more vulnerable +to diseases. Stress also counteracts the production of insulin (the hormone that processes blood sugar), causing the process of repair to slow down. Studies show that emotional stress creates longer recovery +times in our bodies and may be more harmful to our health than non-emotional stress events like physical exercise. + +What happens when people are exposed to physical and mental exhaustion, confasion, physical pain, emotional tension or fear? + +Stress increases our suggestibility. Ivan Pavlov showed that animal behavior could be established or erased by exposing the animal to stress. For example, he could make a dog react aggressively to a caretaker +with whom the dog was once very loyal. The same can happen to people. All people have a certain level of tolerance to stress. Once it is passed, people begin to break down and what they earlier believed and +liked are easily changed. This can happen to prisoners of war. It has also been used to make religious and political conversions, and by police forces to elicit confessions. + +103 + +'1 have lost control over the situation. " + +The more we believe we are in control, the less vulnerable we are to the negative effects of stress. Studies show that people who perceive themselves to be in control over a stressful situation experience +less stress on their hearts and circulatory system. + +The status of our job matters. The Whitehall II study involving 17,000 civil servants showed that people with low perceived control over the work environment or people low in the organizational structure have +an increased risk of cardiovascular disease. Our cortisol levels rise in response to the degree other people order us about. As we climb the social hierarchy health status improves. In Genome, science writer +Dr. Matt Ridley comments on the Whitehall study: "Somebody in a low-grade job, such as a janitor, was nearly four times as likely to have a heart attack as a permanent secretary at the top of the heap." + +In another study researchers tried to find out the differences between business executives who became sick from exposure to high stress and those who didn't. They found that executives who stayed healthy had +a sense of commitment to work and families, felt in control, and had a positive attitude toward challenges. They saw challenges as part oflife and an opportunity for growth rather than as a threat. + +Warren Buffett says, "I have no stress whatsoever - zero. I get to do what I love to do every day. I'm surrounded by people that are terrific." He continues, ''All the businesses I run don't take 5% of my +time. We don't have regular staff meetings and the like. If you've got good businesses and the right managers, you don't need that sort of thing- and if you don't, they don't help." + +Keep in mind + +• Stress is neither good nor bad in itself. It depends on the situation and our interpretation. Stress can be controlled by our attitudes. The Austrian physician Dr. Hans Selye says in Stress without Distress +that it is not stress that harms us but distress. We need challenges. He continues, "Without stress, there would no life... Complete freedom from stress is death." + +• The 1st Century philosopher Epictetus said: "Happiness and freedom begin with a clear understanding of one principle: Some things are within our control, and some things are not. It is only after you have +faced up to this fundamental rule and learned to distinguish between what you can and can't control that inner tranquility and outer effectiveness become possible." + +If a problem can be solved, there is no need to worry. The thing to do is to correct it. If a situation can't be solved, we shouldn't worry about that either. We can't do anything about it. Mark Twain says: +"I've suffered a great many + +104 + +catastrophes in my life. Most of them never happened." Sometimes keeping ourselves busy with something else may cause us to stop worrying. + +PAIN, CHEMICALS AND DISEASES + +Pain upsets and destroys the nature of the person who feels it. + +-Aristotle + +'1can't think clearly because I am drunk. I don't care about the consequences if I act violent." + +We become confused when we are in pain, under the influence of chemicals or have a physical or mental illness. Physical and mental pain may cause fear, anger and stress. Chemical changes magnify the pain and +can cause depression. + +Drugs, stimulants (like nicotine, alcohol or coffee), and depressants distort our senses. + +MULTIPLE TENDENCIES + +When you get two or three of these psychological principles operating together, then you really get irrationality on a tremendous scale. + +- Charles Munger + +Charles Munger gives an illuminating example on the issue of stealing: + +A very significant fraction of the people in the world will steal if (A) it's very easy to do and, (B) there's practically no chance of being caught. And once they start stealing, the consistency principle +will soon combine with operant conditioning to make stealing habitual. So if you run a business where it's easy to steal because of your methods, you're working a great moral injury on the people who work for +you... + +It's very, very important to create human systems that are hard to cheat. Otherwise you're ruining your civilization because these big incentives will create incentive-caused bias and people will rationalize +that bad behavior is OK. + +Then, if somebody else does it, now you've got at least two psychological principles: incentive-caused bias plus social proof. Not only that, but you get Serpico effects: If enough people are profiting in a +general social climate of doing wrong, then they'll turn on you and become dangerous enemies if you try and blow the whistle. + +Frank Serpico became known after exposing corruption at the New York Police Department in the 1970s. When Frank Serpico entered the New York Police force in 1960, payoffs and kickbacks were rampant in the +department. + +105 + +When he refused to take money, his fellow officers saw him as a potential danger. Then he blew the whistle on them, and became their enemy. In a 1971 testimony before the Knapp commission, Serpico said: "I +hope that police officers in the future will not experience the same frustration and anxiety that I was subjected to for the past five years at the hands of my superiors because of my attempt to report +corruption ... We create an atmosphere in which the honest officer fears the dishonest officer, and not the other way around." + +john's acquisition experience caused him stress and cost TransCorp money. + +John said, "I was dissatisfied having done so little for TransCorp last year. All of the other guys made acquisitions. If I could find a good acquisition, maybe I could move up the ranks. I needed a +promotion. + +I found a good-looking business, and saw the possibility of making TransCorp a lot of money. The CEO of the business was a nice guy and we always met in their relaxing conference room. The asking price was +low in relation to past profits. I had experts telling me what a great company it was. I was presented entertaining information on new products. The investment banker did me a favor by bringing the deal and I +wanted to reciprocate. + +The banker told me that other people I admire would jump at the opportunity. I made a commitment to the financiers and told TransCorp's CEO about the deal. I committed myself publicly and felt a need to +follow-through. I concentrated my search on evidence that confirmed the greatness of the deal. I denied reality and thought nothing bad could happen. I didn't say what I thought for fear of social +disapproval. The CEO of the company I wanted to acquire continuously gave me good reasons to pursue the deal. The more effort I put into the deal, the more I felt I had to do it. I finally signed the papers. +When reality kicked in and the deal turned sour, I was in deep trouble. And so was TransCorp." + +'1 don't want to go against the CEO and risk losing my $250,000 directors fee." + +Is the board of directors an effective corrector to deal with CEO mediocrity? Charles Munger says: "The psychological nature of the board of directors system makes it an ideal system for causing people to +follow the lead of the CEO." + +A board may be a legal creation, but it is a social animal. Warren Buffett says: + +When people meet every couple of months and come from different parts of the country + +- and they have the normal social instincts - they don't like to have rump meetings or sort of talk behind people's backs. So it's very difficult in a group - particularly if it's a group + +106 + +like Charlie described where the directors' fees for a significant number of them are important to their well-being, and they'd love to be recommended for another board and add another $100,000 a year to +their income- for someone to lead a charge all of a sudden at a regular meeting or to try to arrange a rump meeting of some sort to say, "We think the guy at the head of the table is no good." + +So dealing with mediocrity- or, like I say, a notch above it - is a difficult problem if you're a board member. .. + +I've been on 19 boards. And I've never seen a director on any of the 19, where the director's fees were important to them, object to an acquisition proposal or a CEO's compensation. + +The CEO of TransCorp tells his board: "This is the decision, now let's start the discussion. " + +Apart from incentive-caused bias, liking and social approval, what are some other tendencies chat operate here? Authority - the CEO is the authority figure who directors tend to trust and obey. He may also +make it difficult for those who question him. Social proof - the CEO is doing dumb things but no one else is objecting so all directors collectively stay quiet - silence equals consent; illusions of the group +as invulnerable and group pressure (loyalty) may also contribute. Reciprocation - unwelcoming information is withheld since the CEO is raising the directors fees, giving them perks, caking them on trips or +letting chem use the corporate jet. Association and Persian Messenger Syndrome - a single director doesn't want to be the carrier of bad news. Self-serving tendencies and optimism + +feelings of confidence and optimism: many boards also select new directors who + +are much like themselves; chat share similar ideological viewpoints. Deprival - Directors don't want to lose income and status. Respecting reasons no matter how illogical - the CEO gives them reasons. +Believing first and doubting later - believing what the CEO says even if not true, especially when distracted. Consistency- directors want to be consistent with earlier decisions - dumb or not. + +Can we get rid of a bad CEO? Warren Buffett and Charles Munger says: + +Buffett: When certain boards consisting of prominent people are embarrassed publicly by the media attention, I think that acts as kind of an early warning signal to some other boards because big shots - and +they look for big shots frequently in terms of dressing up boards - do not like to look foolish, at least publicly... + +Munger: ...in terms of the director's actually rebelling against the CEO, it tends to happen in one or two cases: One is when they reduce the directors' perks - which most CEOs are wise enough not to do. The +ocher is when the situation gets so bad chat it threatens to + +107 + +disgrace the directors. But you rarely see people taking action before they're threatened with disgrace. + +Warren Buffett says that we need true independence from directors i.e. a: "willingness to challenge a forceful CEO when something is wrong or foolish." He continues: "In addition to being independent, +directors should have business-savvy, a shareholder orientation and a genuine interest in the company." + +Charles Munger adds: + +The correct system is the Elihu Root System. Elihu Root, who had three different cabinet appointments, ifI remember right, said no man was fit to hold public office who wasn't perfectly willing to leave it at +any time. And if Elihu Root didn't approve of something the government asked him to do, he could always go back and be the most sought-after lawyer in the world. He had an identity to go back to - so he +didn't need the government's salary. + +Well, I think that also ought to be more the test in corporate directorships. Is a director really fit to make tough calls who isn't perfectly willing to leave the office at any time? My answer 1s no. + +CONTEXTUAL INFLUENCES + +Most social acts have to be understood in their setting, and lose meaning if isolated. + +No error in thinking about social facts is more serious than the failure to see their place and function. + +- Solomon Asch (American social psychologist, 1907-1996) + +Our behavior is influenced by social situational factors, conditions and circumstances, the structure or description of a problem or choice, and our desires, mood and expectations. + +We tend to overestimate personal characteristics and motives when we explain the behavior of others. We underestimate situational factors like social pressure, roles or things over which there are no control. +An example is, blaming an individual rather than a poorly designed system for failure. Chance also matters. Maybe we sometimes give too much blame to people who had bad luck, and too much credit to those who +were simply lucky. + +We expect people to be consistent in their behavior. But we behave differently in different situations. For example, we behave differently at home, in school, at work, and among friends; when alone and when +in a group; when seen and when anonymous. + +108 + +"I shouldn't have been so fast judging him as a bad person. Who knows, I may have done the same if put in the same situation." + +Extreme circumstance and conditions can cause people to do things they would never do under normal circumstances. Put good people in a bad situation and their normal behavior changes. The Zimbardo prison +experiment at Stanford studied the roles people play in prison situations. Students were randomly assigned to the roles of prisoners and guards for a two-week period. Tests showed that all students were +normal people and physically and mentally healthy. A simulated prison environment was created to mimic real-life prison conditions, where they lived for several days. Students playing guards behaved +aggressively and students playing prisoners behaved helplessly. Guards rapidly began to treat the prisoners as if they were non-humans. The prisoners began acting depressed and showed extreme stress. The more +the prisoners acted like non-humans, the more the guards mistreated them. The experiment ended after six days. + +In a statement prepared for the U.S. House of Representatives Committee on the Judiciary, the originator of the experiment, Philip Zimbardo, said: "We were horrified because we saw some boys treat other boys +as if they were despicable animals, taking pleasure in cruelty, while other boys became servile, dehumanized robots who thought only of escape, of their own individual survival, and of their mounting hatred +of the guards." + +Often when we are in a role, we tend to act as others expect. Zimbardo said: "Even when they thought they didn't have to meet anyone's expectations, the role of prison guard determined their actions." + +An American Indian proverb says: "Don't judge a man until you've walked two moons in his moccasins." How would we behave if we were anonymous, part of a group, tired and exhausted, and others had been labeled +as enemies, evil or worthless? + +"Why is John tense when people watch his golf swing?" + +Are our actions observed or not? People may change their behavior merely because they are being observed. + +"No one can see me. " + +Anonymity can create destructive behavior. Studies show that peaceful students can become aggressive when they are made to feel anonymous by having their identity masked. + +109 + +The less knowledgeable we are about an issue, the more influenced we are by how it is framed. + +The answers we get depend on the questions we ask. The British philosopher + +Herbert Spencer said: "How often misused words generate misleading thoughts." Consider how a statement, problem, consequence, or question is presented. How is it worded? What is its context? Are we +considering certain features and ignoring others? Emotional, selective and appealing frames influence us. + +How a choice is presented influences our preferences. For example, we prefer a product that is presented as "95% fat free" rather than "5% fat". We respond differently depending on whether something is +presented in terms of gains or in terms oflosses. A surgical procedure that has a 40% chance of success seems more appealing than one that has a 60% chance of failure. + +Frequencies appeal to our emotions. What is the chance that a mental patient commits an act of violence within 6 months after discharge? Studies show that experienced psychologists and psychiatrists judge the +patient as more dangerous when the risk of violence were presented as relative frequencies (e.g., 20 criminals out of 100 similar to the patient are estimated to be violent to others...) than when the risk +was presented as a probability (e.g., it is estimated that similar patients has a 20% chance of being violent to others ...). One study showed that a disease that kills 1,286 of 10,000 people (12.86%) was +rated as riskier than one that kills 24.14 of 100 people (24.14%). + +We are influenced by the order, first or last, in which a presentation happens. The key variable is the amount of time that separates the presentations, the time when we have to make a judgment, and which +presentation is the most easily remembered. + +Assume that two presidential candidates are speaking on an issue, one directly after the other. If some time passes before we have to make a judgment, we are likely to be more influenced by the first +presentation. Assume now that some time passes between the first and last presentations, but we have to make a judgment immediately after the last presentation. Then we are more likely to be influenced by the +last presentation. + +'1 put my paycheck in the bank at 4% interest, and borrowed money for a car loan at 10% interest. " + +We create our own frames by doing mental accounting. We treat assets of the same value differently depending on where they come from or their importance. We put different values on the same dollar, and are +more willing to risk money we have won than money we have earned. A gain of $1,000 from playing roulette + +110 + +has less value than $1,000 earned from hard work. '1 didn't gamble with my + +$1,000, I only gambled with the $1,000 I won on the casino." But it is the same amount of money. + +In one experiment psychologists found that people who lost a $10 theater ticket on the way to the theatre were reluctant to buy a second ticket. Those who instead lost a $10 bill on the way to buy a $10 +theatre ticket saw the loss of the money and the purchase of the ticket as unrelated, so they would buy the ticket. But, in both cases, the loss was the same. + +We should view our assets in terms of their entirety. A dollar is a dollar independent of where it comes from. What counts is what we put in or take out of our pocket. + +There is a difference in behavior whether we deal with someone we know and a stranger or under the eye of an experimenter. + +"[ expect you to understand what Tm saying. I know you can do this. " + +"Things are not always what they seem," said the 1st Century Roman philosopher Phaedrus. Our behavior can be influenced by the expectations of others- teachers, coaches, bosses, etc. For example, to please +the observer, a research subject may read in a desired result. A patient may wish to respond to a treatment in what they see as the correct way. We live up to what is expected of us. + +Studies show that patients can have faster heartbeats and higher blood pressure when examined by a doctor compared to a nurse. + +We often see what we want or expect to see. A doctor may see an effect in a patient because he expects to see it. We often don't see what we don't expect to see. + +Do we treat people according to our expectations? + +Assume Mary is on her way to meet someone for the first time. Does it matter if this person has been described as friendly or emotionally cold? Yes, it produces a change in Mary's expectations of that +individual and a change in her behavior. Mary will expect friendliness or hostility and behave according to her expectations. The person may react to Mary in a way that confirms her expectations. We treat +people like we expect them to be. If we expect people to be bad, we treat them in a certain way, which may cause them to behave badly. + +Assume that a new teacher is told that half of the class has high IQs and half has low IQs. The teacher is given the names of the supposed intelligent kids and the supposed not so intelligent ones. In +reality, someone has randomly selected the two groups. By the end of the year, the experimental premise will become a + +111 + +self-fulfilling prophecy. The kids the teacher thought had high IQs will be doing better than the kids with supposedly low IQs. This has been demonstrated in studies of elementary school students. Teachers +taught much better when they expected a lot from their students. + +Irrational behavior in one context may cause good results in another. + +We aren't stupid - judgments are often a function of context. The judgments of others can be informative, obedience to an authority is important for order, being careful in getting involved in a dangerous +situation may save our life. + +What about all the evidence from lab experiments? + +Lab experiments can't resemble reality. + +There is a difference between real life and the controlled and somewhat artificial context of the lab. What is happening in some lab experiments may not happen in a natural situation. For example, many +experiments are often played anonymously without repetition. What is the structure of the problem? The environment? Assumptions? Importance? Cost of being wrong? Often there exists more than one right answer. +The context of the task matters. In a more realistic, concrete, and social context, many tasks are often solved correctly. + +Studies show that we are overconfident. Does this mean we are always overconfident? No, the studies only show that some people are overconfident in some tasks in a certain context. + +SOME FINAL ADVICE FROM CHARLES MUNGER + +Follow these three pieces of advice from Charles Munger: + +I don't want you to think we have any way oflearning or behaving so you won't make a lot of mistakes. I'm just saying that you can learn to make fewer mistakes than other people - and how to fix your mistakes +fosterwhen you do make them. But there's no way that you can live an adequate life without [making] many mistakes. In fact, one trick in life is to get so you can handle mistakes. Failure to handle +psychological denial is a common way for people to go broke: You've made an enormous commitment to something. You've poured effort and money in. And the more you put in, the more that the whole consistency +principle makes you think, "Now it has to work. If I put in just a little more, then it'll work." + +And deprival super-reaction syndrome also comes in: You're going to lose the whole thing if you don't put in a little more. People go broke that way - because they can't stop, rethink and say, "I can afford +to write this one off and live to fight + +112 + +again. I don't have to pursue this thing as an obsession - in a way that will break me." Part of what you must learn is how to handle mistakes and new facts that change the odds. Life, in part, is like a +poker game, wherein you have to learn to quit sometimes when holding a much-loved hand. + +I've gotten so that I now use a kind of two-track analysis. First, what are the factors that really govern the interests involved, rationally considered? And second, what are the subconscious influences where +the brain at a subconscious level is automatically doing these things - which by and large are useful, but which often misfunction. One approach is rationality - the way you'd work out a bridge problem: by +evaluating the real interests, the real probabilities and so forth. And the other is to evaluate the psychological factors that cause subconscious conclusions - many of which are wrong. + +Take all the main models from psychology and use them as a checklist in reviewing outcomes in complex systems. No pilot takes off without going through his checklist: A, B, C, D ... And no bridge player who +needs two extra tricks plays a hand without going down his checklist and figuring out how to do it... And, to repeat for emphasis, you have to pay special attention to combinatorial effects that create +lollapalooza consequences. + +Don't our feelings, instincts or our intuition help us avoid misjudgments? + +Natural selection equipped us with traits adapted for the environment in which humans spent most of their time. Feelings like love, compassion, anger, fear, jealousy, and embarrassment can be explained +biologically. They exist for a reason + +to help us survive and reproduce. Somerset Maugham said: "Love is only a dirty trick played on us to achieve a continuation of the species." Why does sex feel good? Because it makes us reproduce. If sex felt +painful, we wouldn't be here today. Our emotions are also part of the human whole. Our "good" emotions wouldn't be good without our "bad" emotions. + +Feelings and instincts helped our ancestors navigate in the world. The ancestral environment rewarded actions before thought, emotion before reason. Fast intuitions and quick reactions are vital responses for +organisms. Spending time pondering may be dangerous. + +The problem is that feelings can be twisted. Intuition is inconsistent and feelings can sometimes get out of control. Especially when we feel uncertain, distracted or stressed. + +Remember Chinese philosopher Lao-Tsu (604-531 BC): "He who knows men is clever; He who knows himself has insight; He who conquers men has force; He who conquers himself is truly strong." + +113 + +In Part Three we will study other reasons why we make misjudgments. These are partly rooted in our psychological make-up; our tendency to use crude rules of thumb, and make hasty judgments and other +psychological tendencies discussed in Part Two. They also have their roots in a lack of considering some basic ideas from physics and mathematics. + +Charles Munger gives us some introductory remarks on the value of knowing the methods of physics: + +One of the things that influenced me greatly was studying physics.. .IfIwere running the world, people who are qualified to do physics would not be allowed to elect out of taking it. I think that even people +who aren't [expecting to] go near physics and engineering [in their planned profession] learn a thinking system in physics that is not learned so well anywhere else. Physics was a total eye-opener. + +The tradition of always looking for the answer in the most fundamental way available + +- that is a great tradition and it saves a lot of time in this world. And, of course, the problems are hard enough that you have to learn to have what some people call assiduity. Well, I've always liked that +word - because to me it means that you sit down on your ass until you've done it. + +114 + +- PART THREE - + +[1mTHE PHYSICS AND MATHEMATICS OF MISJUDGMENTS [0m + +There will come a time when mathematical ignorance, like public smoking, will become socially unacceptable. + +- Jerry King (Professor of Mathematics, from The Art of Mathematics) + +115 + +This part illustrates reasons for misjudgments and mistakes that can be reduced by considering some basic principles from physics and mathematics. The big ideas are explained using examples from business, +investing, law, medicine, etc. As in Part Two, we begin with a list of the causes of misjudgments and mistakes. Each item on the list will be explained over the next chapters. + +Systems thinking + +Failing to consider that actions have both intended and unintended consequences. Includes failing to consider secondary and higher order consequences and inevitable implications. + +Failing to consider the whole system in which actions and reactions take place, the important factors that make up the system, their relationships and effects of changes on system outcome. + +Failing to consider the likely reactions of others - what is best to do may depend on what others do. + +Failing to consider the implications of winning a bid - overestimating value and paying too much. + +Overestimating predictive ability or usmg unknowable factors m making predictions. + +Scale and limits + +Failing to consider that changes in size or time influence form, function and behavior. + +Failing to consider breakpoints, critical thresholds or limits + +Failing to consider constraints - that a system's performance is constrained by its weakest link. + +Causes + +Not understanding what causes desired results. + +Believing cause resembles its effect - that a big effect must have a big or complicated cause. + +Underestimating the influence of randomness in bad or good outcomes. + +Mistaking an effect for its cause. Includes failing to consider that many effects may originate from one common root cause. + +Attributing outcome to a single cause when there are multiple causes. + +Mistaking correlation for cause. + +Failing to consider that an outcome may be consistent with alternative explanations. + +117 + +Drawing conclusions about causes from selective data. Includes identifying the wrong cause because it seems the obvious one based on a single observed effect. Also failing to consider information or evidence +that is missing. + +Not comparing the difference in conditions, behavior and factors between negative and positive outcomes in similar situations when explaining an outcome. + +Numbers and their meaning + +Looking at isolated numbers -failing to consider relationships and magnitudes. Includes not using basic math to count and quantify. Also not differentiating between relative and absolute risk. + +Underestimating the effect of exponential growth. + +Underestimating the time value of money. + +Probabilities and number of possible outcomes + +Underestimating risk exposure in situations where relative frequency (or comparable data) and/or magnitude of consequences is unknown or changing over time. + +Underestimating the number of possible outcomes for unwanted events. Includes underestimating the probability and severity of rare or extreme events. + +Overestimating the chance of rare but widely publicized and highly emotional events and underestimating the chance of common but less publicized events. + +Failing to consider both probabilities and consequences (expected value). + +Believing events where chance plays a role are self-correcting - that previous outcomes of independent events have predictive value in determining future outcomes. + +Believing one can control the outcome of events where chance is involved. + +Judging financial decisions by evaluating gains and losses instead of final state of wealth and personal value. + +Failing to consider the consequences of being wrong. + +Scenarios + +Overestimating the probability of scenarios where all of a series of steps must be achieved for a wanted outcome. Also underestimating opportunities for failure and what normally happens in similar +situations. + +Underestimating the probability of systems failure - scenarios composed of many parts where system failure can happen one way or another. Includes + +118 + +failing to consider that time horizon changes probabilities. Also assuming independence when it is not present and/or assuming events are equally likely when they are not. + +Not adding a factor of safety for known and unknown risks. Size of factor depends on the consequences of failure, how well the risks are understood, systems characteristics and degree of control. + +Coincidences and miracles + +Underestimating that surprises and improbable events happen, somewhere, sometime, to someone, if they have enough opportunities (large enough size or time) to happen. + +Looking for meaning, searching for causes and making up patterns for chance events, especially events that have emotional implications. + +Failing to consider cases involving the absence of a cause or effect. + +Reliability of case evidence + +Overweighing individual case evidence and under-weighing the prior probability (probability estimate of an event before considering new evidence that might change it) considering for example, the base rate +(relative frequency of an attribute or event in a representative comparison group), or evidence from many similar cases. Includes failing to consider the probability of a random match, and the probability of +a false positive and false negative. Also failing to consider a relevant comparison population that bears the characteristic we are seeking. + +Misrepresentative evidence + +Failing to consider changes in factors, context or conditions when using past evidence to predict likely future outcomes. Includes not searching for explanations to why past outcome happened, what is required +to make past record continue, and what forces can change it. + +Overestimatingevidence from a single case or small or unrepresentativesamples. + +Underestimating the influence of chance in performance (success and failure). + +Only seeing positive outcomes - paying little or no attention to negative outcomes and prior probabilities. + +Failing to consider variability of outcomes and their frequency. + +Failing to consider regression - in any series of events where chance is involved unique outcomes tends to regress back to the average outcome. + +119 + +- ONE - + +SYSTEMS THINKING + +Wanted and unwanted consequences + +In one of Aesop's fables the following story is told: + +A poor widow living alone in the country kept a faithful hen. Each morning the hen laid a big, brown egg for the woman's breakfast. One day the widow thought to herself: "Now ifI were to double my hen's +allowance of barley, she would lay me two eggs a day instead of one." So she started feeding her biddy a double measure of grain, and soon the hen began to grow fat and sleek and lazy. It wasn't long before +she stopped laying altogether. + +Every action has consequences. Both intended and unintended. No matter how carefully we plan, we can't anticipate everything. Often we fail to consider what other events are likely to occur as a result of +some action. Politics, medicine, welfare programs, technology, military actions and laws generate unintended consequences. Whatever we do (or don't do), there are multiple consequences. They might not be what +we expect. In one study, traffic engineers found that adding new routes (like a more direct road) could make traffic go slower. During merging, cars drive closer to each other and therefore slow down. +Furthermore, studies of car safety show that wearing seat belt makes drivers feel more secure, making them drive faster or more recklessly. + +By solving one problem, we generate another one and sometimes create an even worse one. + +There was a problem with mice on campus. The solution for exterminating the mice was to pay students $1 for every dead mouse they delivered. It worked! Until the students began breeding the mice in order to +make more money. + +Actions have consequences and consequences have further effects. Charles Munger gives an example regarding Medicare: + +They had all these actuarial studies that showed the cost would be X. And the cost turned out to be more than 1OX... They didn't factor in the fact that effects have effects... they didn't think through the +incentive effects of the way they were changing the rules. They + +120 + +created a system wherein they were reimbursing both doctors and hospitals, in effect, on a cost plus percentage of cost basis. The minute they did that, the hospitals and doctors found wonderful ways to talk +the patients into buying all kinds of care that got reimbursed ... good for the hospital and good for the doctor, but bad for the patient and bad for the taxpayers. + +Should good intentions eliminate bad consequences? No. Outcomes don't follow from intentions and intentions by definition apply only to intended consequences. But as Samuel Johnson said, "The road to hell is +paved with good intentions." Isn't it more important to find out if the consequences are good rather than if the reasons are good? Ask: What are we trying to improve? What can reasonably be expected to +happen? Are the net effects positive or negative? + +Good thinking is better than good intentions. In the 18th Century, Pierre S. du Pont, a deputy to the French National Assembly said: "Bad logicians have committed more involuntary crimes than bad men have +done intentionally." + +But even good thinking can have undesired consequences. Charles Munger gives an example: + +An excess of what seems like professionalism will often wind up hurting you horribly precisely because those careful procedures themselves often lead to overconfidence in their outcome... Long Term Capital +Management, the well-known hedge fund recently collapsed as a result of its principals' overconfidence in their highly leveraged methods. And it collapsed despite those principals having IQ's that must have +averaged 160 or more...Smart, hard-working people aren't exempt from professional disasters resulting from overconfidence. Often they just go aground in the more difficult voyages on which they choose to +embark based on self appraisals in which they conclude that they have superior talents and methods. It is, of course, irritating that extra care in thinking isn't all good- that it also introduces extra +error. But most good things have undesired "side effects." And thinking is no exception. + +One way to reduce unintended consequences is to stop focusing on isolated factors and instead consider how our actions affect the whole system. + +The whole system + +Sales volume dropped and John suggested· "Why don't we reduce price? It's a sure-fire way to win back customers and boost sales. We make up on volume what we lose on price and as a result we increase our +market share. Profits will surely rise. " + +"Where did we go wrong? We lost market share. Profits and stock price declined. " + +121 + +Why didn't TransCorp's profit increase? They forgot to think about all the factors that influenced the outcome. They didn't anticipate the consequences of cutting prices. They didn't consider other factors +and conditions that influenced the value of the business. Some were changed as a consequence of TransCorp's decision to reduce prices in anticipation of higher volumes. Volume increases affect costs and +behavior and need for investments in operating assets. There may also have been production problems due to technical constraints or the price decrease wasn't enough to make customers switch from the +competition. + +How a system behaves is a function of all the factors (human and non-human) that make up and influence the system. + +A system is a collection of parts working together as a whole. Take a business as an example. It is a collection of parts but works as a complete system. There are variables like suppliers, employees, +customers, demand, competition, etc. There are activities like purchasing, manufacturing, warehousing, logistics, and distribution. There are technological systems and equipment needed to conduct the +business. All these parts work together. + +TransCorp fired 200 people to cut costs. + +We optimize one component at a time instead of optimizing the whole (what we finally want to accomplish). TransCorp forgot to consider how a change influences the whole system. Cost cutting doesn't +automatically translate into higher value. TransCorp's decision to foe people caused manufacturing and delivery problems, which in turn caused delays in customer production. This created a loss of customers +and reputation. The end result was lower profits. + +Why reduce prices? What is the purpose? What does TransCorp ultimately want to achieve? + +Systems adjust in response to feedback. A positive feedback amplifies an effect, while a negative dampens it. Take the stock market as an example of a positive feedback. The stock market falls causing a +sell-off. This creates a ripple effect of further sell-off and price declines. The opposite occurs in a stock market bubble. A thermostat is an example of negative feedback. + +Try to optimize the whole and not asystem's individual parts. Think through what other variables may change when we alter a factor in a system. Trace out the short and long-term consequences in numbers and +effects of a proposed action to see if the net result agrees with our ultimate goal. + +Ask: What key factors influence the outcome of the system and how do these factors interact? What other things may change as a consequence of some action? Given these conditions, what likely consequences +(wanted and unwanted) will the + +122 + +proposed action have on the system, considering all the relevant factors that influence or are part of the system? Will the net result be what we want? A manager can for example ask: How is the value of the +business likely to change considering important factors that influence business value? + +Considering the whole includes anticipating the reactions of others. + +The reaction of others + +Game theory is a study of conflict between thoughtful and potential deceitful opponents. + +William Poundstone (from Prisoner's Dilemma) + +TransCorp cut the price and lost volume. + +What happened? TransCorp's competitors matched the price cut. Competitors can match price cuts or even go below it to regain, keep or increase market share. When thinking through consequences, consider what +other people are likely to do. Since our interests may conflict with others, the final outcome of our decision often depends on what others will do. What other people do may + +depend on what they think we will do, their available choices, interests, and how they are thinking- including their misjudgments. As we have learned, humans don't always act rationally. + +Game theory deals with what happens when individuals or groups of people interact with one another to achieve their goals. We saw an example of game theory in Part One (Prisoner's Dilemma). It also applies to +negotiations. Factors that decide the final outcome of a negotiation are: 1) the number of participants, 2) if we meet the participants again in the future, 3) the time lapse in between, 4) the degree of +anonymity and communication, and 5) our relative position of strength which includes our other options, back-up alternatives and need to reach an agreement. + +The winner's curse + +I sent the club a wire stating, "Please accept my resignation. + +I don't care to belong to any club that will have me as a member. " + +Groucho Marx + +Several mining firms including MineCorp, one of TransCorps subsidiaries, are bidding on the right to mine silver. + +No firm knows for certain how much silver there is and hence what the true value is.They each hire an expert to make an educated guess. By definition, these expert guesses will range from too low to too high. +Some firm's expert will probably be + +123 + +dose. But they won't win. The winning firm was MineCorp since their expert had the most optimistic estimate of the value (the seller accepts the highest bid). But there was less silver in the mine than their +expert guessed and less value than what MineCorp paid for the rights. This means that the winning bidder was cursed since the bid was higher than the value. Later it was shown that MineCorp also +underestimated its costs of production. + +Three Atlantic Richfield engineers, Capen, Clapp and Campbell, introduced the idea behind the Winner's Curse when they did a study of companies bidding for oil fields. Their basic idea was Uournal of +Petroleum Technology, June 1971), that "a lease winner tends to be the bidder who most overestimates reserve potential." + +Let's say TransCorp has 10 projects from 10 divisions to choose from. They only have time and money to invest in one project. Which one are they most likely to pick? Of course, the one that looks most +attractive. But all division managers have an incentive to make their own project the most attractive one. The risk is therefore that TransCorp chooses the project with the most optimistic forecast and +therefore more likely to disappoint. + +"Hurray, I won the auction!,"said John. "What you 'won' was the right to pay more for something than everyone else thought it was worth,"said Mary. + +Winning is an informative event, telling us whose estimate was most optimistic. When we place a bid on a house, company, project, or negotiate to buy something, we don't realize what is implied by an +acceptance of our offer. That we may have overestimated its value and therefore paid too much. + +Research shows that the more bidders there are competing for a limited object, each having the same information, and the more uncertain its value is, the more likely we are to overpay. Instead, if our +objective is to create value, the more bidders there are, the more conservative our bidding should be. This also implies that the less information we have compared to other bidders or the more uncertain we +are about the underlying value, the lower we should bid. If we participate in auctions, we must ascertain the true value of what's being sold or its value to us. + +When we negotiate with one party and want an acceptance for an offer, the other party may have an informational advantage. The other party is most likely to accept our offer when it is least favorable to us, +especially if it is a one-time relationship or if the other party is anonymous. + +Consider the seller's perspective. Ask: Why are they selling? How would I reason ifl think it through from the viewpoint of the other person? Why would I make a better decision than someone who has all the +information? + +124 + +Predictions + +Do not, therefore, expect any prophecy from me: had I known what one will discover tomorrow, I would have published it long ago, to secure priority. + +- Henri Poincare (French mathematician and scientist, 1854-1912) + +When asked about corporate responsibility for social problems, Charles Munger answered: + +I'm all for fixing social problems. I'm all for being generous to the less fortunate. And I'm all for doing things where, based on a slight preponderance of the evidence, you [3mguess [0mthat it's likely to do more +good than harm... + +What I'm [3magainst [0mis being very confident and feeling that you know, for sure, that your particular intervention will do more good than harm given that you're dealing with highly complex systems wherein +everything is interacting with everything [3melse. [0mGreek philosopher Heraclitus wrote: "Nothing endures but change." The world is too complicated to predict all the effects of some action. Maybe a business can +predict scenarios like reduction in demand and intensified competition, but some events, their timing, magnitude or consequence, are impossible to anticipate. + +Mark Twain said: "The art of prophecy is very difficult, especially with respect to the future." It is hard to predict something when we don't (or can't) foresee or understand how an entire system works, what +key variables are involved, their attributes, how they influence one another and their impact. Even if we know the key variables, their values may be impossible to estimate. They may also change over time and +be dependent on context. It may also be impossible to estimate how they will interact as a whole. + +The more parts involved and the more they interact, the more can happen, and the harder it is to determine consequences of individual actions. + +According to Dr. Gerald Edelman, the brain is an example of a complex system: + +A complex system is one in which smaller parts form a heterogeneous set of components which are more or less independent. But as these parts connect with each other in larger and larger aggregates, their +functions tend to become integrated, yielding new functions that depend on such high order integration. This is, in fact, just what happens in the brain. + +As the number of variables grows, the number of possible interactions grows even faster. Assume that two subsystems, A and B, cause the behavior of a system. + +125 + +Each subsystem consists of 5 parts. If we only consider two-way interactions among parts, there are 10 interactions between A-parts, 10 between B-parts, and 25 interactions between A and B parts. This means +that the behavior of the system is composed of 55 determinants (SA-parts + 5B-parts + 10 interactions between A parts + 10 interactions between B-parts + 25 interactions between A and B parts). 18% (10 of 55) +of all determinants derive from individual effects of parts in A and B while about 82% (45 of 55) derive from interactions. Now imagine a system where A and B each consists of 100 parts. There are now 20,100 +determinants (100+100+4,950+4,950+10,000) and 19,900 interactions meaning that 99% (19,900 of20,100) of system determinants derive from interactions. + +We often take too little notice of how variables interact. Take the economy as an example. There are many factors to consider. They include interest rates, currency exchange rates, balance of trade figures, +unemployment rates, consumer confidence, political factors, the stock market, business cycles, biases, etc. These factors are interconnected, and it is hard to tell which is most important. Add to this that +people's behavior isn't fixed. We are emotional creatures, our preferences change, and we react to each other's actual or expected decisions. A prediction may also make us change our expectations and +behavior, making the prediction more or less likely to come true. + +Charles Munger says: "We try and predict what individual investments will swim well in relation to the tide. And then we tend to accept the effects of the tide as those effects fall." + +"Ifsomeone could forecast the stock market, why are they selling advice through $100 newsletters?" + +Fidelity's former manager Peter Lynch said in One Up on Wall Street: "There are 60,000 economists in the U.S., many of them employed full-time trying to forecast recessions and interest rates, and if they +could do it successfully twice in a row, they'd all be millionaires by now... As far as I know, most of them are still gainfully employed, which ought to tell us something." + +Predictions about the future are often just projections of past curves and present trends. This is natural since our predictions about the future are made in the present. We therefore assume the future will +be much like the present. But the future can't be known until it arrives. It is contingent on events we can't see. For example, who in the year 1900, could foresee events like World War I and II, the 1929 +stock market crash, Chernobyl or technologies like the television, laser, computer, internet or the DVD? Many key inventions happened by accident and sagacity. For example, in 1867 Alfred Nobel accidentally +discovered that when + +126 + +nitroglycerin dripped on kieselguhr (a mineral made of small, fossilized remains of sea animals), it formed a stable paste that was safer to use than liquid nitroglycerin alone. He called it dynamite. + +Don't believe people that say they can forecast unforeseeable variables. Nobody can forecast interest or currency rates, the GDP, turning points in the economy, the stock market, etc. Massive amounts of +information, advanced computers or fancy mathematical formulas don't help. Warren Buffett says that we tend to put too much comfort in computer models and the precision they project: "We believe the precision +they project is a chimera. In fact, such models can lull decision-makers into a false sense of security and thereby increase their chances of making a really huge mistake." + +Economics isn't like physics. There are no reliable or precise formulas where we easily can fill in the values of various economic factors, and then have the work done. Charles Munger says: "Economics +involves too complex a system... economics should emulate physics' basic ethos, but its search for precision in physics-like formulas is almost always wrong in economics." J.M. Keynes adds: "To convert a +model into a quantitative formula is to destroy its usefulness as an instrument of thought." + +Financial writer Roger Lowenstein writes in When Genius Failed: "The next time a Merton [Robert Merton, 1997 Nobel Laureate for developing mathematical risk management formulas] proposes an elegant model to +manage risks and foretell odds, the next time a computer with a perfect memory of the past is said to quantify risks in the future, investors should run - and quickly- the other way." + +That an event has happened many times before, doesn't mean that it will continue to happen. And just because an event has never happened before, doesn't mean it can't happen in the future. Take catastrophic +events as an example. Who could have predicted the September 11, 2001 terrorist attack on the World Trade Center? Hijacking four planes simultaneously and using them to attack the + +U.S. was improbable. Yet it happened. + +Modern History Professor Richard Evans wrote in In Defence of History: "Time and again, history has proved a very bad predictor of future events. This is because history never repeats itself; nothing in human +society... ever happens twice under exactly the same conditions or in exactly the same way." + +Sometimes we can guess that certain things are bound to happen, but we can't predict when they will happen. + +Will it rain two weeks from now? + +Some things are possible to predict short-term but impossible to predict long- + +127 + +term. Small changes make a big difference over time. Long-term weather forecasts are an example. Many factors determine the weather. Factors that can't be reliably measured ahead of time. Small changes in the +temperature and pressure over the ocean can lead to large variations in the future development of storm systems. Weather predictions become more inexact the further out they are. + +The difficulty lies in initial condition uncertainties and model error. For example, small errors in the initial values ofvariables can grow and produce errors in the forecast. There may also be gaps in the +initial data. But even if we know the initial conditions perfectly, the models are not perfect. Small model errors either in physics or numerics can also grow and produce different states. For example, not +all atmospheric processes are understood. Furthermore, all weather models operate on a finite grid or limited area, typically in the order of 10 to 100 kilometers, depending on the study area. This means that +the numerical resolution and representation is finite. But many physical processes and features that influence the weather occur on smaller scales than those resolved by the grid. For example, energy +transfers at the surface, small atmospheric processes (such as isolated thunderstorms), topography, lakes, and vegetation. The model must treat or "parameterize" the effects of these "sub-grid" features' +effects on the resolved scale. These parameterizations are simplifications and approximations and may also account for many of the model errors. So even if we know all the principles behind the weather and +what governs the atmosphere, fundamental limitations make it hard to make accurate predictions. + +Many meteorologists know they can't make a perfect forecast and have + +therefore given up on predicting whether it will or will not rain beyond a few days into the future. Instead, they have altered their approach and try to quantify the uncertainty in the prediction ("The +probability of precipitation is 20% this Saturday''). This uncertainty is small at short lead times and greater at longer lead times. It also varies with the weather situation, the location and the size of +the area the prediction covers. When meteorologists make forecasts two weeks out, they look at the climatological frequency of precipitation, determined from a history of what has happened in the past. + +All prediction is inherently uncertain, and we have a duty to tell people about the uncertainties of our predictions and our past error rates. Albert Einstein wrote in a March 14, 1954, letter: "The right to +search for truth... implies also a duty; one must not conceal any part of what one has recognized to be true." + +128 + +- Two - + +SCALE AND LIMITS + +Scale of size and time + +Changes in size or time influences form, function and behavior. If something of a certain size is made bigger or smaller, it may not work the same way. Some things get better and others get worse. For +example, changes in the size of an organism affect its strength, surface area, complexity, metabolism, longevity, and speed of movement. + +How do weight, strength and surface area change when we change size? + +If we double the length of a similarly shaped object, surface area increases 4 times and volume 8 times. Surface area increases at the square of length and volume at the cube oflength (to get areas we +multiply two lengths together, and to get volumes we multiply three lengths). + +Volume always grows faster than surface area as we increase size, independent of an object's shape. This places limitations on the size of things. + +Does it make any difference in melting time if we use one ice cube (volume 8) or 8 smaller ones (total volume 8}? + +If we increase size, volume grows faster than surface area. What does this mean? The relationship between surface area and volume decreases when we increase the size. It also means that the relationship +increases when we decrease the size. Take ice cubes as an example. Let's assume the larger one has a side length of 2 and the smaller ones a side length of 1. + +Small ice cube + +Large ice cube + +Side length + +1 + +2 + +Cross-section surface area (side length) 2 + +1 + +4 + +Total surface area (6 sides) + +6 + +24 + +Volume (side length) 1 + +1 + +8 (weight) + +Ratio of total surface area to volume + +6 + +3 + +As we can see, the large ice cube has less surface area per unit volume than 8 small ice cubes. Total surface area is the total area of all 6 surfaces of the ice cube. + +129 + +This means that 8 ice cubes have a surface area of 48 (8 x 6) versus 24 for the larger ice cube. This also means that 8 small ice cubes melt faster than one large ice cube, since the amount of heat an ice +cube can absorb depend on its surface area (the melting process occurs at the surface). Whenever we make objects smaller, we get more surface area per unit volume. For example, since iron rusts when exposed +to air and rusting occur at the surface, a steel knife rusts more slowly than steel wool. + +Why did the dinosaurs have such small heads in relation to their bodies? + +Living things are shaped and constrained by basic mathematical principles. Weight depends on volume and strength or load-bearing ability on area. The strength of a muscle or a bone is a function of +cross-section area. Strength does not increase at the same rate as weight and volume. When we increase size, weight increases faster than strength. Scale up an organism and sooner or later it will be too weak +to support its own weight. Double the size of a small dinosaur - twice as long, wide and high - and it weighs 8 times as much as before. We now need a neck that is 8 times stronger than before since it must +hold 8 times the weight. But since the strength of the neck is proportional to its cross-section area, the neck is only 4 times stronger. There comes a point where the neck breaks. + +What about the giants we see in the movies? + +Assume we make a human 10 times larger than normal. This means he is now 10 times longer, 10 times wider, and 10 times higher. He now weighs 1,000 times more but he is only 100 times stronger (as muscular +strength is proportional to the cross section area of a muscle). Since the load-bearing capacity of bones scales in the same manner his bones would be subject to ten times more stress than normal. He needs +thicker bones to support more weight. Otherwise his legs will crush. This is why elephants have such thick stumpy legs to support their weight. The giant has 1,000 times more meat on the body but only 100 +times the skin to hold it together meaning ten times the pressure on its skin (since pressure is proportional to area). This also means that his skin surface area is too small to remove the heat emitted from +his huge body. He would suffer from overheating since the amount of heat his body produces is proportional to the cube of his length (1,000), while the amount of heat he dissipates through the skin is +proportional to the square of his length (100). + +The British biologist Sir D'Arcy Wentworth Thompson said in On Growth and Form: "Everywhere nature works true to scale, and everything has its proper size accordingly. Men and trees, birds and fishes, stars +and star-systems, have their + +130 + +appropriate dimensions, and their more or less narrow range of absolute magnitudes." + +Some things in nature have about the same shape or pattern regardless of the scale we view them. Asmall part of a cauliflower looks much the same as the entire flower. Other examples include clouds, ferns, +snowflakes, river networks, systems of blood vessels and the structure of coastlines. + +'John needs to hire a new assistant and ask his boss: 'Do I have your OK? Adding + +$20,000 to the payroll should be inconsequential "' + +The concept of scale also applies to time - how things change over time or when something is repeated. What would Warren Buffett have told John? "The proposal should be evaluated as a $3 million decision, +given that an additional person would probably cost at least that amount over his lifetime, factoring in rises, benefits and other expenses." + +Small, slow changes operating over long periods can have great consequences. For example, we have seen how small genetic changes can have major anatomical effects over time. + +Breakpoints, critical thresholds and limits + +At a certain scale, a system reaches a critical mass or a limit where the behavior of the system may change dramatically. It may work better, worse, cease to work or change properties. + +Small interactions over time slowly accumulate into a critical state -where the degree of instability increases. A small event may then trigger a dramatic change like an earthquake. + +A small change may have no effect on a system until a critical threshold is reached. For example, a drug may be ineffective up until a certain threshold and then become effective, or it may become more and +more effective, but then become harmful. + +Another example is from chemistry. When a system of chemicals reaches a certain level of interaction, the system undergoes a dramatic change. A small change in a factor may have an unnoticeable effect but a +further change may cause a system to reach a critical threshold making the system work better or worse. + +A system may also reach a threshold when its properties suddenly change from one type of order to another. For example, when a ferromagnet is heated to a critical temperature it loses its magnetization. As it +is cooled back below that temperature, magnetism returns. + +A company may reach a certain critical size and get advantages of scale in + +131 + +This means that 8 ice cubes have a surface area of 48 (8 x 6) versus 24 for the larger ice cube. This also means that 8 small ice cubes melt faster than one large ice cube, since the amount of heat an ice +cube can absorb depend on its surface area (the melting process occurs at the surface). Whenever we make objects smaller, we get more surface area per unit volume. For example, since iron rusts when exposed +to air and rusting occur at the surface, a steel knife rusts more slowly than steel wool. + +Why did the dinosaurs have such small heads in relation to their bodies? + +Living things are shaped and constrained by basic mathematical principles. Weight depends on volume and strength or load-bearing ability on area. The strength of a muscle or a bone is a function of +cross-section area. Strength does not increase at the same rate as weight and volume. When we increase size, weight increases faster than strength. Scale up an organism and sooner or later it will be too weak +to support its own weight. Double the size of a small dinosaur - twice as long, wide and high - and it weighs 8 times as much as before. We now need a neck that is 8 times stronger than before since it must +hold 8 times the weight. But since the strength of the neck is proportional to its cross-section area, the neck is only 4 times stronger. There comes a point where the neck breaks. + +What about the giants we see in the movies? + +Assume we make a human 10 times larger than normal. This means he is now 10 times longer, 10 times wider, and 10 times higher. He now weighs 1,000 times more but he is only 100 times stronger (as muscular +strength is proportional to the cross section area of a muscle). Since the load-bearing capacity of bones scales in the same manner his bones would be subject to ten times more stress than normal. He needs +thicker bones to support more weight. Otherwise his legs will crush. This is why elephants have such thick stumpy legs to support their weight. The giant has 1,000 times more meat on the body but only 100 +times the skin to hold it together meaning ten times the pressure on its skin (since pressure is proportional to area). This also means that his skin surface area is too small to remove the heat emitted from +his huge body. He would suffer from overheating since the amount of heat his body produces is proportional to the cube of his length (1,000), while the amount of heat he dissipates through the skin is +proportional to the square of his length (100). + +The British biologist Sir D'Arcy Wentworth Thompson said in On Growth and Form: "Everywhere nature works true to scale, and everything has its proper size accordingly. Men and trees, birds and fishes, stars +and star-systems, have their + +130 + +appropriate dimensions, and their more or less narrow range of absolute magnitudes." + +Some things in nature have about the same shape or pattern regardless of the scale we view them. Asmall part of a cauliflower looks much the same as the entire flower. Other examples include clouds, ferns, +snowflakes, river networks, systems of blood vessels and the structure of coastlines. + +'John needs to hire a new assistant and ask his boss: 'Do I have your OK? Adding + +$20,000 to the payroll should be inconsequential."' + +The concept of scale also applies to time - how things change over time or when something is repeated. What would Warren Buffett have told John? "The proposal should be evaluated as a $3 million decision, +given that an additional person would probably cost at least that amount over his lifetime, factoring in rises, benefits and other expenses." + +Small, slow changes operating over long periods can have great consequences. For example, we have seen how small genetic changes can have major anatomical effects over time. + +Breakpoints, critical thresholds and limits + +At a certain scale, a system reaches a critical mass or a limit where the behavior of the system may change dramatically. It may work better, worse, cease to work or change properties. + +Small interactions over time slowly accumulate into a critical state -where the degree of instability increases. A small event may then trigger a dramatic change like an earthquake. + +A small change may have no effect on a system until a critical threshold is reached. For example, a drug may be ineffective up until a certain threshold and then become effective, or it may become more and +more effective, but then become harmful. + +Another example is from chemistry. When a system of chemicals reaches a certain level of interaction, the system undergoes a dramatic change. A small change in a factor may have an unnoticeable effect but a +further change may cause a system to reach a critical threshold making the system work better or worse. + +A system may also reach a threshold when its properties suddenly change from one type of order to another. For example, when a ferromagnet is heated to a critical temperature it loses its magnetization. As it +is cooled back below that temperature, magnetism returns. + +A company may reach a certain critical size and get advantages of scale in + +131 + +experience, purchasing, marketing, manufacturing, administration, research, logistics, distribution, etc. For example, expenses can be spread out over larger amounts of volume, lowering average costs. These +advantages often permit greater specialization, making people better at what they do. + +Scale matters, says Warren Buffett discussing the private jet company NetJets®: + +Both we and our customers derive significant operational benefits from our being the runaway leader in the fractional ownership business. We have more than 300 planes constantly on the go in the U.S. and can +therefore be wherever a customer needs us on very short notice. The ubiquity of our fleet also reduces our "positioning" costs below those incurred by operators with smaller fleets. These advantages of scale, +and others we have, give NetJets a significant economic edge over competition. + +Charles Munger tells us about another kind of advantage of scale: + +In some businesses, the very nature of things is to sort of cascade toward the overwhelming dominance of one firm. The most obvious one is daily newspapers. There's practically no city lefr in the U.S., aside +from a few very big ones, where there's more than one daily newspaper ... Once I get most of the circulation, I get most of the advertising. And once I get most of the advertising and circulation, why would +anyone want the thinner paper with less information in it? So it tends to cascade to a winner-take-all situation. + +"We increased production volume but employee focus, service, and motivation went down." + +At some point the disadvantages of business size may eat into the advantages. For example, increased costs and investments, per-unit cost increases, systems become too complicated, bureaucratic and +inefficient, etc. + +People's behavior may change when we change the scale of a group. What works well in a group of one size may not work at all in a group of another size. Garrett Hardin illustrates this as he examines the +religious Hutterite communities in the northwestern U.S.: + +As a colony grows in size, the propensity of the individual to claim a share of production "according to his needs" increases, while his eagerness to work "according to his ability" diminishes. The +effectiveness of the overseers (preachers or bosses) also diminishes. Then, as shrinking increases, those less inclined to "goof off" begin to envy the brotherhood of drones, whom they presently join. + +132 + +The Hutterites learned that scale or the number of people in each decision unit is important. Up to 150 people per colony, the system can be managed by the force of shame. Above this size an appeal to +conscience loses its effectiveness and individuals begin to need more than they contribute. Studies show that groups of about 150 individuals are common in clans of hunter-gatherers, and military units. The +spread of behavior and ideas depends on scale. A certain proportion or minimum number of people (a threshold) must make a choice before we follow their lead. Some examples are whether to join a strike or +riot, adopt an idea, buy a product or stock, speak out on an issue, or leave a boring party. A critical + +threshold may cause massive social imitation. + +Consider technological, physical, human, biological and mathematical constraints and limits. We can't send signals faster than the speed of light. There are limits to how small or large something can be. +Gordon Moore, one of the founders oflntel, predicted in 1965 that the number of transistors that could be economically produced and placed on a silicon chip would double every 18 months. In 1995 he updated +his prediction to once every two years. Eventually though, physical, engineering or economic limits may stop this from happening. + +Size and frequency + +Small earthquakes are common while big ones are rare. + +Statistics show that the frequency of some events and attributes are inversely proportional to their size. Big or small things can happen but the bigger or more extreme they get, the less frequent they are. +For example, there are a few large earthquakes, fires, avalanches, or cities, but many small ones. There are a few billionaires but many millionaires. + +The size and frequency of these events and attributes has a statistical pattern - a scaling relationship that is about the same independent of size (we saw earlier that there is a scaling relationship between +the length of the ice cube's sides and its volume). For example there is a scaling relationship between earthquake magnitude and frequency. Based on observations from 1990, U.S. Geological Survey estimates +the average annually frequency of magnitude 8 and higher earthquakes to 1, magnitude 7-7.9 to 17, magnitude 6-6.9 to 134, and magnitude 5-5.9 to 1319 earthquakes. Still, the patterns are based on past +statistics and estimates. They don't help us to precisely predict future events. For example, catastrophes occur randomly. We don't know when the next big one will occur. + +85% of the profits ftom the division came ftom 25% of the products. + +The Italian economist and sociologist Vilfredo Pareto noted that 80% of his peas + +133 + +were produced by only 20% of the peapods. He also observed that 20% of the people owned 80% of Italy's land. Often a few things cause much of an effect. For example, a few defects produce most of the problem, +or a few individuals cause most of the problems. A few criminals commit most of the crime. It is estimated that about 5% of movies earn about 80 to 90% of profits in the movie industry. This unevenness is +also common in many other situations like healthcare spending, accidents, or book sales. + +Warren Buffett says: "It is not necessary to do extraordinary things to get extraordinary results." A few products or a few customers produce most of the profit or a few in the sales staff produce most of the +sales. In many business activities a few things can produce much of the value. Ask: How do we allocate our time, work, attention and money? Can we identify the few things that really matter? + +Constraints + +''Increase production!" + +Optimization of one variable may cause the whole system to work less efficiently. Why? The performance of most systems is constrained by the performance of its weakest link. A variable that limits the system +from achieving its goal or optimum performance. An increase in production may for example be physically constrained by the production capacity on one of the machines. If one machine in a production line of +two machines can produce 100 items and the second 90, the output is physically constrained by the second machine. + +What do we want to achieve? What will prevent this from happening? Why? + +When trying to improve the performance of a system, first find out the system's key contraint(s) - which may be physical (capacity, material, the market) or non physical (policies, rules, measurements) - and +its cause and effect relationship with the system. Maybe the constraint is based on faulty assumptions that can be corrected. Then try to "strengthen" or change the weakest link. Watch out for other effects - +wanted or unwanted - that pop up as a consequence. Always consider the effects on the whole system. + +134 + +- THREE - + +CAUSES + +"We measure and reward performance by the quantiry of steel produced. " + +What do we want to accomplish? It's hard to achieve a result if we don't understand what causes the result to happen. In order to solve problems or achieve goals, we must first understand what causes the +result we want to accomplish. Start with examining what factors make up the system and how they connect. Then, define the key factors that determine outcome. + +If a business measures performance by the amount of steel produced, they will + +get a lot of steel produced. But the amount of produced kilo steel is only one part of the equation. It's better to ask: What is the equation that achieves what we want to accomplish? What factors cause what +we want to achieve? Under what circumstances? What causes business value? Do we have the factors needed? What must be changed in the equation to achieve what we want? Have we thought through what other +effects our actions may have? + +Large effects + +A bird flies into the engine of an aircraft and disaster strikes. + +We believe that cause resembles its effect - for example, that large or important effects must have large causes or that complicated outcomes have complicated underlying reasons. But the size of an effect may +not be proportional to its cause. Small things may break a large system. In 1988, 35 people died and 113 were injured when a London-bound commuter train crashed into the back of a stationary train. The +accident was caused by faulty wiring work. A mechanic worked more than 12 hours with only a 5-minute break and forgot to remove a small wire from an old switch when installing a new rail signaling system. + +On September 23, 1999, the Mars Climate Orbiter spacecraft disappeared + +What happened? The core cause was the failed conversion of English units (pounds) to metric units (newton). The manufacturer measured the force of small control thrusters in pounds but the space officials +expected newtons. A misunderstanding that sent the spacecraft about 56 miles too close to Mars, making it disappear into the Martian atmosphere. A simple mistake caused the loss of a $125 million spacecraft. + +135 + +Washing hands save lives. + +Dirty hands can cause major health problems. Among bacteria that reproduce by dividing themselves every half hour, a single one can generate about 17 million offspring within 12 hours. Records at the Center +for Disease Control and Prevention (CDC) show that every year close to 2 million people (out of 35 million admissions annually) in the U.S. pick up an infection in the hospital. Of those people, about 90,000 +die as a result of their infection. And the major reason is bad hygiene like unsanitary conditions, germ-laden instruments and unwashed hands. CDC and the U.S. Department and Health and Human Services +estimate that strict adherence to clean-hand policies alone could save the lives of 20,000 patients. That washing hands saved lives was discovered in 1847 by the Hungarian gynecologist Ignaz Philipp +Semmelweis. When working at the Maternity Department of the Vienna Hospital, he observed that women delivered by medical students had high mortality rates while those delivered by midwife trainees had low +rates of childbed fever. The difference? The medical students had made pathological dissections, or had come into contact with dead bodies before the examination of the women. Semmelweis introduced the +practice of washing hands in a solution of chlorinated lime before every examination and mortality + +rates plummeted. + +Random events + +'.11. fire in our supplier's factory caused delivery problems of components. We lost market share to competition, which resulted in huge losses. This outcome was unforeseeable since we couldn't have predicted +the fire in advance. " + +When bad things happen, we try to find causal explanations or something to blame. The more unexpected or negative we find an event, the more likely we are to look for explanations. We underestimate the +influence of randomness. + +Here we define a random event as an event that can't be predicted because of a lack of knowledge. An event is random when we don't have enough information to determine its outcome in advance. + +Acting on symptoms + +Take away the cause, and the effect ceases. + +- Miguel De Cervantes (from Don Quixote) + +Sometimes we mistake an effect for its cause. There is a story about a man that was walking by a river when suddenly a screaming girl floated by. The man jumped in the river and saved her. After five minutes, +another screaming girl + +136 + +floated by. He jumped in again and saved the girl. The same thing happened over and over again. The problem was a little further up the river. There was a man throwing girls from a bridge. Our hero solved the +symptoms but not the cause of the problem. + +"We have tons of problems. We are losing customers, we can't deliver on time, our inventory system doesn't work. " + +What is the core cause of these problems? Many times when we have a lot of problems, there may be one common reason for them all. When dealing with problems we must focus on what we want to achieve and make +sure that we address the underlying cause and not act on symptoms that may look like causes. Maybe the symptoms were due to wrong policies or measuring instruments or goals, etc. + +Multiple causes + +We attribute an outcome to a single cause when there are multiple causes. We assume that A causes B but A may not be the only thing that causes B. There may be many causes for a given effect. + +For example, behavior is determined by a multitude of psychological and non psychological factors, individual characteristics and the given situation. Sometimes these factors interact and reinforce each +other. When explaining behavior, think in terms of multiple causes. For example, Charles Munger says on the Milgram experiment discussed in Part Two (where a group of research subjects delivered electric +shocks simply because they were told to do so by an authoritative figure): + +For years it was in the psychology books as a demonstration of authority- how authority could be used to persuade people to do awful things. Of course, that's mere first conclusion bias. That's not the +complete and correct explanation. Authority is part of it. However, there was also quite a few other psychological principles [consistency, contrast, reason-respecting], all operating in the same direction, +which achieved that lollapalooza effect precisely because they acted in combination toward the same end. + +Mistaking correlation for cause + +Correlation means a relationship or association between two or more variables. We tend to assume that when two things happen together, that one causes the other. That a change in one variable is strongly +correlated or followed by a change in another doesn't automatically mean that one causes the other. Some third factor may cause them both. Assume we detect a high correlation between money + +137 + +and happiness. But that doesn't tell us if money causes happiness, if happiness causes money, or if some third factor causes them both. + +An example of statistical misuse is from 1992 when it was reported that 28 teenagers who frequently played the game of "Dungeons and Dragons" (D&D) committed suicide. What conclusion should be drawn? Is there +a link between teenage suicide and the game? + +The American mathematician John Allen Paulos tells us in Innumeracy to put this statement into the right perspective by considering two more facts. The game sold millions of copies and about 3 million +teenagers played it. In that age group the annual suicide rate is about 12 people per 100,000. This means chat we can expect 360 D&D playing teenagers (12/100,000 x 3 million players) to commit suicide. + +Alternative explanations + +''Mary has a fever and therefore she has a cold. " + +There may be many explanations for a given outcome. But we often jump to conclusions and fail to consider alternative explanations. A given effect may be consistent with a range of causes and don't help us +find the core cause of a problem. + +That Mary has a fever tells us that she is not well but it doesn't tell us why she is ill. Fever can occur from a range of diseases. Ask: What else can explain this outcome? + +Selective data and appropriate comparisons + +There is nothing more deceptive than an obvious fact. + +Sherlock Holmes (Arthur Conan Doyle, The Boscombe Valley Mystery) + +We identify the wrong cause because it seems the obvious one based on a single observed effect. As Bertrand Russell says: "Obviousness is always the enemy to correctness." + +When someone remarked to the French writer Voltaire, "Life is hard," he retorted, "Compared to what?" We tend to ignore alternatives, and therefore we fail to make appropriate comparisons. Often we only +consider information or evidence that is presented or available and don't consider that information may be missing. + +"By studying successful businesses, I have found that their secret to success is focus," said the CEO ofTransCorp. + +But many failed businesses also had focus. Is success, then, due to strong culture, visionary leaders, or something else? Maybe failed enterprises also had strong + +138 + +cultures and visionary leaders. To understand what qualities cause success, we need to compare business successes with failures. We must include companies that started with the same quality but failed. The +problem though, is that the data for failures often disappears. Furthermore, what works in one situation may fail in another. + +By interviewing survivors of fatal airline accidents, a 1986 Discover article presented some tips on how we could improve our chances of surviving plane crashes. But as noted by Psychology Professor Robyn +Dawes, there was no evaluation of what percent of all passengers did what the survivors did. Maybe those who died also had done the same. Of course, we can't interview the passengers who didn't survive. + +Often the same attributes are used to explain both success and failure. For example, when a company is successful, the media say that it is because of its focus and great leadership. When performance goes +down, they report that the company became less focused and its leadership deteriorated. While there may be evidence that the company is less focused or has worse leadership than before, it could just as well +be that the competition has gotten better. Business performance is relative, not absolute. The performance of a business is always influenced by what its competitors do. Even if a company gets better in many +areas, market share and profits may decline if the competition does things even better. And even if a company gets worse in many areas, market share and profits may increase if competition does things even +worse. + +"Look at where the bullet holes are and put extra armor every place else. " + +During World War II, the statistician Abraham Wald tried to determine where one should add extra armor to airplanes. Based on the patterns of bullet holes in returning airplanes, he suggested that the parts +not hit should be protected with extra armor. How could he reach that conclusion? Because he also considered planes that didn't return. Assume that all planes had been hit more or less uniformly. Some planes +hit in marked areas were still able to return. This means that planes that didn't return were most likely hit somewhere else - in unmarked places. These were the areas that needed more armor. + +"The drug obviously worked since I used it and got better. " + +But the same outcome could have happened without taking the drug. We need to consider both confirming and disconfirming evidence. Ask: What is the frequency of supporting cases compared to disconfirming +cases? What is the relative frequency of this condition or disease in the population? + +For example, when studying the effectiveness of a new treatment, people often + +139 + +ignore the outcome of a non-treatment, and focus only on a large number of successful treatments, and therefore conclude that the treatment is effective. But we also have to look at the number of people who +a) use the treatment and don't improve, b) don't use the treatment and improve, and c) don't use the treatment and don't improve. + +In one study people were asked to judge the effectiveness of a treatment based on the following data from an experiment: + +Treatment No treatment + +Improvement 200 people + +50 + +No improvement 75 + +15 + +Most subjects believed the treatment was effective. But it is rather ineffective. Why? We need to compare the outcome for the no treatment group with the outcome for the treatment group. 50 of 65 people +(50+15) or about 77%, improved without any treatment versus 200 of 275 (200+75) people or about 73% who improved with the treatment. + +Psychology Professor Thomas Gilovich says in How We Know What Isn't So: "With the body so effective in healing itself, many who seek medical assistance will experience a positive outcome even if the doctor +does nothing beneficial. Thus, even a worthless treatment can appear effective when the base-rate of success is so high." + +What caused customer complaints at TransCorp? + +We look for obvious causes and look at the conditions and behavior that were present in the particular situation after we know what happened. But we should observe what is normally happening. Most outcomes +are context-dependent. + +Instead of concentrating on conditions, and behavior preceding the customer complaint, TransCorp should examine both sales without complaints and with complaints and ask: What were the underlying conditions +and behavior when customers didn't complain? Are there differences that can explain the complaints? For similar situations, ask: Compared with what? Compare negative outcomes with positive. What factors +differ? What were the underlying conditions and behavior where something bad happened compared to the conditions and behavior when things worked? What differentiates the situations? Don't draw + +conclusions from what may have been a unique or random event. + +140 + +- FOUR - + +NUMBERS AND THEIR MEANING + +Use basic math to count, quantify, and understand relationships + +john bought all the stock he could since it was priced at only $1. + +Something is only cheap or expensive in relation to something else. If an investor refers to a stock as "cheap," what is it cheap in relation to? 100,000 shares of stock priced at $1 have the same market +valuation as 1,000 shares priced at $100. The relevant question is: What is the company worth in relation to its price? + +TransCorp made a "huge" $1 billion in profits. + +Words like "big" or "small" have no meaning in themselves. A number has only a size in relation to another number. $1 billion says nothing about economic performance unless we compare it with how much capital +was needed to generate it. What ifTransCorp needed $100 billion in equity and debt to run the business? That's only a 1% return. + +"Research shows that the new drug reduces the risk ofgetting the disease by 25%." What benefits can be expected by taking the new drug? Assume statistics show the following: Without the drug 20 people in +1,000 get the disease. By taking the drug, the figure drops to 15 people in 1,000. How efficient is the drug if we look at the absolute number of people saved from the disease? The reduction in absolute risk +is 5 people in 1,000 (20-15) or 0.5%. The reduction in relative risk or the relative number of people saved from the disease is 25% (5/20). A 25% reduction only means something if many people are saved. + +How many people need to take the drug in order to save one individual from the disease? Since 5 people in 1,000 (or 1 in 200) are saved from the disease by taking the drug, only one person out of 200 that +take the drug will be saved. For the other 199 people the drug does not have any positive effect. + +How do we know that research findings are true? Surveys of epidemiological studies (studies of factors affecting health and illness) show that many researchers' claims don't replicate in medical trials +because of bias and random error. For example, two refuted claims are that aspirin is highly protective against heart disease in both men and women and that vitamin E reduces the + +141 + +chance of cardiovascular mortality. Studies by Hygiene and Epidemiology Professor John Ioannidis show that the smaller the studies; the smaller the effect sizes; the hotter the field; the greater the +interest; the larger the databases; and the greater the flexibility in analyses, the higher the chance that a research claim is false. True replication is the cornerstone of science, and assuming that biases +are weeded out, the more researchers reproduce a finding, the better chance it has of being true. + +What does it mean that our sun is 93 million miles away? + +Often we need to translate a number to something more understandable. Light travels at an average speed of 186,281 miles per second. This means that it takes sunbeams about 8 minutes to reach the earth. The +star Alpha Centauri is 4.35 light-years away. A light-year is the distance light travels in one year. Even iflight year measures distance, it implies time. If we were to ride on a beam of light, it would take +us 4.35 years to reach our closest star. When we look up in the sky we see the past - the star as it appeared 4.35 years ago. + +Always look at what numbers mean. For example, ask: Does the magnitude make sense? In relation to what? Also, think about what counts - not how it is counted. There was a sign hanging in the physicist Albert +Einstein's office at Princeton that said: "Not everything that counts can be counted, and not everything that can be counted counts." + +The effect of exponential growth + +john's son David made a proposal '1 take out the garbage every day for a month, and you only have to pay me a penny today and then every day afterward I want double as much as I got the day before. " + +The sequence of numbers 2, 4, 8, 16 grows exponentially. Day 2 his son would have 2 cents, day 3, 4 cents. After 27 days, he would have $1.3 million dollars. The individual growth is constant - 100% a day- +but the sum gets higher faster and faster. This is the power of doubling. + +As we have seen there are limits to prolonged growth. Take bacteria as an example. Assume that a certain strain of bacteria divide in one minute. We put the bacteria in a bottle at 11 am and the bottle is +full at noon. When was the bottle half full? - 11 :59 am. Just one minute earlier. + +Even a small number of steady growth leads eventually to doubling and redoubling. For example, a country whose population grows by 2% a year, double in size in 35 years and redoubles in 70 years. A simple +formula for doubling time is found by dividing 70 by the percent growth per year. + +142 + +Compounding refers to "interest on interest." If we invest $1,000 with a return of 6% a year, we receive $60 in the first year. If we reinvest that $60, next year we get another $60 from our original $1,000 +investment, plus $3.6 from the $60 we reinvested. If we reinvest all our returns, the total value of our original $1,000 investment after 5 years is: $1,000 x 1.06 x 1.06 x 1.06 x 1.06 X 1.06 = $1,338. + +Time is the key to compound interest. Over short periods, compounding produces a little extra return. Over long periods, it has an enormous effect. Invest + +$2,500 each year for 40 years at 10% return and you will be a millionaire. + +The time value of money + +A bird in the hand is worth two in the bush. + +-Aesop + +Why must we reduce the value of money we receive in the future? + +Money paid in the future is worth less than money paid today. A dollar received today is worth more than a dollar received tomorrow. If we have a dollar today, we can invest it and earn interest making that +dollar worth more than a dollar in the future. This means that money has a price and that price is interest. + +How much should we pay today for the right of receiving $1,000 a year from now? Or, how much do we need to invest today in order to have $1,000 a year from now? It's the same question. The answer depends on +the interest rate. If the rate is 6%, then the answer is $943. If we invest $943 today at 6%, we have $1,000 one year from now. $943 is the present value of $1,000 a year from now. We have discounted or +reduced $1,000 to its value today. The further out in time we receive the $1,000 or the higher the interest rate is, the less the present value is. + +143 + +- FIVE - + +PROBABILITIES AND NUMBER OF POSSIBLE OUTCOMES + +Probability is the very guide of life. + +Marcus Tullius Cicero + +How likely do we believe it is that some event will occur? Probabilities are like guesses. But as Richard Feynman said in his Caltech Lectures on Physics: "There are good guesses and there are bad guesses. +The theory of probability is a system for making better guesses." + +We can either estimate the probability based on its relative frequency (proportion of times the event happened in similar situations in the past) or we can make an educated guess using past experiences or +whatever important and relevant information and evidence that is available. + +We can also count possible outcomes. The only time we can calculate the exact probability of an event in advance (over a large number of trials) is in cases where we know all possible outcomes and where all +outcomes are equally likely. This is applicable for games of chance such as tossing a coin or rolling a die. However we use the notion of probability, we need to follow its basic rules. + +How like/,y is it that a hurricane strikes Texas? + +According to the National Hurricane Center, there have been 36 hurricane strikes in Texas from 1900 to 1996. Based on past experience and barring no change in conditions, we can estimate that there is about a +37% (36/97) chance that a hurricane will strike Texas in any given year. This figure - 36/97 - is also called the base rate frequency of outcomes (hurricanes in Texas). + +We must make sure that the conditions that produced the relative frequency can be expected to be pretty much the same before we can use it as a guide for the future. We must also look at variations of outcome +and severity (how much damage an event may cause). Take tornadoes as an example. According to the National Climatic Data Center, between 1950 to 1999 there has been an average of 810 tornadoes yearly in the +U.S. But in 1950 there was 201 tornadoes (causing 70 deaths), in 1975, 919 (causing 60 deaths), and in 1999, 1,342 tornadoes (causing + +94 deaths). + +144 + +A doctor says, "This is the first time I've seen this disease. I estimate there is a 50-50 chance that the patient will survive. " + +This statement has only two possible outcomes. Either the patient dies or not. Does it really make any sense to say "a 50-50 chance" if there are no past data or other evidence to base the probability on? +Does it really tell us something? If there are no historical, comparable or representative data or other evidence to base an estimate on, the probability figure only measures the doctor's belief in the +outcome of the event. + +Another doctor says, "According to medical records of similar cases, under the same conditions, 50% of the patients survived five years or longer." + +The more representative background data or evidence we have the better our estimate of the probability. + +To narrow down the probability figure even more, we need a relevant comparison group, i.e., a group to which a frequency refers. In the hurricane example, we defined the probability for a specific comparison +group, referring to the relative frequency with which hurricanes have occurred (37 times in Texas during the 97 years for which we have data). + +Events may happen with great frequency or rarely. Some events are not repeatable and some events have never happened before. For certain events, past experience may not be representative. Others are +characterized by low past frequency and high severity. Unforeseen events occur where our actual exposure (measures vulnerability and potential cost or loss) is unknown. Sometimes people react to an event by +avoiding or preventing it in the future causing a change of the events future probability. Other times one bad event may increase the chance of another. For example, an earthquake may cause landslides, +floods, or power blackouts. The more uncertainty there is, the harder it is to find a meaningful probability number. Instead our estimate must be constrained to a range of possible outcomes and their +probabilities. + +Uncertainty increases the difficulty for insurers to appropriately pnce catastrophes, such as hurricanes or earthquakes. Warren Buffett says: + +Catastrophe insurers can't simply extrapolate past experience. If there is truly "global warming," for example, the odds would shift, since tiny changes in atmospheric conditions can produce momentous changes +in weather patterns. Furthermore, in recent years there has been a mushrooming of population and insured values in U.S. coastal areas that are particularly vulnerable to hurricanes, the number one creator of +super-cats. A hurricane that caused x dollars of damage 20 years ago could easily cost 1Ox now. + +145 + +Occasionally, also, the unthinkable happens. Who would have guessed for example, that a major earthquake could occur in Charleston, S.C.? (It struck in 1886, registered an estimated 6.6 on the Richter scale, +and caused 60 deaths.) + +But it may still be possible to price sensibly. Warren Buffett says: + +Even if perfection in assessing risks is unattainable, insurers can underwrite sensibly. After all, you need not know a man's precise age to know that he is old enough to vote nor know his exact weight to +recognize his need to diet. + +Warren Buffett also considers a worst case scenario: + +Given the risks we accept, Ajit [Ajit Jain; manager of Berkshire's reinsurance operations] and I constantly focus on our "worst case," knowing, of course, that it is difficult to judge what this is, since you +could conceivably have a Long Island hurricane, a California earthquake, and Super Cat X all in the same year. Additionally, insurance losses could be accompanied by non-insurance troubles. For example, were +we to have super-cat losses from a large Southern California earthquake, they might well be accompanied by a major drop in the value of our holdings in See's, Wells Fargo and Freddie Mac... + +We do, though, monitor our aggregate exposure in order to keep our "worst case" at a level that leaves us comfortable. + +How reliable is past experience for predicting the future? In Against the Gods, Peter Bernstein refers to a 1703 letter written by German mathematician Gottfried Wilhelm von Leibniz to the Swiss scientist and +mathematician Jacob Bernoulli referring to mortality rates: "New illnesses flood the human race, so that no matter how many experiments you have done on corpses, you have not thereby imposed a limit on the +nature of events so that in the future they could not vary." Even with the best empirical evidence, nobody knows precisely what will happen in the future. + +After the September 11, 2001, catastrophe, Warren Buffett wrote on the importance on focusing on actual exposure and how using past experience sometimes may be dangerous: + +In setting prices and also in evaluating aggregation risk, we had either overlooked or dismissed the possibility oflarge-scale terrorism losses... In pricing property coverages, for example, we had looked to +the past and taken into account only costs we might expect to incur from windstorm, fire, explosion and earthquake. But what will be the largest insured + +146 + +property loss in history (after adding related business interruption claims) originated from none of these forces. In short, all of us in the industry made a fundamental underwriting mistake by focusing on +experience, rather than exposure, thereby assuming a huge terrorism risk for which we received no premium. + +Experience, of course, is a highly useful starting point in underwriting most coverages. For example, it's important for insurers writing California earthquake policies to know how many quakes in the state +during the past century have registered 6.0 or greater on the Richter scale. This information will not tell you the exact probability of a big quake next year, or where in the state it might happen. But the +statistic has utility, particularly if you are writing a huge statewide policy... + +At certain times, however, using experience as a guide to pricing is not only useless, but actually dangerous. Late in a bull market, for example, large losses from directors and officers liability insurance +("D&O") are likely to be relatively rare. When stocks are rising, there are a scarcity of targets to sue, and both questionable accounting and management chicanery often go undetected. At that juncture, +experience on high-limit D&O may look great. + +But that's just when [3mexposure [0mis likely to be exploding, by way of ridiculous public offerings, earnings manipulation, chain-letter-like stock promotions and a potpourri of other unsavory activities. When +stocks fall, these sins surface, hammering investors with losses that can run into the hundreds of billions. + +Even if we for some events can't estimate their probability, there may be some evidence telling us if their probabilities are increasing or decreasing. Ask: Do I understand the forces that can cause the +event? What are the key factors? Are there more opportunities for the event to happen? + +Warren Buffett says on terrorism: + +No one knows the probability of a nuclear detonation in a major metropolis area this year... Nor can anyone, with assurance, assess the probability in this year, or another, of deadly biological or chemical +agents being introduced simultaneously... into multiple office buildings and manufacturing plants... + +Here's what we do know: a. The probability of such mind-boggling disasters, though + +likely very low at present, is not zero. b. The probabilities are increasing, in an irregular and immeasurable manner, as knowledge and materials become available to those who wish us ill. + +The more opportunities (possible wanted or unwanted outcomes) an event has to happen in relation to what can happen (all possible outcomes), the more likely it is to occur. + +147 + +Number of possible outcomes + +Toss a coin once. What can happen? There are 2 possible outcomes. Roll a die once. There are 6 possible outcomes. All equally likely. Roll a die twice. What can happen? There are 6 possible outcomes on each +roll and therefore 36 possible combinations or outcomes when rolling a die twice. Roll a die 3 times. There are 216 possible outcomes. + +This is a simplified way of saying that the more possible outcomes an event has (in number or time), the less likely a specific outcome is (for example only one outcome satisfies the wanted event: "roll a die +once and observe a six") and the more likely some outcome is (there are 6 possible outcomes to choose from). The more possible outcomes a specific event has, and the more they are unwanted, and the more +independent events that are needed to achieve a scenario, the less likely it is that the wanted scenario happens. Some outcomes + +may be less likely than others (for example, due to constraints or limits). + +Treat rolling a die 3 times as 3 separate events where each event is "observe a six". What we see from the above is that the more events that must happen to achieve some scenario or wanted outcome ("3 sixes +in a row"), the less likely the scenario is to happen. Observing "anything but 3 sixes in a row" is an unwanted event. There are 215 outcomes or ways for this unwanted event to happen out of + +216. This means that it is very likely that the unwanted event happens. + +We talk about what is likely to happen in the long run. We might be lucky and roll 3 sixes in a row. We must also consider the consequences of an unwanted outcome. + +What does this mean? If there are more ways of reaching a bad outcome than + +a good outcome, the probability of a bad outcome is higher. It is easier to destroy a system than to create one merely because there are more opportunities for destruction than creation. + +It means that surprises, coincidences, rare events and accidents happen, somewhere, sometime, and to someone if they have opportunities to happen. + +It also means that eliminating risk is preferable to finding out where the risk lies (since there are so many opportunities for an unwanted outcome). For example, we can reduce risk by increasing the number +of wanted possible outcomes, reducing the number of unwanted possible outcomes, reducing the magnitude of consequences or avoiding certain situations. + +Ask some relevant questions: + +Event: Type of event? Frequent? Unique? + +Causes: What can initiate and cause the event? What factors contribute? What conditions and circumstances must be present? Have the causes changed over time? + +148 + +Exposure: Known? Measurable? Possible consequences? Magnitude of consequences/loss? What's the worst that can happen? + +Probability: Distribution of possible outcomes over time? Stable? Relative frequency or relevant past experience? Number of observations? Relative likelihood of different size of losses? How is average +frequency produced? Variability in outcome and severity? Dependence on human factors? + +Representative: Past data representative or change in conditions? Evidence of changes in causes or frequency of event? Temporary or permanent change? Small sample or too short observation time? Changing +exposure as time proceeds? + +Backups: Backup failure rate? + +Let's observe some effects of what we've described in this chapter. More focus is put on the underlying ideas than the math. The theory of probability and its definitions, rules and calculations are found in +Appendix Three. + +Low frequency events + +The chance of gain is by every man more or less overvalued, and the chance of loss is by most men undervalued + +- Adam Smith (Scottish philosopher and economist, 1723-1790) + +Supreme Court Justice Oliver Wendell Holmes, Jr. said: "Most people think dramatically, not quantitatively." We overestimate the frequency of deaths from publicized events like tornadoes, floods and homicides +and underestimate the frequency of deaths from less publicized ones like diabetes, stroke and stomach cancer. Why? As we learned in Part Two, we tend to overestimate how often rare but recent, vivid or highly +publicized events happen. The media has an interest in translating the improbable to the believable. There is a difference between the real risk and the risk that sells papers. A catastrophe like a plane +crash makes a compelling news story. Highly emotional events make headlines but are not an indicator of frequency. Consider instead all the times that nothing happens. Most flights are accident-free. Ask: How +likely is the event? How serious are the consequences? + +john is boarding the day flight from Los Angeles to Washington and wonders, "How likely am I to die on this trip?" + +What is the risk of a disaster? First we need to know the available record of previous flights that can be compared to John's. Assume, we find that in 1 out of 10,000 flights there was an accident. The record +also shows that when an accident happens, on average 8 out of 10 are killed, 1 injured and one safe. This means that + +149 + +the chance that a passenger will be involved in an accident is 1 in 10,000; being killed, 1 in 12,500 (10,000/0.8); and being injured, 1 in 100,000 (10.000/0.1) + +According to the Federal Aviation Administration, Dr. Arnold Barnett of Massachusetts Institute of Technology (MIT), a widely recognized expert on air traffic safety, measured a passenger's odds of surviving +the next flight. It related the probability of not being in a fatal air carrier accident and the probability of not surviving if a fatal accident happens. In the year 2000 the odds were 5.8 million to 1. + +According to the National Transportation Safety Board the number of passengers killed in air accidents in the U.S. during 1992 through 2001 was 433 (including the 232 aboard the four hijacked flights on +September 11, 2001). For reference, in 2001, the annual number oflives lost in road traffic accidents in the + +U.S. was 42,119. + +That people feel safer driving than flying makes sense since we are oriented towards survival. As Antonio Damasio says in Descartes' Error, "Planes do crash now and then, and fewer people survive plane +crashes than survive car crashes." Studies also show that we fear harm from what's unfamiliar much more than mundane hazards and by things we feel we control. We don't feel in control when we fly. + +Why do we lose money gambling? Why do we invest in exotic long shot ventures? We often overestimate the chance of low probability but high-payoff bets. For example, how likely is it that anyone guesses a +number between 1 and 14 million? What is Mary's chance of winning "Lotto 6/49" if there are 14 million outcomes? What must happen? She must pick 6 numbers out of 49 and if they all match she wins. What can +happen? How many numbers can she choose from? The possible number of ways she can choose 6 numbers out of 49 is 13,983,816. The probability that someone chooses the winning combination is therefore one in +about 14 million. Merely slightly better than throwing heads on 24 successive tosses of a coin. + +Imagine the time it takes to put together 14 million combinations. If we assume every combination on average takes 1 minute to put down on paper, and Mary pick numbers for 24 hours a day, it will take her 27 +years to write them all down. + +Even if Mary invests $14 million to buy 14 million tickets in the hopes of winning a $20 million jackpot, she may have to share the jackpot with others that picked the winning number. If just one other person +picked the winning combination, she would lose $4 million (20/2- 14). + +150 + +Why do people play a game when the likelihood of losing is so high? Even if we exclude the amusement factor and the reinforcement from an occasional pay off, it is understandable since they perceive the +benefit of being right as huge and the cost of being wrong as low - merely the cost of the ticket or a dollar. Remember the advice of Benjamin Franklin: "He that waits upon fortune, is never sure of a +dinner." + +Mathematical expectation + +A lottery has JOO tickets. Each ticket costs $10. The cash price is $500. Is it worthwhile for Mary to buy a lottery ticket? + +The expected value of this game is the probability of winning (1 in 100) multiplied with the price ($500) less the probability of losing (99 out of 100) multiplied with the cost of playing ($10). For each +outcome we take the probability and multiply the consequence (a reward or a cost) and then add the figures. This means that Mary's expected value of buying a lottery ticket is a loss of about $5 (0.01 x $500 +- 0.99 x $10). + +We need to separate between few games and many games. Since probability means the number of times an event is likely to happen during a large number of trials, the expected value is the amount Mary should +expect to win or lose per game if she made the same bet many times. Expected value tells Mary that she on average should expect to lose $5 every time she plays if she plays the same lottery over and over. Not +what she can expect from a single game. Mary has a 1 + +% chance of winning the lottery and if she wins, her gain is $490. She has a 99 + +% chance oflosing $10. + +Most of our decisions in every-day life are one-time bets. Choices we face only once. Still, this is not the last decision we make. There are a large number of uncertain decisions we make over a lifetime. We +make bets every day. So if we view life's decisions as a series of gambles, we should use expected value as a guide whenever appropriate. Over time, we will come out better. + +John placed $38 dollar on the roulette tabk. + +Mathematics and human nature make it impossible for us to beat the roulette wheel for any considerable length of time. If we play at a casino once we may be lucky and in the short run win some money, but we +should expect to lose in the long run. The casino has the advantage. + +There are 38 different numbers (including double zero) on the roulette wheel. When the croupier spins the wheel there is an equal chance of the ball landing in any one of the 38 slots. John puts $1 on a +single number. If his number comes + +151 + +up, he wins $35. On average his expected value of a one dollar bet is a loss of 5.26 cents (1/38x$35 - 37/38x$1). Over the long run John loses an average of 5.26 cents for every dollar he places on the table. +The odds are set so they average out in the casino's favor. + +''If I just stay at the table long enough, the odds turn in my favor and I will win back everything I lost. " + +But this is what the casino wants us to believe. The casino can't predict the outcome of any particular bet but as soon as there are a large number of individual players making bets, the casino will make +money. As a casino operator said: "What I love is the risk. Some nights we make money, and other nights we make more money." + +Even if we win in the short run, human nature turns us into losers. Nearly all of those who win big continue to play until they have lost their gains, and perhaps more. This is well illustrated by Henry +Howard Harper in his book, The Psychology of Speculation: + +It is said to be a proven fact that the chances are so much against the player, that a roulette wheel can be run at a profit, even if the percentage in favor of the house is entirely eliminated. This is due +to the fact that the excitement of play causes a certain confusion of mind, and players are prone to do the wrong thing; for instance, double their bets when in an adverse run of luck and "pinch" them when +luck is running favorably. Or, on the other hand, players who have pressed their advantage and doubled in a run of favorable luck will continue stubbornly to plunge long after their luck has changed. +Precisely the same psychology applies to trading in stocks. + +Chance has no memory + +"My luck is about to change. The trend will reverse. " + +We tend to believe that the probability of an independent event is lowered when it has happened recently or that the probability is increased when it hasn't happened recently. For example, after a run of bad +outcomes in independent events that appear randomly, we sometimes believe a good outcome is due. But previous outcomes neither influence nor have any predictive value of future outcomes. There is neither +memory nor a sense of justice. + +Mary flipped a coin and got 5 heads in a row. Is a tail due? It must be, since in the long run heads and tails balance out. + +When we say that the probability of tossing tails is 50%, we mean that over a long + +152 + +run of tosses, tails come up half the time. The probability that Mary flips a head on her fifth toss is 50%. The coin has no sense of fairness. As the 19th Century French mathematician Joseph Bertrand said: +"The coin has neither memory or consciousness." Mary committed the gambler's fallacy. This happens when we believe that when something has continued for a certain period of time, it goes back to its long-term +average. This is the same as the roulette player when he bets on red merely because black has come up four times in a row. But black has the same chance as red to come up on the next spin. Each spin, each +outcome is independent of the one before. Only in the long run will the ratio of red to black become equal. + +Every single time Mary plays, the probability it lands on heads is 50% and lands on tails 50%. Even if we know that the probability is 50%, we can't predict if a given flip results in a head or tail. We may +flip heads ten times in a row or none. The laws of probability don't count out luck. + +"J got a speeding ticket yesterday, so now I can cross the speed limit again,"said john. Even criminals suffer the gambler's fallacy. Studies show that repeat criminals expect their chance of getting caught +to be reduced after being caught and punished unless they are extremely unlucky. + +Mary finds it comforting knowing it will take another 99 years until the next giant storm happen. + +What is a" 100-year storm?" To predict storms we look at past statistics i.e., how often in the recorded past a storm of a certain magnitude has occurred. We also assume that the same magnitude of storm will +occur with the same frequency in the future. A 100-year storm doesn't mean it happens only once every 100 years. It could happen any year. If we get a once in 100-year storm this year, another big one could +happen next year. A 100-year event only means that there is a 1% chance that the event will happen in any given year. So even if large storms are rare, they occur at random. The same reasoning is true for +floods, tsunamis, or airplane crashes. In all independent events that have random components in them, there is no memory of the past. + +Controlling chance events + +The craps table was filled with people tossing their die soft and asking for a low number. + +We believe in lucky numbers and we believe we can control the outcome of chance events. But skill or effort doesn't change the probability of chance events. + +153 + +"Change tickets! Are you crazy! I would feel awfol if my number comes up and I'd traded it away. " + +In one experiment a social psychologist found that people were more reluctant to give up a lottery ticket they had chosen themselves, than one selected at random for them. They wanted four times as much money +for selling the chosen ones compared to what they wanted for the randomly selected ticket. But in random drawings it doesn't make any difference if we choose a ticket or are assigned one. The probability of +winning is the same. The lesson is, if you want to sell lottery tickets, let people choose their own numbers instead of randomly drawing them. + +Gains, losses and utility + +The 18th Century Swiss mathematician Daniel Bernoulli said: ''A gain of one thousand ducats is more significant to a pauper than to a rich man though both gain the same amount." This means that the utility or +personal value of an outcome differs for different people and at different stages in life. For example, our preferences change as our state of wealth changes. + +Often when we make financial decisions we don't consider our total wealth. Instead we judge a decision by evaluating changes measured in terms of short term gains and losses. + +"Should I invest?" + +"There is a 50% probability that I gain $10,000. There is a 50% probability that I lose $4,000. " + +"Since I get pleasure from gains and the expected value ($3,000} is positive, I decide to invest." + +Instead we should take a more long-term view and think in terms of wealth. We should add our current wealth to all possible financial outcomes and choose the alternative that has a higher expected utility +(considering our own psychological nature, talent and goals). + +''My present wealth is $1,000,000. Do I choose $1,000,000 for sure or $996,000 or + +$1,010,000 with equal probabilities?" + +"Since the expected utility resulting from integrating the favorable investment with my wealth is lower than the expected utility of my current wealth, I don't invest. " Remember that the concept of utility +is about the personal value of potential consequences and is therefore different for different individuals. An individual who finds that the expected utility resulting from integrating the mentioned + +154 + +investment with his wealth are higher or about the same as the expected utility of his current wealth, will choose the favorable investment. + +Ask: What do I end up with? How much will I have ifl succeed and how much will I have ifl fail? How certain am I? What is the expected utility? + +The consequences of low frequency events + +Imagine the following scenario: + +Outcome A OutcomeB + +Probability Cost of consequence + +10% -90 + +90% -10 + +Expected value + +-9 + +-9 + +Both outcomes have the same expected value but differ hugely in their cost of consequences. We can't only look at how likely an unwanted event is to happen. We must also rate the magnitude of its +consequences. Before taking an action, ask: What are the benefits and costs? What might go wrong? How can it go wrong? How much can I lose? What is the probability and consequence of failure over time? How +can the probability and consequence of failure be reduced? + +What if the probability of success is high but the consequence of failure is terrible? + +The consequences of being wrong + +Take no chance whatsoever with food poisoning, and stay away from places where others have been recently killed, regardless + +of what the mathematical laws of probability tell you. + +- Edward Wilson (Professor Emeritus, from Consilience) + +"Pascal's Wager" is Blaise Pascal's argument for believing in God. Pascal reasoned as follows: If we believe in God, and God exists, we would gain in afterlife. If we don't believe in God, and God exists, we +will lose in afterlife. Independent of the probabilities of a God, the consequences of not believing are so awful, we should hedge our bet and believe. + +Pascal suggests that we are playing a game with 2 choices, believe and not believe, with the following consequences: + +155 + +Probability (p) Believe + +Don't believe + +God does exist + +p + +Saved (good) Damned (bad) + +God does not exist (1 - p) + +Inconvenience Normal life + +If God exists, and we believe God exists, we are saved. This is good. If we don't believe, and God is unforgiving, we are damned. If we believe but God doesn't exist, we miss out on some worldly pleasures. If +God doesn't exist and we don't believe that God exists, we live a normal life. + +Expected value of believing= p (the value of being saved) + (1-p)(the cost of inconvenience) + +Expected value of not believing = p(the cost of being damned) + (1-p)(the value ofliving a normal life) + +Pascal said: "If I lost, I would have lost little. If I won I would have gained eternal life." Our choice depends on the probabilities, but Pascal assumed that the consequences of being damned is infinite, +meaning the expected value of believing is least negative and therefore he reasoned that believing in God is best no matter how low we set the probability that God exists. + +john wants to make extra money and is offered to play Russian Roulette. + +If John wins he gets $10 million. Should he play? There are 6 equally likely possible outcomes when he pulls the trigger - empty, empty, empty, empty, empty, bullet. This makes the probability 5/6 or 83%. +This is the same as saying that John is playing a lottery with only 6 tickets where one ticket is lethal. + +Should he play this game once? The probability is 83% that he gets $10 million. The probability is only 17% that he loses. + +Let's look at the consequences: If John doesn't play and there was a bullet he is glad he didn't play. If he plays and there is a bullet, he dies. If he doesn't play and there was no bullet he loses the +pleasure which the extra money could have bought him. If he plays and there is no bullet he gains $10 million which would buy him extra pleasure. To play is to risk death in exchange for extra pleasure. There +is an 83% probability that John is right but the consequence of being wrong is fatal. Even if the probabilities favor him, the downside is unbearable. Why should John risk his life? The value of survival is +infinite, so the strategy of not playing is best no matter what probability we assign for the existence of "no bullet" or what money is being offered. But there may be exceptions. Someone that is poor, in +need of supporting a family who knows he will die of a lethal disease within 3 months might pull the trigger. He could lose 3 months of life, + +156 + +but if he wins, his family will be taken care of after his death. + +We should never risk something we have and need for something we don't need. But some people pull the trigger anyway. This is what Warren Buffett said about the Long-Term Capital Management affair: + +Here were 16 extremely bright - and I do mean [3mextremely [0mbright - people at the top of LTCM. The average IQ among their top 16 people would probably be as high or higher than at any other organization you +could find. And individually, they had decades of experience - collectively, [3mcenturies [0mof experience - in the sort of securities in which LTCM was invested. + +Moreover, they had a [3mhuge [0mamount of their [3mown [0mmoney up - and probably a very high percentage of their net worth in almost every case. So here were super-bright, extremely experienced people, operating with +their own money. And yet, in effect, on that day in September, they were broke. To me, that's absolutely fascinating. + +In fact, there's a book with a great title - [3mYou Only Have to Get Rich Once. [0mIt's a great title, but not a very good book. (Walter Guttman wrote it many years ago.) But the tide is right: You only have to get +rich [3monce. [0mWhy do very bright people risk losing something that's very important to them to gain something that's totally unimportant? The added money has no utility whatsoever - and the money that was lost +had enormous utility. And on top of that, their reputation gets tarnished and all of that sort of thing. So the gain/loss ratio in any real sense is just [3mincredible... [0mWhenever a really bright person who has +a lot of money goes broke, it's because of leverage... It's [3malmost [0mimpossible to go broke without borrowed money being in the equation. + +157 + +- SIX - + +SCENARIOS + +Systems construction and planning processes + +He that builds before he counts the cost, acts foolishly; + +And he that counts before he builds, finds he did not count wisely. + +- Benjamin Franklin + +just as john started to renovate his house, TransCorp initiated a billion-dollar project. Why do house construction projects, start-ups or product development ventures take more time, money and effort than we +expect? For example, one study found that of 3,500 projects executed, the project budget was often exceeded by 40 - 200%. Studies by Planning Professor Bent Flyvbjerg found that about 9 out of 10 +transportation infrastructure projects had cost overruns. His studies also found large deviations between forecast and actual traffic demand volumes. He gives us several examples: Boston's Central Artery +Tunnel was 275% or $11 billion over budget in constant dollars. Costs for Denver's $5 billion International Airport were dose to 200% higher than estimated and passenger traffic in the opening year was half +of that projected. Denmark's Great Belt underwater rail tunnel had cost over-runs by 110%. Other examples on projects with cost overruns and benefit shortfalls are Bangkok's Skytrain, Los Angeles' convention +center, Quebec's Olympic stadium, the Eurofighter military jet, the Channel Tunnel, the Pentagon Spy Satellite Program, and Athens' 2004 Olympics. + +A project is composed of a series of steps where all must be achieved for success. Each individual step has some probability of failure. We often underestimate the large number of things that may happen in +the future or all opportunities for failure that may cause a project to go wrong. Humans make mistakes, equipment fails, technologies don't work as planned, unrealistic expectations, biases including sunk +cost-syndrome, inexperience, wrong incentives, contractor failure, untested technology, delays, wrong deliveries, changing requirements, random events, ignoring early warning signals are reasons for delays, +cost overruns and mistakes. Often we focus too much on the specific project case and ignore what normally happens in similar situations (base rate frequency of outcomes-personal and others). Why should some +project be any different from + +158 + +the long-term record of similar ones? George Bernard Shaw said: "We learn from history that man can never learn anything from history." + +The more independent steps that are involved in achieving a scenario, the more opportunities for failure and the less likely it is that the scenario will happen. We often underestimate the number of steps, +people and decisions involved. + +Add to this that we often forget that the reliability of a system is a function of the whole system. The weakest link sets the upper limit for the whole chain. + +TransCorp wants to develop a new product. + +To predict the probability of developing the new product we need to know all the steps in the product development chain and the probability of each one. The project is composed of 6 steps and each step is +independent of the others. Each step has an 80% probability of success. Based on similar development programs performed under the same conditions, TransCorp estimates that 8 out of 10 times each step is +successful. In 2 times out of 10 something happens that prevents each step from succeeding. But since each step is independent, the probabilities must be multiplied together. The probability the company +finally succeeds in developing the product is 26% - meaning that TransCorp should expect success one time out of four. So even if each step had an 80% probability of success, when combined, the probability of +product success decreases to 26%. + +Every time we add another step to some system, the probability that the system works is reduced. + +John is thinking of investing in a biotech start-up. + +Professor and startup coach John Nesheim, who has been involved in some 300 plus startups, tells us in High Tech Startup, that only six out of one million high tech ideas turn into a public company. This base +rate frequency tells us there is a low prior probability of turning into a public company. + +Take a biotech venture as an example. Studies show that of every 10,000 to 30,000 drug candidate molecule entering discovery, only 250 make it to pre clinical evaluation; only 5 to 10 to clinical; and only +one gets approved. There are so many things that must go right before it becomes a business that generates money. Factors like technological virtue, product safety, cost-effectiveness, manufacturing, patent +issues, product stability, regulatory matters, market assessment, competitive position, financial need (and availability), etc. How can we put a probability number on all these factors? And even if we can, +these factors must all work to achieve the desired scenario. Ask: What is the prior probability of success for this type of venture before I consider this specific case? + +159 + +Warren Buffett says on biotech: + +How many of these companies are making a couple of hundred million dollars a year? It just doesn't happen. It's not that easy to make lots of money in a business in a capitalistic society. There are people +that are looking at what you're doing every day and trying to figure out a way to do it better, underprice you, bring out a better product or whatever it may be. + +The compensation we need for taking a risk is really a function of the wanted outcome in relation to all possible outcomes. Take rolling a die as an example. How likely is it that we get a six four times in a +row? If we have to invest $1 to play this game once, we need to get back $1,296 to go even. There are 1,296 outcomes and only one of them is favorable (6,6,6,6). + +The more negative things that can happen - or positive things that must happen - the better compensated we must be for taking on the risk. Ask: What can happen and what are the consequences? Anticipate +unforeseen obstacles. + +If you do venture investments, follow the advice of Warren Buffett: + +You may consciously purchase a risky investment - one that indeed has a significant possibility of causing loss or injury - if you believe that your gain, weighted for probabilities, considerably exceeds your +loss, comparably weighted, and if you can commit to a number of similar, but unrelated opportunities. Most venture capitalists employ this strategy. Should you choose to pursue this course, you should adopt +the outlook of the casino that owns a roulette wheel, which will want to see lots of action because it is favored by probabilities, but will refuse to accept a single, huge bet. + +We can demonstrate Buffett's advice mathematically. Suppose a start-up has a 40% probability of succeeding. The probability that 10 mutually independent start-ups (with the same probability of success) all +succeed is 0.01% but the probability that at least one succeeds is 99.4%. Here we assumed that the fate of each venture is independent of the fate of the other. That one start-up fails make it no more likely +that another start-up fails. + +"How can we fond this venture if we don't present a great fature?" + +Consider bias from incentives. To sell in a venture, expected returns are often overestimated. Warren Buffett says, "We expect all of our businesses to now and then have ups and downs. (Only in the sales +presentations of investment banks do earnings move forever upward.)" + +160 + +Systems failure and accidents + +On July 25th, 2000, a Concorde bound ftom Paris to New York crashed shortly after take off All I 09 people on board were killed, along with 4 on the ground. + +A stray metal strip on the runway lost by another aircraft caused the event. As a result a tire burst. Its explosion sent pieces of rubber into the fuel tank, causing a fuel leak and fire. + +We underestimate how likely it is that an event happens when it may happen one way or another. Accidents happen if they have opportunities to happen. + +Astronomy Professor Carl Sagan said in Carl Sagan: a life in the cosmos: "The Chernobyl and Challenger disasters remind us that highly visible technological systems in which enormous national prestige had +been invested can nevertheless experience catastrophic failures." + +System safety doesn't reside in one component but in the interactions of all the components. If one key component fails, the system may fail. Assume a space shuttle is composed of 2,000 independent parts or +smaller systems, each with a workingprobabilityof99.9%. All parts need to work for the shuttle to work. The probability that at least one of the parts doesn't work causing the shuttle to malfunction is 86% +(many parts means many opportunities for failure). + +The blackout began at 10:30 p.m. in the Omaha area and the domino effect caused a cascade of electricity cuts throughout U.S. + +Some systems are more prone to accidents than others because of the number of components, their connections and interactions. The more variables we add to a system, and the more they interact, the more +complicated we make it and the more opportunity the system has to fail. Improving certain parts in highly interconnected systems may do little to eliminate future problems. There is always the possibility of +multiple simultaneous failures and the more complicated the system, the harder it is to predict all possible failures. The exception to this is systems that serve as a substitute if the present system breaks +down. We must ensure that backup systems don't cause unwanted effects or that some parts share the same defects. + +Separate between independent and dependent events. The probability that an airplane navigation system works is 99% and the probability that the backup navigation system works is 90%. The probability that the +backup system fails is not influenced by whether the primary system fails or not. The probability that neither navigation system works is one tenth of a percent (0.0lx0.1). Navigation system reliability is +therefore 99.9% (at least one navigation system will work). + +But if the systems are dependent - the probability of the backup failing rises + +161 + +if the primary system fails - the overall probability of a system failure increases. We can't assume that events are independent of each other. What happens next in a chain of events may not be independent of +the previous outcome. Subsystems may share something in common. For example, aircraft engines draw fuel from a common supply and a common pump. Dependence can also be caused by the fact that parts are of the +same design, manufactured by the same company. + +Unlikely things happen if enough time passes. An event that has one chance in 20 of happening in any given year (assume that the probability stay the same over time) is nearly certain to happen over 50 years +(92.3%). If we reduce the probability to one chance in 40, the probability of the event happening at least once over 50 years is decreased to 71.8%. + +Suppose there are 40 independent ways for a nuclear accident to happen in any given year, each with a probability of 1 in 1000. The probability that an accident happens in any given year is 3.9%. The +probability that at least one nuclear accident happens during the next 10 years is 33%. + +We might reduce the probability of accidents, but not eliminate them. + +At 3:42pm, San Francisco was shaken by a major earthquake. + +Based on frequency and scientific data, scientists estimated in 2003 that there is a 62% probability (the error range could be anywhere from 38 to 87%) of at least one magnitude 6.7 or greater earthquake, +striking somewhere in the Bay region before 2032. The probability of a major earthquake happening in any given year is therefore 3.2% (assuming the probability of a major earthquake happening in any given +year stays the same). The probability that a major earthquake will happen at least once during the next 5 years is 15%. + +Regardless of the factors that are considered in predicting earthquakes, chance plays a role in whether a large earthquake happens. + +Can we predict the time, location and magnitude of a future earthquake? Berkeley Statistics Professors David Freedman and Philip Stark say in their report What is the chance of an earthquake that a larger +earthquake in the Bay Area is inevitable, and imminent in geologic time: "Probabilities are a distraction. Instead of making forecasts, the USGS [U.S. Geological Survey] could help to improve building codes +and to plan the government's response to the next large earthquake. Bay Area residents should take reasonable precautions, including bracing and bolting their homes as well a securing water heaters, +bookcases, and other heavy objects. They should keep first aid supplies, water, and food at hand. They should largely ignore the USGS probability forecast." + +162 + +"Our technology was foolproof How could this happen?" + +Many systems fail because they focus on the machines, not the people that use them. For example, a study of anesthesiologists found that human error was involved in 82% of preventable accidents. The remainder +was due to equipment failure. + +Even if the probability that some technology works is 99.99%, human fallibility makes the system less reliable than technological reliability alone. Humans are involved in designing, execution and follow-up. +Excluding ignorance and insufficient knowledge, given the complexity of human and non-human factors interacting, there is a multitude of ways in which things can go wrong. + +In 1983 Korean airlines Flight 007 was shot down for into Russian territory for violating Russian air space. All 269 people on board were killed. + +The plane had deviated close to 360 miles from its predetermined track. It was later shown that a chain of accidental events led the plane off track. It started when the plane left Anchorage, Alaska. The +captain and crew were tired when the plane took off. A series of small events, each trivial, combined to cause a catastrophe. + +"Sorry, I left a metal instrument in your abdomen. " + +Doctors sometimes make mistakes - both in diagnosing and treating patients. For example, a surgeon leaving a metal instrument in a patient's abdomen, a patient having the wrong leg amputated, a cardiac +surgeon bypassing the wrong artery, a doctor prescribing the wrong drug, a missed diagnosis of complete heart block, a missed colon cancer, a wrong diagnosis of pulmonary embolism, or a blood product being +mislabeled. + +In the Harvard Medical Practice Study (1991), a random sample of 30,000 + +patients from 51 hospitals in the state of New York was selected. Medical records were examined to detect evidence of injuries caused by medical mismanagement. The study showed that 3.7% of patients +(negligence accounting for 1%) had complications that either prolonged their hospital stay or resulted in disability. Later studies have shown that medical errors account for between 44,000 to 98,000 deaths +in the U.S. every year and that medication errors are the leading eighth cause of death. + +A study of 100 cases of diagnostic errors in internal medicine showed that system-related factors contributed in 65% of the cases and cognitive factors in 74%. Cognitive and system-related factors often +co-occurred. The single most common cause of cognitive-based errors was the tendency to stop considering other possible explanations after reaching a diagnosis. + +Studies of autopsies show that a U.S. institution with an autopsy rate of 5%, + +163 + +can expect to misdiagnose a principal underlying disease, or the primary cause of death, about 24% of the time. Even a hospital that does autopsies on everyone should expect an error rate of about 8%. + +Henry Ford said: "Don't find fault, find a remedy." Don't assign blame. Look for causes and preventive methods. Often it is better to prevent future errors by designing safety into systems than punishing +individuals for past error. Blame does little to improve safety or prevent others from making the same mistake. For example, aviation assumes that errors of judgment happen and that it is better to seek out +causes than assign blame. That is why the Federal Aviation Administration (FM) has an Aviation Safety Reporting System (ASRS) for analyzing and reporting aviation incidents. FM utilizes NASA as a third party +to receive aviation safety reports. This cooperation invites pilots to report to NASA actual or potential deficiencies involving aviation safety. That NASA is the receiver ensures confidentiality and +anonymity of the reporter and all parties involved in an incident. There has been no breach of confidentiality in more than 20 years of the ASRS under NASA management. Pilots who report an incident within ten +days have automatic immunity from punishment. + +Safety factor + +"We always consider variability and unpredictability when setting safety factors. We act as if we were building a bridge. We are very conservative. " + +Ancient Rome used incentives in the design and construction of safe bridges. The designer of the bridge had to stand under it after completion while chariots drove over the top. This put both the designer's +life and those who used the bridge at risk. This increased the probability that designers made sure the bridge held up. Engineers and architects add a safety factor to accommodate uncertainty. This factor +depends on the consequences of failure, how well the risks are understood, + +systems characteristics and degree of control. + +Assume that accidents will happen and prepare for when people and technology don't work as planned. Systems should be designed to eliminate the probability of bad events or limit their consequences if they +happen. We can borrow an idea from aviation where incidents are thoroughly investigated to learn what went wrong and how to do better next time - critical incident analysis. Ask: How do specific accidents +evolve? What major factors contribute? Are there any common patterns? We need to add a factor of safety for known and unknown risks. We have to consider break points, build in defense systems and contingency +plans. We must also simplify and standardize equipment and processes and use checklists to + +decrease the likelihood of operator errors. + +164 + +- SEVEN - + +COINCIDENCES AND MIRACLES + +Coincidences + +The most astonishingly incredible coincidence imaginable would be the complete absence of all coincidences. + +- John Allen Paulos (from Beyond Numeracy) + +We notice certain things and ignore others. We select and talk about the amazing event, not the ordinary ones. We see coincidences after they happen. We don't see them before they happen. + +We underestimate how many opportunities there are for "unlikely" events to happen. Surprises and improbable events happen if they have enough opportunities to happen. There are many ways in which events may +be linked together. + +Getting 5 tails in a row is certain to happen somewhere, sometime to someone. The chances may be small that an event happens at a particular place, time or to a particular person. But with many places, over +long periods of time or with many individuals, the seemingly improbable will happen. As Aristotle says: "It is likely that unlikely things should happen." + +Someone flips tails 20 times in a row. + +Amazing, isn't it? Seen as an isolated event it may seem unlikely. But with a large enough group to choose from, it is likely that it happens to someone. In a group of 1,048,576 people it happens to someone. +In fact, in the U.S. a country with about 280 million people, one in a million chance events happen 280 times a day. + +How likely is it that two people share the same birthday? + +There are many opportunities for coincidences. For example, in a group of 23 people, the probability is 50.7% that two people share the same birthday. It is rather likely that events like this one happen +since there are many ways that 2 people can share an unspecified birthday. Observe that the question is not how likely it is that 2 people share any particular birthday. The question is whether it is likely +that 2 people share an unspecified birthday. + +How many people have to be present at Mary's birthday dinner so there is more + +165 + +than a 50% chance that one of the other guests has the same birthday as Mary? 183, since we now work with the restriction "two people must share a particular birthday." + +Scale matters. When the numbers are large enough, improbable things happen. The more available opportunities or the longer the time, unlikely events happen. Ask: What are all possible outcomes and their +likelihood? What else could have happened? + +Making up causes for chance events + +Humans are pattern seeking, storytelling animals. We look for and find patterns in our world and in our lives, then weave narratives around those patterns to bring them to life and give them meaning. + +- Michael Shermer (Publisher of Skeptic) + +john tosses a single die six times and the result is either (A) 623514 or (B) 666111. + +Which alternative showed the correct outcome? Even if (A) looks random and + +looks like it has a pattern, in independent chance events, both A and Bare equally likely or unlikely to appear. Random events may not look random. Independent sequences often show order or streaks. For +example, during the Second World War, people saw a pattern in the German bomb hits of London, expecting some areas more dangerous than others. But they were randomly distributed over London. + +We want to find reasons for all kind of events - random or not. We search for patterns even where none exist. For example, there must be something important that is happening if a particular number comes up +again and again. But it is always possible to find patterns and meaning in an event if we actively search for them and selectively pick anything that fits the pattern and ignore everything that doesn't. But +we can't predict the pattern in advance. + +John rolls five dice and gets five sixes. + +The probability that some roll contains any five specified numbers is very small or one in 7,776 (for example, 6x6x6x6x6). When we toss five dice there are precisely 7,776 different combinations of numbers +that can appear. Every combination is equally likely and one of them is certain to happen every time we roll five dice. Even if one particular combination (five sixes) is improbable, no single combination is +impossible. Any combination that happens is simply one out of a number of equally likely outcomes. It may have been improbable that John rolled five sixes, but not impossible. + +166 + +Anything can happen if the number of possibilities is large. People have seen a human face on Mars, faces in rocks, clouds or even in a grilled cheese sandwich. But that is no mystery. Given the large numbers +of rocks, clouds, and sandwiches, sooner or later we will find one that looks like a face, even a particular face. + +Believing in miracles + +Impector Gregory: '1s there any point to which you would wish to draw my attention?" Sherlock Holmes: "To the curious incident of the dog in the night-time. " + +Inspector Gregoty: "The dog did nothing in the night-time. " + +"That was the curious incident,"remarked Sherlock Holmes. + +- Arthur Conan Doyle (from Silver Blaze) + +Mary thinks about calling her friend Jill. Suddenly the phone rings and it is Jill. + +Is something paranormal going on? No, Mary forgot about all the times Jill didn't call when Mary was thinking about her, or the times someone else called, or the times Jill called but Mary wasn't thinking of +her, or the times Jill didn't call when Mary wasn't thinking of her. When Mary thinks about Jill and the phone rings, it registers as an event and something we remember. When Jill doesn't call, it is a +non-event. Nothing happened. Nothing is registered and therefore nothing is remembered. + +We often pay little or no attention to times when nothing happens. We shouldn't look at past events and find significance in the amazing ones. We need to make comparisons among cases involving no cause or no +effect and look at all the other things that might have happened instead. + +"The psychic predicted the tornado" + +Amazing. It sounds too good to be by chance. What we didn't know was that the psychic predicts a tornado every week. As Marcus Tullius Cicero said: "For who can shoot all day without striking the target +occasionally." Often we don't notice the incorrect predictions, only the rare moments when something happens. We forget when they are wrong and only remember when they were right. And many times we want them +to be right, so we hear what we want to hear and fill in the blanks. + +"The art of prophecy is very difficult, especially with respect to the future", wrote Mark Twain. This is why it's important to remain skeptical of "future tellers." Their right guesses are highly publicized +but not all their wrong guesses. Like Harvard Professor Theodore Levitt said: "It's easy to be a prophet. You make twenty-five predictions and the ones that come true are the ones you talk about." Michel de +Montaigne adds: "Besides, nobody keeps a record of their erroneous prophecies since they are infinite and everyday." + +167 + +The future-tellers predictions are always far enough in the future that they never have to face the consequences when they're wrong. Or they make their forecasts so general they can apply to anyone or to any +outcome so they can't be proved wrong. + +"There is no evidence that ghosts don't exist. " + +Some things can't be proven false. The fact that there is no evidence against ghosts isn't the same as confirming evidence that there are ghosts. What is true depends on the amount of evidence supporting it, +not by the lack of evidence against it. + +Mary comes home after school and tells John: "My friend Alice witnessed a miracle. " The 18th Century Scottish Philosopher David Hume suggested a test to analyze claims of miraculous events: "No testimony is +sufficient to establish a miracle, unless the testimony be of such a kind, that its falsehood would be more miraculous than the fact which it endeavors to establish." + +Hume suggests the following test: If the opposite of a given statement is more + +likely, the statement is probably false. Thus, isn't it more likely that the opposite, "Alice didn't witness a miracle" is true? Not because miracles are impossible but because the alternative explanation of +illusion is more probable. How many things that are impossible must happen for a miracle to be true? + +The German poet Johann Wolfgang von Goethe said: "Mysteries are not necessarily miracles." That an event can't be explained doesn't mean it is a miracle. No theory can explain everything. As Michael Shermer +says, "My analogy is that the L.A.P.D. [Los Angeles Police Department] can solve, say, 90 percent of annual homicides. Are we to assume that the other 10 percent have supernatural or paranormal causes? No, of +course not, because we all understand that the police cannot solve all murder mysteries." + +Bertrand Russell said in A History of Western Philosophy: "Uncertainty, in the presence of vivid hopes and fears, is painful, but must be endured if we wish to live without the support of comforting fairy +tales." + +168 + +- EIGHT - + +RELIABILITY OF CASE EVIDENCE + +Prior probabilities + +At the dinner table john tells Mary: "One of our employees got caught today for stealing, but she said she never did it before and will never do it again. " + +How likely is it that she never did it before? Look at the prior probability of stealing, considering for example, the base rate or how typical or representative an event or attribute is. + +Charles Munger tells us how John should think: + +If you're going to catch 10 embezzlements a year, what are the chances that any one of them - applying what Tversky and Kahneman called base rate information - will be somebody who only did it this once? And +the people who have done it before and are going to do it again, what are they all going to say? Well in the history of the ... Company they always say, "I never did it before, and I'm never going to do it +again." And we cashier them. It would be evil not to, because terrible behavior spreads. + +Does eyewitness identification or DNA evidence mean that a person is guilty? Does a positive medical test mean that a person has a disease? + +In the eighteenth century, the English mathematician and minister Thomas Bayes laid a foundation for a method of evaluating evidence. The French mathematician Pierre Simon de Laplace brought the method to its +modern form. Bayes' Theorem makes it possible to update the prior probability of an outcome in light of new evidence. It is easier to use if we change probability formats into frequency formats. Let's use +Bayes's Theorem with a modified version of the classic cab problem, + +originally developed by the Psychologists Daniel Kahneman and Amos Tversky. + +john testifies in court: '1 witnessed the accident and the cab involved was green. " John's vision has been reliably tested and the tests establish that he can identify the color green correctly 8 out of 10 +times. John said "green" in 8 out of 10 cases when something was green and said "green" 2 times out of 10 when something was blue. This means that John misidentified the color 2 out of 10 times. + +How trustworthy is John as an eyewitness? A witness testimony always + +169 + +contains a degree of uncertainty. Also remember that the reliability of any observation not only depends on the reliability of the observer - even if John has good eyes - but also on how likely his +observation is true given prior probabilities. First we ask: What is the prior probability ofoutcome- how probable is an event prior to considering the new evidence? How probable is it that a green cab was +involved in an accident before we consider John's evidence? Assume that the relative frequency (the proportion of cabs of a certain color in a particular population at a specific point in time) of blue and +green cabs gives us information about the prior probability of involvement in the accident. What was the proportion of blue and green cabs out of all cabs at the time of the accident? Assume there were a +total of 100 cabs in town. 90 blue and 10 green. This means that the prior probability the + +cab involved was green is 10% (10 green cabs out of 100). + +What is the (posterior - after considering case evidence) probability the cab was green given that John said it was green? + +John says "green" + +Given green + +8 cabs (IO x 0.8) + +Given blue 18 (90 X 0.2) + +Total 26 + +If 10 out of 100 cabs are green and John is right 8 out of 10 times, then he identifies 8 cabs as green. IfJohn says green cab and it is not a green cab then he is likely to identify 18 of the 80 blue cabs as +green. Out of a total of 26 cabs John has identified as green, only 8 are green. This means that the likelihood that the cab was green given John's testimony that "the cab was green" is 31 % (8/26). It seems +the cab involved is more likely to have been blue. + +Before John testified the prior probability was only 10% that the cab involved was green. When he testified "green" the probability rose to 31%. + +"Based on 50 years of accidents involving cabs, given the same proportion of color, 3 out of 4 times the cab involved was green. " + +Independent of the frequency of blue and green cabs, the appropriate prior probability may have been past evidence of accidents. What we want is the correct evidence that is representative for what was likely +to happen before we considered the new evidence. + +When we get new representative evidence, we must update the prior probability. Ask: What has happened in similar cases in the past? Are there any reasons this probability should be revised? Have the +circumstances or the environment changed? The more uncertainty that surrounds a specific case, the more emphasis we must put on the prior probability. + +170 + +How strong is the evidence? + +One factor when evaluating evidence is the coincidental or random match probability. It answers the question: What is the probability that a person other than the suspect, randomly selected, will match a +certain profile? For example, when evaluating DNA evidence a random match happens when two different people share the same DNA profile. + +After five days of searching, the police found the missing woman strangled to death. john's brother, Bill, is on trial for her murder. + +There is a DNA profile match. The forensic evidence against Bill is blood and tissue samples taken from the crime scene, which match Bill's. Either Bill left the evidence or someone else did. + +What is the probability of a coincidental match? How likely is it that a match occurs between the DNA profile found at the scene of the murder and a randomly chosen person? How likely is it that Bill's +profile matches the profile of the person who did leave the evidence at the crime scene? How rare is this profile? The rarer the profile, the lower the probability that Bill's matches only by chance. The +prosecution's medical expert witness estimates (estimation of the frequency of the profile in the most appropriate comparison population) the probability that there would be such a match if Bill was innocent +and the match was just a coincidence as only 1 in 20,000. This means that out of every 20,000 individuals, only one will have the same DNA profile as the one found at the murder scene. The prosecutor argues: +"There is only a one in 20,000 chance that someone other than Bill would by chance have the same profile as the one found on the murder scene. The probability is therefore only 1 in 20,000 that someone other +than Bill left the evidence. "The figure had a dramatic impact on the media and + +the jury. Bill was found guilty and given a life sentence. + +Where did justice go wrong? The prosecutor confused two probabilities. The probability that Bill is innocent given a match is not the same as the probability of a match given Bill is innocent. The prosecutor +should have said: "The probability is one in 20,000 that some person other than Bill would leave the same blood and tissue as that found on the crime scene. " + +The jury also needs to consider prior (before the evaluation of the forensic evidence is considered) probabilities of guilt. The probability that Bill is the murderer can't only be calculated from the +forensic evidence alone. Other evidence needs to be considered. The significance of forensic evidence always depends on other evidence. What other data do the police have? What else is known about Bill? Does +he have an alibi? Was he near the crime scene? Each piece + +171 + +of evidence must be considered together, and not in isolation. There may also have been a non-criminal explanation of why Bill left the blood and tissue samples. + +Based on evidence prior to considering the forensic evidence the jury estimates there is a 10% probability that Bill is the source of the forensic evidence (90% that he is not and thus innocent). The +probability of a match given Bill is guilty is 1 (sensitivity 100% i.e. no false negatives) because if Bill is the source of the forensic evidence and the laboratory test is accurate, his DNA profile will +match. Combining this with the random match probability of one chance in 20,000 (that his DNA profile showed up at the crime scene just by chance) gives a posterior probability that Bill is the source of the +forensic evidence of 99.96% (0.1/0.100045). + +Match + +Given guilty Given innocent + +0.1 (10% X 100%) 0.000045 (90% X 1/20,000) + +Total 0.100045 + +One way of determining the prior probability is by asking: What is the population from which the murderer could have come? We need to know the appropriate comparison population to estimate this number. The +murder has taken place in a city of 500,000 men. Assume any man in the city could have committed the crime. One of them is the murderer. Of the 499,999 people innocent, we can expect about 25 coincidental DNA +matches. This means there are 26 men (25 + the murderer) who could have committed the crime. Since Bill is one of these 26, the probability that he is guilty given the forensic evidence, is only 3.8% (1/26). + +But is this really true? It is only true if all men are equally likely to have committed the crime. For example, that they all had the same access to the crime scene. + +The choice of appropriate comparison population also matters. How did the expert witness estimate the random match probability? What is the real prevalence of this profile? And does the random match +probability mean that this profile would occur only once in 20,000 individuals? No, the calculated frequency is only an estimate that may be wrong in either direction. + +DNA evidence is also easier to plant at a crime scene than for example fingerprints (DNA evidence is easier to manufacture or distort). In Scientific Conversations by Claudia Dreifus, forensic mathematician +Charles Brenner says about the O.J. Simpson case and DNA evidence: "The defense did something very clever from the DNA point of view: They said the evidence was planted. Their basic strategy was even if it +matches, it was a plant. They gave up on the + +172 + +strategy of disproving the DNA evidence. There obviously was a match in the blood. They never denied it." + +In the O.J. Simpson trial, the defense argued that fewer than one out of 1,000 wife abusers kill their wives. Therefore evidence of abuse is irrelevant and should not be admissible in a murder trial. But the +appropriate probability is not the probability that a man who abuses his wife kills her. The relevant comparison population to consider is wives who have been abused by their husbands and thereafter been +murdered by someone. The relevant question is therefore: What is the probability that a man killed his wife given that he abused her and given that she was actually killed by someone? And Nicole Brown Simpson +was killed, not just abused. + +John Allen Paulos says in Innumeracy that given reasonable facts about murder and abuse, it has been shown that if a man abuses his wife or girlfriend and she is later killed, the abuser is the killer more +than 80 percent of the time. But this doesn't mean that the probability that the husband or boyfriend is guilty of murder is 80%. It is just one piece of evidence among many that needs to be considered. + +Do errors happen in testing? + +Yes, one type of error is a false positive and another is a false negative. A false positive is akin to a false alarm. A false negative is the missing of a real effect. For example, some factors that can +influence the reliability of medical test results and cause false positives are: the clinical accuracy of the test method (compared with some "gold standard"), patient preparation, medical conditions, +medications and laboratory errors. People may also make errors when collecting and handling samples, in their interpretation of test results or in reporting test results correctly. + +john tested positive for a rare disease with a mortality rate of BO%. How scared should he be? + +What is the chance that anyone (a person chosen randomly and belonging to the same risk group as John) actually has the disease given that they tested positive? The predictive value of the test depends both +on the clinical accuracy of the test and prior probabilities or the proportion of individuals with the disease in the population we are testing at agiven time (prevalence). Clinical accuracy is composed of +sensitivity (the frequency of positive test that results in positive samples) and + +specificity (the frequency of negative test that results in negative samples). + +Assume a population of 100,000 people. + +The frequency of people with the disease in the population is 0.1 % i.e. one person in 1,000 has the disease. Before the test John had a 0.1% chance of having + +173 + +the disease and a 99.9 % chance of not having the disease. If the test was 100% accurate, 100 people should test positive and 99,900 should test negative. These are the prior probabilities. + +The test has a 97% sensitivity or true positive rate. This means that 97 out of 100 people with the disease correctly test positive. It also means that 3 people out of 100 with the disease wrongly test +negative (false negatives). + +The test has a 95% specificity or true negative rate. This means that 95 out of 100 people without the disease correctly test negative. 5% of the time the test is incorrect. 5% of the people without the +disease or 4,995 people wrongly test positive (false positives). + +Since John is told he tested positive, the information he needs is the frequency of people that test positive and have the disease (true positives) and the frequency of people that test positive but don't +have the disease (false positives). + +Test positive + +Given disease 97 (100 X 0.97) + +Given not disease 4,995 (99,900 X 0.05) + +Total 5,092 + +Out of every 1,000 people belonging to the same risk group as John, we can expect that 19 people have the deadly disease given they test positive (97/5,092). The probability that John has the deadly disease +given he tested positive is about 1.9% or very low. Out of 5,092 tests, most are false positives indicating the disease when there is no disease. + +What if a randomly tested person tests negative? There are 3 false negatives and 94,905 true negatives, meaning that there is more than a 99.9% chance that the person doesn't have the disease. + +The label "tested positive" can be scary but remember that the test is not the disease. A test could fall in the group of false positives. But which is worst? To belong to the group of false positives - +diagnosed as having the disease without having it, or false negatives - diagnosed as not having the disease but having it? The higher the prior probability or the more common a disease, the more reliable the +outcome of the test. Conversely, the lower the prior probability or the more rare the disease, the less reliable the outcome of the test. Even a highly accurate test can yield an unreliable result if it tests +for a rather uncommon disease. This assumes that the individual tested does not belong to a group of + +people at higher risk of having the disease. + +Ask: What is the frequency of people with the disease in the relevant comparison population before I consider specific case evidence? How accurate is the medical test? + +174 + +The above reasoning can be used to help evaluate the reliability of diagnostic tests or screening procedures. Some examples are screening for or diagnosis of breast cancer, prostate cancer, colorectal cancer, +HIV or drug use. + +Estimating the frequency of false positives and false negatives are also important when evaluating the reliability of polygraph tests (used in criminal investigations or for screening employees) and +identification systems. + +In polygraph tests, false positives occur when innocent persons are found deceptive. False negatives occur when guilty persons are found non-deceptive. + +In identification systems, a false positive occurs when a system accepts a match where there is none. A false negative occurs when a system fails to recognize a match where there is one. + +The probability of false positives is also a factor to consider when evaluating the value of DNA profile evidence. This means that the jury in Bill's case also needs to consider the false positive rate. The +jury needs to ask: What is the probability that the laboratory reports a match between two samples that don't match? A reported match doesn't necessarily mean a true match. Errors happen. A possible +explanation for the forensic match may be error due to contamination (accidental or deliberate), mishandling the evidence, or switching the samples. For example, in one rape case, technicians from the Houston +police crime laboratory told the jury that they found a DNA match between a rapist's DNA and a male suspect. The man was convicted in 1999 and sent to prison for 25 years. In 2003, the Houston Police +Department said that the DNA was not from the convicted man. + +When evaluating case evidence we must consider the prior probability, the + +probability of a random match, and the probability of a false positive. + +175 + +- NINE - + +MISREPRESENTATIVE EVIDENCE + +[1mConditions, environments and circumstances change [0mPeople like to look for systems that have worked over the past 20 years or so. Ifyou could make money based on what has worked + +the past 20 years, all of the richest people would be librarians. + +- Warren Buffett + +Bertrand Russell said in [3mProblems of Philosophy: [0m"The man who has fed the chicken every day throughout its life at last wrings its neck instead." Often the past is a good guide to the future - but not always. +Statistics are a record of the past, not a prediction of the future. We can't automatically assume that the future will mirror the past. Processes and circumstances change. Warren Buffett says: "Conditions +relating to technology and all aspects of human behavior can make the future a lot different than the past." + +We need to consider changes in conditions before using past evidence to predict likely future outcomes. For example, it's in the nature of businesses and economic conditions to change. Competition and demand +changes. If there are more ways for creating competition or less demand, we have to change the equation. Ask: Why was past experience the way it was? What reason is there to suppose that the future will +resemble the past? Has the environment changed? Are the conditions similar? Are the context and circumstances that caused the past still present? + +We also make mistakes if we ignore that past performance may have been achieved under far different circumstances than today. As Warren Buffett says, "The same mistake that a baseball manager would were he to +judge the future prospects of a 42-year-old center fielder on the basis of his lifetime batting average." Management performance may also be conditioned on environment. What makes an individual successful in +one environment does not guarantee success in + +another. Ask: What is the company's or manager's ability to handle adversity? + +"We can sell more if we market the illness rather than the drug,"said the manager of TransCorp's pharmaceutical division. + +Is the frequency of a disease really increasing? We need to consider other factors + +176 + +before we conclude that the frequency of an event has changed. For example, a disease may be more correctly diagnosed than it was in the past. Often we only see what we have names for - a disease that was +formerly classified as "disease X" or "cause unknown" may now be re-classified or get a name. There may also be technological improvements in the collection and reporting of data. There may also be business +incentives at work. For example, widening a market by creating a new condition, redefining adisease or exaggerating a minor one, thereby having more people labeled as having a disease. + +If conditions change, we must update our assumptions to reflect the present + +environment. Before we use the change as evidence for what is likely to happen, ask: What has changed? Are there more ways for some undesirable event to happen? Is the change permanent or temporary? + +The single case or unrepresentative samples + +Four out of five doctors recommend the drug. + +This statement doesn't tell us anything if we don't know how many doctors were observed. Maybe it was just 1O; an observation that can't be extrapolated to include all doctors. A small sample size has no +predictive value. The smaller the sample is, the more statistical fluctuations and the more likely it is that we find chance events. We need a representative comparison group, large enough sample size, and +long enough periods of time. + +Small samples can cause us to believe a risk is lower or higher than reality. Why? A small sample increases the chance that we won't find a particular relationship where it exists or find one where it doesn't +exist. + +Charles Munger gives an example of the importance of getting representative data - even if it's approximate: + +The water system of California was designed looking at a fairly short period of weather history. If they'd been willing to take less perfect records and look an extra hundred years back, they'd have seen that +they weren't designing it right to handle drought conditions which were entirely likely. + +You see that again and again - that people have some information they can count well and they have other information much harder to count. So they make the decision based only on what they can count well. And +they ignore much more important information because its quality in terms of numeracy is less - even though it's very important in terms of reaching the right cognitive result. All I can tell you is that +around Wesco and Berkshire, we try not to be like that. We have Lord Keynes' attitude, which Warren quotes all the time: "We'd rather be roughly right than precisely wrong." In other words, if something + +177 + +is terribly important, we'll guess at it rather than just make our judgment based on what happens to be easily countable. + +Chance and performance + +No victor believes in chance. + +- Friedrich Wilhelm Nietzsche + +Past performance is no guarantee of future results. Consider evidence that describes what happens in most similar situations or to most people. + +Sometimes a track record is not a good indicator of what is likely to happen in the future. It may show up by luck. Imagine a room filled with 1,000 monkeys. Each is trying to predict the direction (up or +down) of interest rates. At the end of 10 predictions, one monkey has a perfect record of predicting the direction of interest rates. He is considered agenius and the greatest economist in history. Even if it +was just by chance. As soon as we have a large population of forecasters that predict events where chance plays a role, someone will be right, get press coverage and be presented as a hero. He will hold +lectures and give sensible explanations. + +Sometimes we only see the good performers. Partly because winners have a tendency to show up (one monkey). Losers don't (999 monkeys). Often we aren't interested in the losers anyway. But we shouldn't be +amazed to see winners if there is a large population to choose from. 10,000 monkeys and we find 10 geniuses. When we measure performance we must consider both the number of successes (one monkey), the number +of failures (999 monkeys), and the size of the relevant comparison population they came from (1,000 monkeys). The more people (or monkeys), involved in something where chance plays a role, the more likely it +is that some people have great performances just by chance. An exception is in a group of high performers where we can observe some common + +characteristics that may be a causal factor and not luck. + +The same mistakes may happen when people base their conclusions on mere effects and ignore the influence of chance. Think about 100 monkeys. They each roll a die once. Select those 16 monkeys (1/6x100) who +rolled a six. As a cure for their "roll-a-six" tendency we give them a new drug. After taking the drug they roll the die again. Now only 2 or 3 monkeys (1/6x16) rolled a six. The rest were "cured." Our false +conclusion: "The drug obviously worked." + +A con artist sets up a trap. He calls John with a tip. "Watch this stock. It will go up." After 3 correct predictions, John sends him his money. The con artist disappears. + +What John didn't know was that the con artist made the same call to 80 people. + +178 + +He told half of them the stock would go up, and the other half the stock would go down. And one of his predictions is sure to be right. 40 people were impressed. At the second call 20 people were impressed +and at his third and last call he was considered a genius by 10 people who all sent him their money. + +Ignoring failures + +Evidence must be drawn from the frequency of both success and failure over time. Often we only consider the successful and supporting outcomes. The epidemiological literature refers to this as survival bias. +Only the characteristics of the survivors of a disease or outcome under study are included in the study. Those who have died before the end of the study are excluded. If these are patients with more severe +risk factors, the study reduces an apparent association between risk factors and outcomes. Survival bias is also common in all studies made after the outcomes have occurred (including back testing). They only +focus on surviving cases or patients. The people who have died are not in the sampling pool. People may also select or omit certain information by only publishing positive outcomes and omitting negative ones. + +If we only study successes or survivors, a performance record may look better than it really is. Charles Munger says that we give too little attention to failures: + +It is assumed by many business school graduates, and by almost all consultants, that a corporation can easily improve its outcome by purchasing unrelated or tenuously related businesses. According to this +widely shared view, if only the obvious steps had been taken, if the right "mission statement" had been adopted and the right "experts" hired, then each railroad, instead of remaining bound in chains by new +forms of competition and obsolete and hostile laws and union rules, would have become another Federal Express, another United Parcel Service, or even another brilliant performer in the mode of Emerson +Electric. + +Our experience, both actual and vicarious, makes us less optimistic about easy solutions through business acquisition. We think undue optimism arises because successful records draw too much attention. Many +people then reason as I would ifl forecasted good prospects in big-time tennis after observation limited to Ivan Lendl and Steffi Graf, or good prospects in the California lottery after limiting observations +to winners. The converse is also true, only more so. Far too little attention is given to the terrible effects on shareholders (or other owners) of the worst examples of corporate acquisitions such as +CBS-DuMont, Xerox-Scientific Data Systems, General Electric-Utah International, Exxon-Reliance Electric... and Avon Products. + +In 1999, people said: ''internet businesses are doing great. " + +Often we see only the businesses that do well and ignore the failures. Especially + +179 + +in bull markets where successes get wide publicity. Ask: What is the relevant comparison population from which we measure 5-year performance (assume 100 Internet businesses)? How many are doing well (assume +5). How many are not performing well (assume 80). How many have gone out of business (assume 15). From this we can draw the conclusion that the above statement is false. + +TransCorps technical department developed a new defense system and claims a success rate of80%. WhenJohn observed IO tests, he witnessed 8 failures and only 2 successes. In 1992, Theodore Postal, a professor +of science and national security at MIT, measured the effectiveness (not in terms of its psychological and political impact) of the Patriot anti-missile system in the Gulf War. Based on studying videotapes of +26 Patriot/Scud engagements involving 25 misses and 1 hit, he told the Committee on Government Operations that, "the video evidence makes an overwhelming circumstantial case that Patriot did not come dose to +achieving a 80 percent intercept rate in Saudi Arabia." The Pentagon reported firing 47 Patriot missiles at Scuds, at first claiming an 80% success rate. A congressional report later concluded that Patriots +succeeded in downing only 4 Scuds. + +If we assume that John's observations represent a valid random sample of tests, + +how likely is it that he would observe exactly 2 "hits" and 8 "misses" if the technical department's claim was true? + +This is an example of a binomial experiment. It describes experiments with repeated, identical trials where each trial can only have two possible outcomes (e.g. success or failure). Assuming independent +engagements, the probability is only 0.007%. If the departments claim was true, then John witnessed an event of a very low probability. It is more likely that their claim was false. + +Variability + +You can, for example, never foretell what any man will do, but you can say with precision what an average number will be up to. Individuals vary, but percentages remain constant. So says the statistician. + +- Arthur Conan Doyle (from The Sign of Four) + +When evaluating likely outcomes, look at the whole distribution of possible outcomes + +- average outcome, variability, and the probability of an extreme outcome and its consequences. What we mean by variability is how much the individual outcomes are spread out from the average outcome. The +more spread out, the more variability. Ask: What has happened in the past? How much do the outcomes fluctuate around the average? What factors contribute to past variability? Have they changed? + +180 + +The normal distribution curve shows a frequency distribution of outcomes and may sometimes help us find the most frequent outcomes and the variations. There are many ways a set of outcomes can be spread out +or distributed. But some outcomes are more frequent than others. Many characteristics resulting from independent random factors have a bell-shaped frequency distribution. This means that the most frequent +outcomes will be in the middle of the distribution, and the other outcomes will fall on either side of the middle. The + +further away any outcome is from the middle, the less frequent it is. + +Examples of normally distributed outcomes are heights or weights of adults (which depend on factors such as genes, diet, or environment), temperatures, car accidents, mortality rates, or the length of life of +a light bulb. + +What is the average height of female adults? + +If we randomly select one thousand adult females and measure their height, we end up with a distribution of outcomes that look like a bell-shaped curve. Their heights will center around their average height, +and the breadth of the curve indicates how variable around this average the heights are. Adding one extremely tall woman to a large sample doesn't really change the average height. + +The same reasoning can be applied to an auto insurance company. The more of the same game the insurance company plays, the better the average becomes as a guide. Adding an extremely expensive car accident +doesn't really change this. The average is representative and has predictive power. + +But we can't use the normal distribution curve for those classes of insurance that involve mammoth and unusual risks. For an insurance company specializing in insuring unique events, the possible variability +in outcomes is key. + +TransCorp's new computer software grabbed 90% of the market. + +In many cases, the normal distribution curve may not give us a true picture of reality. One single favorable or unfavorable extreme event can have a large impact and dramatically change the averages. We saw +examples of this uneven type of distribution earlier with size and frequency. The less number of times or the shorter the time or the more impact a single event may have on the average, the more important it +is to consider the variability, and the more unpredictable some factor becomes. For example, suppose the average sales of books are + +$200,000. But if our sample contains one extreme best-seller (the Harry Potter + +books), the average will not help us predict what a new book on average may sell for. Other examples are movie sales (the movie Titanic), price changes in financial markets (a sudden large depreciation of a +currency, damages from + +181 + +hurricanes (Katrina), or impact from innovations (TransCorp's new software). For example, there is no typical software and past averages don't mean anything. We see what has happened in the measured past. We +don't know what the biggest hurricane will be or its likelihood of occurring. When we look back, we + +only see what the biggest hurricane was in the documented past. + +We can't use past statistics to predict these rare and high-impact events. We don't know their timing, frequency, or degree of impact. We can't exactly figure out their properties or develop a formula. We +only know that they happen and that they can have a huge impact. In some cases, we may have some evidence telling us if the probabilities are changing. Also, many events are not independent but are instead +interconnected. Financial markets are one example; markets have memories, assets may be correlated and one bad event may cause another. The danger of using the normal distribution curve in cases where one +huge event can dramatically change reality is well described at length by the Epistemologist of Randomness Nassim Nicholas Taleb in his book The Black Swan. + +10 people have a total wealth of$10 million i.e. the average wealth per person is $1 million. + +What if one person has $10 million and nine nothing? How can the average + +income soar? Suppose ten middle-class people are riding on a bus. One gets off the bus and a billionaire gets on. + +John has an option to play one of two games. Each game has three equally likely outcomes. The game may be one of chance, insurance, investing, etc. + +Outcomes Average outcome + +Probability + +Expected value + +Gamel + +30 40 50 + +40 + +1/3 1/3 1/3 + +40 + +Game2 + +0 20 100 + +40 + +1/3 1/3 1/3 + +40 + +If he plays each game over and over, the expected value is 40 for both, so it shouldn't matter what game he chooses to play. But what about ifJohn only plays this game once? He should play game 1 since it has +less variability. + +john has been offered to invest in a private venture capital fond. The venture manager's track record is an average rate of return of 25% over the last five years. + +This doesn't say much if we don't look at how the underlying performance was produced. By looking closely at how this return was produced John found that the venture manager had done 10 deals. One deal had +been a spectacular success + +182 + +and the rest failures. Had this one deal been due to luck? + +Remember that some people leave out data when reporting their performance. + +Mary reads in the paper that the average price of a house is $1,000,000. + +But this may cause her to get a false picture of reality. Assume there are 100 houses and 90 of them are priced at $500,000 and 10 "castles" at $5.5 million. We have to watch out for the variations. + +A business executive tells us that his company had average earnings of $50 million over the last 3 years. But when we look closer we find great variability and a downward trend in the performance record: +1998: $100 million, 1999: $50 million, 2000: $0. + +The median is the middle of a distribution where half the outcomes are above the median and half below. If 9 people have $1 million each and one has $1 billion, the average wealth is about $101 million, but +the median amount is $1 million. + +In 1982, Stephen jay Gould was diagnosed with a rare and deadly form of cancer with a median mortality of 8 months after discovery. He beat the cancer for 20 years. Does an 8 month median mortality mean that +a person will be dead in 8 months? Gould learned that an 8 month median mortality means half the people die before 8 months and half will live longer. But he found that there was a wider spread of outcomes +after 8 months than before. This makes sense since there is a lower limit to the spread of outcomes during an 8 month period than after 8 months. No person will die before the start of the 8 month period but +those who survive can live considerably longer than 8 months. We can't treat the average or the median as the most likely outcome for any single individual. Look at the variation between all outcomes. This +means that a treatment ought to be determined based on whether an individual is likely to have an outcome better or worse than the median. + +Effects of regression + +"Regression to the mean" is a notion worked out by Sir Francis Galton (Charles Darwin's first cousin). It says that, in any series of events where chance is involved, very good or bad performances, high or +low scores, extreme events, etc. tend on the average, to be followed by more average performance or less extreme events. If we do extremely well, we're likely to do worse the next time, while if we do poorly, +we're likely to do better the next time. But regression to the mean is not a natural law. Merely a statistical tendency. And it may take a long time before it happens. + +183 + +Dissatisfied with the new employees' performance, John put them into a skill enhancing program. He measures the employees' skills at the end of the program. + +Their scores are now higher than they were on the first test. John's conclusion: "The skill-enhancing program caused the improvement in skill." This isn't necessarily true. Their higher scores could be the +result of regression to the mean. Since these individuals were measured as being on the low end of the scale of skill, they would have shown an improvement even if they hadn't taken the skill-enhancing +program. And there could be many reasons for their earlier performance - stress, fatigue, sickness, distraction, etc. Their true ability perhaps hasn't changed. + +Our performance always varies around some average true performance. Extreme performance tends to get less extreme the next time. Why? Testing measurements can never be exact. All measurements are made up of +one true part and one random error part. When the measurements are extreme, they are likely to be partly caused by chance. Chance is likely to contribute less on the second time we measure performance. + +If we switch from one way of doing something to another merely because we + +are unsuccessful, it's very likely that we do better the next time even if the new way of doing something is equal or worse. + +Part Two and Three dealt with reasons for misjudgments and ideas for reducing them. Before we enter Part Four let's conclude with how we can learn from past mistakes. + +Post Mortem + +Spanish-American philosopher George Santayana once said: "Those who cannot remember the past are condemned to repeat it." How can we understand what is happening to us without any reference to the past? We +conveniently forget to record our mistakes. But they should be highlighted. We should confess our errors and learn from them. We should look into their causes and take steps to prevent them from happening +again. Ask: + +What was my original reason for doing something? What did I know and what were my assumptions? What were my alternatives at the time? + +How did reality work out relative to my original guess? What worked and what didn't? + +Given the information that was available, should I have been able to predict what was going to happen? + +What worked well? What should I do differently? What did I fail to do? What did I miss? What must I learn? What must I stop doing? + +184 + +Why don't we do post mortems? Charles Munger says: + +You tend to forget your own mistakes when reputation is threatened by remembering. For that very reason, one very wise company - Johnson & Johnson - has a system whereby two years or so after they've made +some big acquisition they have a post-mortem. And they bring back the original projections and the original reasons for doing the deal. They identify the people who made the arguments and what have you. Then +they compare them with how the deal worked out. + +Warren Buffett says that, "Triumphs are trumpeted, but dumb decisions either get no follow-up or are rationalized." He continues: + +Managers tend to be reluctant to look at the results of the capital projects or the acquisitions that they proposed with great detail only a year or two earlier to a board. And they don't want to actually +stick the figures up there as to how the reality worked out relative to the projections. That's human nature. + +But I think you're a better doctor if you drop by the pathology department occasionally. And I think you're a better manager or investor if you look at each decision that you've made of importance and see +which ones worked out and which ones didn't - and figure your batting average. Then, if your batting average gets too bad, you better hand the decision-making over to someone else. + +We could also use pre-mortems to help us anticipate problems and key vulnerabilities. For example, before making an important decision, imagine a failure where things really have gone wrong and ask: What +could have caused this? + +What guidelines and tools are there to better thinking? Charles Munger gives us some introductory remarks for Part Four: + +Berkshire is basically a very old-fashioned kind of a place and we try to exert discipline to stay that way. I don't mean old-fashioned stupid. I mean the eternal verities: basic mathematics, basic horse +sense, basic fear, basic diagnosis of human nature making possible predictions regarding human behavior. If you just do that with a certain amount of discipline, I think it's likely to work out quite well. + +185 + +- PART FOUR - + +[1mGUIDELINES TO BETTER THINKING [0m + +The brain can be developed just the same way as the muscles can be developed, if one will only take the pains to train the mind to think. + +- Thomas Alva Edison (American inventor, 1847-1931) + +187 + +- ONE - + +Sun Tzu said in [3mThe Art of War: [0m"The general who wins a battle makes many calculations in his temple before the battle is fought." + +The purpose of this part is to explore tools that provide a foundation for rational thinking. Ideas that help us when achieving goals, explaining "why," preventing and reducing mistakes, solving problems, and +evaluating statements. + +The following 12 tools will be discussed. + +Models of reality. + +Meaning. + +Simplification. + +Rules and filters. + +Goals. + +Alternatives. + +Consequences. + +Quantification. + +Evidence. + +Backward thinking. + +Risk. + +Attitudes. + +MODELS OF REALITY + +Educated men are as superior to uneducated men as the living are to the dead. + +-Aristotle + +Learn, understand and use the big ideas and general principles that explain a lot about how the world works. When Charles Munger was asked what would be the best question he should ask himself, he said: + +Ifyou ask not about investment matters, but about your personal lives, I think the best question is, "Is there anything I can do to make my whole life and my whole mental process work better?" + +189 + +And I would say that developing the habit of mastering the multiple models which underlie reality is the best thing you can do.. .It's just so much fun - and it works so well. + +A model is an idea that helps us better understand how the world works. Models illustrate consequences and answer questions like "why" and "how". Take the model of social proof as an example. What happens? +When people are uncertain they often automatically do what others do without thinking about the correct thing to do. This idea helps explain "why" and predict "how" people are likely to behave in certain +situations. + +Models help us avoid problems. Assume that we are told that the earth consists of infinite resources. By knowing the idea about limits, we know the statement is false. Someone gives us an investment proposal +about a project that contradicts the laws of physics. How much misery can be avoided by staying away from whatever doesn't make scientific sense? + +What characterizes a useful model? + +If a model agrees with reality, it is most likely true. One idea from biology that agrees with reality is that "people on average act out of self-interest." But not the idea that "people's personalities can +be evaluated by using the Rorschach ink-blot test." It can't predict people's personalities. Ask: What is the underlying big idea? Do I understand its application in practical life? Does it help me understand +the world? How does it work? Why does it work? Under what conditions does it work? How reliable is it? What are its limitations? How does it relate to other models? + +Charles Munger gives an example of a useful idea from chemistry - autocatalysis: + +If you get a certain kind of process going in chemistry, it speeds up on its own. So you get this marvelous boost in what you're trying to do that runs on and on. Now, the laws of physics are such that it +doesn't run on [3mforever. [0mBut it runs on for a goodly while. So you get a huge boost. You accomplish A- and, all of a sudden, you're getting A+ B + C for awhile. + +He continues telling us how this idea can be applied: + +Disney is an amazing example of autocatalysis ... They had all those movies in the can. They owned the copyright. And just as Coke could prosper when refrigeration came, when the videocassette was invented, +Disney didn't have to invent anything or do anything except take the thing out of the can and stick it on the cassette. + +190 + +Which models are most reliable? Charles Munger answers: + +The models that come from hard science and engineering are the most reliable models on this Earth. And engineering quality control - at least the guts of it that matters to you and me and people who are not +professional engineers - is very much based on the elementary mathematics of Fermat and Pascal: It costs so much and you get so much less likelihood of it breaking if you spend this much ... + +And, of course, the engineering idea of a backup system is a very powerful idea. The engineering idea ofbreakpoints- that's avery powerful model, too. The notion of a critical mass - that comes out of physics +- is a very powerful model. + +A valuable model produces meaningful explanations and predictions oflikely future consequences where the cost of being wrong is high. + +A model should be easy to use. If it is complicated, we don't use it. + +It is useful on a nearly daily basis. If it is not used, we forget it. And what use is knowledge if we don't use it? + +Considering many ideas help us achieve a holistic view + +Those who love wisdom must be inquirers into many things indeed. + +Heraclitus + +What can help us see the big picture? How can we consider many aspects of an issue? Use knowledge and insights from many disciplines. Most problems need to be studied from a variety of perspectives. Charles +Munger says, "In most messy human problems, you have to be able to use all the big ideas and not just a few of them." + +The world is multidisciplinary. Physics doesn't explain everything; neither does biology or economics. For example, in a business it is useful to know how scale changes behavior, how systems may break, how +supply influences prices, and how incentives cause behavior. + +Since no single discipline has all the answers, we need to understand and use the big ideas from all the important disciplines - mathematics, physics, chemistry, engineering, biology, psychology, and rank and +use them in order of their reliability. Charles Munger illustrates the importance of this: + +Suppose you want to be good at declarer play in contract bridge. Well, you know the contract - you know what you have to achieve. And you can count up the sure winners you have by laying down your high cards +and your invincible trumps. + +191 + +But if you're a trick or two short, how are you going to get the other needed tricks? Well, there are only six or so different, standard methods: You've got long-suit establishment. You've got finesses. +You've got throw-in plays. You've got cross-ruffs. You've got squeezes. And you've got various ways of misleading the defense into making errors. So it's a very limited number of models. But if you only know +one or two of those models, then you're going to be a horse's patoot in declarer play... + +If you don't have the full repertoire, I guarantee you that you'll overutilize the limited + +repertoire you have - including use of models that are inappropriate just because they're available to you in the limited stock you have in mind. + +Suppose we have a problem and ask: What can explain this? How can we achieve this? How can we then use different ideas? Charles Munger tells us how to do it: + +Have a full kit of tools... go through them in your mind checklist-sryle... you can never make any explanation that can be made in a more fundamental way in any other way than the most fundamental way. And +you always take with full attribution to the most fundamental ideas that you are required to use. When you're using physics, you say you're using physics. When you're using biology, you say you're using +biology. + +We also need to understand how different ideas interact and combine. Charles Munger says: + +You get lollapalooza effects when two, three or four forces are all operating in the same direction. And, frequently, you don't get simple addition. It's often like a critical mass in physics where you get a +nuclear explosion if you get to a certain point of mass - and you don't get anything much worth seeing if you don't reach the mass. + +Sometimes the forces just add like ordinary quantities and sometimes they combine on a break-point or critical-mass basis... More commonly, the forces coming out of... models are conflicting to some extent. +And you get huge, miserable trade-offs ... So you [must] have the models and you [must] see the relatedness and the effects from the relatedness. + +The British mathematician and philosopher Alfred North Whitehead said: "The problem of education is to make the pupil see the wood by means of the trees." We need to consider many aspects of an issue and +synthesize and integrate them. We need to understand how it all fits together to form a coherent whole. The term synthesis comes from classical Greek and means literally "to put together." Below are some +examples of how this can be used in problem-solving. + +192 + +We can combine ideas within a discipline. We saw in Part Two how psychological tendencies can combine and give Lollapalooza effects. + +We can try to find connections between ideas or derive new ideas from these connections. The modern evolutionary synthesis was a unification of several ideas within biology. + +We can combine ideas from different disciplines. The ideas of scaling from mathematics, systems and constraints from physics, and competitive advantage from microeconomics often explain how business value is +created or destroyed. + +We can try to see relationships between phenomena, and try to find one principle that can explain them all. The British physicist James Clark Maxwell combined in one model the laws of electricity and +magnetism with the laws of behavior of light. This single model explained optical, electrical and magnetic phenomena. + +We can find similarities or functional equivalents within or between disciplines. The functional equivalent of viscosity from chemistry is stickiness in economics. + +How can we learn an idea so it sticks in our memory? + +Samuel Johnson said: "He is a benefactor of mankind who contracts the great rules of life into short sentences, that may be easily impressed on the memory, and so recur habitually to the mind." + +Richard Feynman answered the following question in one of his physics lectures: + +If, in some cataclysm, all of scientific knowledge were to be destroyed, and only one sentence passed on to the next generations of creatures, what statement would contain the most information in the fewest +words? I believe it is the atomic hypothesis (or the atomic fact, or whatever you wish to call it) that all things are made ofatoms - little particles that move around in perpetual motion, attracting each +other when they area little distance apart, but repelling upon being squeezed into one another. In that one sentence, you will see, there is an enormous amount of information about the world, if just a little +imagination and thinking are applied. + +We can use the Feynman "one sentence explanation" when dealing with big ideas. "What sentence contains the most information in the fewest words?" An example of a one-sentence idea from psychology is: "We get +what we reward for." A sentence from physics is: "Energy is neither created nor destroyed - only changed from one form into another." + +Another way to understand a model is to give it a "hook." Associate the model with a dramatic real-life story, analogy, individual, or picture. For example to + +193 + +remember social proof, we can think about the Genovese homicide in New York City (see Part Two). + +A Chinese proverb says, "I forget what I hear; I remember what I see; I know what I do." Since the best way to learn something is by doing it, we must apply models routinely to different situations. Like any +skill, this takes both practice and discipline. + +Search for explanations + +What happens and why does it happen? + +One way of forcing us to learn models to better deal with reality is to open our eyes and look at the things we see around us and ask "why" things are happening (or why things are not happening). Take some +simple examples as "why do apples fall downward?" or "why do we fall down when we slip?" or "why don't we fall off the earth?" The English mathematician and physicist Sir Isaac Newton's law of gravitation can +explain this. + +Newton's 1st law tells us that an object in motion tends to continue in motion at a steady speed in a straight line, and an object at rest tends to stay at rest, unless the object is acted upon by an outside +force. + +This means that there are only 3 ways to change an object: an object at rest can start to move, an object in motion at a steady speed can go up or down in speed, and an object in motion in a straight line can +change direction. And what is needed to change an object's motion? A force. + +All change in motion happens in response to the action of force(s). By forces, we mean a push or a pull that acts on an object. When we open a door or throw a baseball, we are using forces (muscular effort). +Almost everything we do involves forces. + +Newton's 2nd law tells us that force is the product of mass and acceleration. Acceleration is any change in speed and/or direction. It depends on the mass (measures an object power to resist change in its +state of motion) of an object and the magnitude and direction of the force acting on it. The more force we use at a given mass, the greater the acceleration. But the more mass, the more an object resists +acceleration. For example, the more force we use to throw a baseball, the greater the acceleration of the ball. If we increase mass, we have to add more force to produce the same rate of acceleration. + +Newton's 3rd law is that forces work in pairs. One object exerts a force on a second object, but the second object also exerts a force equal and opposite in direction to the force acting on it - the first +object. As Newton said in Philosophiae Natura/is Principia Mathematica: "If you press a stone with your + +194 + +finger, the finger is also pressed by the stone." If we throw a baseball, the ball also "throws" us or pushes back on our hand with the same force. + +Now we come to the force of gravity. Influenced by Johannes Kepler's work on planetary motion and Galileo Galilei's work on freely falling objects, Newton found out that there was a force that attracts two +objects to each other. Two factors influence the degree of attraction. Mass and distance. The greater the mass of two objects or the closer the distance between them, the greater the attraction between them. +This also means that the greater the distance between the objects, the weaker the force of gravity. If we for example double the distance, the force is as fourth as strong. + +Mathematically we can state the force of attraction or gravitation as equal to the mass of one object multiplied with the mass of the other object divided by the square of the distance between the objects. +All this is multiplied with a constant (a number that doesn't change in value)-g (9.8 meters per second each second or 9.8m/s2 ). We can call g, the acceleration of gravity near the surface of the Earth. + +It is the force ofgravity that makes an apple fall toward the Earth. + +The Earth attracts the apple with a force that is proportional to its mass and inversely proportional to the square of the distance between them. But Newton's third law says that the apple also exerts an +equal and opposite force on the Earth. The force of attraction on the apple by the Earth is the same as the force of attraction on the Earth by the apple. So even if it looks to us like the apple falls to the +Earth, both the Earth and apple fall toward each other. The force is the same but as we see from Newton's second law, not the acceleration. Their masses differ. The Earth's mass is so large compared to the +apple that we see the apple "falling." Apples fall, starting at rest, to the Earth since they have less mass than the Earth, meaning they accelerate (change speed) more toward the Earth than the Earth does +toward the apple. The Earth's great mass also explains why we fall toward the Earth when we slip. + +The same force draws the Moon to the Earth. But what keeps the Moon in orbit around the Earth instead of crashing into the Earth? + +Newton knew that there must be some force pulling the Moon toward the Earth. Otherwise according to the 1st law the Moon would continue in motion in a straight line at a steady speed instead of its more +elliptical motion. Some force must continuously pull the Moon out of its straight-line motion and change its direction. And since the Moon's orbit is circular, this force must originate from the center of the +Earth. Why? Newton knew that a centripetal force (any force + +195 + +directed toward a fixed center) controls objects going in a circle around a fixed point. + +That force is gravity. It changes the Moons acceleration by continually changing its direction toward the center of the Earth causing the Moon to curve into circular motion. As the Moon moves horizontally in +a direction tangent (the straight line that touches a curve) to the Earth, at each point along its path, gravity pulls it inward toward the center of the Earth and the result is a Moon in circular orbit. + +The Moon's speed is great enough to ensure that its falling distance matches the Earth's curvature. The Moon remains at the same distance above Earth since the Earth curves at the same rate as the Moon +"falls." By the time the Moon has fallen a certain distance toward Earth, it has moved sideways about the same distance. If its speed were much lower, the pull of gravity would gradually force the Moon + +closer to the Earth until they crash into each other. If its speed where much higher, + +the Moon would escape the force of gravity and move away from us. + +The Moon doesn't accelerate as much as the apple, because of its distance to Earth (the force of gravity is weaker). The Moon in its orbit is about sixty times as far away from the Earth's center as the apple +is. + +Newton's law of gravitation isn't enough to describe the motion of objects whose speed is near the speed oflight. Why? According to Albert Einstein's theory of relativity, the mass of an object is not a +constant. It increases as its speed approaches the speed oflight. Newton's theories and the theory of relativity also differ when gravitational fields are much larger than those found on Earth. Under most +conditions, though, Newton's laws and his theory of gravitation are adequate. + +The relative influence of gravity varies with size and scale. + +Why does falling.from a high tree not harm an insect? + +In Two New Sciences, Galileo Galilei wrote: "Who does not know that a horse falling from a height of three or four cubits will break his bones, while a dog falling from the same height or a cat from a height +of eight or ten cubits will suffer no injury?" + +Imagine if a mouse, a horse and a human were to be thrown out of an airplane from 1,000 yards. What happens? The biologist J.B.S. Haldane said in On Being the Right Size (reprinted in The World of +Mathematics): "You can drop a mouse + +down a thousand-yard mine shaft; and, on arriving at the bottom, it gets a slight shock and walks away, provided that the ground is fairly soft. A rat is killed, a man is broken, a horse splashes." + +196 + +Physical forces act on animals differently. Gravity has a more powerful effect on bigger things, than on smaller things. Gravity is a major influence on us, but is of minor significance to smaller animals. +Since human surface area is so small, gravitational forces act upon our weight. But gravity is negligible to very small animals with high surface area to volume ratios. The dominant force is then surface +force. Haldane says: "Divide an animal's length, breadth, and height each by ten; its weight is reduced to a thousandth, but its surface only to a hundredth. So the resistance to falling in the case of the +small animal is relatively ten times greater than the driving force [of gravity]." + +"Weight affects speed when air resistance is present. + +On smaller scales, gravity becomes less and less important compared with air resistance. Throw a mouse off the plane and it floats down as frictional forces acting on its surface overcome the influence of +gravity. + +A falling object falls faster and faster, until the force of air drag acting in the opposite direction (arising from air resistance) equals its weight. Air drag depends on the surface area (the amount of air +the falling object must plow through as it falls) and the speed of the falling object. Since a mouse has so much surface area compared to its small weight, it doesn't have to fall very fast before the upward +acting air drag builds up to its downward-acting weight. The net force on the mouse is then zero and the mouse stops accelerating. + +The force of air resistance against the falling horse is much greater than the force against the mouse. This happens because the horse plows through more air than the mouse does. The heavier horse falls +faster through the air, increasing air resistance even more. The horse falls faster than the human before the air drag equals its weight and will therefore reach the ground first. + +The horse has a greater surface area than the mouse, but the mouse has a greater surface area for its volume than the horse has. A mouse obeys the same law of gravitation as a human, and also the same law of +air-resistance. But gravitation is key for humans, while air-resistance is all-important for the mouse. On the other hand, due to surface tension, the mouse will have problems when climbing from a pool of +water. Haldane tells us a wet mouse has to carry its own weight of water. Imagine how hard it would be to get out of the bathtub if we + +carried on our body a weight of water equal to our weight. + +These examples show how we can better deal with reality by observing and ask "why" things happen. So look around, ask questions and remember the words of inventor and engineer Charles Proteus Steinmetz: +"There are no foolish questions and no man becomes a fool until he has stopped asking questions." + +197 + +Assume that the big ideas are true until learning otherwise. All knowledge is subject to change as new evidence arrives. This mean we have to continuously learn and re-learn. + +Keeping knowledge alive and adding knowledge over time comes with an extra benefit. "Just as iron rusts from disuse, and stagnant water putrefies, or when cold turns to ice, so our intellect wastes unless it +is kept in use," wrote Leonardo da Vinci. Research by Integrative Biology Professor Marian Cleeves Diamond at the University of California, Berkeley, reveals that a stimulating environment, curiosity and +education are nourishment to the brain and therefore healthy. The more stimulation we give our brains, the better off we are. In Psychology Today (1984) she says, "I looked for people who were extremely +active after 88 years of age. I found that the people who use their brains don't lose them. It was that simple." + +Remember, knowing a definition or memorizing an idea is useless if we don't understand its meaning. Alfred North Whitehead said in The Aims of Education: "Education should be useful, whatever your aim in +life." + +198 + +- Two - + +MEANING + +Bad terminology is the enemy ofgood thinking. + +Warren Buffett + +Words, definitions, propositions, statements, or goals don't tell us anything. We need to understand what they mean. It is the same with knowledge. Knowledge is only valuable if it's useful and something is +only useful if we understand what it means. + +Richard Feynman's father, Melville, taught his son, the difference between knowing the name of something and knowing what goes on: + +See that bird? It's a brown-throated thrush, but in Germany it's called a halzenfugel and in Chinese they call it a chung ling and even if you know all those names for it, you still know nothing about the +bird. You only know something about people; what they call the bird. + +Now that thrush sings, and teaches its young to fly, and flies so many miles away during the summer across the country, and nobody knows how it finds its way. + +Doesn't this tell us something in the sense of learning? Words or names don't constitute knowledge. Knowing the name of something doesn't help us understand it. Since understanding implies action and +accomplishment, one way of understanding is to see what happens. Feynman illustrates: + +There is a picture of a dog, a windable toy dog, and a hand comes to the winder, and then the dog is able to move. Under the last picture, it says "What makes it move?" ... the answer I was trying to learn is +that "energy makes it move." ... + +It would be equally well to say that "God makes it move," or "spirit makes it move," or "movability makes it move." (In fact one could equally well say "energy makes it stop.") + +Look at it this way: That's only the definition of energy. It should be reversed. We might say when something can move that it has energy in it, but not "what makes it move is energy."... + +If you ask a child what makes the toy dog move, you should think about what an ordinary human being would answer. The answer is that you wound up the spring; it tries + +199 + +to unwind and pushes the gear around. What a good way to begin a science course. Take apart the toy; see how it works... + +I think, for lesson number one, to learn a mystic formula for answering questions is very bad. + +Feynman gives another example of an empty definition: "the soles of your shoes wear out because of friction." Real knowledge is: "Shoe leather wears out because it rubs against the sidewalk and the little +notches and bumps on the sidewalk grab pieces and pull them off." + +Feynman provides a test we can do to check our understanding: + +Without using the new word which you have just learned, try to rephrase what you have just learned in your own language. Without using the word "energy," tell me what you know now about the dog's motion. + +Understanding "meaning" requires that we observe and ask basic questions. + +Examples of some questions are: + +Meaning of words: What do the words mean? What do they imply? Do they mean anything? Can we translate words, ideas or statements into an ordinary situation that tells us something? An expression is always +relative. We have to judge and measure it against something. + +Meaning of an event: What effect is produced? What is really happening using ordinary words? What is it doing? What is accomplished? Under what conditions does it happen? What else does it mean? + +Causes: What is happening here and why? Is this working? Why or why not? Why did that happen? Why does it work here but not there? How can it happen? What are the mechanisms behind? What makes it happen? + +Implications: What is the consequence of this observation, event, or experience? What does that imply? + +Purpose: Why should we do that? Why do I want this to happen? + +Reason: Why is this better than that? + +Usefulness: What is the applicability of this? Does it mean anything in relation to what I want to achieve? + +Danish physicist Niels Bohr said: "Never express yourself more clearly, than you are able to think." When describing something, tell it as it is and use words that people understand, and in terms of ideas +with which they are familiar. Albert Einstein said: "If you can't explain it simply, you don't understand it well enough." Get to the point. Ask: What do I want to say? One reason for + +200 + +miscommunication can be that the words mean one thing to you and something else to the person you're talking to. + +Ask "What happens?" + +Why have Warren Buffett and Charles Munger successfully compounded the book value of Berkshire Hathaway 3700 times over the last 42 years? Why do many people lose money investing? + +The reason we invest in an economic asset like a business, apartment building, farm, or bond is to make money. But what does that mean? What is making money? What happens when we make money? + +Follow the cash. "How much cash do I get and when do I get it?" + +What happens when we make money is that we get more money back in the future than we invest today. For example, we invest $100 and get back $150. + +What determines our return from investing in an economic asset? The price we pay, how much money we get back, and when we get it back. It makes a huge difference if we get $150 back in 2 years or 10 years. +The difference in yearly return is 22% versus 4%. Our return can be measured against the expected returns from other available investment opportunities. This means that the value of an economic asset is +influenced by interest rates. If interest changes, value changes. The higher the rates, the less the value. + +If we knew for certain we would get $10 in cash every year for 5 years and we use a risk-free government bond rate of 6% as the discount rate, then the asset has a value of about $42. This means that if we +pay $42, we get a 6% average yearly rate of return. If we pay $30, our return rises to 20%. The larger the difference between an economic asset's value (e.g. $42) and the price we pay, the higher our yearly +return becomes. + +Warren Buffett says, "We use the risk-free rate merely to equate one item to another. In other words, we're looking for whatever is the most attractive. In order to estimate the present value of anything, +we're going to use a number. And, obviously, we can always buy government bonds. Therefore, that becomes the yardstick rate... to simply compare all kinds of investment opportunities across the spectrum: oil +wells, farms, whatever it may be." + +Don't pay more than what you get back in value. + +Benjamin Franklin said: "I conceive that great part of the miseries of mankind are brought upon them by the false estimates they have made of the value of things, and by their giving too much for their +whistles." One of Francois Due de + +201 + +la Rochefoucauld's maxims was: "The height of ability consists in a thorough knowledge of the true value of things." + +The key question we should ask when investing money in economic assets is: What is the expected future cash we can take out and when does it appear? How else can we know what an asset may be worth and what +kind of return we can expect at a given price? Warren Buffett says: "In the end, what you have to decide is whether you're going to value a business at $400 million, $600 million or $800 million - and then +compare that with the price." + +john wants to buy an ice cream store (it doesn't matter if it is a small ice cream store or 100 shares in a billion dollar business, the relevant reasoning is the same). + +Is this a good deal? It depends on the price John pays, and the discounted value of the cash that can be taken out of the ice cream store during its remaining life. How much cash can John take out? When can +he take it out? This depends on the amount and timing of the free cash flow that is generated by the store or how much cash he can take out (and when) without hurting the store's present position against +competition. + +Warren Buffett says of the "cash flow" numbers that are often set forth in Wall Street reports: + +These numbers routinely include (a) [reported earnings] plus (b) [depreciation, depletion, amortization, and certain other non-cash charges] - but do not subtract (c) [the average annual amount of capitalized +expenditures for plant and equipment, etc.] Most sales brochures of investment bankers also feature deceptive presentations of this kind. These imply that the business being offered is the commercial +counterpart of the Pyramids - forever state-of-the-art, never needing to be replaced, improved or refurbished. + +Some cash is always needed for reinvestment in capital expenditures for plant and equipment and working capital merely to enable a business to stay in business or maintain its unit volume and long-term +competitive position. A classic example is a retail store that needs to install air-conditioning because other stores have made the investment. It doesn't generate any extra business, but without it, the +store may lose customers to competition. + +Buffett also says that we have to watch out for certain figures: "When companies or investment professionals use terms such as "EBITDA" and "pro forma," they want you to unthinkingly accept concepts that are +dangerously flawed." + +202 + +He continues: + +Trumpeting EBITDA (earnings before interest, taxes, depreciation and amortization) is a particularly pernicious practice. Doing so implies that depreciation is not truly an expense, given that it is a +"non-cash" charge. That's nonsense. In truth, depreciation is a particularly unattractive expense because the cash outlay it represents is paid up front, before the asset acquired has delivered any benefits +to the business. Imagine, if you will, that at the beginning of this year a company paid all of its employees for the next ten years of their service (in the way they would lay out cash for a fixed asset to +be useful for ten years). In the following nine years, compensation would be a "non-cash" expense - a reduction of a prepaid compensation asset established this year. Would anyone care to argue that the +recording of the expense in years two through ten would be simply a bookkeeping formality? + +But isn't it earnings that matter for stockholders? John Burr Williams wrote in his 1938 book, The Theory of Investment Value: + +If earnings not paid out in dividends are all successfully reinvested at compound interest for the benefit of the stockholder ... then these earnings should produce dividends later; if not, then they are +money lost.... Earnings are only a means to an end, and the means should not be mistaken for the end. Therefore we must say that a stock derives its value from its dividends, not its earnings, In short, a +stock is worth only what you can get out of it... for we are discussing permanent investment, not speculative trading, and dividends for years to come, not income for the moment only. + +Warren Buffett adds, "If somebody's reinvesting all their cash flow, they better have some very big figures coming in down the road because a financial asset has to give you back a lot more cash one day in +order to justify your laying out cash for it now." + +Is value a precise figure? + +Warren Buffett says: + +Intrinsic value is an estimate rather than a precise figure, and it is additionally an estimate that must be changed if interest rates move or forecasts of future cash flows are revised. Two people looking at +the same set of facts, moreover - and this would apply even to Charlie and me - will almost inevitably come up with at least slightly different intrinsic value figures. + +203 + +Using precise numbers is, in fact, foolish; working with a range of possibilities is the better approach. + +Is there a difference between how we value different businesses? + +No matter whether a company makes telecom equipment, cars, or candy, it's still the same question: How much cash do we get and when? The name attached to the cash doesn't matter. Warren Buffett says: + +What you're trying to do is to look at all the cash a business will produce between now and judgment day and discount it back to the present using an appropriate discount rate and buy a lot cheaper than that. +Whether the money comes from a bank, an Internet company, a brick company...the money all spends the same. Why pay more for a telecom business than a brick business? Money doesn't know where it comes from. +There's no sense in paying more for a glamorous business if you're getting the same amount of money, but paying more for it. It's the same money that you can get from a brick company at a lower cost. The +question is what are the economic characteristics of the bank, the Internet company or the brick company. That's going to tell you how much cash they generate over long periods in the future. + +What ifJohn needs to invest more cash in the store? + +We have to consider the amount and timing of both cash into and from the store. As many investors in "growth" companies are well aware of, some businesses seem to need a never-ending supply of new cash. +Warren Buffett says, "Growth can destroy value if it requires cash inputs in the early years of a project or enterprise that exceed the discounted value of the cash that those assets will generate in later +years... Growth is simply a component- usually a plus, sometimes a minus - in the value equation." + +But isn't it easy going wrong in estimating the amount and timing of future cash flows in and out ofa business? + +At Berkshire, they deal with this problem in two ways. Warren Buffett says: + +First, we try to stick to businesses we believe we understand. That means they must be relatively simple and stable in character. If a business is complex or subject to constant change, we're not smart enough +to predict future cash flows. Incidentally, that shortcoming doesn't bother us. What counts for most people in investing is not how much they know, but rather how realistically they define what they don't +know. An investor needs to do very few things right as long as he or she avoids big mistakes. + +Second, and equally important, we insist on a margin of safety in our purchase price. If + +204 + +we calculate the value of a common stock to be only slightly higher than its price, we're not interested in buying. We believe this margin-of-safety principle, so strongly emphasized by Ben Graham, to be the +cornerstone of investment success. + +Warren Buffett also says that, "we try... to keep our estimates conservative." He continues: + +... take all of the variables and calculate 'em reasonably conservatively... don't focus too much on extreme conservatism on each variable in terms of the discount rate and the growth rate and so on; but try +to be as realistic as you can on these numbers, with any errors being on the conservative side. And then when you get all through, you apply the margin of safety. + +It's the same thing Berkshire does in insurance. Buffett gives an example: + +If we're trying to figure out what we should charge for, say, the chances of a 6.0 earthquake in California, we know that in the last century I think there've been 26 or so earthquakes in California that +registered 6.0 or greater. And let's forget about whether they occur in remote areas. Let's just say we were writing a policy that paid off on a 6.0 or greater quake in California, regardless of whether it +occurred in a desert and did no damage. Well, we would look at the history and we'd say, "Well, there've been 26 in the last century." + +And we would probably assume a little higher number in the next century. That'd just be our nature. However, we wouldn't assume 50 - because if we did, we wouldn't write any business. But we might assume a +little higher. IfI were pricing it myself, I'd probably say, well, I'll assume that there are going to be 30 - or maybe 32 or something like that. + +And then when I'm all through, I'll want to put a premium on it that incorporates a margin of safety. In other words, if I were to figure that the proper rate for 32 was $1 million, I would probably want to +charge something more than $1 million to build in that margin of safety. But I want to be conservative at all the levels - and then I want to have that significant margin of safety at the end. + +What can john reasonably expect the store to be worth? + +How much should John pay for the store? What future free cash flow can rationally be expected? How much cash can John take out and when? + +Warren Buffett says, "You'd try to figure out what you were laying out currently and what you're likely to get back over time, how certain you felt about getting it and how it compared to other alternatives." +He continues: "For our discount rate, we basically think in terms of the long-term government rate... But in times + +205 + +of what seem like very low rates, we might use a little higher rate." Buffett also says, "And that discount rate doesn't pay you as high a rate as it needs to." + +In 2003, Warren Buffett said, "We love owning common stocks - if they can be purchased at attractive prices... Unless, however, we see a very high probability of at least 10% pre-tax returns, we will sit on +the sidelines." + +Let's assume based on the store's history and expecting the same conditions in the future, John estimates that he can take out $300,000 in cash every year. Knowing he can always buy a risk-free government +bond, John uses a bond rate of 6% as the discount rate. He also knows he can reinvest whatever cash he can take out from the store at 6%. The value of the store is then $5 million ($300,000/0.06). + +Whatever he can pay below this figure increases his expected return. But since cash from a business can't be as certain as cash from a government bond, why should John pay $5 million? Why should John take +time and effort investing in something that gives him the same return as doing nothing? And since John can't know for certain whether expected cash flows will turn out as he expects, he should buy the store +at a price that gives him a huge margin of safety. + +If John's required rate of return is 10%, the value of the store is $3 million. + +Each person should use his own required rate of return. But whatever discount rate we use, we should always require a substantial discount from the estimated value in order to justify making the investment. + +We shouldn't engage in false precision. Warren Buffett says, "We believe that if you can pinpoint it, you're kidding yourself. Therefore, we think that when we make a decision there ought to be such a margin +of safety - it ought to be so attractive - that you don't have to carry it out three decimal places." He continues: "We are very inexact ... How certain we are is the most important part... You'd be amazed at +how inexact we are." Charles Munger says, "We never sit down, run the numbers out and discount them back to net present value... The decision should be obvious." + +We can use whatever discount rate we require and we can always compare investment opportunities with the long-term Treasury rate. But there is no point in calculating the value of the unpredictable. We need +some certainty. Ask: How much confidence do I have in the numbers? + +We can't compensate what we can't predict with a higher discount rate. Warren Buffett says: + +When we look at the future of businesses, we look at riskiness as being sort of a go/no-go valve. In other words, if we think that we simply don't know what's going to happen in the + +206 + +future, that doesn't mean it's risky for everyone. It means we don't know - that it's risky for + +us. It may not be risky for someone else who understands the business. + +However, in that case, we just give up. We don't try to predict those things. We don't say, "Well, we don't know what's going to happen. Therefore, we'll discount some cash flows that we don't even know at 9% +instead of7%." That is not our way to approach it. Once it passes a threshold test of being something about which we feel quite certain, we tend to apply the same discount factor to everything. And we try to +only buy businesses + +about which we're quite certain. + +Should john always take out whatever cash he can? + +That depends on if the return for keeping the cash in the business is higher than the return John gets if he takes it out and invests somewhere else. Why should John want to take it out if he could reinvest +the cash in the business at a higher return than 6%? And why should he not take the cash out if he can't reinvest it in the business at a higher return than 6%? + +Here is a big difference between a company controlled by John and a public company where John only owns a part of the business. He doesn't control when to take the cash out in a public company. Both in +private and public companies, cash may be reinvested at a mediocre return or into ideas that don't work. History has shown that many times reinvested cash has been wasted money and that a pay-out would have +been better. + +How much cash flow the store will generate is mainly determined by three variables: (1) Sales - how many units of ice cream will be sold at what price? (2) Operating costs - how much does it cost to make the +ice cream and conduct the business? (3) Invested capital - how much capital is needed to conduct the business? To what degree is this capital financed with debt rather than equity and at what cost? + +These variables determine what return the business earns on the capital that is invested in the store. Sales, costs, and capital need are largely determined by demand, competition from similar or substituting +products, advantages against competition and their sustainability, cost and capital efficiency, and operational effectiveness in execution. What does this mean? Let's translate it into a simple question: Does +the ice cream store have something people need or want now and in the future (demand), that no one else has (competitive advantage) or can copy or get now and in the future (sustainable) and can these +advantages be translated into business value? + +For example, why do customers choose to buy ice cream from this store rather than from somewhere else? Is it location, assortment, taste, service, + +207 + +price? What do they associate the store and its products with? What is important to customers? Why do they come back? Have their motivations changed over the years or are they likely to change over the next +10 years? What incentives can cause customers to switch to or away from the store? What threats are there? + +Warren Buffett illustrates his thinking: + +If you and I were looking at the chewing gum business (and we own no Wrigley's, so I use it fairly often in class), you'd pick a figure that you would expect unit volumes of chewing gum to grow in the next +10-20 years and you'd give me your expectations about how much pricing flexibility Wrigley's has and how much danger there is that Wrigley's market share might be dramatically reduced-you'd go through all of +that... We're evaluating the moat, the price elasticity that interacts with the moat in certain ways, the likelihood of unit demand changing in the future or management being either very bright with the cash +that they develop or very stupid with it... + +I would say you can almost measure the strength of a business over time by the agony its managers go through in determining whether a price increase can be sustained ... You can learn a lot about the +durability of the economics of a business by observing the price behavior. + +Can competitors make the store's product obsolete or copy its advantages? + +If someone puts a store next to John's and customers don't see any difference between two stores products and services, then customers are likely to buy the ice cream in the store with the lowest prices. + +Could John still make money having the lowest price? Yes, if demand exceeds supply or if John can produce and sell his ice cream at a lower cost than competition assuming of course competition doesn't want to +run its business at a loss. John must run the store with extreme cost and capital efficiency relative to the competition. Lower costs and better use of capital allows him to keep the lowest price and still +make money. + +How important is store management? + +How much cash and when John gets it is also a function of the ability and integrity of management. Management can influence owners' return by influencing the return of the business. It can influence where +capital is being employed, and under what conditions money is to be reinvested. + +When it comes to integrity, Warren Buffett says it best: + +208 + +One friend of mine said that in hiring they look for three things: intelligence, energy, and character. If they don't have the last one, the first two will kill you because, it's true, if you are going to +hire somebody that doesn't have character, you had really better hope they are dumb and lazy, because, if they are smart and energetic, they'll get you in all kinds of trouble. + +A business may look to have a huge margin of safety in price but without an able and honest management this margin may end up as an illusion. History is filled with stories about great businesses that were +destroyed by poor management. Ask: Is the company equipped with a competent and honest management that focuses on value? Will they use free cash flow for the benefit of the owners? + +But in some businesses, not even brilliant management helps. Warren Buffett shares his experiences: + +My conclusion from my own experiences and from much observation of other businesses is that a good managerial record (measured by economic returns) is far more a function of what business boat you get into +than it is of how effectively you row (though intelligence and effort help considerable, of course, in any business, good or bad). Some years ago I wrote: "When a management with a repuration for brilliance +tackles a business with a reputation for poor fundamental economics, it is the reputation of the business that remains intact." Nothing has since changed my point of view on that matter. Should you find +yourself in a chronically-leaking boat, energy devoted to changing vessels is likely to be more productive than energy devoted to patching leaks. + +Let's take another example of "what happens". This time we describe a model from chemistry and give an example of a misused word - entropy. + +At 3.54 a.m. the city of Los Angeles woke up to a 6.5 earthquake. + +Why does an earthquake crush so many structures and cause so many deaths? Why doesn't hot coffee stay hot? The answer to these questions gets to the heart of every spontaneous (means in chemistry "by itself, +without energy input") physical or chemical event in our lives. The warmth in a hot beverage is due to fast moving molecules. They collide with slower moving molecules in the (relatively colder) environment +and cause the slower ones to speed up. Energy is spread out from the hot liquid to the cup, the air, and by the currents of the air, to distant places. That is the nature of energy. + +The instant we drop a ball on the floor its energy becomes kinetic energy or energy due to movement. But the term isn't important. What happens is. All + +209 + +energy tends to spread, to become dispersed, if it is not hindered from doing so. That explains why iron rusts, why there are hurricanes, why objects break, etc. Why does a speeding truck running into a brick +wall cause enormous destruction? Its kinetic energy not only tends to spread out; it spreads out catastrophically. + +The same with the earthquake. Stress in the earth caused by the slow movement of the earth's crust floating on its hot molten energy-filled core suddenly spreads. Its potential energy is instantly changed to +kinetic energy as the earth moves. When such gigantic energy spreads, it shakes everything for miles around an epicenter. Because of that energy dispersal, not only buildings collapse, but lives are cut +short. + +Our lives are based on energy dispersal. Each second, chemicals in our body (converted within us from the food we eat and oxygen we breathe) keep our hearts beating. Our lungs pump oxygen into us and carbon +dioxide out. We are energy processing machines. We must keep spreading out energy so that we are warm and keep making chemicals so our hearts beat and muscles work and our lungs function. If these processes +are seriously interrupted - as they are in any major accident like an earthquake - we die. + +What does it mean (what happens) when we hear it was a magnitude 6.5 earthquake? The Richter scale is a logarithmic scale developed by the geophysicist Charles F. Richter and measures the amplitude (size) of +an earthquake from the recording of earthquake waves made on a seismograph. Each unit increase in the scale corresponds to a 10-fold increase in ground motion. A magnitude 7.5 earthquake produces 10 times +more ground motion than a magnitude 6.5 earthquake. But since energy causes the damage, the important difference lies in the energy release. For every unit increase, energy release increases by a factor of +about 32. A 7.5 earthquake releases about 32 times more energy than a 6.5. + +Since 1900, the biggest earthquake in the U.S. occurred in Alaska in 1964. It had a magnitude of 9.2. What is the difference in strength or energy between a magnitude 9.2 earthquake and a 6.5 earthquake? +About 11,220 times. This means that it would take 11,220 earthquakes of magnitude 6.5 to equal the energy released by a 9.2 earthquake. This explains the destructive power of big quakes. + +"Follow the energy. " + +Entropy measures how much energy is spread out in a process, or how widely spread out it becomes - at a specific temperature. Entropy is a misused word, + +210 + +often used to explain all kinds of "disorder." Disorder is certainly characteristic of many of our situations in life - failed relationships, social problems, messy desks, disorderly bedrooms, etc. However, +entropy has no relevance to these things. Only to the scientific measure of physical energy flow from being concentrated to being spread out. + +A room doesn't have a tendency to get messy by itself. Some outside energy is needed. It is the energy concentrated in our muscles that is being spread and causes our desks to be messed up. There is no energy +being spread out in the papers themselves. As Chemistry Professor Frank Lambert says, "There isn't any 'tendency of objects to become disorganized' in nature any more than bank tellers have a 'tendency to +give money to robbers' without a gun." + +That energy tends to spread explains why metal rusts, why things break and wear down. Since energy always flows from being concentrated to less concentrated; physical objects and chemical systems deteriorate, +break or become destroyed. But these things don't happen immediately or spontaneously. The repetition of time and energy must be considered. A small push (or activation energy) is needed to start a reaction. +Gasoline needs a spark or flame to react with oxygen. We need a match to light a fire. For example, it took a single spark to initiate the reaction between hydrogen gas and oxygen, causing the airship +Hindenburg to burn. It takes movements of wind and warm moisture from a tropical ocean to form a hurricane. It takes oxygen and moisture to make iron rust. It takes energy to make wood rot. And this process +can be delayed. This happens if we for example paint iron to prevent rusting. Painting keeps oxygen away from the iron so a reaction can't happen. + +These examples show how by observing "what happens" we can better understand reality. + +211 + +- THREE - + +SIMPLIFICATION + +We have a passion for keeping things simple. + +- Charles Munger + +john fears that being simple reduces his importance. + +Former General Electric CEO Jack Welch said: "You can't believe how hard it is for people to be simple, how much they fear being simple. They worry that if they're simple, people will think they're +simple-minded. In reality, of course, it's just the reverse. Clear tough-minded people are the most simple." + +Warren Buffett agrees: "We haven't succeeded because we have some great, complicated systems or magic formulas we apply or anything of the sort. What we have is just simplicity itself." Charles Munger adds: +"If something is too hard, we move on to something else. What could be more simple than that?" + +Simplify the way we do things + +It's amazing how people even today use a computer to do something you can do with a pencil and paper in less time. + +- Richard Feynman (from No Ordinary Genius) + +Make problems easier to solve. Turn complicated problems into simpler ones. Eliminate everything except the essentials. Break down a problem into its components but look at the problem holistically. Draw a +picture of the problem. Put down on a paper the key factors and their relationship. Charles Munger says: "I generally try to approach complex tasks by first disposing of the easy decisions." + +Be problem-oriented. Not method-oriented. Use whatever works. Why? + +Because the result is what matters, not the method we use to arrive at it. + +Look for good enough solutions appropriate to the problem at hand. Not perfection and beauty. + +Make fewer and better decisions. Why? Because it forces us to think more on each decision and thereby reduces our chance of mistakes. Warren Buffett gives another compelling reason: + +212 + +Charlie and I decided long ago that in an investment lifetime, it's just too hard to make hundreds of smart decisions. That judgment became ever more compelling as Berkshire's capital mushroomed and the +universe of investments that could significantly affect our result shrank dramatically. Therefore, we adopted a strategy that required our being smart + +- and not too smart at that - only a very few times. + +William James said: "The art of being wise is the art of knowing what to overlook." Charles Munger tells us about the importance of eliminating nonsense: "Part of that [having uncommon sense], I think, is +being able to tune out folly, as distinguished from recognizing wisdom. You've got whole categories of things you just bat away so your brain isn't cluttered with them. That way, you're better able to pick up +a few sensible things to do." + +Warren Buffett agrees: + +Yeah, we don't consider many stupid things. I mean, we get rid of 'em fast... Just getting rid of the nonsense - just figuring out that if people call you and say, ''I've got this great, wonderful idea'', you +don't spend 10 minutes once you know in the first sentence that it isn't a great, wonderful idea... Don't be polite and go through the whole process. + +Often we try to get too much information, including misinformation, or information of no use to explain or predict. We also focus on details and what's irrelevant or unknowable and overlook the obvious +truths. Dealing with what's important forces us to prioritize. There are often just a few actions that produce most of what we are trying to achieve. There are only a few decisions of real importance. + +More information doesn't equal more knowledge or better decisions. And remember that today we not only have access to more information, but also misinformation. Charles Munger says: "The harder you work, the +more confidence you get. But you may be working hard on something that is false." + +In Arthur Conan Doyle's The Reigate Puzzle, Sherlock Holmes says: "It is of the highest importance in the art of detection to be able to recognize, out of a number of facts, which are incidental and which +vital." + +Turn off the noise or what's irrelevant and look at the big picture. Ask: Why am I doing this? What really matters? What is important for what I want to achieve? Will more information affect my decision? +Don't collect data randomly. Start with why the particular information is needed in the first place. + +When asked if he used a computer, Charles Munger said: + +213 + +I'm a follower of what I call the Thomas Hunt Morgan school. Morgan was one of the great biologists in the history of the world who figured out a lot of genetics [Morgan established that chromosomes carried +the units of inheritance] with very slender resources in a so-called "fly room" - first at Columbia and then at Caltech. And when Morgan reached Caltech, he did something that was very peculiar. He banned the +Friden calculator + +- which was the computer of that age - from the biology department. Everybody else at Caltech used the Friden calculator endlessly for all kinds of statistical correlations and much else. Morgan banned it. + +And they asked, "Why are you doing this?" He said, 'Tm so located in life that I'm like + +a gold miner in 1848 who could just walk along the banks of the river and pick up enormous nuggets of gold with organized common sense. And as long as I can do this, I'm not going to use scarce resources in +placer mining." + +Well, that's the way I go at life. I think if you get the big points with organized common sense, it's amazing the placer mining you never have to do ... + +But is there still enormous gain to be made with organized common sense that doesn't require a computer? I think the answer is "yes." Are there dangers in getting too caught up in the minutiae of using a +computer so that you miss the organized common sense? There are huge dangers. There'll always be huge dangers. People calculate too much and think too little. + +Avoid certain things + +There are things that we stay away from. Were like the man who said he had three baskets on his desk: in, out and too tough. We have such baskets - mental baskets - in our office. An awfal lot ofstujfgoes in +the "too tough" basket. + +- Charles Munger + +Deal with the situations in life by knowing what to avoid. Reducing mistakes by learning what areas, situations and people to avoid is often a better use of time than seeking out new ways of succeeding. Also, +it is often simpler to prevent something than to solve it. 13th Century jurist and priest Henry de Bracton said: "An ounce of prevention is worth a pound of cure." + +Warren Buffett describes how he and Charles Munger do it: + +Easy does it. After 25 years of buying and supervising a great variety of businesses, Charlie and I have not learned how to solve difficult business problems. What we have learned is to avoid them. To the +extent we have been successful, it is because we concentrated on identifying one-foot hurdles that we could step over rather than because we acquired any + +214 + +ability to clear seven-footers. The finding may seem unfair, but in both business and investments it is usually far more profitable to simply stick with the easy and obvious than it is to resolve the +difficult. + +We basically have the attitude that you can't make a good deal with a bad person. We don't try to protect ourselves by contracts or all kinds of due diligence - we just forget about it. We can do fine over +time dealing with people we like and admire and trust. + +And the bad actor will try to tantalize you in one way or another. But you won't win. It pays to just avoid him. We started out with that attitude. However, one or two experiences have convinced us even more +so that that's the way to play the game. + +Charles Munger follows up with: + +I've heard Warren say since very early in his life that the difference between agood business and a bad one is that a good business throws up one easy decision after another, whereas a bad one gives you +horrible choices - decisions that are extremely hard to make: "Can it work?" "Is it worth the money?" + +One way to determine which is the good business and which is the bad one is to see which one is throwing management bloopers - pleasant, no-brainer decisions - time after time after time. + +Focus leads to understanding and efficiency + +Those who attain to any excellence commonly spend life in some single pursuit, for excellence is not often gained upon easier terms. + +- Samuel Johnson + +It is impossible for our brain to think too many things at the same time and expect to do well. Shifting our mental attention between tasks costs time and comprehension, especially when we switch between more +complicated and unfamiliar tasks. + +Actions and decisions are simpler when we focus on one thing at the time. Publilius Syrus said: "To do two things at once is to do neither." If we only have one thing to focus on, we tend to do it well and +build knowledge. + +Always think with a purpose in mind. Ask: What do I want to achieve or avoid? Is focus important in business and for management? Warren Buffett says: + +A... serious problem occurs when the management of a great company gets sidetracked and neglects its wonderful base business while purchasing other businesses that are so-so + +215 + +or worse... (Would you believe that a few decades back they were growing shrimp at Coke and exploring for oil at Gillette?) Loss of focus is what most worries Charlie and me when we contemplate investing in +businesses that in general look outstanding. All too often, we've seen value stagnate in the presence of hubris or of boredom that caused the attention of managers to wander ... + +I love focused management ... And when you lose that focus - it shows... GEICO + +actually started fooling around in a number of things in the early 1980s. And they paid a price for it - actually a very big price. They paid a direct price in terms of the cost for those things - because +they almost all worked out badly. And then they paid an additional price in terms of the loss of focus on the main business. + +Focus on what you can know and that makes a difference + +Before attacking a problem ask if it is worth solving or spending time on. Warren Buffett explains one of the reasons for his and Charles Munger's success in life and business: + +There are two questions you ask yourself as you look at the decision you'll make. A) is it knowable? B) is it important? Ifit is not knowable, as you know there are all kinds of things that are important but +not knowable, we forget about those. And if it's unimportant, whether it's knowable or not, it won't make any difference. We don't care. + +What's knowable and important? And what can be translated into useful action? Some important things we can't know. Like where the stock market is going. Other things we can know but they are not important. + +Ask the right questions + +The formulation ofa problem is often more essential than its solution, which may be merely a matter of mathematical or experimental skill. + +- Albert Einstein + +Sometimes it is harder to understand a problem than to solve it. Asking the important questions may help. Start with basic questions like: What does it mean? What is the simplest example? What is the number +one question? How can I tell if the answer is right? Can I come up with an example that makes it clear what the problem is? + +But it is not enough to ask the right questions. We must look at the right place and ask the right person. We can't rely too much on assumptions since we can't be sure that someone else's assumptions are the +same as ours, unless we ask them to explain. + +216 + +Patience + +It's not that I'm so smart; it's just that I stay with problems longer. + +Albert Einstein + +The best thinking is often done when there is no stress, time limit, threats, or judging. Thinking takes time and the simple truths often reveal themselves when we're doing something else. + +We are more likely to solve a specific problem or gain new insight if we leave the problem alone for awhile and let our subconscious mind work. This is well illustrated by the physicists Albert Einstein and +Leopold Infeld: + +In nearly every detective novel since the admirable stories of Conan Doyle there comes a time where the investigator has collected all the facts he needs for at least some phase of his problem. These facts +often seem quite strange, incoherent, and wholly unrelated. The great detective, however, realizes that no further investigation is needed at the moment, and that only pure thinking will lead to a correlation +of the facts collected. So he plays his violin, or lounges in his armchair enjoying a pipe, when suddenly, by Jove, he has it! + +Roger Lowenstein describes Warren Buffett in [3mBuffett: The Making of an American Capitalist: [0m"Buffett's genius was largely a genius of character - of patience, discipline and rationality...His talent sprang +from his unrivaled independence of mind and ability to focus on his work and shut out the world." Have patience in waiting for opportunities. Resist the temptation to always do something. If we are in a +hurry, it's easier to make misjudgments. This is key in investing. Warren Buffett says, "In allocating capital, activity does not correlate with achievement. Indeed, in the fields of investments and +acquisitions, frenetic behavior is often counterproductive." He continues: "If you feel like you have to invest every day, you're going to make a lot of mistakes. It isn't that kind of a + +business. You have to wait for the fat pitch." Charles Munger adds: + +A few major opportunities, clearly recognizable as such, will usually come to one who continuously searches and waits, with a curious mind, loving diagnosis involving multiple variables. And then all that is +required is a willingness to bet heavily when the odds are extremely favorable, using resources available as a result of prudence and patience in the past. + +217 + +- FOUR - + +RULES AND FILTERS + +Rules are for the obedience of fools and the guidance of wise men. + +David Ogilvy (Advertising executive, 1911-1999) + +What can help us avoid problems and act as guidelines when making decisions? Based on our knowledge of reality and our personal situation we should establish some "what to do" and "what to avoid" rules. + +Charles Munger gives an example of a rule: + +Any time anybody offers you [3manything [0mwith a big commission and a 200-page prospectus, don't buy it. Occasionally, you'll be wrong if you adopt "Munger's Rule". However, over a lifetime, you'll be a long way +ahead - and you will miss a lot of unhappy experiences that might otherwise reduce your love for your fellow man. + +Another rule comes from Benjamin Franklin: "To apply myself industriously to whatever business I take at hand, and not divert my mind from my business by any foolish project of growing suddenly rich; for +industry and patience are the surest means of plenty." + +Other rules could be, "Walk away from anything I don't understand or can't quantify or doesn't work. Only deal with people I trust. " + +Warren Buffett provides us with guidelines on how to win in insurance, which applies to other areas as well: + +What counts in this business is underwriting discipline. The winners are those that unfailingly stick to three key principles: + +They accept only those risks that they are able to properly evaluate (staying within their circle of competence) and that, after they have evaluated all relevant factors including remote loss scenarios, carry +the expectancy ofprofit. These insurers ignore market-share considerations andare sanguine about losing business to competitors that are offering foolish prices or policy conditions. + +They limit the business they accept in a manner that guarantees they will suffer no aggregation of losses.from a single event or.from related events that will threaten their solvency. They ceaselessly search +for possible correlation among seemingly-unrelated risks. + +218 + +3. They avoid business involving moral risk: No matter what the rate, trying to write good contracts with bad people doesn't work. While most policyholders and clients are honorable and ethical, doing +business with the few exceptions is usually expensive, sometimes extraordinarily so. + +I have known the details of almost every policy that Ajit [Ajit Jain] has written... and never on even a single occasion have I seen him break any of our three underwriting rules. His extraordinary +discipline, of course, does not eliminate losses; it does, however, prevent foolish losses. And that's the key: Just as in the case of investing, insurers produce outstanding long term results primarily by +avoiding dumb decisions, rather than by making brilliant ones. + +Filters + +We really can say no in 10 seconds or so to 90% + of all the things that come along simply because we have these filters. + +- Warren Buffett + +Filters help us prioritize and figure out what makes sense. + +When we know what we want, we need criteria to evaluate alternatives. Ask: What are the most critical (and knowable) factors that will cause what I want to achieve or avoid? Criteria must be based on evidence +and be reasonably predictive, i.e., we must do better than chance by relying on them. Try to use as few criteria as necessary to make your judgment. Then rank them in order of their importance and use them as +filters. Set decision thresholds in a way that minimizes the likelihood of false alarms and misses (in investing, choosing a bad investment or missing a good investment). Consider the consequences of being +wrong. For example, in medicine, a threshold depends on factors such as the prevalence of a condition, its seriousness, the availability of corrective measures, and the emotional and financial costs of false +alarms. + +Past criminal and prison records are more reliable than expert criminologists in predicting success on parole. + +Studies show that in some fields, when based on the same evidence, a more mechanical prediction process involving a small number of relevant variables is more reliable than the predictions of trained and +experienced experts. This has been shown in diagnoses of medical conditions, predictions of academic performance, in determining gambling odds, and loan and credit risk. Why does it work better? Because we +humans are not always consistent. As we have seen, recent experiences, suggestions, or how information is presented may influence us. Add to this our natural limitations in memory, attention, and processing. + +219 + +More information doesn't mean we are better off. Sometimes extra information is useless and confusing. + +A man is rushed to a hospital in the throes ofa heart attack. The doctor needs to decide whether the victim should be treated as a low risk or high-risk patient. + +Criteria don't have to be numerous or complicated. Late Statistics Professor Leo Breiman and colleagues at University of California, Berkeley, developed a method to classify high-risk heart attack patients +using only a maximum of 3 variables. Blood pressure, age and sinus tachycardia (rapid heartbeat). + +If a patient's minimum systolic blood pressure over the initial 24-hour period is less than 91, he is immediately classified as high risk. If not, the second variable is age. If the patient is over 62.5 years +old, then one more variable - sinus tachycardia + +is needed to classify him as high or low risk. If the patient displays sinus tachycardia he is classified as high risk. Thus, the doctor needs to answer three yes no questions to reach a decision. The method +is more accurate in classifying high risk heart attack patients than complex statistical classification methods. + +At a press conference in 2001, when Warren Buffett was asked how he evaluated new business ideas, he said he used 4 criteria as filters. + +Can I understand it? If it passes this filter, + +Does it look like it has some kind of sustainable competitive advantage? If it passes this filter, + +Is the management composed of able and honest people? Ifit passes this filter, + +Is the price right? If it passes this filter, then we write a check + +What does Warren Buffett mean by "understanding?" Predictability: "Our definition of understanding is thinking that we have a reasonable probability of being able to assess where the business will be in 10 +years." He continues: + +The only way we know how to make money is to try and evaluate businesses. And if we can't evaluate a carbon steel company, we don't buy it. It doesn't mean it isn't a good buy. It doesn't mean it isn't +selling for a fraction of what its worth. It just means that we don't know how to evaluate it. If we can't evaluate the sense of putting in a chemical plant or something in Brazil, we don't do it... + +We understand the product. We understand what it does for people. We just don't know [what its economics will be] 10 years from now... You can understand steel. You can understand homebuilding. But if you +look at a homebuilder and try to think where the economics of it is going to be in five or 10 years, that's another question. It's not a question + +220 + +of understanding the product they turn out, the means they use to distribute it- all of that sort of thing - it's the predictability of the economics of the situation 10 years out. + +Let's take an example where we combine rules and filters. Reality often shows that one cause of problems is getting involved with wrong people. A rule could therefore be: "Avoid low quality people." As a +consequence a filter may be: "Good track record and character traits." Then we look for dues and ask questions designed to answer the question: "High or low grade individual?" + +Elimination + +Elimination is a great conservator of effort. For example, place the burden of proof on statements that contradict basic scientific ideas. Eliminate situations that may cause great sorrow, what is not +important or knowable, what can't happen or be achieved, what can't usefully be predicted or explained, what can't be tested, what is already disproved, the easy decisions, the wrong assumptions, what we +can't do something about or problems where we don't have any competence. + +Science works by elimination. To avoid drowning in low-information observations or experiments, scientists think in advance about what the most important and conclusive experiments would be: What are we +trying to achieve or prove, and how can we reach these ends? What can't happen? This way, they narrow down the possibilities. It is similar to what Warren Buffett told us in Part One - eliminate possibilities +and get down to the few that have any chance of success. Look for certain things that narrow down the possibilities. + +Checklist procedures + +Air carrier cockpit checklists to be reviewed in an effort to ensure that each list provides a means of reminding the crew, immediately prior to takeoff, that all items critical for safe flight have been +accomplished. + +- National Transportation Safety Board, 1969 + +In 1987, Northwest Airlines flight 255 crashed shortly after take-off All 155 persons aboard expect one were killed A federal report concluded that the probable cause of the accident was the flight crew's +failure to use the taxi checklist to ensure that the flaps and slats were extended for takeoff. Contributing to the accident was the absence of electrical power to the airplane's takeoff warning system, which +consequently could not warn the flight crew that the airplane was not configured properly for takeoff. Use checklist procedures. Together with other tools they help us reduce the + +221 + +chance of harm. Concentrate on the critical items. If we don't check for them we may get harmed. Pilots call these the "killer items." + +Charles Munger suggests using models in a checklist fashion: + +Generally speaking, I think you need mental models - and what I call checklist procedures + +where you take a worthwhile list of models and run right down them: "Is this here? Is that here?" and so on and so on ... Now if there are two or three items that are very important chat aren't on your +checklist - well, if you're an airplane pilot, you can crash. Likewise, if you're trying to analyze a company without using an adequate checklist, you may make a very bad investment. + +Some issues to think about when designing checklists are: + +Different issues need different checklists. + +A checklist must include each critical item necessary for "safety'' and avoiding "accidents" so we don't need to rely on memory for items to be checked. + +Readily usable and easy to use. + +Agree with reality. + +Contributing to the accident was the captain's over-reliance on automated flight systems. + +Avoid excessive reliance on checklists. They may sometimes give us a false sense of security. Checklists work well as long as what may happen can be foreseen. But the unexpected sometimes happens. An +unmentioned item may be the core cause of a problem. + +Doing something according to pre-established rules, filters and checklists often makes more sense than doing something out of pure emotion. But we can't have too many rules, filters or items without thinking. +We must always understand what we're trying to accomplish. + +222 + +- FIVE - + +GOALS + +Our plans miscarry because they have no aim. When a man does not know what harbor he is headingfor, no wind is the right wind. + +- Lucius Annaeus Seneca + +"Why doesn't our employee, Tom, perform well?" + +Often we are surprised when people don't perform as we expect. + +How does Tom perceive he is being measured and rewarded? What does he perceive is expected of him? Do we give him mixed messages? What skills, knowledge and information does he need? Does he have those? What +response do we give him about his performance? + +Tom: "I have the right knowledge and understand the goal. I also know how to achieve the goal and why my way makes the most sense. I have the authority to make the relevant decisions and can measure the +outcome continuously. If I achieve the goal, I will be rewarded. I decide the amount of reward I will get. If I don't accomplish the goal, I lose my job. Since I have the responsibility, it is only right that +I face the consequences." + +Have goals that cause what we want to accomplish. Do we know what we want to achieve and why? fu Aristotle said: ''Are we not more likely to hit the mark if we have a target?" How can we make the right +decision if we don't know what we want to achieve? Even if we don't know what we want, we often know what we don't want, meaning that our goal can be to avoid certain things. + +Meaningful goals need to be backed by reasons as a way of testing that we set the right goal. Goals should be: + +Clearly defined. Don't say: "I want to have a better life." Be concrete. For example: "I want a new Volvo." + +Focused on results. + +Realistic and logical - what can and can't be achieved? Low goals may produce low performance and unrealistic goals may cause people to cheat. Lucius Annaeus Seneca said we should: "Never work either for +useless goals, or impossible ones." + +Measurable. + +223 + +Tailored to our individual needs. + +Subject to change. Ask: Given our current objective, what is the best course of action to take? + +Goals also need target dates and control stations measuring the degree to which the goal is being achieved. + +Do we know what causes our goal to be achieved? We can't achieve what we want if we don't understand what makes it happen. And are we sure our goal is the right one for what we finally want to achieve? + +Warren Buffett and Charles Munger elaborated on the issue of the energy crisis at the 2001 Berkshire Hathaway Annual Meeting: + +In power systems we need surplus of capacity. And how do we get that? By giving people an incentive for having extra capacity. A power business can't be punished for not having excess capacity and can't be +rewarded for having less then what is needed. + +We need three things for this not to happen again. One is that we need reasonable efficiency in operations. Secondly, since it does tend to have in many situations monopoly characteristics, we want something +that produced a fair return, but not a great return, on capital - enough to attract new capital. And third, we need a margin of safety or a little more capacity than needed. And we need the whole equation. + +Always ask: What end result do I want? What causes that? What factors have a major impact on the outcome? What single factor has the most impact? Do I have the variable(s) needed for the goal to be achieved? +What is the best way to achieve my goal? Have I considered what other effects my actions will have that will influence the final outcome? + +When we solve problems and know what we want to achieve, we need to prioritize or focus on the right problems. What should we do first? Ask: How serious are the problems? Are they fixable? What is the most +important problem? Are the assumptions behind them correct? Did we consider the interconnected ness of the problems? The long-term consequences? + +Since big effects - bad or good - happen when we optimize some factors or combine many factors, we should use whatever factors necessary to achieve our goal. + +224 + +- SIX - + +ALTERNATIVES + +Ifyou've got two suitors who are really eager to have you and one is way the hell better than the other, you do not have to spend much time + +with the other. And that's the way we filter out buying opportunities. + +- Charles Munger + +"Allocate the money to us!" + +How should we best allocate our scarce resources? TransCorp has ten different projects to choose from. Should they invest in all? Should each project get the same amount of funding? People, money, time, +talent and other resources are limited. They also have alternative uses. Some options are also better than others. + +Opportunity cost + +"I weigh my use of capital and time against other available alternate uses. " + +One filter that can be used to measure choices against each other is our own personal opportunity cost. Our time and money are limited. If we make a decision to do one thing we are deciding not to do some +other available thing. Every minute we choose to spend on one thing is a minute unavailable to spend on other things. Every dollar we invest is a dollar unavailable for other available investments. If we +decide to spend money today instead of investing for the future we give up the opportunity to spend more in the future. Ifl decide to play golf today I miss the opportunity to finish this book on time. If I +write, I miss the opportunity to spend time with my children. Since children grow up, this opportunity has a time limit. + +Choices have costs. Even understanding has an opportunity cost. If we understand one thing well we may understand other things better. The cost of using a limited resource like time, effort and money for a +specific purpose, can be measured as the value or opportunity lost by not using it in its best available alternative use (assuming it achieves the same purpose). + +Do you choose to work or go to college? + +What is the real cost of choosing one alternative in favor of another? To use a + +225 + +somewhat changed example from Warren Buffett: What is the real cost of not having a college education? What is the difference in income over a lifetime between having an education or not? If we ignore the +non-economic benefits of having an education, this difference in income discounted to graduation day is the value of the education or the real cost of not having an education. + +What is our time worth? Do we spend ten hours doing repairs on our house or do we use a carpenter? The real cost of doing the repairs ourselves is the money that we would have earned doing something else. + +Does "free health care" mean it is really ftee? + +No, had it not been free, the resources used for providing free health care could have been used for something else. Often we only see the benefits of government spending. We don't see what is prevented from +happening or that resources are diverted from alternative uses. + +"Employ 3 more sales representatives in Montana. " + +Should TransCorp take the time, money and talent to build a market presence in Montana? The real cost of doing that is the value of the time, money and talent used in its best alternative use. Maybe +increasing their presence in a state where they already have a market share is creating more value. Sometimes it is more profitable to marginally increase a cost where a company already has an infrastructure. +Where do they marginally get the most leverage on resources spent? Always ask: What is the change of value of taking a specific action? Where is it best to invest resources from a value point of view? + +john's return ftom the investment was a meager I%. + +The 10-year $100,000 investment in the private partnership promised a yearly return of 15%. John's next best available investment at the time was a long-term + +U.S. government bond yielding 6%. 10 years later reality kicked in. He got back + +$110,000. His yearly return was only 1%. If he hadn't made the investment back then, but had earned returns comparable with the government bond, John would now have $179,000 (pretax) instead of the $110,000 +(pretax). His real cost of doing this investment was $69,000. The money invested tied him in other ways. This doesn't include the mental stress he experienced during the ride. + +We all have a lot of things we like: our spouse, job, house, car, investments, etc. When we decide whether to change something, we should measure it against the best of what we already have. + +A complementary filter to evaluate alternatives is to list their respective pros + +226 + +and cons and then weigh all the points. Charles Darwin did this in order to decide whether to marry. Warren Buffett tells us what to look for in a spouse: "Look for someone who will love you unconditionally +and will subtly encourage you to be better than you thought you can be." + +We can also weigh alternatives the way Benjamin Franklin did. Make up a list of reasons for and against and assign them weights. + +All decisions are not equally important. Some decisions have a greater influence on our lives. A decision we make today that will influence our lives ten years from now is far more important than one that +will influence us only today. If we make a mistake in choosing the wrong vacation, the consequences over time will most likely be minor. But if, for example, we choose the wrong spouse, the wrong education, +career, friends, or investment, it may haunt us a long, long time. + +227 + +- SEVEN - + +CONSEQUENCES + +The key thing in economics, whenever someone makes an assertion to you, is to always ask, "And then what?" Actually, it's not such a bad idea to ask it about everything. But you should always ask, "And then +what?" + +- Warren Buffett + +John told the CEO of TransCorp: "We see the immediate benefits of investment in machines. We don't see competitive actions and that all the benefits go to the customer." + +"In the department of economy, an act, a habit, an institution, a law, gives birth + +not only to an effect, but to a series of effects," wrote the French journalist economist Claude Frederic Bastiat in his 1850 essay, ThatWhich is Seen, and That Which is Not Seen. He continues: + +Of these effects, the first only is immediate; it manifests itself simultaneously with its cause + +- it is seen. The others unfold in succession - they are not seen... Between a good and a bad economist this constitutes the whole difference - the one takes account of the visible effect; the other takes +account both of the effects which are seen, and also of those which it is necessary to foresee. + +Consider secondary and long-term effects of an action. Charles Munger points out that in a commodity business or in a business earning substandard returns, + +All of the advantages from great improvements are going to flow through to the customers ... the people who sell the machinery - and, by and large, even the internal bureaucrats urging you to buy the +equipment - show you projections with the amount you'll save at current prices with the new technology. However, they don't do the second step of the analysis-which is to determine how much is going to stay +home and how much is just going to flow through to the customer. + +I've never seen a single projection incorporating that second step in my life. And I see them all the time. Rather, they always read: "This capital outlay will save you so much money that it will pay for +itself in three years." So you keep buying things that will pay for + +228 + +themselves in three years. And after 20 years of doing it, somehow you've earned a return of only about 4% per annum. That's the textile business. + +And it isn't that the machines weren't better. It's just that the savings didn't go to you. The cost reductions came through all right. But the [3mbenefit [0mof the cost reductions didn't go to the guy who bought +the equipment. + +Warren Buffett tells us about the illusionary benefits: + +Many of our competitors ... were stepping up to the same kind of expenditures and, once enough companies did so, their reduced costs became the baseline for reduced prices industrywide. Viewed individually, +each company's capital investment decision appeared cost-effective and rational; viewed collectively, the decisions neutralized each other and were irrational. + +Whenever we install a policy, take an action or evaluate statements, we must trace the consequences. When doing so, we must remember four key things: + +Pay attention to the whole system. Direct and indirect effects, + +Consequences have implications or more consequences, some which may be unwanted. We can't estimate all possible consequences but there is at least one unwanted consequence we should look our for, + +Consider the effects offeedback, time, scale, repetition, critical thresholds and limits, + +Different alternatives have different consequences in terms of costs and benefits. Estimate the net effects over time and how desirable these are compared to what we want to achieve. + +We can't get something/or nothing. + +Take the issue on alternative energy sources. Some relevant headlines when thinking about alternatives: Energy used versus usable energy produced (considering the entire production process)? Infrastructure +requirements? Scalable? Transport and storage? Costs (considering subsidies)? Who pays? Environmental benefits and costs? Sustainability? Consequences over time? Degree of difficulty in properly evaluating +all the factors involved? Consequences of being wrong? + +Judge an action by its net consequences over time considering the whole system. Follow up changes in individual variables by determining how the rest of the system will respond over time. Reducing risk in one +area may increase it in + +229 + +another. Changes in one variable may change the entire system. One change may cause another change causing another, etc. This includes considering short and long-term consequences since there may be a long +time between an action and its full effects. + +Marcus Tullius Cicero said: "Extreme justice is extreme injustice." Some systems should be made deliberately a little unfair if they carry better consequences for us all. Charles Munger tells us about the +Navy model - a rule with net benefits: + +If you're a captain in the Navy and you've been up for 24 hours straight and have to go to sleep and you turn the ship over to a competent first mate in tough conditions and he takes the ship aground - +clearly through no fault of yours - they don't court martial you, but your naval career is over. + +Napoleon said he liked luckier generals - he wasn't into supporting losers. Well, the Navy likes luckier captains. + +You can say, "That's too tough. That's not law school. That's not due process." Well, the Navy model is better in its context than would be the law school model. The Navy model really forces people to pay +attention when conditions are tough - because they know that there's no excuse. Very simply, if your ship goes aground, your career is over. + +"It doesn't matter whether it was your fault or not. Nobody's interested in your fault. It's just a rule that we happen to have - for the good of all, all effects considered." + +I like some rules like that - I think that the civilization works better with some of these no-fault rules. But that stuff tends to be anathema around law schools. "It's not due process. You're not really +searching for justice." + +Well, I am searching for justice when I argue for the Navy rule - for the justice of fewer ships going aground. Considering the net benefit, I don't care if one captain has some unfairness in his life. After +all, it's not like he's being court marshalled. He just has to look for a new line of work. And he keeps vested pension rights and so on. So it's not like it's the end of the world. + +230 + +- EIGHT - + +QUANTIFICATION + +To talk sense, is to talk in quantities. It is no use saying that the nation is large, + +- [3mHow large? It is no use saying that radium is scarce, [0m- [3mHow scarce? [0m-Alfred North Whitehead (from The Aims of Education) + +Most aspects of our life depend on our ability to quantify and understand patterns and relationships, proportions, or magnitudes. What does math do? It helps us develop consequences, and evaluate when things +make sense. And math is stable. Two plus two is four was true 1 million years ago and will be true 1 million years from today. + +When we translate something into numbers we can make comparisons. How can we evaluate if a decision is intelligent or not if we can't measure it against a relevant and important yardstick? + +Some things can't be measured exactly, so estimating a range is the next best alternative. + +"It is better to be roughly right than precisely wrong," said J.M. Keynes. Don't overweigh what can be counted and underweigh what cannot. Beware of false concreteness - often we believe that data based on +figures with lots of decimal places are more accurate than words alone. Charles Munger says: + +You've got a complex system, and it spews out a lot of wonderful numbers that enable you to measure some factors. But there are other factors that are terribly important and there's no precise numbering you +can put to these factors. You know they're important but you don't have the numbers. Well, practically everybody overweighs the stuff that can be numbered, because it yields to the statistical techniques +they're taught in academia, and doesn't mix in the hard-to-measure stuff that may be more important. + +Let's illustrate the importance of quantification with examples from the world of business and investing. + +How much capital is needed to produce a dollar of cash flow? + +Does return on invested capital make a difference? Assume two businesses - X + +231 + +and Y - generate the same cash earnings of $10 million and "perpetual" growth of 5%. The difference lies in how much capital they use to produce these earnings. X needs $100 million and Y $40 million. This +means that their return on invested capital is 10% respective 25%. This also means that they differ in the free cash flow (after reinvesting) or distributable cash they generate. X generates + +$5 million and Y $8 million. Return on invested capital makes a difference in value. + +Business X + +Business Y + +Invested capital + +100 + +40 + +Free cash flow + +10 + +10 + +Reinvested capital + +-5 + +-2 + +Return on reinvested capital + +10% + +25% + +Available cash flow for distribution + +5 + +8 + +Value at 10% discount rate + +100 (5/(0.1-0.05)) + +160 + +Warren Buffett describes what businesses are best to own: + +Leaving the question of price aside, the best business to own is one that over an extended period can employ large amounts of incremental capital at very high rates of return. The worst business to own is one +that must, or will, do the opposite - that is, consistently employ ever-greater amounts of capital at very low rates of return. + +Should higher earnings automatically impress us? + +Warren Buffett gives an example from one of Berkshire's subsidiaries: + +While an increase in earnings from $8 million to $72 million sounds terrific - and usually is -you should not automatically assume that to be the case. You must first make sure that earnings were not +depressed in the base year. If they were instead substantial in relation to capital employed, an even more important point must be examined: how much additional capital was required to produce the additional +earnings? + +We need to understand what is behind the numbers. Warren Buffett says that, "return on beginning equity capital" is "the most appropriate measure of single year managerial performance. Informed use of that +yardstick, however, requires, an understanding of many factors, including accounting policies, historical carrying values of assets, financial leverage, and industry conditions." + +We can't expect to get a higher return on investment over time than the + +232 + +underlying business produces on its invested capital over time. Charles Munger says: + +Over the long term, it's hard for a stock to earn a much better return than the business which underlies it earns. If the business earns 6% on capital over 40 years and you hold it for that 40 years, you're +not going to make much different than a 6% return - even if you originally buy it at a huge discount. Conversely, if a business earns 18% on capital over 20 or 30 years, even if you pay an expensive looking +price, you'll end up with a fine result. + +Few companies can manage, over a ten to twenty-year period, to keep earning high returns on 20% or more on invested capital while reinvesting all or most of their earnings. Changes in the competitive arena, +buyer habits, and the environment will make that almost a certainty. + +Warren Buffett reveals the limits of earnings growth and how lofty predictions lead to dumb behavior: + +Examine the record of, say, the 200 highest earning companies from 1970 or 1980 and tabulate how many have increased per-share earnings by 15% annually since those dates. You will find that only a handful +have. I would wager you avery significant sum that fewer than 10 of the 200 most profitable companies in 2000 will attain 15% annual growth in earnings-per-share over the next 20 years. + +He continues: + +Finally, be suspICtous of companies that trumpet earnings projections and growth expectations. Businesses seldom operate in a tranquil, no-surprise environment, and earnings simply don't advance smoothly +(except, of course, in the offering books of investment bankers). + +Charlie and I not only don't know today what our businesses will earn [3mnext year [0m- we don't even know what they will earn [3mnext quarter. [0mWe are suspicious of those CEOs who regularly claim they do know the +future - and we become downright incredulous if they consistently reach their declared targets. Managers that always promise to "make the numbers" will at some point be tempted to [3mmake up [0mthe numbers. + +Suddenly demand goes down and price competition rises. + +How does a change in growth rate change business value? Business value is a function of the amount and timing of future cash flows. If cash flows decreases and/or appears further off in the future, business +value declines. + +233 + +Warren Buffett illustrates how valuations must change when growth expectations are revised: + +A few years ago the conventional wisdom held that a newspaper, television or magazine property would forever increase its earnings at 6% or so annually and would do so without the employment of additional +capital for the reason that depreciation charges would roughly match capital expenditures and working capital requirements would be minor. Therefore, reported earnings (before amortization of intangibles) +were also freely distributable earnings, which meant that ownership of a media property could be construed as akin to owning a perpetual annuity set to grow at 6% a year. Say, next, that a discount rate of +10% was used to determine the present value of that earnings stream. One could then calculate that it was appropriate to pay a whopping $25 million for a property with current after-tax earnings of $1 million +(1/0.1-0.06). + +Now change the assumption and posit that the $1 million represents "normal earning power" and that earnings will bob around this figure cyclically. A "bob-around" pattern is indeed the lot of most businesses, +whose income stream grows only if their owners are willing to commit more capital (usually in the form of retained earnings). Under our revised assumption, $1 million of earnings, discounted by the same 10%, +translates to a + +$10 million valuation. Thus a seemingly modest shift in assumptions reduce the property's valuation to 10 times after-tax earnings. + +Do we pay the same price for a business financed with debt as for a business with no debt? + +Assume Mary is interested in buying a furniture store. The business is stable with no growth, free cash flow of 15 and financed with 75 in equity. A price of 100 (15/0.15) will give her a 15% return. Does +debt make a difference? Yes, the seller could then make extra money by leveraging the business before selling it.If the seller refinances the business with 50 in debt (and the business can borrow at 6% +interest) and withdraws 50 as a dividend, income after interest would be 12 (15-3). If Mary then buys the store for 80 (12/0.15) the seller would have made an extra 30 (50+80- + +100) without any change in the underlying operations of the business. + +Instead Mary should assume she acquires a debt-free business and adjust for 50 of debt and pay 50 (15/0.15-50). She should also correct (add to the price) for excess cash - cash or cash assets that aren't +needed to conduct the business. + +This is the same type of reasoning as when we buy a house. If we for example + +buy a house for $500,000 and put in $200,000 of our own saved money and mortgage the rest or $300,000, the price of the house is still $500,000. + +234 + +"The synergies we expected from the merger never materialized They were mere illusions. " + +Don't forget to quantify consequences when making acquisitions. Take the profit & loss statement and balance sheet of the acquiring company and the target company. Calculate what happens with volume, prices, +cost, and invested capital when the companies combine, considering consequences and behavioral changes of employees, suppliers, customers, and competition. How does business value change? Be realistic. +Studies show that most mergers fail to generate value for the acquiring company's owners. The main reason is that the buyer paid too much for synergies that weren't real. + +"Of one thing, however, be certain," says Warren Buffett, "If a CEO is enthused about a particularly foolish acquisition, both his internal staff and his outside advisors will come up with whatever +projections are needed to justify his stance. Only in fairy tales are emperors told they are naked." + +john reads the paper. A company announced a $10 million contract and its market capitalization jumped $1 billion. + +Does this make sense? If we assume the contract generates a 15% profit margin, + +the implied market value increase is $1.5 million. And even a high-margin project can be a loser if it requires a lot of capital and human resources. + +If present value is the same for different businesses, does the timing of the dividend matter? + +Assume there are 2 different businesses -X and Y -with the following forecasted dividends. After year 5 the two companies close down. + +Year + +1 + +2 + +3 + +4 + +5 + +Dividends from X + +10 + +10 + +10 + +10 + +10 + +Dividends from Y + +0 + +0 + +0 + +0 + +61 + +All cash generated by X is each year distributed to its owners. The free cash flow generated by Y is reinvested and not paid out until after the five year period. Assuming we want a 10% return, the present +value of X's respective Y's dividends are the same or about 38. But this assumes that we can reinvest our dividends from X at 10% so that we have 61 after 5 years. It also assumes that Y can reinvest their +cash flow at rates that cause the dividend to be 61 after 5 years. But in both cases the future may turn out different than expected. The business environment may change and competition increase making the +dividends from X and Y come + +235 + +out differently from what we expect. The more our calculation depends on cash flows far out in the future, the more opportunities there are for unwanted events, and the more uncertain our expected return. + +Do the math! + +We can do a simple exercise to test our possible return from investing in a company and if its market valuation makes sense. Just think about the math implicit. + +Below are some examples where we have ignored dividends and options (in reality we need to properly account for options and make sure that the company's accounting reflects reality and the true operational +performance.) Think of a stock as part of a business and remember that small changes in assumptions can dramatically change value. + +John is thinking of buying 1,000 shares of stock in a public ice cream manufacturer with a market value of $1 billion and no debt or off-balance sheet obligations. How should John reason? + +What is my estimated annual rate of return? + +John projects the future value, and then compares that value with the present market value of $1 billion. What is his implied annual rate of return? Will the price paid give him an adequate return? + +The business has initial cash earnings (earnings+ amortization of goodwill) of + +$40 million and an assumed average annual growth rate in cash earnings of 10% for 10 years. This translates into $104 million in cash earnings in year 10. Assume the market pays an average multiple of 15 for +this type of business. This implies + +$1.56 billion in market value in year 10. If John compares this figure with the present market value, his implied yearly return is 4.5%. John compares this return with the return from other available +investment opportunities. A business may have a great track record, but if the math doesn't work, stay away. + +What scenario achieves a 15% annual rate of return? + +How much must the ice cream manufacturer earn to generate a 15% annual rate of return for John? If the present market value compounds at 15%, what does this imply and is it reasonable? + +A present market value of $1 billion and an annual return of 15% imply $4 billion in market value in year 10. This is what $1 billion will grow to in 10 years if it grows 15% per year. An average multiple of +15 implies $270 million in cash earnings in year 10. This translates into an average annual growth rate in cash earnings of 21% (from a base of $40 million). A profit margin of 15% implies + +236 + +$1.8 billion in sales year 10. He can continue with implied future sales volume, number of users and usage, market share, etc. + +John then asks: What causes this future value? What does this imply in numbers today? Is it reasonable regarding evidence of track record in growth, earnings, profit margins, market size/volume growth, market +share, competitive advantage, etc? Which factor has the greatest impact on future cash earnings and thereby value? What forces can change this scenario? How can the company lose its advantages? + +If the company doesn't make money today, what future free cash flow is implied by their market value if I want a 10% return? + +In the midst of the Internet mania, Warren Buffett said: + +When we buy a stock, we always think in terms of buying the whole enterprise because it enables us to think as businessmen rather than stock speculators. So let's just take a company that has marvelous +prospects, that paying you nothing now where you buy it at a valuation of$500 billion... For example, let's assume that there's only going to be a one year delay before the business starts paying out to you +and you want to get a 10% return. If you paid $500 billion, then $55 billion in cash is the amount that it's going to have to + +be able to disgorge to you year after year after year. To do that, it has to make perhaps $80 billion, or close to it, pretax. Look around at the universe of businesses in this world and see how many are +earning $80 billion pretax - or $70 billion or $60 or $50 or $40 or even + +$30 billion. You won't find any. + +Whether a business sells nails or telecom equipment, if more money is going out than coming in, on a present value basis, it is worthless. As Warren Buffett says, "Value is destroyed, not created, by any +business that loses money over its lifetime, no matter how high its interim valuation may get." + +He continues: + +There's plenty of magic in short term in rising P/E multiples and the games people play with accounting and so on. But in the end, you can't get more out of a business between now and its extinction than the +business makes. And actually you'll make something less depending on who your business managers are, how often there's turnover in the security and how much you pay the investment manager and so on. + +237 + +- NINE - + +EVIDENCE + +It is undesirable to believe a proposition when there is no ground whatsoever for supposing it true. + +- Bertrand Russell + +Evidence helps us prove what is likely to happen or likely to be true or false. Evidence comes from facts, observations, experiences, comparisons, and experiments. + +The methods of science + +There are in fact two things: science and opinion; the former begets knowledge, the latter ignorance. + +- Hippocrates + +"What experiment can I do to figure this out?" + +In 1986, the space shuttle Challenger exploded on launch, killing all astronauts aboard. After the disaster, NASA put together a commission where Richard Feynman showed that the fuel booster rockets were not +safe when the temperature was cold. The temperature at takeoff was 32 F. During a launch, vibrations cause the rocket joints to move. Inside the rocket joints there were rubber O-rings that are used in a +certain key stage in the space shuttle's fuel delivery system. + +Richard Feynman did a simple experiment with a rubber O-ring from the Challenger rocket. He squeezed the rings in a C-clamp and dipped them in a glass of ice water (32 F) and showed that the rubber didn't +expand. Since there was no resilience in the rubber at 32 F, the O-ring could not fill the gap in the expanding rocket booster joints. It consequently caused an explosion of the booster and the space shuttle. + +This also illustrates that an experiment doesn't have to be complicated. + +Do what scientists do: Strive for objectivity. Scientists try to describe the world as it is, not as they want it to be. They seek to answer "why" and "how" questions and try to predict natural phenomena and +processes by using methods of scientific integrity. Adam Smith said in An Inquiry into the Nature and Causes of + +238 + +the Wealth of Nations: "Science is the great antidote to the poison of enthusiasm and superstition." + +The scientific process involves the following steps (of course, trial and error, luck and intuition also matters - scientists use any methods that help them solve a problem): + +Problem or observation - We try to figure something out. We have a problem or we observe some phenomena and wonder what happens and why (what matters is what actually happens). + +Guess [1mwhy- [0mWe try to find a possible solution or an explanation (a hypothesis of why or how something happens) that can be proved or disproved by testing it against experiment and observation. Maybe some rule +or model can solve the problem or explain our observation. Our guess must be measurable and agree with nature and proven evidence. + +Predict consequences - We work out all logical consequences of our guess and see what would be implied if our guess was right. + +Test - "If I do this, what will happen?" Testability is key. We compare the implied consequences of our guess with experiment, evidence and observation. We repeat the experiment against error, fraud, +coincidence, and change in circumstances or environment. We report our results honestly. The more evidence that agrees with our guess, the more likely the guess was right. If the guess disagrees with +experiment or evidence, it is wrong. As Richard Feynman says: + +It does not make any difference how beautiful your guess is. It does not make any difference how smart you are, who made the guess, or what his name is - if it disagrees with experiment it is wrong. + +Darwin realized that for an observation to be of any use, it must be tested for or against a theory, hypothesis or model (if we don't "guess why", there can be no experiments since a test has nothing to guide +it). On board the HMS Beagle, in a letter to his friend Henry Fawcett, Darwin wrote: + +About thirty years ago there was much talk that geologists ought only to observe and not to theorize; and I well remember someone saying that at this rate a man might as well go into agravel pit and count the +pebbles and describe the colours. How odd it is that anyone should not see that all observation must be for or against some view if it is to be of any service! + +We don't merely observe some behavior; we observe with some purpose in mind or in light of some theory or with some background about what is important to + +239 + +look for. It is the same when we search for information. Charles Munger says: + +... you have to have some idea of why you're looking for the information. Don't read annual reports the way Francis Bacon said you do science ... where you just collect endless [amounts of] data and then only +later do you try to make sense ofit. You have to start with some ideas of reality. And then you have to look to see whether what you're seeing fits in with that basic thought structure. + +Occam's Razor is a principle attributed to the 14th Century logician William of Occam: "Entities should not be multiplied unnecessarily." If we face two possible explanations which make the same predictions, +the one based on the least number of unproven assumptions is preferable, until more evidence comes along. Occam doesn't rule out other explanations. To paraphrase Albert Einstein: "Theories should be as +simple as possible, but no simpler." + +Finding evidence from the past + +Study the past if you would divine the future. + +- Confucius + +john is thinking of hiring a new manager. Does the managers past record matter? + +Warren Buffett says: + +The best judgment we can make about managerial competence does not depend on what people say, but simply what the record shows. At Berkshire Hathaway, when we buy a business we usually keep whoever has been +running it, so we already have a batting average. Take the case of Mrs. B. who ran our Furniture Mart. Over a SO-year period, we'd seen her take $500 and turn it into a business that made $18 million pretax. +So we knew she was competent ... Clearly, the lesson here is that the past record is the best single guide. + +Then you run into the problem of the 14-year-old horse. Let's say you buy The Daily Racing Form and it shows that the horse won the Kentucky Derby as a four-year-old. Based on past performance, you know this +was one hell of a horse. But now he's 14 and can barely move. So you have to ask yourself, "Is there anything about the past record that makes it a poor guideline as a forecaster of the future?" + +The following questions help us decide if past evidence is representative for the future: + +Observation: Will past/present behavior continue? How long can it continue? + +240 + +Explanation: Why did it happen in the past or why does it happen now? How did it happen? We must understand the reasons why a past outcome occurred. What are the key factors? This demands that we understand +the equation - the key variables involved and their relationships. Start with a hypothesis. Compare the implied consequences of our explanation of causes with appropriate evidence + +- for and against. + +Predictability: How predictive (representative) is the past/present evidence for what is likely to happen in the future? Are the conditions now and in the future likely to change? Make sure that the evidence +isn't random. What worked in the past could have been the result of chance. + +[1mContinuation and Change: [0mWhat is required to make the past/ present record continue or to achieve the goal (look at the equation again)? What must happen? What must not happen? What forces can change it or +cause what we don't want? Likely? Antidotes to what we don't want to happen? + +Certainty and Consequences: How certain am I? What single event am I betting on that must happen or not happen? What are the consequences of being wrong? + +Falsify and disprove + +All our commonsense ideas should always be open to criticism. + +- Karl Popper (Austrian-British philosopher, 1902-1994) + +Scientific results always have some probability attached to them. Tomorrow may bring new evidence. Instead of verifying a statement, it is sometimes better to prove it false. A single piece of evidence in +favor of a statement does not prove its truth - it only supports it. But a single piece of evidence against it will show that it is false. Albert Einstein said: "No number of experiments can prove me right; a +single experiment can prove me wrong." + +"All swans are white. " + +How could we test this statement? We could open our eyes, and go out looking for non-white swans. If we find one swan that is not white we have disproved the statement. The more swans we find to be white, the +more support the statement has. But it is not proven. One black swan and the statement is rejected. + +"The universe is no more than 10,000 years old." + +What experiment can we perform to falsify this statement? We can look up at the sky and observe stars that are millions of light-years away. This means we are seeing them as they were millions of years ago. + +241 + +"The medical treatment worked. Tm cured. " "Compared to what?" + +How can we test whether a cure is due to treatment, good salesmanship, the power of suggestion, or the patient's imagination? To reduce error and bias, medical research uses a randomized, double blind +placebo-controlled study. Research subjects are randomly divided in two groups that match each other in age, physical status and other factors. One group receives the treatment and the other group the +placebo. Neither the research subjects nor the researchers know who's getting the treatment or the placebo. Then the researchers compare the effects. + +"There is no risk in using this medicine. " + +That there is no evidence of harm (or benefit) isn't the same as evidence that something is safe (or harmful). Only safe (or harmful) based on what we know so far. Compare archaeology - just because something +hasn't been found doesn't mean it won't be found. + +Disprove ideas. Charles Darwin always looked at the possibility that he was wrong: + +I had, also, during many years, followed a golden rule, namely, that whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it +without fail and at once: for I had found by experience that such facts and thoughts were far more apt to escape from the memory than favourable ones. Owing to this habit, very few objections were raised +against my views which I had not at least noticed and attempted to answer ... + +I think that I have become a little more skillful in guessing right explanations and in devising experimental tests; but this may probably be the result of mere practice, and of a larger store of knowledge. I +have as much difficulty as ever in expressing myself clearly and concisely; and this difficulty has caused me a very great loss of time; but it has had the compensating advantage of forcing me to think long +and intently about every sentence, and thus I have been led to see errors in reasoning and in my own observations or those of others. + +"Since a lot of evidence agrees with my explanation, I must be right. " + +Not necessarily, the same evidence may agree with other explanations. Look for evidence that disproves your explanation. + +Don't spend time on already disproved ideas or arguments or those that can't be disproved. Ask: What test can disprove this? For example, someone tells us that there is life on planet Zeta. This can't be +tested. That doesn't mean there is + +242 + +no life on the planet. It only means that there is no way we can test it today. + +Theories based on observations have priority over theories alone since observations can disprove theories. Galileo Galilei based his theories on observations in the debate whether the sun revolved around the +Earth. + +Engage in self-criticism. Question your assumptions. Explain the opposite of your beliefs. Ask: Assume I'm wrong, how will I know? Why may an opposite theory be correct? Assuming my answer is correct, what +would cause me to change my mind? Then, look for that evidence. + +Often we don't see our weaknesses and thus are not motivated to improve. Therefore, encourage the right people to give objective feedback that will help us improve. + +Look back and measure how you are doing against your original expectations. + +Find your mistakes early and correct them quickly before they cause harm. + +The next tool forces us to be objective. Charles Munger says on backward thinking: + +The mental habit of thinking backward [3mforces [0mobjectivity - because one of the ways you think a thing through backward is you take your initial assumption and say, "Let's try and [3mdisprove [0mit." + +That is [3mnot [0mwhat most people do with their initial assumption. They try and [3mconfirm [0mit. It's an automatic tendency in psychology- often called "first-conclusion bias". But it's only a tendency. You can train +yourself away from the tendency to a substantial degree. You just constantly take your own assumptions and try and disprove them. + +243 + +- TEN - + +BACKWARD THINKING + +Alot of success in life and success in business comes from knowing what you really want to avoid - like early death and a bad marriage. + +Charles Munger + +Avoid what causes the opposite of what you want to achieve. + +"You must always invert," said the 19th Century German mathematician Karl Jacobi when asked the secret of his mathematical discoveries. Whenever we try to achieve a goal, solve problems, predict what is +likely to happen or likely to be true or false, we should think things through backwards. + +At the weekly meeting with his managers, John asked· "What actions could our company take to destroy as much value as possible in as short time as possible?" "Treat the employees badly. Reward bad work. Don't +appeal to the employee's self interests but to a goal no one understands. Don't inform people what the company stands for, what rules apply, and the consequences for breaking them. Make sure people don't know +their areas of responsibility. Put the right person in the wrong place. Don't let people know if they achieve a goal. Everything should be impossible to measure. Never tell people why something should be +done. + +Surround the CEO with confused, unmotivated subordinates. Give key customers reasons to be angry. Late and wrong deliveries, delays, and arrogance will help. Let the customers associate the business with +misery and make sure that this feeling gets reinforced at every contact with the company." + +Thinking backwards, we can determine what actions must be avoided. As Charles Munger says, "If you were hired by the World Bank to help India, it would be very helpful to determine the three best ways to +increase man-years of misery in India - and, then, turn around and avoid those ways." + +Instead of asking how we can achieve a goal, we ask the opposite question: What don't I want to achieve (non-goal)? What causes the non-goal? How can I avoid that? What do I now want to achieve? How can I do +that? For example, instead of searching for how John and Mary can improve their marriage, they ask: "What qualities will destroy our marriage?" One quality is dishonesty. Now they + +244 + +reinvert the question back and ask: "How can we improve our marriage?" Be honest. (See also Charles Munger's brilliant speech on prescriptions for guaranteed misery in Appendix One). + +Charles Munger provides an enlightening example on how dumb systems cause dumb behavior: + +Let's say you have a desire to do public service. As a natural part of your planning, you think in reverse and ask, "What can I do to ruin our civilization?" That's easy. If what you want to do is to ruin +your civilization, just go to the legislature and pass laws that create systems wherein people can easily cheat. It will work perfectly. Take the workers' compensation system in California. Stress is real And +its misery can be real. So you want + +to compensate people for their stress in the workplace. It seems like a noble thing to do. But the trouble with such a compensation practice is that it's practically impossible to delete huge cheating. And +once you reward cheating, you get crooked lawyers, crooked doctors, crooked unions, etc. participating in referral schemes. You get a total miasma of disastrous behavior. And the behavior makes all the people +doing it worse as they do it. So you were trying to help your civilization. But what you did was create enormous damage, net. So it's much better to let some things go uncompensated - to let life be hard - +than + +to create systems that are easy to cheat. + +"Don't think about the color red!" + +If someone told you not to think of the color red, you might automatically think of that color. Why? Because in order to know what not to think about, your brain must first think about it. When John is on a +golf course trying to hit over a water hazard in front of the green, he doesn't say to himself, "I don't want to hit the ball in the water," but instead "I want to hit the ball on the green." So when we tell +people what to avoid, we should end with what we want them to achieve. + +Study errors. + +Marcus Porcius Cato wrote: "Wise men profit more from fools than fools from wise men; for the wise men shun the mistakes of the fools, but fools do not imitate the successes of the wise." + +To reduce mistakes, we should study failures with severe consequences. Both in business and in life. We should look at their causes over time and see if they are unchanged. + +Often we learn more from understanding why something doesn't work than from why it does. Studies also show that dramatic error-story training is an + +245 + +effective method of learning. Errors are salient and memorable. Studying errors encourage effortful thinking, and improves our capacity to deal with change and new or unusual situations. Ask: Why did that +happen? Why do certain businesses lose money or fail? Why do smart people engage in foolish behavior? Why do certain accidents happen? What was the mistake that caused bad performance? What circumstances were +present? What's the lesson? + +When we know this, we should ask: What people or businesses are doing things that history has proven causes failure? How can we best avoid what we don't want to happen? How can we create the best conditions +to avoid mistakes? How can we prevent causes that can't be eliminated? How can we limit the consequences of what we want to avoid? How can we limit the probability of what we want to avoid? + +We can organize the study of errors, by using a table like the one below. + +What to avoid + +What were the mistakes? + +Cause Antidote + +Why did those happen? What are the major risk factors? + +How do specific errors evolve? What factors contribute? + +Stupidity/Irrationality + +Big idea that helps explain and predict? + +What is rational? How can I create the best conditions to make good decisions? What can be eliminated or prevented? + +Turn the negative into an advantage. + +In 1796, British physician Edward Jenner discovered vaccination. He noticed that milkmaids who had contracted a mild and usually non-lethal form of the pox virus - cowpox - seemed to be immune to the lethal +form of the virus, smallpox. He then took samples of a milkmaid's lesions and inoculated a young boy with cowpox. The boy built up antibodies in his immune system that prevented him from getting smallpox and +subsequently survived the epidemic. + +Begin with the end in mind + +In the 4th Century the Greek mathematician Pappus of Alexandria wrote: "Let us start with what is being seeked and assume that we already found it." Assume we've achieved our goal, then ask: What was the +purpose? Was this what I wanted? If so, from which earlier position do I get there? What is needed to achieve this? Then work backward to the beginning. By working backwards we can easier see + +246 + +how and if something may work. An example of this is retrospective disease studies. Researchers study the disease then work backward to see what prior conditions are associated with it. + +"We need discipline in schools. " + +What would be the consequences if this statement were false? Turn a statement backwards and show that the opposite is worse. What are the consequences? Unbelievable or negative? Suppose there was no +discipline in schools, would there be more behavior we don't want? + +When we believe we have arrived at the right judgment, we should consider what could cause the opposite of our prediction -what we don't want to happen. Suppose we make a personality judgment and conclude +that the individual is of good character and we want to enter a relationship. Ask: What can ruin this relationship? What causes me to misjudge character? + +Other uses of backward thinking are: Study evidence that implies the opposite of what is normal and ask "why." Use "negative" rules - tell people what they can't do. Practice zero base thinking - start with a +clean sheet of paper and ask: If we weren't already doing what we do, how can we best achieve our goal? + +Next chapter is about risk or the possibility of loss. If we put our head in the lion's mouth, we shouldn't be surprised if it's bitten off. + +247 + +- ELEVEN - + +RISK + +Alife without adventure is likely to be unsatisfying, but a life in which adventure is allowed to take whatever form it will is sure to be short. + +Bertrand Russell (from Authority and the Individual) + +"Why do you want to buy this stock?What must happen for the investment to succeed? What is the downside?" + +Reflect on what can go wrong. Ask: What may cause this to turn into a catastrophe? What is the potential downside? What should I worry about? What is the likelihood and magnitude of a possible loss? What's +the worst thing chat could happen? What can I do to prevent it? What will I do if it happens? + +We need to look at the downside when we invest. According to Forbes + +Magazine, Charles Munger's way of reasoning is: + +The simple fact is that you can't tell whether an idea is likely to work unless you consider all the possible negatives... Okay, it's a good company. But is the price low enough? Is the management made up of +people Munger and Buffett are comfortable with? If it is cheap enough to buy, is it cheap for the wrong reason or the right reason? As Munger puts it: "What's the flip side, what can go wrong that I haven't +seen?" + +Being wrong causes both an actual loss and an opportunity cost. When investing, we can either lose our capital - we invest 10 and get back 5 - or we get an inadequate return - for example 3% versus 6% from a +bond. What does Warren Buffett say about business risk? + +When we look at businesses, we try to look at businesses that are good businesses today and think about what can go wrong. We think of business risk in terms of what can happen five, 10 or 15 years from now +that will destroy, modify or reduce the economic strengths we believe currently exist in the business. And for some businesses, that's impossible to figure - at least it's impossible for us to figure - and we +don't even think about it. If we can think of very much that can go wrong, we just forget it. + +248 + +Warren Buffett says that "the best way to minimize risk is to think". He also tells us how Berkshire reduces risk: + +In stocks, we expect every commitment to work out well because we concentrate on conservatively financed businesses with strong competitive strengths, run by able and honest people. If we buy into these +companies at sensible prices, losses should be rare. Indeed, during the 38 years we have run the company's affairs, gains from the equities we manage at Berkshire (that is, excluding those managed at General +Re and GEICO) have exceeded losses by a ratio of about 100 to one. + +Do we need to take a lot of risks to get ahead in life? Charles Munger tells a story: + +I had a relative by marriage who died in his late 80s. And I don't think he ever had a loss. He only did about eight things in his lifetime. He started with a small poke, and if something wasn't a near cinch, +he didn't do it. He lived well and died rich. I think it's possible for a great many people to live a life like that where there isn't much risk of disaster and where they're virtually sure to get ahead a +reasonable amount. It takes a lot of judgment, a lot of discipline and an absence of hyperactivity. By this method, I think most intelligent people can take a lot of risk out oflife. + +A fool and his money are soon parted + +What traits are necessary to be an outstanding long-term investor? Warren Buffett gives us some clues in Berkshire Hathaway's 2006 Chairman's letter, where he mentions Berkshire's intention of hiring someone +to succeed him as Berkshire's chief investment officer when the need arises: + +Picking the right person(s) will not be an easy task. It's not hard, of course, to find smart people, among them individuals who have impressive investment records. But there is far more to successful +long-term investing than brains and performance that has recently been good. + +Over time, markets will do extraordinarily, even bizarre things. A single, big mistake + +could wipe out a long string of successes. We therefore need someone genetically programmed to recognize and avoid serious risks, including those never before encountered. Certain perils that lurk in +investment strategies cannot be spotted by use of the models commonly employed today by financial institutions. + +Temperament is also important. Independent thinking, emotional stability, and a keen understanding of both human and institutional behavior is vital to long-term investment success. + +249 + +The consequences of being wrong + +If we can't tolerate a possible consequence, remote though it may be, we steer clear of planting its seeds. + +- Warren Buffett + +Experience tells me that the foture will be similar to the past. + +It may or may not. We don't know the future. What if the consequences of being wrong are terrible and can cause us great harm? If the decision is important, we should largely ignore what has happened in the +past and focus on the consequences of being wrong. + +Why do we insure our houses? We do it because the consequences of being wrong + +- a fire - is devastating, and the cost of insurance is relatively minor in comparison. For example, the cost of a $1.000 premium decreases my happiness very little, while the potential loss of $300,000 would +lead to considerable misery. Ask: What could go wrong? What can I do to prevent harm or to deal with it if it happens? + +john wants to buy another ice cream store. + +The key variable he's betting on is that "Unit volume will increase." What are the consequences ifhe is wrong? + +The worse the consequence of being wrong, the less inclined we must be to + +take a specific action or the more evidence we need in favor of something. + +Ask: What is the cost of being wrong versus the benefit of being right compared to other investment opportunities? Cost: John may lose money, reputation, and experience mental stress. It will also take his +focus away from other business. Benefit: Possibility to make more money over a period of time. Alternative: More time to concentrate on the present business or other opportunities. + +Or stated another way: Ifl do this because I bet that unit volume will increase but I'm wrong (volume remains the same or decreases due to less demand and more competition or unfavorable environment) what are +the consequences? Can I handle them? Are they reversible? IfI don't do this because I bet that unit volume will go down or stay the same, but I'm wrong, what are the consequences? In which alternative do I +lose less? + +Margin of safety + +We try to arrange [our affairs] so that no matter what happens, we'll never have to 'go back to go. " + +Charles Munger + +250 + +Albert Einstein said: "Whoever undertakes to set himself up as a judge of truth and knowledge is shipwrecked by the laughter of the gods." We can't predict what is going to happen in life. Never underestimate +the chance of rare events. + +To protect us from all the unknowns that lie ahead we can either avoid certain situations, make decisions that work out for a wide range of outcomes, have backups or a huge margin of safety. For example, when +investing money the following can guide us: know the underlying business value, don't use leverage, enter situations where the management is able and honest, and invest with a huge margin of safety. + +How much margin of safety do we need? Warren Buffett answers: + +If you understand a business - if you can see its future perfectly- then, obviously, you need very little in the way of margin of safety. Conversely, the more things that can happen, the more uncertainty +there is, the more vulnerable the business is or the greater the possibility of change, the larger margin of safety you require... + +If you're driving a 9,800 pound truck across a bridge that says it holds 10,000 pounds and the bridge is only about six inches above the ground, then you may feel OK. However, if the bridge is over the Grand +Canyon, then you may want a little larger margin of safety. And, therefore, you may only drive a 4,000 pound truck across. So it depends on the nature of the underlying risk. + +What else is important? We have a better chance of avoiding misjudgment and improving our lives if we have the right attitude and follow certain values. + +In writer Janet Lowe's wonderful biography of Charles Munger, [3mDamn Right!, [0mwe can learn some of Charles Munger's views on values and behavior from his stepson, Hal Borthwick: + +Charlie drummed in the notion that a person should always "Do the best that you can do. Never tell a lie. If you say you're going to do it, get it done. Nobody gives a shit about an excuse. Leave for the +meeting early. Don't be late, but if you are late, don't bother giving people excuses. Just apologize... Return your calls quickly. The other thing is the five second no. You've got to make your mind up. You +don't leave people hanging." + +251 + +- TWELVE - + +ATTITUDES + +Be happy while you're living, for you are a long time dead. + +Scottish proverb + +Life is long if we know how to use it + +The Roman philosopher Lucius Annaeus Seneca tells us in his Moral Essays that it's not that we have so little time but that we waste much of it: + +Why do we complain of Nature? She has shown herself kindly; life, if you know how to use it, is long. But one man is possessed by an avarice that is insatiable, another by a toilsome devotion to tasks that +are useless; one man is besotted with wine, another is paralyzed by sloth; one man is exhausted by an ambition that always hangs upon the decision of others, another, driven on by the greed of the trader, is +led over all lands and all seas by the hope of gain... many are kept busy either in the pursuit of other men's fortune or in complaining of their own; many, following no fixed aim, shifting and inconstant and +dissatisfied, are plunged by their fickleness into plans that are ever new; some have no fixed principle bywhich to direct their course, but Fate takes them unawares while they loll and yawn - so surely does +it happen that I cannot doubt the truth of that utterance which the greatest of poets delivered with all the seeming of an oracle: "The part of life we really live is small." For all the rest of existence is +not life, but merely time. + +He continues: "You live as if you were destined to live forever, no thought of your frailty ever enters your head, of how much time has already gone by you take no heed.": + +You squander time as if you drew from a full and abundant supply, though all the while that day which you bestow on some person or thing is perhaps your last. You have all the fears of mortals and all the +desires of immortals. You will hear many men saying: "After my fiftieth year I shall retire into leisure, my sixtieth year shall release me from public duties." And what guarantee, pray, have you that your +life will last longer? Who will suffer your course to be just as you plan it? Are you not ashamed to reserve for yourself only the remnant of life, and to set apart for wisdom only that time which cannot be +devoted to + +252 + +any business? How late it is to begin to live just when we must cease to live! What foolish forgetfulness of mortality to postpone wholesome plans to the fiftieth and sixtieth year, and to intend to begin +life at a point to which few have attained! + +Life is too short to waste. Samuel Johnson said: "It matters not how a man dies, but how he lives. The act of dying is not of importance, it lasts so short a time." We only have one life so we should try to +create a life we enjoy. Comedian George Burns said: "You can either do what you love or love what you do. I don't + +see there's any other choice." + +We all have 24 hours in the day. We can't save time, only spend it wisely or foolishly. How do we use our time? What is the best use? What do we want out of life? Do we live in a way to make that possible? +The shorter the list, the more likely it is to focus on things that matter. Know what we want and don't want. Do we do what we want to do or what others expect us to do? Who or what is most important in our +life? Do we have a sense of meaning? + +Part of avoiding misjudgments and improving our lives is having the right attitude toward life. Since people are different, there is no one-size-fits-all strategy. We each must figure out our own style. But +there are guidelines that apply to us all. + +We should act in a way that agrees with our nature, advantages and limitations and we should establish (and follow) some values. + +How can we expect to succeed in a field we don't understand? We reduce the likelihood of making mistakes if we deal with things that agree with our nature, and things we understand and do well. We have a +better chance solving problems and evaluating statements if they are within our area of competence. Confucius said: "To know that we know what we know, and that we do not know, what we do not know; that is +true knowledge." We must determine our abilities and limitations. We need to know what we don't know or are not capable of knowing and avoid those areas. As Warren Buffett says: + +You have to stick within what I call your circle of competence. You have to know what you understand and what you don't understand. It's not terribly important how big the circle is. But it's terribly +important that you know where the perimeter is. + +Charles Munger adds: + +We'd rather deal with what we understand. Why should we want to play a competitive game in a field where we have no advantage - maybe a disadvantage - instead of playing in a field where we have a clear +advantage? + +253 + +Each of you will have to figure out where your talents lie. And you'll have to use your advantages. But if you try to succeed in what you're worst at, you're going to have a very louse career. I can almost +guarantee it. To do otherwise, you'd have to buy a winning lottery ticket or get very lucky somewhere else. + +Ask: What is my nature? What motivates me? What is my tolerance for pain and risk? What has given me happiness and unhappiness in the past? What things and people am I comfortable with? What are my talents +and skills? Do I know the difference between what I want and what I'm good at? Where do I have an edge over others? What are my limitations? + +How can we do what is important if we don't have any values? If we don't stand for something, we fall for anything. + +Be honest + +Honesty is the first chapter of the book of wisdom. + +- Thomas Jefferson (American President 1743-1826) + +Act honorably. Listen to the words of Mark Twain: "Always do right. This will gratify some people and astonish the rest." + +Tell the truth. Follow Lou Vincenti's rule (former Chairman ofWesco): "If you tell the truth you don't have to remember your lies." + +Honesty pays. Charles Munger says: "More often we've made extra money out of morality. Ben Franklin was right for us. He didn't say honesty was the best morals, he said that it was the best policy." + +Act with integrity and individuality. Heraclitus said: "The content of your character is your choice. Day by day, what you choose, what you think, and what you do is who you become. Your integrity is your +destiny.. .it is the light that guides your way." + +Every human being is unique so we have the right to be different. Why is integrity the real freedom? Because if we have nothing to hide we have nothing to fear. + +Charles Munger says: + +We think there should be a huge area between ... what you are willing to do and what you can do without a significant risk of suffering criminal penalty or causing losses. We believe you shouldn't go anywhere +near that line. You ought to have an internal compass. So there should be all kinds of things you won't do even though they're perfectly legal. That's the way we try to operate. + +254 + +Stay out of anything questionable and deal with honorable people. Use the Warren Buffett "front-page test:" "Would I be willing to see my action immediately described by an informed and critical reporter on +the front page of my local paper, there to be read by my spouse, children and friends?" + +Trusting people is efficient. Charles Munger says: "Good character is very efficient. If you can trust people, your systems can be way simpler. There's enormous efficiency in good character and dis-efficiency +in bad character." + +Act as an exemplar + +Wealth is a blessing to those who know how to use it, a curse to those who don't. + +- Publius Terentius + +Observe what signals you send out. Charles Munger tells us that some people have a duty to create the right appearance: ''A person who rises high in the Army or becomes a Supreme Court justice is expected to +be an exemplar, so why shouldn't someone who rises high in a big corporation act as an exemplar?" + +He continues: + +You don't want your first grade teacher to be fornicating on the floor or drinking booze in the classroom. Similarly, I don't think you want your stock exchange to be all over the headlines because of its +wretched excess. And I certainly don't think that you want to turn the country's major stock exchange into even more of a casino than it is already. + +The military has the right model. Munger continues: + +One of the things that's been horribly underdone is the concept where the military equivalent is conduct unbecoming an officer. When you rise to a certain point in a civilization, you ought to have a duty to +behave as an exemplar. When is the last time you heard in a boardroom, 'Is this consistent with our duties as exemplars?' I mean the very word has an antique ring to it 'exemplar'. But that's exactly what is +horribly lacking. + +And everybody can see that that's what's required. The military concept of conduct unbecoming an officer is an important one. Your duty is to not cause resentment and envy and a lot of other things. You have +a big duty as an exemplar." + +How can we teach ethics? Charles Munger says: + +I think the best single way to teach ethics is by example. And that means if you take in people who demonstrate in all their daily conduct an appropriate ethical framework, I think that has + +255 + +enormous influence on the people who watch it. Conversely, if your ethics slip, and if people are being rewarded for ethical slips, then I think your ethics cascade downward at a very, very rapid rate. + +I think ethics are terribly important, but I think they're best taught indirectly by example. If + +you just sort oflearn a few rules and remember 'em well enough to pass a test, my guess is it doesn't do all that much for people's ethics. But if you see people you admire behaving a certain way- +particularly under stress - I think you're likely to remember and be affected by that for a long, long time. + +Treat people fairly + +Warren Buffett says that: "The only way to be loved is to be lovable. You always get back more than you give away. If you don't give any you won't get any." Lao Tsu said: "Respond intelligently even to +unintelligent treatment." Be nice to people and if they are not nice to you - don't be nasty - just avoid them in the future. Follow the advice of Charles Darwin - avoid controversies: + +I rejoice that I have avoided controversies, and this I owe to Lyell, who many years ago, in reference to my geological works, strongly advised me never to get entangled in a controversy, as it rarely did any +good and caused a miserable loss of time and temper. .. + +All that I think is that you [letter to E. Haeckel) will excite anger, and that anger so completely blinds every one that your arguments would have no chance of influencing those who are already opposed to +our views. + +Don't take life too seriously + +Life is too important to be taken seriously. + +- Oscar Wilde + +Have perspective. Remember Samuel Johnson's words: "Distance has the same effect on the mind as on the eye." When we fail we should view it as a learning expenence. + +Have a positive attitude. Mayo Clinic researchers report that optimists report a higher level of physical and mental functioning than pessimists. Studies at the Mayo Clinic also show that optimists live +longer than pessimists. Having a positive attitude also causes the body to produce pain-suppressing hormones, called endorphins, which work like morphine. + +Warren Buffett says on the value of enthusiasm: + +256 + +I do think enthusiasm is a good quality to have generally. It has helped me... I like managers in our businesses that are enthusiastic. These people are enthusiastic about their work in the same way people +can get enthusiastic about golf, and that translates into results. If you are in a job that you are not enthusiastic about, find something else. You're not doing yourself any favor, and you're not doing your +employer any favor and you're going to make a change anyway at some point. We're here on earth only one time, unless Shirley MacLaine is right, so you ought to be doing something that you enjoy as you go +along, and can be enthusiastic about. + +He also says that we should do what we enjoy: "Do what turns you on. Do something that if you had all the money in the world, you'd still be doing it. You've got to have a reason to jump out of bed in the +morning... Don't look for the money. Look for something you love, and if you're good, the money will come." + +Have reasonable expectations + +Blessed is he that expects nothing, for he shall never be disappointed. + +- Benjamin Franklin + +If we don't hope for much, reality often beats our expectations. If we always expect the best or have unreal expectations, we are often disappointed. We feel worse and make bad judgments. + +Expect adversity. We encounter adversity in whatever we choose to do in life. Charles Munger gives his iron prescription for life: + +Whenever you think that some situation or some person is ruining your life, it is actually you who are ruining your life... Feeling like a victim is a perfectly disastrous way to go through life. If you just +take the attitude that however bad it is in any way, it's always your fault and you just fix it as best you can - the so-called "iron prescription" - I think that really works. + +When bad things happen, ask: What else does this mean? See life's obstacles as temporary setbacks, not disasters. Mark Twain says: "[Our] race, in its poverty, has unquestionably one really effective weapon - +laughter... Against the assault oflaughter nothing can stand." + +257 + +Live in the present + +The superior man does not waste himself on what is distant, on what is absent. He stands in the here and now, in the real situation. + +- Confucius + +Often we tend to emphasize the destination so much that we miss the journey. Stay in the present and enjoy life today. Blaise Pascal wrote: + +Let each of us examine his thoughts; he will find them wholly concerned with the past or the future. We almost never think of the present, and if we do think of it, it is only to see what light it throws on +our plans for the future. The present is never our end. The past and the present are our means, the future alone our end. Thus we never actually live, but hope to live, and since we are always planning how to +be happy, it is inevitable that we should never be so. + +Be curious and open-minded. Always ask "why'' + +Curiosity is one of the permanent and certain characteristics of a vigorous mind. + +Samuel Johnson + +Thomas Henry Huxley said: "Sit down before facts like a child, and be prepared to give up every preconceived Notion, follow humbly wherever and to whatever abysses Nature leads, or you shall learn nothing." A +child is curious and asks "why?" As grown-ups we seem to forget the "whys" and accept what others say. We should all be children again and see the world as if through the eyes of a curious child without +preconceptions. + +The End + +I confess that I have been as blind as a mole, but it is better to learn wisdom late than never to learn it at all. + +Sherlock Holmes (Arthur Conan Doyle, The Man with the Twisted Lip) + +I hope this book is helpful in both understanding and improving your thinking. I also hope that you will continue in your search for wisdom. We are still going to make misjudgments (at least I still do them), +but we can improve. + +258 + +- APPENDIX ONE - + +CHARLES T. MUNGER HARVARD SCHOOL COMMENCEMENT SPEECH + +[1mjUNE 13, 1986 [0m + +Prescriptions for Guaranteed Misery in Life + +Now that Headmaster Berrisford has selected one of the oldest and longest-serving trustees to make a commencement speech, it behooves the speaker to address two questions in every mind: + +Why was such a selection made? and, + +How long is the speech going to last? + +I will answer the first question from long experience alongside Berrisford. He is seeking enhanced reputation for our school in the manner of the man who proudly displays his horse which can count to seven. +The man knows that counting to seven is not much of a mathematical feat but he expects approval because doing so is creditable, considering that the performer is a horse. + +The second question, regarding length of speech, I am not going to answer in advance. It + +would deprive your upturned faces oflively curiosity and obvious keen anticipation, which I prefer to retain, regardless of source. + +But I will tell you how my consideration of speech length created the subject matter of the speech itself. I was puffed up when invited to speak. While not having significant public speaking experience, I do +hold a black belt in chutzpah, and, I immediately considered Demosthenes and Cicero as role models and anticipated trying to earn a compliment like Cicero gave when asked which was his favorite among the +orations of Demosthenes. Cicero replied: "The longest one." + +However, fortunately for this audience, I also thought of Samuel Johnson's famous comment when he addressed Milton's poem, Paradise Lost, and correctly said: "No one ever wished it longer." And that made me +consider which of all the twenty Harvard School graduation speeches I had heard that I wished longer. There was only one such speech, that given byJohnny Carson, specifying Carson's prescriptions for +guaranteed misery in life. I therefore decided to repeat Carson's speech but in expanded form with some added prescriptions of my own. + +After all, I am much older than Carson was when he spoke and have failed and been miserable more often and in more ways than was possible for a charming humorist speaking at younger age. I am plainly +well-qualified to expand on Carson's theme. + +What Carson said was that he couldn't tell the graduating class how to be happy, but he could tell them from personal experience how to guarantee misery. Carson's prescriptions for sure misery included: + +260 + +Ingesting chemicals in an effort to alter mood or perception; + +Envy; and + +Resentment. + +I can still recall Carson's absolute conviction as he told how he had tried these things on occasion after occasion and had become miserable every time. + +It is easy to understand Carson's first prescription for misery - ingesting chemicals. I add + +my voice. The four closest friends of my youth were highly intelligent, ethical, humorous types, favored in person and background. Two are long dead, with alcohol a contributing factor, and a third is a +living alcoholic - if you call that living. While susceptibility varies, addiction can happen to any of us, through a subtle process where the bonds of degradation are too light to be felt until they are too +strong to be broken. And I have yet to meet anyone, in over six decades of life, whose life was worsened by overfear and overavoidance of such a deceptive pathway to destruction. + +Envy, of course, joins chemicals in winning some sort of quantity price for causing misery. It was wreaking havoc long before it got a bad press in the laws of Moses. If you wish to retain the contribution of +envy to misery, I recommend that you never read any of the biographies of that good Christian, Samuel Johnson, because his life demonstrates in an enticing way the possibility and advantage of transcending +envy. + +Resentment has always worked for me exactly as it worked for Carson. I cannot recommend it highly enough to you if you desire misery. Johnson spoke well when he said that life is hard enough to swallow +without squeezing in the bitter rind of resentment. + +For those of you who want misery, I also recommend refraining from practice of the Disraeli compromise, designed for people who find it impossible to quit resentment cold turkey. Disraeli, as he rose to +become one of the greatest Prime Ministers, learned to give up vengeance as a motivation for action, but he did retain some outlet for resentment by putting the names of people who wronged him on pieces of +paper in a drawer. Then, from time to time, he reviewed these names and took pleasure in noting the way the world had taken his enemies down without his assistance. + +Well, so much for Carson's three prescriptions. Here are four more prescriptions from Munger: + +First, be unreliable. Do not faithfully do what you have engaged to do. If you will only master this one habit you will more than counterbalance the combined effect of all your virtues, howsoever great. If +you like being distrusted and excluded from the best human contribution and company, this prescription is for you. Master this one habit and you can always play the role of the hare in the fable, except that +instead of being outrun by one fine turtle you will be outrun by hordes and hordes of mediocre turtles and even by some mediocre turtles on crutches. + +I must warn you that if you don't follow my first prescription it may be hard to end up miserable, even if you start disadvantaged. I had a roommate in college who was and is severely dyslexic. But he is +perhaps the most reliable man I have ever known. He has had a wonderful life so far, outstanding wife and children, chief executive of a multibillion dollar corporation. + +261 + +If you want to avoid a conventional, main-culture, establishment result of this kind, you simply can't count on your other handicaps to hold you back if you persist in being reliable. + +I cannot here pass by a reference to a life described as "wonderful so far," without reinforcing the "so far" aspects of the human condition by repeating the remark of Croesus, once the richest king in the +world. Later, in ignominious captivity, as he prepared to be burned alive, he said: "Well now do I remember the words of the historian Solon: "No man's life should be accounted a happy one until it is over." + +My second prescription for misery is ro learn everything you possibly can from your own personal experience, minimizing what you learn vicariously from the good and bad experience of others, living and dead. +This prescription is a sure-shot producer of misery and second-rate achievement. + +You can see the results of not learning from others' mistakes by simply looking about you. How little originality there is in the common disasters of mankind - drunk driving deaths, reckless driving maimings, +incurable venereal diseases, conversion of bright college students into brainwashed zombies as members of destructive cults, business failures through repetition of obvious mistakes made by predecessors, +various forms of crowd folly, and so on. I recommend as a memory clue to finding the way to real trouble from heedless, unoriginal error the modern saying: "If at first you don't succeed, well, so much for +hang gliding." + +The other aspect of avoiding vicarious wisdom is the rule for not learning from the best work done before yours. The prescription is to become as non-educated as you reasonable can. + +Perhaps you will better see the type of non-miserable result you can thus avoid if I render a short historical account. There once was a man who assiduously mastered the work of his best predecessors, despite +a poor start and very tough time in analytic geometry. Eventually his own original work attracted wide attention and he said of that work: + +"lfl have seen a little farther than other men it is because I stood on the shoulders of giants." + +The bones of that man lie buried now, in Westminster Abbey, under an unusual inscription: + +"Here lie the remains of all that was mortal in Sir Isaac Newton." + +My third prescription for misery is to go down and stay down when you get your first, second, or third severe reverse in the battle oflife. Because there is so much adversity out there, even for the lucky and +wise, this will guarantee that, in due course, you will be permanently mired in misery. Ignore at all cost the lesson contained in the accurate epitaph written for himself by Epicetus: "Here lies Epicetus, a +slave, maimed in body, the ultimate in poverty, and favored by the Gods." + +My final prescription to you for a life of fuzzy thinking and infelicity is to ignore a story they told me when I was very young about a rustic who said: "I wish I knew where I was going to die, and then I'd +never go there." Most people smile (as you did) at the rustic's ignorance and ignore his basic wisdom. If my experience is any guide, the rustic's approach is to be avoided at all cost by someone bent on +misery. To help fail you should discount as mere quirk, with + +262 + +no useful message, the method of the rustic, which is the same one used in Carson's speech. What Carson did was to approach the study of how to create X by turning the question backward, that is, by studying +how to create non-X. The great algebraist, Jacobi, had exactly the same approach as Carson and was known for his constant repetition of one phrase: "Invert, always invert." It is in the nature of things, as +Jacobi knew, that many hard problems are best solved only when they are addressed backward. For instance, when almost everyone else was trying to revise the electromagnetic laws of Maxwell to be consistent +with the motion laws of Newton, Einstein discovered special relativity as he made a 180 degree turn and + +revised Newton's laws to fit Maxwell's. + +It is my opinion, as a certified biography nut, that Charles Robert Darwin would have ranked near the middle of the Harvard School graduating class of 1986. Yet he is now famous in the history of science. +This is precisely the type of example you should learn nothing from if bent on minimizing your results from your own endowment. + +Darwin's result was due in large measure to his working method, which violated all my rules for misery and particularly emphasized a backward twist in that he always gave priority attention to evidence +tending to disconfirm whatever cherished and hard-won theory he already had. In contrast, most people early achieve and later intensify a tendency to process new and disconfirming information so that any +original conclusion remains intact. They become people of whom Philip Wylie observed: "You couldn't squeeze a dime between what they already know and what they will never learn." + +The life of Darwin demonstrates how a turtle may outrun the hares, aided by extreme + +objectivity, which helps the objective person end up like the only player without blindfold in a game of pin-the-donkey. + +If you minimize objectivity, you ignore not only a lesson from Darwin but also one from + +Einstein. Einstein said that his successful theories came from: "Curiosity, concentration, perseverance and self-criticism. And by self-criticism he meant the testing and destruction of his own well-loved +ideas. + +Finally, minimizing objectivity will help you lessen the compromises and burdens of owning worldly goods, because objectivity does not work only for great physicists and biologists. It also adds power to the +work of a plumbing contractor in Bemidji. Therefore, if you interpret being true to yourself as requiring that you retain every notion of your youth you will be safely underway, not only toward maximizing +ignorance, but also toward whatever misery can be obtained through unpleasant experiences in business. + +It is fitting now that a backward sort of speech end with a backward sort of toast, inspired by Elihu Root's repeated accounts of how the dog went to Dover, "leg over leg." To the class of 1986: + +Gentlemen, may each of you rise high by spending each day of a long life aiming low. + +263 + +- APPENDIX Two - + +WISDOM FROM CHARLES T. MUNGER AND WARREN E. BUFFETT + +On how to change people + +Suppose you've got a client who really wants to commit tax fraud. If he doesn't push the tax law away beyond the line, he can't stand it. He can't shave in the morning if he thinks there's been any cheating +he could get by with that he hasn't done. And there are people like that. They just feel they aren't living aggressively enough. + +You can approach that situation in either of two ways: (A) you can say, "I just won't work for him," and duck it. Or, (B) you can say, "Well, the circumstances of my life require that I work for him. And what +Tm doing for him doesn't involve my cheating. Therefore, I'll do it." And if you see he wants to do something really stupid, it probably won't work to tell him, + +"What you're doing is bad. I have better morals than you." + +That offends him. You're young. He's old. Therefore, instead of being persuaded, he's more likely to react with, "Who in the hell are you to establish the moral code of the whole world?" But instead, you can +say to him, "You can't do that without three other people beneath you knowing about it. Therefore, you're making yourself subject to blackmail. You're risking your + +reputation. You're risking your family, your money, etc." + +That is likely to work. And you're telling him something that's true. Do you want to spend a lot of time working for people where you have to use methods like that to get them to behave well? I think the +answer is no. But if you're hooked with it, appealing to interest is likely to work better as a matter of human persuasion than appeal to anything else. That, again, is a powerful psychological principle with +deep biological roots. + +I saw that psychological principle totally blown at Salomon. Salomon's general council knew that the CEO, Gutfreund, should have promptly told the Federal authorities all about Salomon's trading improprieties +in which Gutfreund didn't participate and which he hadn't caused. And the general counsel urged Gutfreund to do it. He told Gutfreund, in effect, "You're probably not legally required to do that, but it's the +right thing to do. You really should." + +But it didn't work. The task was easy to put off - because it was unpleasant. So that's what Gutfreund did - he put it off. + +And the general counsel had very little constituency within Salomon except for the CEO. If the CEO went down, the general counsel was going down with him. Therefore, his whole career was on the line. So to +save his career, he needed to talk the dilatory CEO into doing the right thing. + +It would've been child's play to get that job done right. All the general counsel had to do was to tell his boss, "John, this situation could ruin your life. You could lose your wealth. You could lose your +reputation... "And it would have worked. CEOs don't like the idea of being + +264 + +ruined, disgraced and fired. (Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.59.) + +On some reasons to why managers don't make rational decisions + +My most surprising discovery: the overwhelming importance in business of an unseen force that we might call "the institutional imperative." In business school, I was given no hint of the imperative's +existence and I did not intuitively understand it when I entered the business world. I thought then that decent, intelligent, and experienced managers would automatically make rational business decisions. But +I learned over time that isn't so. Instead, rationality frequently wilts when the institutional imperative comes into play. + +For example: (1) As if governed by Newton's First Law of Motion, an institution will resist any change in its current direction; (2) Just as work expands to fill available time, corporate projects or +acquisitions will materialize to soak up available funds; (3) Any business craving of the leader, however foolish, will be quickly supported by detailed rate-of-return and strategic studies prepared by his +troops; and (4) The behavior of peer companies, whether they are expanding, acquiring, setting executive compensation or whatever, will be mindlessly imitated. + +Institutional dynamics, not venality or stupidity, set businesses on these courses, which are too often misguided. After making some expensive mistakes because I ignored the power of the imperative, I have +tried to organize and manage Berkshire in ways that minimize its influence. Furthermore, Charlie and I have attempted to concentrate our investments in companies that appear alert to the problem. (Warren +Buffett, Berkshire Hathaway Inc., Letters to Shareholders, 1989, p.62.) + +On the difficulty of replacing a CEO + +Most organizations depend on the self-interest of the superior to weed out the second-rate inferior. If I'm a sales manager and I've got lots of lousy salesmen, it hurts my performance and it probably hurts +my income to keep on the sub-par performers. It certainly hurts a football coach to keep a sub-par quarterback or any other player in there ifhe can get a better one. In almost all jobs, there is a reward or +penalty system that causes the superior to think actively about whether the people beneath him are doing a first-class job and to do something about it if they aren't. + +That works all the way up to the CEO. But the CEO's superiors are the directors of the publicly held company. And are the directors of the company going to suffer if the CEO is sub-par? Probably only if +they're embarrassed. That's the way you hurt the superior in that case. You don't take away his directors' fee. And as a practical matter, you don't displace directors very often. So the only system that's +comparable to the problem of the football coach or the sales manager is probably to hurt psychically the position of the inferior director + +- and that will work. Otherwise, the motivation to correct the CEO problem is not strong unless there's a big ownership among directors - and even that doesn't always work perfectly. To change directors +usually takes the action of big shareholders. It doesn't happen any other way. It's a very awkward situation for a management or a group of directors, who have somehow selected other weak directors, to make +changes. It goes against all the natural + +265 + +societal norms to walk up to some guy at a meeting- who isn't causing any harm and is sitting there like a potted palm - and turn to him and say, "We've all thought it over. And you're really not any good." +It just doesn't happen. (Warren Buffett, Berkshire Hathaway annual meeting, 1993, Outstanding Investor Digest, June 30, 1993, p.32.) + +On the kind of people we should do business with + +I have been asked by a number of people just what secrets the Blumkins [Nebraska Furniture Mart] bring to their business. These are not very esoteric. All members of the family: (1) apply themselves with an +enthusiasm and energy that would make Ben Franklin and Horatio Alger look like dropouts; (2) define with extraordinary realism their area of special competence and act decisively on all matters within it; (3) +ignore even the most enticing propositions falling outside of that area of special competence; and (4) unfailingly behave in a high-grade manner with everyone they deal with. (Mrs. B boils it down to "sell +cheap and tell the truth".) (Warren Buffett, Berkshire Hathaway Inc., Letters to Shareholders, 1984, p.87.) + +We really don't want to buy into any organization that we felt would be lacking that quality [intellectual honesty] in the first place - because we really don't believe in buying into organizations to change +them. We may change the comp system a little or something of the sort... + +We want people joining us who already are the type that face reality and that basically [not only] tell us the truth, but tell themselves the truth - which is even more important. Once you get an organization +that lies to itself- and there are plenty that do - I just think you get into all kinds of problems. And people know it throughout the organization and they adopt the norms of what they think is happening up +above them. Particularly in a financial organization - really in any organization, but particularly in a financial organization - that is death over time. We wouldn't buy into something that we felt had that +problem with the idea that we would correct it - because we wouldn't. We've had a little experience with some organizations that have had that sort of problem. And it's not correctable - at least based on the +life span of humans. It's too much to commit to. (Warren Buffett, Berkshire Hathaway annual meeting, 2000, Outstanding Investor Digest, OID.Com, continued from December 18, 2000 &Year End 2000 Editions.) + +We find it meaningful when an owner cares about whom he sells to. We like to do business with someone who loves his company, not just the money that a sale will bring him (though we certainly understand why +he likes that as well). When chis emotional attachment exists, it signals that important qualities will likely be found within the business: honest accounting, pride of product, respect for customers, and a +loyal group of associates having a strong sense of direction. The reverse is apt to be true, also. When an owner auctions off his business, exhibiting a total lack of interest in what follows, you will +frequently find that it has been dressed up for sale, particularly when the seller is a "financial owner." And if owners behave with little regard for their business and its people, their conduct will often +contaminate attitudes and practices throughout the company. (Warren Buffett, Berkshire Hathaway Inc., 2000 Annual Report, p.7.) + +266 + +On picking up the right character traits + +Buffett: It does pay to have the right models.. .I think that it just stands to reason that if you copy the people that you look up to - particularly if you do it at an early enough age... If you influence +the role models of a five-year old or an eight-year old or a ten-year old, then it's going to have a huge impact. + +And of course, virtually everybody starts out with their initial models being their parents. So they are the ones that are going to have a huge effect on 'em. And if that parent turns out to be a great model, +I think it's going to be a huge plus for the child. I think it beats a whole lot of other things in life to have the right models around... + +But you've got to start early. It's very tough to change behavior later on. I tell the students + +in classes, "Just pick out the person you admire the most in the class, and sit down and write the reasons why you admire him and then try and figure out why you can't have the same qualities." After all, +they're not like the ability to throw a football 60 yards or run the 100 in ten seconds flat or something like that. They're qualities of personality, character and temperament that can be emulated. + +And you can apply the reverse ofit following Charlie's theory: You can find the people you don't like and say, "What don't I like about these people?" It takes a little strength of character, but you can look +inwards and say, "Have I got some of that in me?" + +It's not complicated. Ben Graham did it, Ben Franklin did it. And nothing could be more simple than to try and figure out what you find admirable and then decide that the person you really would like to +admire is yourself And the only way you're going to do it is to take on the qualities of other people you admire. + +Munger: Also, there is no reason to look only for living models. The eminent dead are in the nature of things some of the best models around. And if a model is all you want, you're really better off not +limiting yourself to the living. Some of the very best models have been dead for a long time. (Berkshire Hathaway annual meeting, 2000, Outstanding Investor Digest, Year End 2000 Edition, pp.62-63.) + +On overconfidence + +About 99% of American management thinks that if they're wonderful at doing one thing that they'll be wonderful at doing something else. They're like a duck on a pond when it's raining + +- they're going up in the world. They start thinking that they're the ones that are causing themselves to rise. So they go over to some place where it isn't raining and they just sit there on the ground. But +nothing happens. Then they usually fire their number rwo in command or hire a consultant. They very seldom see what really happens is that they have left their circle of competence ... + +If you take the CEOs of America's largest corporations, they do not know what their circle of competence is. That's one of the reasons they make so many dumb acquisitions. They rise to the top of the business +because they're great salesmen, great production people or whatever. All of a sudden, they're running a multi-billion dollar business and their job is to allocate capital and to buy businesses. They've never +bought a business in their life. They don't know what it's all about. + +So they usually do one or rwo things. Either they set up an internal department, hire a + +267 + +bunch of guys and have them tell him something to do. Of course, the guys know if they don't tell him something to do, then there will be no jobs. So you can imagine what activity takes place then. Or they go +out and hire investment bankers who get paid by the transaction. (Warren Buffett, lecture at Stanford Law School, March 23, 1990, [3mOutstanding Investor Digest, [0mApril 18, 1990, pp.13-14.) + +On some reasons to why bad lending happen so often + +Granting the presence of perverse incentives, what are the operating mechanics that cause widespread bad loans (where the higher interest rates do not adequately cover increased risk ofloss) under our present +system? After all, the bad lending, while it has a surface plausibility to bankers under cost pressure, is, by definition, not rational, at least for the lending banks and the wider civilization. How then +does bad lending occur so often? + +It occurs (partly) because there are predictable irrationalities among people as social animals. It is now pretty clear (in experimental social psychology) that people on the horns of a dilemma, which is +where our system has placed our bankers, are extra likely to react unwisely to the example of other people's conduct, now widely called "social proo£" So, once some banker has apparently (but not really) +solved his cost-pressure problem by unwise lending, a considerable amount of imitative "crowd folly," relying on the "social proof," is the natural consequence. Additional massive irrational lending is caused +by "reinforcement" of foolish behavior, caused by unwise accounting convention in a manner discussed later in this letter. It is hard to be wise when the messages which drive you are wrong messages provided +by a mal-designed system ... + +Many eminent "experts" would not agree with our notions about systemic irresponsibility from combining (1) "free-market" pricing of interest rates with (2) government guarantees of payment. If many eminent +"experts" are wrong, how could this happen? Our explanation is that the "experts" are over-charmed with an admirable, powerful, predictive model, coming down from Adam Smith. Those discretionary interest +rates on deposits have a "free-market" + +image, making it easy to conclude, automatically, that the discretionary rates, like other free market processes, must be good. Indeed, they are appraised as remaining good even when combined with +governmental deposit insurance, a radical non-free-market element. + +Such illogical thinking displays the standard folly bedeviling the "expert" role in any soft science: one tends to use only models from one's own segment of a discipline, ignoring or underweighing others. +Furthermore, the more powerful and useful is any model, the more error it tends to produce through overconfident misuse. + +This brings to mind Ben Graham's paradoxical observation that good ideas cause more investment mischief than bad ideas. He had it right. It is so easy for us all to push a really good idea to wretched excess, +as in the case of the Florida land bubble or the "nifty fifty" corporate stocks. Then mix in a little "social proof" (from other experts), and brains (including ours) often turn to mush. It would be nice if +great old models never tricked us, but, alas, "some dreams are not to be." Even Einstein got tricked in his later years... + +We think current accounting for many high-interest-rate loans has terrible consequences in the banking system. In essence, it "front ends" into reported income revenues that would have been deferred until +much later, after risky bets were more clearly won, if more + +268 + +conservative accounting had been employed. This practice turns many a banker into a human version of one of B.F. Skinner's pigeons, since he is "reinforced" into continuing and expanding bad lending through +the pleasure of seeing good figures in the short term. The good figures substitute nicely in the mind for nonexistent underlying institutional good, partly through the process, originally demonstrated by +Pavlov, wherein we respond to a mere association because it has usually portended a reality that would make the response correct. (Charles Munger, Wesco Financial Inc., 1990 Annual Report. Berkshire Hathaway +Inc., Letters to Shareholders, 1987-1995, pp.205-208.) + +On the value of math + +53% of the world's stock market value is in the U.S. Well, if U.S. GDP [gross domestic product] grows at 4-5% a year with 1-2% inflation - which would be a pretty good, in fact it would be a very good result +- then I think it's very unlikely that corporate profits are going to grow at a greater rate than that. Corporate profits as a percent of GDP are on the high side already- and corporate profits can't +constantly grow at a faster rate than GDP. Obviously, in the end, they'd be greater than GDP. + +It's like somebody said about New York - that it has more lawyers than people. You run into certain conflicts as you go along if you say profits can get bigger than GDP. So if you have a situation where the +best you can hope for in corporate profit growth over the years is 4-5%, how can it be reasonable to think that equities - which, after all, are a capitalization of those corporate profits - can grow at 15% a +year? It's nonsense, frankly... + +The other day, I looked at the Fortune 500. And the companies on that list earned $334 billion and had a market capitalization of $9.9 trillion at year end - which would probably be up to at least $10.5 +trillion now. Well, the only money investors are going to make in the long run is what the businesses make. There's nothing added. The government doesn't throw in anything. Nobody's adding to the pot. People +take out from the pot in terms of frictional costs - investment management fees, brokerage commissions and all of that. But $334 billion is all that the investment earns. + +If you own a farm, what the farm produces is all you're going to get from the farm. If it produces $50 an acre of net profit, you'll get $50 an acre of net profit. And there's nothing about it that transforms +that in some miraculous form. If you owned all of the Fortune 500 + +- if you owned 100% ofit -you'd be making $334 billion. And if you paid $10.5 trillion for that, well, that's not a great return on investment. + +Then you might say, "Can that $334 billion double in five years?" Well, it can't double in five years with GDP growing at 4% a year or some number like that. It would just produce things so out of whack in +terms of experience in the American economy that it won't happen. Any time you get involved in these things where if you trace out the mathematics of it, you bump into absurdities, then you better change your +expectations somewhat. (Warren Buffett, Berkshire Hathaway annual meeting, 1999, Outstanding Investor Digest, December 10, 1999, p.52.) + +On advantages of scale + +In terms of which businesses succeed and which businesses fail, advantages of scale are + +269 + +ungodly important. For example, one great advantage of scale taught in all of the business schools of the world is cost reductions along the so-called experience curve. Just doing something complicated in +more and more volume enables human beings, who are trying to improve and are motivated by the incentives of capitalism, to do it more and more efficiently. The very nature of things is that if you get a whole +lot of volume through your joint, you get better at processing that volume. That's an enormous advantage. And it has a lot to do + +with which businesses succeed and fail.... + +Let's go through a list - albeit an incomplete one of possible advantages of scale. Some come from simple geometry. If you're building a great spherical tank, obviously as you build it bigger, the amount of +steel you use in the surface goes up with the square and the cubic volume goes up with the cube. So as you increase the dimensions, you can hold a lot more volume per unit area of steel. And there are all +kinds of things like that where the simple geometry - the simple reality- gives you an advantage of scale. + +For example, you can get advantages of scale from TV advertising. When TV advertising first arrived - when talking color pictures first came into our living rooms - it was an unbelievably powerful thing. And +in the early days, we had three networks that had whatever it was - say 90% of the audience. + +Well, if you were Proctor & Gamble, you could afford to use this new method of + +advertising. You could afford the very expensive cost of network television because you were selling so damn many cans and bottles. Some little guy couldn't. And there was no way of buying it in part. +Therefore, he couldn't use it. In effect, if you didn't have a big volume, you couldn't use network TV advertising - which was the most effective technique. + +So when TV came in, the branded companies that were already big got a huge tail wind. + +Indeed, they prospered and prospered and prospered until some of them got fat and foolish, which happens with prosperity- at least to some people.... + +And your advantage of scale can be an informational advantage. If I go to some remote + +place, I may see Wrigley chewing gum alongside Glotz's chewing gum. Well, I know that Wrigley is a satisfactory product, whereas I don't know anything about Glotz's. So if one is + +$.40 and the other is $.30, am I going to take something I don't know and put it in my mouth + +which is a pretty personal place, after all - for a lousy dime? + +Another advantage of scale comes from psychology We are all influenced - subconsciously + +and to some extent consciously- by what we see others do and approve. Therefore, if everybody's buying something, we think it's better. We don't like to be the one guy who's out of step. + +Again, some of this is at a subconscious level and some of it isn't. Sometimes, we consciously and rationally think, "Gee, I don't know much about this. They know more than I do. Therefore, why shouldn't I +follow them?" + +The social proof phenomenon which comes right out of psychology gives huge advantages to scale - for example, with very wide distribution, which of course is hard to get. One advantage of Coca-Cola is that +it's available almost everywhere in the world. + +Well, suppose you have a little soft drink. Exactly how do you make it available all over the Earth? The worldwide distribution setup - which is slowly won by a big enterprise - gets to be a huge advantage +And if you think about it, once you get enough advantages of that + +type, it can become very hard for anybody to dislodge you. 270 + +There's another kind of advantage to scale. In some businesses, the very nature of things is to sort of cascade toward the overwhelming dominance of one firm. + +The most obvious one is daily newspapers. There's practically no city left in the U.S., aside from a few very big ones, where there's more than one daily newspaper. + +And again, that's a scale thing. Once I get most of the circulation, I get most of the advertising. And once I get most of the advertising and circulation, why would anyone want the thinner paper with less +information in it? So it tends to cascade to a winner-take-all situation. And chat's a separate form of the advantages of scale phenomenon. + +Similarly, all these huge advantages of scale allow greater specialization within the firm. Therefore, each person can be better at what he does... + +On the subject of advantages of economies of scale, I find chain stores quite interesting. Just think about it. The concept of a chain store was a fascinating invention. You get this huge purchasing power - +which means chat you have lower merchandise costs. You get a whole bunch oflittle laboratories out there in which you can conduct experiments. And you get specialization. If one little guy is trying to buy +across 27 different merchandise categories influenced by traveling salesmen, he's going to make a lot of dumb decisions. But if your buying is done in headquarters for a huge bunch of stores, you can get very +bright people chat know a lot about + +refrigerators and so forth to do the buying. + +The reverse is demonstrated by the little store where one guy is doing all the buying. It's like the old story about the little store with salt all over its walls. And a stranger comes in and says to the +store owner, "You must sell a lot of salt." And he replies, "No, I don't. But you should see the guy who sells me salt." (Lecture by Charles T. Munger to the students of Professor Guilford Babcock at the +University of Southern California School of Business on April 14, 1994, Outstanding Investor Digest, May 5, 1995, pp.52-54.) + +On disadvantages of scale + +For example, we - by which I mean Berkshire Hathaway - are the largest shareholder in Capital Cities/ABC. And we had trade publications there that got murdered - where our competitors beat us. And the way +they beat us was by going to a narrower specialization. + +We'd have a travel magazine for business travel. So somebody would create one which was addressed solely at corporate travel departments. Like an ecosystem, you're getting a narrower and narrower +specialization. + +Well, they got much more efficient. They could tell more to the guys who ran corporate travel departments. Plus, they didn't have to waste the ink and paper mailing out stuff that corporate travel departments +weren't interested in reading. It was a more efficient system. And they beat our brains out as we relied on our broader magazine. + +That's what happened to The Saturday Evening Post and all chose things. They're gone. What we have now is Motorcross- which is read by a bunch of nuts who like to participate in tournaments where they turn +somersaults on their motorcycles. But they care about it. For them, it's the principal purpose of life. A magazine called Motorcross is a total necessity to those people. And its profit margins would make you +salivate. Just think of how narrowcast chat kind of publishing is. So occasionally, scaling down and intensifying gives you the big advantage. Bigger is not always better. + +271 + +The great defect of scale, of course, which makes the game interesting - so that the big people don't always win - is that as you get big, you get the bureaucracy. And with the bureaucracy comes the +territoriality- which is again grounded in human nature. + +And the incentives are perverse. For example, if you worked for AT&T in my day, it was a great bureaucracy. Who in the hell was really thinking about the shareholder or anything else? And in a bureaucracy, +you think the work is done when it goes out of your in-basket into somebody's else's in-basket. But, of course, it isn't. It's not done until AT&T delivers what it's supposed to deliver. So you get big, fat, +dumb, unmotivated bureaucracies. + +They also tend to become somewhat corrupt. In other words, ifl've got a department and you've got a department and we kind of share power running this thing, there's sort of an unwritten rule: "If you won't +bother me, I won't bother you and we're both happy." So you get layers of management and associated costs that nobody needs. Then, while people are justifying all these layers. It takes forever to get +anything done. They're too slow to make decisions and nimbler people run circles around them. + +The constant curse of scale is that it leads to big, dumb bureaucracy - which, of course, reaches its highest and worst form in government where the incentives are really awful. That doesn't mean we don't +need governments - because we do. But it's a terrible problem to get big bureaucracies to behave. (Lecture by Charles T. Munger to the students of Professor Guilford Babcock at the University of Southern +California School of Business on April 14, 1994, Outstanding Investor Digest, May 5, 1995, p.53.) + +On how to get worldly wisdom + +I've long believed that a certain system - which almost any intelligent person can learn - works way better than the systems that most people use. As I said at the U.S.C. Business School, what you need is a +latticework of mental models in your head. And you hang your actual experience and your vicarious experience (that you get from reading and so forth) on this latticework of powerful models. And, with that +system, things gradually get to fit together in a way that enhances cognition. + +And you need the models - not just from one or two disciplines, but from [3mall [0mthe important disciplines. You need the best 100 or so models from microeconomics, physiology, psychology particularly, elementary +mathematics, hard science and engineering [and so on]. + +You don't have to be a huge expert in any of those fields. All you've got to do is take the really big ideas and learn them early and well. + +You can't learn those 100 big ideas you really need the way many students do - where you learn 'em well enough to bang 'em back to the professor and get your grade and then you empty them out as though you +were emptying a bathtub so you can take in more water next time. If that's the way you learn the 100 big models you're going to need, [you'll be] an "also ran" in the game of life. You have to learn the +models so that they become part of your ever used repertoire. (Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, December 29, 1997, +p.24.) + +On what something really mean + +By its nature, the U.S. is running a substantial merchandise trade deficit. If you buy more + +272 + +from the rest of the world than you're selling them - which is what happens by definition when you're running a trade deficit - you have to balance the books. They have to get something - some capital asset - +in exchange: They may get a government bond. They may get a piece of a U.S. business. But they have to get something. + +The key thing in economics, whenever someone makes an assertion to you, is to always + +ask, "And then what?" Actually, it's not such a bad idea to ask it about everything. But you should always ask, "And then what?" + +So when you read that the merchandise trade deficit is $9 billion, what else does that mean? It means that somehow we must also have traded $9 billion of capital assets - (future) claims on our production - +and given them to somebody else in the world. So they have to invest. They don't have any choice. And when somebody says, "Won't it be terrible if the Japanese sell all of their government bonds?" Well, they +can't without getting another American asset in exchange. There's simply no other way to do it. They could sell it to the French, but then the French have the same problem. + +So trace through the transactions on the circle whenever you talk about any specific action in economics. (Warren Buffett, Berkshire Hathaway annual meeting, 1997, Outstanding Investor Digest, August 8, 1997, +p.23.) + +On 3 timeless ideas for investing + +His [Benjamin Graham] three basic ideas - and none of them are complicated or require any mathematical talent or anything of that sort - are: + +that you should look at stocks as part ownership of a business, + +that you should look at market fluctuations in terms of his "Mr. Market" example and make them your friend rather than your enemy by essentially profiting from folly rather participating in it, and finally, + +the three most important words in investing are "margin of safety" - ... always building a 15,000 pound bridge if you're going to be driving 10,000 pound truck across it ... + +So I think that it comes down to those ideas - although they sound so simple and commonplace that it kind of seems like a waste to go to school and get a Ph.D. in Economics and have it all come back to that. +It's a little like spending eight years in divinity school and having somebody tell you that the ten commandments were all that counted. There is a certain natural tendency to overlook anything that simple +and important. (Warren Buffett, speech at New York Society of Security Analysts, December 6, 1994, Outstanding Investor Digest, May 5, 1995, p.3.) + +On how to evaluate businesses + +Leaving aside tax factors, the formula we use for evaluating stocks and businesses is identical. Indeed, the formula for valuing [3mall [0massets that are purchased for financial gain has been unchanged since it +was first laid out bya very smart man in about 600 B.C. (though he wasn't smart enough to know it was 600 B.C.). + +The oracle was Aesop and his enduring, though somewhat incomplete, investment insight was "a bird in the hand is worth two in the bush." To flesh out this principle, you must answer + +273 + +only three questions. How certain are you that there are indeed birds in the bush? When will they emerge and how many will there be? What is the risk-free interest rate (which we consider to be the yield on +long-term U.S. bonds)? If you can answer these three questions, you will know the maximum value of the bush - and the maximum number of the birds you now possess that should be offered for it. And, of course, +don't literally think birds. Think dollars. + +Aesop's investment axiom, thus expanded and converted into dollars, is immutable. It + +applies to outlays for farms, oil royalties, bonds, stocks, lottery tickets, and manufacturing plants. And neither the advent of the steam engine, the harnessing of electricity nor the creation of the +automobile changed the formula one iota - nor will the Internet. Just insert the correct numbers, and you can rank the attractiveness of all possible uses of capital throughout the universe. (Warren Buffett, +Berkshire Hathaway Inc., 2000 Annual Report, p.13.) + +On commodity businesses + +Businesses in industries with both substantial over-capacity and a "commodity" product (undifferentiated in any customer-important way by factors such as performance, appearance, service support, etc.) are +prime candidates for profit troubles. These may be escaped, true, if prices or costs are administered in some manner and thereby insulated at least partially from normal market forces. This administration can +be carried out (a) legally through government intervention (until recently, this category included pricing for truckers and deposit costs for financial institutions), (b) illegally through collusion, or (c) +"extra legally" through OPEC-style foreign cartelization (with tag-along benefits for domestic non cartel operators). + +If, however, costs and prices are determined by full-bore competition, there is more than + +ample capacity, and the buyer cares little about whose product or distribution services he uses, industry economics are almost certain to be unexciting. They may well be disastrous. + +Hence the constant struggle of every vendor to establish and emphasize special qualities of product or service. This works with candy bars (customers buy by brand name, not by asking for a "two-ounce candy +bar") but doesn't work with sugar (how often do you hear, "I'll have a cup of coffee with cream and C & H sugar, please"). + +In many industries, differentiation simply can't be made meaningful. A few producers in such industries may consistently do well if they have a cost advantage that is both wide and sustainable. By definition +such exceptions are few, and, in many industries, are non-existent. For the great majority of companies selling "commodity" products, a depressing equation of business economics prevails: persistent +over-capacity without administered prices (or costs) equals poor profitability. + +Of course, over-capacity may eventually self-correct, either as capacity shrinks or demand expands. Unfortunately for the participants, such corrections often are long delayed. When they finally occur, the +rebound to prosperity frequently produces a pervasive enthusiasm for expansion that, within a few years, again creates over-capacity and a new profitless environment. In other words, nothing fails like +success. + +What finally determines levels of long-term profitability in such industries is the ratio of supply-tight to supply-ample years. Frequently that ratio is dismal. (It seems as if the most + +274 + +recent supply-tight period in our textile business - it occurred some years back - lasted the better part of a morning.) + +In some industries, however, capacity-tight conditions can last a long time. Sometimes actual growth in demand will outrun forecasted growth for an extended period. In other cases, adding capacity requires +very long lead times because complicated manufacturing facilities must be planned and built. (Warren Buffett, Berkshire Hathaway Inc., Letters to Shareholders, 1982, pp.56-57.) + +On paying cash out or keeping it in the business + +When we have capital around, we have three questions... First, "Does it make more sense to pay it out to the shareholders than to keep it within the company?" The sub-question on that is, "If we pay it out, +is it better off to do it via repurchases or via dividend?" The test for whether we pay it out in dividends is, "Can we create more than a dollar of value within the company with that dollar by retaining it +rather than paying it out?" + +And you never know the answer to that. But so far, the answer, as judged by our results, is, "Yes, we can". And we think that prospectively we can. But that's a hope on our part. It's justified to some extent +by past history, but it's not a certainty. + +Once we've crossed that threshold, then we ask ourselves, "Should we repurchase stock?" + +Well, obviously, if you can buy your stock at a significant discount from conservatively calculated intrinsic value and you can buy a reasonable quantity, that's a sensible use for capital. + +Beyond that, the question becomes, "If you have the capital and you think that you can create more than a dollar, how do you create the most value with the least risk?" And that gets to business risk.. .I can +determine it by looking at the business, the competitive environment in which it operates and so on. + +So once we cross the threshold of deciding that we can deploy capital so as to create more than a dollar of present value for every dollar retained, then it's just a question of doing the most intelligent +thing you can find. And the cost of every deal that we do is measured by the second best deal that's around at a given time - including doing more of some of the things we're already in. (Warren Buffett, +Berkshire Hathaway annual meeting, 2001, Outstanding Investor Digest, Year End 2001 Edition, pp.38-39.) + +On how to avoid problems + +We handle negotiations way different than anybody. When we bought See's Candy, I spent an hour there. Every business we've bought on one call. On the Borsheim's deal, I dropped over to Ike Friedman's house +for half an hour. He showed me some figures that weren't audited penciled on a piece of paper. + +lfl need a team oflawyers and accountants, it isn't going to be a good deal. We've never + +had an extended negotiation with anybody about anything. That's just not our style. If it's going to be that way, I don't want to deal with them - because it's going to ruin my life sooner or later. So we +just walk away. (Warren Buffett, lecture at Stanford Law School, March 23, 1990, Outstanding Investor Digest, April 18, 1990, p.18.) + +275 + +Buffett: Some businesses are a lot easier to understand than others. And Charlie and I don't like difficult problems. If something is difficult to figure... We'd rather multiply by 3 than by1t. Munger: That's +such an obvious point. Yet so many people think that if they just hire somebody with the appropriate labels, they can do something very difficult. That is one of the most dangerous ideas a human being can +have. All kinds of things can create problems by causing complexity. The other day I was dealing with a problem - it was a new building. And I said, "This problem has three things I've learned to fear- an +architect, a contractor and a hill." If you go through life like that, I think you'll at least make fewer mistakes than people who think they can do anything, no matter how complex, by just hiring somebody +with a credible + +label. You don't have to hire out your thinking if you keep it simple... + +Buffett: If you get into some complicated business, you can get a report that's 1,000 pages thick and you can have Ph.D.'s working on it. But it doesn't mean anything. What you'll have is a report. But you +won't have any better understanding of that business and what it's going to look like in 10 or 15 years. The big thing to do is to avoid being wrong. (Berkshire Hathaway annual meeting, 1994, Outstanding +Investor Digest, June 23, 1994, p.23.) + +On the real risk of investing + +In our opinion, the real risk that an investor must assess is whether his aggregate after-tax receipts from an investment (including those he receives on sale) will, over his prospective holding period, give +him at least as much purchasing power as he had to begin with, plus a modest rate of interest on that initial stake. Though this risk cannot be calculated with engineering precision, it can in some cases be +judged with a degree of accuracy that is useful. The primary factors bearing upon this evaluation are: + +The certainty with which the long-term economic characteristics of the business can be evaluated; + +The certainty with which management can be evaluated, both to its ability to realize the full potential of the business and to wisely employ its cash flows; + +The certainty with which management can be counted on to channel the rewards from the business to the shareholders rather than to itself; + +The purchase price of the business: + +The levels of taxation and inflation that will be experienced and that will determine the degree by which an investor's purchasing power return is reduced from his gross return. (Warren Buffett, Berkshire +Hathaway Inc., Letters to Shareholders, 1993, p.135.) + +On the difficulty of developing a fair social system + +Let's just say, Sandy, that it was 24 hours before you were born, and a genie appeared, and said "Sandy, you look like a winner. I have enormous confidence in you, and what I'm going to do is let you set the +rules of the society into which you will be born. You can set the economic rules, thesocial rules, and whatever rules you set will apply during your lifetime, and your children's lifetimes." + +And you'll say, "Well, that's nice, but what's the catch?" + +And the genie says, "Here's the catch. You don't know if you're going to be born rich or poor, white or black, male or female, able-bodied or infirm, intelligent or retarded. All you + +276 + +know is that you're going to get one ball out of a barrel with, say, 5.8 billion balls in it." You're going to participate in what I call the Ovarian Lottery. And it's the most important thing that will +happen to you in your life, but you have no control over it. It's going to determine far more than your grades at school or anything else that happens to you. + +Now, what rules do you want to have? I'm not going to tell you the rules, and nobody will tell you; you have to make them up for yourself. But they will affect how you think about what you do in your will and +things of that sort. That's because you're going to want to have a system that turns out great quantities of goods and services, so that your kids can live better than you did, and so that your grandchildren +can live better than your kids. You're going to want a system that keeps Bill Gates and Andy Grove and Jack Welch working long, long after they don't need to work. You're going to want the most able people +working more than 12 hours a day. So you've got to have a system that incentives them, and that turns out goods. + +But you're also going to want a system that takes care of the bad balls, the ones that aren't lucky. If you have a system that is turning out enough goods and services, you can take care of them. You want a +system where people are free of fear to some extent. You don't want people worrying about being sick in their old age, or fearful about going home at night. So you'll try to design something, assuming you +have the goods and services to solve that sort of thing. You'll want equaliry of opportunity- a good public school system - to make you feel that every piece of talent out there will get the same shot at +contributing. And your tax system will follow from your reasoning on that. And what you do with the money you make is another thing to think about it. As you work through that, everybody comes up with +something a little different. I just suggest you play that little game. (Warren Buffett, "Buffett & Gates on Success", KCTS/Seattle, May 1998, transcript p.12.) + +For other issues regarding investing, business economics and managing, read the annual reports of Berkshire Hathaway Inc. (www.berkshirehathaway.com) and subscribe to Outstanding Investor Digest. +(www.oid.com) + +277 + +- APPENDIX THREE - + +PROBABILITY + +Blaise Pascal and Pierre Fermat developed the fundamental principles of probability in a series ofletters exchanged starting in the year 1654. + +Definitions + +Experiment is the process of obtaining an observation. For example: Toss a coin twice and observe what happens. + +Outcome is the possible result of the experiment. All possible outcomes of the experiment are called the sample space. The experiment of tossing a coin twice results in one of four possible outcomes - +Tail/Tail Head/Head, Head/Tail, or Tail/Head. + +Event is a set of outcomes of the experiment. One event would be: Observe at least one head. This event consists of the three outcomes HH, HT, TH A compound event is an event composed of two or more separate +events. + +Independent events - two events A and Bare independent if no event can influence the probability of the other. Event A: observe one head when flipping a coin. Event B: observe one tail when flipping another +coin. Each flip is independent of the other since whatever happens to the first coin cannot influence the flip of the second or tell us what outcome is likely to happen when we flip the second coin. + +Mutually exclusive events - two events are mutually exclusive if they cannot happen at the same time i.e. they have no outcomes in common. A single coin is tossed. There are two events: observing a head or +observing a tail. Observing a head excludes the possibility of observing a tail. Two events are non-mutually exclusive if they have one or more outcomes in common. A single die is tossed. Event A: observe a +four. Event B: observe an even number. These events have one outcome in common since an "even number" consists of the numbers 2, 4, and 6. + +Probability - a number between O and I that measures how likely an event is to happen over the long run. A probability of I means an event happens with certainty and a probability of O means it is impossible +for an event to happen. + +Arithmetic mean of a set of outcomes is usually called the average value of these outcomes. To + +find the mean of the numbers 1,8,6,4,7, we add the numbers together-26-and divide by 5 = 5.2. + +Variability shows how concentrated or spread out the outcomes are around the arithmetic mean. + +Expectation is the average value we expect to observe if we perform a large number of experiments. Also called expected value- the probability-weighted sum of all possible outcomes. + +Population - the total number of something - outcomes, objects, events, etc. It is a group that has at least one characteristic in common from which our sample of data is selected. + +278 + +Sample - a representative and randomly taken part of the population that is studied in order to draw conclusions about the population. The larger the sample, the better our estimate of the probability. But +observe that what is essential is the absolute size of the sample (e.g. the number of people who've been asked), not its proportion of the population. A random sample of 3,000 from the entire U.S. is more +predictive than a sample of 40 from a particular university. A random sample is one in which every item in the population is equally likely to be chosen. + +How do we decide the probability of an event? + +The laws of probability tell us what is likely to happen over a large number of trials. This means we can expect to make reasonable predictions what on average are likely to happen over the long run, but we +can't predict the outcome of a particular event. + +There are three ways to measure probability: the logical way, the relative frequency way, and the subjective way. + +The logical way + +The logical way can be used in situations where we know the number of outcomes and where all these outcomes are equally likely. For example in games of chance, we find the probability by dividing the number +of outcomes that are favorable to the event (yield the outcome we look for) with the total number of possible outcomes. Observe that this definition can only be applied if we can analyze a situation into +equally likely outcomes. + +What is the probability that we observe one head when tossing a coin? The number of equally likely favorable outcomes is one (head) and the total number of possible equally likely outcomes is two (head and +tail) and therefore the probability is½ or 50%. + +Relative frequency + +When an experiment can be repeated many times, probability is the proportion of times the event happened in relation to an infinite number of experiments. In most cases we don't know the probability of an +event. Why? Because we can't know all the outcomes. We must then try to estimate the long-term relative frequency by performing experiments or by finding representative information about how often an event +happened in the past. + +By representative we mean that the information must be based on the relative frequency of historical data over a large number of independent experiments or observations of the same reference class under +essentially the same conditions. The reference class is the one for which the distribution of outcomes is known or can be reasonable estimated. The more relevant cases we examine, the better our chance is to +estimate correctly the underlying probability. + +Conduct an experiment to test how likely it is that you toss head. Toss a coin 1000 times and observe what happens. Jfyou got heads 400 times the relative frequency or the fraction between the number of +tossed heads (number of times the events happened) and the total number of tosses (number of experiments) is 400/1000. Toss a coin 2000 times and observe what happens. If you got heads 900 times the relative +frequency is 900/2000. The more tosses, the less the difference will be between an events theoretical probability and the relative frequency with which it happens. In this case it will move towards the value +½. + +279 + +What is the frequency of losses? How are losses distributed over time? What is their magnitude? Insurance companies use relative frequencies. They base their premiums on an estimate of how likely it is that a +specific event that cause them to pay happen. If they assume the past is a representative guide for the future they try to find out the relative frequency of a specific "accident" by observing past +frequencies of specific accidents. + +Suppose the probability that a given house will burn is 0.3%. This means that the insurance company found historical data and other indicators about a large number of houses (for example the reference class +is "50 years of data of fires in a given area'') and discovered that, in the past, 3 out of 1,000 houses in a given area will burn. It also means that, assuming there are no changes in the causes of these +fires, we can predict approximately the same proportion of fires in the foture. An insurance company knows that in a given year a certain percentage of their policyholders will have an accident. They don't +know which ones, but they diversify their risk by insuring many individuals. What is unpredictable for one person can be predictable for a large population. But they must make sure the events are independent +and that not a single event or a confluence ofindependent events affects multiple policyholders causing the insurer to pay out on many claims at one time. For example, an insurance company who provides fire +insurance to a number of buildings in a single block may face ruin if a large fire happens. + +Subjective probability + +If an experiment is not repeatable or when there is no representative historical relative frequency, or comparable data, the probability is then a measure of our personal degree of belief in the likelihood of +an event happening. We have to make a subjective evaluation or a personal estimation using whatever information is available. But we can't just assign any number to events. They must agree with the rules of +probability. + +A New York Rangers supporter might say, "I believe that the NY Rangers have a 90% chance of winning their next match since they have been playing so well. " + +Rules of probability + +When two events are independent (no event can influence the probability of the other), the probability that they both will happen is the product of their individual probabilities. We can write this as: Both A +and B will happen= P(A) x P(B). + +A company has two independent manufacturing processes. In process one, 5% of the produced items are defective, and in process two, 3 %. If we pick one item from each process, how likely is it that both items +are defective? 0.15% (0.05 x 0.03). + +This rule is changed if the events are dependent. In many situations the probability of an event depends on the outcome of some other event. Events are often related in a way so that if one event happens, it +makes the other event more or less likely to happen. For example, if we toss a die and event A is: observe an even number, and event B: observe a number less than 4, then given we know B has happened, the +probability is 1/3. This is called a conditional probability or the probability that an event happen given that some other event has happened. Conditional probabilities involve dependent events. The +conditional probability of A given B is 1/3 since we know B was either 1,2 or 3 and only 2 implies event A. + +280 + +What is the probability that there are two boys in a two-child family given that there is at least one boy? Ask: What can happen or what are the number of outcomes that are equally likely to happen? Boy/Boy- +Girl/Girl - Boy/Girl - Girl/Boy. Since we already know that there is "at least one boy'; we can rule out scenario "Girl/Girl" The probability is therefore 113 or 33%. + +What is the probability that there are two boys in a two-child family given that the first-born is a boy? The number of outcomes that are equally likely to happen are: Boy/Boy - Girl/Girl - Boy/Girl - +Girl/Boy. Since we already know that the older child is a boy, we can rule out scenario GB and GG. The probability is 50%. + +A problem in conditional probability that has caused many mathematics professors problems, is the Monty Hall Dilemma. The columnist Marilyn vos Savant (Parade 1990, Sept 9, p. 13.) asked the following +problem: + +"Suppose you're on a game show, and you're given the choice of three doors. Behind one door is a car; behind the others, goats. You pick a door, say No. l, and the host, who knows what's behind the doors, +opens another door, say No. 3, which has a goat. He then says to you, 'Do you want to pick door No. 2?' Is it to your advantage to switch your choice?" + +How would you answer? Assume we always have the opportunity to switch. Make a table of possible outcomes and test in how many outcomes it pays to switch doors. + +Door 1 + +Door2 + +Door3 + +Car + +Goat + +Goat + +Goat + +Car + +Goat + +Goat + +Goat + +Car + +Assume you choose door number 1. What are then the consequences if the car is in door 1, + +2 or 3? + +Car behind door + +Host 012ens door + +You switch + +You don't switch + +1 + +2 + +Lose + +Win + +2 + +3 + +Win + +Lose + +3 + +2 + +Win + +Lose + +2/3 + +1/3 + +We should always switch doors since we win 2/3 of the time. They key to this problem is that we know ahead of the game (conditional) that the host knows what is behind each door and always opens a door with a +goat behind it. + +When two events are mutually exclusive (can't both happen at the same time), the probability that one or the other will happen is the sum of their respective probabilities. We can write this as: Either A or B +will happen = P(A) + P(B). + +What is the probability that we get either a two or a four when a single die is tossed once? There are 6 outcomes and the two events ("getting a two" and ''getting a four") have no outcomes in common. We +can't get both a two and a four on the same toss. How many favorable outcomes are + +281 + +there or in how many ways can we get a two? In one out of six. In how many ways can we get a four? In one out of six. The probability that we get a four or a six is 1/6 + 1/6 = 33%. + +When two events are non-mutually exclusive (both can happen at the same time), the probability that at least one of them will happen is equal to the sum of the probabilities of the two events minus the +probability that both events happen. We can write this complementary rule as: P(A) + P(B) - P(A and B). + +Assume that the probability a Los Angeles teenager ownsa surfing board is 25%, a bicycle 85%, and owning both 20%. If we randomly choose a Los Angeles teenager, the probability that he or she owns a surfing +board or a bicycle is (0.25 + 0.85) - 0.20 = 90%. These events had two outcomes in common since the teenager could have both a surfing board and a bicycle. + +Sometimes it is easier to deal with problems if we turn them backwards. The probability of an event not happening is 1 minus the probability it will happen. If the probability of an event A is 30%, then the +probability that the event won't happen is 70% because "not event A" is the complement of the event A. The sum of probability of an event happening and probability of the same event not happening is always 1. + +What is the probability that we get at least one six in four rolls of a single die? We turn the question around and calculate the probability of "not getting any sixes in four rolls ofa die''. There are four +independent events - not getting a six on the first throw... second... The probability of each one is 516 since there are five outcomes (1,2,3,4,5) which results in the event "no six" and each is independent +of what happened before. This means that the probability of not getting any sixes are 516 x 516 x 516 x 516 or 48.2%. Therefore "the probability ofgetting at least one six" is 1 + +- [3m0.482 or 51.8%. [0mCounting possible outcomes + +The multiplication principle says that if one event can happen in "n" different ways, and a second event can happen independent of the first in "m" different ways, the two events can happen in nm different +ways. + +Suppose there are 4 different flights between Los Angeles and New York, 3 between New York and Boston and 5 between Boston and Bermuda. The number of itineraries assuming we can connect between any of the +stated flights are 4 x 3 x 5 = 60. + +Permutations or rearrangements mean the different ways we can order or arrange a number of objects. + +We have 3 hats to choose from - one black, one white and one brown. In how many ways can we arrange them if the order white, black and brown is different from the order black, white and brown? This is the +same as asking how many permutations there are with three hats, taken three at a time. We can arrange the hats in 6 ways: Black-White-Brown, Black-Brown-White, White Black-Brown, White-Brown-Black, +Brown-White-Black, Brown-Black-White. + +Another way to think about this: We have three boxes in a row where we put a different hat in each box. We can fill the first box in three ways, since we can choose between all three hats. We can then fill +the second box in two ways, since we now can choose between only two hats. We can fill + +282 + +the third box in only one way, since we have only one hat left. This means we can fill the box in 3 x 2 x 1 = 6 ways. + +Another way to write this is 3!If we haven (6) boxes and can choose from all of them, there are n (6) choices. Then we are left with n-1 (5) choices for box number two, n-2 (4) choices for box number three +and so on. The number of permutations of n boxes is n!. What n! - Factorial- means is the product of all numbers from 1 ton. + +Suppose we havea dinner in our home with 12 people sitting around a table. How many seating arrangements are possible? The first person that enters the room can choose between twelve chairs, the second +between eleven chairs and so on, meaning there are 12! or 479,001,600 different seating arrangements. + +The number of ways we can arrange r objects from a group of n objects is called a permutation of n objects taken rat a time and is defined as n! / (n-r)! + +A safe has 100 digits. To open the safe a burglar needs to pick the correct 3 different numbers. Is it likely? The number ofpermutations or ways ofarranging 3 digits from 100 digits is 970,200 + +(100!/(J 00-3J!). If every permutation takes the burglar 5 seconds, all permutations are tried in + +56 days assuming a 24-hour working day. + +Combinations means the different ways we can choose a number of different objects from a group of objects where no order is involved, just the number of ways of choosing them. + +In how many ways can we combine 2 flavors of ice cream if we can choose from strawberry (SJ, + +vanilla (V), and chocolate (CJ without repeated flavors?We can combine them in 3 ways: SV,SC, VC. VS and SVare a combination of the same ice creams. The order doesn't matter. Vanilla on the top is the same as +vanilla on the bottom. + +The number of ways we can select r objects from a group of n objects is called a combination of n objects taken rat a time and is defined as n! / r!(n-r)! + +The numberof ways we can select 3 people taken from agroup of 10 people is 120 (10!/3!(10-3J!). + +The binomial distribution + +Suppose we take a true-false test with 10 questions. We don't know anything about the subject. All we can do is guess. To pass this test, we must answer exactly 5 questions correct. Are we likely to do that +by guessing? + +How should we reason? Ask: How many equally likely independent outcomes are there when we guess? There are 2 possible outcomes. Either we are right or wrong. If the test only had one question, the probability +that we guess the right answer is 50%. The probability that we guess the wrong answer is also 50% {1- the probability of guessing the right answer). + +What is the total number of equally likely outcomes? Since every question has 2 possible outcomes and there are 10 questions there are a total of 210 outcomes or 1,024 possible true false combinations. We can +answer the test in 1,024 different ways. What is the number of favorable outcomes? There is only one way we can answer all 10 questions right (or wrong). They all have to be right (or wrong). The chance of +getting all 10 answers right or wrong by guessing is therefore 1 in 1024. This means that if we took the test 1,024 times and guessed + +283 + +randomly at the answers each time, just once in 1,024 times should we expect to get all 10 + +answers right or wrong. + +In how many ways can we be right on 5 questions? Let's go back to combinations and ask: in how many ways can we select 5 questions if we can choose from 10 questions? There are 252 ways (10!/5!(10-5)!) we can +answer 10 questions to get exactly a score of 5. Since each guess has a 50% probability of being right and there are 10 questions and we want to be right on exactly 5 of them and there are 252 equally likely +ways we can answer 5 questions, then the probability that we answer exactly 5 questions right is (0.5)5 x (0.5)5 x 252 = 24.6% + +How likely is it then that we answer at least 5 questions correctly? This probability must be higher since we also can answer 6, 7, 8, 9 or 10 questions correct. Therefore we must add the probability that we +guess 6, 7, 8, 9, and 10 questions correct. + +In how many ways can we be right on 5 questions? 10!/5!(10-5)! = 252 ways In how many ways can we be right on 6 questions? 10!/6!(10-6)! = 210 ways In how many ways can we be right on 7 questions? +10!/7!(10-7)! = 120 ways In how many ways can we be right on 8 questions? 10!/8!(10-8)! 45 ways In how many ways can we be right on 9 questions? 10!/9!(10-9)! = 10 ways Inhowmanywayscanweberighton +lOquestions? 10!/10!(10-10)!= 1 way + +Total = 638 ways + +Since each guess has a 50% probability of being right and there are 10 questions and we want to be right on at least 5 of them and there are 638 equally likely ways we can answer at least 5 questions, the +probability that we answer at least 5 questions right is (0.5)5 x (0.5) 5 x 638 = 62.3%. + +The example illustrated a binomial experiment. The probability distribution for a binomial experiment is: Number of possible ways of selecting k things from n things (observing k successes inn trials) x +(probability of success)k (1 - probability of success)n-k + +If we put in the above figures we get: 252 x (0.5)5 x (0.5)5 + 210 x (0.5)6 x (0.5)4 + 120 x + +(0.5)7 x (0.5)3 + 45 X (0.5)' X (0.5)2 + 10 X (0.5)9 X (0.5)' + lx (0.5)' 0 X (0.5)0 = 62.3% + +Binomial experiments have the following characteristics: An event that is repeatable or the experiment consists of n number of identical and independent trials. There are only two outcomes in every trial - +success/failure, right/wrong, present/absent, 0/1 etc. and the probabilities of success and failure are constant in every trial. + +Examples of binomial experiments are firing a projectile at a target (hit/miss), developing a new drug (effective/not effective), dosing a sale (sale/no sale) etc. + +We toss a single die 5 times. How likely is it that you will roll exactly 3 sixes? What is success? Rolling a 6 on a single die. What's the probability of rolling a 6 on a single die? 1/6 (there are 6 +outcomes and one of them is a success). What is the probability of failure? 1-1/6 = 516. What is the number of trials? 5. What is the number of successes out of those trials? 3. In how many ways can you roll +three sixes (successes) in 5 trials? 5!/3!(5-3)! = JO Probability= JO x (116)3 x (5/6J = 3.2% + +A boat has three independent engines and needs at least two to work properly. The probability that each engine works properly is 98%. The probability that all three engines work is 94.1% + +284 + +) . + +(0.983 The probability that at least one engine fails (either engine 1, 2 or 3) is therefore 5.9% + +(this is the same as the probability that exactly 1 engine fail + exactly 2 engines fails + exactly 3 engines fails). + +What is the probability that at least 2 engines work? Let's go back to combinations and the binomial distribution: probability (3 engines work) + probability (2 engines work) = 3!/3!(3-3)! x (0.98)3 x (0.02)" ++ 3!/2!(3-2)! x (0.98J x (0.02)1 = 99.8816%. The probability that at least two engines will fail is therefore 0.1184%. The boat will fail to work in 1 out of 845 times. + +Let's add a backup engine. What is now the probability that at least 2 engines work? Probability (4 engines work) + probability (3 engines work) + probability (2 engines work) = 4!/4!(4-4)! x (0.98)4 X +(0.02)" + 4f/3f(4-3)! X (0.98)3 X (0.02)1 + 4f/2f(4-2)f X (0.98/ X (0.02/ = + +99.996848%. The probability that at least three engines will fail is therefore 0.003152%. The boat will now only fail in 1 out o/31,726 times. + +Binomial probabilities assume independence. It may be that the failure of one engine increases the failure probability of a second engine. For example, the failure of one engine increases the load on which +the second engine is run. Using one engine causes more stress and wear to the second engine, etc. + +Calculations to some of the examples + +Page + +150 The possible number of ways we can choose 6 numbers out of 49 are 49!/(49-6)!6! + += 13,983,816. + +24 hours equals 1,440 minutes. One 365-day year equals 525,600 minutes. 14 million minutes equals about 27 years. + +The probability we succeed is (0.8) 6 or 26%. + +) + +The probability that IO mutually independent start-ups all succeed is 0.01% (0.410 + +) . + +but the probability that at least one succeeds is 99.4% (I - 0.610 + +) . + +The probability that at least one of the parts don't work is 86.5% (1 - 0.999 2000 Assuming independence, the probability of system failure (where at least one part must fail for the system to fail) is 1 +minus the reliability of the system. + +161 Assuming independence, the probability of system failure (where both navigation systems must fail for the system to fail) is the product of the probabilities of primary and back up system failing. + +162 An event that has one chance in 20 of happening in any given year is nearly certain to happen over 50 years (I - 0.95 50 = 92.3%). If there is a 5% chance that an event happens in any given year, then the +chance that it won't happen is 95%. The chance that it won't happen over 50 years is 7.7%. This means that the probability that the event happens at least once is 92.3%. + +285 + +162 The probability that at least one accident will happen in any given year is 3.9% {1- + +0.99940). The probability that at least one accident will happen during the next 10 years is 33% (1 - 0.96110 ). + +162 The probability of a major earthquake happening in any given year (assumed to be a constant) is therefore 3.2% ((1-p)30 = 38%). The probability that a major earthquake + +) . + +will happen at least once during the next 5 years is 15% (1 - 0.9685 + +165 In a group of 1,048,576 (220) people it happens to someone. In fact, in the U.S. a country with 280 million people, one in a million chance events happen 280 times a day (1/1,000,000 x 280 million). + +165 1 person has 365 possible birthdays if we assume that there are 365 days to choose from and that all birthdays are equally likely to happen. When there are 2 persons in a group the second person can +choose among 364 possible birthdays that are not shared with the first person. The second person only shares 1 day with the first person. The chance that 2 persons share birthdays is therefore 1 out of365 or +0.27%. When there are 3 people in a group it is easier to find the likelihood that 2 of them share a birthday by first finding out how likely it is that no one of these 3 people share birthdays. When there +are 3 people in a group the third person can choose among 363 possible birthdays that are not shared with any of the first 2 persons. This means that the chance that the third person will not share birthday +with any of the first 2 persons is 363 out of365 or 99.45%. + +To find the probability that multiple events happen, we multiply the individual probabilities together. The probability that no one in a group of 3, share birthday is therefore: 365/365 x 364/365 x 363/365 = +99.18%. Therefore, the probability that 2 people in a group of 3 share birthdays is 1 - 0.9918 or 0.82%. Let's repeat this procedure for a group of 23 people: + +365 X 364 X 363 X ••••••343 = 49.30/o. + +365 23 + +Therefore, the probability that 2 people in a group of 23, share birthdays is 1 - 0.493 or 50.7%. + +178 At the end of 10 predictions, one monkey has a perfect record of predicting the direction of interest rates (1,000 x 0.510). + +180 The number of ways to get 2 successes in 10 trials are 10!/ (10-2)!2! or 45. The probability is 45x (O.8 )2 x (O. 2)8 or 0.007%. + +286 + +- APPENDIX FOUR - + +CHECKLISTS + +Helpful for achieving goals, making choices, solving problems, evaluating what is likely to be true or false etc. + +Use notions + +Use the big ideas that underlie reality + +Understand what something really means + +Simplify + +Use rules and filters + +Know what I want to achieve + +Find and evaluate alternatives + +Understand consequences and their consequences on the whole + +Quantify + +Search for and base things on evidence + +Think things through backward + +Remember that big effects come from large combinations of factors + +Evaluate the consequences ifI'm wrong + +What is the issue? + +What's the question? What is this really about? + +What's the essence or nub of the issue? What is then the key question? + +Relevant? Solvable? Important? Knowable? Utility- applicability? + +Do I understand what the subject is all about? In order to have an opinion on a subject I need some relevant data and basic knowledge about the subject, otherwise just say: "I don't know". + +Is my judgment here better than others? + +What must I predict here and is it predictable? + +Is a decision needed? What happens if I don't deal with this? Is this something I can do anything about? Should "I" do this? + +Over what period of time am I considering this issue? Where am I at present? From whose point of view? + +Simplify by deciding big "no-brainer questions" first and begin from where I am. + +Understand what it means + +Translate words and ideas in terms I understand. Do I understand what words and statements really mean and imply? Does it mean anything? Will it help me make useful predictions on what is likely to happen? + +287 + +- Do I understand how and why something works and happens? What is it doing? Why does it do that? What is happening? How and why is this happening? What is the consequence of this (observation, finding, +event, experience...)? + +- Definitions and implications? + +Filters and Rules + +- Use filters incl. rules and default rules - what test(s) can I make? + +- Adapt to my psychological nature, abilities, advantages, and limitations + +- Consider values and preferences and therefore priorities and what I want to avoid + +What do I specifically and measurable want to achieve and avoid and when and why? + +- What future "value" do I want to achieve? Target numbers? Target effects? Time horizon? + +- Assume I have already reached my target. What would this imply in numbers and effects? What must then have been achieved? Is it (target) reasonable? Is it reasonable ifI reverse this to the present? + +- Do I have ways to measure to what degree my goal is being achieved? Key variables or components of yardstick? + +- IfI achieve this what will happen? Do I want that to happen? + +- Can I break my goal into short-term goals with deadlines? + +- What is my real reason for doing this? Is it because I want to or because I have to? Have I stated my goal from internal and external realities or am I biased now or influenced by some psychological forces? + +- Can I express my goal in a way that makes it easier to see how it is going to be achieved? + +- Is this the true goal for what I want to achieve? + +What is the cause of that? + +- To achieve my goal I must understand what causes my goal to be achieved + +- What is the equation for goal and what evidence do I have for that? + +- What don't I want to achieve? What causes non-goal and what can I do to avoid that? What must I not do or what must I avoid? + +- What variables influence the system? What are the critical forces and variables, the ones that account for the main outcome? What is the key unknown? What is the certainty with which I can evaluate, +optimize ... the different variables? + +- Which variables are dependent on other variables (or situation, environment, context, timing, behavior) and which ones act independently of each other? + +- What force causes a variable to be achieved? What produces the force(s)? Are there short and long-term forces? What is their relative strength? How do they combine and interact and what are the effects? How +can I get many forces to operate together in the same direction? What lack of force would destroy the system? What produces this force? How predictable are they? What can the forces in place rationally expect +to cause? What forces are temporary and which ones are permanent? How will the system change as the forces that act on the variable change? + +- How resistant is the system to a change in the variables and/or forces? What are the likely + +288 + +wanted and unwanted short- and long-term consequences (on numbers and effects) of changes (up/down) - scale, size or mass, strength, intensity, length, time horizon, environment, participants etc. - in the +variables or forces? What happens when a number of small causes operate over a long time? What are the consequences if a force acts on the variable over a long time? Which force could change it? What is +needed to create a critical mass? What forces when added can create a critical mass? How? Will something else happen when I change a variable or force? What must happen for a force to change? Can a change +produce other consequences (observe that I am interested in effects on the whole system and the final outcome)? Does a change in one variable make a dramatic difference in outcome? Will the properties also +change? What are the consequences if the relation between the variables changes? What is the change point? Barriers? Catalyst? Tipping point? Inflection point? Break point? Limits? Is there a time lag before +effects happen? Feedback? What can speed up the cause? What are the critical points when the effects get reversed? What can I change in the equation and what can others change? How? Who? When? Which variables +must I change to achieve goal? How can I measure the amount of change? Degree of sensitivity ifl change the assumptions? Effects on goal and path? What will happen ifl hold one variable constant? Ifl at the +same time increase one variable and decrease another? Net effect? Ifl change one variable or force at a time? What is it in the environment that can change the situation? What other advantages and +disadvantages can I achieve if I optimize one of the variables? What must happen to cause a change in outcome? Is it still a variable ifl change the conditions? + +- Are there exceptions to the equation and why? What conditions are required to achieve goal? Has my goal different cause short-term and long-term? Is the cause time-dependent? Can I deduce the cause by +observing the effects? Have I looked upon the system from different angles and viewpoints? What does the measurement of the subject depend on? + +- What is the major constraint that limits the goal from being achieved? + +What available alternatives do I have to achieve my goal? + +- Judge alternatives in terms of goal, subject in question, rules and filters, cause and effect, human behavior, evidence, counter evidence, simplicity and opportunity cost of money, time, other resources, +effort, understanding, risk and mental stress. + +- What evidence (incl. models) do I have that these alternatives are most likely to achieve goal? + +- Are they depending on time horizon or event? + +- What are the likely consequences of each action? What possible outcomes can happen? Likelihood? How desirable is each consequence? + +- Do I forego any future opportunities ifl make a specific action now? + +What are the consequences? + +- Find out which alternative are most likely to achieve my goal by estimating their likely consequences + +- If I do this, what will happen? Why will this not happen? + +- What are the likely (logical) wanted and unwanted (or unintended) consequences + +289 + +(quantitative and qualitative) and consequences of consequences (immediate and over the course ofa long period) of each alternative/event (proposition) factoring in relevant variables? + +- What are the different scenarios and outcomes that can happen? What is likely to happen short and long-term based on the evidence? + +- What can help me make predictions on consequences or if something is likely to be true or false? + +- What must happen for the goal to be achieved? How likely is it that the necessary events will happen and happen to me? What does the probabilities favor? What will happen ifI reverse the proposition? + +- What are the uncertainties that can significantly influence the outcome? What unintended consequences are there due to repeating effects, complications ... ? Is the net effect positive? Does the +consequences predict anything else? What else does this mean? + +- What are the consequences if this is true or false? + +- Have I considered the whole system from different viewpoints? Have I considered social, financial, physical and emotional consequences? What are others likely to do? What are my experiences of earlier +behavior? What happens when others do the same? + +Bias + +- Is there any reason for bias due to self-interest or psychological influences that may cause misjudgment? + +- Is this a biased statement or a fact? What are factual judgments and what are value judgments? + +- How reliable is he? Is he competent enough to judge? Credentials? What is his purpose with this? Does he have any motive to lie? How does he know that this is true? + +The hypothesis + +- Based on what I want to achieve; test statement implied by goal or statement for consequences. + +- For every alternative ask: Is this alternative likely to achieve my goal (true)? For proposition ask: Is this proposition likely to be true? + +- How can I test (testability) if this is true? Can I try to prove it is false before I try to see if it's true? + +- What do I need to know ifI shall test this statement? I must first find out the equation for what causes the statement to be true so I know what is the most important I need to know the future true outcome +of and then search for the evidence for and against that this will be achieved. What is the statement that should be proved? + +- What is the simplest hypothesis? + +Look for evidence and judge the evidence + +- How likely is it that the key cause (for goal, non-goal, and proposition) will be achieved? + +- When evaluating statements or true/false, look for meaning, motives, causes, consequences and evidence for and against. + +- If this were true what would the consequences then imply? Are the consequences of it not + +being true illogical or unbelievable? Does it have any predictability? + +290 + +- How and where can I find the representative evidence if this is true? What is given? What are unquestionable truths? Will the test or other ways of measure give the same results when repeated (reliable)? +Can I test for consequences (verifiable)? Is the evidence based on what is known and have I interpreted the data correct (valid)? What evidence do I have? Evidence against? What grounds do I have for +accepting that evidence? Weight of evidence? What is the quality of the evidence? How credible is the evidence? Dependent on time, environment? Too small sample? Does the statement agree with the available +evidence? Does it violate any scientific laws or laws of nature? + +- What representative information do I have? What is happening by observation? Can I do an experiment to confirm my guess? Does it agree with experiment? + +- What is the track record (case rate, base rate frequency, variability, average rate, degree of randomness, my own experiences, environment, players, and other relevant factors for the case) on what happened +(worked and not) in the past? Is there any reason to believe that this record isn't representative for what is likely to happen in the future? What can make the future a lot different than the past? What's +been permanent and what hasn't? + +- How long can this continue? What is the major cause(s) now? What force(s) can make it continue, initiate a change, or stop it and why? Is it likely? + +- Ifl get evidence that is the opposite of my previous convictions I must ask: How does this happen? What is going on here? What evidence do I have? What grounds do I have for accepting the evidence? + +Disprove my (or others) conclusion by thinking like a prosecutor + +- Consider causes for misjudgments + +How can I test and prove that my idea and conclusion is wrong? What reasons are there why I might be wrong? Where can I find the evidence that suggest I am wrong? How credible is my evidence? What facts and +evidence disagree with my conclusion/idea? + +What major assumptions have I built the case on? Are they built on reality? Are their consequences logical? Has anyone proved that my assumptions are right? What are the consequences if my beliefs and +assumptions are wrong? + +What have I ignored or overlooked? Better alternatives? Have I ignored evidence? Have I taken into account the limitations when humans are involved? What factors are uncertain and why? Have I just projected +present trends? What have I misinterpreted? Have I used the right definitions? Did I consider and combined all the relevant factors? Have I used the appropriate measure/yardstick? Did I go wrong in the +measurement? Have I confused cause and correlation? What about if my goal is shaped by what I believe is true but it isn't? Are there random or systematic errors? What other causes can explain my results? +Have I considered the whole system and that interacting parts sometimes can vary in unexpected and unwanted ways? + +- Bias for my own ideas? Is my ego getting in the way of making an intelligent decision? Will I really beat the historical average/record? Have I looked for contrary effects? + +- What do I not see? What is the significance of this? Does an inversion of the assumption lead to a logical absurdity? Is the opposite more likely? Is there any contrary evidence? What evidence can prove it +is false (or not achieving goal)? What experimental (or experience, + +291 + +observation... ) evidence are there that it's false? More evidence in favor of that? What causes it to be false? + +- Meaning? Can I show that the consequences ofit being true are unbelievable? What is the implied effect ifl trace it out mathematically? Would the opposite of the statement be more likely? If yes, the +proposition is probably false. + +What is the downside? + +- How can I be hurt? What could possible go wrong? What can turn this into a mistake? What would the consequences be? + +- How often do things go wrong? Surprise factors? What can happen that will dramatically change the outcome? + +- What is the worst thing that could happen - the nightmare scenario? How likely is that? What will I do if it does? What are the consequences if things go from bad to worse? And what are then the +consequences? + +- What are the consequences ifI get two or three forces acting in concert against me? Which alternatives net effects are least worse? + +- Execution risk? + +- What do I least like? What am I least sure of? + +- Can an advantage give me unwanted consequences? How do I lose an advantage? + +- How can I structure the "system" to minimize the influence of negatives? Antidotes to what I don't want happen? Do I have a backup plan for surprises? Can I correct it? What rules can I install to achieve +goal and avoid non-goal? Is there a built-in safety factor? + +What are the consequences if I am wrong? + +- What key thing am I betting on? Do I risk what is important for me for something of relative low utility for me? + +What is the cost (dollars, time, mental stress etc) of being wrong weighted against the benefit or value of being right compared to the next best available opportunity? + +Ifl do this because I believe the consequences are in my best interest/it's true but I turn out wrong/it is false, what are the short- and long-term consequences (actual loss and opportunity cost loss) for my +goal and can I handle them and/or reverse them? + +IfI don't do this because I believe the consequences is not in my best interest/it's false but I turn out wrong/it's true, what are the short- and long-term consequences for my goal and can I handle them +and/or reverse them? + +- If I don't take a decision at all now because I don't believe it is necessary but I am wrong, + +what are the short- and long-term consequences for my goal and can I handle them and/or reverse them? + +What is the value? + +What is the utility or preference of each of these alternatives to me? Which alternative is most likely to achieve my goal and ultimate objective? Is it really more attractive than the other choices I have? + +What can I use as criteria to judge my alternatives against each other? + +292 + +- What do I like best if I weigh the alternatives against each other by assigning their characteristics numerical values? + +- Will it make a difference? Make an impact? How willing am I to accept certain outcomes? + +What yardstick can be used to measure progress or to measure things against? + +- What yardstick(s) do I use? What is the yardstick by which the decision is made? + +- How can I easily measure to what degree my goal are being achieved? What indicators can I track? + +- Does the "system" give people an incentive to behave in a way so that my goal will be achieved? Or does it work against the goal? + +How act now? + +- Can I execute? What specific action(s) do I have to do (must do) now? What do I need to do first? + +Who is going to do what, where, when, why and how? + +Have I decided on where the critical points (time and effects) are? + +Have I installed some kind of control stations and rules? Why is this the right rule? What are the consequences if I don't install chis rule (or change my way of doing something)? What administrative and +practical actions must I do due to the rule? How much time will it take to follow the rule? Can I control how I follow the rule? Can I install a time-limited rule? Where does the rules not work? + +Have I made an active decision? + +- Am I prepared to change the decision to reflect new information or new insights on what works and not? + +Is another decision contingent on a specific event happening? Have I evaluated the issue as it exists today? Is the underlying rationale for the decision still there? What new evidence is there that can +change the likelihood? Does my way of measuring progress give any clue of what is likely to happen in the future? Events - relevant or irrelevant? Does it make any difference for my goal (independent of time +horizon)? + +Post mortem or learning from mistakes + +How well did it or didn't it work out? Did I act? Did I do what I said? What did I think at the time? Original reasons compared to reality? + +Why did I go wrong? How? Where? Opportunity cost? + +How can I figure out if this is going to continue? Have I acted on my mistakes? How act to not repeat? What should I have done and didn't do? What should I concentrate on? What must I improve? What must I +learn? + +What exactly is the problem? + +What do I want to achieve? Why don't I achieve my goal? What happen? How does it happen? Where does it happen and not? When does it happen and not? Who's affected? + +What causes my goal? What interferes with the factors chat cause my goal? Symptoms or + +293 + +core cause? What is the single most important limiting factor for reaching my goal? What principles or assumptions do I base this on? What are the consequences if they are wrong? Assuming no limitations, what +would be the best course of action? Other consequences? + +WHAT ARE THE LIKELY CONSEQUENCES CONSIDERING HUMAN BEHAVIOR? + +What is causing me to do this? + +What are my present environment and my state of mind? What is rewarding for me to do/say ifl want to avoid pain? What do I perceive to be the consequences for me? Are they painful or pleasurable? What +psychological tendencies will influence me? Are they likely to cause a misjudgment? + +What is the context? + +What does the environment and participants (incl. size) look like? Who is the decision-maker and what are his criteria for making decisions? Who benefits and who pay? Who is responsible for outcome? Who and +what are influencing the participant's perception of reality? + +Can I judge him? + +Can I judge his character? What are his experiences? What temporary or permanent characteristics influence him (age, cultural background, health, mood... )? What environmental (present internal and external) +or situational factors influence him? Does he want to sell me something? + +What is in his self-interest to do? + +What is logical for him to do? What is rewarding for him to do ifhe want to avoid pain? What does he perceive as painful? What does he fear and why? What does he want more of or what does he not want to be +taken away? What "resources" motivates him? His health, job, family, position, reputation, status, power? What would give him an incentive or disincentive? What reward or penalty system causes his behavior? +What is he rewarded (perceived) for doing? What is he punished (perceived) for doing? How is he measured? How does he perceive the consequences of non-goal? Is it to his advantage/interest to believe (or not +to believe) something? + +What are the psychological tendencies and shortcuts that influence him and can cause misjudgment? + +What bias affects his conclusions? What external influences is there, that will likely influence him? What temptations are there that appeal to his self-interest? What activates his behavior? + +What are the consequences? + +What are the consequences for me? Will my goal still be achieved? Is what is rewarding for him also rewarding for me? Is the system set up so that the relevant participant's interest coincides with my goal? +Does it "pay him" to make the wrong decision? Does he understand + +294 + +the consequences of his behavior? What are the short-and long-term consequences for him? What are the lines of responsibility? Does he have the responsibility for the consequences? What happens when others do +the same? + +What system would I like to have if the roles were reversed? + +How would I like to be treated if the roles were reversed? What would cause me to do the things I want him to do? What are the behavioral tendencies I can use to change his behavior? How shall I behave ifl +want to guarantee non-goal? Can I now turn around and avoid chose? + +Is this the right system? + +Can I appeal to his self-interest? Can I appeal to fear of losing reputation, money, status, family..? Can I change his present associations to pain? How can I organize the system to minimize certain +influences? Have I cold him what I expect? Have I inspected what is done? Have I supported things done well? Does he have the necessary skills, knowledge and the relevant information? Does he know what is +expected of him? Does he know the goal, how he will reach it and why that is the best path? Can he measure his progress? Is it related to his daily activities? Does he have the responsibility and the +authority? Is his reward aligned with the goal? What rules can I install that will consider human weaknesses? Can I install a reverse rule? What changes must be made? Who will call for them? How likely is +that? What are his values? His goals? What does he consider to be resulc? What is his perception of the consequences if he behave like we want him to and if he doesn't? + +BUSINESS EVALUATION + +Filter 1 - Can I understand the business - predictability? + +- [3mReasons for demand [0m- How certain am I chat (and can explain why) people are likely to continue buy this type of product or service in the future? What has happened in the past and what is likely to happen +in the future? Cyclically in demand? Capacity versus demand? + +- [3mReturn characteristics [0m- Industry and company return characteristics and change over the last ten years? + +- [3mIndustry structure [0m- No of competitors and size? Who dictate the terms in chis industry? What is needed to make money in chis industry? Position within the industry? Do I know who is going to make the money +in this market and why? + +- Real Customer- Who decides what to buy and what are his decision-criteria? + +Filter 2 - Does it look like the business has some kind of sustainable competitive advantage? + +- Competitive Advantage - How certain am I that (and can explain why) they are likely to buy the product or service from the company rather than from someone else? Are the reasons virtually unchanged from +what they were ten years ago? Are these motivations likely to be unchanged over the next ten years? + +- Value - How strong and sustainable is chis advantage? Have the advantages become stronger and more durable over the years? What can destroy or reduce them? Barriers to entry? Brand loyalty? Vulnerable to +change in demand or prices? Easy to copy? Short + +295 + +product life cycle? Customer cost and incentive to switch supplier? Annual cost differential against competition? Capital investments needed? Bargaining power? Obsolescence risk? New customer alternatives? +Change in buying habits or power? Competitor potential to undercut prices assuming same cost structure? What is needed to make sure the advantages stay sustainable? Growth opportunities left? Is the demand +for the product likely to grow? Untapped unit volume demand? Pricing power? + +Profitability - Can the advantage be translated into profitability and why? How does the + +company make money? How much capital is needed to produce incremental revenues? Financial characteristics-return on capital (operating margins and capital turnover), gross margins, sales growth, cost-and +capital structure and efficiency? Normalized free cash flow? Advantages of scale? Critical variable? + +Filter 3 - Able and honest management? + +Is the management composed of competent and honest people that understands and focuses on creation of value? + +Filter 4 - Is the price right? + +Can I buy at a price that provides a good return with a huge margin of safety measured against other available alternatives and with evidence from facts and figures? + +Filter 5 - Disprove + +How can the business get killed? If the company could kill one of its competitors, who would it be and why? If the company would go away for 5 years which competitor would they bet on and why? How resistant +is the business to adversity? Assume the company paid out all its equity capital, would it still have any value? Could someone with the access to billions of dollars and talent, successfully compete with the +company? How much damage could a competitor do if he doesn't care about returns? Recession sensitivity? Execution risk? Will new technology help or hurt? + +Filter 6 - What are the consequences ifl'm wrong? + +296 + +- SOURCE NOTES - + +Introduction + +Page + +11 "I think that I am... " Francis Darwin (editor), [3mThe Autobiography of Charles Darwin and Selected Letters, [0mDover Publications, New York, 1958, p.55. + +Part One + +Page + +4 "The brain is the... " Gerald Edelman, [3mBrainMatters, [0mThe NeuroSciences Institute, Fall 2000. + +7 "although in some sense... " Ralph Greenspan, [3mPerception, Selection and the Brain, [0mJournal of Neuroaesthetics, July, 2004. + +7 "Isaac Newton might have... " Ralph Greenspan, [3mNature Reviews, [0mVolume 2, May 2001, p.386. + +18 "In no sense... " Ra!ph Greenspan, [3mPerception, Selection and the Brain, [0mJournal ofNeuroaesthetics, July, 2004. + +21 "Why should a man... " Charles Darwin, 1871, [3mThe decent of man, and selecion in relation to sex. [0mLondon: John Murray, 1st edition. Volume 1. Chapter IV (On The Manner of Development of Man from Some Lower +Form). [3mFrom The Complete Work of Charles Darwin Online, [0mUniversity of Cambridge, Cambridge. http://darwin-online.org.uk/ + +21 "powerful stimulus... " Charles Darwin, 1871, [3mThe decent of man, and selecion in relation to sex. [0mLondon: John Murray, 1st edition. Volume 1. Chapter V (On the Development of the Intellectual and Moral +Faculties During Primeval and Civilised Times). [3mFrom The Complete Work of Charles Darwin Online, [0mUniversity of Cambridge, Cambridge. http:/ /darwin-online.org.ukl + +23 "At the moment ... " Charles Darwin, 1871, [3mThe decent of man, and selecion in relation to sex. [0mLondon: John Murray, 1st edition. Volume 1. Chapter III (Comparison of the Mental Powers of Man and the Lower +Animals). [3mFrom The Complete Work of Charles Darwin Online, [0mUniversity of Cambridge, Cambridge. http://darwin-online.org.uk/ + +"At a small dinner gathering... " Lee Alan Dugatkin, [3mCheating Monkeys and Citizen Bees: The Nature of Cooperation in Animals and Humans, [0mThe Free Press, Simon & Schuster Inc., New York, 1999, p.101. + +"Fear of disapproval is... " 59 words, p. 77 from [3mThe Ostrich Factor: Our Population Myopia, [0mby Hardin Garrett (1999). By permission of Oxford University Press, Inc. + +Part Two + +Page + +45 "If the laws of... " 31 words, p. 61 from [3mThe Ostrich Factor: Our Population Myopia, [0mby Hardin Garrett (1999). By permission of Oxford University Press, Inc. + +88 "His [Jones] masterstroke was... " Robert Cialdini, [3mInfluence: The Psychology of Persuasion, [0mQuill + +William Morrow and Company Inc, New York, 1984,1993, p.156. + +88 "In a country like... " Robert Cialdini, [3mInfluence: The Psychology of Persuasion, [0mQuill William Morrow and Company Inc, New York, 1984,1993, p.154. + +88 "Have the courage... " Benjamin Graham, [3mThe Intelligent Investor: A Book of Practical Counsel, [0mHarper & Row, Publishers, New York, 1973, Fourth Revised Edition, p.287. + +297 + +Part Three + +Page + +125 "A complex system... " Gerald Edelman, BrainMatters, The NeuroSciences Institute, Fall 2002. + +132 ''As a colony grows... " 63 words, pp. 266-267 from Living Within Limits: Ecology, Economics, and Population Taboos by Hardin Garrett (1995). By permission of Oxford University Press, Inc. + +152 "It is said to be... " Henry Howard Harper, The Psychology of Speculation: The Human Element in Stock Market Speculations, Fraser Publishing Company, Burlington, Vermont, 1966, p.44. + +Part Four + +Page + +193 "If, in some cataclysm, all... ", Richard Feynman & Robert Leighton & Matthew Sands The Feynman Lectures on Physics, Addison-Wesley Publishing Company, Reading, Massachusetts, 1963, Sixth printing, 1977, +p.1.2. Copyright by California Institute ofTechnology. + +199 "See that bird?... " Richard Feynman, "What is Science?", The Physics Teacher, Vol. 7, Issue 6, pp.313-320, 1969. + +199 "There is a picture... " Richard Feynman, "What is Science?", The Physics Teacher, Vol. 7, Issue 6, pp.313-320, 1969. + +200 "the soles of your... " Richard Feynman, "What is Science?", The Physics Teacher, Vol. 7, Issue 6, + +pp.313-320, 1969. + +200 "Without using the... " Richard Feynman, "What is Science?", The Physics Teacher, Vol. 7, Issue 6, pp.313-320, 1969. + +203 "If earnings not paid... " John Burr Williams, The Theory of Investment Value, Fraser Publishing + +Company, Burlington, 1997 and originally published in 1938 by Harvard University Press, pp.57-58. + +212 "You can't believe... " Noel Tichy and Ram Charan, "Speed, Simplicy, Self-Confidence: An + +Interview with Jack Welch," Harvard Business Review, September-October 1989, p.112. + +217 "In nearly every detective... " Albert Einstein & Leopold Infeld, The Evolution of Physics: The Growth of Ideas from Early Concepts to Relativity and Quanta, Cambridge University Press, Cambridge, 1938, +Reprinted 1978, p.4. + +228 "In the department... " Claude Frederic Bastiat, That Which ls Seen, and That Which Is Not Seen, + +http:/ /bastiat.org/ + +239 "It does not make any... " Richard Feynman, The Character of Physical Law, The Modern Library, Random House, Inc., New York, 1965, 1994 Modern Library Edition, p.150. + +239 "About thirty years ago... " Charles Darwin to Henry Fawcett (18 September 1861), Letter No. 133 in Francis Darwin (editor), More Letters of Charles Darwin, Vol. 1 D. Appleton, New York, 1903. + +242 "I had also... " Francis Darwin (editor), The Autobiography of Charles Darwin and Selected Letters, + +Dover Publications Inc, Mineola, New York, 1958, pp.45,52-53. + +252 "Why do we complain ... " Seneca Lucius Annaeus, On the Shortness of Life, translated by John + +W. Basore, Loeb Classical Library London, William Heineman, 1932, from The Forum Romanum, The Corpus Scriptorum Latinorum + +256 "I rejoice that... " Francis Darwin (editor), The Autobiography of Charles Darwin and Selected Letters, Dover Publications Inc., Mineola, New York, 1958, pp.46,279. + +Source notes - Charles Munger and Warren Buffett Introduction + +Page + +"All I want to... " Berkshire Hathaway Inc., 1996 Annual Report, p.9. + +"I believe in the... " Lecture by CharlesT. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.63. + +298 + +111 "I chink it's a huge... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.63. + +Part One + +18 "There was a great... " Berkshire Hathaway annual meeting, 2004, Outstanding Investor Digest, + +December 31, 2004, p.32. + +"It's ego. It's greed... " Adam Smith's Money Game, Transcript #105, Air Date: May 15, 1998. + +"I always look at. .. " Buffett &Gates on Success, KCTS/Seatcle, May 1998 transcript p. 4. + +Part Two + +Page + +39 "I came to the... " Andrew Kilpatrick, Of Permanent Value: The Story of Warren Buffett, + +Birmingham: AKPE, 2000, p.873. + +39 "If you want co... " Berkshire Hathaway annual meeting, 1991, Outstanding Investor Digest, May 24, 1991, p.32. + +"We only give... " Berkshire Hathaway annual meeting, 1995, Outstanding Investor Digest, + +August 10, 1995, p.4. + +"The iron rule of nature... " Wesco Financial annual meeting, 2001. + +"The worst abuses ... " Wesco Financial annual meeting, 1994, Outstanding Investor Digest, June 23, 1994, p.15. + +"In the New York... Wesco Financial annual meeting, 2004, Outstanding Investor Digest, + +December 31, 2004, p.45. + +"From all business... " Lecture by Charles T. Munger to the students of Professor Guilford Babcock at the University of Southern California School of Business on April 14, 1994, Outstanding Investor Digest, +May 5, 1995, p.59. + +"The food value... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, December 29, 1997, p.27. + +"Well, che customer. .. " Lecture by Charles T. Munger to che students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, December 29, 1997, p.29. + +"As you occupy some... " Wesco Financial Inc., 1990 Annual Report, (Berkshire Hathaway Inc., + +Letters to Shareholders, 1987-1995, p.203.) + +"Goals should be... " Berkshire Hathaway Inc., 1996 Annual Report, p.l 0. + +"lc's very hard to change... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor Digest, September 24, 1998, p.55. + +"An example of a... " Berkshire Hathaway annual meeting, 1993, Outstanding Investor Digest, + +June 30, 1993, p.29. + +"without the help of... " Berkshire Hathaway Inc., Letters to Shareholders, 1994, p.149. + +"All commissioned salesmen ... " Wesco Financial annual meeting, 1988, Outstanding Investor Digest, April 30, 1988, p.21. + +"They were paid... " Wesco Financial annual meeting, 1992, Outstanding Investor Digest, June + +22, 1992, p.8. + +"Mark Twain used to say... " Berkshire Hathaway annual meeting, 1995, Outstanding Investor Digest, August 10, 1995, p.11. + +52 "I have no use... " Berkshire Hathaway annual meeting, 1995, Andrew Kilpatrick, Of Permanent + +Value: The Story ofWarren Buffett, Birmingham: AKPE, 2000, p.l 074. + +"I do not understand... " Berkshire Hathaway annual meeting, 1994, Outstanding Investor Digest, June 23, 1994, pp.23-24. + +"When they make... " Berkshire Hathaway Inc., Letters to Shareholders, 1989, p.60. + +53 "I would say that... " Berkshire Hathaway annual meeting, 2002. + +"I'd say chat... " Berkshire Hathaway annual meeting, 2001, Outstanding Investor Digest, Year End 2001 Edition, p.24. + +299 + +"We want the manager... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor Digest, September 24, 1998, pp.55-56. + +"Any investor can ... " Berkshire Hathaway Inc., 1997 Annual Report, p.3. + +"Arco was celebrating ... " Wesco Financial annual meeting, 2004, Outstanding Investor Digest, + +December 31, 2004, p.51. + +"Well if you stop... " The Psychology of Human Misjudgment, Talk at the Cambridge Center for Behavioral Studies, April 24, 1995. + +'Tm not saying that... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor Digest, + +September 24, 1998, p.54. + +58 "It is remarkable... " Wesco Financial Inc., 1989 Annual Report, (Berkshire Hathaway Inc., Letters to Shareholders, 1987-1995, p.196.) + +58 "We won't do anything... " Lecture at Stanford Law School, March 23, 1990, Outstanding Investor Digest, April 18, 1990, p.14. + +"What the human being... " Berkshire Hathaway annual meeting, 2002. + +"We do have a... " Berkshire Hathaway Inc., Letters to Shareholders, 1995, p.162. + +"We have very much... " Wesco Financial annual meeting, 1989, Outstanding Investor Digest, + +July 26, 1989, pp.6-7. + +"I chink it was... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor Digest, + +September 24, 1998, p.40. + +65 "Heavy ideology is... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.47. + +"We've done a... " Berkshire Hathaway annual meeting, 2000, Outstanding Investor Digest, Year + +End 2000 Edition, p.60. + +"The most important. .. " Berkshire Hathaway Inc., Letters to Shareholders, 1990, p.74. + +66 "Berkshire extracted a... " Wesco Financial annual meeting, 1989, Outstanding Investor Digest, + +July 26, 1989, p.9. + +"Charlie and I believe... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor Digest, September 24, 1998, p.40. + +"(A) You're facing deprival. .. " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.53. + +"The deprival super-reaction... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.52. + +"One reason why... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.52. + +"Buffett: A very important ... " Berkshire Hathaway annual meeting, 1995, Outstanding Investor Digest, August 10, 1995, p.6. + +"In Captain Cook's... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.50. + +72 "Predicting rain... " Berkshire Hathaway Inc., 2001 Annual Report, p.9. + +72 "It rook Noah... " Berkshire Hathaway annual meeting, 1991, Outstanding Investor Digest, May 24, 1991,p.31. + +75 "In my generation ... " The Psychology of Human Misjudgment, Talk at the Cambridge Center for Behavioral Studies, April 24, 1995. + +75 "One of the problems... " 1994 Lecture ofThe E. J. Faulkner Lecture Series, A Colloquium with University of Nebraska-Lincoln Students by Warren E. Buffett, p.21. + +80 "Three quarters of..." 1994 Lecture ofThe E. J. Faulkner Lecture Series, A Colloquium with University of Nebraska-Lincoln Students by Warren E. Buffett, pp.15-16. + +84 ''As happens in... " Berkshire Hathaway Inc., Letters to Shareholders, 1989, p.59. + +"This friend, who ran... " Berkshire Hathaway Inc., Letters to Shareholders, 1995, p.148. + +"Most managers have very... " Berkshire Hathaway Inc., Letters to Shareholders, 1984, p.96. + +85 "Grown-up people... " Wesco Financial annual meeting, 1995, Outstanding Investor Digest, + +300 + +August 10, 1995, p. 62. + +"We derive no comfort ... " Letter to partners, January 18, 1965. + +"Techniques shrouded in... " Berkshire Hathaway Inc., Letters to Shareholders, 1987, p.12. + +92 "Around here... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor Digest, + +September 24, 1998, p.49. + +"His rule for all... " Lecture by Charles T. Munger to the students of Professor Guilford Babcock at the University of Southern California School of Business on April 14, 1994, Outstanding Investor Digest, +May 5, 1995, p.50. + +"You can't really... " Lecture by Charles T. Munger to the students of Professor Guilford Babcock + +at the University of Southern California School of Business on April 14, 1994, Outstanding Investor Digest, May 5, 1995, p.49. + +99 "The sad fact... " Berkshire Hathaway Inc., Letters to Shareholders, 1994, pp.147-148. + +"We hear a great... " Berkshire Hathaway Inc., Letters to Shareholders, 1979, pp.20-21. + +"We've got great... " Wesco Financial annual meeting, 2000, Outstanding Investor Digest, + +December 18, 2000, p.60. + +100 "There's no use... " Berkshire Hathaway Inc., Letters to Shareholders, 1993, p.129. + +104 "I have no stress... " Berkshire Hathaway annual meeting, 2001, Outstanding Investor Digest, Year End 2001 Edition, p.46. + +I 04 "All the businesses... " Warren Buffett interview, Outstanding Investor Digest, June 23, 1989, p.12. + +105 "When you get two... " Berkshire Hathaway annual meeting, 1991, Outstanding Investor Digest, + +May 24, 1991, p.32. + +105 "A very significant... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, pp.51-52. + +106 "The psychological... " Berkshire Hathaway annual meeting, 1993, Outstanding Investor Digest, + +June 30, 1993, p.32. + +"When people meet. .. " Berkshire Hathaway annual meeting, 2005, Outstanding Investor Digest, + +March 9, 2006, p.55. + +"Buffett: When certain boards... " Berkshire Hathaway annual meeting 1993, Outstanding Investor Digest, June 30, 1993, p.31. + +"willingness to... " Berkshire Hathaway Inc., 2003 Annual Report, p.9. + +108 "In addition ... " Berkshire Hathaway Inc., 2003 Annual Report, p.10. + +108 "The correct system... " Berkshire Hathaway annual meeting, 2005, Outstanding Investor Digest, + +March 9, 2006, p. 56. + +112 "I don't want to... " Lecture by Charles T. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.55. + +113 "I've gotten so that... " Lecture by Charles T. Munger to the students of Professor Guilford Babcock at the University of Southern California School of Business on April 14, 1994, Outstanding Investor +Digest, May 5, 1995, p.51. + +113 "Take all the main ... " Lecture by CharlesT. Munger to the students of Professor William Lazier at Stanford Law School, Outstanding Investor Digest, March 13, 1998, pp.48-49. + +114 "One of the things... " Wesco Financial annual meeting, 1998, Outstanding Investor Digest, + +December 29, 1998, pp.46-47. + +Part Three + +Page + +120 "They had all... " Wesco Financial annual meeting, 2001, Wesco Special Report, Outstanding Investor Digest, OID.COM Edition, 2003, p.10. + +121 "An excess of what ... " Charles T. Munger, speech at Miramar Sheraton Hotel, Santa Monica, CA, on October 14, 1998 to a meeting of the Foundation Financial Officer Group, Outstanding Investor Digest, +1998 Bonus Edition. p.2. + +301 + +125 + +'Tm all for fixing... " Wesco Financial annual meeting, 1998, Outstanding Investor Digest, March + +13, 1998, p.57. + +126 + +"We try and predict..." Wesco Financial annual meeting, 2001, Wesco Special Report, + +Outstanding Investor Digest, OID.COM Edition, 2003, p.l. + +127 + +"We believe the... " Berkshire Hathaway Inc., 1996 Annual Report, p.9. + +127 + +"Economics involves too... " Academic Economics: Strengths and Faults After Considering + +Interdisciplinary Needs, Herb Key Undergraduate Lecture, University of California, Santa Barbara, + +Economics Department, October 3, 2003, http://www.tilsonfimds.com/MungerUCSBspeech.pd£ + +131 + +"The proposal should... " Berkshire Hathaway Inc., 2004 Annual Report, p.8. + +132 + +"Both we and our... " Berkshire Hathaway Inc., 2001 Annual Report, p.14. + +132 + +"In some businesses... " Lecture by Charles T. Munger to the students of Professor Guilford + +Babcock at the University of Southern California School of Business on April 14, 1994, + +Outstanding Investor Digest, May 5, 1995, pp.52-54 + +134 + +"It is not necessary..." Berkshire Hathaway Inc., Letters to Shareholders, 1994, p.147. + +137 + +"For years it was... " Lecture by Charles T. Munger to the students of Professor William Lazier + +at Stanford Law School, Outstanding Investor Digest, March 13, 1998, p.48. + +145 + +"Catastrophe insurers... " Berkshire Hathaway Inc., Letters to Shareholders, 1992, p.113. + +146 + +"Even if perfection... " Berkshire Hathaway Inc., 1996 Annual Report, p.9. + +146 + +"Given the risks... " Berkshire Hathaway Inc., Letters to Shareholders, 1994, p.153. + +146 + +"We do, though,... " Berkshire Hathaway Inc., Letters to Shareholders, 1995, p.169. + +146 + +"In setting prices and... " Berkshire Hathaway Inc., 2001 Annual Report, p.8. + +147 + +"No one knows... " Berkshire Hathaway Inc., 2001 Annual Report, p.8. + +157 + +"Here were 16 extremely... " Berkshire Hathaway annual meeting, 1999, Outstanding Investor + +Digest, December 31, 1999, pp.55-56. + +160 + +"How many of these... " Berkshire Hathaway annual meeting, 1999, Outstanding Investor Digest, + +December 10, 1999, p.56. + +160 + +"You may consciously... " Berkshire Hathaway Inc., Letters to Shareholders, 1993, p.136. + +160 + +"We expect all... " Berkshire Hathaway Inc., 2000 Annual Report, p.7. + +169 + +"If you're going... " The Psychology of Human Misjudgment, Talk at the Cambridge Center for + +Behavioral Studies, April 24, 1995. + +176 + +"People like to look... " Berkshire Hathaway annual meeting, 1989, Outstanding Investor Digest, + +June 23, 1989, p.9. + +176 + +"Conditions relating to... " Berkshire Hathaway annual meeting, 1992, Outstanding Investor + +Digest, June 22, 1992, p.45. + +176 + +"The same mistake... " Berkshire Hathaway Inc., Letters to Shareholders, 1988, p.23. + +177 + +"The water system... " Wesco Financial annual meeting, 1990, Outstanding Investor Digest, June + +28, 1990, pp.20-21. + +179 + +"It is assumed by... " Wesco Financial Inc., 1989 Annual Report, (Berkshire Hathaway Inc., + +Letters to Shareholders, 1987-1995, p.193.) + +185 + +"You rend to forget. .. " Wesco Financial annual meeting, 1998, Outstanding Investor Digest, + +December 29, 1998, p.50. + +185 + +"Triumphs are trumpeted ... " Berkshire Hathaway Inc., 2000 Annual Report, p. 10. + +185 + +"Managers rend to... " Berkshire Hathaway annual meeting, 1999, Outstanding Investor Digest, + +December 31, 1999, p.60. + +185 + +"Berkshire is basically... " Berkshire Hathaway annual meeting, 1994, Outstanding Investor + +Digest, June 23, 1994, p. 31. + +Part Four + +Page + +189 "If you ask not... " Wesco Financial annual meeting 1999, Outstanding Investor Digest, December 31, 1999, p.37. + +302 + +190 + +"If you get... " Lecture by Charles T. Munger to the students of Professor William Lazier at + +190 + +Stanford Law School, [3mOutstanding Investor Digest, [0mDecember 29, 1997, p. 25. + +"Disney is an... " Lecture by Charles T. Munger to the students of Professor William Lazier at + +191 + +Stanford Law School, [3mOutstanding Investor Digest, [0mMarch 13, 1998, pp.55-56. + +'The models that come... " Lecture by Charles T. Munger to the students of Professor Guilford + +Babcock at the University of Southern California School of Business on April 14, 1994, + +191 + +Outstanding Investor Digest, May 5, 1995, pp.50-51. + +"In most messy human... " Wesco Financial annual meeting, 2000, [3mOutstanding Investor Digest, [0m191 + +December 18, 2000, p.52. + +"Suppose you want... " Lecture by Charles T. Munger to the students of Professor William Lazier + +192 + +at Stanford Law School, [3mOutstanding Investor Digest, [0mDecember 29, 1997, p.26. + +"If you don't... " Wesco Financial annual meeting 1999, [3mOutstanding Investor Digest, [0mDecember + +192 + +31, 1999,p.40. + +"Have a full kit... "Academic Economics: Strengths and Faults After Considering Interdisciplinary + +192 + +Needs, Herb Key Undergraduate Lecture, University of California, Santa Barbara, Economics Department, October 3, 2003, http://www.tilsonfunds.com/MungerUCSBspeech.pd£ + +"You get [3mlollapalooza ... " [0mLecture by Charles T. Munger to the students of Professor William + +Lazier at Stanford Law School, [3mOutstanding Investor Digest, [0mDecember 29, 1997, p.25. + +199 + +"Bad terminology is... " Berkshire Hathaway Inc., 2001 [3mAnnual Report, [0mp.10. + +201 + +"We use the... " Berkshire Hathaway annual meeting, 1997, [3mOutstanding Investor Digest, [0mAugust + +202 + +8, 1997, p.18. + +"In the end... " Berkshire Hathaway annual meeting, 2001, [3mOutstanding Investor Digest, [0mYear End + +202 + +2001 Edition, p.37. + +'These numbers routinely... " Berkshire Hathaway Inc., [3mLetters to Shareholders, [0m1986, p.142. + +202 + +"When companies or... " Berkshire Hathaway Inc., 2001 [3mAnnual Report, [0mp.10. + +203 + +"Trumpeting EBITDA... " Berkshire Hathaway Inc., 2002 [3mAnnual Report, [0mp.21. + +203 + +"If somebody's reinvesting... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor + +203 + +Digest, September 24, 1998, p.36. + +"Intrinsic value is an... " Berkshire Hathaway Inc.2001 Annual Report, [3mAn Owner's Manual, [0mp.67. + +204 + +"Using precise numbers... " Berkshire Hathaway Inc., 2000 [3mAnnual Report, [0mp.13. + +204 + +"What you're trying to... " Berkshire Hathaway annual meeting, 2002. + +204 + +"Growth can destroy... " Berkshire Hathaway Inc., 2000 [3mAnnual Report, [0mp.13. + +204 + +"First, we try to... " Berkshire Hathaway Inc., [3mLetters to Shareholders, [0m1992, p.117. + +205 + +"We try... to keep... " Berkshire Hathaway Inc., 2000 [3mAnnual Report, [0mp.14. + +205 + +"take all of the... " Berkshire Hathaway annual meeting, 2004, [3mOutstanding Investor Digest, [0m205 + +December 31, 2004, p.34. + +"If we're trying... " Berkshire Hathaway annual meeting, 2004, Outstanding Investor Digest, + +205 + +December 31, 2004, p.34. + +"You'd try to ... " Berkshire Hathaway annual meeting, 1994, [3mOutstanding Investor Digest, [0mJune + +205 + +23, 1994, p.26. + +"For our discount ... " Berkshire Hathaway annual meeting, 1996, [3mOutstanding Investor Digest, [0m206 + +August 8, 1996, p.28. + +"And that discount... " Berkshire Hathaway annual meeting, 1998, [3mOutstanding Investor Digest, [0m206 + +September 24, 1998, p.36. + +"We love owning... " Berkshire Hathaway Inc., 2002 [3mAnnual Report, [0mp.16. + +206 + +"We believe that... " Berkshire Hathaway annual meeting, 1995, [3mOutstanding Investor Digest, [0m206 + +August 10, 1995, p.12. + +"We are very inexact. .. " Berkshire Hathaway annual meeting, 1990, [3mOutstanding Investor Digest, [0m206 + +May 31, 1990,p.25. + +"When we look... " Berkshire Hathaway annual meeting, 1998, [3mOutstanding Investor Digest, [0mSeptember 24, 1998, p.37. + +303 + +208 + +"If you and I..." Berkshire Hathaway annual meeting, 1999, Outstanding Investor Digest, + +December 10, 1999, p.48. + +208 + +"I would say... " Berkshire Hathaway annual meeting, 2005, Outstanding Investor Digest, March + +209 + +9, 2006, p.60. + +"One friend of mine... " 1994 Lecture ofThe E. J. Faulkner Lecture Series, A Colloquium with + +University of Nebraska-Lincoln Students by Warren E. Buffett, p.6. + +209 + +"My conclusion from... " Berkshire Hathaway Inc., Letters to Shareholders, 1985, p.108. + +212 + +"We have a passion... " Wesco Financial annual meeting, 2002. + +212 + +We haven't succeeded ... " Berkshire Hathaway annual meeting, 2005, Outstanding Investor + +Digest, March 9, 2006, p.62. + +212 + +"If something is... " Berkshire Hathaway annual meeting, 2006. + +212 + +"I generally try... " Berkshire Hathaway annual meeting, 2006. + +213 + +"Charlie and I decided... " Berkshire Hathaway Inc., Letters to Shareholders, 1993, p.134. + +213 + +"Part of that... " Berkshire Hathaway annual meeting, 2004, Outstanding Investor Digest, + +December 31, 2004, p.32. + +213 + +"Yeah, we don't... " Berkshire Hathaway annual meeting, 2004, Outstanding Investor Digest, + +December 31, 2004, p.32. + +213 + +"The harder you... " Wesco Financial annual meeting, 2006. + +214 + +'Tm a follower... " Wesco Financial annual meeting, 2002, Outstanding Investor Digest, + +December 31, 2002, p.38. + +214 + +"There are things... " Wesco Financial annual meeting, 2002, Outstanding Investor Digest, + +December 31, 2002, p.26. + +214 + +"Easy does it. .. " Berkshire Hathaway Inc., Letters to Shareholders, 1989, p.62. + +215 + +"We basically have... " Berkshire Hathaway annual meeting, 1995, Outstanding Investor Digest, + +August 10, 1995, p.20. + +215 + +"I've heard Warren... " Berkshire Hathaway annual meeting, 1997, Outstanding Investor Digest, + +September 24, 1998, p.38. + +215 + +"A... serious problem... " Berkshire Hathaway Inc., 1996 Annual Report, pp.15-16. + +216 + +"I love focused ... " Berkshire Hathaway annual meeting, 1996, Outstanding Investor Digest, + +August 8, 1996, pp.24-25. + +216 + +"There are two questions... " Berkshire Hathaway, press conference, May 2001. + +217 + +"In allocating capital. .. " Berkshire Hathaway Inc., 1998 Annual Report, p.12. + +217 + +"If you feel like... " Berkshire Hathaway annual meeting, 1996, Outstanding Investor Digest, + +August 8, 1996, pp.23-24. + +217 + +"A few major opportunities... " Wesco Financial Inc., 1996 Annual Report, p.6. + +218 + +"Any time anybody... " Lecture by Charles T. Munger to the students of Professor Guilford + +Babcock at the University of Southern California School of Business on April 14, 1994, + +Outstanding Investor Digest, May 5, 1995, p.62. + +218 + +"What counts in this... " Berkshire Hathaway Inc., 2001 Annual Report, pp.7-9. + +219 + +"We really can... " Berkshire Hathaway annual meeting, 1998, Outstanding Investor Digest, + +September 24, 1998, p.48. + +220 + +"Our definition of... " Berkshire Hathaway annual meeting, 2000, Outstanding Investor Digest, + +December 18, 2000, pp.39-40. + +222 + +"Generally speaking... ", Wesco Financial annual meeting, 2002, Outstanding Investor Digest, + +December 31, 2002, p.26. + +225 + +"If you've got two... " Berkshire Hathaway annual meeting, 1997, Outstanding Investor Digest, + +August 8, 1997,p.16. + +227 + +"Look for someone... " Meeting with Warren Buffett May 23, 2005 - University of Maryland + +Student Trek to Omaha. + +228 + +"The key thing... " Berkshire Hathaway annual meeting, 1997, Outstanding Investor Digest, + +August 8, 1997, p.23. + +304 + +228 + +"All of the advantages... " Lecture by Charles T. Munger to the students of Professor Guilford + +Babcock at the University of Southern California School of Business on April 14, 1994, + +Outstanding Investor Digest, May 5, 1995, p. 56. + +229 + +"Many of our..." Berkshire Hathaway Inc., Letters to Shareholders, 1985, p.108. + +230 + +"If you're a captain ... " Lecture by Charles T. Munger to the students of Professor William Lazier + +at Stanford Law School, Outstanding Investor Digest, March 13, 1998, pp.60-61. + +231 + +"You've got a ... "Academic Economics: Strengths and Faults After Considering Interdisciplinary + +Needs, Herb Key Undergraduate Lecture, University of California, Santa Barbara, Economics + +Department, October 3, 2003, http:/ /www.tilsonfunds.com/MungerUCSBspeech.pdf. + +232 + +"Leaving the question... " Berkshire Hathaway Inc., Letters to Shareholders, 1992, p.116. + +232 + +"While an increase ... " Berkshire Hathaway Inc., Letters to Shareholders, 1985, p.109. + +232 + +"return on beginning... " Berkshire Hathaway Inc., Letters to Shareholders, 1980, p.27. + +233 + +"Over the long term... " Lecture by Charles T. Munger to the students of Professor Guilford + +Babcock at the University of Southern California School of Business on April 14, 1994, + +Outstanding Investor Digest, May 5, 1995, p.61. + +233 + +"Examine the record... " Berkshire Hathaway Inc., 2000 Annual Report, p.18. + +233 + +"Finally, be suspicious ... " Berkshire Hathaway Inc., 2002 Annual Report, p.21. + +234 + +"A few years ago... " Berkshire Hathaway Inc., Letters to Shareholders, 1991, pp.94-95. + +235 + +"Ofone thing, however. .. " Berkshire Hathaway Inc., 1997 Annual Report, p.15. + +237 + +"When we buy a stock... " Berkshire Hathaway annual meeting, 2000, Outstanding Investor + +Digest, December 18, 2000, pp.34-35. + +237 + +"Value is destroyed ... " Berkshire Hathaway Inc., 2000 Annual Report, p.14. + +237 + +"There's plenty of magic..." Berkshire Hathaway annual meeting 1993, Outstanding Investor + +Digest, June 30, 1993, p.37. + +240 + +"... you have to have... " Wesco Financial annual meeting, 1998, Outstanding Investor Digest, + +December 29, 1998, p.47. + +240 + +"The best judgment. .. " Warren Buffett from a speech at the Emory Business School as reported + +243 + +in, "Track record is everything", Across the Board, October 1991, p.59. + +'The mental habit of... " Lecture by Charles T. Munger to the students of Professor William + +Lazier at Stanford Law School, Outstanding Investor Digest, December 29, 1997, pp.24. + +244 + +"A lot of success... " Wesco Financial annual meeting, 2000, Outstanding Investor Digest, + +244 + +December 18, 2000, p.60. + +"If you were hired... " Lecture by Charles T. Munger to the students of Professor William Lazier + +at Stanford Law School, Outstanding Investor Digest, December 29, 1997, p.24. + +245 + +"Let's say you have... " Lecture by Charles T. Munger to the students of Professor William Lazier + +at Stanford Law School, Outstanding Investor Digest, March 13, 1998, pp.51-52. + +248 + +"The simple fact. .. " Robert Lenzner and David S. Fondiller, "The not-so-silent partner," Forbes + +Magazine, January 22, 1996, p.83. + +248 + +"When we look at... " Berkshire Hathaway annual meeting, 2000, Outstanding Investor Digest, + +December 18, 2000, p.43. + +249 + +"the best way... " Berkshire Hathaway annual meeting, 2004, Outstanding Investor Digest, + +December 31, 2004, p.32. + +249 + +"In stocks, we expect. .. " Berkshire Hathaway Inc., 2002 Annual Report, p.16. + +249 + +"I had a relative... " Wesco Financial annual meeting, 2002, Outstanding Investor Digest, + +December 31, 2002, p.28. + +250 + +"If we can't... " Berkshire Hathaway Inc., 1996 Annual Report, p.9. + +250 + +"We try to arrange... " Wesco Financial annual meeting, 2002, Outstanding Investor Digest, + +December 31, 2002, p.33. + +251 + +"If you understand... " Berkshire Hathaway annual meeting, 1997, Outstanding Investor Digest, + +August 8, 1997, p.17. + +251 + +"Charlie drummed in... " Janet Lowe, Damn Right: Behind the Scenes with Berkshire Hathaway + +305 + +253 + +Billionaire Charlie Munger, John Wiley & Sons, New York, 2000, p.54. + +"You have to stick... " Berkshire Hathaway annual meeting, 1993, [3mOutstanding Investor Digest, [0mJune 30, 1993, p.24. + +253 + +"We'd rather deal... " Lecture by Charles T. Munger to the students of Professor William Lazier + +at Stanford Law School, [3mOutstanding Investor Digest, [0mMarch 13, 1998, p.55. + +254 + +"If you tell... " Wesco Financial annual meeting, 2004, [3mOutstanding Investor Digest, [0mDecember + +31, 2004, p.42. + +254 + +"More often we've... " Wesco Financial annual meeting, 2004, [3mOutstanding Investor Digest, [0mDecember 31, 2004, p.42. + +254 + +"We think there... " Wesco Financial annual meeting, 2004, [3mOutstanding Investor Digest, [0mDecember 31, 2004, p.42. + +255 + +"Good character is... " Berkshire Hathaway annual meeting, 1993, [3mOutstanding Investor Digest, [0mJune 30, 1993, p.29. + +255 + +''A person who... " Wesco Financial annual meeting, 2006 + +255 + +"You don't want... " Berkshire Hathaway annual meeting, 2005, [3mOutstanding Investor Digest, [0mMarch 9, 2006, p.61. + +255 + +"One of the things... " Berkshire Hathaway annual meeting, 2005, [3mOutstanding Investor Digest, [0mMarch 9, 2006, p.61 + +255 + +"I think the best... " Wesco Financial annual meeting, 2004, [3mOutstanding Investor Digest, [0mDecember 31, 2004, p.50. + +256 + +'The only way... " Berkshire Hathaway annual meeting, 2003 + +257 + +"I do think enthusiasm ... " Buffett & Gates on Success, KCTS/Seattle, May 1998 transcript p. 20. + +257 + +"Do what turns..." Speech to University of Nevada students, 2006 + +257 + +"Don't look for... " Speech to University of Tennessee students, 2006 + +257 + +"Whenever you think... " Wesco Financial annual meeting, 2001, Wesco Special Report, + +Outstanding Investor Digest, OID.COM Edition, 2003, p.20. + +306 + +- BIBLIOGRAPHY - + +Adams John, Risk, UCL Press, London, 1995 + +Allison Graham & Zelikow Philip, Essence Of Decision: Explaining the Cuban Missile Crisis, Addison- Wesley Educational Publishers, New York, 1999 + +Aronson Elliot, The Social Animal, W:H. 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Various characteristics of each ebook are listed to aid in +selecting the preferred file. Click on any of the filenumbers below to +quickly view each ebook. + +┏━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓ ┃ +1228 │ 1859, First Edition ┃ +┠───────┼─────────────────────────────────────────────────────────┨ ┃ +22764 │ 1860, Second Edition ┃ +┠───────┼─────────────────────────────────────────────────────────┨ ┃ +2009 │ 1872, Sixth Edition, considered the definitive edition. ┃ ┗━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛ -On -the Origin of Species +On the Origin of Species BY MEANS OF NATURAL SELECTION, -OR THE -PRESERVATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE. +OR THE PRESERVATION OF FAVOURED RACES IN THE STRUGGLE FOR LIFE. By Charles Darwin, M.A., -Fellow Of The Royal, Geological, Linnæan, Etc., Societies; -Author Of ‘Journal Of Researches During H.M.S. Beagle’s Voyage Round The -World.’ +Fellow Of The Royal, Geological, Linnæan, Etc., Societies; Author Of +‘Journal Of Researches During H.M.S. Beagle’s Voyage Round The World.’ -LONDON: -JOHN MURRAY, ALBEMARLE STREET. -1859. +LONDON: JOHN MURRAY, ALBEMARLE STREET. 1859. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ -“But with regard to the material world, we can at least go so far as this—we -can perceive that events are brought about not by insulated interpositions of -Divine power, exerted in each particular case, but by the establishment of -general laws.” +“But with regard to the material world, we can at least go so far as +this—we can perceive that events are brought about not by insulated +interpositions of Divine power, exerted in each particular case, but by +the establishment of general laws.” W. WHEWELL: Bridgewater Treatise. -“To conclude, therefore, let no man out of a weak conceit of sobriety, or an -ill-applied moderation, think or maintain, that a man can search too far or be -too well studied in the book of God’s word, or in the book of God’s works; -divinity or philosophy; but rather let men endeavour an endless progress or -proficience in both.” +“To conclude, therefore, let no man out of a weak conceit of sobriety, +or an ill-applied moderation, think or maintain, that a man can search +too far or be too well studied in the book of God’s word, or in the book +of God’s works; divinity or philosophy; but rather let men endeavour an +endless progress or proficience in both.” BACON: Advancement of Learning. -Down, Bromley, Kent, - October, 1st, 1859. +Down, Bromley, Kent, October, 1st, 1859. ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ Contents -INTRODUCTION. -1. VARIATION UNDER DOMESTICATION. -2. VARIATION UNDER NATURE. -3. STRUGGLE FOR EXISTENCE. -4. NATURAL SELECTION. -5. LAWS OF VARIATION. -6. DIFFICULTIES ON THEORY. -7. INSTINCT. -8. HYBRIDISM. -9. ON THE IMPERFECTION OF THE GEOLOGICAL RECORD. -10. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS. -11. GEOGRAPHICAL DISTRIBUTION. -12. GEOGRAPHICAL DISTRIBUTION—continued. -13. MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY: -14. RECAPITULATION AND CONCLUSION. -INDEX +INTRODUCTION. 1. VARIATION UNDER DOMESTICATION. 2. VARIATION UNDER +NATURE. 3. STRUGGLE FOR EXISTENCE. 4. NATURAL SELECTION. 5. LAWS OF +VARIATION. 6. DIFFICULTIES ON THEORY. 7. INSTINCT. 8. HYBRIDISM. 9. +ON THE IMPERFECTION OF THE GEOLOGICAL RECORD. 10. ON THE GEOLOGICAL +SUCCESSION OF ORGANIC BEINGS. 11. GEOGRAPHICAL DISTRIBUTION. 12. +GEOGRAPHICAL DISTRIBUTION—continued. 13. MUTUAL AFFINITIES OF ORGANIC +BEINGS: MORPHOLOGY: 14. RECAPITULATION AND CONCLUSION. INDEX DETEAILED CONTENTS. ON THE ORIGIN OF SPECIES. @@ -80,110 +65,82 @@ INTRODUCTION. CHAPTER I. VARIATION UNDER DOMESTICATION. -Causes of Variability. -Effects of Habit. -Correlation of Growth. -Inheritance. -Character of Domestic Varieties. -Difficulty of distinguishing between Varieties and Species. -Origin of Domestic Varieties from one or more Species. -Domestic Pigeons, their Differences and Origin. -Principle of Selection anciently followed, its Effects. -Methodical and Unconscious Selection. -Unknown Origin of our Domestic Productions. -Circumstances favourable to Man’s power of Selection. +Causes of Variability. Effects of Habit. Correlation of Growth. +Inheritance. Character of Domestic Varieties. Difficulty of +distinguishing between Varieties and Species. Origin of Domestic +Varieties from one or more Species. Domestic Pigeons, their Differences +and Origin. Principle of Selection anciently followed, its Effects. +Methodical and Unconscious Selection. Unknown Origin of our Domestic +Productions. Circumstances favourable to Man’s power of Selection. CHAPTER 2. VARIATION UNDER NATURE. -Variability. -Individual Differences. -Doubtful species. -Wide ranging, much diffused, and common species vary most. -Species of the larger genera in any country vary more than the species of the -smaller genera. -Many of the species of the larger genera resemble varieties in being very -closely, but unequally, related to each other, and in having restricted ranges. +Variability. Individual Differences. Doubtful species. Wide ranging, +much diffused, and common species vary most. Species of the larger +genera in any country vary more than the species of the smaller genera. +Many of the species of the larger genera resemble varieties in being +very closely, but unequally, related to each other, and in having +restricted ranges. CHAPTER 3. STRUGGLE FOR EXISTENCE. -Bears on natural selection. -The term used in a wide sense. -Geometrical powers of increase. -Rapid increase of naturalised animals and plants. -Nature of the checks to increase. -Competition universal. -Effects of climate. -Protection from the number of individuals. -Complex relations of all animals and plants throughout nature. -Struggle for life most severe between individuals and varieties of the same -species; often severe between species of the same genus. -The relation of organism to organism the most important of all relations. +Bears on natural selection. The term used in a wide sense. Geometrical +powers of increase. Rapid increase of naturalised animals and plants. +Nature of the checks to increase. Competition universal. Effects of +climate. Protection from the number of individuals. Complex relations +of all animals and plants throughout nature. Struggle for life most +severe between individuals and varieties of the same species; often +severe between species of the same genus. The relation of organism to +organism the most important of all relations. CHAPTER 4. NATURAL SELECTION. Natural Selection: its power compared with man’s selection, its power on -characters of trifling importance, its power at all ages and on both sexes. -Sexual Selection. -On the generality of intercrosses between individuals of the same species. -Circumstances favourable and unfavourable to Natural Selection, -namely, intercrossing, isolation, number of individuals. -Slow action. -Extinction caused by Natural Selection. -Divergence of Character, related to the diversity of inhabitants of any small -area, and to naturalisation. -Action of Natural Selection, through Divergence of Character and -Extinction, on the descendants from a common parent. -Explains the Grouping of all organic beings. +characters of trifling importance, its power at all ages and on both +sexes. Sexual Selection. On the generality of intercrosses between +individuals of the same species. Circumstances favourable and +unfavourable to Natural Selection, namely, intercrossing, isolation, +number of individuals. Slow action. Extinction caused by Natural +Selection. Divergence of Character, related to the diversity of +inhabitants of any small area, and to naturalisation. Action of Natural +Selection, through Divergence of Character and Extinction, on the +descendants from a common parent. Explains the Grouping of all organic +beings. CHAPTER 5. LAWS OF VARIATION. -Effects of external conditions. -Use and disuse, combined with natural selection; organs of flight and of -vision. -Acclimatisation. -Correlation of growth. -Compensation and economy of growth. -False correlations. -Multiple, rudimentary, and lowly organised structures variable. -Parts developed in an unusual manner are highly variable: specific characters -more variable than generic: secondary sexual characters variable. -Species of the same genus vary in an analogous manner. -Reversions to long-lost characters. -Summary. +Effects of external conditions. Use and disuse, combined with natural +selection; organs of flight and of vision. Acclimatisation. +Correlation of growth. Compensation and economy of growth. False +correlations. Multiple, rudimentary, and lowly organised structures +variable. Parts developed in an unusual manner are highly variable: +specific characters more variable than generic: secondary sexual +characters variable. Species of the same genus vary in an analogous +manner. Reversions to long-lost characters. Summary. CHAPTER 6. DIFFICULTIES ON THEORY. -Difficulties on the theory of descent with modification. -Transitions. -Absence or rarity of transitional varieties. -Transitions in habits of life. -Diversified habits in the same species. -Species with habits widely different from those of their allies. -Organs of extreme perfection. -Means of transition. -Cases of difficulty. -Natura non facit saltum. -Organs of small importance. -Organs not in all cases absolutely perfect. -The law of Unity of Type and of the Conditions of Existence embraced by the -theory of Natural Selection. +Difficulties on the theory of descent with modification. Transitions. +Absence or rarity of transitional varieties. Transitions in habits of +life. Diversified habits in the same species. Species with habits +widely different from those of their allies. Organs of extreme +perfection. Means of transition. Cases of difficulty. Natura non +facit saltum. Organs of small importance. Organs not in all cases +absolutely perfect. The law of Unity of Type and of the Conditions of +Existence embraced by the theory of Natural Selection. CHAPTER 7. INSTINCT. Instincts comparable with habits, but different in their origin. -Instincts graduated. -Aphides and ants. -Instincts variable. -Domestic instincts, their origin. -Natural instincts of the cuckoo, ostrich, and parasitic bees. -Slave-making ants. -Hive-bee, its cell-making instinct. +Instincts graduated. Aphides and ants. Instincts variable. Domestic +instincts, their origin. Natural instincts of the cuckoo, ostrich, and +parasitic bees. Slave-making ants. Hive-bee, its cell-making instinct. Difficulties on the theory of the Natural Selection of instincts. Neuter or sterile insects. @@ -192,64 +149,54 @@ Summary. CHAPTER 8. HYBRIDISM. Distinction between the sterility of first crosses and of hybrids. -Sterility various in degree, not universal, affected by close interbreeding, -removed by domestication. -Laws governing the sterility of hybrids. -Sterility not a special endowment, but incidental on other differences. -Causes of the sterility of first crosses and of hybrids. -Parallelism between the effects of changed conditions of life and crossing. -Fertility of varieties when crossed and of their mongrel offspring not -universal. -Hybrids and mongrels compared independently of their fertility. -Summary. +Sterility various in degree, not universal, affected by close +interbreeding, removed by domestication. Laws governing the sterility +of hybrids. Sterility not a special endowment, but incidental on other +differences. Causes of the sterility of first crosses and of hybrids. +Parallelism between the effects of changed conditions of life and +crossing. Fertility of varieties when crossed and of their mongrel +offspring not universal. Hybrids and mongrels compared independently of +their fertility. Summary. CHAPTER 9. ON THE IMPERFECTION OF THE GEOLOGICAL RECORD. -On the absence of intermediate varieties at the present day. -On the nature of extinct intermediate varieties; on their number. -On the vast lapse of time, as inferred from the rate of deposition and of -denudation. -On the poorness of our palæontological collections. -On the intermittence of geological formations. -On the absence of intermediate varieties in any one formation. -On the sudden appearance of groups of species. -On their sudden appearance in the lowest known fossiliferous strata. +On the absence of intermediate varieties at the present day. On the +nature of extinct intermediate varieties; on their number. On the vast +lapse of time, as inferred from the rate of deposition and of +denudation. On the poorness of our palæontological collections. On the +intermittence of geological formations. On the absence of intermediate +varieties in any one formation. On the sudden appearance of groups of +species. On their sudden appearance in the lowest known fossiliferous +strata. CHAPTER 10. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS. -On the slow and successive appearance of new species. -On their different rates of change. -Species once lost do not reappear. -Groups of species follow the same general rules in their appearance and -disappearance as do single species. -On Extinction. -On simultaneous changes in the forms of life throughout the world. -On the affinities of extinct species to each other and to living species. -On the state of development of ancient forms. -On the succession of the same types within the same areas. -Summary of preceding and present chapters. +On the slow and successive appearance of new species. On their +different rates of change. Species once lost do not reappear. Groups +of species follow the same general rules in their appearance and +disappearance as do single species. On Extinction. On simultaneous +changes in the forms of life throughout the world. On the affinities of +extinct species to each other and to living species. On the state of +development of ancient forms. On the succession of the same types +within the same areas. Summary of preceding and present chapters. CHAPTER 11. GEOGRAPHICAL DISTRIBUTION. Present distribution cannot be accounted for by differences in physical -conditions. -Importance of barriers. -Affinity of the productions of the same continent. -Centres of creation. -Means of dispersal, by changes of climate and of the level of the land, and by -occasional means. +conditions. Importance of barriers. Affinity of the productions of the +same continent. Centres of creation. Means of dispersal, by changes of +climate and of the level of the land, and by occasional means. Dispersal during the Glacial period co-extensive with the world. CHAPTER 12. GEOGRAPHICAL DISTRIBUTION—continued. -Distribution of fresh-water productions. -On the inhabitants of oceanic islands. -Absence of Batrachians and of terrestrial Mammals. -On the relation of the inhabitants of islands to those of the nearest mainland. +Distribution of fresh-water productions. On the inhabitants of oceanic +islands. Absence of Batrachians and of terrestrial Mammals. On the +relation of the inhabitants of islands to those of the nearest mainland. On colonisation from the nearest source with subsequent modification. Summary of the last and present chapters. @@ -257,12706 +204,13851 @@ Summary of the last and present chapters. CHAPTER 13. MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY: EMBRYOLOGY: RUDIMENTARY ORGANS. -CLASSIFICATION, groups subordinate to groups. -Natural system. -Rules and difficulties in classification, explained on the theory of descent -with modification. -Classification of varieties. -Descent always used in classification. -Analogical or adaptive characters. -Affinities, general, complex and radiating. -Extinction separates and defines groups. -MORPHOLOGY, between members of the same class, between parts of the same -individual. -EMBRYOLOGY, laws of, explained by variations not supervening at an early age, -and being inherited at a corresponding age. -RUDIMENTARY ORGANS; their origin explained. -Summary. +CLASSIFICATION, groups subordinate to groups. Natural system. Rules +and difficulties in classification, explained on the theory of descent +with modification. Classification of varieties. Descent always used in +classification. Analogical or adaptive characters. Affinities, +general, complex and radiating. Extinction separates and defines +groups. MORPHOLOGY, between members of the same class, between parts of +the same individual. EMBRYOLOGY, laws of, explained by variations not +supervening at an early age, and being inherited at a corresponding age. +RUDIMENTARY ORGANS; their origin explained. Summary. CHAPTER 14. RECAPITULATION AND CONCLUSION. Recapitulation of the difficulties on the theory of Natural Selection. Recapitulation of the general and special circumstances in its favour. -Causes of the general belief in the immutability of species. -How far the theory of natural selection may be extended. -Effects of its adoption on the study of Natural history. -Concluding remarks. +Causes of the general belief in the immutability of species. How far +the theory of natural selection may be extended. Effects of its +adoption on the study of Natural history. Concluding remarks. ON THE ORIGIN OF SPECIES. INTRODUCTION. -When on board H.M.S. ‘Beagle,’ as naturalist, I was much struck with certain -facts in the distribution of the inhabitants of South America, and in the -geological relations of the present to the past inhabitants of that continent. -These facts seemed to me to throw some light on the origin of species—that -mystery of mysteries, as it has been called by one of our greatest -philosophers. On my return home, it occurred to me, in 1837, that something -might perhaps be made out on this question by patiently accumulating and -reflecting on all sorts of facts which could possibly have any bearing on it. -After five years’ work I allowed myself to speculate on the subject, and drew -up some short notes; these I enlarged in 1844 into a sketch of the conclusions, -which then seemed to me probable: from that period to the present day I have -steadily pursued the same object. I hope that I may be excused for entering on -these personal details, as I give them to show that I have not been hasty in -coming to a decision. - -My work is now nearly finished; but as it will take me two or three more years -to complete it, and as my health is far from strong, I have been urged to -publish this Abstract. I have more especially been induced to do this, as Mr. -Wallace, who is now studying the natural history of the Malay archipelago, has -arrived at almost exactly the same general conclusions that I have on the -origin of species. Last year he sent to me a memoir on this subject, with a -request that I would forward it to Sir Charles Lyell, who sent it to the -Linnean Society, and it is published in the third volume of the Journal of that -Society. Sir C. Lyell and Dr. Hooker, who both knew of my work—the latter -having read my sketch of 1844—honoured me by thinking it advisable to publish, -with Mr. Wallace’s excellent memoir, some brief extracts from my manuscripts. - -This Abstract, which I now publish, must necessarily be imperfect. I cannot -here give references and authorities for my several statements; and I must -trust to the reader reposing some confidence in my accuracy. No doubt errors -will have crept in, though I hope I have always been cautious in trusting to -good authorities alone. I can here give only the general conclusions at which I -have arrived, with a few facts in illustration, but which, I hope, in most -cases will suffice. No one can feel more sensible than I do of the necessity of -hereafter publishing in detail all the facts, with references, on which my -conclusions have been grounded; and I hope in a future work to do this. For I -am well aware that scarcely a single point is discussed in this volume on which -facts cannot be adduced, often apparently leading to conclusions directly -opposite to those at which I have arrived. A fair result can be obtained only -by fully stating and balancing the facts and arguments on both sides of each -question; and this cannot possibly be here done. +When on board H.M.S. ‘Beagle,’ as naturalist, I was much struck with +certain facts in the distribution of the inhabitants of South America, +and in the geological relations of the present to the past inhabitants +of that continent. These facts seemed to me to throw some light on the +origin of species—that mystery of mysteries, as it has been called by +one of our greatest philosophers. On my return home, it occurred to me, +in 1837, that something might perhaps be made out on this question by +patiently accumulating and reflecting on all sorts of facts which could +possibly have any bearing on it. After five years’ work I allowed +myself to speculate on the subject, and drew up some short notes; these +I enlarged in 1844 into a sketch of the conclusions, which then seemed +to me probable: from that period to the present day I have steadily +pursued the same object. I hope that I may be excused for entering on +these personal details, as I give them to show that I have not been +hasty in coming to a decision. + +My work is now nearly finished; but as it will take me two or three more +years to complete it, and as my health is far from strong, I have been +urged to publish this Abstract. I have more especially been induced to +do this, as Mr. Wallace, who is now studying the natural history of the +Malay archipelago, has arrived at almost exactly the same general +conclusions that I have on the origin of species. Last year he sent to +me a memoir on this subject, with a request that I would forward it to +Sir Charles Lyell, who sent it to the Linnean Society, and it is +published in the third volume of the Journal of that Society. Sir C. +Lyell and Dr. Hooker, who both knew of my work—the latter having read my +sketch of 1844—honoured me by thinking it advisable to publish, with Mr. +Wallace’s excellent memoir, some brief extracts from my manuscripts. + +This Abstract, which I now publish, must necessarily be imperfect. I +cannot here give references and authorities for my several statements; +and I must trust to the reader reposing some confidence in my accuracy. +No doubt errors will have crept in, though I hope I have always been +cautious in trusting to good authorities alone. I can here give only the +general conclusions at which I have arrived, with a few facts in +illustration, but which, I hope, in most cases will suffice. No one can +feel more sensible than I do of the necessity of hereafter publishing in +detail all the facts, with references, on which my conclusions have been +grounded; and I hope in a future work to do this. For I am well aware +that scarcely a single point is discussed in this volume on which facts +cannot be adduced, often apparently leading to conclusions directly +opposite to those at which I have arrived. A fair result can be obtained +only by fully stating and balancing the facts and arguments on both +sides of each question; and this cannot possibly be here done. I much regret that want of space prevents my having the satisfaction of -acknowledging the generous assistance which I have received from very many -naturalists, some of them personally unknown to me. I cannot, however, let this -opportunity pass without expressing my deep obligations to Dr. Hooker, who for -the last fifteen years has aided me in every possible way by his large stores -of knowledge and his excellent judgment. +acknowledging the generous assistance which I have received from very +many naturalists, some of them personally unknown to me. I cannot, +however, let this opportunity pass without expressing my deep +obligations to Dr. Hooker, who for the last fifteen years has aided me +in every possible way by his large stores of knowledge and his excellent +judgment. In considering the Origin of Species, it is quite conceivable that a -naturalist, reflecting on the mutual affinities of organic beings, on their -embryological relations, their geographical distribution, geological -succession, and other such facts, might come to the conclusion that each -species had not been independently created, but had descended, like varieties, -from other species. Nevertheless, such a conclusion, even if well founded, -would be unsatisfactory, until it could be shown how the innumerable species -inhabiting this world have been modified, so as to acquire that perfection of -structure and coadaptation which most justly excites our admiration. -Naturalists continually refer to external conditions, such as climate, food, -etc., as the only possible cause of variation. In one very limited sense, as we -shall hereafter see, this may be true; but it is preposterous to attribute to -mere external conditions, the structure, for instance, of the woodpecker, with -its feet, tail, beak, and tongue, so admirably adapted to catch insects under -the bark of trees. In the case of the misseltoe, which draws its nourishment -from certain trees, which has seeds that must be transported by certain birds, -and which has flowers with separate sexes absolutely requiring the agency of -certain insects to bring pollen from one flower to the other, it is equally -preposterous to account for the structure of this parasite, with its relations -to several distinct organic beings, by the effects of external conditions, or -of habit, or of the volition of the plant itself. - -The author of the ‘Vestiges of Creation’ would, I presume, say that, after a -certain unknown number of generations, some bird had given birth to a -woodpecker, and some plant to the misseltoe, and that these had been produced -perfect as we now see them; but this assumption seems to me to be no -explanation, for it leaves the case of the coadaptations of organic beings to -each other and to their physical conditions of life, untouched and unexplained. - -It is, therefore, of the highest importance to gain a clear insight into the -means of modification and coadaptation. At the commencement of my observations -it seemed to me probable that a careful study of domesticated animals and of -cultivated plants would offer the best chance of making out this obscure -problem. Nor have I been disappointed; in this and in all other perplexing -cases I have invariably found that our knowledge, imperfect though it be, of -variation under domestication, afforded the best and safest clue. I may venture -to express my conviction of the high value of such studies, although they have -been very commonly neglected by naturalists. - -From these considerations, I shall devote the first chapter of this Abstract to -Variation under Domestication. We shall thus see that a large amount of -hereditary modification is at least possible, and, what is equally or more -important, we shall see how great is the power of man in accumulating by his -Selection successive slight variations. I will then pass on to the variability -of species in a state of nature; but I shall, unfortunately, be compelled to -treat this subject far too briefly, as it can be treated properly only by -giving long catalogues of facts. We shall, however, be enabled to discuss what -circumstances are most favourable to variation. In the next chapter the -Struggle for Existence amongst all organic beings throughout the world, which -inevitably follows from their high geometrical powers of increase, will be -treated of. This is the doctrine of Malthus, applied to the whole animal and -vegetable kingdoms. As many more individuals of each species are born than can -possibly survive; and as, consequently, there is a frequently recurring -struggle for existence, it follows that any being, if it vary however slightly -in any manner profitable to itself, under the complex and sometimes varying -conditions of life, will have a better chance of surviving, and thus be -naturally selected. From the strong principle of inheritance, any selected -variety will tend to propagate its new and modified form. - -This fundamental subject of Natural Selection will be treated at some length in -the fourth chapter; and we shall then see how Natural Selection almost -inevitably causes much Extinction of the less improved forms of life and -induces what I have called Divergence of Character. In the next chapter I shall -discuss the complex and little known laws of variation and of correlation of -growth. In the four succeeding chapters, the most apparent and gravest -difficulties on the theory will be given: namely, first, the difficulties of -transitions, or in understanding how a simple being or a simple organ can be -changed and perfected into a highly developed being or elaborately constructed -organ; secondly the subject of Instinct, or the mental powers of animals, -thirdly, Hybridism, or the infertility of species and the fertility of -varieties when intercrossed; and fourthly, the imperfection of the Geological -Record. In the next chapter I shall consider the geological succession of -organic beings throughout time; in the eleventh and twelfth, their geographical -distribution throughout space; in the thirteenth, their classification or -mutual affinities, both when mature and in an embryonic condition. In the last -chapter I shall give a brief recapitulation of the whole work, and a few -concluding remarks. - -No one ought to feel surprise at much remaining as yet unexplained in regard to -the origin of species and varieties, if he makes due allowance for our profound -ignorance in regard to the mutual relations of all the beings which live around -us. Who can explain why one species ranges widely and is very numerous, and why -another allied species has a narrow range and is rare? Yet these relations are -of the highest importance, for they determine the present welfare, and, as I -believe, the future success and modification of every inhabitant of this world. -Still less do we know of the mutual relations of the innumerable inhabitants of -the world during the many past geological epochs in its history. Although much -remains obscure, and will long remain obscure, I can entertain no doubt, after -the most deliberate study and dispassionate judgment of which I am capable, -that the view which most naturalists entertain, and which I formerly -entertained—namely, that each species has been independently created—is -erroneous. I am fully convinced that species are not immutable; but that those -belonging to what are called the same genera are lineal descendants of some -other and generally extinct species, in the same manner as the acknowledged -varieties of any one species are the descendants of that species. Furthermore, -I am convinced that Natural Selection has been the main but not exclusive means -of modification. - -CHAPTER I. -VARIATION UNDER DOMESTICATION. - -Causes of Variability. Effects of Habit. Correlation of Growth. Inheritance. -Character of Domestic Varieties. Difficulty of distinguishing between Varieties -and Species. Origin of Domestic Varieties from one or more Species. Domestic -Pigeons, their Differences and Origin. Principle of Selection anciently -followed, its Effects. Methodical and Unconscious Selection. Unknown Origin of -our Domestic Productions. Circumstances favourable to Man’s power of Selection. - -When we look to the individuals of the same variety or sub-variety of our older -cultivated plants and animals, one of the first points which strikes us, is, -that they generally differ much more from each other, than do the individuals -of any one species or variety in a state of nature. When we reflect on the vast -diversity of the plants and animals which have been cultivated, and which have -varied during all ages under the most different climates and treatment, I think -we are driven to conclude that this greater variability is simply due to our -domestic productions having been raised under conditions of life not so uniform -as, and somewhat different from, those to which the parent-species have been -exposed under nature. There is, also, I think, some probability in the view -propounded by Andrew Knight, that this variability may be partly connected with -excess of food. It seems pretty clear that organic beings must be exposed -during several generations to the new conditions of life to cause any -appreciable amount of variation; and that when the organisation has once begun -to vary, it generally continues to vary for many generations. No case is on -record of a variable being ceasing to be variable under cultivation. Our oldest -cultivated plants, such as wheat, still often yield new varieties: our oldest -domesticated animals are still capable of rapid improvement or modification. - -It has been disputed at what period of life the causes of variability, whatever -they may be, generally act; whether during the early or late period of -development of the embryo, or at the instant of conception. Geoffroy St. -Hilaire’s experiments show that unnatural treatment of the embryo causes -monstrosities; and monstrosities cannot be separated by any clear line of -distinction from mere variations. But I am strongly inclined to suspect that -the most frequent cause of variability may be attributed to the male and female -reproductive elements having been affected prior to the act of conception. -Several reasons make me believe in this; but the chief one is the remarkable -effect which confinement or cultivation has on the functions of the -reproductive system; this system appearing to be far more susceptible than any -other part of the organisation, to the action of any change in the conditions -of life. Nothing is more easy than to tame an animal, and few things more -difficult than to get it to breed freely under confinement, even in the many -cases when the male and female unite. How many animals there are which will not -breed, though living long under not very close confinement in their native -country! This is generally attributed to vitiated instincts; but how many -cultivated plants display the utmost vigour, and yet rarely or never seed! In -some few such cases it has been found out that very trifling changes, such as a -little more or less water at some particular period of growth, will determine -whether or not the plant sets a seed. I cannot here enter on the copious -details which I have collected on this curious subject; but to show how -singular the laws are which determine the reproduction of animals under -confinement, I may just mention that carnivorous animals, even from the -tropics, breed in this country pretty freely under confinement, with the -exception of the plantigrades or bear family; whereas, carnivorous birds, with -the rarest exceptions, hardly ever lay fertile eggs. Many exotic plants have -pollen utterly worthless, in the same exact condition as in the most sterile -hybrids. When, on the one hand, we see domesticated animals and plants, though -often weak and sickly, yet breeding quite freely under confinement; and when, -on the other hand, we see individuals, though taken young from a state of -nature, perfectly tamed, long-lived, and healthy (of which I could give -numerous instances), yet having their reproductive system so seriously affected -by unperceived causes as to fail in acting, we need not be surprised at this -system, when it does act under confinement, acting not quite regularly, and -producing offspring not perfectly like their parents or variable. - -Sterility has been said to be the bane of horticulture; but on this view we owe -variability to the same cause which produces sterility; and variability is the -source of all the choicest productions of the garden. I may add, that as some -organisms will breed most freely under the most unnatural conditions (for -instance, the rabbit and ferret kept in hutches), showing that their -reproductive system has not been thus affected; so will some animals and plants -withstand domestication or cultivation, and vary very slightly—perhaps hardly -more than in a state of nature. - -A long list could easily be given of “sporting plants;” by this term gardeners -mean a single bud or offset, which suddenly assumes a new and sometimes very -different character from that of the rest of the plant. Such buds can be -propagated by grafting, etc., and sometimes by seed. These “sports” are -extremely rare under nature, but far from rare under cultivation; and in this -case we see that the treatment of the parent has affected a bud or offset, and -not the ovules or pollen. But it is the opinion of most physiologists that -there is no essential difference between a bud and an ovule in their earliest -stages of formation; so that, in fact, “sports” support my view, that -variability may be largely attributed to the ovules or pollen, or to both, -having been affected by the treatment of the parent prior to the act of -conception. These cases anyhow show that variation is not necessarily -connected, as some authors have supposed, with the act of generation. - -Seedlings from the same fruit, and the young of the same litter, sometimes -differ considerably from each other, though both the young and the parents, as -Müller has remarked, have apparently been exposed to exactly the same -conditions of life; and this shows how unimportant the direct effects of the -conditions of life are in comparison with the laws of reproduction, and of -growth, and of inheritance; for had the action of the conditions been direct, -if any of the young had varied, all would probably have varied in the same -manner. To judge how much, in the case of any variation, we should attribute to -the direct action of heat, moisture, light, food, etc., is most difficult: my -impression is, that with animals such agencies have produced very little direct -effect, though apparently more in the case of plants. Under this point of view, -Mr. Buckman’s recent experiments on plants seem extremely valuable. When all or -nearly all the individuals exposed to certain conditions are affected in the -same way, the change at first appears to be directly due to such conditions; -but in some cases it can be shown that quite opposite conditions produce -similar changes of structure. Nevertheless some slight amount of change may, I -think, be attributed to the direct action of the conditions of life—as, in some -cases, increased size from amount of food, colour from particular kinds of food -and from light, and perhaps the thickness of fur from climate. - -Habit also has a decided influence, as in the period of flowering with plants -when transported from one climate to another. In animals it has a more marked -effect; for instance, I find in the domestic duck that the bones of the wing -weigh less and the bones of the leg more, in proportion to the whole skeleton, -than do the same bones in the wild-duck; and I presume that this change may be -safely attributed to the domestic duck flying much less, and walking more, than -its wild parent. The great and inherited development of the udders in cows and -goats in countries where they are habitually milked, in comparison with the -state of these organs in other countries, is another instance of the effect of -use. Not a single domestic animal can be named which has not in some country -drooping ears; and the view suggested by some authors, that the drooping is due -to the disuse of the muscles of the ear, from the animals not being much -alarmed by danger, seems probable. - -There are many laws regulating variation, some few of which can be dimly seen, -and will be hereafter briefly mentioned. I will here only allude to what may be -called correlation of growth. Any change in the embryo or larva will almost -certainly entail changes in the mature animal. In monstrosities, the -correlations between quite distinct parts are very curious; and many instances -are given in Isidore Geoffroy St. Hilaire’s great work on this subject. -Breeders believe that long limbs are almost always accompanied by an elongated -head. Some instances of correlation are quite whimsical; thus cats with blue -eyes are invariably deaf; colour and constitutional peculiarities go together, -of which many remarkable cases could be given amongst animals and plants. From -the facts collected by Heusinger, it appears that white sheep and pigs are -differently affected from coloured individuals by certain vegetable poisons. -Hairless dogs have imperfect teeth; long-haired and coarse-haired animals are -apt to have, as is asserted, long or many horns; pigeons with feathered feet -have skin between their outer toes; pigeons with short beaks have small feet, -and those with long beaks large feet. Hence, if man goes on selecting, and thus -augmenting, any peculiarity, he will almost certainly unconsciously modify -other parts of the structure, owing to the mysterious laws of the correlation -of growth. - -The result of the various, quite unknown, or dimly seen laws of variation is -infinitely complex and diversified. It is well worth while carefully to study -the several treatises published on some of our old cultivated plants, as on the -hyacinth, potato, even the dahlia, etc.; and it is really surprising to note -the endless points in structure and constitution in which the varieties and -sub-varieties differ slightly from each other. The whole organisation seems to -have become plastic, and tends to depart in some small degree from that of the -parental type. - -Any variation which is not inherited is unimportant for us. But the number and -diversity of inheritable deviations of structure, both those of slight and -those of considerable physiological importance, is endless. Dr. Prosper Lucas’s -treatise, in two large volumes, is the fullest and the best on this subject. No -breeder doubts how strong is the tendency to inheritance: like produces like is -his fundamental belief: doubts have been thrown on this principle by -theoretical writers alone. When a deviation appears not unfrequently, and we -see it in the father and child, we cannot tell whether it may not be due to the -same original cause acting on both; but when amongst individuals, apparently +naturalist, reflecting on the mutual affinities of organic beings, on +their embryological relations, their geographical distribution, +geological succession, and other such facts, might come to the +conclusion that each species had not been independently created, but had +descended, like varieties, from other species. Nevertheless, such a +conclusion, even if well founded, would be unsatisfactory, until it +could be shown how the innumerable species inhabiting this world have +been modified, so as to acquire that perfection of structure and +coadaptation which most justly excites our admiration. Naturalists +continually refer to external conditions, such as climate, food, etc., +as the only possible cause of variation. In one very limited sense, as +we shall hereafter see, this may be true; but it is preposterous to +attribute to mere external conditions, the structure, for instance, of +the woodpecker, with its feet, tail, beak, and tongue, so admirably +adapted to catch insects under the bark of trees. In the case of the +misseltoe, which draws its nourishment from certain trees, which has +seeds that must be transported by certain birds, and which has flowers +with separate sexes absolutely requiring the agency of certain insects +to bring pollen from one flower to the other, it is equally preposterous +to account for the structure of this parasite, with its relations to +several distinct organic beings, by the effects of external conditions, +or of habit, or of the volition of the plant itself. + +The author of the ‘Vestiges of Creation’ would, I presume, say that, +after a certain unknown number of generations, some bird had given birth +to a woodpecker, and some plant to the misseltoe, and that these had +been produced perfect as we now see them; but this assumption seems to +me to be no explanation, for it leaves the case of the coadaptations of +organic beings to each other and to their physical conditions of life, +untouched and unexplained. + +It is, therefore, of the highest importance to gain a clear insight into +the means of modification and coadaptation. At the commencement of my +observations it seemed to me probable that a careful study of +domesticated animals and of cultivated plants would offer the best +chance of making out this obscure problem. Nor have I been disappointed; +in this and in all other perplexing cases I have invariably found that +our knowledge, imperfect though it be, of variation under domestication, +afforded the best and safest clue. I may venture to express my +conviction of the high value of such studies, although they have been +very commonly neglected by naturalists. + +From these considerations, I shall devote the first chapter of this +Abstract to Variation under Domestication. We shall thus see that a +large amount of hereditary modification is at least possible, and, what +is equally or more important, we shall see how great is the power of man +in accumulating by his Selection successive slight variations. I will +then pass on to the variability of species in a state of nature; but I +shall, unfortunately, be compelled to treat this subject far too +briefly, as it can be treated properly only by giving long catalogues of +facts. We shall, however, be enabled to discuss what circumstances are +most favourable to variation. In the next chapter the Struggle for +Existence amongst all organic beings throughout the world, which +inevitably follows from their high geometrical powers of increase, will +be treated of. This is the doctrine of Malthus, applied to the whole +animal and vegetable kingdoms. As many more individuals of each species +are born than can possibly survive; and as, consequently, there is a +frequently recurring struggle for existence, it follows that any being, +if it vary however slightly in any manner profitable to itself, under +the complex and sometimes varying conditions of life, will have a better +chance of surviving, and thus be naturally selected. From the strong +principle of inheritance, any selected variety will tend to propagate +its new and modified form. + +This fundamental subject of Natural Selection will be treated at some +length in the fourth chapter; and we shall then see how Natural +Selection almost inevitably causes much Extinction of the less improved +forms of life and induces what I have called Divergence of Character. In +the next chapter I shall discuss the complex and little known laws of +variation and of correlation of growth. In the four succeeding chapters, +the most apparent and gravest difficulties on the theory will be given: +namely, first, the difficulties of transitions, or in understanding how +a simple being or a simple organ can be changed and perfected into a +highly developed being or elaborately constructed organ; secondly the +subject of Instinct, or the mental powers of animals, thirdly, +Hybridism, or the infertility of species and the fertility of varieties +when intercrossed; and fourthly, the imperfection of the Geological +Record. In the next chapter I shall consider the geological succession +of organic beings throughout time; in the eleventh and twelfth, their +geographical distribution throughout space; in the thirteenth, their +classification or mutual affinities, both when mature and in an +embryonic condition. In the last chapter I shall give a brief +recapitulation of the whole work, and a few concluding remarks. + +No one ought to feel surprise at much remaining as yet unexplained in +regard to the origin of species and varieties, if he makes due allowance +for our profound ignorance in regard to the mutual relations of all the +beings which live around us. Who can explain why one species ranges +widely and is very numerous, and why another allied species has a narrow +range and is rare? Yet these relations are of the highest importance, +for they determine the present welfare, and, as I believe, the future +success and modification of every inhabitant of this world. Still less +do we know of the mutual relations of the innumerable inhabitants of the +world during the many past geological epochs in its history. Although +much remains obscure, and will long remain obscure, I can entertain no +doubt, after the most deliberate study and dispassionate judgment of +which I am capable, that the view which most naturalists entertain, and +which I formerly entertained—namely, that each species has been +independently created—is erroneous. I am fully convinced that species +are not immutable; but that those belonging to what are called the same +genera are lineal descendants of some other and generally extinct +species, in the same manner as the acknowledged varieties of any one +species are the descendants of that species. Furthermore, I am convinced +that Natural Selection has been the main but not exclusive means of +modification. + +CHAPTER I. VARIATION UNDER DOMESTICATION. + +Causes of Variability. Effects of Habit. Correlation of Growth. +Inheritance. Character of Domestic Varieties. Difficulty of +distinguishing between Varieties and Species. Origin of Domestic +Varieties from one or more Species. Domestic Pigeons, their Differences +and Origin. Principle of Selection anciently followed, its Effects. +Methodical and Unconscious Selection. Unknown Origin of our Domestic +Productions. Circumstances favourable to Man’s power of Selection. + +When we look to the individuals of the same variety or sub-variety of +our older cultivated plants and animals, one of the first points which +strikes us, is, that they generally differ much more from each other, +than do the individuals of any one species or variety in a state of +nature. When we reflect on the vast diversity of the plants and animals +which have been cultivated, and which have varied during all ages under +the most different climates and treatment, I think we are driven to +conclude that this greater variability is simply due to our domestic +productions having been raised under conditions of life not so uniform +as, and somewhat different from, those to which the parent-species have +been exposed under nature. There is, also, I think, some probability in +the view propounded by Andrew Knight, that this variability may be +partly connected with excess of food. It seems pretty clear that organic +beings must be exposed during several generations to the new conditions +of life to cause any appreciable amount of variation; and that when the +organisation has once begun to vary, it generally continues to vary for +many generations. No case is on record of a variable being ceasing to be +variable under cultivation. Our oldest cultivated plants, such as wheat, +still often yield new varieties: our oldest domesticated animals are +still capable of rapid improvement or modification. + +It has been disputed at what period of life the causes of variability, +whatever they may be, generally act; whether during the early or late +period of development of the embryo, or at the instant of conception. +Geoffroy St. Hilaire’s experiments show that unnatural treatment of the +embryo causes monstrosities; and monstrosities cannot be separated by +any clear line of distinction from mere variations. But I am strongly +inclined to suspect that the most frequent cause of variability may be +attributed to the male and female reproductive elements having been +affected prior to the act of conception. Several reasons make me +believe in this; but the chief one is the remarkable effect which +confinement or cultivation has on the functions of the reproductive +system; this system appearing to be far more susceptible than any other +part of the organisation, to the action of any change in the conditions +of life. Nothing is more easy than to tame an animal, and few things +more difficult than to get it to breed freely under confinement, even in +the many cases when the male and female unite. How many animals there +are which will not breed, though living long under not very close +confinement in their native country! This is generally attributed to +vitiated instincts; but how many cultivated plants display the utmost +vigour, and yet rarely or never seed! In some few such cases it has been +found out that very trifling changes, such as a little more or less +water at some particular period of growth, will determine whether or not +the plant sets a seed. I cannot here enter on the copious details which +I have collected on this curious subject; but to show how singular the +laws are which determine the reproduction of animals under confinement, +I may just mention that carnivorous animals, even from the tropics, +breed in this country pretty freely under confinement, with the +exception of the plantigrades or bear family; whereas, carnivorous +birds, with the rarest exceptions, hardly ever lay fertile eggs. Many +exotic plants have pollen utterly worthless, in the same exact condition +as in the most sterile hybrids. When, on the one hand, we see +domesticated animals and plants, though often weak and sickly, yet +breeding quite freely under confinement; and when, on the other hand, we +see individuals, though taken young from a state of nature, perfectly +tamed, long-lived, and healthy (of which I could give numerous +instances), yet having their reproductive system so seriously affected +by unperceived causes as to fail in acting, we need not be surprised at +this system, when it does act under confinement, acting not quite +regularly, and producing offspring not perfectly like their parents or +variable. + +Sterility has been said to be the bane of horticulture; but on this view +we owe variability to the same cause which produces sterility; and +variability is the source of all the choicest productions of the garden. +I may add, that as some organisms will breed most freely under the most +unnatural conditions (for instance, the rabbit and ferret kept in +hutches), showing that their reproductive system has not been thus +affected; so will some animals and plants withstand domestication or +cultivation, and vary very slightly—perhaps hardly more than in a state +of nature. + +A long list could easily be given of “sporting plants;” by this term +gardeners mean a single bud or offset, which suddenly assumes a new and +sometimes very different character from that of the rest of the plant. +Such buds can be propagated by grafting, etc., and sometimes by seed. +These “sports” are extremely rare under nature, but far from rare under +cultivation; and in this case we see that the treatment of the parent +has affected a bud or offset, and not the ovules or pollen. But it is +the opinion of most physiologists that there is no essential difference +between a bud and an ovule in their earliest stages of formation; so +that, in fact, “sports” support my view, that variability may be largely +attributed to the ovules or pollen, or to both, having been affected by +the treatment of the parent prior to the act of conception. These cases +anyhow show that variation is not necessarily connected, as some authors +have supposed, with the act of generation. + +Seedlings from the same fruit, and the young of the same litter, +sometimes differ considerably from each other, though both the young and +the parents, as Müller has remarked, have apparently been exposed to +exactly the same conditions of life; and this shows how unimportant the +direct effects of the conditions of life are in comparison with the laws +of reproduction, and of growth, and of inheritance; for had the action +of the conditions been direct, if any of the young had varied, all would +probably have varied in the same manner. To judge how much, in the case +of any variation, we should attribute to the direct action of heat, +moisture, light, food, etc., is most difficult: my impression is, that +with animals such agencies have produced very little direct effect, +though apparently more in the case of plants. Under this point of view, +Mr. Buckman’s recent experiments on plants seem extremely valuable. When +all or nearly all the individuals exposed to certain conditions are +affected in the same way, the change at first appears to be directly due +to such conditions; but in some cases it can be shown that quite +opposite conditions produce similar changes of structure. Nevertheless +some slight amount of change may, I think, be attributed to the direct +action of the conditions of life—as, in some cases, increased size from +amount of food, colour from particular kinds of food and from light, and +perhaps the thickness of fur from climate. + +Habit also has a decided influence, as in the period of flowering with +plants when transported from one climate to another. In animals it has a +more marked effect; for instance, I find in the domestic duck that the +bones of the wing weigh less and the bones of the leg more, in +proportion to the whole skeleton, than do the same bones in the +wild-duck; and I presume that this change may be safely attributed to +the domestic duck flying much less, and walking more, than its wild +parent. The great and inherited development of the udders in cows and +goats in countries where they are habitually milked, in comparison with +the state of these organs in other countries, is another instance of the +effect of use. Not a single domestic animal can be named which has not +in some country drooping ears; and the view suggested by some authors, +that the drooping is due to the disuse of the muscles of the ear, from +the animals not being much alarmed by danger, seems probable. + +There are many laws regulating variation, some few of which can be dimly +seen, and will be hereafter briefly mentioned. I will here only allude +to what may be called correlation of growth. Any change in the embryo or +larva will almost certainly entail changes in the mature animal. In +monstrosities, the correlations between quite distinct parts are very +curious; and many instances are given in Isidore Geoffroy St. Hilaire’s +great work on this subject. Breeders believe that long limbs are almost +always accompanied by an elongated head. Some instances of correlation +are quite whimsical; thus cats with blue eyes are invariably deaf; +colour and constitutional peculiarities go together, of which many +remarkable cases could be given amongst animals and plants. From the +facts collected by Heusinger, it appears that white sheep and pigs are +differently affected from coloured individuals by certain vegetable +poisons. Hairless dogs have imperfect teeth; long-haired and +coarse-haired animals are apt to have, as is asserted, long or many +horns; pigeons with feathered feet have skin between their outer toes; +pigeons with short beaks have small feet, and those with long beaks +large feet. Hence, if man goes on selecting, and thus augmenting, any +peculiarity, he will almost certainly unconsciously modify other parts +of the structure, owing to the mysterious laws of the correlation of +growth. + +The result of the various, quite unknown, or dimly seen laws of +variation is infinitely complex and diversified. It is well worth while +carefully to study the several treatises published on some of our old +cultivated plants, as on the hyacinth, potato, even the dahlia, etc.; +and it is really surprising to note the endless points in structure and +constitution in which the varieties and sub-varieties differ slightly +from each other. The whole organisation seems to have become plastic, +and tends to depart in some small degree from that of the parental type. + +Any variation which is not inherited is unimportant for us. But the +number and diversity of inheritable deviations of structure, both those +of slight and those of considerable physiological importance, is +endless. Dr. Prosper Lucas’s treatise, in two large volumes, is the +fullest and the best on this subject. No breeder doubts how strong is +the tendency to inheritance: like produces like is his fundamental +belief: doubts have been thrown on this principle by theoretical writers +alone. When a deviation appears not unfrequently, and we see it in the +father and child, we cannot tell whether it may not be due to the same +original cause acting on both; but when amongst individuals, apparently exposed to the same conditions, any very rare deviation, due to some -extraordinary combination of circumstances, appears in the parent—say, once -amongst several million individuals—and it reappears in the child, the mere -doctrine of chances almost compels us to attribute its reappearance to -inheritance. Every one must have heard of cases of albinism, prickly skin, -hairy bodies, etc., appearing in several members of the same family. If strange -and rare deviations of structure are truly inherited, less strange and commoner -deviations may be freely admitted to be inheritable. Perhaps the correct way of -viewing the whole subject, would be, to look at the inheritance of every -character whatever as the rule, and non-inheritance as the anomaly. - -The laws governing inheritance are quite unknown; no one can say why the same -peculiarity in different individuals of the same species, and in individuals of -different species, is sometimes inherited and sometimes not so; why the child -often reverts in certain characters to its grandfather or grandmother or other -much more remote ancestor; why a peculiarity is often transmitted from one sex -to both sexes or to one sex alone, more commonly but not exclusively to the -like sex. It is a fact of some little importance to us, that peculiarities -appearing in the males of our domestic breeds are often transmitted either -exclusively, or in a much greater degree, to males alone. A much more important -rule, which I think may be trusted, is that, at whatever period of life a -peculiarity first appears, it tends to appear in the offspring at a -corresponding age, though sometimes earlier. In many cases this could not be -otherwise: thus the inherited peculiarities in the horns of cattle could appear -only in the offspring when nearly mature; peculiarities in the silkworm are -known to appear at the corresponding caterpillar or cocoon stage. But -hereditary diseases and some other facts make me believe that the rule has a -wider extension, and that when there is no apparent reason why a peculiarity -should appear at any particular age, yet that it does tend to appear in the +extraordinary combination of circumstances, appears in the parent—say, +once amongst several million individuals—and it reappears in the child, +the mere doctrine of chances almost compels us to attribute its +reappearance to inheritance. Every one must have heard of cases of +albinism, prickly skin, hairy bodies, etc., appearing in several members +of the same family. If strange and rare deviations of structure are +truly inherited, less strange and commoner deviations may be freely +admitted to be inheritable. Perhaps the correct way of viewing the whole +subject, would be, to look at the inheritance of every character +whatever as the rule, and non-inheritance as the anomaly. + +The laws governing inheritance are quite unknown; no one can say why the +same peculiarity in different individuals of the same species, and in +individuals of different species, is sometimes inherited and sometimes +not so; why the child often reverts in certain characters to its +grandfather or grandmother or other much more remote ancestor; why a +peculiarity is often transmitted from one sex to both sexes or to one +sex alone, more commonly but not exclusively to the like sex. It is a +fact of some little importance to us, that peculiarities appearing in +the males of our domestic breeds are often transmitted either +exclusively, or in a much greater degree, to males alone. A much more +important rule, which I think may be trusted, is that, at whatever +period of life a peculiarity first appears, it tends to appear in the +offspring at a corresponding age, though sometimes earlier. In many +cases this could not be otherwise: thus the inherited peculiarities in +the horns of cattle could appear only in the offspring when nearly +mature; peculiarities in the silkworm are known to appear at the +corresponding caterpillar or cocoon stage. But hereditary diseases and +some other facts make me believe that the rule has a wider extension, +and that when there is no apparent reason why a peculiarity should +appear at any particular age, yet that it does tend to appear in the offspring at the same period at which it first appeared in the parent. I -believe this rule to be of the highest importance in explaining the laws of -embryology. These remarks are of course confined to the first appearance of the -peculiarity, and not to its primary cause, which may have acted on the ovules -or male element; in nearly the same manner as in the crossed offspring from a -short-horned cow by a long-horned bull, the greater length of horn, though -appearing late in life, is clearly due to the male element. - -Having alluded to the subject of reversion, I may here refer to a statement -often made by naturalists—namely, that our domestic varieties, when run wild, -gradually but certainly revert in character to their aboriginal stocks. Hence -it has been argued that no deductions can be drawn from domestic races to -species in a state of nature. I have in vain endeavoured to discover on what -decisive facts the above statement has so often and so boldly been made. There -would be great difficulty in proving its truth: we may safely conclude that -very many of the most strongly-marked domestic varieties could not possibly -live in a wild state. In many cases we do not know what the aboriginal stock -was, and so could not tell whether or not nearly perfect reversion had ensued. -It would be quite necessary, in order to prevent the effects of intercrossing, -that only a single variety should be turned loose in its new home. -Nevertheless, as our varieties certainly do occasionally revert in some of -their characters to ancestral forms, it seems to me not improbable, that if we -could succeed in naturalising, or were to cultivate, during many generations, -the several races, for instance, of the cabbage, in very poor soil (in which -case, however, some effect would have to be attributed to the direct action of -the poor soil), that they would to a large extent, or even wholly, revert to -the wild aboriginal stock. Whether or not the experiment would succeed, is not -of great importance for our line of argument; for by the experiment itself the -conditions of life are changed. If it could be shown that our domestic -varieties manifested a strong tendency to reversion,—that is, to lose their -acquired characters, whilst kept under unchanged conditions, and whilst kept in -a considerable body, so that free intercrossing might check, by blending -together, any slight deviations of structure, in such case, I grant that we -could deduce nothing from domestic varieties in regard to species. But there is -not a shadow of evidence in favour of this view: to assert that we could not -breed our cart and race-horses, long and short-horned cattle, and poultry of -various breeds, and esculent vegetables, for an almost infinite number of -generations, would be opposed to all experience. I may add, that when under -nature the conditions of life do change, variations and reversions of character -probably do occur; but natural selection, as will hereafter be explained, will -determine how far the new characters thus arising shall be preserved. - -When we look to the hereditary varieties or races of our domestic animals and -plants, and compare them with species closely allied together, we generally -perceive in each domestic race, as already remarked, less uniformity of -character than in true species. Domestic races of the same species, also, often -have a somewhat monstrous character; by which I mean, that, although differing -from each other, and from the other species of the same genus, in several -trifling respects, they often differ in an extreme degree in some one part, -both when compared one with another, and more especially when compared with all -the species in nature to which they are nearest allied. With these exceptions -(and with that of the perfect fertility of varieties when crossed,—a subject -hereafter to be discussed), domestic races of the same species differ from each -other in the same manner as, only in most cases in a lesser degree than, do -closely-allied species of the same genus in a state of nature. I think this -must be admitted, when we find that there are hardly any domestic races, either -amongst animals or plants, which have not been ranked by some competent judges -as mere varieties, and by other competent judges as the descendants of +believe this rule to be of the highest importance in explaining the laws +of embryology. These remarks are of course confined to the first +appearance of the peculiarity, and not to its primary cause, which may +have acted on the ovules or male element; in nearly the same manner as +in the crossed offspring from a short-horned cow by a long-horned bull, +the greater length of horn, though appearing late in life, is clearly +due to the male element. + +Having alluded to the subject of reversion, I may here refer to a +statement often made by naturalists—namely, that our domestic varieties, +when run wild, gradually but certainly revert in character to their +aboriginal stocks. Hence it has been argued that no deductions can be +drawn from domestic races to species in a state of nature. I have in +vain endeavoured to discover on what decisive facts the above statement +has so often and so boldly been made. There would be great difficulty in +proving its truth: we may safely conclude that very many of the most +strongly-marked domestic varieties could not possibly live in a wild +state. In many cases we do not know what the aboriginal stock was, and +so could not tell whether or not nearly perfect reversion had ensued. +It would be quite necessary, in order to prevent the effects of +intercrossing, that only a single variety should be turned loose in its +new home. Nevertheless, as our varieties certainly do occasionally +revert in some of their characters to ancestral forms, it seems to me +not improbable, that if we could succeed in naturalising, or were to +cultivate, during many generations, the several races, for instance, of +the cabbage, in very poor soil (in which case, however, some effect +would have to be attributed to the direct action of the poor soil), that +they would to a large extent, or even wholly, revert to the wild +aboriginal stock. Whether or not the experiment would succeed, is not of +great importance for our line of argument; for by the experiment itself +the conditions of life are changed. If it could be shown that our +domestic varieties manifested a strong tendency to reversion,—that is, +to lose their acquired characters, whilst kept under unchanged +conditions, and whilst kept in a considerable body, so that free +intercrossing might check, by blending together, any slight deviations +of structure, in such case, I grant that we could deduce nothing from +domestic varieties in regard to species. But there is not a shadow of +evidence in favour of this view: to assert that we could not breed our +cart and race-horses, long and short-horned cattle, and poultry of +various breeds, and esculent vegetables, for an almost infinite number +of generations, would be opposed to all experience. I may add, that when +under nature the conditions of life do change, variations and reversions +of character probably do occur; but natural selection, as will hereafter +be explained, will determine how far the new characters thus arising +shall be preserved. + +When we look to the hereditary varieties or races of our domestic +animals and plants, and compare them with species closely allied +together, we generally perceive in each domestic race, as already +remarked, less uniformity of character than in true species. Domestic +races of the same species, also, often have a somewhat monstrous +character; by which I mean, that, although differing from each other, +and from the other species of the same genus, in several trifling +respects, they often differ in an extreme degree in some one part, both +when compared one with another, and more especially when compared with +all the species in nature to which they are nearest allied. With these +exceptions (and with that of the perfect fertility of varieties when +crossed,—a subject hereafter to be discussed), domestic races of the +same species differ from each other in the same manner as, only in most +cases in a lesser degree than, do closely-allied species of the same +genus in a state of nature. I think this must be admitted, when we find +that there are hardly any domestic races, either amongst animals or +plants, which have not been ranked by some competent judges as mere +varieties, and by other competent judges as the descendants of aboriginally distinct species. If any marked distinction existed between -domestic races and species, this source of doubt could not so perpetually -recur. It has often been stated that domestic races do not differ from each -other in characters of generic value. I think it could be shown that this -statement is hardly correct; but naturalists differ most widely in determining -what characters are of generic value; all such valuations being at present -empirical. Moreover, on the view of the origin of genera which I shall -presently give, we have no right to expect often to meet with generic -differences in our domesticated productions. - -When we attempt to estimate the amount of structural difference between the -domestic races of the same species, we are soon involved in doubt, from not -knowing whether they have descended from one or several parent-species. This -point, if it could be cleared up, would be interesting; if, for instance, it -could be shown that the greyhound, bloodhound, terrier, spaniel, and bull-dog, -which we all know propagate their kind so truly, were the offspring of any -single species, then such facts would have great weight in making us doubt -about the immutability of the many very closely allied and natural species—for -instance, of the many foxes—inhabiting different quarters of the world. I do -not believe, as we shall presently see, that all our dogs have descended from -any one wild species; but, in the case of some other domestic races, there is +domestic races and species, this source of doubt could not so +perpetually recur. It has often been stated that domestic races do not +differ from each other in characters of generic value. I think it could +be shown that this statement is hardly correct; but naturalists differ +most widely in determining what characters are of generic value; all +such valuations being at present empirical. Moreover, on the view of the +origin of genera which I shall presently give, we have no right to +expect often to meet with generic differences in our domesticated +productions. + +When we attempt to estimate the amount of structural difference between +the domestic races of the same species, we are soon involved in doubt, +from not knowing whether they have descended from one or several +parent-species. This point, if it could be cleared up, would be +interesting; if, for instance, it could be shown that the greyhound, +bloodhound, terrier, spaniel, and bull-dog, which we all know propagate +their kind so truly, were the offspring of any single species, then such +facts would have great weight in making us doubt about the immutability +of the many very closely allied and natural species—for instance, of the +many foxes—inhabiting different quarters of the world. I do not believe, +as we shall presently see, that all our dogs have descended from any one +wild species; but, in the case of some other domestic races, there is presumptive, or even strong, evidence in favour of this view. -It has often been assumed that man has chosen for domestication animals and -plants having an extraordinary inherent tendency to vary, and likewise to -withstand diverse climates. I do not dispute that these capacities have added -largely to the value of most of our domesticated productions; but how could a -savage possibly know, when he first tamed an animal, whether it would vary in -succeeding generations, and whether it would endure other climates? Has the -little variability of the ass or guinea-fowl, or the small power of endurance -of warmth by the rein-deer, or of cold by the common camel, prevented their -domestication? I cannot doubt that if other animals and plants, equal in number -to our domesticated productions, and belonging to equally diverse classes and -countries, were taken from a state of nature, and could be made to breed for an -equal number of generations under domestication, they would vary on an average -as largely as the parent species of our existing domesticated productions have -varied. - -In the case of most of our anciently domesticated animals and plants, I do not -think it is possible to come to any definite conclusion, whether they have -descended from one or several species. The argument mainly relied on by those -who believe in the multiple origin of our domestic animals is, that we find in -the most ancient records, more especially on the monuments of Egypt, much -diversity in the breeds; and that some of the breeds closely resemble, perhaps -are identical with, those still existing. Even if this latter fact were found -more strictly and generally true than seems to me to be the case, what does it -show, but that some of our breeds originated there, four or five thousand years -ago? But Mr. Horner’s researches have rendered it in some degree probable that -man sufficiently civilized to have manufactured pottery existed in the valley -of the Nile thirteen or fourteen thousand years ago; and who will pretend to -say how long before these ancient periods, savages, like those of Tierra del -Fuego or Australia, who possess a semi-domestic dog, may not have existed in -Egypt? - -The whole subject must, I think, remain vague; nevertheless, I may, without -here entering on any details, state that, from geographical and other -considerations, I think it highly probable that our domestic dogs have -descended from several wild species. In regard to sheep and goats I can form no -opinion. I should think, from facts communicated to me by Mr. Blyth, on the -habits, voice, and constitution, etc., of the humped Indian cattle, that these -had descended from a different aboriginal stock from our European cattle; and -several competent judges believe that these latter have had more than one wild -parent. With respect to horses, from reasons which I cannot give here, I am -doubtfully inclined to believe, in opposition to several authors, that all the -races have descended from one wild stock. Mr. Blyth, whose opinion, from his -large and varied stores of knowledge, I should value more than that of almost -any one, thinks that all the breeds of poultry have proceeded from the common -wild Indian fowl (Gallus bankiva). In regard to ducks and rabbits, the breeds -of which differ considerably from each other in structure, I do not doubt that -they all have descended from the common wild duck and rabbit. +It has often been assumed that man has chosen for domestication animals +and plants having an extraordinary inherent tendency to vary, and +likewise to withstand diverse climates. I do not dispute that these +capacities have added largely to the value of most of our domesticated +productions; but how could a savage possibly know, when he first tamed +an animal, whether it would vary in succeeding generations, and whether +it would endure other climates? Has the little variability of the ass or +guinea-fowl, or the small power of endurance of warmth by the rein-deer, +or of cold by the common camel, prevented their domestication? I cannot +doubt that if other animals and plants, equal in number to our +domesticated productions, and belonging to equally diverse classes and +countries, were taken from a state of nature, and could be made to breed +for an equal number of generations under domestication, they would vary +on an average as largely as the parent species of our existing +domesticated productions have varied. + +In the case of most of our anciently domesticated animals and plants, I +do not think it is possible to come to any definite conclusion, whether +they have descended from one or several species. The argument mainly +relied on by those who believe in the multiple origin of our domestic +animals is, that we find in the most ancient records, more especially on +the monuments of Egypt, much diversity in the breeds; and that some of +the breeds closely resemble, perhaps are identical with, those still +existing. Even if this latter fact were found more strictly and +generally true than seems to me to be the case, what does it show, but +that some of our breeds originated there, four or five thousand years +ago? But Mr. Horner’s researches have rendered it in some degree +probable that man sufficiently civilized to have manufactured pottery +existed in the valley of the Nile thirteen or fourteen thousand years +ago; and who will pretend to say how long before these ancient periods, +savages, like those of Tierra del Fuego or Australia, who possess a +semi-domestic dog, may not have existed in Egypt? + +The whole subject must, I think, remain vague; nevertheless, I may, +without here entering on any details, state that, from geographical and +other considerations, I think it highly probable that our domestic dogs +have descended from several wild species. In regard to sheep and goats I +can form no opinion. I should think, from facts communicated to me by +Mr. Blyth, on the habits, voice, and constitution, etc., of the humped +Indian cattle, that these had descended from a different aboriginal +stock from our European cattle; and several competent judges believe +that these latter have had more than one wild parent. With respect to +horses, from reasons which I cannot give here, I am doubtfully inclined +to believe, in opposition to several authors, that all the races have +descended from one wild stock. Mr. Blyth, whose opinion, from his large +and varied stores of knowledge, I should value more than that of almost +any one, thinks that all the breeds of poultry have proceeded from the +common wild Indian fowl (Gallus bankiva). In regard to ducks and +rabbits, the breeds of which differ considerably from each other in +structure, I do not doubt that they all have descended from the common +wild duck and rabbit. The doctrine of the origin of our several domestic races from several -aboriginal stocks, has been carried to an absurd extreme by some authors. They -believe that every race which breeds true, let the distinctive characters be -ever so slight, has had its wild prototype. At this rate there must have -existed at least a score of species of wild cattle, as many sheep, and several -goats in Europe alone, and several even within Great Britain. One author -believes that there formerly existed in Great Britain eleven wild species of -sheep peculiar to it! When we bear in mind that Britain has now hardly one -peculiar mammal, and France but few distinct from those of Germany and -conversely, and so with Hungary, Spain, etc., but that each of these kingdoms -possesses several peculiar breeds of cattle, sheep, etc., we must admit that -many domestic breeds have originated in Europe; for whence could they have been -derived, as these several countries do not possess a number of peculiar species -as distinct parent-stocks? So it is in India. Even in the case of the domestic -dogs of the whole world, which I fully admit have probably descended from -several wild species, I cannot doubt that there has been an immense amount of -inherited variation. Who can believe that animals closely resembling the -Italian greyhound, the bloodhound, the bull-dog, or Blenheim spaniel, etc.—so -unlike all wild Canidæ—ever existed freely in a state of nature? It has often -been loosely said that all our races of dogs have been produced by the crossing -of a few aboriginal species; but by crossing we can get only forms in some -degree intermediate between their parents; and if we account for our several -domestic races by this process, we must admit the former existence of the most -extreme forms, as the Italian greyhound, bloodhound, bull-dog, etc., in the -wild state. Moreover, the possibility of making distinct races by crossing has -been greatly exaggerated. There can be no doubt that a race may be modified by -occasional crosses, if aided by the careful selection of those individual -mongrels, which present any desired character; but that a race could be -obtained nearly intermediate between two extremely different races or species, -I can hardly believe. Sir J. Sebright expressly experimentised for this object, -and failed. The offspring from the first cross between two pure breeds is -tolerably and sometimes (as I have found with pigeons) extremely uniform, and -everything seems simple enough; but when these mongrels are crossed one with -another for several generations, hardly two of them will be alike, and then the -extreme difficulty, or rather utter hopelessness, of the task becomes apparent. -Certainly, a breed intermediate between two very distinct breeds could not be -got without extreme care and long-continued selection; nor can I find a single -case on record of a permanent race having been thus formed. - -On the Breeds of the Domestic Pigeon.—Believing that it is always best to study -some special group, I have, after deliberation, taken up domestic pigeons. I -have kept every breed which I could purchase or obtain, and have been most -kindly favoured with skins from several quarters of the world, more especially -by the Honourable W. Elliot from India, and by the Honourable C. Murray from -Persia. Many treatises in different languages have been published on pigeons, -and some of them are very important, as being of considerable antiquity. I have -associated with several eminent fanciers, and have been permitted to join two -of the London Pigeon Clubs. The diversity of the breeds is something -astonishing. Compare the English carrier and the short-faced tumbler, and see -the wonderful difference in their beaks, entailing corresponding differences in -their skulls. The carrier, more especially the male bird, is also remarkable -from the wonderful development of the carunculated skin about the head, and -this is accompanied by greatly elongated eyelids, very large external orifices -to the nostrils, and a wide gape of mouth. The short-faced tumbler has a beak -in outline almost like that of a finch; and the common tumbler has the singular -and strictly inherited habit of flying at a great height in a compact flock, -and tumbling in the air head over heels. The runt is a bird of great size, with -long, massive beak and large feet; some of the sub-breeds of runts have very -long necks, others very long wings and tails, others singularly short tails. -The barb is allied to the carrier, but, instead of a very long beak, has a very -short and very broad one. The pouter has a much elongated body, wings, and -legs; and its enormously developed crop, which it glories in inflating, may -well excite astonishment and even laughter. The turbit has a very short and -conical beak, with a line of reversed feathers down the breast; and it has the -habit of continually expanding slightly the upper part of the oesophagus. The -Jacobin has the feathers so much reversed along the back of the neck that they -form a hood, and it has, proportionally to its size, much elongated wing and -tail feathers. The trumpeter and laugher, as their names express, utter a very -different coo from the other breeds. The fantail has thirty or even forty -tail-feathers, instead of twelve or fourteen, the normal number in all members -of the great pigeon family; and these feathers are kept expanded, and are -carried so erect that in good birds the head and tail touch; the oil-gland is -quite aborted. Several other less distinct breeds might have been specified. - -In the skeletons of the several breeds, the development of the bones of the -face in length and breadth and curvature differs enormously. The shape, as well -as the breadth and length of the ramus of the lower jaw, varies in a highly -remarkable manner. The number of the caudal and sacral vertebræ vary; as does -the number of the ribs, together with their relative breadth and the presence -of processes. The size and shape of the apertures in the sternum are highly -variable; so is the degree of divergence and relative size of the two arms of -the furcula. The proportional width of the gape of mouth, the proportional -length of the eyelids, of the orifice of the nostrils, of the tongue (not -always in strict correlation with the length of beak), the size of the crop and -of the upper part of the oesophagus; the development and abortion of the -oil-gland; the number of the primary wing and caudal feathers; the relative -length of wing and tail to each other and to the body; the relative length of -leg and of the feet; the number of scutellæ on the toes, the development of -skin between the toes, are all points of structure which are variable. The -period at which the perfect plumage is acquired varies, as does the state of -the down with which the nestling birds are clothed when hatched. The shape and -size of the eggs vary. The manner of flight differs remarkably; as does in some -breeds the voice and disposition. Lastly, in certain breeds, the males and -females have come to differ to a slight degree from each other. - -Altogether at least a score of pigeons might be chosen, which if shown to an -ornithologist, and he were told that they were wild birds, would certainly, I -think, be ranked by him as well-defined species. Moreover, I do not believe -that any ornithologist would place the English carrier, the short-faced -tumbler, the runt, the barb, pouter, and fantail in the same genus; more -especially as in each of these breeds several truly-inherited sub-breeds, or -species as he might have called them, could be shown him. +aboriginal stocks, has been carried to an absurd extreme by some +authors. They believe that every race which breeds true, let the +distinctive characters be ever so slight, has had its wild prototype. At +this rate there must have existed at least a score of species of wild +cattle, as many sheep, and several goats in Europe alone, and several +even within Great Britain. One author believes that there formerly +existed in Great Britain eleven wild species of sheep peculiar to it! +When we bear in mind that Britain has now hardly one peculiar mammal, +and France but few distinct from those of Germany and conversely, and so +with Hungary, Spain, etc., but that each of these kingdoms possesses +several peculiar breeds of cattle, sheep, etc., we must admit that many +domestic breeds have originated in Europe; for whence could they have +been derived, as these several countries do not possess a number of +peculiar species as distinct parent-stocks? So it is in India. Even in +the case of the domestic dogs of the whole world, which I fully admit +have probably descended from several wild species, I cannot doubt that +there has been an immense amount of inherited variation. Who can believe +that animals closely resembling the Italian greyhound, the bloodhound, +the bull-dog, or Blenheim spaniel, etc.—so unlike all wild Canidæ—ever +existed freely in a state of nature? It has often been loosely said that +all our races of dogs have been produced by the crossing of a few +aboriginal species; but by crossing we can get only forms in some degree +intermediate between their parents; and if we account for our several +domestic races by this process, we must admit the former existence of +the most extreme forms, as the Italian greyhound, bloodhound, bull-dog, +etc., in the wild state. Moreover, the possibility of making distinct +races by crossing has been greatly exaggerated. There can be no doubt +that a race may be modified by occasional crosses, if aided by the +careful selection of those individual mongrels, which present any +desired character; but that a race could be obtained nearly intermediate +between two extremely different races or species, I can hardly believe. +Sir J. Sebright expressly experimentised for this object, and failed. +The offspring from the first cross between two pure breeds is tolerably +and sometimes (as I have found with pigeons) extremely uniform, and +everything seems simple enough; but when these mongrels are crossed one +with another for several generations, hardly two of them will be alike, +and then the extreme difficulty, or rather utter hopelessness, of the +task becomes apparent. Certainly, a breed intermediate between two very +distinct breeds could not be got without extreme care and long-continued +selection; nor can I find a single case on record of a permanent race +having been thus formed. + +On the Breeds of the Domestic Pigeon.—Believing that it is always best +to study some special group, I have, after deliberation, taken up +domestic pigeons. I have kept every breed which I could purchase or +obtain, and have been most kindly favoured with skins from several +quarters of the world, more especially by the Honourable W. Elliot from +India, and by the Honourable C. Murray from Persia. Many treatises in +different languages have been published on pigeons, and some of them are +very important, as being of considerable antiquity. I have associated +with several eminent fanciers, and have been permitted to join two of +the London Pigeon Clubs. The diversity of the breeds is something +astonishing. Compare the English carrier and the short-faced tumbler, +and see the wonderful difference in their beaks, entailing corresponding +differences in their skulls. The carrier, more especially the male bird, +is also remarkable from the wonderful development of the carunculated +skin about the head, and this is accompanied by greatly elongated +eyelids, very large external orifices to the nostrils, and a wide gape +of mouth. The short-faced tumbler has a beak in outline almost like that +of a finch; and the common tumbler has the singular and strictly +inherited habit of flying at a great height in a compact flock, and +tumbling in the air head over heels. The runt is a bird of great size, +with long, massive beak and large feet; some of the sub-breeds of runts +have very long necks, others very long wings and tails, others +singularly short tails. The barb is allied to the carrier, but, instead +of a very long beak, has a very short and very broad one. The pouter has +a much elongated body, wings, and legs; and its enormously developed +crop, which it glories in inflating, may well excite astonishment and +even laughter. The turbit has a very short and conical beak, with a line +of reversed feathers down the breast; and it has the habit of +continually expanding slightly the upper part of the oesophagus. The +Jacobin has the feathers so much reversed along the back of the neck +that they form a hood, and it has, proportionally to its size, much +elongated wing and tail feathers. The trumpeter and laugher, as their +names express, utter a very different coo from the other breeds. The +fantail has thirty or even forty tail-feathers, instead of twelve or +fourteen, the normal number in all members of the great pigeon family; +and these feathers are kept expanded, and are carried so erect that in +good birds the head and tail touch; the oil-gland is quite aborted. +Several other less distinct breeds might have been specified. + +In the skeletons of the several breeds, the development of the bones of +the face in length and breadth and curvature differs enormously. The +shape, as well as the breadth and length of the ramus of the lower jaw, +varies in a highly remarkable manner. The number of the caudal and +sacral vertebræ vary; as does the number of the ribs, together with +their relative breadth and the presence of processes. The size and shape +of the apertures in the sternum are highly variable; so is the degree of +divergence and relative size of the two arms of the furcula. The +proportional width of the gape of mouth, the proportional length of the +eyelids, of the orifice of the nostrils, of the tongue (not always in +strict correlation with the length of beak), the size of the crop and of +the upper part of the oesophagus; the development and abortion of the +oil-gland; the number of the primary wing and caudal feathers; the +relative length of wing and tail to each other and to the body; the +relative length of leg and of the feet; the number of scutellæ on the +toes, the development of skin between the toes, are all points of +structure which are variable. The period at which the perfect plumage is +acquired varies, as does the state of the down with which the nestling +birds are clothed when hatched. The shape and size of the eggs vary. The +manner of flight differs remarkably; as does in some breeds the voice +and disposition. Lastly, in certain breeds, the males and females have +come to differ to a slight degree from each other. + +Altogether at least a score of pigeons might be chosen, which if shown +to an ornithologist, and he were told that they were wild birds, would +certainly, I think, be ranked by him as well-defined species. Moreover, +I do not believe that any ornithologist would place the English carrier, +the short-faced tumbler, the runt, the barb, pouter, and fantail in the +same genus; more especially as in each of these breeds several +truly-inherited sub-breeds, or species as he might have called them, +could be shown him. Great as the differences are between the breeds of pigeons, I am fully -convinced that the common opinion of naturalists is correct, namely, that all -have descended from the rock-pigeon (Columba livia), including under this term -several geographical races or sub-species, which differ from each other in the -most trifling respects. As several of the reasons which have led me to this -belief are in some degree applicable in other cases, I will here briefly give -them. If the several breeds are not varieties, and have not proceeded from the -rock-pigeon, they must have descended from at least seven or eight aboriginal -stocks; for it is impossible to make the present domestic breeds by the -crossing of any lesser number: how, for instance, could a pouter be produced by -crossing two breeds unless one of the parent-stocks possessed the -characteristic enormous crop? The supposed aboriginal stocks must all have been -rock-pigeons, that is, not breeding or willingly perching on trees. But besides -C. livia, with its geographical sub-species, only two or three other species of -rock-pigeons are known; and these have not any of the characters of the -domestic breeds. Hence the supposed aboriginal stocks must either still exist -in the countries where they were originally domesticated, and yet be unknown to -ornithologists; and this, considering their size, habits, and remarkable -characters, seems very improbable; or they must have become extinct in the wild -state. But birds breeding on precipices, and good fliers, are unlikely to be -exterminated; and the common rock-pigeon, which has the same habits with the -domestic breeds, has not been exterminated even on several of the smaller -British islets, or on the shores of the Mediterranean. Hence the supposed -extermination of so many species having similar habits with the rock-pigeon -seems to me a very rash assumption. Moreover, the several above-named -domesticated breeds have been transported to all parts of the world, and, -therefore, some of them must have been carried back again into their native -country; but not one has ever become wild or feral, though the dovecot-pigeon, -which is the rock-pigeon in a very slightly altered state, has become feral in -several places. Again, all recent experience shows that it is most difficult to -get any wild animal to breed freely under domestication; yet on the hypothesis -of the multiple origin of our pigeons, it must be assumed that at least seven +convinced that the common opinion of naturalists is correct, namely, +that all have descended from the rock-pigeon (Columba livia), including +under this term several geographical races or sub-species, which differ +from each other in the most trifling respects. As several of the reasons +which have led me to this belief are in some degree applicable in other +cases, I will here briefly give them. If the several breeds are not +varieties, and have not proceeded from the rock-pigeon, they must have +descended from at least seven or eight aboriginal stocks; for it is +impossible to make the present domestic breeds by the crossing of any +lesser number: how, for instance, could a pouter be produced by crossing +two breeds unless one of the parent-stocks possessed the characteristic +enormous crop? The supposed aboriginal stocks must all have been +rock-pigeons, that is, not breeding or willingly perching on trees. But +besides C. livia, with its geographical sub-species, only two or three +other species of rock-pigeons are known; and these have not any of the +characters of the domestic breeds. Hence the supposed aboriginal stocks +must either still exist in the countries where they were originally +domesticated, and yet be unknown to ornithologists; and this, +considering their size, habits, and remarkable characters, seems very +improbable; or they must have become extinct in the wild state. But +birds breeding on precipices, and good fliers, are unlikely to be +exterminated; and the common rock-pigeon, which has the same habits with +the domestic breeds, has not been exterminated even on several of the +smaller British islets, or on the shores of the Mediterranean. Hence the +supposed extermination of so many species having similar habits with the +rock-pigeon seems to me a very rash assumption. Moreover, the several +above-named domesticated breeds have been transported to all parts of +the world, and, therefore, some of them must have been carried back +again into their native country; but not one has ever become wild or +feral, though the dovecot-pigeon, which is the rock-pigeon in a very +slightly altered state, has become feral in several places. Again, all +recent experience shows that it is most difficult to get any wild animal +to breed freely under domestication; yet on the hypothesis of the +multiple origin of our pigeons, it must be assumed that at least seven or eight species were so thoroughly domesticated in ancient times by half-civilized man, as to be quite prolific under confinement. -An argument, as it seems to me, of great weight, and applicable in several -other cases, is, that the above-specified breeds, though agreeing generally in -constitution, habits, voice, colouring, and in most parts of their structure, -with the wild rock-pigeon, yet are certainly highly abnormal in other parts of -their structure: we may look in vain throughout the whole great family of -Columbidæ for a beak like that of the English carrier, or that of the -short-faced tumbler, or barb; for reversed feathers like those of the jacobin; -for a crop like that of the pouter; for tail-feathers like those of the -fantail. Hence it must be assumed not only that half-civilized man succeeded in -thoroughly domesticating several species, but that he intentionally or by -chance picked out extraordinarily abnormal species; and further, that these -very species have since all become extinct or unknown. So many strange -contingencies seem to me improbable in the highest degree. - -Some facts in regard to the colouring of pigeons well deserve consideration. -The rock-pigeon is of a slaty-blue, and has a white rump (the Indian -sub-species, C. intermedia of Strickland, having it bluish); the tail has a -terminal dark bar, with the bases of the outer feathers externally edged with -white; the wings have two black bars; some semi-domestic breeds and some -apparently truly wild breeds have, besides the two black bars, the wings -chequered with black. These several marks do not occur together in any other -species of the whole family. Now, in every one of the domestic breeds, taking -thoroughly well-bred birds, all the above marks, even to the white edging of -the outer tail-feathers, sometimes concur perfectly developed. Moreover, when -two birds belonging to two distinct breeds are crossed, neither of which is -blue or has any of the above-specified marks, the mongrel offspring are very -apt suddenly to acquire these characters; for instance, I crossed some -uniformly white fantails with some uniformly black barbs, and they produced -mottled brown and black birds; these I again crossed together, and one -grandchild of the pure white fantail and pure black barb was of as beautiful a -blue colour, with the white rump, double black wing-bar, and barred and -white-edged tail-feathers, as any wild rock-pigeon! We can understand these -facts, on the well-known principle of reversion to ancestral characters, if all -the domestic breeds have descended from the rock-pigeon. But if we deny this, -we must make one of the two following highly improbable suppositions. Either, -firstly, that all the several imagined aboriginal stocks were coloured and -marked like the rock-pigeon, although no other existing species is thus -coloured and marked, so that in each separate breed there might be a tendency -to revert to the very same colours and markings. Or, secondly, that each breed, -even the purest, has within a dozen or, at most, within a score of generations, -been crossed by the rock-pigeon: I say within a dozen or twenty generations, -for we know of no fact countenancing the belief that the child ever reverts to -some one ancestor, removed by a greater number of generations. In a breed which -has been crossed only once with some distinct breed, the tendency to reversion -to any character derived from such cross will naturally become less and less, -as in each succeeding generation there will be less of the foreign blood; but -when there has been no cross with a distinct breed, and there is a tendency in -both parents to revert to a character, which has been lost during some former -generation, this tendency, for all that we can see to the contrary, may be -transmitted undiminished for an indefinite number of generations. These two -distinct cases are often confounded in treatises on inheritance. - -Lastly, the hybrids or mongrels from between all the domestic breeds of pigeons -are perfectly fertile. I can state this from my own observations, purposely -made on the most distinct breeds. Now, it is difficult, perhaps impossible, to -bring forward one case of the hybrid offspring of two animals clearly distinct -being themselves perfectly fertile. Some authors believe that long-continued -domestication eliminates this strong tendency to sterility: from the history of -the dog I think there is some probability in this hypothesis, if applied to +An argument, as it seems to me, of great weight, and applicable in +several other cases, is, that the above-specified breeds, though +agreeing generally in constitution, habits, voice, colouring, and in +most parts of their structure, with the wild rock-pigeon, yet are +certainly highly abnormal in other parts of their structure: we may look +in vain throughout the whole great family of Columbidæ for a beak like +that of the English carrier, or that of the short-faced tumbler, or +barb; for reversed feathers like those of the jacobin; for a crop like +that of the pouter; for tail-feathers like those of the fantail. Hence +it must be assumed not only that half-civilized man succeeded in +thoroughly domesticating several species, but that he intentionally or +by chance picked out extraordinarily abnormal species; and further, that +these very species have since all become extinct or unknown. So many +strange contingencies seem to me improbable in the highest degree. + +Some facts in regard to the colouring of pigeons well deserve +consideration. The rock-pigeon is of a slaty-blue, and has a white rump +(the Indian sub-species, C. intermedia of Strickland, having it bluish); +the tail has a terminal dark bar, with the bases of the outer feathers +externally edged with white; the wings have two black bars; some +semi-domestic breeds and some apparently truly wild breeds have, besides +the two black bars, the wings chequered with black. These several marks +do not occur together in any other species of the whole family. Now, in +every one of the domestic breeds, taking thoroughly well-bred birds, all +the above marks, even to the white edging of the outer tail-feathers, +sometimes concur perfectly developed. Moreover, when two birds belonging +to two distinct breeds are crossed, neither of which is blue or has any +of the above-specified marks, the mongrel offspring are very apt +suddenly to acquire these characters; for instance, I crossed some +uniformly white fantails with some uniformly black barbs, and they +produced mottled brown and black birds; these I again crossed together, +and one grandchild of the pure white fantail and pure black barb was of +as beautiful a blue colour, with the white rump, double black wing-bar, +and barred and white-edged tail-feathers, as any wild rock-pigeon! We +can understand these facts, on the well-known principle of reversion to +ancestral characters, if all the domestic breeds have descended from the +rock-pigeon. But if we deny this, we must make one of the two following +highly improbable suppositions. Either, firstly, that all the several +imagined aboriginal stocks were coloured and marked like the +rock-pigeon, although no other existing species is thus coloured and +marked, so that in each separate breed there might be a tendency to +revert to the very same colours and markings. Or, secondly, that each +breed, even the purest, has within a dozen or, at most, within a score +of generations, been crossed by the rock-pigeon: I say within a dozen or +twenty generations, for we know of no fact countenancing the belief that +the child ever reverts to some one ancestor, removed by a greater number +of generations. In a breed which has been crossed only once with some +distinct breed, the tendency to reversion to any character derived from +such cross will naturally become less and less, as in each succeeding +generation there will be less of the foreign blood; but when there has +been no cross with a distinct breed, and there is a tendency in both +parents to revert to a character, which has been lost during some former +generation, this tendency, for all that we can see to the contrary, may +be transmitted undiminished for an indefinite number of generations. +These two distinct cases are often confounded in treatises on +inheritance. + +Lastly, the hybrids or mongrels from between all the domestic breeds of +pigeons are perfectly fertile. I can state this from my own +observations, purposely made on the most distinct breeds. Now, it is +difficult, perhaps impossible, to bring forward one case of the hybrid +offspring of two animals clearly distinct being themselves perfectly +fertile. Some authors believe that long-continued domestication +eliminates this strong tendency to sterility: from the history of the +dog I think there is some probability in this hypothesis, if applied to species closely related together, though it is unsupported by a single -experiment. But to extend the hypothesis so far as to suppose that species, -aboriginally as distinct as carriers, tumblers, pouters, and fantails now are, -should yield offspring perfectly fertile, inter se, seems to me rash in the -extreme. - -From these several reasons, namely, the improbability of man having formerly -got seven or eight supposed species of pigeons to breed freely under -domestication; these supposed species being quite unknown in a wild state, and -their becoming nowhere feral; these species having very abnormal characters in -certain respects, as compared with all other Columbidæ, though so like in most -other respects to the rock-pigeon; the blue colour and various marks -occasionally appearing in all the breeds, both when kept pure and when crossed; -the mongrel offspring being perfectly fertile;—from these several reasons, -taken together, I can feel no doubt that all our domestic breeds have descended -from the Columba livia with its geographical sub-species. - -In favour of this view, I may add, firstly, that C. livia, or the rock-pigeon, -has been found capable of domestication in Europe and in India; and that it -agrees in habits and in a great number of points of structure with all the -domestic breeds. Secondly, although an English carrier or short-faced tumbler -differs immensely in certain characters from the rock-pigeon, yet by comparing -the several sub-breeds of these breeds, more especially those brought from -distant countries, we can make an almost perfect series between the extremes of -structure. Thirdly, those characters which are mainly distinctive of each -breed, for instance the wattle and length of beak of the carrier, the shortness -of that of the tumbler, and the number of tail-feathers in the fantail, are in -each breed eminently variable; and the explanation of this fact will be obvious -when we come to treat of selection. Fourthly, pigeons have been watched, and -tended with the utmost care, and loved by many people. They have been -domesticated for thousands of years in several quarters of the world; the -earliest known record of pigeons is in the fifth Aegyptian dynasty, about 3000 -B.C., as was pointed out to me by Professor Lepsius; but Mr. Birch informs me -that pigeons are given in a bill of fare in the previous dynasty. In the time -of the Romans, as we hear from Pliny, immense prices were given for pigeons; -“nay, they are come to this pass, that they can reckon up their pedigree and -race.” Pigeons were much valued by Akber Khan in India, about the year 1600; -never less than 20,000 pigeons were taken with the court. “The monarchs of Iran -and Turan sent him some very rare birds;” and, continues the courtly historian, -“His Majesty by crossing the breeds, which method was never practised before, -has improved them astonishingly.” About this same period the Dutch were as -eager about pigeons as were the old Romans. The paramount importance of these -considerations in explaining the immense amount of variation which pigeons have -undergone, will be obvious when we treat of Selection. We shall then, also, see -how it is that the breeds so often have a somewhat monstrous character. It is -also a most favourable circumstance for the production of distinct breeds, that -male and female pigeons can be easily mated for life; and thus different breeds -can be kept together in the same aviary. - -I have discussed the probable origin of domestic pigeons at some, yet quite -insufficient, length; because when I first kept pigeons and watched the several -kinds, knowing well how true they bred, I felt fully as much difficulty in -believing that they could ever have descended from a common parent, as any -naturalist could in coming to a similar conclusion in regard to the many -species of finches, or other large groups of birds, in nature. One circumstance -has struck me much; namely, that all the breeders of the various domestic -animals and the cultivators of plants, with whom I have ever conversed, or -whose treatises I have read, are firmly convinced that the several breeds to -which each has attended, are descended from so many aboriginally distinct -species. Ask, as I have asked, a celebrated raiser of Hereford cattle, whether -his cattle might not have descended from long horns, and he will laugh you to -scorn. I have never met a pigeon, or poultry, or duck, or rabbit fancier, who -was not fully convinced that each main breed was descended from a distinct -species. Van Mons, in his treatise on pears and apples, shows how utterly he -disbelieves that the several sorts, for instance a Ribston-pippin or -Codlin-apple, could ever have proceeded from the seeds of the same tree. -Innumerable other examples could be given. The explanation, I think, is simple: -from long-continued study they are strongly impressed with the differences -between the several races; and though they well know that each race varies -slightly, for they win their prizes by selecting such slight differences, yet -they ignore all general arguments, and refuse to sum up in their minds slight -differences accumulated during many successive generations. May not those -naturalists who, knowing far less of the laws of inheritance than does the -breeder, and knowing no more than he does of the intermediate links in the long -lines of descent, yet admit that many of our domestic races have descended from -the same parents—may they not learn a lesson of caution, when they deride the -idea of species in a state of nature being lineal descendants of other species? - -Selection.—Let us now briefly consider the steps by which domestic races have -been produced, either from one or from several allied species. Some little -effect may, perhaps, be attributed to the direct action of the external -conditions of life, and some little to habit; but he would be a bold man who -would account by such agencies for the differences of a dray and race horse, a -greyhound and bloodhound, a carrier and tumbler pigeon. One of the most -remarkable features in our domesticated races is that we see in them -adaptation, not indeed to the animal’s or plant’s own good, but to man’s use or -fancy. Some variations useful to him have probably arisen suddenly, or by one -step; many botanists, for instance, believe that the fuller’s teazle, with its -hooks, which cannot be rivalled by any mechanical contrivance, is only a -variety of the wild Dipsacus; and this amount of change may have suddenly -arisen in a seedling. So it has probably been with the turnspit dog; and this -is known to have been the case with the ancon sheep. But when we compare the -dray-horse and race-horse, the dromedary and camel, the various breeds of sheep -fitted either for cultivated land or mountain pasture, with the wool of one -breed good for one purpose, and that of another breed for another purpose; when -we compare the many breeds of dogs, each good for man in very different ways; -when we compare the game-cock, so pertinacious in battle, with other breeds so -little quarrelsome, with “everlasting layers” which never desire to sit, and -with the bantam so small and elegant; when we compare the host of agricultural, -culinary, orchard, and flower-garden races of plants, most useful to man at -different seasons and for different purposes, or so beautiful in his eyes, we -must, I think, look further than to mere variability. We cannot suppose that -all the breeds were suddenly produced as perfect and as useful as we now see -them; indeed, in several cases, we know that this has not been their history. -The key is man’s power of accumulative selection: nature gives successive -variations; man adds them up in certain directions useful to him. In this sense -he may be said to make for himself useful breeds. - -The great power of this principle of selection is not hypothetical. It is -certain that several of our eminent breeders have, even within a single -lifetime, modified to a large extent some breeds of cattle and sheep. In order -fully to realise what they have done, it is almost necessary to read several of -the many treatises devoted to this subject, and to inspect the animals. -Breeders habitually speak of an animal’s organisation as something quite -plastic, which they can model almost as they please. If I had space I could -quote numerous passages to this effect from highly competent authorities. -Youatt, who was probably better acquainted with the works of agriculturalists -than almost any other individual, and who was himself a very good judge of an -animal, speaks of the principle of selection as “that which enables the -agriculturist, not only to modify the character of his flock, but to change it -altogether. It is the magician’s wand, by means of which he may summon into -life whatever form and mould he pleases.” Lord Somerville, speaking of what -breeders have done for sheep, says:—“It would seem as if they had chalked out -upon a wall a form perfect in itself, and then had given it existence.” That -most skilful breeder, Sir John Sebright, used to say, with respect to pigeons, -that “he would produce any given feather in three years, but it would take him -six years to obtain head and beak.” In Saxony the importance of the principle -of selection in regard to merino sheep is so fully recognised, that men follow -it as a trade: the sheep are placed on a table and are studied, like a picture -by a connoisseur; this is done three times at intervals of months, and the -sheep are each time marked and classed, so that the very best may ultimately be -selected for breeding. - -What English breeders have actually effected is proved by the enormous prices -given for animals with a good pedigree; and these have now been exported to -almost every quarter of the world. The improvement is by no means generally due -to crossing different breeds; all the best breeders are strongly opposed to -this practice, except sometimes amongst closely allied sub-breeds. And when a -cross has been made, the closest selection is far more indispensable even than -in ordinary cases. If selection consisted merely in separating some very -distinct variety, and breeding from it, the principle would be so obvious as -hardly to be worth notice; but its importance consists in the great effect -produced by the accumulation in one direction, during successive generations, -of differences absolutely inappreciable by an uneducated eye—differences which -I for one have vainly attempted to appreciate. Not one man in a thousand has -accuracy of eye and judgment sufficient to become an eminent breeder. If gifted -with these qualities, and he studies his subject for years, and devotes his -lifetime to it with indomitable perseverance, he will succeed, and may make -great improvements; if he wants any of these qualities, he will assuredly fail. -Few would readily believe in the natural capacity and years of practice -requisite to become even a skilful pigeon-fancier. - -The same principles are followed by horticulturists; but the variations are -here often more abrupt. No one supposes that our choicest productions have been -produced by a single variation from the aboriginal stock. We have proofs that -this is not so in some cases, in which exact records have been kept; thus, to -give a very trifling instance, the steadily-increasing size of the common -gooseberry may be quoted. We see an astonishing improvement in many florists’ -flowers, when the flowers of the present day are compared with drawings made -only twenty or thirty years ago. When a race of plants is once pretty well -established, the seed-raisers do not pick out the best plants, but merely go -over their seed-beds, and pull up the “rogues,” as they call the plants that -deviate from the proper standard. With animals this kind of selection is, in -fact, also followed; for hardly any one is so careless as to allow his worst -animals to breed. +experiment. But to extend the hypothesis so far as to suppose that +species, aboriginally as distinct as carriers, tumblers, pouters, and +fantails now are, should yield offspring perfectly fertile, inter se, +seems to me rash in the extreme. + +From these several reasons, namely, the improbability of man having +formerly got seven or eight supposed species of pigeons to breed freely +under domestication; these supposed species being quite unknown in a +wild state, and their becoming nowhere feral; these species having very +abnormal characters in certain respects, as compared with all other +Columbidæ, though so like in most other respects to the rock-pigeon; the +blue colour and various marks occasionally appearing in all the breeds, +both when kept pure and when crossed; the mongrel offspring being +perfectly fertile;—from these several reasons, taken together, I can +feel no doubt that all our domestic breeds have descended from the +Columba livia with its geographical sub-species. + +In favour of this view, I may add, firstly, that C. livia, or the +rock-pigeon, has been found capable of domestication in Europe and in +India; and that it agrees in habits and in a great number of points of +structure with all the domestic breeds. Secondly, although an English +carrier or short-faced tumbler differs immensely in certain characters +from the rock-pigeon, yet by comparing the several sub-breeds of these +breeds, more especially those brought from distant countries, we can +make an almost perfect series between the extremes of structure. +Thirdly, those characters which are mainly distinctive of each breed, +for instance the wattle and length of beak of the carrier, the shortness +of that of the tumbler, and the number of tail-feathers in the fantail, +are in each breed eminently variable; and the explanation of this fact +will be obvious when we come to treat of selection. Fourthly, pigeons +have been watched, and tended with the utmost care, and loved by many +people. They have been domesticated for thousands of years in several +quarters of the world; the earliest known record of pigeons is in the +fifth Aegyptian dynasty, about 3000 B.C., as was pointed out to me by +Professor Lepsius; but Mr. Birch informs me that pigeons are given in a +bill of fare in the previous dynasty. In the time of the Romans, as we +hear from Pliny, immense prices were given for pigeons; “nay, they are +come to this pass, that they can reckon up their pedigree and race.” +Pigeons were much valued by Akber Khan in India, about the year 1600; +never less than 20,000 pigeons were taken with the court. “The monarchs +of Iran and Turan sent him some very rare birds;” and, continues the +courtly historian, “His Majesty by crossing the breeds, which method was +never practised before, has improved them astonishingly.” About this +same period the Dutch were as eager about pigeons as were the old +Romans. The paramount importance of these considerations in explaining +the immense amount of variation which pigeons have undergone, will be +obvious when we treat of Selection. We shall then, also, see how it is +that the breeds so often have a somewhat monstrous character. It is also +a most favourable circumstance for the production of distinct breeds, +that male and female pigeons can be easily mated for life; and thus +different breeds can be kept together in the same aviary. + +I have discussed the probable origin of domestic pigeons at some, yet +quite insufficient, length; because when I first kept pigeons and +watched the several kinds, knowing well how true they bred, I felt fully +as much difficulty in believing that they could ever have descended from +a common parent, as any naturalist could in coming to a similar +conclusion in regard to the many species of finches, or other large +groups of birds, in nature. One circumstance has struck me much; namely, +that all the breeders of the various domestic animals and the +cultivators of plants, with whom I have ever conversed, or whose +treatises I have read, are firmly convinced that the several breeds to +which each has attended, are descended from so many aboriginally +distinct species. Ask, as I have asked, a celebrated raiser of Hereford +cattle, whether his cattle might not have descended from long horns, and +he will laugh you to scorn. I have never met a pigeon, or poultry, or +duck, or rabbit fancier, who was not fully convinced that each main +breed was descended from a distinct species. Van Mons, in his treatise +on pears and apples, shows how utterly he disbelieves that the several +sorts, for instance a Ribston-pippin or Codlin-apple, could ever have +proceeded from the seeds of the same tree. Innumerable other examples +could be given. The explanation, I think, is simple: from long-continued +study they are strongly impressed with the differences between the +several races; and though they well know that each race varies slightly, +for they win their prizes by selecting such slight differences, yet they +ignore all general arguments, and refuse to sum up in their minds slight +differences accumulated during many successive generations. May not +those naturalists who, knowing far less of the laws of inheritance than +does the breeder, and knowing no more than he does of the intermediate +links in the long lines of descent, yet admit that many of our domestic +races have descended from the same parents—may they not learn a lesson +of caution, when they deride the idea of species in a state of nature +being lineal descendants of other species? + +Selection.—Let us now briefly consider the steps by which domestic races +have been produced, either from one or from several allied species. Some +little effect may, perhaps, be attributed to the direct action of the +external conditions of life, and some little to habit; but he would be a +bold man who would account by such agencies for the differences of a +dray and race horse, a greyhound and bloodhound, a carrier and tumbler +pigeon. One of the most remarkable features in our domesticated races is +that we see in them adaptation, not indeed to the animal’s or plant’s +own good, but to man’s use or fancy. Some variations useful to him have +probably arisen suddenly, or by one step; many botanists, for instance, +believe that the fuller’s teazle, with its hooks, which cannot be +rivalled by any mechanical contrivance, is only a variety of the wild +Dipsacus; and this amount of change may have suddenly arisen in a +seedling. So it has probably been with the turnspit dog; and this is +known to have been the case with the ancon sheep. But when we compare +the dray-horse and race-horse, the dromedary and camel, the various +breeds of sheep fitted either for cultivated land or mountain pasture, +with the wool of one breed good for one purpose, and that of another +breed for another purpose; when we compare the many breeds of dogs, each +good for man in very different ways; when we compare the game-cock, so +pertinacious in battle, with other breeds so little quarrelsome, with +“everlasting layers” which never desire to sit, and with the bantam so +small and elegant; when we compare the host of agricultural, culinary, +orchard, and flower-garden races of plants, most useful to man at +different seasons and for different purposes, or so beautiful in his +eyes, we must, I think, look further than to mere variability. We cannot +suppose that all the breeds were suddenly produced as perfect and as +useful as we now see them; indeed, in several cases, we know that this +has not been their history. The key is man’s power of accumulative +selection: nature gives successive variations; man adds them up in +certain directions useful to him. In this sense he may be said to make +for himself useful breeds. + +The great power of this principle of selection is not hypothetical. It +is certain that several of our eminent breeders have, even within a +single lifetime, modified to a large extent some breeds of cattle and +sheep. In order fully to realise what they have done, it is almost +necessary to read several of the many treatises devoted to this subject, +and to inspect the animals. Breeders habitually speak of an animal’s +organisation as something quite plastic, which they can model almost as +they please. If I had space I could quote numerous passages to this +effect from highly competent authorities. Youatt, who was probably +better acquainted with the works of agriculturalists than almost any +other individual, and who was himself a very good judge of an animal, +speaks of the principle of selection as “that which enables the +agriculturist, not only to modify the character of his flock, but to +change it altogether. It is the magician’s wand, by means of which he +may summon into life whatever form and mould he pleases.” Lord +Somerville, speaking of what breeders have done for sheep, says:—“It +would seem as if they had chalked out upon a wall a form perfect in +itself, and then had given it existence.” That most skilful breeder, Sir +John Sebright, used to say, with respect to pigeons, that “he would +produce any given feather in three years, but it would take him six +years to obtain head and beak.” In Saxony the importance of the +principle of selection in regard to merino sheep is so fully recognised, +that men follow it as a trade: the sheep are placed on a table and are +studied, like a picture by a connoisseur; this is done three times at +intervals of months, and the sheep are each time marked and classed, so +that the very best may ultimately be selected for breeding. + +What English breeders have actually effected is proved by the enormous +prices given for animals with a good pedigree; and these have now been +exported to almost every quarter of the world. The improvement is by no +means generally due to crossing different breeds; all the best breeders +are strongly opposed to this practice, except sometimes amongst closely +allied sub-breeds. And when a cross has been made, the closest selection +is far more indispensable even than in ordinary cases. If selection +consisted merely in separating some very distinct variety, and breeding +from it, the principle would be so obvious as hardly to be worth notice; +but its importance consists in the great effect produced by the +accumulation in one direction, during successive generations, of +differences absolutely inappreciable by an uneducated eye—differences +which I for one have vainly attempted to appreciate. Not one man in a +thousand has accuracy of eye and judgment sufficient to become an +eminent breeder. If gifted with these qualities, and he studies his +subject for years, and devotes his lifetime to it with indomitable +perseverance, he will succeed, and may make great improvements; if he +wants any of these qualities, he will assuredly fail. Few would readily +believe in the natural capacity and years of practice requisite to +become even a skilful pigeon-fancier. + +The same principles are followed by horticulturists; but the variations +are here often more abrupt. No one supposes that our choicest +productions have been produced by a single variation from the aboriginal +stock. We have proofs that this is not so in some cases, in which exact +records have been kept; thus, to give a very trifling instance, the +steadily-increasing size of the common gooseberry may be quoted. We see +an astonishing improvement in many florists’ flowers, when the flowers +of the present day are compared with drawings made only twenty or thirty +years ago. When a race of plants is once pretty well established, the +seed-raisers do not pick out the best plants, but merely go over their +seed-beds, and pull up the “rogues,” as they call the plants that +deviate from the proper standard. With animals this kind of selection +is, in fact, also followed; for hardly any one is so careless as to +allow his worst animals to breed. In regard to plants, there is another means of observing the accumulated -effects of selection—namely, by comparing the diversity of flowers in the -different varieties of the same species in the flower-garden; the diversity of -leaves, pods, or tubers, or whatever part is valued, in the kitchen-garden, in -comparison with the flowers of the same varieties; and the diversity of fruit -of the same species in the orchard, in comparison with the leaves and flowers -of the same set of varieties. See how different the leaves of the cabbage are, -and how extremely alike the flowers; how unlike the flowers of the heartsease -are, and how alike the leaves; how much the fruit of the different kinds of -gooseberries differ in size, colour, shape, and hairiness, and yet the flowers -present very slight differences. It is not that the varieties which differ -largely in some one point do not differ at all in other points; this is hardly +effects of selection—namely, by comparing the diversity of flowers in +the different varieties of the same species in the flower-garden; the +diversity of leaves, pods, or tubers, or whatever part is valued, in the +kitchen-garden, in comparison with the flowers of the same varieties; +and the diversity of fruit of the same species in the orchard, in +comparison with the leaves and flowers of the same set of varieties. See +how different the leaves of the cabbage are, and how extremely alike the +flowers; how unlike the flowers of the heartsease are, and how alike the +leaves; how much the fruit of the different kinds of gooseberries differ +in size, colour, shape, and hairiness, and yet the flowers present very +slight differences. It is not that the varieties which differ largely in +some one point do not differ at all in other points; this is hardly ever, perhaps never, the case. The laws of correlation of growth, the -importance of which should never be overlooked, will ensure some differences; -but, as a general rule, I cannot doubt that the continued selection of slight -variations, either in the leaves, the flowers, or the fruit, will produce races -differing from each other chiefly in these characters. +importance of which should never be overlooked, will ensure some +differences; but, as a general rule, I cannot doubt that the continued +selection of slight variations, either in the leaves, the flowers, or +the fruit, will produce races differing from each other chiefly in these +characters. It may be objected that the principle of selection has been reduced to -methodical practice for scarcely more than three-quarters of a century; it has -certainly been more attended to of late years, and many treatises have been -published on the subject; and the result, I may add, has been, in a -corresponding degree, rapid and important. But it is very far from true that -the principle is a modern discovery. I could give several references to the -full acknowledgment of the importance of the principle in works of high -antiquity. In rude and barbarous periods of English history choice animals were -often imported, and laws were passed to prevent their exportation: the -destruction of horses under a certain size was ordered, and this may be -compared to the “roguing” of plants by nurserymen. The principle of selection I -find distinctly given in an ancient Chinese encyclopædia. Explicit rules are -laid down by some of the Roman classical writers. From passages in Genesis, it -is clear that the colour of domestic animals was at that early period attended -to. Savages now sometimes cross their dogs with wild canine animals, to improve -the breed, and they formerly did so, as is attested by passages in Pliny. The -savages in South Africa match their draught cattle by colour, as do some of the -Esquimaux their teams of dogs. Livingstone shows how much good domestic breeds -are valued by the negroes of the interior of Africa who have not associated -with Europeans. Some of these facts do not show actual selection, but they show -that the breeding of domestic animals was carefully attended to in ancient -times, and is now attended to by the lowest savages. It would, indeed, have -been a strange fact, had attention not been paid to breeding, for the -inheritance of good and bad qualities is so obvious. - -At the present time, eminent breeders try by methodical selection, with a -distinct object in view, to make a new strain or sub-breed, superior to -anything existing in the country. But, for our purpose, a kind of Selection, -which may be called Unconscious, and which results from every one trying to -possess and breed from the best individual animals, is more important. Thus, a -man who intends keeping pointers naturally tries to get as good dogs as he can, -and afterwards breeds from his own best dogs, but he has no wish or expectation -of permanently altering the breed. Nevertheless I cannot doubt that this -process, continued during centuries, would improve and modify any breed, in the -same way as Bakewell, Collins, etc., by this very same process, only carried on -more methodically, did greatly modify, even during their own lifetimes, the -forms and qualities of their cattle. Slow and insensible changes of this kind -could never be recognised unless actual measurements or careful drawings of the -breeds in question had been made long ago, which might serve for comparison. In -some cases, however, unchanged or but little changed individuals of the same -breed may be found in less civilised districts, where the breed has been less -improved. There is reason to believe that King Charles’s spaniel has been -unconsciously modified to a large extent since the time of that monarch. Some -highly competent authorities are convinced that the setter is directly derived -from the spaniel, and has probably been slowly altered from it. It is known -that the English pointer has been greatly changed within the last century, and -in this case the change has, it is believed, been chiefly effected by crosses -with the fox-hound; but what concerns us is, that the change has been effected -unconsciously and gradually, and yet so effectually, that, though the old -Spanish pointer certainly came from Spain, Mr. Borrow has not seen, as I am -informed by him, any native dog in Spain like our pointer. - -By a similar process of selection, and by careful training, the whole body of -English racehorses have come to surpass in fleetness and size the parent Arab -stock, so that the latter, by the regulations for the Goodwood Races, are -favoured in the weights they carry. Lord Spencer and others have shown how the -cattle of England have increased in weight and in early maturity, compared with -the stock formerly kept in this country. By comparing the accounts given in old -pigeon treatises of carriers and tumblers with these breeds as now existing in -Britain, India, and Persia, we can, I think, clearly trace the stages through -which they have insensibly passed, and come to differ so greatly from the -rock-pigeon. - -Youatt gives an excellent illustration of the effects of a course of selection, -which may be considered as unconsciously followed, in so far that the breeders -could never have expected or even have wished to have produced the result which -ensued—namely, the production of two distinct strains. The two flocks of -Leicester sheep kept by Mr. Buckley and Mr. Burgess, as Mr. Youatt remarks, -“have been purely bred from the original stock of Mr. Bakewell for upwards of -fifty years. There is not a suspicion existing in the mind of any one at all -acquainted with the subject that the owner of either of them has deviated in -any one instance from the pure blood of Mr. Bakewell’s flock, and yet the -difference between the sheep possessed by these two gentlemen is so great that -they have the appearance of being quite different varieties.” +methodical practice for scarcely more than three-quarters of a century; +it has certainly been more attended to of late years, and many treatises +have been published on the subject; and the result, I may add, has been, +in a corresponding degree, rapid and important. But it is very far from +true that the principle is a modern discovery. I could give several +references to the full acknowledgment of the importance of the principle +in works of high antiquity. In rude and barbarous periods of English +history choice animals were often imported, and laws were passed to +prevent their exportation: the destruction of horses under a certain +size was ordered, and this may be compared to the “roguing” of plants by +nurserymen. The principle of selection I find distinctly given in an +ancient Chinese encyclopædia. Explicit rules are laid down by some of +the Roman classical writers. From passages in Genesis, it is clear that +the colour of domestic animals was at that early period attended to. +Savages now sometimes cross their dogs with wild canine animals, to +improve the breed, and they formerly did so, as is attested by passages +in Pliny. The savages in South Africa match their draught cattle by +colour, as do some of the Esquimaux their teams of dogs. Livingstone +shows how much good domestic breeds are valued by the negroes of the +interior of Africa who have not associated with Europeans. Some of these +facts do not show actual selection, but they show that the breeding of +domestic animals was carefully attended to in ancient times, and is now +attended to by the lowest savages. It would, indeed, have been a strange +fact, had attention not been paid to breeding, for the inheritance of +good and bad qualities is so obvious. + +At the present time, eminent breeders try by methodical selection, with +a distinct object in view, to make a new strain or sub-breed, superior +to anything existing in the country. But, for our purpose, a kind of +Selection, which may be called Unconscious, and which results from every +one trying to possess and breed from the best individual animals, is +more important. Thus, a man who intends keeping pointers naturally tries +to get as good dogs as he can, and afterwards breeds from his own best +dogs, but he has no wish or expectation of permanently altering the +breed. Nevertheless I cannot doubt that this process, continued during +centuries, would improve and modify any breed, in the same way as +Bakewell, Collins, etc., by this very same process, only carried on more +methodically, did greatly modify, even during their own lifetimes, the +forms and qualities of their cattle. Slow and insensible changes of this +kind could never be recognised unless actual measurements or careful +drawings of the breeds in question had been made long ago, which might +serve for comparison. In some cases, however, unchanged or but little +changed individuals of the same breed may be found in less civilised +districts, where the breed has been less improved. There is reason to +believe that King Charles’s spaniel has been unconsciously modified to a +large extent since the time of that monarch. Some highly competent +authorities are convinced that the setter is directly derived from the +spaniel, and has probably been slowly altered from it. It is known that +the English pointer has been greatly changed within the last century, +and in this case the change has, it is believed, been chiefly effected +by crosses with the fox-hound; but what concerns us is, that the change +has been effected unconsciously and gradually, and yet so effectually, +that, though the old Spanish pointer certainly came from Spain, Mr. +Borrow has not seen, as I am informed by him, any native dog in Spain +like our pointer. + +By a similar process of selection, and by careful training, the whole +body of English racehorses have come to surpass in fleetness and size +the parent Arab stock, so that the latter, by the regulations for the +Goodwood Races, are favoured in the weights they carry. Lord Spencer and +others have shown how the cattle of England have increased in weight and +in early maturity, compared with the stock formerly kept in this +country. By comparing the accounts given in old pigeon treatises of +carriers and tumblers with these breeds as now existing in Britain, +India, and Persia, we can, I think, clearly trace the stages through +which they have insensibly passed, and come to differ so greatly from +the rock-pigeon. + +Youatt gives an excellent illustration of the effects of a course of +selection, which may be considered as unconsciously followed, in so far +that the breeders could never have expected or even have wished to have +produced the result which ensued—namely, the production of two distinct +strains. The two flocks of Leicester sheep kept by Mr. Buckley and Mr. +Burgess, as Mr. Youatt remarks, “have been purely bred from the original +stock of Mr. Bakewell for upwards of fifty years. There is not a +suspicion existing in the mind of any one at all acquainted with the +subject that the owner of either of them has deviated in any one +instance from the pure blood of Mr. Bakewell’s flock, and yet the +difference between the sheep possessed by these two gentlemen is so +great that they have the appearance of being quite different varieties.” If there exist savages so barbarous as never to think of the inherited character of the offspring of their domestic animals, yet any one animal particularly useful to them, for any special purpose, would be carefully -preserved during famines and other accidents, to which savages are so liable, -and such choice animals would thus generally leave more offspring than the -inferior ones; so that in this case there would be a kind of unconscious -selection going on. We see the value set on animals even by the barbarians of -Tierra del Fuego, by their killing and devouring their old women, in times of -dearth, as of less value than their dogs. - -In plants the same gradual process of improvement, through the occasional -preservation of the best individuals, whether or not sufficiently distinct to -be ranked at their first appearance as distinct varieties, and whether or not -two or more species or races have become blended together by crossing, may -plainly be recognised in the increased size and beauty which we now see in the -varieties of the heartsease, rose, pelargonium, dahlia, and other plants, when -compared with the older varieties or with their parent-stocks. No one would -ever expect to get a first-rate heartsease or dahlia from the seed of a wild -plant. No one would expect to raise a first-rate melting pear from the seed of -a wild pear, though he might succeed from a poor seedling growing wild, if it -had come from a garden-stock. The pear, though cultivated in classical times, -appears, from Pliny’s description, to have been a fruit of very inferior -quality. I have seen great surprise expressed in horticultural works at the -wonderful skill of gardeners, in having produced such splendid results from -such poor materials; but the art, I cannot doubt, has been simple, and, as far -as the final result is concerned, has been followed almost unconsciously. It -has consisted in always cultivating the best known variety, sowing its seeds, -and, when a slightly better variety has chanced to appear, selecting it, and so -onwards. But the gardeners of the classical period, who cultivated the best -pear they could procure, never thought what splendid fruit we should eat; -though we owe our excellent fruit, in some small degree, to their having -naturally chosen and preserved the best varieties they could anywhere find. +preserved during famines and other accidents, to which savages are so +liable, and such choice animals would thus generally leave more +offspring than the inferior ones; so that in this case there would be a +kind of unconscious selection going on. We see the value set on animals +even by the barbarians of Tierra del Fuego, by their killing and +devouring their old women, in times of dearth, as of less value than +their dogs. + +In plants the same gradual process of improvement, through the +occasional preservation of the best individuals, whether or not +sufficiently distinct to be ranked at their first appearance as distinct +varieties, and whether or not two or more species or races have become +blended together by crossing, may plainly be recognised in the increased +size and beauty which we now see in the varieties of the heartsease, +rose, pelargonium, dahlia, and other plants, when compared with the +older varieties or with their parent-stocks. No one would ever expect to +get a first-rate heartsease or dahlia from the seed of a wild plant. No +one would expect to raise a first-rate melting pear from the seed of a +wild pear, though he might succeed from a poor seedling growing wild, if +it had come from a garden-stock. The pear, though cultivated in +classical times, appears, from Pliny’s description, to have been a fruit +of very inferior quality. I have seen great surprise expressed in +horticultural works at the wonderful skill of gardeners, in having +produced such splendid results from such poor materials; but the art, I +cannot doubt, has been simple, and, as far as the final result is +concerned, has been followed almost unconsciously. It has consisted in +always cultivating the best known variety, sowing its seeds, and, when a +slightly better variety has chanced to appear, selecting it, and so +onwards. But the gardeners of the classical period, who cultivated the +best pear they could procure, never thought what splendid fruit we +should eat; though we owe our excellent fruit, in some small degree, to +their having naturally chosen and preserved the best varieties they +could anywhere find. A large amount of change in our cultivated plants, thus slowly and -unconsciously accumulated, explains, as I believe, the well-known fact, that in -a vast number of cases we cannot recognise, and therefore do not know, the wild -parent-stocks of the plants which have been longest cultivated in our flower -and kitchen gardens. If it has taken centuries or thousands of years to improve -or modify most of our plants up to their present standard of usefulness to man, -we can understand how it is that neither Australia, the Cape of Good Hope, nor -any other region inhabited by quite uncivilised man, has afforded us a single -plant worth culture. It is not that these countries, so rich in species, do not -by a strange chance possess the aboriginal stocks of any useful plants, but -that the native plants have not been improved by continued selection up to a -standard of perfection comparable with that given to the plants in countries -anciently civilised. - -In regard to the domestic animals kept by uncivilised man, it should not be -overlooked that they almost always have to struggle for their own food, at -least during certain seasons. And in two countries very differently -circumstanced, individuals of the same species, having slightly different -constitutions or structure, would often succeed better in the one country than -in the other, and thus by a process of “natural selection,” as will hereafter -be more fully explained, two sub-breeds might be formed. This, perhaps, partly -explains what has been remarked by some authors, namely, that the varieties -kept by savages have more of the character of species than the varieties kept -in civilised countries. - -On the view here given of the all-important part which selection by man has -played, it becomes at once obvious, how it is that our domestic races show -adaptation in their structure or in their habits to man’s wants or fancies. We -can, I think, further understand the frequently abnormal character of our -domestic races, and likewise their differences being so great in external -characters and relatively so slight in internal parts or organs. Man can hardly -select, or only with much difficulty, any deviation of structure excepting such -as is externally visible; and indeed he rarely cares for what is internal. He -can never act by selection, excepting on variations which are first given to -him in some slight degree by nature. No man would ever try to make a fantail, -till he saw a pigeon with a tail developed in some slight degree in an unusual -manner, or a pouter till he saw a pigeon with a crop of somewhat unusual size; -and the more abnormal or unusual any character was when it first appeared, the -more likely it would be to catch his attention. But to use such an expression -as trying to make a fantail, is, I have no doubt, in most cases, utterly -incorrect. The man who first selected a pigeon with a slightly larger tail, -never dreamed what the descendants of that pigeon would become through -long-continued, partly unconscious and partly methodical selection. Perhaps the -parent bird of all fantails had only fourteen tail-feathers somewhat expanded, +unconsciously accumulated, explains, as I believe, the well-known fact, +that in a vast number of cases we cannot recognise, and therefore do not +know, the wild parent-stocks of the plants which have been longest +cultivated in our flower and kitchen gardens. If it has taken centuries +or thousands of years to improve or modify most of our plants up to +their present standard of usefulness to man, we can understand how it is +that neither Australia, the Cape of Good Hope, nor any other region +inhabited by quite uncivilised man, has afforded us a single plant worth +culture. It is not that these countries, so rich in species, do not by a +strange chance possess the aboriginal stocks of any useful plants, but +that the native plants have not been improved by continued selection up +to a standard of perfection comparable with that given to the plants in +countries anciently civilised. + +In regard to the domestic animals kept by uncivilised man, it should not +be overlooked that they almost always have to struggle for their own +food, at least during certain seasons. And in two countries very +differently circumstanced, individuals of the same species, having +slightly different constitutions or structure, would often succeed +better in the one country than in the other, and thus by a process of +“natural selection,” as will hereafter be more fully explained, two +sub-breeds might be formed. This, perhaps, partly explains what has been +remarked by some authors, namely, that the varieties kept by savages +have more of the character of species than the varieties kept in +civilised countries. + +On the view here given of the all-important part which selection by man +has played, it becomes at once obvious, how it is that our domestic +races show adaptation in their structure or in their habits to man’s +wants or fancies. We can, I think, further understand the frequently +abnormal character of our domestic races, and likewise their differences +being so great in external characters and relatively so slight in +internal parts or organs. Man can hardly select, or only with much +difficulty, any deviation of structure excepting such as is externally +visible; and indeed he rarely cares for what is internal. He can never +act by selection, excepting on variations which are first given to him +in some slight degree by nature. No man would ever try to make a +fantail, till he saw a pigeon with a tail developed in some slight +degree in an unusual manner, or a pouter till he saw a pigeon with a +crop of somewhat unusual size; and the more abnormal or unusual any +character was when it first appeared, the more likely it would be to +catch his attention. But to use such an expression as trying to make a +fantail, is, I have no doubt, in most cases, utterly incorrect. The man +who first selected a pigeon with a slightly larger tail, never dreamed +what the descendants of that pigeon would become through long-continued, +partly unconscious and partly methodical selection. Perhaps the parent +bird of all fantails had only fourteen tail-feathers somewhat expanded, like the present Java fantail, or like individuals of other and distinct -breeds, in which as many as seventeen tail-feathers have been counted. Perhaps -the first pouter-pigeon did not inflate its crop much more than the turbit now -does the upper part of its oesophagus,—a habit which is disregarded by all -fanciers, as it is not one of the points of the breed. - -Nor let it be thought that some great deviation of structure would be necessary -to catch the fancier’s eye: he perceives extremely small differences, and it is -in human nature to value any novelty, however slight, in one’s own possession. -Nor must the value which would formerly be set on any slight differences in the -individuals of the same species, be judged of by the value which would now be -set on them, after several breeds have once fairly been established. Many -slight differences might, and indeed do now, arise amongst pigeons, which are -rejected as faults or deviations from the standard of perfection of each breed. -The common goose has not given rise to any marked varieties; hence the -Thoulouse and the common breed, which differ only in colour, that most fleeting -of characters, have lately been exhibited as distinct at our poultry-shows. - -I think these views further explain what has sometimes been noticed—namely that -we know nothing about the origin or history of any of our domestic breeds. But, -in fact, a breed, like a dialect of a language, can hardly be said to have had -a definite origin. A man preserves and breeds from an individual with some -slight deviation of structure, or takes more care than usual in matching his -best animals and thus improves them, and the improved individuals slowly spread -in the immediate neighbourhood. But as yet they will hardly have a distinct -name, and from being only slightly valued, their history will be disregarded. -When further improved by the same slow and gradual process, they will spread -more widely, and will get recognised as something distinct and valuable, and -will then probably first receive a provincial name. In semi-civilised -countries, with little free communication, the spreading and knowledge of any -new sub-breed will be a slow process. As soon as the points of value of the new -sub-breed are once fully acknowledged, the principle, as I have called it, of -unconscious selection will always tend,—perhaps more at one period than at -another, as the breed rises or falls in fashion,—perhaps more in one district -than in another, according to the state of civilisation of the -inhabitants—slowly to add to the characteristic features of the breed, whatever -they may be. But the chance will be infinitely small of any record having been -preserved of such slow, varying, and insensible changes. - -I must now say a few words on the circumstances, favourable, or the reverse, to -man’s power of selection. A high degree of variability is obviously favourable, -as freely giving the materials for selection to work on; not that mere -individual differences are not amply sufficient, with extreme care, to allow of -the accumulation of a large amount of modification in almost any desired -direction. But as variations manifestly useful or pleasing to man appear only -occasionally, the chance of their appearance will be much increased by a large -number of individuals being kept; and hence this comes to be of the highest -importance to success. On this principle Marshall has remarked, with respect to -the sheep of parts of Yorkshire, that “as they generally belong to poor people, -and are mostly in small lots, they never can be improved.” On the other hand, -nurserymen, from raising large stocks of the same plants, are generally far -more successful than amateurs in getting new and valuable varieties. The -keeping of a large number of individuals of a species in any country requires -that the species should be placed under favourable conditions of life, so as to -breed freely in that country. When the individuals of any species are scanty, -all the individuals, whatever their quality may be, will generally be allowed -to breed, and this will effectually prevent selection. But probably the most -important point of all, is, that the animal or plant should be so highly useful -to man, or so much valued by him, that the closest attention should be paid to -even the slightest deviation in the qualities or structure of each individual. -Unless such attention be paid nothing can be effected. I have seen it gravely -remarked, that it was most fortunate that the strawberry began to vary just -when gardeners began to attend closely to this plant. No doubt the strawberry -had always varied since it was cultivated, but the slight varieties had been -neglected. As soon, however, as gardeners picked out individual plants with -slightly larger, earlier, or better fruit, and raised seedlings from them, and -again picked out the best seedlings and bred from them, then, there appeared -(aided by some crossing with distinct species) those many admirable varieties -of the strawberry which have been raised during the last thirty or forty years. - -In the case of animals with separate sexes, facility in preventing crosses is -an important element of success in the formation of new races,—at least, in a -country which is already stocked with other races. In this respect enclosure of -the land plays a part. Wandering savages or the inhabitants of open plains -rarely possess more than one breed of the same species. Pigeons can be mated -for life, and this is a great convenience to the fancier, for thus many races -may be kept true, though mingled in the same aviary; and this circumstance must -have largely favoured the improvement and formation of new breeds. Pigeons, I -may add, can be propagated in great numbers and at a very quick rate, and -inferior birds may be freely rejected, as when killed they serve for food. On -the other hand, cats, from their nocturnal rambling habits, cannot be matched, -and, although so much valued by women and children, we hardly ever see a -distinct breed kept up; such breeds as we do sometimes see are almost always -imported from some other country, often from islands. Although I do not doubt -that some domestic animals vary less than others, yet the rarity or absence of -distinct breeds of the cat, the donkey, peacock, goose, etc., may be attributed -in main part to selection not having been brought into play: in cats, from the -difficulty in pairing them; in donkeys, from only a few being kept by poor -people, and little attention paid to their breeding; in peacocks, from not -being very easily reared and a large stock not kept; in geese, from being -valuable only for two purposes, food and feathers, and more especially from no -pleasure having been felt in the display of distinct breeds. - -To sum up on the origin of our Domestic Races of animals and plants. I believe -that the conditions of life, from their action on the reproductive system, are -so far of the highest importance as causing variability. I do not believe that -variability is an inherent and necessary contingency, under all circumstances, -with all organic beings, as some authors have thought. The effects of -variability are modified by various degrees of inheritance and of reversion. -Variability is governed by many unknown laws, more especially by that of -correlation of growth. Something may be attributed to the direct action of the -conditions of life. Something must be attributed to use and disuse. The final -result is thus rendered infinitely complex. In some cases, I do not doubt that -the intercrossing of species, aboriginally distinct, has played an important -part in the origin of our domestic productions. When in any country several -domestic breeds have once been established, their occasional intercrossing, -with the aid of selection, has, no doubt, largely aided in the formation of new -sub-breeds; but the importance of the crossing of varieties has, I believe, -been greatly exaggerated, both in regard to animals and to those plants which -are propagated by seed. In plants which are temporarily propagated by cuttings, -buds, etc., the importance of the crossing both of distinct species and of -varieties is immense; for the cultivator here quite disregards the extreme +breeds, in which as many as seventeen tail-feathers have been counted. +Perhaps the first pouter-pigeon did not inflate its crop much more than +the turbit now does the upper part of its oesophagus,—a habit which is +disregarded by all fanciers, as it is not one of the points of the +breed. + +Nor let it be thought that some great deviation of structure would be +necessary to catch the fancier’s eye: he perceives extremely small +differences, and it is in human nature to value any novelty, however +slight, in one’s own possession. Nor must the value which would +formerly be set on any slight differences in the individuals of the same +species, be judged of by the value which would now be set on them, after +several breeds have once fairly been established. Many slight +differences might, and indeed do now, arise amongst pigeons, which are +rejected as faults or deviations from the standard of perfection of each +breed. The common goose has not given rise to any marked varieties; +hence the Thoulouse and the common breed, which differ only in colour, +that most fleeting of characters, have lately been exhibited as distinct +at our poultry-shows. + +I think these views further explain what has sometimes been +noticed—namely that we know nothing about the origin or history of any +of our domestic breeds. But, in fact, a breed, like a dialect of a +language, can hardly be said to have had a definite origin. A man +preserves and breeds from an individual with some slight deviation of +structure, or takes more care than usual in matching his best animals +and thus improves them, and the improved individuals slowly spread in +the immediate neighbourhood. But as yet they will hardly have a distinct +name, and from being only slightly valued, their history will be +disregarded. When further improved by the same slow and gradual +process, they will spread more widely, and will get recognised as +something distinct and valuable, and will then probably first receive a +provincial name. In semi-civilised countries, with little free +communication, the spreading and knowledge of any new sub-breed will be +a slow process. As soon as the points of value of the new sub-breed are +once fully acknowledged, the principle, as I have called it, of +unconscious selection will always tend,—perhaps more at one period than +at another, as the breed rises or falls in fashion,—perhaps more in one +district than in another, according to the state of civilisation of the +inhabitants—slowly to add to the characteristic features of the breed, +whatever they may be. But the chance will be infinitely small of any +record having been preserved of such slow, varying, and insensible +changes. + +I must now say a few words on the circumstances, favourable, or the +reverse, to man’s power of selection. A high degree of variability is +obviously favourable, as freely giving the materials for selection to +work on; not that mere individual differences are not amply sufficient, +with extreme care, to allow of the accumulation of a large amount of +modification in almost any desired direction. But as variations +manifestly useful or pleasing to man appear only occasionally, the +chance of their appearance will be much increased by a large number of +individuals being kept; and hence this comes to be of the highest +importance to success. On this principle Marshall has remarked, with +respect to the sheep of parts of Yorkshire, that “as they generally +belong to poor people, and are mostly in small lots, they never can be +improved.” On the other hand, nurserymen, from raising large stocks of +the same plants, are generally far more successful than amateurs in +getting new and valuable varieties. The keeping of a large number of +individuals of a species in any country requires that the species should +be placed under favourable conditions of life, so as to breed freely in +that country. When the individuals of any species are scanty, all the +individuals, whatever their quality may be, will generally be allowed to +breed, and this will effectually prevent selection. But probably the +most important point of all, is, that the animal or plant should be so +highly useful to man, or so much valued by him, that the closest +attention should be paid to even the slightest deviation in the +qualities or structure of each individual. Unless such attention be +paid nothing can be effected. I have seen it gravely remarked, that it +was most fortunate that the strawberry began to vary just when gardeners +began to attend closely to this plant. No doubt the strawberry had +always varied since it was cultivated, but the slight varieties had been +neglected. As soon, however, as gardeners picked out individual plants +with slightly larger, earlier, or better fruit, and raised seedlings +from them, and again picked out the best seedlings and bred from them, +then, there appeared (aided by some crossing with distinct species) +those many admirable varieties of the strawberry which have been raised +during the last thirty or forty years. + +In the case of animals with separate sexes, facility in preventing +crosses is an important element of success in the formation of new +races,—at least, in a country which is already stocked with other races. +In this respect enclosure of the land plays a part. Wandering savages or +the inhabitants of open plains rarely possess more than one breed of the +same species. Pigeons can be mated for life, and this is a great +convenience to the fancier, for thus many races may be kept true, though +mingled in the same aviary; and this circumstance must have largely +favoured the improvement and formation of new breeds. Pigeons, I may +add, can be propagated in great numbers and at a very quick rate, and +inferior birds may be freely rejected, as when killed they serve for +food. On the other hand, cats, from their nocturnal rambling habits, +cannot be matched, and, although so much valued by women and children, +we hardly ever see a distinct breed kept up; such breeds as we do +sometimes see are almost always imported from some other country, often +from islands. Although I do not doubt that some domestic animals vary +less than others, yet the rarity or absence of distinct breeds of the +cat, the donkey, peacock, goose, etc., may be attributed in main part to +selection not having been brought into play: in cats, from the +difficulty in pairing them; in donkeys, from only a few being kept by +poor people, and little attention paid to their breeding; in peacocks, +from not being very easily reared and a large stock not kept; in geese, +from being valuable only for two purposes, food and feathers, and more +especially from no pleasure having been felt in the display of distinct +breeds. + +To sum up on the origin of our Domestic Races of animals and plants. I +believe that the conditions of life, from their action on the +reproductive system, are so far of the highest importance as causing +variability. I do not believe that variability is an inherent and +necessary contingency, under all circumstances, with all organic beings, +as some authors have thought. The effects of variability are modified by +various degrees of inheritance and of reversion. Variability is +governed by many unknown laws, more especially by that of correlation of +growth. Something may be attributed to the direct action of the +conditions of life. Something must be attributed to use and disuse. The +final result is thus rendered infinitely complex. In some cases, I do +not doubt that the intercrossing of species, aboriginally distinct, has +played an important part in the origin of our domestic productions. When +in any country several domestic breeds have once been established, their +occasional intercrossing, with the aid of selection, has, no doubt, +largely aided in the formation of new sub-breeds; but the importance of +the crossing of varieties has, I believe, been greatly exaggerated, both +in regard to animals and to those plants which are propagated by seed. +In plants which are temporarily propagated by cuttings, buds, etc., the +importance of the crossing both of distinct species and of varieties is +immense; for the cultivator here quite disregards the extreme variability both of hybrids and mongrels, and the frequent sterility of hybrids; but the cases of plants not propagated by seed are of little -importance to us, for their endurance is only temporary. Over all these causes -of Change I am convinced that the accumulative action of Selection, whether -applied methodically and more quickly, or unconsciously and more slowly, but -more efficiently, is by far the predominant Power. - -CHAPTER II. -VARIATION UNDER NATURE. - -Variability. Individual differences. Doubtful species. Wide ranging, much -diffused, and common species vary most. Species of the larger genera in any -country vary more than the species of the smaller genera. Many of the species -of the larger genera resemble varieties in being very closely, but unequally, -related to each other, and in having restricted ranges. - -Before applying the principles arrived at in the last chapter to organic beings -in a state of nature, we must briefly discuss whether these latter are subject -to any variation. To treat this subject at all properly, a long catalogue of -dry facts should be given; but these I shall reserve for my future work. Nor -shall I here discuss the various definitions which have been given of the term -species. No one definition has as yet satisfied all naturalists; yet every -naturalist knows vaguely what he means when he speaks of a species. Generally -the term includes the unknown element of a distinct act of creation. The term -“variety” is almost equally difficult to define; but here community of descent -is almost universally implied, though it can rarely be proved. We have also +importance to us, for their endurance is only temporary. Over all these +causes of Change I am convinced that the accumulative action of +Selection, whether applied methodically and more quickly, or +unconsciously and more slowly, but more efficiently, is by far the +predominant Power. + +CHAPTER II. VARIATION UNDER NATURE. + +Variability. Individual differences. Doubtful species. Wide ranging, +much diffused, and common species vary most. Species of the larger +genera in any country vary more than the species of the smaller genera. +Many of the species of the larger genera resemble varieties in being +very closely, but unequally, related to each other, and in having +restricted ranges. + +Before applying the principles arrived at in the last chapter to organic +beings in a state of nature, we must briefly discuss whether these +latter are subject to any variation. To treat this subject at all +properly, a long catalogue of dry facts should be given; but these I +shall reserve for my future work. Nor shall I here discuss the various +definitions which have been given of the term species. No one definition +has as yet satisfied all naturalists; yet every naturalist knows vaguely +what he means when he speaks of a species. Generally the term includes +the unknown element of a distinct act of creation. The term “variety” is +almost equally difficult to define; but here community of descent is +almost universally implied, though it can rarely be proved. We have also what are called monstrosities; but they graduate into varieties. By a -monstrosity I presume is meant some considerable deviation of structure in one -part, either injurious to or not useful to the species, and not generally -propagated. Some authors use the term “variation” in a technical sense, as -implying a modification directly due to the physical conditions of life; and -“variations” in this sense are supposed not to be inherited: but who can say -that the dwarfed condition of shells in the brackish waters of the Baltic, or -dwarfed plants on Alpine summits, or the thicker fur of an animal from far -northwards, would not in some cases be inherited for at least some few -generations? and in this case I presume that the form would be called a -variety. +monstrosity I presume is meant some considerable deviation of structure +in one part, either injurious to or not useful to the species, and not +generally propagated. Some authors use the term “variation” in a +technical sense, as implying a modification directly due to the physical +conditions of life; and “variations” in this sense are supposed not to +be inherited: but who can say that the dwarfed condition of shells in +the brackish waters of the Baltic, or dwarfed plants on Alpine summits, +or the thicker fur of an animal from far northwards, would not in some +cases be inherited for at least some few generations? and in this case I +presume that the form would be called a variety. Again, we have many slight differences which may be called individual -differences, such as are known frequently to appear in the offspring from the -same parents, or which may be presumed to have thus arisen, from being -frequently observed in the individuals of the same species inhabiting the same -confined locality. No one supposes that all the individuals of the same species -are cast in the very same mould. These individual differences are highly -important for us, as they afford materials for natural selection to accumulate, -in the same manner as man can accumulate in any given direction individual -differences in his domesticated productions. These individual differences -generally affect what naturalists consider unimportant parts; but I could show -by a long catalogue of facts, that parts which must be called important, -whether viewed under a physiological or classificatory point of view, sometimes -vary in the individuals of the same species. I am convinced that the most -experienced naturalist would be surprised at the number of the cases of -variability, even in important parts of structure, which he could collect on -good authority, as I have collected, during a course of years. It should be -remembered that systematists are far from pleased at finding variability in -important characters, and that there are not many men who will laboriously -examine internal and important organs, and compare them in many specimens of -the same species. I should never have expected that the branching of the main -nerves close to the great central ganglion of an insect would have been -variable in the same species; I should have expected that changes of this -nature could have been effected only by slow degrees: yet quite recently Mr. -Lubbock has shown a degree of variability in these main nerves in Coccus, which -may almost be compared to the irregular branching of the stem of a tree. This -philosophical naturalist, I may add, has also quite recently shown that the -muscles in the larvæ of certain insects are very far from uniform. Authors -sometimes argue in a circle when they state that important organs never vary; -for these same authors practically rank that character as important (as some -few naturalists have honestly confessed) which does not vary; and, under this -point of view, no instance of an important part varying will ever be found: but -under any other point of view many instances assuredly can be given. - -There is one point connected with individual differences, which seems to me -extremely perplexing: I refer to those genera which have sometimes been called -“protean” or “polymorphic,” in which the species present an inordinate amount -of variation; and hardly two naturalists can agree which forms to rank as -species and which as varieties. We may instance Rubus, Rosa, and Hieracium -amongst plants, several genera of insects, and several genera of Brachiopod -shells. In most polymorphic genera some of the species have fixed and definite -characters. Genera which are polymorphic in one country seem to be, with some -few exceptions, polymorphic in other countries, and likewise, judging from -Brachiopod shells, at former periods of time. These facts seem to be very -perplexing, for they seem to show that this kind of variability is independent -of the conditions of life. I am inclined to suspect that we see in these -polymorphic genera variations in points of structure which are of no service or -disservice to the species, and which consequently have not been seized on and -rendered definite by natural selection, as hereafter will be explained. - -Those forms which possess in some considerable degree the character of species, -but which are so closely similar to some other forms, or are so closely linked -to them by intermediate gradations, that naturalists do not like to rank them -as distinct species, are in several respects the most important for us. We have -every reason to believe that many of these doubtful and closely-allied forms -have permanently retained their characters in their own country for a long -time; for as long, as far as we know, as have good and true species. -Practically, when a naturalist can unite two forms together by others having -intermediate characters, he treats the one as a variety of the other, ranking -the most common, but sometimes the one first described, as the species, and the -other as the variety. But cases of great difficulty, which I will not here -enumerate, sometimes occur in deciding whether or not to rank one form as a -variety of another, even when they are closely connected by intermediate links; -nor will the commonly-assumed hybrid nature of the intermediate links always -remove the difficulty. In very many cases, however, one form is ranked as a -variety of another, not because the intermediate links have actually been -found, but because analogy leads the observer to suppose either that they do -now somewhere exist, or may formerly have existed; and here a wide door for the -entry of doubt and conjecture is opened. +differences, such as are known frequently to appear in the offspring +from the same parents, or which may be presumed to have thus arisen, +from being frequently observed in the individuals of the same species +inhabiting the same confined locality. No one supposes that all the +individuals of the same species are cast in the very same mould. These +individual differences are highly important for us, as they afford +materials for natural selection to accumulate, in the same manner as man +can accumulate in any given direction individual differences in his +domesticated productions. These individual differences generally affect +what naturalists consider unimportant parts; but I could show by a long +catalogue of facts, that parts which must be called important, whether +viewed under a physiological or classificatory point of view, sometimes +vary in the individuals of the same species. I am convinced that the +most experienced naturalist would be surprised at the number of the +cases of variability, even in important parts of structure, which he +could collect on good authority, as I have collected, during a course of +years. It should be remembered that systematists are far from pleased at +finding variability in important characters, and that there are not many +men who will laboriously examine internal and important organs, and +compare them in many specimens of the same species. I should never have +expected that the branching of the main nerves close to the great +central ganglion of an insect would have been variable in the same +species; I should have expected that changes of this nature could have +been effected only by slow degrees: yet quite recently Mr. Lubbock has +shown a degree of variability in these main nerves in Coccus, which may +almost be compared to the irregular branching of the stem of a tree. +This philosophical naturalist, I may add, has also quite recently shown +that the muscles in the larvæ of certain insects are very far from +uniform. Authors sometimes argue in a circle when they state that +important organs never vary; for these same authors practically rank +that character as important (as some few naturalists have honestly +confessed) which does not vary; and, under this point of view, no +instance of an important part varying will ever be found: but under any +other point of view many instances assuredly can be given. + +There is one point connected with individual differences, which seems to +me extremely perplexing: I refer to those genera which have sometimes +been called “protean” or “polymorphic,” in which the species present an +inordinate amount of variation; and hardly two naturalists can agree +which forms to rank as species and which as varieties. We may instance +Rubus, Rosa, and Hieracium amongst plants, several genera of insects, +and several genera of Brachiopod shells. In most polymorphic genera some +of the species have fixed and definite characters. Genera which are +polymorphic in one country seem to be, with some few exceptions, +polymorphic in other countries, and likewise, judging from Brachiopod +shells, at former periods of time. These facts seem to be very +perplexing, for they seem to show that this kind of variability is +independent of the conditions of life. I am inclined to suspect that we +see in these polymorphic genera variations in points of structure which +are of no service or disservice to the species, and which consequently +have not been seized on and rendered definite by natural selection, as +hereafter will be explained. + +Those forms which possess in some considerable degree the character of +species, but which are so closely similar to some other forms, or are so +closely linked to them by intermediate gradations, that naturalists do +not like to rank them as distinct species, are in several respects the +most important for us. We have every reason to believe that many of +these doubtful and closely-allied forms have permanently retained their +characters in their own country for a long time; for as long, as far as +we know, as have good and true species. Practically, when a naturalist +can unite two forms together by others having intermediate characters, +he treats the one as a variety of the other, ranking the most common, +but sometimes the one first described, as the species, and the other as +the variety. But cases of great difficulty, which I will not here +enumerate, sometimes occur in deciding whether or not to rank one form +as a variety of another, even when they are closely connected by +intermediate links; nor will the commonly-assumed hybrid nature of the +intermediate links always remove the difficulty. In very many cases, +however, one form is ranked as a variety of another, not because the +intermediate links have actually been found, but because analogy leads +the observer to suppose either that they do now somewhere exist, or may +formerly have existed; and here a wide door for the entry of doubt and +conjecture is opened. Hence, in determining whether a form should be ranked as a species or a -variety, the opinion of naturalists having sound judgment and wide experience -seems the only guide to follow. We must, however, in many cases, decide by a -majority of naturalists, for few well-marked and well-known varieties can be -named which have not been ranked as species by at least some competent judges. +variety, the opinion of naturalists having sound judgment and wide +experience seems the only guide to follow. We must, however, in many +cases, decide by a majority of naturalists, for few well-marked and +well-known varieties can be named which have not been ranked as species +by at least some competent judges. That varieties of this doubtful nature are far from uncommon cannot be -disputed. Compare the several floras of Great Britain, of France or of the -United States, drawn up by different botanists, and see what a surprising -number of forms have been ranked by one botanist as good species, and by -another as mere varieties. Mr. H. C. Watson, to whom I lie under deep -obligation for assistance of all kinds, has marked for me 182 British plants, -which are generally considered as varieties, but which have all been ranked by -botanists as species; and in making this list he has omitted many trifling -varieties, but which nevertheless have been ranked by some botanists as -species, and he has entirely omitted several highly polymorphic genera. Under -genera, including the most polymorphic forms, Mr. Babington gives 251 species, -whereas Mr. Bentham gives only 112,—a difference of 139 doubtful forms! Amongst -animals which unite for each birth, and which are highly locomotive, doubtful -forms, ranked by one zoologist as a species and by another as a variety, can -rarely be found within the same country, but are common in separated areas. How -many of those birds and insects in North America and Europe, which differ very -slightly from each other, have been ranked by one eminent naturalist as -undoubted species, and by another as varieties, or, as they are often called, -as geographical races! Many years ago, when comparing, and seeing others -compare, the birds from the separate islands of the Galapagos Archipelago, both -one with another, and with those from the American mainland, I was much struck -how entirely vague and arbitrary is the distinction between species and -varieties. On the islets of the little Madeira group there are many insects -which are characterized as varieties in Mr. Wollaston’s admirable work, but -which it cannot be doubted would be ranked as distinct species by many +disputed. Compare the several floras of Great Britain, of France or of +the United States, drawn up by different botanists, and see what a +surprising number of forms have been ranked by one botanist as good +species, and by another as mere varieties. Mr. H. C. Watson, to whom I +lie under deep obligation for assistance of all kinds, has marked for me +182 British plants, which are generally considered as varieties, but +which have all been ranked by botanists as species; and in making this +list he has omitted many trifling varieties, but which nevertheless have +been ranked by some botanists as species, and he has entirely omitted +several highly polymorphic genera. Under genera, including the most +polymorphic forms, Mr. Babington gives 251 species, whereas Mr. Bentham +gives only 112,—a difference of 139 doubtful forms! Amongst animals +which unite for each birth, and which are highly locomotive, doubtful +forms, ranked by one zoologist as a species and by another as a variety, +can rarely be found within the same country, but are common in separated +areas. How many of those birds and insects in North America and Europe, +which differ very slightly from each other, have been ranked by one +eminent naturalist as undoubted species, and by another as varieties, +or, as they are often called, as geographical races! Many years ago, +when comparing, and seeing others compare, the birds from the separate +islands of the Galapagos Archipelago, both one with another, and with +those from the American mainland, I was much struck how entirely vague +and arbitrary is the distinction between species and varieties. On the +islets of the little Madeira group there are many insects which are +characterized as varieties in Mr. Wollaston’s admirable work, but which +it cannot be doubted would be ranked as distinct species by many entomologists. Even Ireland has a few animals, now generally regarded as -varieties, but which have been ranked as species by some zoologists. Several -most experienced ornithologists consider our British red grouse as only a -strongly-marked race of a Norwegian species, whereas the greater number rank it -as an undoubted species peculiar to Great Britain. A wide distance between the -homes of two doubtful forms leads many naturalists to rank both as distinct -species; but what distance, it has been well asked, will suffice? if that -between America and Europe is ample, will that between the Continent and the -Azores, or Madeira, or the Canaries, or Ireland, be sufficient? It must be -admitted that many forms, considered by highly-competent judges as varieties, -have so perfectly the character of species that they are ranked by other -highly-competent judges as good and true species. But to discuss whether they -are rightly called species or varieties, before any definition of these terms -has been generally accepted, is vainly to beat the air. - -Many of the cases of strongly-marked varieties or doubtful species well deserve -consideration; for several interesting lines of argument, from geographical -distribution, analogical variation, hybridism, etc., have been brought to bear -on the attempt to determine their rank. I will here give only a single -instance,—the well-known one of the primrose and cowslip, or Primula veris and -elatior. These plants differ considerably in appearance; they have a different -flavour and emit a different odour; they flower at slightly different periods; -they grow in somewhat different stations; they ascend mountains to different -heights; they have different geographical ranges; and lastly, according to very -numerous experiments made during several years by that most careful observer -Gärtner, they can be crossed only with much difficulty. We could hardly wish -for better evidence of the two forms being specifically distinct. On the other -hand, they are united by many intermediate links, and it is very doubtful -whether these links are hybrids; and there is, as it seems to me, an -overwhelming amount of experimental evidence, showing that they descend from -common parents, and consequently must be ranked as varieties. - -Close investigation, in most cases, will bring naturalists to an agreement how -to rank doubtful forms. Yet it must be confessed, that it is in the best-known -countries that we find the greatest number of forms of doubtful value. I have -been struck with the fact, that if any animal or plant in a state of nature be -highly useful to man, or from any cause closely attract his attention, -varieties of it will almost universally be found recorded. These varieties, -moreover, will be often ranked by some authors as species. Look at the common -oak, how closely it has been studied; yet a German author makes more than a -dozen species out of forms, which are very generally considered as varieties; -and in this country the highest botanical authorities and practical men can be -quoted to show that the sessile and pedunculated oaks are either good and -distinct species or mere varieties. - -When a young naturalist commences the study of a group of organisms quite -unknown to him, he is at first much perplexed to determine what differences to -consider as specific, and what as varieties; for he knows nothing of the amount -and kind of variation to which the group is subject; and this shows, at least, -how very generally there is some variation. But if he confine his attention to -one class within one country, he will soon make up his mind how to rank most of -the doubtful forms. His general tendency will be to make many species, for he -will become impressed, just like the pigeon or poultry-fancier before alluded +varieties, but which have been ranked as species by some zoologists. +Several most experienced ornithologists consider our British red grouse +as only a strongly-marked race of a Norwegian species, whereas the +greater number rank it as an undoubted species peculiar to Great +Britain. A wide distance between the homes of two doubtful forms leads +many naturalists to rank both as distinct species; but what distance, it +has been well asked, will suffice? if that between America and Europe is +ample, will that between the Continent and the Azores, or Madeira, or +the Canaries, or Ireland, be sufficient? It must be admitted that many +forms, considered by highly-competent judges as varieties, have so +perfectly the character of species that they are ranked by other +highly-competent judges as good and true species. But to discuss whether +they are rightly called species or varieties, before any definition of +these terms has been generally accepted, is vainly to beat the air. + +Many of the cases of strongly-marked varieties or doubtful species well +deserve consideration; for several interesting lines of argument, from +geographical distribution, analogical variation, hybridism, etc., have +been brought to bear on the attempt to determine their rank. I will here +give only a single instance,—the well-known one of the primrose and +cowslip, or Primula veris and elatior. These plants differ considerably +in appearance; they have a different flavour and emit a different odour; +they flower at slightly different periods; they grow in somewhat +different stations; they ascend mountains to different heights; they +have different geographical ranges; and lastly, according to very +numerous experiments made during several years by that most careful +observer Gärtner, they can be crossed only with much difficulty. We +could hardly wish for better evidence of the two forms being +specifically distinct. On the other hand, they are united by many +intermediate links, and it is very doubtful whether these links are +hybrids; and there is, as it seems to me, an overwhelming amount of +experimental evidence, showing that they descend from common parents, +and consequently must be ranked as varieties. + +Close investigation, in most cases, will bring naturalists to an +agreement how to rank doubtful forms. Yet it must be confessed, that it +is in the best-known countries that we find the greatest number of forms +of doubtful value. I have been struck with the fact, that if any animal +or plant in a state of nature be highly useful to man, or from any cause +closely attract his attention, varieties of it will almost universally +be found recorded. These varieties, moreover, will be often ranked by +some authors as species. Look at the common oak, how closely it has been +studied; yet a German author makes more than a dozen species out of +forms, which are very generally considered as varieties; and in this +country the highest botanical authorities and practical men can be +quoted to show that the sessile and pedunculated oaks are either good +and distinct species or mere varieties. + +When a young naturalist commences the study of a group of organisms +quite unknown to him, he is at first much perplexed to determine what +differences to consider as specific, and what as varieties; for he knows +nothing of the amount and kind of variation to which the group is +subject; and this shows, at least, how very generally there is some +variation. But if he confine his attention to one class within one +country, he will soon make up his mind how to rank most of the doubtful +forms. His general tendency will be to make many species, for he will +become impressed, just like the pigeon or poultry-fancier before alluded to, with the amount of difference in the forms which he is continually -studying; and he has little general knowledge of analogical variation in other -groups and in other countries, by which to correct his first impressions. As he -extends the range of his observations, he will meet with more cases of -difficulty; for he will encounter a greater number of closely-allied forms. But -if his observations be widely extended, he will in the end generally be enabled -to make up his own mind which to call varieties and which species; but he will -succeed in this at the expense of admitting much variation,—and the truth of -this admission will often be disputed by other naturalists. When, moreover, he -comes to study allied forms brought from countries not now continuous, in which -case he can hardly hope to find the intermediate links between his doubtful -forms, he will have to trust almost entirely to analogy, and his difficulties -will rise to a climax. - -Certainly no clear line of demarcation has as yet been drawn between species -and sub-species—that is, the forms which in the opinion of some naturalists -come very near to, but do not quite arrive at the rank of species; or, again, -between sub-species and well-marked varieties, or between lesser varieties and -individual differences. These differences blend into each other in an -insensible series; and a series impresses the mind with the idea of an actual -passage. +studying; and he has little general knowledge of analogical variation in +other groups and in other countries, by which to correct his first +impressions. As he extends the range of his observations, he will meet +with more cases of difficulty; for he will encounter a greater number of +closely-allied forms. But if his observations be widely extended, he +will in the end generally be enabled to make up his own mind which to +call varieties and which species; but he will succeed in this at the +expense of admitting much variation,—and the truth of this admission +will often be disputed by other naturalists. When, moreover, he comes to +study allied forms brought from countries not now continuous, in which +case he can hardly hope to find the intermediate links between his +doubtful forms, he will have to trust almost entirely to analogy, and +his difficulties will rise to a climax. + +Certainly no clear line of demarcation has as yet been drawn between +species and sub-species—that is, the forms which in the opinion of some +naturalists come very near to, but do not quite arrive at the rank of +species; or, again, between sub-species and well-marked varieties, or +between lesser varieties and individual differences. These differences +blend into each other in an insensible series; and a series impresses +the mind with the idea of an actual passage. Hence I look at individual differences, though of small interest to the -systematist, as of high importance for us, as being the first step towards such -slight varieties as are barely thought worth recording in works on natural -history. And I look at varieties which are in any degree more distinct and -permanent, as steps leading to more strongly marked and more permanent -varieties; and at these latter, as leading to sub-species, and to species. The -passage from one stage of difference to another and higher stage may be, in -some cases, due merely to the long-continued action of different physical -conditions in two different regions; but I have not much faith in this view; -and I attribute the passage of a variety, from a state in which it differs very -slightly from its parent to one in which it differs more, to the action of -natural selection in accumulating (as will hereafter be more fully explained) -differences of structure in certain definite directions. Hence I believe a -well-marked variety may be justly called an incipient species; but whether this -belief be justifiable must be judged of by the general weight of the several -facts and views given throughout this work. - -It need not be supposed that all varieties or incipient species necessarily -attain the rank of species. They may whilst in this incipient state become -extinct, or they may endure as varieties for very long periods, as has been -shown to be the case by Mr. Wollaston with the varieties of certain fossil -land-shells in Madeira. If a variety were to flourish so as to exceed in -numbers the parent species, it would then rank as the species, and the species -as the variety; or it might come to supplant and exterminate the parent -species; or both might co-exist, and both rank as independent species. But we -shall hereafter have to return to this subject. - -From these remarks it will be seen that I look at the term species, as one -arbitrarily given for the sake of convenience to a set of individuals closely -resembling each other, and that it does not essentially differ from the term -variety, which is given to less distinct and more fluctuating forms. The term -variety, again, in comparison with mere individual differences, is also applied +systematist, as of high importance for us, as being the first step +towards such slight varieties as are barely thought worth recording in +works on natural history. And I look at varieties which are in any +degree more distinct and permanent, as steps leading to more strongly +marked and more permanent varieties; and at these latter, as leading to +sub-species, and to species. The passage from one stage of difference to +another and higher stage may be, in some cases, due merely to the +long-continued action of different physical conditions in two different +regions; but I have not much faith in this view; and I attribute the +passage of a variety, from a state in which it differs very slightly +from its parent to one in which it differs more, to the action of +natural selection in accumulating (as will hereafter be more fully +explained) differences of structure in certain definite directions. +Hence I believe a well-marked variety may be justly called an incipient +species; but whether this belief be justifiable must be judged of by the +general weight of the several facts and views given throughout this +work. + +It need not be supposed that all varieties or incipient species +necessarily attain the rank of species. They may whilst in this +incipient state become extinct, or they may endure as varieties for very +long periods, as has been shown to be the case by Mr. Wollaston with the +varieties of certain fossil land-shells in Madeira. If a variety were to +flourish so as to exceed in numbers the parent species, it would then +rank as the species, and the species as the variety; or it might come to +supplant and exterminate the parent species; or both might co-exist, and +both rank as independent species. But we shall hereafter have to return +to this subject. + +From these remarks it will be seen that I look at the term species, as +one arbitrarily given for the sake of convenience to a set of +individuals closely resembling each other, and that it does not +essentially differ from the term variety, which is given to less +distinct and more fluctuating forms. The term variety, again, in +comparison with mere individual differences, is also applied arbitrarily, and for mere convenience sake. -Guided by theoretical considerations, I thought that some interesting results -might be obtained in regard to the nature and relations of the species which -vary most, by tabulating all the varieties in several well-worked floras. At -first this seemed a simple task; but Mr. H. C. Watson, to whom I am much -indebted for valuable advice and assistance on this subject, soon convinced me -that there were many difficulties, as did subsequently Dr. Hooker, even in -stronger terms. I shall reserve for my future work the discussion of these -difficulties, and the tables themselves of the proportional numbers of the -varying species. Dr. Hooker permits me to add, that after having carefully read -my manuscript, and examined the tables, he thinks that the following statements -are fairly well established. The whole subject, however, treated as it -necessarily here is with much brevity, is rather perplexing, and allusions -cannot be avoided to the “struggle for existence,” “divergence of character,” -and other questions, hereafter to be discussed. - -Alph. De Candolle and others have shown that plants which have very wide ranges -generally present varieties; and this might have been expected, as they become -exposed to diverse physical conditions, and as they come into competition -(which, as we shall hereafter see, is a far more important circumstance) with -different sets of organic beings. But my tables further show that, in any -limited country, the species which are most common, that is abound most in -individuals, and the species which are most widely diffused within their own -country (and this is a different consideration from wide range, and to a -certain extent from commonness), often give rise to varieties sufficiently -well-marked to have been recorded in botanical works. Hence it is the most -flourishing, or, as they may be called, the dominant species,—those which range -widely over the world, are the most diffused in their own country, and are the -most numerous in individuals,—which oftenest produce well-marked varieties, or, -as I consider them, incipient species. And this, perhaps, might have been -anticipated; for, as varieties, in order to become in any degree permanent, -necessarily have to struggle with the other inhabitants of the country, the -species which are already dominant will be the most likely to yield offspring -which, though in some slight degree modified, will still inherit those -advantages that enabled their parents to become dominant over their -compatriots. - -If the plants inhabiting a country and described in any Flora be divided into -two equal masses, all those in the larger genera being placed on one side, and -all those in the smaller genera on the other side, a somewhat larger number of -the very common and much diffused or dominant species will be found on the side -of the larger genera. This, again, might have been anticipated; for the mere -fact of many species of the same genus inhabiting any country, shows that there -is something in the organic or inorganic conditions of that country favourable -to the genus; and, consequently, we might have expected to have found in the -larger genera, or those including many species, a large proportional number of -dominant species. But so many causes tend to obscure this result, that I am -surprised that my tables show even a small majority on the side of the larger -genera. I will here allude to only two causes of obscurity. Fresh-water and -salt-loving plants have generally very wide ranges and are much diffused, but -this seems to be connected with the nature of the stations inhabited by them, -and has little or no relation to the size of the genera to which the species -belong. Again, plants low in the scale of organisation are generally much more -widely diffused than plants higher in the scale; and here again there is no -close relation to the size of the genera. The cause of lowly-organised plants -ranging widely will be discussed in our chapter on geographical distribution. - -From looking at species as only strongly-marked and well-defined varieties, I -was led to anticipate that the species of the larger genera in each country -would oftener present varieties, than the species of the smaller genera; for -wherever many closely related species (i.e. species of the same genus) have -been formed, many varieties or incipient species ought, as a general rule, to -be now forming. Where many large trees grow, we expect to find saplings. Where -many species of a genus have been formed through variation, circumstances have -been favourable for variation; and hence we might expect that the circumstances -would generally be still favourable to variation. On the other hand, if we look -at each species as a special act of creation, there is no apparent reason why -more varieties should occur in a group having many species, than in one having -few. - -To test the truth of this anticipation I have arranged the plants of twelve -countries, and the coleopterous insects of two districts, into two nearly equal -masses, the species of the larger genera on one side, and those of the smaller -genera on the other side, and it has invariably proved to be the case that a -larger proportion of the species on the side of the larger genera present -varieties, than on the side of the smaller genera. Moreover, the species of the -large genera which present any varieties, invariably present a larger average -number of varieties than do the species of the small genera. Both these results -follow when another division is made, and when all the smallest genera, with -from only one to four species, are absolutely excluded from the tables. These -facts are of plain signification on the view that species are only strongly -marked and permanent varieties; for wherever many species of the same genus -have been formed, or where, if we may use the expression, the manufactory of -species has been active, we ought generally to find the manufactory still in -action, more especially as we have every reason to believe the process of -manufacturing new species to be a slow one. And this certainly is the case, if -varieties be looked at as incipient species; for my tables clearly show as a -general rule that, wherever many species of a genus have been formed, the -species of that genus present a number of varieties, that is of incipient -species, beyond the average. It is not that all large genera are now varying -much, and are thus increasing in the number of their species, or that no small -genera are now varying and increasing; for if this had been so, it would have -been fatal to my theory; inasmuch as geology plainly tells us that small genera -have in the lapse of time often increased greatly in size; and that large -genera have often come to their maxima, declined, and disappeared. All that we -want to show is, that where many species of a genus have been formed, on an -average many are still forming; and this holds good. +Guided by theoretical considerations, I thought that some interesting +results might be obtained in regard to the nature and relations of the +species which vary most, by tabulating all the varieties in several +well-worked floras. At first this seemed a simple task; but Mr. H. C. +Watson, to whom I am much indebted for valuable advice and assistance on +this subject, soon convinced me that there were many difficulties, as +did subsequently Dr. Hooker, even in stronger terms. I shall reserve for +my future work the discussion of these difficulties, and the tables +themselves of the proportional numbers of the varying species. Dr. +Hooker permits me to add, that after having carefully read my +manuscript, and examined the tables, he thinks that the following +statements are fairly well established. The whole subject, however, +treated as it necessarily here is with much brevity, is rather +perplexing, and allusions cannot be avoided to the “struggle for +existence,” “divergence of character,” and other questions, hereafter to +be discussed. + +Alph. De Candolle and others have shown that plants which have very wide +ranges generally present varieties; and this might have been expected, +as they become exposed to diverse physical conditions, and as they come +into competition (which, as we shall hereafter see, is a far more +important circumstance) with different sets of organic beings. But my +tables further show that, in any limited country, the species which are +most common, that is abound most in individuals, and the species which +are most widely diffused within their own country (and this is a +different consideration from wide range, and to a certain extent from +commonness), often give rise to varieties sufficiently well-marked to +have been recorded in botanical works. Hence it is the most flourishing, +or, as they may be called, the dominant species,—those which range +widely over the world, are the most diffused in their own country, and +are the most numerous in individuals,—which oftenest produce well-marked +varieties, or, as I consider them, incipient species. And this, perhaps, +might have been anticipated; for, as varieties, in order to become in +any degree permanent, necessarily have to struggle with the other +inhabitants of the country, the species which are already dominant will +be the most likely to yield offspring which, though in some slight +degree modified, will still inherit those advantages that enabled their +parents to become dominant over their compatriots. + +If the plants inhabiting a country and described in any Flora be divided +into two equal masses, all those in the larger genera being placed on +one side, and all those in the smaller genera on the other side, a +somewhat larger number of the very common and much diffused or dominant +species will be found on the side of the larger genera. This, again, +might have been anticipated; for the mere fact of many species of the +same genus inhabiting any country, shows that there is something in the +organic or inorganic conditions of that country favourable to the genus; +and, consequently, we might have expected to have found in the larger +genera, or those including many species, a large proportional number of +dominant species. But so many causes tend to obscure this result, that I +am surprised that my tables show even a small majority on the side of +the larger genera. I will here allude to only two causes of obscurity. +Fresh-water and salt-loving plants have generally very wide ranges and +are much diffused, but this seems to be connected with the nature of the +stations inhabited by them, and has little or no relation to the size of +the genera to which the species belong. Again, plants low in the scale +of organisation are generally much more widely diffused than plants +higher in the scale; and here again there is no close relation to the +size of the genera. The cause of lowly-organised plants ranging widely +will be discussed in our chapter on geographical distribution. + +From looking at species as only strongly-marked and well-defined +varieties, I was led to anticipate that the species of the larger genera +in each country would oftener present varieties, than the species of the +smaller genera; for wherever many closely related species (i.e. species +of the same genus) have been formed, many varieties or incipient species +ought, as a general rule, to be now forming. Where many large trees +grow, we expect to find saplings. Where many species of a genus have +been formed through variation, circumstances have been favourable for +variation; and hence we might expect that the circumstances would +generally be still favourable to variation. On the other hand, if we +look at each species as a special act of creation, there is no apparent +reason why more varieties should occur in a group having many species, +than in one having few. + +To test the truth of this anticipation I have arranged the plants of +twelve countries, and the coleopterous insects of two districts, into +two nearly equal masses, the species of the larger genera on one side, +and those of the smaller genera on the other side, and it has invariably +proved to be the case that a larger proportion of the species on the +side of the larger genera present varieties, than on the side of the +smaller genera. Moreover, the species of the large genera which present +any varieties, invariably present a larger average number of varieties +than do the species of the small genera. Both these results follow when +another division is made, and when all the smallest genera, with from +only one to four species, are absolutely excluded from the tables. These +facts are of plain signification on the view that species are only +strongly marked and permanent varieties; for wherever many species of +the same genus have been formed, or where, if we may use the expression, +the manufactory of species has been active, we ought generally to find +the manufactory still in action, more especially as we have every reason +to believe the process of manufacturing new species to be a slow one. +And this certainly is the case, if varieties be looked at as incipient +species; for my tables clearly show as a general rule that, wherever +many species of a genus have been formed, the species of that genus +present a number of varieties, that is of incipient species, beyond the +average. It is not that all large genera are now varying much, and are +thus increasing in the number of their species, or that no small genera +are now varying and increasing; for if this had been so, it would have +been fatal to my theory; inasmuch as geology plainly tells us that small +genera have in the lapse of time often increased greatly in size; and +that large genera have often come to their maxima, declined, and +disappeared. All that we want to show is, that where many species of a +genus have been formed, on an average many are still forming; and this +holds good. There are other relations between the species of large genera and their recorded varieties which deserve notice. We have seen that there is no -infallible criterion by which to distinguish species and well-marked varieties; -and in those cases in which intermediate links have not been found between -doubtful forms, naturalists are compelled to come to a determination by the -amount of difference between them, judging by analogy whether or not the amount -suffices to raise one or both to the rank of species. Hence the amount of -difference is one very important criterion in settling whether two forms should -be ranked as species or varieties. Now Fries has remarked in regard to plants, -and Westwood in regard to insects, that in large genera the amount of -difference between the species is often exceedingly small. I have endeavoured -to test this numerically by averages, and, as far as my imperfect results go, -they always confirm the view. I have also consulted some sagacious and most -experienced observers, and, after deliberation, they concur in this view. In -this respect, therefore, the species of the larger genera resemble varieties, -more than do the species of the smaller genera. Or the case may be put in -another way, and it may be said, that in the larger genera, in which a number -of varieties or incipient species greater than the average are now -manufacturing, many of the species already manufactured still to a certain -extent resemble varieties, for they differ from each other by a less than usual -amount of difference. - -Moreover, the species of the large genera are related to each other, in the -same manner as the varieties of any one species are related to each other. No -naturalist pretends that all the species of a genus are equally distinct from -each other; they may generally be divided into sub-genera, or sections, or -lesser groups. As Fries has well remarked, little groups of species are -generally clustered like satellites around certain other species. And what are -varieties but groups of forms, unequally related to each other, and clustered -round certain forms—that is, round their parent-species? Undoubtedly there is -one most important point of difference between varieties and species; namely, -that the amount of difference between varieties, when compared with each other -or with their parent-species, is much less than that between the species of the -same genus. But when we come to discuss the principle, as I call it, of -Divergence of Character, we shall see how this may be explained, and how the -lesser differences between varieties will tend to increase into the greater -differences between species. - -There is one other point which seems to me worth notice. Varieties generally -have much restricted ranges: this statement is indeed scarcely more than a -truism, for if a variety were found to have a wider range than that of its -supposed parent-species, their denominations ought to be reversed. But there is -also reason to believe, that those species which are very closely allied to -other species, and in so far resemble varieties, often have much restricted -ranges. For instance, Mr. H. C. Watson has marked for me in the well-sifted -London Catalogue of plants (4th edition) 63 plants which are therein ranked as -species, but which he considers as so closely allied to other species as to be -of doubtful value: these 63 reputed species range on an average over 6.9 of the -provinces into which Mr. Watson has divided Great Britain. Now, in this same -catalogue, 53 acknowledged varieties are recorded, and these range over 7.7 -provinces; whereas, the species to which these varieties belong range over 14.3 -provinces. So that the acknowledged varieties have very nearly the same -restricted average range, as have those very closely allied forms, marked for -me by Mr. Watson as doubtful species, but which are almost universally ranked -by British botanists as good and true species. - -Finally, then, varieties have the same general characters as species, for they -cannot be distinguished from species,—except, firstly, by the discovery of -intermediate linking forms, and the occurrence of such links cannot affect the -actual characters of the forms which they connect; and except, secondly, by a -certain amount of difference, for two forms, if differing very little, are -generally ranked as varieties, notwithstanding that intermediate linking forms -have not been discovered; but the amount of difference considered necessary to -give to two forms the rank of species is quite indefinite. In genera having -more than the average number of species in any country, the species of these -genera have more than the average number of varieties. In large genera the -species are apt to be closely, but unequally, allied together, forming little -clusters round certain species. Species very closely allied to other species -apparently have restricted ranges. In all these several respects the species of -large genera present a strong analogy with varieties. And we can clearly -understand these analogies, if species have once existed as varieties, and have -thus originated: whereas, these analogies are utterly inexplicable if each -species has been independently created. - -We have, also, seen that it is the most flourishing and dominant species of the -larger genera which on an average vary most; and varieties, as we shall -hereafter see, tend to become converted into new and distinct species. The -larger genera thus tend to become larger; and throughout nature the forms of -life which are now dominant tend to become still more dominant by leaving many -modified and dominant descendants. But by steps hereafter to be explained, the -larger genera also tend to break up into smaller genera. And thus, the forms of -life throughout the universe become divided into groups subordinate to groups. - -CHAPTER III. -STRUGGLE FOR EXISTENCE. - -Bears on natural selection. The term used in a wide sense. Geometrical powers -of increase. Rapid increase of naturalised animals and plants. Nature of the -checks to increase. Competition universal. Effects of climate. Protection from -the number of individuals. Complex relations of all animals and plants -throughout nature. Struggle for life most severe between individuals and -varieties of the same species; often severe between species of the same genus. -The relation of organism to organism the most important of all relations. - -Before entering on the subject of this chapter, I must make a few preliminary -remarks, to show how the struggle for existence bears on Natural Selection. It -has been seen in the last chapter that amongst organic beings in a state of -nature there is some individual variability; indeed I am not aware that this -has ever been disputed. It is immaterial for us whether a multitude of doubtful -forms be called species or sub-species or varieties; what rank, for instance, -the two or three hundred doubtful forms of British plants are entitled to hold, -if the existence of any well-marked varieties be admitted. But the mere -existence of individual variability and of some few well-marked varieties, -though necessary as the foundation for the work, helps us but little in -understanding how species arise in nature. How have all those exquisite -adaptations of one part of the organisation to another part, and to the -conditions of life, and of one distinct organic being to another being, been -perfected? We see these beautiful co-adaptations most plainly in the woodpecker -and missletoe; and only a little less plainly in the humblest parasite which -clings to the hairs of a quadruped or feathers of a bird; in the structure of -the beetle which dives through the water; in the plumed seed which is wafted by -the gentlest breeze; in short, we see beautiful adaptations everywhere and in -every part of the organic world. - -Again, it may be asked, how is it that varieties, which I have called incipient -species, become ultimately converted into good and distinct species, which in -most cases obviously differ from each other far more than do the varieties of -the same species? How do those groups of species, which constitute what are -called distinct genera, and which differ from each other more than do the -species of the same genus, arise? All these results, as we shall more fully see -in the next chapter, follow inevitably from the struggle for life. Owing to -this struggle for life, any variation, however slight and from whatever cause -proceeding, if it be in any degree profitable to an individual of any species, -in its infinitely complex relations to other organic beings and to external -nature, will tend to the preservation of that individual, and will generally be -inherited by its offspring. The offspring, also, will thus have a better chance -of surviving, for, of the many individuals of any species which are -periodically born, but a small number can survive. I have called this -principle, by which each slight variation, if useful, is preserved, by the term -of Natural Selection, in order to mark its relation to man’s power of -selection. We have seen that man by selection can certainly produce great -results, and can adapt organic beings to his own uses, through the accumulation -of slight but useful variations, given to him by the hand of Nature. But -Natural Selection, as we shall hereafter see, is a power incessantly ready for -action, and is as immeasurably superior to man’s feeble efforts, as the works -of Nature are to those of Art. - -We will now discuss in a little more detail the struggle for existence. In my -future work this subject shall be treated, as it well deserves, at much greater -length. The elder De Candolle and Lyell have largely and philosophically shown -that all organic beings are exposed to severe competition. In regard to plants, -no one has treated this subject with more spirit and ability than W. Herbert, -Dean of Manchester, evidently the result of his great horticultural knowledge. -Nothing is easier than to admit in words the truth of the universal struggle -for life, or more difficult—at least I have found it so—than constantly to bear -this conclusion in mind. Yet unless it be thoroughly engrained in the mind, I -am convinced that the whole economy of nature, with every fact on distribution, -rarity, abundance, extinction, and variation, will be dimly seen or quite -misunderstood. We behold the face of nature bright with gladness, we often see -superabundance of food; we do not see, or we forget, that the birds which are -idly singing round us mostly live on insects or seeds, and are thus constantly -destroying life; or we forget how largely these songsters, or their eggs, or -their nestlings, are destroyed by birds and beasts of prey; we do not always -bear in mind, that though food may be now superabundant, it is not so at all -seasons of each recurring year. - -I should premise that I use the term Struggle for Existence in a large and -metaphorical sense, including dependence of one being on another, and including -(which is more important) not only the life of the individual, but success in -leaving progeny. Two canine animals in a time of dearth, may be truly said to -struggle with each other which shall get food and live. But a plant on the edge -of a desert is said to struggle for life against the drought, though more -properly it should be said to be dependent on the moisture. A plant which -annually produces a thousand seeds, of which on an average only one comes to -maturity, may be more truly said to struggle with the plants of the same and -other kinds which already clothe the ground. The missletoe is dependent on the -apple and a few other trees, but can only in a far-fetched sense be said to -struggle with these trees, for if too many of these parasites grow on the same -tree, it will languish and die. But several seedling missletoes, growing close -together on the same branch, may more truly be said to struggle with each -other. As the missletoe is disseminated by birds, its existence depends on -birds; and it may metaphorically be said to struggle with other fruit-bearing -plants, in order to tempt birds to devour and thus disseminate its seeds rather -than those of other plants. In these several senses, which pass into each -other, I use for convenience sake the general term of struggle for existence. - -A struggle for existence inevitably follows from the high rate at which all -organic beings tend to increase. Every being, which during its natural lifetime -produces several eggs or seeds, must suffer destruction during some period of -its life, and during some season or occasional year, otherwise, on the -principle of geometrical increase, its numbers would quickly become so -inordinately great that no country could support the product. Hence, as more -individuals are produced than can possibly survive, there must in every case be -a struggle for existence, either one individual with another of the same -species, or with the individuals of distinct species, or with the physical -conditions of life. It is the doctrine of Malthus applied with manifold force -to the whole animal and vegetable kingdoms; for in this case there can be no -artificial increase of food, and no prudential restraint from marriage. -Although some species may be now increasing, more or less rapidly, in numbers, -all cannot do so, for the world would not hold them. - -There is no exception to the rule that every organic being naturally increases -at so high a rate, that if not destroyed, the earth would soon be covered by -the progeny of a single pair. Even slow-breeding man has doubled in twenty-five -years, and at this rate, in a few thousand years, there would literally not be -standing room for his progeny. Linnæus has calculated that if an annual plant -produced only two seeds—and there is no plant so unproductive as this—and their -seedlings next year produced two, and so on, then in twenty years there would -be a million plants. The elephant is reckoned to be the slowest breeder of all -known animals, and I have taken some pains to estimate its probable minimum -rate of natural increase: it will be under the mark to assume that it breeds -when thirty years old, and goes on breeding till ninety years old, bringing -forth three pair of young in this interval; if this be so, at the end of the -fifth century there would be alive fifteen million elephants, descended from -the first pair. - -But we have better evidence on this subject than mere theoretical calculations, -namely, the numerous recorded cases of the astonishingly rapid increase of -various animals in a state of nature, when circumstances have been favourable -to them during two or three following seasons. Still more striking is the -evidence from our domestic animals of many kinds which have run wild in several -parts of the world: if the statements of the rate of increase of slow-breeding -cattle and horses in South America, and latterly in Australia, had not been -well authenticated, they would have been quite incredible. So it is with -plants: cases could be given of introduced plants which have become common -throughout whole islands in a period of less than ten years. Several of the -plants now most numerous over the wide plains of La Plata, clothing square -leagues of surface almost to the exclusion of all other plants, have been -introduced from Europe; and there are plants which now range in India, as I -hear from Dr. Falconer, from Cape Comorin to the Himalaya, which have been -imported from America since its discovery. In such cases, and endless instances -could be given, no one supposes that the fertility of these animals or plants -has been suddenly and temporarily increased in any sensible degree. The obvious -explanation is that the conditions of life have been very favourable, and that -there has consequently been less destruction of the old and young, and that -nearly all the young have been enabled to breed. In such cases the geometrical -ratio of increase, the result of which never fails to be surprising, simply -explains the extraordinarily rapid increase and wide diffusion of naturalised -productions in their new homes. - -In a state of nature almost every plant produces seed, and amongst animals -there are very few which do not annually pair. Hence we may confidently assert, -that all plants and animals are tending to increase at a geometrical ratio, -that all would most rapidly stock every station in which they could any how -exist, and that the geometrical tendency to increase must be checked by -destruction at some period of life. Our familiarity with the larger domestic -animals tends, I think, to mislead us: we see no great destruction falling on -them, and we forget that thousands are annually slaughtered for food, and that -in a state of nature an equal number would have somehow to be disposed of. - -The only difference between organisms which annually produce eggs or seeds by -the thousand, and those which produce extremely few, is, that the slow-breeders -would require a few more years to people, under favourable conditions, a whole -district, let it be ever so large. The condor lays a couple of eggs and the -ostrich a score, and yet in the same country the condor may be the more -numerous of the two: the Fulmar petrel lays but one egg, yet it is believed to -be the most numerous bird in the world. One fly deposits hundreds of eggs, and -another, like the hippobosca, a single one; but this difference does not -determine how many individuals of the two species can be supported in a -district. A large number of eggs is of some importance to those species, which -depend on a rapidly fluctuating amount of food, for it allows them rapidly to -increase in number. But the real importance of a large number of eggs or seeds -is to make up for much destruction at some period of life; and this period in -the great majority of cases is an early one. If an animal can in any way -protect its own eggs or young, a small number may be produced, and yet the -average stock be fully kept up; but if many eggs or young are destroyed, many -must be produced, or the species will become extinct. It would suffice to keep -up the full number of a tree, which lived on an average for a thousand years, -if a single seed were produced once in a thousand years, supposing that this -seed were never destroyed, and could be ensured to germinate in a fitting -place. So that in all cases, the average number of any animal or plant depends -only indirectly on the number of its eggs or seeds. - -In looking at Nature, it is most necessary to keep the foregoing considerations -always in mind—never to forget that every single organic being around us may be -said to be striving to the utmost to increase in numbers; that each lives by a -struggle at some period of its life; that heavy destruction inevitably falls -either on the young or old, during each generation or at recurrent intervals. -Lighten any check, mitigate the destruction ever so little, and the number of -the species will almost instantaneously increase to any amount. The face of -Nature may be compared to a yielding surface, with ten thousand sharp wedges -packed close together and driven inwards by incessant blows, sometimes one +infallible criterion by which to distinguish species and well-marked +varieties; and in those cases in which intermediate links have not been +found between doubtful forms, naturalists are compelled to come to a +determination by the amount of difference between them, judging by +analogy whether or not the amount suffices to raise one or both to the +rank of species. Hence the amount of difference is one very important +criterion in settling whether two forms should be ranked as species or +varieties. Now Fries has remarked in regard to plants, and Westwood in +regard to insects, that in large genera the amount of difference between +the species is often exceedingly small. I have endeavoured to test this +numerically by averages, and, as far as my imperfect results go, they +always confirm the view. I have also consulted some sagacious and most +experienced observers, and, after deliberation, they concur in this +view. In this respect, therefore, the species of the larger genera +resemble varieties, more than do the species of the smaller genera. Or +the case may be put in another way, and it may be said, that in the +larger genera, in which a number of varieties or incipient species +greater than the average are now manufacturing, many of the species +already manufactured still to a certain extent resemble varieties, for +they differ from each other by a less than usual amount of difference. + +Moreover, the species of the large genera are related to each other, in +the same manner as the varieties of any one species are related to each +other. No naturalist pretends that all the species of a genus are +equally distinct from each other; they may generally be divided into +sub-genera, or sections, or lesser groups. As Fries has well remarked, +little groups of species are generally clustered like satellites around +certain other species. And what are varieties but groups of forms, +unequally related to each other, and clustered round certain forms—that +is, round their parent-species? Undoubtedly there is one most important +point of difference between varieties and species; namely, that the +amount of difference between varieties, when compared with each other or +with their parent-species, is much less than that between the species of +the same genus. But when we come to discuss the principle, as I call it, +of Divergence of Character, we shall see how this may be explained, and +how the lesser differences between varieties will tend to increase into +the greater differences between species. + +There is one other point which seems to me worth notice. Varieties +generally have much restricted ranges: this statement is indeed scarcely +more than a truism, for if a variety were found to have a wider range +than that of its supposed parent-species, their denominations ought to +be reversed. But there is also reason to believe, that those species +which are very closely allied to other species, and in so far resemble +varieties, often have much restricted ranges. For instance, Mr. H. C. +Watson has marked for me in the well-sifted London Catalogue of plants +(4th edition) 63 plants which are therein ranked as species, but which +he considers as so closely allied to other species as to be of doubtful +value: these 63 reputed species range on an average over 6.9 of the +provinces into which Mr. Watson has divided Great Britain. Now, in this +same catalogue, 53 acknowledged varieties are recorded, and these range +over 7.7 provinces; whereas, the species to which these varieties belong +range over 14.3 provinces. So that the acknowledged varieties have very +nearly the same restricted average range, as have those very closely +allied forms, marked for me by Mr. Watson as doubtful species, but which +are almost universally ranked by British botanists as good and true +species. + +Finally, then, varieties have the same general characters as species, +for they cannot be distinguished from species,—except, firstly, by the +discovery of intermediate linking forms, and the occurrence of such +links cannot affect the actual characters of the forms which they +connect; and except, secondly, by a certain amount of difference, for +two forms, if differing very little, are generally ranked as varieties, +notwithstanding that intermediate linking forms have not been +discovered; but the amount of difference considered necessary to give to +two forms the rank of species is quite indefinite. In genera having more +than the average number of species in any country, the species of these +genera have more than the average number of varieties. In large genera +the species are apt to be closely, but unequally, allied together, +forming little clusters round certain species. Species very closely +allied to other species apparently have restricted ranges. In all these +several respects the species of large genera present a strong analogy +with varieties. And we can clearly understand these analogies, if +species have once existed as varieties, and have thus originated: +whereas, these analogies are utterly inexplicable if each species has +been independently created. + +We have, also, seen that it is the most flourishing and dominant species +of the larger genera which on an average vary most; and varieties, as we +shall hereafter see, tend to become converted into new and distinct +species. The larger genera thus tend to become larger; and throughout +nature the forms of life which are now dominant tend to become still +more dominant by leaving many modified and dominant descendants. But by +steps hereafter to be explained, the larger genera also tend to break up +into smaller genera. And thus, the forms of life throughout the universe +become divided into groups subordinate to groups. + +CHAPTER III. STRUGGLE FOR EXISTENCE. + +Bears on natural selection. The term used in a wide sense. Geometrical +powers of increase. Rapid increase of naturalised animals and plants. +Nature of the checks to increase. Competition universal. Effects of +climate. Protection from the number of individuals. Complex relations of +all animals and plants throughout nature. Struggle for life most severe +between individuals and varieties of the same species; often severe +between species of the same genus. The relation of organism to organism +the most important of all relations. + +Before entering on the subject of this chapter, I must make a few +preliminary remarks, to show how the struggle for existence bears on +Natural Selection. It has been seen in the last chapter that amongst +organic beings in a state of nature there is some individual +variability; indeed I am not aware that this has ever been disputed. It +is immaterial for us whether a multitude of doubtful forms be called +species or sub-species or varieties; what rank, for instance, the two or +three hundred doubtful forms of British plants are entitled to hold, if +the existence of any well-marked varieties be admitted. But the mere +existence of individual variability and of some few well-marked +varieties, though necessary as the foundation for the work, helps us but +little in understanding how species arise in nature. How have all those +exquisite adaptations of one part of the organisation to another part, +and to the conditions of life, and of one distinct organic being to +another being, been perfected? We see these beautiful co-adaptations +most plainly in the woodpecker and missletoe; and only a little less +plainly in the humblest parasite which clings to the hairs of a +quadruped or feathers of a bird; in the structure of the beetle which +dives through the water; in the plumed seed which is wafted by the +gentlest breeze; in short, we see beautiful adaptations everywhere and +in every part of the organic world. + +Again, it may be asked, how is it that varieties, which I have called +incipient species, become ultimately converted into good and distinct +species, which in most cases obviously differ from each other far more +than do the varieties of the same species? How do those groups of +species, which constitute what are called distinct genera, and which +differ from each other more than do the species of the same genus, +arise? All these results, as we shall more fully see in the next +chapter, follow inevitably from the struggle for life. Owing to this +struggle for life, any variation, however slight and from whatever cause +proceeding, if it be in any degree profitable to an individual of any +species, in its infinitely complex relations to other organic beings and +to external nature, will tend to the preservation of that individual, +and will generally be inherited by its offspring. The offspring, also, +will thus have a better chance of surviving, for, of the many +individuals of any species which are periodically born, but a small +number can survive. I have called this principle, by which each slight +variation, if useful, is preserved, by the term of Natural Selection, in +order to mark its relation to man’s power of selection. We have seen +that man by selection can certainly produce great results, and can adapt +organic beings to his own uses, through the accumulation of slight but +useful variations, given to him by the hand of Nature. But Natural +Selection, as we shall hereafter see, is a power incessantly ready for +action, and is as immeasurably superior to man’s feeble efforts, as the +works of Nature are to those of Art. + +We will now discuss in a little more detail the struggle for existence. +In my future work this subject shall be treated, as it well deserves, at +much greater length. The elder De Candolle and Lyell have largely and +philosophically shown that all organic beings are exposed to severe +competition. In regard to plants, no one has treated this subject with +more spirit and ability than W. Herbert, Dean of Manchester, evidently +the result of his great horticultural knowledge. Nothing is easier than +to admit in words the truth of the universal struggle for life, or more +difficult—at least I have found it so—than constantly to bear this +conclusion in mind. Yet unless it be thoroughly engrained in the mind, I +am convinced that the whole economy of nature, with every fact on +distribution, rarity, abundance, extinction, and variation, will be +dimly seen or quite misunderstood. We behold the face of nature bright +with gladness, we often see superabundance of food; we do not see, or we +forget, that the birds which are idly singing round us mostly live on +insects or seeds, and are thus constantly destroying life; or we forget +how largely these songsters, or their eggs, or their nestlings, are +destroyed by birds and beasts of prey; we do not always bear in mind, +that though food may be now superabundant, it is not so at all seasons +of each recurring year. + +I should premise that I use the term Struggle for Existence in a large +and metaphorical sense, including dependence of one being on another, +and including (which is more important) not only the life of the +individual, but success in leaving progeny. Two canine animals in a time +of dearth, may be truly said to struggle with each other which shall get +food and live. But a plant on the edge of a desert is said to struggle +for life against the drought, though more properly it should be said to +be dependent on the moisture. A plant which annually produces a thousand +seeds, of which on an average only one comes to maturity, may be more +truly said to struggle with the plants of the same and other kinds which +already clothe the ground. The missletoe is dependent on the apple and a +few other trees, but can only in a far-fetched sense be said to struggle +with these trees, for if too many of these parasites grow on the same +tree, it will languish and die. But several seedling missletoes, growing +close together on the same branch, may more truly be said to struggle +with each other. As the missletoe is disseminated by birds, its +existence depends on birds; and it may metaphorically be said to +struggle with other fruit-bearing plants, in order to tempt birds to +devour and thus disseminate its seeds rather than those of other plants. +In these several senses, which pass into each other, I use for +convenience sake the general term of struggle for existence. + +A struggle for existence inevitably follows from the high rate at which +all organic beings tend to increase. Every being, which during its +natural lifetime produces several eggs or seeds, must suffer destruction +during some period of its life, and during some season or occasional +year, otherwise, on the principle of geometrical increase, its numbers +would quickly become so inordinately great that no country could support +the product. Hence, as more individuals are produced than can possibly +survive, there must in every case be a struggle for existence, either +one individual with another of the same species, or with the individuals +of distinct species, or with the physical conditions of life. It is the +doctrine of Malthus applied with manifold force to the whole animal and +vegetable kingdoms; for in this case there can be no artificial increase +of food, and no prudential restraint from marriage. Although some +species may be now increasing, more or less rapidly, in numbers, all +cannot do so, for the world would not hold them. + +There is no exception to the rule that every organic being naturally +increases at so high a rate, that if not destroyed, the earth would soon +be covered by the progeny of a single pair. Even slow-breeding man has +doubled in twenty-five years, and at this rate, in a few thousand years, +there would literally not be standing room for his progeny. Linnæus has +calculated that if an annual plant produced only two seeds—and there is +no plant so unproductive as this—and their seedlings next year produced +two, and so on, then in twenty years there would be a million plants. +The elephant is reckoned to be the slowest breeder of all known animals, +and I have taken some pains to estimate its probable minimum rate of +natural increase: it will be under the mark to assume that it breeds +when thirty years old, and goes on breeding till ninety years old, +bringing forth three pair of young in this interval; if this be so, at +the end of the fifth century there would be alive fifteen million +elephants, descended from the first pair. + +But we have better evidence on this subject than mere theoretical +calculations, namely, the numerous recorded cases of the astonishingly +rapid increase of various animals in a state of nature, when +circumstances have been favourable to them during two or three following +seasons. Still more striking is the evidence from our domestic animals +of many kinds which have run wild in several parts of the world: if the +statements of the rate of increase of slow-breeding cattle and horses in +South America, and latterly in Australia, had not been well +authenticated, they would have been quite incredible. So it is with +plants: cases could be given of introduced plants which have become +common throughout whole islands in a period of less than ten years. +Several of the plants now most numerous over the wide plains of La +Plata, clothing square leagues of surface almost to the exclusion of all +other plants, have been introduced from Europe; and there are plants +which now range in India, as I hear from Dr. Falconer, from Cape Comorin +to the Himalaya, which have been imported from America since its +discovery. In such cases, and endless instances could be given, no one +supposes that the fertility of these animals or plants has been suddenly +and temporarily increased in any sensible degree. The obvious +explanation is that the conditions of life have been very favourable, +and that there has consequently been less destruction of the old and +young, and that nearly all the young have been enabled to breed. In such +cases the geometrical ratio of increase, the result of which never fails +to be surprising, simply explains the extraordinarily rapid increase and +wide diffusion of naturalised productions in their new homes. + +In a state of nature almost every plant produces seed, and amongst +animals there are very few which do not annually pair. Hence we may +confidently assert, that all plants and animals are tending to increase +at a geometrical ratio, that all would most rapidly stock every station +in which they could any how exist, and that the geometrical tendency to +increase must be checked by destruction at some period of life. Our +familiarity with the larger domestic animals tends, I think, to mislead +us: we see no great destruction falling on them, and we forget that +thousands are annually slaughtered for food, and that in a state of +nature an equal number would have somehow to be disposed of. + +The only difference between organisms which annually produce eggs or +seeds by the thousand, and those which produce extremely few, is, that +the slow-breeders would require a few more years to people, under +favourable conditions, a whole district, let it be ever so large. The +condor lays a couple of eggs and the ostrich a score, and yet in the +same country the condor may be the more numerous of the two: the Fulmar +petrel lays but one egg, yet it is believed to be the most numerous bird +in the world. One fly deposits hundreds of eggs, and another, like the +hippobosca, a single one; but this difference does not determine how +many individuals of the two species can be supported in a district. A +large number of eggs is of some importance to those species, which +depend on a rapidly fluctuating amount of food, for it allows them +rapidly to increase in number. But the real importance of a large number +of eggs or seeds is to make up for much destruction at some period of +life; and this period in the great majority of cases is an early one. If +an animal can in any way protect its own eggs or young, a small number +may be produced, and yet the average stock be fully kept up; but if many +eggs or young are destroyed, many must be produced, or the species will +become extinct. It would suffice to keep up the full number of a tree, +which lived on an average for a thousand years, if a single seed were +produced once in a thousand years, supposing that this seed were never +destroyed, and could be ensured to germinate in a fitting place. So that +in all cases, the average number of any animal or plant depends only +indirectly on the number of its eggs or seeds. + +In looking at Nature, it is most necessary to keep the foregoing +considerations always in mind—never to forget that every single organic +being around us may be said to be striving to the utmost to increase in +numbers; that each lives by a struggle at some period of its life; that +heavy destruction inevitably falls either on the young or old, during +each generation or at recurrent intervals. Lighten any check, mitigate +the destruction ever so little, and the number of the species will +almost instantaneously increase to any amount. The face of Nature may be +compared to a yielding surface, with ten thousand sharp wedges packed +close together and driven inwards by incessant blows, sometimes one wedge being struck, and then another with greater force. -What checks the natural tendency of each species to increase in number is most -obscure. Look at the most vigorous species; by as much as it swarms in numbers, -by so much will its tendency to increase be still further increased. We know -not exactly what the checks are in even one single instance. Nor will this -surprise any one who reflects how ignorant we are on this head, even in regard -to mankind, so incomparably better known than any other animal. This subject -has been ably treated by several authors, and I shall, in my future work, -discuss some of the checks at considerable length, more especially in regard to -the feral animals of South America. Here I will make only a few remarks, just -to recall to the reader’s mind some of the chief points. Eggs or very young -animals seem generally to suffer most, but this is not invariably the case. -With plants there is a vast destruction of seeds, but, from some observations -which I have made, I believe that it is the seedlings which suffer most from -germinating in ground already thickly stocked with other plants. Seedlings, -also, are destroyed in vast numbers by various enemies; for instance, on a -piece of ground three feet long and two wide, dug and cleared, and where there -could be no choking from other plants, I marked all the seedlings of our native -weeds as they came up, and out of the 357 no less than 295 were destroyed, -chiefly by slugs and insects. If turf which has long been mown, and the case -would be the same with turf closely browsed by quadrupeds, be let to grow, the -more vigorous plants gradually kill the less vigorous, though fully grown, -plants: thus out of twenty species growing on a little plot of turf (three feet -by four) nine species perished from the other species being allowed to grow up -freely. - -The amount of food for each species of course gives the extreme limit to which -each can increase; but very frequently it is not the obtaining food, but the -serving as prey to other animals, which determines the average numbers of a -species. Thus, there seems to be little doubt that the stock of partridges, -grouse, and hares on any large estate depends chiefly on the destruction of -vermin. If not one head of game were shot during the next twenty years in -England, and, at the same time, if no vermin were destroyed, there would, in -all probability, be less game than at present, although hundreds of thousands -of game animals are now annually killed. On the other hand, in some cases, as -with the elephant and rhinoceros, none are destroyed by beasts of prey: even -the tiger in India most rarely dares to attack a young elephant protected by -its dam. +What checks the natural tendency of each species to increase in number +is most obscure. Look at the most vigorous species; by as much as it +swarms in numbers, by so much will its tendency to increase be still +further increased. We know not exactly what the checks are in even one +single instance. Nor will this surprise any one who reflects how +ignorant we are on this head, even in regard to mankind, so incomparably +better known than any other animal. This subject has been ably treated +by several authors, and I shall, in my future work, discuss some of the +checks at considerable length, more especially in regard to the feral +animals of South America. Here I will make only a few remarks, just to +recall to the reader’s mind some of the chief points. Eggs or very young +animals seem generally to suffer most, but this is not invariably the +case. With plants there is a vast destruction of seeds, but, from some +observations which I have made, I believe that it is the seedlings which +suffer most from germinating in ground already thickly stocked with +other plants. Seedlings, also, are destroyed in vast numbers by various +enemies; for instance, on a piece of ground three feet long and two +wide, dug and cleared, and where there could be no choking from other +plants, I marked all the seedlings of our native weeds as they came up, +and out of the 357 no less than 295 were destroyed, chiefly by slugs and +insects. If turf which has long been mown, and the case would be the +same with turf closely browsed by quadrupeds, be let to grow, the more +vigorous plants gradually kill the less vigorous, though fully grown, +plants: thus out of twenty species growing on a little plot of turf +(three feet by four) nine species perished from the other species being +allowed to grow up freely. + +The amount of food for each species of course gives the extreme limit to +which each can increase; but very frequently it is not the obtaining +food, but the serving as prey to other animals, which determines the +average numbers of a species. Thus, there seems to be little doubt that +the stock of partridges, grouse, and hares on any large estate depends +chiefly on the destruction of vermin. If not one head of game were shot +during the next twenty years in England, and, at the same time, if no +vermin were destroyed, there would, in all probability, be less game +than at present, although hundreds of thousands of game animals are now +annually killed. On the other hand, in some cases, as with the elephant +and rhinoceros, none are destroyed by beasts of prey: even the tiger in +India most rarely dares to attack a young elephant protected by its dam. Climate plays an important part in determining the average numbers of a -species, and periodical seasons of extreme cold or drought, I believe to be the -most effective of all checks. I estimated that the winter of 1854-55 destroyed -four-fifths of the birds in my own grounds; and this is a tremendous -destruction, when we remember that ten per cent. is an extraordinarily severe -mortality from epidemics with man. The action of climate seems at first sight -to be quite independent of the struggle for existence; but in so far as climate -chiefly acts in reducing food, it brings on the most severe struggle between -the individuals, whether of the same or of distinct species, which subsist on -the same kind of food. Even when climate, for instance extreme cold, acts -directly, it will be the least vigorous, or those which have got least food -through the advancing winter, which will suffer most. When we travel from south -to north, or from a damp region to a dry, we invariably see some species -gradually getting rarer and rarer, and finally disappearing; and the change of -climate being conspicuous, we are tempted to attribute the whole effect to its -direct action. But this is a very false view: we forget that each species, even -where it most abounds, is constantly suffering enormous destruction at some -period of its life, from enemies or from competitors for the same place and -food; and if these enemies or competitors be in the least degree favoured by -any slight change of climate, they will increase in numbers, and, as each area -is already fully stocked with inhabitants, the other species will decrease. -When we travel southward and see a species decreasing in numbers, we may feel -sure that the cause lies quite as much in other species being favoured, as in -this one being hurt. So it is when we travel northward, but in a somewhat -lesser degree, for the number of species of all kinds, and therefore of -competitors, decreases northwards; hence in going northward, or in ascending a -mountain, we far oftener meet with stunted forms, due to the directly injurious -action of climate, than we do in proceeding southwards or in descending a -mountain. When we reach the Arctic regions, or snow-capped summits, or absolute -deserts, the struggle for life is almost exclusively with the elements. - -That climate acts in main part indirectly by favouring other species, we may -clearly see in the prodigious number of plants in our gardens which can -perfectly well endure our climate, but which never become naturalised, for they -cannot compete with our native plants, nor resist destruction by our native -animals. +species, and periodical seasons of extreme cold or drought, I believe to +be the most effective of all checks. I estimated that the winter of +1854-55 destroyed four-fifths of the birds in my own grounds; and this +is a tremendous destruction, when we remember that ten per cent. is an +extraordinarily severe mortality from epidemics with man. The action of +climate seems at first sight to be quite independent of the struggle for +existence; but in so far as climate chiefly acts in reducing food, it +brings on the most severe struggle between the individuals, whether of +the same or of distinct species, which subsist on the same kind of food. +Even when climate, for instance extreme cold, acts directly, it will be +the least vigorous, or those which have got least food through the +advancing winter, which will suffer most. When we travel from south to +north, or from a damp region to a dry, we invariably see some species +gradually getting rarer and rarer, and finally disappearing; and the +change of climate being conspicuous, we are tempted to attribute the +whole effect to its direct action. But this is a very false view: we +forget that each species, even where it most abounds, is constantly +suffering enormous destruction at some period of its life, from enemies +or from competitors for the same place and food; and if these enemies or +competitors be in the least degree favoured by any slight change of +climate, they will increase in numbers, and, as each area is already +fully stocked with inhabitants, the other species will decrease. When +we travel southward and see a species decreasing in numbers, we may feel +sure that the cause lies quite as much in other species being favoured, +as in this one being hurt. So it is when we travel northward, but in a +somewhat lesser degree, for the number of species of all kinds, and +therefore of competitors, decreases northwards; hence in going +northward, or in ascending a mountain, we far oftener meet with stunted +forms, due to the directly injurious action of climate, than we do in +proceeding southwards or in descending a mountain. When we reach the +Arctic regions, or snow-capped summits, or absolute deserts, the +struggle for life is almost exclusively with the elements. + +That climate acts in main part indirectly by favouring other species, we +may clearly see in the prodigious number of plants in our gardens which +can perfectly well endure our climate, but which never become +naturalised, for they cannot compete with our native plants, nor resist +destruction by our native animals. When a species, owing to highly favourable circumstances, increases inordinately in numbers in a small tract, epidemics—at least, this seems generally to occur with our game animals—often ensue: and here we have a -limiting check independent of the struggle for life. But even some of these -so-called epidemics appear to be due to parasitic worms, which have from some -cause, possibly in part through facility of diffusion amongst the crowded -animals, been disproportionably favoured: and here comes in a sort of struggle -between the parasite and its prey. - -On the other hand, in many cases, a large stock of individuals of the same -species, relatively to the numbers of its enemies, is absolutely necessary for -its preservation. Thus we can easily raise plenty of corn and rape-seed, etc., -in our fields, because the seeds are in great excess compared with the number -of birds which feed on them; nor can the birds, though having a superabundance -of food at this one season, increase in number proportionally to the supply of -seed, as their numbers are checked during winter: but any one who has tried, -knows how troublesome it is to get seed from a few wheat or other such plants -in a garden; I have in this case lost every single seed. This view of the -necessity of a large stock of the same species for its preservation, explains, -I believe, some singular facts in nature, such as that of very rare plants -being sometimes extremely abundant in the few spots where they do occur; and -that of some social plants being social, that is, abounding in individuals, -even on the extreme confines of their range. For in such cases, we may believe, -that a plant could exist only where the conditions of its life were so -favourable that many could exist together, and thus save each other from utter -destruction. I should add that the good effects of frequent intercrossing, and -the ill effects of close interbreeding, probably come into play in some of -these cases; but on this intricate subject I will not here enlarge. - -Many cases are on record showing how complex and unexpected are the checks and -relations between organic beings, which have to struggle together in the same -country. I will give only a single instance, which, though a simple one, has -interested me. In Staffordshire, on the estate of a relation where I had ample -means of investigation, there was a large and extremely barren heath, which had -never been touched by the hand of man; but several hundred acres of exactly the -same nature had been enclosed twenty-five years previously and planted with -Scotch fir. The change in the native vegetation of the planted part of the -heath was most remarkable, more than is generally seen in passing from one -quite different soil to another: not only the proportional numbers of the -heath-plants were wholly changed, but twelve species of plants (not counting -grasses and carices) flourished in the plantations, which could not be found on -the heath. The effect on the insects must have been still greater, for six -insectivorous birds were very common in the plantations, which were not to be -seen on the heath; and the heath was frequented by two or three distinct -insectivorous birds. Here we see how potent has been the effect of the -introduction of a single tree, nothing whatever else having been done, with the -exception that the land had been enclosed, so that cattle could not enter. But -how important an element enclosure is, I plainly saw near Farnham, in Surrey. -Here there are extensive heaths, with a few clumps of old Scotch firs on the -distant hill-tops: within the last ten years large spaces have been enclosed, -and self-sown firs are now springing up in multitudes, so close together that -all cannot live. When I ascertained that these young trees had not been sown or -planted, I was so much surprised at their numbers that I went to several points -of view, whence I could examine hundreds of acres of the unenclosed heath, and -literally I could not see a single Scotch fir, except the old planted clumps. -But on looking closely between the stems of the heath, I found a multitude of -seedlings and little trees, which had been perpetually browsed down by the -cattle. In one square yard, at a point some hundred yards distant from one of -the old clumps, I counted thirty-two little trees; and one of them, judging -from the rings of growth, had during twenty-six years tried to raise its head -above the stems of the heath, and had failed. No wonder that, as soon as the -land was enclosed, it became thickly clothed with vigorously growing young -firs. Yet the heath was so extremely barren and so extensive that no one would -ever have imagined that cattle would have so closely and effectually searched -it for food. - -Here we see that cattle absolutely determine the existence of the Scotch fir; -but in several parts of the world insects determine the existence of cattle. -Perhaps Paraguay offers the most curious instance of this; for here neither -cattle nor horses nor dogs have ever run wild, though they swarm southward and -northward in a feral state; and Azara and Rengger have shown that this is -caused by the greater number in Paraguay of a certain fly, which lays its eggs -in the navels of these animals when first born. The increase of these flies, -numerous as they are, must be habitually checked by some means, probably by -birds. Hence, if certain insectivorous birds (whose numbers are probably -regulated by hawks or beasts of prey) were to increase in Paraguay, the flies -would decrease—then cattle and horses would become feral, and this would -certainly greatly alter (as indeed I have observed in parts of South America) -the vegetation: this again would largely affect the insects; and this, as we -just have seen in Staffordshire, the insectivorous birds, and so onwards in -ever-increasing circles of complexity. We began this series by insectivorous -birds, and we have ended with them. Not that in nature the relations can ever -be as simple as this. Battle within battle must ever be recurring with varying -success; and yet in the long-run the forces are so nicely balanced, that the -face of nature remains uniform for long periods of time, though assuredly the -merest trifle would often give the victory to one organic being over another. -Nevertheless so profound is our ignorance, and so high our presumption, that we -marvel when we hear of the extinction of an organic being; and as we do not see -the cause, we invoke cataclysms to desolate the world, or invent laws on the -duration of the forms of life! - -I am tempted to give one more instance showing how plants and animals, most -remote in the scale of nature, are bound together by a web of complex -relations. I shall hereafter have occasion to show that the exotic Lobelia -fulgens, in this part of England, is never visited by insects, and -consequently, from its peculiar structure, never can set a seed. Many of our -orchidaceous plants absolutely require the visits of moths to remove their -pollen-masses and thus to fertilise them. I have, also, reason to believe that -humble-bees are indispensable to the fertilisation of the heartsease (Viola -tricolor), for other bees do not visit this flower. From experiments which I -have tried, I have found that the visits of bees, if not indispensable, are at -least highly beneficial to the fertilisation of our clovers; but humble-bees -alone visit the common red clover (Trifolium pratense), as other bees cannot -reach the nectar. Hence I have very little doubt, that if the whole genus of -humble-bees became extinct or very rare in England, the heartsease and red -clover would become very rare, or wholly disappear. The number of humble-bees -in any district depends in a great degree on the number of field-mice, which -destroy their combs and nests; and Mr. H. Newman, who has long attended to the -habits of humble-bees, believes that “more than two thirds of them are thus -destroyed all over England.” Now the number of mice is largely dependent, as -every one knows, on the number of cats; and Mr. Newman says, “Near villages and -small towns I have found the nests of humble-bees more numerous than elsewhere, -which I attribute to the number of cats that destroy the mice.” Hence it is -quite credible that the presence of a feline animal in large numbers in a -district might determine, through the intervention first of mice and then of -bees, the frequency of certain flowers in that district! +limiting check independent of the struggle for life. But even some of +these so-called epidemics appear to be due to parasitic worms, which +have from some cause, possibly in part through facility of diffusion +amongst the crowded animals, been disproportionably favoured: and here +comes in a sort of struggle between the parasite and its prey. + +On the other hand, in many cases, a large stock of individuals of the +same species, relatively to the numbers of its enemies, is absolutely +necessary for its preservation. Thus we can easily raise plenty of corn +and rape-seed, etc., in our fields, because the seeds are in great +excess compared with the number of birds which feed on them; nor can the +birds, though having a superabundance of food at this one season, +increase in number proportionally to the supply of seed, as their +numbers are checked during winter: but any one who has tried, knows how +troublesome it is to get seed from a few wheat or other such plants in a +garden; I have in this case lost every single seed. This view of the +necessity of a large stock of the same species for its preservation, +explains, I believe, some singular facts in nature, such as that of very +rare plants being sometimes extremely abundant in the few spots where +they do occur; and that of some social plants being social, that is, +abounding in individuals, even on the extreme confines of their range. +For in such cases, we may believe, that a plant could exist only where +the conditions of its life were so favourable that many could exist +together, and thus save each other from utter destruction. I should add +that the good effects of frequent intercrossing, and the ill effects of +close interbreeding, probably come into play in some of these cases; but +on this intricate subject I will not here enlarge. + +Many cases are on record showing how complex and unexpected are the +checks and relations between organic beings, which have to struggle +together in the same country. I will give only a single instance, which, +though a simple one, has interested me. In Staffordshire, on the estate +of a relation where I had ample means of investigation, there was a +large and extremely barren heath, which had never been touched by the +hand of man; but several hundred acres of exactly the same nature had +been enclosed twenty-five years previously and planted with Scotch fir. +The change in the native vegetation of the planted part of the heath was +most remarkable, more than is generally seen in passing from one quite +different soil to another: not only the proportional numbers of the +heath-plants were wholly changed, but twelve species of plants (not +counting grasses and carices) flourished in the plantations, which could +not be found on the heath. The effect on the insects must have been +still greater, for six insectivorous birds were very common in the +plantations, which were not to be seen on the heath; and the heath was +frequented by two or three distinct insectivorous birds. Here we see how +potent has been the effect of the introduction of a single tree, nothing +whatever else having been done, with the exception that the land had +been enclosed, so that cattle could not enter. But how important an +element enclosure is, I plainly saw near Farnham, in Surrey. Here there +are extensive heaths, with a few clumps of old Scotch firs on the +distant hill-tops: within the last ten years large spaces have been +enclosed, and self-sown firs are now springing up in multitudes, so +close together that all cannot live. When I ascertained that these young +trees had not been sown or planted, I was so much surprised at their +numbers that I went to several points of view, whence I could examine +hundreds of acres of the unenclosed heath, and literally I could not see +a single Scotch fir, except the old planted clumps. But on looking +closely between the stems of the heath, I found a multitude of seedlings +and little trees, which had been perpetually browsed down by the cattle. +In one square yard, at a point some hundred yards distant from one of +the old clumps, I counted thirty-two little trees; and one of them, +judging from the rings of growth, had during twenty-six years tried to +raise its head above the stems of the heath, and had failed. No wonder +that, as soon as the land was enclosed, it became thickly clothed with +vigorously growing young firs. Yet the heath was so extremely barren and +so extensive that no one would ever have imagined that cattle would have +so closely and effectually searched it for food. + +Here we see that cattle absolutely determine the existence of the Scotch +fir; but in several parts of the world insects determine the existence +of cattle. Perhaps Paraguay offers the most curious instance of this; +for here neither cattle nor horses nor dogs have ever run wild, though +they swarm southward and northward in a feral state; and Azara and +Rengger have shown that this is caused by the greater number in Paraguay +of a certain fly, which lays its eggs in the navels of these animals +when first born. The increase of these flies, numerous as they are, must +be habitually checked by some means, probably by birds. Hence, if +certain insectivorous birds (whose numbers are probably regulated by +hawks or beasts of prey) were to increase in Paraguay, the flies would +decrease—then cattle and horses would become feral, and this would +certainly greatly alter (as indeed I have observed in parts of South +America) the vegetation: this again would largely affect the insects; +and this, as we just have seen in Staffordshire, the insectivorous +birds, and so onwards in ever-increasing circles of complexity. We began +this series by insectivorous birds, and we have ended with them. Not +that in nature the relations can ever be as simple as this. Battle +within battle must ever be recurring with varying success; and yet in +the long-run the forces are so nicely balanced, that the face of nature +remains uniform for long periods of time, though assuredly the merest +trifle would often give the victory to one organic being over another. +Nevertheless so profound is our ignorance, and so high our presumption, +that we marvel when we hear of the extinction of an organic being; and +as we do not see the cause, we invoke cataclysms to desolate the world, +or invent laws on the duration of the forms of life! + +I am tempted to give one more instance showing how plants and animals, +most remote in the scale of nature, are bound together by a web of +complex relations. I shall hereafter have occasion to show that the +exotic Lobelia fulgens, in this part of England, is never visited by +insects, and consequently, from its peculiar structure, never can set a +seed. Many of our orchidaceous plants absolutely require the visits of +moths to remove their pollen-masses and thus to fertilise them. I have, +also, reason to believe that humble-bees are indispensable to the +fertilisation of the heartsease (Viola tricolor), for other bees do not +visit this flower. From experiments which I have tried, I have found +that the visits of bees, if not indispensable, are at least highly +beneficial to the fertilisation of our clovers; but humble-bees alone +visit the common red clover (Trifolium pratense), as other bees cannot +reach the nectar. Hence I have very little doubt, that if the whole +genus of humble-bees became extinct or very rare in England, the +heartsease and red clover would become very rare, or wholly disappear. +The number of humble-bees in any district depends in a great degree on +the number of field-mice, which destroy their combs and nests; and Mr. +H. Newman, who has long attended to the habits of humble-bees, believes +that “more than two thirds of them are thus destroyed all over England.” +Now the number of mice is largely dependent, as every one knows, on the +number of cats; and Mr. Newman says, “Near villages and small towns I +have found the nests of humble-bees more numerous than elsewhere, which +I attribute to the number of cats that destroy the mice.” Hence it is +quite credible that the presence of a feline animal in large numbers in +a district might determine, through the intervention first of mice and +then of bees, the frequency of certain flowers in that district! In the case of every species, many different checks, acting at different -periods of life, and during different seasons or years, probably come into -play; some one check or some few being generally the most potent, but all -concurring in determining the average number or even the existence of the -species. In some cases it can be shown that widely-different checks act on the -same species in different districts. When we look at the plants and bushes -clothing an entangled bank, we are tempted to attribute their proportional -numbers and kinds to what we call chance. But how false a view is this! Every -one has heard that when an American forest is cut down, a very different -vegetation springs up; but it has been observed that the trees now growing on -the ancient Indian mounds, in the Southern United States, display the same -beautiful diversity and proportion of kinds as in the surrounding virgin -forests. What a struggle between the several kinds of trees must here have gone -on during long centuries, each annually scattering its seeds by the thousand; -what war between insect and insect—between insects, snails, and other animals -with birds and beasts of prey—all striving to increase, and all feeding on each -other or on the trees or their seeds and seedlings, or on the other plants -which first clothed the ground and thus checked the growth of the trees! Throw -up a handful of feathers, and all must fall to the ground according to definite -laws; but how simple is this problem compared to the action and reaction of the +periods of life, and during different seasons or years, probably come +into play; some one check or some few being generally the most potent, +but all concurring in determining the average number or even the +existence of the species. In some cases it can be shown that +widely-different checks act on the same species in different districts. +When we look at the plants and bushes clothing an entangled bank, we are +tempted to attribute their proportional numbers and kinds to what we +call chance. But how false a view is this! Every one has heard that when +an American forest is cut down, a very different vegetation springs up; +but it has been observed that the trees now growing on the ancient +Indian mounds, in the Southern United States, display the same beautiful +diversity and proportion of kinds as in the surrounding virgin forests. +What a struggle between the several kinds of trees must here have gone +on during long centuries, each annually scattering its seeds by the +thousand; what war between insect and insect—between insects, snails, +and other animals with birds and beasts of prey—all striving to +increase, and all feeding on each other or on the trees or their seeds +and seedlings, or on the other plants which first clothed the ground and +thus checked the growth of the trees! Throw up a handful of feathers, +and all must fall to the ground according to definite laws; but how +simple is this problem compared to the action and reaction of the innumerable plants and animals which have determined, in the course of -centuries, the proportional numbers and kinds of trees now growing on the old -Indian ruins! - -The dependency of one organic being on another, as of a parasite on its prey, -lies generally between beings remote in the scale of nature. This is often the -case with those which may strictly be said to struggle with each other for -existence, as in the case of locusts and grass-feeding quadrupeds. But the -struggle almost invariably will be most severe between the individuals of the -same species, for they frequent the same districts, require the same food, and -are exposed to the same dangers. In the case of varieties of the same species, -the struggle will generally be almost equally severe, and we sometimes see the -contest soon decided: for instance, if several varieties of wheat be sown -together, and the mixed seed be resown, some of the varieties which best suit -the soil or climate, or are naturally the most fertile, will beat the others -and so yield more seed, and will consequently in a few years quite supplant the -other varieties. To keep up a mixed stock of even such extremely close -varieties as the variously coloured sweet-peas, they must be each year -harvested separately, and the seed then mixed in due proportion, otherwise the -weaker kinds will steadily decrease in numbers and disappear. So again with the -varieties of sheep: it has been asserted that certain mountain-varieties will -starve out other mountain-varieties, so that they cannot be kept together. The -same result has followed from keeping together different varieties of the -medicinal leech. It may even be doubted whether the varieties of any one of our -domestic plants or animals have so exactly the same strength, habits, and -constitution, that the original proportions of a mixed stock could be kept up -for half a dozen generations, if they were allowed to struggle together, like -beings in a state of nature, and if the seed or young were not annually sorted. - -As species of the same genus have usually, though by no means invariably, some -similarity in habits and constitution, and always in structure, the struggle -will generally be more severe between species of the same genus, when they come -into competition with each other, than between species of distinct genera. We -see this in the recent extension over parts of the United States of one species -of swallow having caused the decrease of another species. The recent increase -of the missel-thrush in parts of Scotland has caused the decrease of the -song-thrush. How frequently we hear of one species of rat taking the place of -another species under the most different climates! In Russia the small Asiatic -cockroach has everywhere driven before it its great congener. One species of -charlock will supplant another, and so in other cases. We can dimly see why the -competition should be most severe between allied forms, which fill nearly the -same place in the economy of nature; but probably in no one case could we -precisely say why one species has been victorious over another in the great -battle of life. +centuries, the proportional numbers and kinds of trees now growing on +the old Indian ruins! + +The dependency of one organic being on another, as of a parasite on its +prey, lies generally between beings remote in the scale of nature. This +is often the case with those which may strictly be said to struggle with +each other for existence, as in the case of locusts and grass-feeding +quadrupeds. But the struggle almost invariably will be most severe +between the individuals of the same species, for they frequent the same +districts, require the same food, and are exposed to the same dangers. +In the case of varieties of the same species, the struggle will +generally be almost equally severe, and we sometimes see the contest +soon decided: for instance, if several varieties of wheat be sown +together, and the mixed seed be resown, some of the varieties which best +suit the soil or climate, or are naturally the most fertile, will beat +the others and so yield more seed, and will consequently in a few years +quite supplant the other varieties. To keep up a mixed stock of even +such extremely close varieties as the variously coloured sweet-peas, +they must be each year harvested separately, and the seed then mixed in +due proportion, otherwise the weaker kinds will steadily decrease in +numbers and disappear. So again with the varieties of sheep: it has been +asserted that certain mountain-varieties will starve out other +mountain-varieties, so that they cannot be kept together. The same +result has followed from keeping together different varieties of the +medicinal leech. It may even be doubted whether the varieties of any one +of our domestic plants or animals have so exactly the same strength, +habits, and constitution, that the original proportions of a mixed stock +could be kept up for half a dozen generations, if they were allowed to +struggle together, like beings in a state of nature, and if the seed or +young were not annually sorted. + +As species of the same genus have usually, though by no means +invariably, some similarity in habits and constitution, and always in +structure, the struggle will generally be more severe between species of +the same genus, when they come into competition with each other, than +between species of distinct genera. We see this in the recent extension +over parts of the United States of one species of swallow having caused +the decrease of another species. The recent increase of the +missel-thrush in parts of Scotland has caused the decrease of the +song-thrush. How frequently we hear of one species of rat taking the +place of another species under the most different climates! In Russia +the small Asiatic cockroach has everywhere driven before it its great +congener. One species of charlock will supplant another, and so in other +cases. We can dimly see why the competition should be most severe +between allied forms, which fill nearly the same place in the economy of +nature; but probably in no one case could we precisely say why one +species has been victorious over another in the great battle of life. A corollary of the highest importance may be deduced from the foregoing -remarks, namely, that the structure of every organic being is related, in the -most essential yet often hidden manner, to that of all other organic beings, -with which it comes into competition for food or residence, or from which it -has to escape, or on which it preys. This is obvious in the structure of the -teeth and talons of the tiger; and in that of the legs and claws of the -parasite which clings to the hair on the tiger’s body. But in the beautifully -plumed seed of the dandelion, and in the flattened and fringed legs of the -water-beetle, the relation seems at first confined to the elements of air and -water. Yet the advantage of plumed seeds no doubt stands in the closest -relation to the land being already thickly clothed by other plants; so that the -seeds may be widely distributed and fall on unoccupied ground. In the -water-beetle, the structure of its legs, so well adapted for diving, allows it -to compete with other aquatic insects, to hunt for its own prey, and to escape -serving as prey to other animals. - -The store of nutriment laid up within the seeds of many plants seems at first -sight to have no sort of relation to other plants. But from the strong growth -of young plants produced from such seeds (as peas and beans), when sown in the -midst of long grass, I suspect that the chief use of the nutriment in the seed -is to favour the growth of the young seedling, whilst struggling with other -plants growing vigorously all around. - -Look at a plant in the midst of its range, why does it not double or quadruple -its numbers? We know that it can perfectly well withstand a little more heat or -cold, dampness or dryness, for elsewhere it ranges into slightly hotter or -colder, damper or drier districts. In this case we can clearly see that if we -wished in imagination to give the plant the power of increasing in number, we -should have to give it some advantage over its competitors, or over the animals -which preyed on it. On the confines of its geographical range, a change of -constitution with respect to climate would clearly be an advantage to our -plant; but we have reason to believe that only a few plants or animals range so -far, that they are destroyed by the rigour of the climate alone. Not until we -reach the extreme confines of life, in the arctic regions or on the borders of -an utter desert, will competition cease. The land may be extremely cold or dry, -yet there will be competition between some few species, or between the -individuals of the same species, for the warmest or dampest spots. - -Hence, also, we can see that when a plant or animal is placed in a new country -amongst new competitors, though the climate may be exactly the same as in its -former home, yet the conditions of its life will generally be changed in an -essential manner. If we wished to increase its average numbers in its new home, -we should have to modify it in a different way to what we should have done in -its native country; for we should have to give it some advantage over a -different set of competitors or enemies. - -It is good thus to try in our imagination to give any form some advantage over -another. Probably in no single instance should we know what to do, so as to -succeed. It will convince us of our ignorance on the mutual relations of all -organic beings; a conviction as necessary, as it seems to be difficult to -acquire. All that we can do, is to keep steadily in mind that each organic -being is striving to increase at a geometrical ratio; that each at some period -of its life, during some season of the year, during each generation or at -intervals, has to struggle for life, and to suffer great destruction. When we -reflect on this struggle, we may console ourselves with the full belief, that -the war of nature is not incessant, that no fear is felt, that death is -generally prompt, and that the vigorous, the healthy, and the happy survive and -multiply. - -CHAPTER IV. -NATURAL SELECTION. +remarks, namely, that the structure of every organic being is related, +in the most essential yet often hidden manner, to that of all other +organic beings, with which it comes into competition for food or +residence, or from which it has to escape, or on which it preys. This is +obvious in the structure of the teeth and talons of the tiger; and in +that of the legs and claws of the parasite which clings to the hair on +the tiger’s body. But in the beautifully plumed seed of the dandelion, +and in the flattened and fringed legs of the water-beetle, the relation +seems at first confined to the elements of air and water. Yet the +advantage of plumed seeds no doubt stands in the closest relation to the +land being already thickly clothed by other plants; so that the seeds +may be widely distributed and fall on unoccupied ground. In the +water-beetle, the structure of its legs, so well adapted for diving, +allows it to compete with other aquatic insects, to hunt for its own +prey, and to escape serving as prey to other animals. + +The store of nutriment laid up within the seeds of many plants seems at +first sight to have no sort of relation to other plants. But from the +strong growth of young plants produced from such seeds (as peas and +beans), when sown in the midst of long grass, I suspect that the chief +use of the nutriment in the seed is to favour the growth of the young +seedling, whilst struggling with other plants growing vigorously all +around. + +Look at a plant in the midst of its range, why does it not double or +quadruple its numbers? We know that it can perfectly well withstand a +little more heat or cold, dampness or dryness, for elsewhere it ranges +into slightly hotter or colder, damper or drier districts. In this case +we can clearly see that if we wished in imagination to give the plant +the power of increasing in number, we should have to give it some +advantage over its competitors, or over the animals which preyed on it. +On the confines of its geographical range, a change of constitution with +respect to climate would clearly be an advantage to our plant; but we +have reason to believe that only a few plants or animals range so far, +that they are destroyed by the rigour of the climate alone. Not until we +reach the extreme confines of life, in the arctic regions or on the +borders of an utter desert, will competition cease. The land may be +extremely cold or dry, yet there will be competition between some few +species, or between the individuals of the same species, for the warmest +or dampest spots. + +Hence, also, we can see that when a plant or animal is placed in a new +country amongst new competitors, though the climate may be exactly the +same as in its former home, yet the conditions of its life will +generally be changed in an essential manner. If we wished to increase +its average numbers in its new home, we should have to modify it in a +different way to what we should have done in its native country; for we +should have to give it some advantage over a different set of +competitors or enemies. + +It is good thus to try in our imagination to give any form some +advantage over another. Probably in no single instance should we know +what to do, so as to succeed. It will convince us of our ignorance on +the mutual relations of all organic beings; a conviction as necessary, +as it seems to be difficult to acquire. All that we can do, is to keep +steadily in mind that each organic being is striving to increase at a +geometrical ratio; that each at some period of its life, during some +season of the year, during each generation or at intervals, has to +struggle for life, and to suffer great destruction. When we reflect on +this struggle, we may console ourselves with the full belief, that the +war of nature is not incessant, that no fear is felt, that death is +generally prompt, and that the vigorous, the healthy, and the happy +survive and multiply. + +CHAPTER IV. NATURAL SELECTION. Natural Selection: its power compared with man’s selection, its power on -characters of trifling importance, its power at all ages and on both sexes. -Sexual Selection. On the generality of intercrosses between individuals of the -same species. Circumstances favourable and unfavourable to Natural Selection, -namely, intercrossing, isolation, number of individuals. Slow action. -Extinction caused by Natural Selection. Divergence of Character, related to the -diversity of inhabitants of any small area, and to naturalisation. Action of -Natural Selection, through Divergence of Character and Extinction, on the -descendants from a common parent. Explains the Grouping of all organic beings. - -How will the struggle for existence, discussed too briefly in the last chapter, -act in regard to variation? Can the principle of selection, which we have seen -is so potent in the hands of man, apply in nature? I think we shall see that it -can act most effectually. Let it be borne in mind in what an endless number of -strange peculiarities our domestic productions, and, in a lesser degree, those -under nature, vary; and how strong the hereditary tendency is. Under -domestication, it may be truly said that the whole organisation becomes in some -degree plastic. Let it be borne in mind how infinitely complex and -close-fitting are the mutual relations of all organic beings to each other and -to their physical conditions of life. Can it, then, be thought improbable, -seeing that variations useful to man have undoubtedly occurred, that other -variations useful in some way to each being in the great and complex battle of -life, should sometimes occur in the course of thousands of generations? If such -do occur, can we doubt (remembering that many more individuals are born than -can possibly survive) that individuals having any advantage, however slight, -over others, would have the best chance of surviving and of procreating their -kind? On the other hand, we may feel sure that any variation in the least -degree injurious would be rigidly destroyed. This preservation of favourable -variations and the rejection of injurious variations, I call Natural Selection. -Variations neither useful nor injurious would not be affected by natural -selection, and would be left a fluctuating element, as perhaps we see in the +characters of trifling importance, its power at all ages and on both +sexes. Sexual Selection. On the generality of intercrosses between +individuals of the same species. Circumstances favourable and +unfavourable to Natural Selection, namely, intercrossing, isolation, +number of individuals. Slow action. Extinction caused by Natural +Selection. Divergence of Character, related to the diversity of +inhabitants of any small area, and to naturalisation. Action of Natural +Selection, through Divergence of Character and Extinction, on the +descendants from a common parent. Explains the Grouping of all organic +beings. + +How will the struggle for existence, discussed too briefly in the last +chapter, act in regard to variation? Can the principle of selection, +which we have seen is so potent in the hands of man, apply in nature? I +think we shall see that it can act most effectually. Let it be borne in +mind in what an endless number of strange peculiarities our domestic +productions, and, in a lesser degree, those under nature, vary; and how +strong the hereditary tendency is. Under domestication, it may be truly +said that the whole organisation becomes in some degree plastic. Let it +be borne in mind how infinitely complex and close-fitting are the mutual +relations of all organic beings to each other and to their physical +conditions of life. Can it, then, be thought improbable, seeing that +variations useful to man have undoubtedly occurred, that other +variations useful in some way to each being in the great and complex +battle of life, should sometimes occur in the course of thousands of +generations? If such do occur, can we doubt (remembering that many more +individuals are born than can possibly survive) that individuals having +any advantage, however slight, over others, would have the best chance +of surviving and of procreating their kind? On the other hand, we may +feel sure that any variation in the least degree injurious would be +rigidly destroyed. This preservation of favourable variations and the +rejection of injurious variations, I call Natural Selection. Variations +neither useful nor injurious would not be affected by natural selection, +and would be left a fluctuating element, as perhaps we see in the species called polymorphic. -We shall best understand the probable course of natural selection by taking the -case of a country undergoing some physical change, for instance, of climate. -The proportional numbers of its inhabitants would almost immediately undergo a -change, and some species might become extinct. We may conclude, from what we -have seen of the intimate and complex manner in which the inhabitants of each -country are bound together, that any change in the numerical proportions of -some of the inhabitants, independently of the change of climate itself, would -most seriously affect many of the others. If the country were open on its -borders, new forms would certainly immigrate, and this also would seriously -disturb the relations of some of the former inhabitants. Let it be remembered -how powerful the influence of a single introduced tree or mammal has been shown -to be. But in the case of an island, or of a country partly surrounded by -barriers, into which new and better adapted forms could not freely enter, we -should then have places in the economy of nature which would assuredly be -better filled up, if some of the original inhabitants were in some manner -modified; for, had the area been open to immigration, these same places would -have been seized on by intruders. In such case, every slight modification, -which in the course of ages chanced to arise, and which in any way favoured the -individuals of any of the species, by better adapting them to their altered -conditions, would tend to be preserved; and natural selection would thus have -free scope for the work of improvement. - -We have reason to believe, as stated in the first chapter, that a change in the -conditions of life, by specially acting on the reproductive system, causes or -increases variability; and in the foregoing case the conditions of life are -supposed to have undergone a change, and this would manifestly be favourable to -natural selection, by giving a better chance of profitable variations -occurring; and unless profitable variations do occur, natural selection can do -nothing. Not that, as I believe, any extreme amount of variability is -necessary; as man can certainly produce great results by adding up in any given -direction mere individual differences, so could Nature, but far more easily, -from having incomparably longer time at her disposal. Nor do I believe that any -great physical change, as of climate, or any unusual degree of isolation to -check immigration, is actually necessary to produce new and unoccupied places -for natural selection to fill up by modifying and improving some of the varying -inhabitants. For as all the inhabitants of each country are struggling together -with nicely balanced forces, extremely slight modifications in the structure or -habits of one inhabitant would often give it an advantage over others; and -still further modifications of the same kind would often still further increase -the advantage. No country can be named in which all the native inhabitants are -now so perfectly adapted to each other and to the physical conditions under -which they live, that none of them could anyhow be improved; for in all -countries, the natives have been so far conquered by naturalised productions, -that they have allowed foreigners to take firm possession of the land. And as -foreigners have thus everywhere beaten some of the natives, we may safely -conclude that the natives might have been modified with advantage, so as to -have better resisted such intruders. - -As man can produce and certainly has produced a great result by his methodical -and unconscious means of selection, what may not nature effect? Man can act -only on external and visible characters: nature cares nothing for appearances, -except in so far as they may be useful to any being. She can act on every -internal organ, on every shade of constitutional difference, on the whole -machinery of life. Man selects only for his own good; Nature only for that of -the being which she tends. Every selected character is fully exercised by her; -and the being is placed under well-suited conditions of life. Man keeps the -natives of many climates in the same country; he seldom exercises each selected -character in some peculiar and fitting manner; he feeds a long and a short -beaked pigeon on the same food; he does not exercise a long-backed or -long-legged quadruped in any peculiar manner; he exposes sheep with long and -short wool to the same climate. He does not allow the most vigorous males to -struggle for the females. He does not rigidly destroy all inferior animals, but -protects during each varying season, as far as lies in his power, all his -productions. He often begins his selection by some half-monstrous form; or at -least by some modification prominent enough to catch his eye, or to be plainly -useful to him. Under nature, the slightest difference of structure or -constitution may well turn the nicely-balanced scale in the struggle for life, -and so be preserved. How fleeting are the wishes and efforts of man! how short -his time! and consequently how poor will his products be, compared with those -accumulated by nature during whole geological periods. Can we wonder, then, -that nature’s productions should be far “truer” in character than man’s -productions; that they should be infinitely better adapted to the most complex -conditions of life, and should plainly bear the stamp of far higher -workmanship? +We shall best understand the probable course of natural selection by +taking the case of a country undergoing some physical change, for +instance, of climate. The proportional numbers of its inhabitants would +almost immediately undergo a change, and some species might become +extinct. We may conclude, from what we have seen of the intimate and +complex manner in which the inhabitants of each country are bound +together, that any change in the numerical proportions of some of the +inhabitants, independently of the change of climate itself, would most +seriously affect many of the others. If the country were open on its +borders, new forms would certainly immigrate, and this also would +seriously disturb the relations of some of the former inhabitants. Let +it be remembered how powerful the influence of a single introduced tree +or mammal has been shown to be. But in the case of an island, or of a +country partly surrounded by barriers, into which new and better adapted +forms could not freely enter, we should then have places in the economy +of nature which would assuredly be better filled up, if some of the +original inhabitants were in some manner modified; for, had the area +been open to immigration, these same places would have been seized on by +intruders. In such case, every slight modification, which in the course +of ages chanced to arise, and which in any way favoured the individuals +of any of the species, by better adapting them to their altered +conditions, would tend to be preserved; and natural selection would thus +have free scope for the work of improvement. + +We have reason to believe, as stated in the first chapter, that a change +in the conditions of life, by specially acting on the reproductive +system, causes or increases variability; and in the foregoing case the +conditions of life are supposed to have undergone a change, and this +would manifestly be favourable to natural selection, by giving a better +chance of profitable variations occurring; and unless profitable +variations do occur, natural selection can do nothing. Not that, as I +believe, any extreme amount of variability is necessary; as man can +certainly produce great results by adding up in any given direction mere +individual differences, so could Nature, but far more easily, from +having incomparably longer time at her disposal. Nor do I believe that +any great physical change, as of climate, or any unusual degree of +isolation to check immigration, is actually necessary to produce new and +unoccupied places for natural selection to fill up by modifying and +improving some of the varying inhabitants. For as all the inhabitants of +each country are struggling together with nicely balanced forces, +extremely slight modifications in the structure or habits of one +inhabitant would often give it an advantage over others; and still +further modifications of the same kind would often still further +increase the advantage. No country can be named in which all the native +inhabitants are now so perfectly adapted to each other and to the +physical conditions under which they live, that none of them could +anyhow be improved; for in all countries, the natives have been so far +conquered by naturalised productions, that they have allowed foreigners +to take firm possession of the land. And as foreigners have thus +everywhere beaten some of the natives, we may safely conclude that the +natives might have been modified with advantage, so as to have better +resisted such intruders. + +As man can produce and certainly has produced a great result by his +methodical and unconscious means of selection, what may not nature +effect? Man can act only on external and visible characters: nature +cares nothing for appearances, except in so far as they may be useful to +any being. She can act on every internal organ, on every shade of +constitutional difference, on the whole machinery of life. Man selects +only for his own good; Nature only for that of the being which she +tends. Every selected character is fully exercised by her; and the being +is placed under well-suited conditions of life. Man keeps the natives of +many climates in the same country; he seldom exercises each selected +character in some peculiar and fitting manner; he feeds a long and a +short beaked pigeon on the same food; he does not exercise a long-backed +or long-legged quadruped in any peculiar manner; he exposes sheep with +long and short wool to the same climate. He does not allow the most +vigorous males to struggle for the females. He does not rigidly destroy +all inferior animals, but protects during each varying season, as far as +lies in his power, all his productions. He often begins his selection by +some half-monstrous form; or at least by some modification prominent +enough to catch his eye, or to be plainly useful to him. Under nature, +the slightest difference of structure or constitution may well turn the +nicely-balanced scale in the struggle for life, and so be preserved. How +fleeting are the wishes and efforts of man! how short his time! and +consequently how poor will his products be, compared with those +accumulated by nature during whole geological periods. Can we wonder, +then, that nature’s productions should be far “truer” in character than +man’s productions; that they should be infinitely better adapted to the +most complex conditions of life, and should plainly bear the stamp of +far higher workmanship? It may be said that natural selection is daily and hourly scrutinising, -throughout the world, every variation, even the slightest; rejecting that which -is bad, preserving and adding up all that is good; silently and insensibly -working, whenever and wherever opportunity offers, at the improvement of each -organic being in relation to its organic and inorganic conditions of life. We -see nothing of these slow changes in progress, until the hand of time has -marked the long lapse of ages, and then so imperfect is our view into long past -geological ages, that we only see that the forms of life are now different from -what they formerly were. - -Although natural selection can act only through and for the good of each being, -yet characters and structures, which we are apt to consider as of very trifling -importance, may thus be acted on. When we see leaf-eating insects green, and -bark-feeders mottled-grey; the alpine ptarmigan white in winter, the red-grouse -the colour of heather, and the black-grouse that of peaty earth, we must -believe that these tints are of service to these birds and insects in -preserving them from danger. Grouse, if not destroyed at some period of their -lives, would increase in countless numbers; they are known to suffer largely -from birds of prey; and hawks are guided by eyesight to their prey,—so much so, -that on parts of the Continent persons are warned not to keep white pigeons, as -being the most liable to destruction. Hence I can see no reason to doubt that -natural selection might be most effective in giving the proper colour to each -kind of grouse, and in keeping that colour, when once acquired, true and -constant. Nor ought we to think that the occasional destruction of an animal of -any particular colour would produce little effect: we should remember how -essential it is in a flock of white sheep to destroy every lamb with the -faintest trace of black. In plants the down on the fruit and the colour of the -flesh are considered by botanists as characters of the most trifling -importance: yet we hear from an excellent horticulturist, Downing, that in the -United States smooth-skinned fruits suffer far more from a beetle, a curculio, -than those with down; that purple plums suffer far more from a certain disease -than yellow plums; whereas another disease attacks yellow-fleshed peaches far -more than those with other coloured flesh. If, with all the aids of art, these -slight differences make a great difference in cultivating the several -varieties, assuredly, in a state of nature, where the trees would have to -struggle with other trees and with a host of enemies, such differences would -effectually settle which variety, whether a smooth or downy, a yellow or purple -fleshed fruit, should succeed. - -In looking at many small points of difference between species, which, as far as -our ignorance permits us to judge, seem to be quite unimportant, we must not -forget that climate, food, etc., probably produce some slight and direct -effect. It is, however, far more necessary to bear in mind that there are many -unknown laws of correlation of growth, which, when one part of the organisation -is modified through variation, and the modifications are accumulated by natural -selection for the good of the being, will cause other modifications, often of -the most unexpected nature. +throughout the world, every variation, even the slightest; rejecting +that which is bad, preserving and adding up all that is good; silently +and insensibly working, whenever and wherever opportunity offers, at the +improvement of each organic being in relation to its organic and +inorganic conditions of life. We see nothing of these slow changes in +progress, until the hand of time has marked the long lapse of ages, and +then so imperfect is our view into long past geological ages, that we +only see that the forms of life are now different from what they +formerly were. + +Although natural selection can act only through and for the good of each +being, yet characters and structures, which we are apt to consider as of +very trifling importance, may thus be acted on. When we see leaf-eating +insects green, and bark-feeders mottled-grey; the alpine ptarmigan white +in winter, the red-grouse the colour of heather, and the black-grouse +that of peaty earth, we must believe that these tints are of service to +these birds and insects in preserving them from danger. Grouse, if not +destroyed at some period of their lives, would increase in countless +numbers; they are known to suffer largely from birds of prey; and hawks +are guided by eyesight to their prey,—so much so, that on parts of the +Continent persons are warned not to keep white pigeons, as being the +most liable to destruction. Hence I can see no reason to doubt that +natural selection might be most effective in giving the proper colour to +each kind of grouse, and in keeping that colour, when once acquired, +true and constant. Nor ought we to think that the occasional destruction +of an animal of any particular colour would produce little effect: we +should remember how essential it is in a flock of white sheep to destroy +every lamb with the faintest trace of black. In plants the down on the +fruit and the colour of the flesh are considered by botanists as +characters of the most trifling importance: yet we hear from an +excellent horticulturist, Downing, that in the United States +smooth-skinned fruits suffer far more from a beetle, a curculio, than +those with down; that purple plums suffer far more from a certain +disease than yellow plums; whereas another disease attacks +yellow-fleshed peaches far more than those with other coloured flesh. +If, with all the aids of art, these slight differences make a great +difference in cultivating the several varieties, assuredly, in a state +of nature, where the trees would have to struggle with other trees and +with a host of enemies, such differences would effectually settle which +variety, whether a smooth or downy, a yellow or purple fleshed fruit, +should succeed. + +In looking at many small points of difference between species, which, as +far as our ignorance permits us to judge, seem to be quite unimportant, +we must not forget that climate, food, etc., probably produce some +slight and direct effect. It is, however, far more necessary to bear in +mind that there are many unknown laws of correlation of growth, which, +when one part of the organisation is modified through variation, and the +modifications are accumulated by natural selection for the good of the +being, will cause other modifications, often of the most unexpected +nature. As we see that those variations which under domestication appear at any particular period of life, tend to reappear in the offspring at the same -period;—for instance, in the seeds of the many varieties of our culinary and -agricultural plants; in the caterpillar and cocoon stages of the varieties of -the silkworm; in the eggs of poultry, and in the colour of the down of their -chickens; in the horns of our sheep and cattle when nearly adult;—so in a state -of nature, natural selection will be enabled to act on and modify organic -beings at any age, by the accumulation of profitable variations at that age, -and by their inheritance at a corresponding age. If it profit a plant to have -its seeds more and more widely disseminated by the wind, I can see no greater -difficulty in this being effected through natural selection, than in the -cotton-planter increasing and improving by selection the down in the pods on -his cotton-trees. Natural selection may modify and adapt the larva of an insect -to a score of contingencies, wholly different from those which concern the -mature insect. These modifications will no doubt affect, through the laws of -correlation, the structure of the adult; and probably in the case of those -insects which live only for a few hours, and which never feed, a large part of -their structure is merely the correlated result of successive changes in the -structure of their larvæ. So, conversely, modifications in the adult will -probably often affect the structure of the larva; but in all cases natural -selection will ensure that modifications consequent on other modifications at a -different period of life, shall not be in the least degree injurious: for if -they became so, they would cause the extinction of the species. - -Natural selection will modify the structure of the young in relation to the -parent, and of the parent in relation to the young. In social animals it will -adapt the structure of each individual for the benefit of the community; if -each in consequence profits by the selected change. What natural selection -cannot do, is to modify the structure of one species, without giving it any -advantage, for the good of another species; and though statements to this -effect may be found in works of natural history, I cannot find one case which -will bear investigation. A structure used only once in an animal’s whole life, -if of high importance to it, might be modified to any extent by natural -selection; for instance, the great jaws possessed by certain insects, and used -exclusively for opening the cocoon—or the hard tip to the beak of nestling -birds, used for breaking the egg. It has been asserted, that of the best -short-beaked tumbler-pigeons more perish in the egg than are able to get out of -it; so that fanciers assist in the act of hatching. Now, if nature had to make -the beak of a full-grown pigeon very short for the bird’s own advantage, the -process of modification would be very slow, and there would be simultaneously -the most rigorous selection of the young birds within the egg, which had the -most powerful and hardest beaks, for all with weak beaks would inevitably -perish: or, more delicate and more easily broken shells might be selected, the -thickness of the shell being known to vary like every other structure. - -Sexual Selection.—Inasmuch as peculiarities often appear under domestication in -one sex and become hereditarily attached to that sex, the same fact probably -occurs under nature, and if so, natural selection will be able to modify one -sex in its functional relations to the other sex, or in relation to wholly -different habits of life in the two sexes, as is sometimes the case with -insects. And this leads me to say a few words on what I call Sexual Selection. -This depends, not on a struggle for existence, but on a struggle between the -males for possession of the females; the result is not death to the -unsuccessful competitor, but few or no offspring. Sexual selection is, -therefore, less rigorous than natural selection. Generally, the most vigorous -males, those which are best fitted for their places in nature, will leave most -progeny. But in many cases, victory will depend not on general vigour, but on -having special weapons, confined to the male sex. A hornless stag or spurless -cock would have a poor chance of leaving offspring. Sexual selection by always -allowing the victor to breed might surely give indomitable courage, length to -the spur, and strength to the wing to strike in the spurred leg, as well as the -brutal cock-fighter, who knows well that he can improve his breed by careful -selection of the best cocks. How low in the scale of nature this law of battle -descends, I know not; male alligators have been described as fighting, -bellowing, and whirling round, like Indians in a war-dance, for the possession -of the females; male salmons have been seen fighting all day long; male -stag-beetles often bear wounds from the huge mandibles of other males. The war -is, perhaps, severest between the males of polygamous animals, and these seem -oftenest provided with special weapons. The males of carnivorous animals are -already well armed; though to them and to others, special means of defence may -be given through means of sexual selection, as the mane to the lion, the -shoulder-pad to the boar, and the hooked jaw to the male salmon; for the shield -may be as important for victory, as the sword or spear. - -Amongst birds, the contest is often of a more peaceful character. All those who -have attended to the subject, believe that there is the severest rivalry -between the males of many species to attract by singing the females. The -rock-thrush of Guiana, birds of Paradise, and some others, congregate; and -successive males display their gorgeous plumage and perform strange antics -before the females, which standing by as spectators, at last choose the most -attractive partner. Those who have closely attended to birds in confinement -well know that they often take individual preferences and dislikes: thus Sir R. -Heron has described how one pied peacock was eminently attractive to all his -hen birds. It may appear childish to attribute any effect to such apparently -weak means: I cannot here enter on the details necessary to support this view; -but if man can in a short time give elegant carriage and beauty to his bantams, -according to his standard of beauty, I can see no good reason to doubt that -female birds, by selecting, during thousands of generations, the most melodious -or beautiful males, according to their standard of beauty, might produce a -marked effect. I strongly suspect that some well-known laws with respect to the -plumage of male and female birds, in comparison with the plumage of the young, -can be explained on the view of plumage having been chiefly modified by sexual -selection, acting when the birds have come to the breeding age or during the +period;—for instance, in the seeds of the many varieties of our culinary +and agricultural plants; in the caterpillar and cocoon stages of the +varieties of the silkworm; in the eggs of poultry, and in the colour of +the down of their chickens; in the horns of our sheep and cattle when +nearly adult;—so in a state of nature, natural selection will be enabled +to act on and modify organic beings at any age, by the accumulation of +profitable variations at that age, and by their inheritance at a +corresponding age. If it profit a plant to have its seeds more and more +widely disseminated by the wind, I can see no greater difficulty in this +being effected through natural selection, than in the cotton-planter +increasing and improving by selection the down in the pods on his +cotton-trees. Natural selection may modify and adapt the larva of an +insect to a score of contingencies, wholly different from those which +concern the mature insect. These modifications will no doubt affect, +through the laws of correlation, the structure of the adult; and +probably in the case of those insects which live only for a few hours, +and which never feed, a large part of their structure is merely the +correlated result of successive changes in the structure of their larvæ. +So, conversely, modifications in the adult will probably often affect +the structure of the larva; but in all cases natural selection will +ensure that modifications consequent on other modifications at a +different period of life, shall not be in the least degree injurious: +for if they became so, they would cause the extinction of the species. + +Natural selection will modify the structure of the young in relation to +the parent, and of the parent in relation to the young. In social +animals it will adapt the structure of each individual for the benefit +of the community; if each in consequence profits by the selected change. +What natural selection cannot do, is to modify the structure of one +species, without giving it any advantage, for the good of another +species; and though statements to this effect may be found in works of +natural history, I cannot find one case which will bear investigation. A +structure used only once in an animal’s whole life, if of high +importance to it, might be modified to any extent by natural selection; +for instance, the great jaws possessed by certain insects, and used +exclusively for opening the cocoon—or the hard tip to the beak of +nestling birds, used for breaking the egg. It has been asserted, that of +the best short-beaked tumbler-pigeons more perish in the egg than are +able to get out of it; so that fanciers assist in the act of hatching. +Now, if nature had to make the beak of a full-grown pigeon very short +for the bird’s own advantage, the process of modification would be very +slow, and there would be simultaneously the most rigorous selection of +the young birds within the egg, which had the most powerful and hardest +beaks, for all with weak beaks would inevitably perish: or, more +delicate and more easily broken shells might be selected, the thickness +of the shell being known to vary like every other structure. + +Sexual Selection.—Inasmuch as peculiarities often appear under +domestication in one sex and become hereditarily attached to that sex, +the same fact probably occurs under nature, and if so, natural selection +will be able to modify one sex in its functional relations to the other +sex, or in relation to wholly different habits of life in the two sexes, +as is sometimes the case with insects. And this leads me to say a few +words on what I call Sexual Selection. This depends, not on a struggle +for existence, but on a struggle between the males for possession of the +females; the result is not death to the unsuccessful competitor, but few +or no offspring. Sexual selection is, therefore, less rigorous than +natural selection. Generally, the most vigorous males, those which are +best fitted for their places in nature, will leave most progeny. But in +many cases, victory will depend not on general vigour, but on having +special weapons, confined to the male sex. A hornless stag or spurless +cock would have a poor chance of leaving offspring. Sexual selection by +always allowing the victor to breed might surely give indomitable +courage, length to the spur, and strength to the wing to strike in the +spurred leg, as well as the brutal cock-fighter, who knows well that he +can improve his breed by careful selection of the best cocks. How low in +the scale of nature this law of battle descends, I know not; male +alligators have been described as fighting, bellowing, and whirling +round, like Indians in a war-dance, for the possession of the females; +male salmons have been seen fighting all day long; male stag-beetles +often bear wounds from the huge mandibles of other males. The war is, +perhaps, severest between the males of polygamous animals, and these +seem oftenest provided with special weapons. The males of carnivorous +animals are already well armed; though to them and to others, special +means of defence may be given through means of sexual selection, as the +mane to the lion, the shoulder-pad to the boar, and the hooked jaw to +the male salmon; for the shield may be as important for victory, as the +sword or spear. + +Amongst birds, the contest is often of a more peaceful character. All +those who have attended to the subject, believe that there is the +severest rivalry between the males of many species to attract by singing +the females. The rock-thrush of Guiana, birds of Paradise, and some +others, congregate; and successive males display their gorgeous plumage +and perform strange antics before the females, which standing by as +spectators, at last choose the most attractive partner. Those who have +closely attended to birds in confinement well know that they often take +individual preferences and dislikes: thus Sir R. Heron has described +how one pied peacock was eminently attractive to all his hen birds. It +may appear childish to attribute any effect to such apparently weak +means: I cannot here enter on the details necessary to support this +view; but if man can in a short time give elegant carriage and beauty to +his bantams, according to his standard of beauty, I can see no good +reason to doubt that female birds, by selecting, during thousands of +generations, the most melodious or beautiful males, according to their +standard of beauty, might produce a marked effect. I strongly suspect +that some well-known laws with respect to the plumage of male and female +birds, in comparison with the plumage of the young, can be explained on +the view of plumage having been chiefly modified by sexual selection, +acting when the birds have come to the breeding age or during the breeding season; the modifications thus produced being inherited at -corresponding ages or seasons, either by the males alone, or by the males and -females; but I have not space here to enter on this subject. - -Thus it is, as I believe, that when the males and females of any animal have -the same general habits of life, but differ in structure, colour, or ornament, -such differences have been mainly caused by sexual selection; that is, -individual males have had, in successive generations, some slight advantage -over other males, in their weapons, means of defence, or charms; and have -transmitted these advantages to their male offspring. Yet, I would not wish to -attribute all such sexual differences to this agency: for we see peculiarities -arising and becoming attached to the male sex in our domestic animals (as the -wattle in male carriers, horn-like protuberances in the cocks of certain fowls, -etc.), which we cannot believe to be either useful to the males in battle, or -attractive to the females. We see analogous cases under nature, for instance, -the tuft of hair on the breast of the turkey-cock, which can hardly be either -useful or ornamental to this bird;—indeed, had the tuft appeared under -domestication, it would have been called a monstrosity. - -Illustrations of the action of Natural Selection.—In order to make it clear -how, as I believe, natural selection acts, I must beg permission to give one or -two imaginary illustrations. Let us take the case of a wolf, which preys on -various animals, securing some by craft, some by strength, and some by -fleetness; and let us suppose that the fleetest prey, a deer for instance, had -from any change in the country increased in numbers, or that other prey had -decreased in numbers, during that season of the year when the wolf is hardest -pressed for food. I can under such circumstances see no reason to doubt that -the swiftest and slimmest wolves would have the best chance of surviving, and -so be preserved or selected,—provided always that they retained strength to -master their prey at this or at some other period of the year, when they might -be compelled to prey on other animals. I can see no more reason to doubt this, -than that man can improve the fleetness of his greyhounds by careful and -methodical selection, or by that unconscious selection which results from each -man trying to keep the best dogs without any thought of modifying the breed. - -Even without any change in the proportional numbers of the animals on which our -wolf preyed, a cub might be born with an innate tendency to pursue certain -kinds of prey. Nor can this be thought very improbable; for we often observe -great differences in the natural tendencies of our domestic animals; one cat, -for instance, taking to catch rats, another mice; one cat, according to Mr. St. -John, bringing home winged game, another hares or rabbits, and another hunting -on marshy ground and almost nightly catching woodcocks or snipes. The tendency -to catch rats rather than mice is known to be inherited. Now, if any slight -innate change of habit or of structure benefited an individual wolf, it would -have the best chance of surviving and of leaving offspring. Some of its young -would probably inherit the same habits or structure, and by the repetition of -this process, a new variety might be formed which would either supplant or -coexist with the parent-form of wolf. Or, again, the wolves inhabiting a -mountainous district, and those frequenting the lowlands, would naturally be -forced to hunt different prey; and from the continued preservation of the -individuals best fitted for the two sites, two varieties might slowly be -formed. These varieties would cross and blend where they met; but to this -subject of intercrossing we shall soon have to return. I may add, that, -according to Mr. Pierce, there are two varieties of the wolf inhabiting the -Catskill Mountains in the United States, one with a light greyhound-like form, -which pursues deer, and the other more bulky, with shorter legs, which more -frequently attacks the shepherd’s flocks. - -Let us now take a more complex case. Certain plants excrete a sweet juice, -apparently for the sake of eliminating something injurious from their sap: this -is effected by glands at the base of the stipules in some Leguminosæ, and at -the back of the leaf of the common laurel. This juice, though small in -quantity, is greedily sought by insects. Let us now suppose a little sweet -juice or nectar to be excreted by the inner bases of the petals of a flower. In -this case insects in seeking the nectar would get dusted with pollen, and would -certainly often transport the pollen from one flower to the stigma of another -flower. The flowers of two distinct individuals of the same species would thus -get crossed; and the act of crossing, we have good reason to believe (as will -hereafter be more fully alluded to), would produce very vigorous seedlings, -which consequently would have the best chance of flourishing and surviving. -Some of these seedlings would probably inherit the nectar-excreting power. -Those individual flowers which had the largest glands or nectaries, and which -excreted most nectar, would be oftenest visited by insects, and would be -oftenest crossed; and so in the long-run would gain the upper hand. Those -flowers, also, which had their stamens and pistils placed, in relation to the -size and habits of the particular insects which visited them, so as to favour -in any degree the transportal of their pollen from flower to flower, would -likewise be favoured or selected. We might have taken the case of insects -visiting flowers for the sake of collecting pollen instead of nectar; and as -pollen is formed for the sole object of fertilisation, its destruction appears -a simple loss to the plant; yet if a little pollen were carried, at first -occasionally and then habitually, by the pollen-devouring insects from flower -to flower, and a cross thus effected, although nine-tenths of the pollen were -destroyed, it might still be a great gain to the plant; and those individuals -which produced more and more pollen, and had larger and larger anthers, would -be selected. +corresponding ages or seasons, either by the males alone, or by the +males and females; but I have not space here to enter on this subject. + +Thus it is, as I believe, that when the males and females of any animal +have the same general habits of life, but differ in structure, colour, +or ornament, such differences have been mainly caused by sexual +selection; that is, individual males have had, in successive +generations, some slight advantage over other males, in their weapons, +means of defence, or charms; and have transmitted these advantages to +their male offspring. Yet, I would not wish to attribute all such sexual +differences to this agency: for we see peculiarities arising and +becoming attached to the male sex in our domestic animals (as the wattle +in male carriers, horn-like protuberances in the cocks of certain fowls, +etc.), which we cannot believe to be either useful to the males in +battle, or attractive to the females. We see analogous cases under +nature, for instance, the tuft of hair on the breast of the turkey-cock, +which can hardly be either useful or ornamental to this bird;—indeed, +had the tuft appeared under domestication, it would have been called a +monstrosity. + +Illustrations of the action of Natural Selection.—In order to make it +clear how, as I believe, natural selection acts, I must beg permission +to give one or two imaginary illustrations. Let us take the case of a +wolf, which preys on various animals, securing some by craft, some by +strength, and some by fleetness; and let us suppose that the fleetest +prey, a deer for instance, had from any change in the country increased +in numbers, or that other prey had decreased in numbers, during that +season of the year when the wolf is hardest pressed for food. I can +under such circumstances see no reason to doubt that the swiftest and +slimmest wolves would have the best chance of surviving, and so be +preserved or selected,—provided always that they retained strength to +master their prey at this or at some other period of the year, when they +might be compelled to prey on other animals. I can see no more reason to +doubt this, than that man can improve the fleetness of his greyhounds by +careful and methodical selection, or by that unconscious selection which +results from each man trying to keep the best dogs without any thought +of modifying the breed. + +Even without any change in the proportional numbers of the animals on +which our wolf preyed, a cub might be born with an innate tendency to +pursue certain kinds of prey. Nor can this be thought very improbable; +for we often observe great differences in the natural tendencies of our +domestic animals; one cat, for instance, taking to catch rats, another +mice; one cat, according to Mr. St. John, bringing home winged game, +another hares or rabbits, and another hunting on marshy ground and +almost nightly catching woodcocks or snipes. The tendency to catch rats +rather than mice is known to be inherited. Now, if any slight innate +change of habit or of structure benefited an individual wolf, it would +have the best chance of surviving and of leaving offspring. Some of its +young would probably inherit the same habits or structure, and by the +repetition of this process, a new variety might be formed which would +either supplant or coexist with the parent-form of wolf. Or, again, the +wolves inhabiting a mountainous district, and those frequenting the +lowlands, would naturally be forced to hunt different prey; and from the +continued preservation of the individuals best fitted for the two sites, +two varieties might slowly be formed. These varieties would cross and +blend where they met; but to this subject of intercrossing we shall soon +have to return. I may add, that, according to Mr. Pierce, there are two +varieties of the wolf inhabiting the Catskill Mountains in the United +States, one with a light greyhound-like form, which pursues deer, and +the other more bulky, with shorter legs, which more frequently attacks +the shepherd’s flocks. + +Let us now take a more complex case. Certain plants excrete a sweet +juice, apparently for the sake of eliminating something injurious from +their sap: this is effected by glands at the base of the stipules in +some Leguminosæ, and at the back of the leaf of the common laurel. This +juice, though small in quantity, is greedily sought by insects. Let us +now suppose a little sweet juice or nectar to be excreted by the inner +bases of the petals of a flower. In this case insects in seeking the +nectar would get dusted with pollen, and would certainly often transport +the pollen from one flower to the stigma of another flower. The flowers +of two distinct individuals of the same species would thus get crossed; +and the act of crossing, we have good reason to believe (as will +hereafter be more fully alluded to), would produce very vigorous +seedlings, which consequently would have the best chance of flourishing +and surviving. Some of these seedlings would probably inherit the +nectar-excreting power. Those individual flowers which had the largest +glands or nectaries, and which excreted most nectar, would be oftenest +visited by insects, and would be oftenest crossed; and so in the +long-run would gain the upper hand. Those flowers, also, which had their +stamens and pistils placed, in relation to the size and habits of the +particular insects which visited them, so as to favour in any degree the +transportal of their pollen from flower to flower, would likewise be +favoured or selected. We might have taken the case of insects visiting +flowers for the sake of collecting pollen instead of nectar; and as +pollen is formed for the sole object of fertilisation, its destruction +appears a simple loss to the plant; yet if a little pollen were carried, +at first occasionally and then habitually, by the pollen-devouring +insects from flower to flower, and a cross thus effected, although +nine-tenths of the pollen were destroyed, it might still be a great gain +to the plant; and those individuals which produced more and more pollen, +and had larger and larger anthers, would be selected. When our plant, by this process of the continued preservation or natural selection of more and more attractive flowers, had been rendered highly -attractive to insects, they would, unintentionally on their part, regularly -carry pollen from flower to flower; and that they can most effectually do this, -I could easily show by many striking instances. I will give only one—not as a -very striking case, but as likewise illustrating one step in the separation of -the sexes of plants, presently to be alluded to. Some holly-trees bear only -male flowers, which have four stamens producing rather a small quantity of -pollen, and a rudimentary pistil; other holly-trees bear only female flowers; -these have a full-sized pistil, and four stamens with shrivelled anthers, in -which not a grain of pollen can be detected. Having found a female tree exactly -sixty yards from a male tree, I put the stigmas of twenty flowers, taken from -different branches, under the microscope, and on all, without exception, there -were pollen-grains, and on some a profusion of pollen. As the wind had set for -several days from the female to the male tree, the pollen could not thus have -been carried. The weather had been cold and boisterous, and therefore not -favourable to bees, nevertheless every female flower which I examined had been -effectually fertilised by the bees, accidentally dusted with pollen, having -flown from tree to tree in search of nectar. But to return to our imaginary -case: as soon as the plant had been rendered so highly attractive to insects -that pollen was regularly carried from flower to flower, another process might -commence. No naturalist doubts the advantage of what has been called the -“physiological division of labour;” hence we may believe that it would be -advantageous to a plant to produce stamens alone in one flower or on one whole -plant, and pistils alone in another flower or on another plant. In plants under -culture and placed under new conditions of life, sometimes the male organs and -sometimes the female organs become more or less impotent; now if we suppose -this to occur in ever so slight a degree under nature, then as pollen is -already carried regularly from flower to flower, and as a more complete -separation of the sexes of our plant would be advantageous on the principle of -the division of labour, individuals with this tendency more and more increased, -would be continually favoured or selected, until at last a complete separation -of the sexes would be effected. - -Let us now turn to the nectar-feeding insects in our imaginary case: we may -suppose the plant of which we have been slowly increasing the nectar by -continued selection, to be a common plant; and that certain insects depended in -main part on its nectar for food. I could give many facts, showing how anxious -bees are to save time; for instance, their habit of cutting holes and sucking -the nectar at the bases of certain flowers, which they can, with a very little -more trouble, enter by the mouth. Bearing such facts in mind, I can see no -reason to doubt that an accidental deviation in the size and form of the body, -or in the curvature and length of the proboscis, etc., far too slight to be -appreciated by us, might profit a bee or other insect, so that an individual so -characterised would be able to obtain its food more quickly, and so have a -better chance of living and leaving descendants. Its descendants would probably -inherit a tendency to a similar slight deviation of structure. The tubes of the -corollas of the common red and incarnate clovers (Trifolium pratense and -incarnatum) do not on a hasty glance appear to differ in length; yet the -hive-bee can easily suck the nectar out of the incarnate clover, but not out of -the common red clover, which is visited by humble-bees alone; so that whole -fields of the red clover offer in vain an abundant supply of precious nectar to -the hive-bee. Thus it might be a great advantage to the hive-bee to have a -slightly longer or differently constructed proboscis. On the other hand, I have -found by experiment that the fertility of clover greatly depends on bees -visiting and moving parts of the corolla, so as to push the pollen on to the -stigmatic surface. Hence, again, if humble-bees were to become rare in any -country, it might be a great advantage to the red clover to have a shorter or -more deeply divided tube to its corolla, so that the hive-bee could visit its -flowers. Thus I can understand how a flower and a bee might slowly become, -either simultaneously or one after the other, modified and adapted in the most -perfect manner to each other, by the continued preservation of individuals -presenting mutual and slightly favourable deviations of structure. - -I am well aware that this doctrine of natural selection, exemplified in the -above imaginary instances, is open to the same objections which were at first -urged against Sir Charles Lyell’s noble views on “the modern changes of the -earth, as illustrative of geology;” but we now very seldom hear the action, for -instance, of the coast-waves, called a trifling and insignificant cause, when -applied to the excavation of gigantic valleys or to the formation of the -longest lines of inland cliffs. Natural selection can act only by the -preservation and accumulation of infinitesimally small inherited modifications, -each profitable to the preserved being; and as modern geology has almost -banished such views as the excavation of a great valley by a single diluvial -wave, so will natural selection, if it be a true principle, banish the belief -of the continued creation of new organic beings, or of any great and sudden -modification in their structure. - -On the Intercrossing of Individuals.—I must here introduce a short digression. -In the case of animals and plants with separated sexes, it is of course obvious -that two individuals must always unite for each birth; but in the case of -hermaphrodites this is far from obvious. Nevertheless I am strongly inclined to -believe that with all hermaphrodites two individuals, either occasionally or -habitually, concur for the reproduction of their kind. This view, I may add, -was first suggested by Andrew Knight. We shall presently see its importance; -but I must here treat the subject with extreme brevity, though I have the -materials prepared for an ample discussion. All vertebrate animals, all -insects, and some other large groups of animals, pair for each birth. Modern -research has much diminished the number of supposed hermaphrodites, and of real -hermaphrodites a large number pair; that is, two individuals regularly unite -for reproduction, which is all that concerns us. But still there are many -hermaphrodite animals which certainly do not habitually pair, and a vast -majority of plants are hermaphrodites. What reason, it may be asked, is there -for supposing in these cases that two individuals ever concur in reproduction? -As it is impossible here to enter on details, I must trust to some general +attractive to insects, they would, unintentionally on their part, +regularly carry pollen from flower to flower; and that they can most +effectually do this, I could easily show by many striking instances. I +will give only one—not as a very striking case, but as likewise +illustrating one step in the separation of the sexes of plants, +presently to be alluded to. Some holly-trees bear only male flowers, +which have four stamens producing rather a small quantity of pollen, and +a rudimentary pistil; other holly-trees bear only female flowers; these +have a full-sized pistil, and four stamens with shrivelled anthers, in +which not a grain of pollen can be detected. Having found a female tree +exactly sixty yards from a male tree, I put the stigmas of twenty +flowers, taken from different branches, under the microscope, and on +all, without exception, there were pollen-grains, and on some a +profusion of pollen. As the wind had set for several days from the +female to the male tree, the pollen could not thus have been carried. +The weather had been cold and boisterous, and therefore not favourable +to bees, nevertheless every female flower which I examined had been +effectually fertilised by the bees, accidentally dusted with pollen, +having flown from tree to tree in search of nectar. But to return to our +imaginary case: as soon as the plant had been rendered so highly +attractive to insects that pollen was regularly carried from flower to +flower, another process might commence. No naturalist doubts the +advantage of what has been called the “physiological division of +labour;” hence we may believe that it would be advantageous to a plant +to produce stamens alone in one flower or on one whole plant, and +pistils alone in another flower or on another plant. In plants under +culture and placed under new conditions of life, sometimes the male +organs and sometimes the female organs become more or less impotent; now +if we suppose this to occur in ever so slight a degree under nature, +then as pollen is already carried regularly from flower to flower, and +as a more complete separation of the sexes of our plant would be +advantageous on the principle of the division of labour, individuals +with this tendency more and more increased, would be continually +favoured or selected, until at last a complete separation of the sexes +would be effected. + +Let us now turn to the nectar-feeding insects in our imaginary case: we +may suppose the plant of which we have been slowly increasing the nectar +by continued selection, to be a common plant; and that certain insects +depended in main part on its nectar for food. I could give many facts, +showing how anxious bees are to save time; for instance, their habit of +cutting holes and sucking the nectar at the bases of certain flowers, +which they can, with a very little more trouble, enter by the mouth. +Bearing such facts in mind, I can see no reason to doubt that an +accidental deviation in the size and form of the body, or in the +curvature and length of the proboscis, etc., far too slight to be +appreciated by us, might profit a bee or other insect, so that an +individual so characterised would be able to obtain its food more +quickly, and so have a better chance of living and leaving descendants. +Its descendants would probably inherit a tendency to a similar slight +deviation of structure. The tubes of the corollas of the common red and +incarnate clovers (Trifolium pratense and incarnatum) do not on a hasty +glance appear to differ in length; yet the hive-bee can easily suck the +nectar out of the incarnate clover, but not out of the common red +clover, which is visited by humble-bees alone; so that whole fields of +the red clover offer in vain an abundant supply of precious nectar to +the hive-bee. Thus it might be a great advantage to the hive-bee to have +a slightly longer or differently constructed proboscis. On the other +hand, I have found by experiment that the fertility of clover greatly +depends on bees visiting and moving parts of the corolla, so as to push +the pollen on to the stigmatic surface. Hence, again, if humble-bees +were to become rare in any country, it might be a great advantage to the +red clover to have a shorter or more deeply divided tube to its corolla, +so that the hive-bee could visit its flowers. Thus I can understand how +a flower and a bee might slowly become, either simultaneously or one +after the other, modified and adapted in the most perfect manner to each +other, by the continued preservation of individuals presenting mutual +and slightly favourable deviations of structure. + +I am well aware that this doctrine of natural selection, exemplified in +the above imaginary instances, is open to the same objections which were +at first urged against Sir Charles Lyell’s noble views on “the modern +changes of the earth, as illustrative of geology;” but we now very +seldom hear the action, for instance, of the coast-waves, called a +trifling and insignificant cause, when applied to the excavation of +gigantic valleys or to the formation of the longest lines of inland +cliffs. Natural selection can act only by the preservation and +accumulation of infinitesimally small inherited modifications, each +profitable to the preserved being; and as modern geology has almost +banished such views as the excavation of a great valley by a single +diluvial wave, so will natural selection, if it be a true principle, +banish the belief of the continued creation of new organic beings, or of +any great and sudden modification in their structure. + +On the Intercrossing of Individuals.—I must here introduce a short +digression. In the case of animals and plants with separated sexes, it +is of course obvious that two individuals must always unite for each +birth; but in the case of hermaphrodites this is far from obvious. +Nevertheless I am strongly inclined to believe that with all +hermaphrodites two individuals, either occasionally or habitually, +concur for the reproduction of their kind. This view, I may add, was +first suggested by Andrew Knight. We shall presently see its importance; +but I must here treat the subject with extreme brevity, though I have +the materials prepared for an ample discussion. All vertebrate animals, +all insects, and some other large groups of animals, pair for each +birth. Modern research has much diminished the number of supposed +hermaphrodites, and of real hermaphrodites a large number pair; that is, +two individuals regularly unite for reproduction, which is all that +concerns us. But still there are many hermaphrodite animals which +certainly do not habitually pair, and a vast majority of plants are +hermaphrodites. What reason, it may be asked, is there for supposing in +these cases that two individuals ever concur in reproduction? As it is +impossible here to enter on details, I must trust to some general considerations alone. -In the first place, I have collected so large a body of facts, showing, in -accordance with the almost universal belief of breeders, that with animals and -plants a cross between different varieties, or between individuals of the same -variety but of another strain, gives vigour and fertility to the offspring; and -on the other hand, that close interbreeding diminishes vigour and fertility; -that these facts alone incline me to believe that it is a general law of nature -(utterly ignorant though we be of the meaning of the law) that no organic being -self-fertilises itself for an eternity of generations; but that a cross with -another individual is occasionally—perhaps at very long +In the first place, I have collected so large a body of facts, showing, +in accordance with the almost universal belief of breeders, that with +animals and plants a cross between different varieties, or between +individuals of the same variety but of another strain, gives vigour and +fertility to the offspring; and on the other hand, that close +interbreeding diminishes vigour and fertility; that these facts alone +incline me to believe that it is a general law of nature (utterly +ignorant though we be of the meaning of the law) that no organic being +self-fertilises itself for an eternity of generations; but that a cross +with another individual is occasionally—perhaps at very long intervals—indispensable. -On the belief that this is a law of nature, we can, I think, understand several -large classes of facts, such as the following, which on any other view are -inexplicable. Every hybridizer knows how unfavourable exposure to wet is to the -fertilisation of a flower, yet what a multitude of flowers have their anthers -and stigmas fully exposed to the weather! but if an occasional cross be -indispensable, the fullest freedom for the entrance of pollen from another -individual will explain this state of exposure, more especially as the plant’s -own anthers and pistil generally stand so close together that -self-fertilisation seems almost inevitable. Many flowers, on the other hand, -have their organs of fructification closely enclosed, as in the great -papilionaceous or pea-family; but in several, perhaps in all, such flowers, -there is a very curious adaptation between the structure of the flower and the -manner in which bees suck the nectar; for, in doing this, they either push the -flower’s own pollen on the stigma, or bring pollen from another flower. So -necessary are the visits of bees to papilionaceous flowers, that I have found, -by experiments published elsewhere, that their fertility is greatly diminished -if these visits be prevented. Now, it is scarcely possible that bees should fly -from flower to flower, and not carry pollen from one to the other, to the great -good, as I believe, of the plant. Bees will act like a camel-hair pencil, and -it is quite sufficient just to touch the anthers of one flower and then the -stigma of another with the same brush to ensure fertilisation; but it must not +On the belief that this is a law of nature, we can, I think, understand +several large classes of facts, such as the following, which on any +other view are inexplicable. Every hybridizer knows how unfavourable +exposure to wet is to the fertilisation of a flower, yet what a +multitude of flowers have their anthers and stigmas fully exposed to the +weather! but if an occasional cross be indispensable, the fullest +freedom for the entrance of pollen from another individual will explain +this state of exposure, more especially as the plant’s own anthers and +pistil generally stand so close together that self-fertilisation seems +almost inevitable. Many flowers, on the other hand, have their organs of +fructification closely enclosed, as in the great papilionaceous or +pea-family; but in several, perhaps in all, such flowers, there is a +very curious adaptation between the structure of the flower and the +manner in which bees suck the nectar; for, in doing this, they either +push the flower’s own pollen on the stigma, or bring pollen from another +flower. So necessary are the visits of bees to papilionaceous flowers, +that I have found, by experiments published elsewhere, that their +fertility is greatly diminished if these visits be prevented. Now, it is +scarcely possible that bees should fly from flower to flower, and not +carry pollen from one to the other, to the great good, as I believe, of +the plant. Bees will act like a camel-hair pencil, and it is quite +sufficient just to touch the anthers of one flower and then the stigma +of another with the same brush to ensure fertilisation; but it must not be supposed that bees would thus produce a multitude of hybrids between -distinct species; for if you bring on the same brush a plant’s own pollen and -pollen from another species, the former will have such a prepotent effect, that -it will invariably and completely destroy, as has been shown by Gärtner, any -influence from the foreign pollen. - -When the stamens of a flower suddenly spring towards the pistil, or slowly move -one after the other towards it, the contrivance seems adapted solely to ensure -self-fertilisation; and no doubt it is useful for this end: but, the agency of -insects is often required to cause the stamens to spring forward, as Kölreuter -has shown to be the case with the barberry; and curiously in this very genus, -which seems to have a special contrivance for self-fertilisation, it is well -known that if very closely-allied forms or varieties are planted near each -other, it is hardly possible to raise pure seedlings, so largely do they -naturally cross. In many other cases, far from there being any aids for -self-fertilisation, there are special contrivances, as I could show from the -writings of C. C. Sprengel and from my own observations, which effectually -prevent the stigma receiving pollen from its own flower: for instance, in -Lobelia fulgens, there is a really beautiful and elaborate contrivance by which -every one of the infinitely numerous pollen-granules are swept out of the -conjoined anthers of each flower, before the stigma of that individual flower -is ready to receive them; and as this flower is never visited, at least in my -garden, by insects, it never sets a seed, though by placing pollen from one -flower on the stigma of another, I raised plenty of seedlings; and whilst -another species of Lobelia growing close by, which is visited by bees, seeds +distinct species; for if you bring on the same brush a plant’s own +pollen and pollen from another species, the former will have such a +prepotent effect, that it will invariably and completely destroy, as has +been shown by Gärtner, any influence from the foreign pollen. + +When the stamens of a flower suddenly spring towards the pistil, or +slowly move one after the other towards it, the contrivance seems +adapted solely to ensure self-fertilisation; and no doubt it is useful +for this end: but, the agency of insects is often required to cause the +stamens to spring forward, as Kölreuter has shown to be the case with +the barberry; and curiously in this very genus, which seems to have a +special contrivance for self-fertilisation, it is well known that if +very closely-allied forms or varieties are planted near each other, it +is hardly possible to raise pure seedlings, so largely do they naturally +cross. In many other cases, far from there being any aids for +self-fertilisation, there are special contrivances, as I could show from +the writings of C. C. Sprengel and from my own observations, which +effectually prevent the stigma receiving pollen from its own flower: for +instance, in Lobelia fulgens, there is a really beautiful and elaborate +contrivance by which every one of the infinitely numerous +pollen-granules are swept out of the conjoined anthers of each flower, +before the stigma of that individual flower is ready to receive them; +and as this flower is never visited, at least in my garden, by insects, +it never sets a seed, though by placing pollen from one flower on the +stigma of another, I raised plenty of seedlings; and whilst another +species of Lobelia growing close by, which is visited by bees, seeds freely. In very many other cases, though there be no special mechanical -contrivance to prevent the stigma of a flower receiving its own pollen, yet, as -C. C. Sprengel has shown, and as I can confirm, either the anthers burst before -the stigma is ready for fertilisation, or the stigma is ready before the pollen -of that flower is ready, so that these plants have in fact separated sexes, and -must habitually be crossed. How strange are these facts! How strange that the -pollen and stigmatic surface of the same flower, though placed so close -together, as if for the very purpose of self-fertilisation, should in so many -cases be mutually useless to each other! How simply are these facts explained -on the view of an occasional cross with a distinct individual being +contrivance to prevent the stigma of a flower receiving its own pollen, +yet, as C. C. Sprengel has shown, and as I can confirm, either the +anthers burst before the stigma is ready for fertilisation, or the +stigma is ready before the pollen of that flower is ready, so that these +plants have in fact separated sexes, and must habitually be crossed. How +strange are these facts! How strange that the pollen and stigmatic +surface of the same flower, though placed so close together, as if for +the very purpose of self-fertilisation, should in so many cases be +mutually useless to each other! How simply are these facts explained on +the view of an occasional cross with a distinct individual being advantageous or indispensable! -If several varieties of the cabbage, radish, onion, and of some other plants, -be allowed to seed near each other, a large majority, as I have found, of the -seedlings thus raised will turn out mongrels: for instance, I raised 233 -seedling cabbages from some plants of different varieties growing near each -other, and of these only 78 were true to their kind, and some even of these -were not perfectly true. Yet the pistil of each cabbage-flower is surrounded -not only by its own six stamens, but by those of the many other flowers on the -same plant. How, then, comes it that such a vast number of the seedlings are -mongrelized? I suspect that it must arise from the pollen of a distinct variety -having a prepotent effect over a flower’s own pollen; and that this is part of -the general law of good being derived from the intercrossing of distinct -individuals of the same species. When distinct species are crossed the case is -directly the reverse, for a plant’s own pollen is always prepotent over foreign -pollen; but to this subject we shall return in a future chapter. - -In the case of a gigantic tree covered with innumerable flowers, it may be -objected that pollen could seldom be carried from tree to tree, and at most -only from flower to flower on the same tree, and that flowers on the same tree -can be considered as distinct individuals only in a limited sense. I believe -this objection to be valid, but that nature has largely provided against it by -giving to trees a strong tendency to bear flowers with separated sexes. When -the sexes are separated, although the male and female flowers may be produced -on the same tree, we can see that pollen must be regularly carried from flower -to flower; and this will give a better chance of pollen being occasionally -carried from tree to tree. That trees belonging to all Orders have their sexes -more often separated than other plants, I find to be the case in this country; -and at my request Dr. Hooker tabulated the trees of New Zealand, and Dr. Asa -Gray those of the United States, and the result was as I anticipated. On the -other hand, Dr. Hooker has recently informed me that he finds that the rule -does not hold in Australia; and I have made these few remarks on the sexes of -trees simply to call attention to the subject. +If several varieties of the cabbage, radish, onion, and of some other +plants, be allowed to seed near each other, a large majority, as I have +found, of the seedlings thus raised will turn out mongrels: for +instance, I raised 233 seedling cabbages from some plants of different +varieties growing near each other, and of these only 78 were true to +their kind, and some even of these were not perfectly true. Yet the +pistil of each cabbage-flower is surrounded not only by its own six +stamens, but by those of the many other flowers on the same plant. How, +then, comes it that such a vast number of the seedlings are mongrelized? +I suspect that it must arise from the pollen of a distinct variety +having a prepotent effect over a flower’s own pollen; and that this is +part of the general law of good being derived from the intercrossing of +distinct individuals of the same species. When distinct species are +crossed the case is directly the reverse, for a plant’s own pollen is +always prepotent over foreign pollen; but to this subject we shall +return in a future chapter. + +In the case of a gigantic tree covered with innumerable flowers, it may +be objected that pollen could seldom be carried from tree to tree, and +at most only from flower to flower on the same tree, and that flowers on +the same tree can be considered as distinct individuals only in a +limited sense. I believe this objection to be valid, but that nature has +largely provided against it by giving to trees a strong tendency to bear +flowers with separated sexes. When the sexes are separated, although the +male and female flowers may be produced on the same tree, we can see +that pollen must be regularly carried from flower to flower; and this +will give a better chance of pollen being occasionally carried from tree +to tree. That trees belonging to all Orders have their sexes more often +separated than other plants, I find to be the case in this country; and +at my request Dr. Hooker tabulated the trees of New Zealand, and Dr. Asa +Gray those of the United States, and the result was as I anticipated. On +the other hand, Dr. Hooker has recently informed me that he finds that +the rule does not hold in Australia; and I have made these few remarks +on the sexes of trees simply to call attention to the subject. Turning for a very brief space to animals: on the land there are some -hermaphrodites, as land-mollusca and earth-worms; but these all pair. As yet I -have not found a single case of a terrestrial animal which fertilises itself. -We can understand this remarkable fact, which offers so strong a contrast with -terrestrial plants, on the view of an occasional cross being indispensable, by -considering the medium in which terrestrial animals live, and the nature of the -fertilising element; for we know of no means, analogous to the action of -insects and of the wind in the case of plants, by which an occasional cross -could be effected with terrestrial animals without the concurrence of two -individuals. Of aquatic animals, there are many self-fertilising -hermaphrodites; but here currents in the water offer an obvious means for an -occasional cross. And, as in the case of flowers, I have as yet failed, after -consultation with one of the highest authorities, namely, Professor Huxley, to -discover a single case of an hermaphrodite animal with the organs of -reproduction so perfectly enclosed within the body, that access from without -and the occasional influence of a distinct individual can be shown to be -physically impossible. Cirripedes long appeared to me to present a case of very -great difficulty under this point of view; but I have been enabled, by a -fortunate chance, elsewhere to prove that two individuals, though both are -self-fertilising hermaphrodites, do sometimes cross. - -It must have struck most naturalists as a strange anomaly that, in the case of -both animals and plants, species of the same family and even of the same genus, -though agreeing closely with each other in almost their whole organisation, yet -are not rarely, some of them hermaphrodites, and some of them unisexual. But -if, in fact, all hermaphrodites do occasionally intercross with other -individuals, the difference between hermaphrodites and unisexual species, as -far as function is concerned, becomes very small. - -From these several considerations and from the many special facts which I have -collected, but which I am not here able to give, I am strongly inclined to -suspect that, both in the vegetable and animal kingdoms, an occasional -intercross with a distinct individual is a law of nature. I am well aware that -there are, on this view, many cases of difficulty, some of which I am trying to -investigate. Finally then, we may conclude that in many organic beings, a cross -between two individuals is an obvious necessity for each birth; in many others -it occurs perhaps only at long intervals; but in none, as I suspect, can -self-fertilisation go on for perpetuity. - -Circumstances favourable to Natural Selection.—This is an extremely intricate -subject. A large amount of inheritable and diversified variability is -favourable, but I believe mere individual differences suffice for the work. A -large number of individuals, by giving a better chance for the appearance -within any given period of profitable variations, will compensate for a lesser -amount of variability in each individual, and is, I believe, an extremely -important element of success. Though nature grants vast periods of time for the -work of natural selection, she does not grant an indefinite period; for as all -organic beings are striving, it may be said, to seize on each place in the -economy of nature, if any one species does not become modified and improved in -a corresponding degree with its competitors, it will soon be exterminated. - -In man’s methodical selection, a breeder selects for some definite object, and -free intercrossing will wholly stop his work. But when many men, without -intending to alter the breed, have a nearly common standard of perfection, and -all try to get and breed from the best animals, much improvement and -modification surely but slowly follow from this unconscious process of -selection, notwithstanding a large amount of crossing with inferior animals. -Thus it will be in nature; for within a confined area, with some place in its -polity not so perfectly occupied as might be, natural selection will always -tend to preserve all the individuals varying in the right direction, though in -different degrees, so as better to fill up the unoccupied place. But if the -area be large, its several districts will almost certainly present different -conditions of life; and then if natural selection be modifying and improving a -species in the several districts, there will be intercrossing with the other -individuals of the same species on the confines of each. And in this case the -effects of intercrossing can hardly be counterbalanced by natural selection -always tending to modify all the individuals in each district in exactly the -same manner to the conditions of each; for in a continuous area, the conditions -will generally graduate away insensibly from one district to another. The -intercrossing will most affect those animals which unite for each birth, which -wander much, and which do not breed at a very quick rate. Hence in animals of -this nature, for instance in birds, varieties will generally be confined to -separated countries; and this I believe to be the case. In hermaphrodite -organisms which cross only occasionally, and likewise in animals which unite -for each birth, but which wander little and which can increase at a very rapid -rate, a new and improved variety might be quickly formed on any one spot, and -might there maintain itself in a body, so that whatever intercrossing took -place would be chiefly between the individuals of the same new variety. A local -variety when once thus formed might subsequently slowly spread to other -districts. On the above principle, nurserymen always prefer getting seed from a -large body of plants of the same variety, as the chance of intercrossing with -other varieties is thus lessened. - -Even in the case of slow-breeding animals, which unite for each birth, we must -not overrate the effects of intercrosses in retarding natural selection; for I -can bring a considerable catalogue of facts, showing that within the same area, -varieties of the same animal can long remain distinct, from haunting different -stations, from breeding at slightly different seasons, or from varieties of the -same kind preferring to pair together. - -Intercrossing plays a very important part in nature in keeping the individuals -of the same species, or of the same variety, true and uniform in character. It -will obviously thus act far more efficiently with those animals which unite for -each birth; but I have already attempted to show that we have reason to believe -that occasional intercrosses take place with all animals and with all plants. -Even if these take place only at long intervals, I am convinced that the young -thus produced will gain so much in vigour and fertility over the offspring from -long-continued self-fertilisation, that they will have a better chance of -surviving and propagating their kind; and thus, in the long run, the influence -of intercrosses, even at rare intervals, will be great. If there exist organic -beings which never intercross, uniformity of character can be retained amongst -them, as long as their conditions of life remain the same, only through the -principle of inheritance, and through natural selection destroying any which -depart from the proper type; but if their conditions of life change and they -undergo modification, uniformity of character can be given to their modified +hermaphrodites, as land-mollusca and earth-worms; but these all pair. As +yet I have not found a single case of a terrestrial animal which +fertilises itself. We can understand this remarkable fact, which offers +so strong a contrast with terrestrial plants, on the view of an +occasional cross being indispensable, by considering the medium in which +terrestrial animals live, and the nature of the fertilising element; for +we know of no means, analogous to the action of insects and of the wind +in the case of plants, by which an occasional cross could be effected +with terrestrial animals without the concurrence of two individuals. Of +aquatic animals, there are many self-fertilising hermaphrodites; but +here currents in the water offer an obvious means for an occasional +cross. And, as in the case of flowers, I have as yet failed, after +consultation with one of the highest authorities, namely, Professor +Huxley, to discover a single case of an hermaphrodite animal with the +organs of reproduction so perfectly enclosed within the body, that +access from without and the occasional influence of a distinct +individual can be shown to be physically impossible. Cirripedes long +appeared to me to present a case of very great difficulty under this +point of view; but I have been enabled, by a fortunate chance, elsewhere +to prove that two individuals, though both are self-fertilising +hermaphrodites, do sometimes cross. + +It must have struck most naturalists as a strange anomaly that, in the +case of both animals and plants, species of the same family and even of +the same genus, though agreeing closely with each other in almost their +whole organisation, yet are not rarely, some of them hermaphrodites, and +some of them unisexual. But if, in fact, all hermaphrodites do +occasionally intercross with other individuals, the difference between +hermaphrodites and unisexual species, as far as function is concerned, +becomes very small. + +From these several considerations and from the many special facts which +I have collected, but which I am not here able to give, I am strongly +inclined to suspect that, both in the vegetable and animal kingdoms, an +occasional intercross with a distinct individual is a law of nature. I +am well aware that there are, on this view, many cases of difficulty, +some of which I am trying to investigate. Finally then, we may conclude +that in many organic beings, a cross between two individuals is an +obvious necessity for each birth; in many others it occurs perhaps only +at long intervals; but in none, as I suspect, can self-fertilisation go +on for perpetuity. + +Circumstances favourable to Natural Selection.—This is an extremely +intricate subject. A large amount of inheritable and diversified +variability is favourable, but I believe mere individual differences +suffice for the work. A large number of individuals, by giving a better +chance for the appearance within any given period of profitable +variations, will compensate for a lesser amount of variability in each +individual, and is, I believe, an extremely important element of +success. Though nature grants vast periods of time for the work of +natural selection, she does not grant an indefinite period; for as all +organic beings are striving, it may be said, to seize on each place in +the economy of nature, if any one species does not become modified and +improved in a corresponding degree with its competitors, it will soon be +exterminated. + +In man’s methodical selection, a breeder selects for some definite +object, and free intercrossing will wholly stop his work. But when many +men, without intending to alter the breed, have a nearly common standard +of perfection, and all try to get and breed from the best animals, much +improvement and modification surely but slowly follow from this +unconscious process of selection, notwithstanding a large amount of +crossing with inferior animals. Thus it will be in nature; for within a +confined area, with some place in its polity not so perfectly occupied +as might be, natural selection will always tend to preserve all the +individuals varying in the right direction, though in different degrees, +so as better to fill up the unoccupied place. But if the area be large, +its several districts will almost certainly present different conditions +of life; and then if natural selection be modifying and improving a +species in the several districts, there will be intercrossing with the +other individuals of the same species on the confines of each. And in +this case the effects of intercrossing can hardly be counterbalanced by +natural selection always tending to modify all the individuals in each +district in exactly the same manner to the conditions of each; for in a +continuous area, the conditions will generally graduate away insensibly +from one district to another. The intercrossing will most affect those +animals which unite for each birth, which wander much, and which do not +breed at a very quick rate. Hence in animals of this nature, for +instance in birds, varieties will generally be confined to separated +countries; and this I believe to be the case. In hermaphrodite organisms +which cross only occasionally, and likewise in animals which unite for +each birth, but which wander little and which can increase at a very +rapid rate, a new and improved variety might be quickly formed on any +one spot, and might there maintain itself in a body, so that whatever +intercrossing took place would be chiefly between the individuals of the +same new variety. A local variety when once thus formed might +subsequently slowly spread to other districts. On the above principle, +nurserymen always prefer getting seed from a large body of plants of the +same variety, as the chance of intercrossing with other varieties is +thus lessened. + +Even in the case of slow-breeding animals, which unite for each birth, +we must not overrate the effects of intercrosses in retarding natural +selection; for I can bring a considerable catalogue of facts, showing +that within the same area, varieties of the same animal can long remain +distinct, from haunting different stations, from breeding at slightly +different seasons, or from varieties of the same kind preferring to pair +together. + +Intercrossing plays a very important part in nature in keeping the +individuals of the same species, or of the same variety, true and +uniform in character. It will obviously thus act far more efficiently +with those animals which unite for each birth; but I have already +attempted to show that we have reason to believe that occasional +intercrosses take place with all animals and with all plants. Even if +these take place only at long intervals, I am convinced that the young +thus produced will gain so much in vigour and fertility over the +offspring from long-continued self-fertilisation, that they will have a +better chance of surviving and propagating their kind; and thus, in the +long run, the influence of intercrosses, even at rare intervals, will be +great. If there exist organic beings which never intercross, uniformity +of character can be retained amongst them, as long as their conditions +of life remain the same, only through the principle of inheritance, and +through natural selection destroying any which depart from the proper +type; but if their conditions of life change and they undergo +modification, uniformity of character can be given to their modified offspring, solely by natural selection preserving the same favourable variations. -Isolation, also, is an important element in the process of natural selection. -In a confined or isolated area, if not very large, the organic and inorganic -conditions of life will generally be in a great degree uniform; so that natural -selection will tend to modify all the individuals of a varying species -throughout the area in the same manner in relation to the same conditions. -Intercrosses, also, with the individuals of the same species, which otherwise -would have inhabited the surrounding and differently circumstanced districts, -will be prevented. But isolation probably acts more efficiently in checking the -immigration of better adapted organisms, after any physical change, such as of -climate or elevation of the land, etc.; and thus new places in the natural -economy of the country are left open for the old inhabitants to struggle for, -and become adapted to, through modifications in their structure and -constitution. Lastly, isolation, by checking immigration and consequently -competition, will give time for any new variety to be slowly improved; and this -may sometimes be of importance in the production of new species. If, however, -an isolated area be very small, either from being surrounded by barriers, or -from having very peculiar physical conditions, the total number of the -individuals supported on it will necessarily be very small; and fewness of -individuals will greatly retard the production of new species through natural -selection, by decreasing the chance of the appearance of favourable variations. - -If we turn to nature to test the truth of these remarks, and look at any small -isolated area, such as an oceanic island, although the total number of the -species inhabiting it, will be found to be small, as we shall see in our -chapter on geographical distribution; yet of these species a very large -proportion are endemic,—that is, have been produced there, and nowhere else. -Hence an oceanic island at first sight seems to have been highly favourable for -the production of new species. But we may thus greatly deceive ourselves, for -to ascertain whether a small isolated area, or a large open area like a -continent, has been most favourable for the production of new organic forms, we -ought to make the comparison within equal times; and this we are incapable of -doing. - -Although I do not doubt that isolation is of considerable importance in the -production of new species, on the whole I am inclined to believe that largeness -of area is of more importance, more especially in the production of species, -which will prove capable of enduring for a long period, and of spreading -widely. Throughout a great and open area, not only will there be a better -chance of favourable variations arising from the large number of individuals of -the same species there supported, but the conditions of life are infinitely -complex from the large number of already existing species; and if some of these -many species become modified and improved, others will have to be improved in a -corresponding degree or they will be exterminated. Each new form, also, as soon -as it has been much improved, will be able to spread over the open and -continuous area, and will thus come into competition with many others. Hence -more new places will be formed, and the competition to fill them will be more -severe, on a large than on a small and isolated area. Moreover, great areas, -though now continuous, owing to oscillations of level, will often have recently -existed in a broken condition, so that the good effects of isolation will -generally, to a certain extent, have concurred. Finally, I conclude that, -although small isolated areas probably have been in some respects highly -favourable for the production of new species, yet that the course of -modification will generally have been more rapid on large areas; and what is -more important, that the new forms produced on large areas, which already have -been victorious over many competitors, will be those that will spread most -widely, will give rise to most new varieties and species, and will thus play an -important part in the changing history of the organic world. - -We can, perhaps, on these views, understand some facts which will be again -alluded to in our chapter on geographical distribution; for instance, that the -productions of the smaller continent of Australia have formerly yielded, and -apparently are now yielding, before those of the larger Europæo-Asiatic area. -Thus, also, it is that continental productions have everywhere become so -largely naturalised on islands. On a small island, the race for life will have -been less severe, and there will have been less modification and less -extermination. Hence, perhaps, it comes that the flora of Madeira, according to -Oswald Heer, resembles the extinct tertiary flora of Europe. All fresh-water -basins, taken together, make a small area compared with that of the sea or of -the land; and, consequently, the competition between fresh-water productions -will have been less severe than elsewhere; new forms will have been more slowly -formed, and old forms more slowly exterminated. And it is in fresh water that -we find seven genera of Ganoid fishes, remnants of a once preponderant order: -and in fresh water we find some of the most anomalous forms now known in the -world, as the Ornithorhynchus and Lepidosiren, which, like fossils, connect to -a certain extent orders now widely separated in the natural scale. These -anomalous forms may almost be called living fossils; they have endured to the -present day, from having inhabited a confined area, and from having thus been -exposed to less severe competition. - -To sum up the circumstances favourable and unfavourable to natural selection, -as far as the extreme intricacy of the subject permits. I conclude, looking to -the future, that for terrestrial productions a large continental area, which -will probably undergo many oscillations of level, and which consequently will -exist for long periods in a broken condition, will be the most favourable for -the production of many new forms of life, likely to endure long and to spread -widely. For the area will first have existed as a continent, and the -inhabitants, at this period numerous in individuals and kinds, will have been -subjected to very severe competition. When converted by subsidence into large -separate islands, there will still exist many individuals of the same species -on each island: intercrossing on the confines of the range of each species will -thus be checked: after physical changes of any kind, immigration will be -prevented, so that new places in the polity of each island will have to be -filled up by modifications of the old inhabitants; and time will be allowed for -the varieties in each to become well modified and perfected. When, by renewed -elevation, the islands shall be re-converted into a continental area, there -will again be severe competition: the most favoured or improved varieties will -be enabled to spread: there will be much extinction of the less improved forms, -and the relative proportional numbers of the various inhabitants of the renewed -continent will again be changed; and again there will be a fair field for -natural selection to improve still further the inhabitants, and thus produce -new species. - -That natural selection will always act with extreme slowness, I fully admit. -Its action depends on there being places in the polity of nature, which can be -better occupied by some of the inhabitants of the country undergoing -modification of some kind. The existence of such places will often depend on -physical changes, which are generally very slow, and on the immigration of -better adapted forms having been checked. But the action of natural selection -will probably still oftener depend on some of the inhabitants becoming slowly -modified; the mutual relations of many of the other inhabitants being thus -disturbed. Nothing can be effected, unless favourable variations occur, and -variation itself is apparently always a very slow process. The process will -often be greatly retarded by free intercrossing. Many will exclaim that these +Isolation, also, is an important element in the process of natural +selection. In a confined or isolated area, if not very large, the +organic and inorganic conditions of life will generally be in a great +degree uniform; so that natural selection will tend to modify all the +individuals of a varying species throughout the area in the same manner +in relation to the same conditions. Intercrosses, also, with the +individuals of the same species, which otherwise would have inhabited +the surrounding and differently circumstanced districts, will be +prevented. But isolation probably acts more efficiently in checking the +immigration of better adapted organisms, after any physical change, such +as of climate or elevation of the land, etc.; and thus new places in the +natural economy of the country are left open for the old inhabitants to +struggle for, and become adapted to, through modifications in their +structure and constitution. Lastly, isolation, by checking immigration +and consequently competition, will give time for any new variety to be +slowly improved; and this may sometimes be of importance in the +production of new species. If, however, an isolated area be very small, +either from being surrounded by barriers, or from having very peculiar +physical conditions, the total number of the individuals supported on it +will necessarily be very small; and fewness of individuals will greatly +retard the production of new species through natural selection, by +decreasing the chance of the appearance of favourable variations. + +If we turn to nature to test the truth of these remarks, and look at any +small isolated area, such as an oceanic island, although the total +number of the species inhabiting it, will be found to be small, as we +shall see in our chapter on geographical distribution; yet of these +species a very large proportion are endemic,—that is, have been produced +there, and nowhere else. Hence an oceanic island at first sight seems +to have been highly favourable for the production of new species. But we +may thus greatly deceive ourselves, for to ascertain whether a small +isolated area, or a large open area like a continent, has been most +favourable for the production of new organic forms, we ought to make the +comparison within equal times; and this we are incapable of doing. + +Although I do not doubt that isolation is of considerable importance in +the production of new species, on the whole I am inclined to believe +that largeness of area is of more importance, more especially in the +production of species, which will prove capable of enduring for a long +period, and of spreading widely. Throughout a great and open area, not +only will there be a better chance of favourable variations arising from +the large number of individuals of the same species there supported, but +the conditions of life are infinitely complex from the large number of +already existing species; and if some of these many species become +modified and improved, others will have to be improved in a +corresponding degree or they will be exterminated. Each new form, also, +as soon as it has been much improved, will be able to spread over the +open and continuous area, and will thus come into competition with many +others. Hence more new places will be formed, and the competition to +fill them will be more severe, on a large than on a small and isolated +area. Moreover, great areas, though now continuous, owing to +oscillations of level, will often have recently existed in a broken +condition, so that the good effects of isolation will generally, to a +certain extent, have concurred. Finally, I conclude that, although small +isolated areas probably have been in some respects highly favourable for +the production of new species, yet that the course of modification will +generally have been more rapid on large areas; and what is more +important, that the new forms produced on large areas, which already +have been victorious over many competitors, will be those that will +spread most widely, will give rise to most new varieties and species, +and will thus play an important part in the changing history of the +organic world. + +We can, perhaps, on these views, understand some facts which will be +again alluded to in our chapter on geographical distribution; for +instance, that the productions of the smaller continent of Australia +have formerly yielded, and apparently are now yielding, before those of +the larger Europæo-Asiatic area. Thus, also, it is that continental +productions have everywhere become so largely naturalised on islands. On +a small island, the race for life will have been less severe, and there +will have been less modification and less extermination. Hence, perhaps, +it comes that the flora of Madeira, according to Oswald Heer, resembles +the extinct tertiary flora of Europe. All fresh-water basins, taken +together, make a small area compared with that of the sea or of the +land; and, consequently, the competition between fresh-water productions +will have been less severe than elsewhere; new forms will have been more +slowly formed, and old forms more slowly exterminated. And it is in +fresh water that we find seven genera of Ganoid fishes, remnants of a +once preponderant order: and in fresh water we find some of the most +anomalous forms now known in the world, as the Ornithorhynchus and +Lepidosiren, which, like fossils, connect to a certain extent orders now +widely separated in the natural scale. These anomalous forms may almost +be called living fossils; they have endured to the present day, from +having inhabited a confined area, and from having thus been exposed to +less severe competition. + +To sum up the circumstances favourable and unfavourable to natural +selection, as far as the extreme intricacy of the subject permits. I +conclude, looking to the future, that for terrestrial productions a +large continental area, which will probably undergo many oscillations of +level, and which consequently will exist for long periods in a broken +condition, will be the most favourable for the production of many new +forms of life, likely to endure long and to spread widely. For the area +will first have existed as a continent, and the inhabitants, at this +period numerous in individuals and kinds, will have been subjected to +very severe competition. When converted by subsidence into large +separate islands, there will still exist many individuals of the same +species on each island: intercrossing on the confines of the range of +each species will thus be checked: after physical changes of any kind, +immigration will be prevented, so that new places in the polity of each +island will have to be filled up by modifications of the old +inhabitants; and time will be allowed for the varieties in each to +become well modified and perfected. When, by renewed elevation, the +islands shall be re-converted into a continental area, there will again +be severe competition: the most favoured or improved varieties will be +enabled to spread: there will be much extinction of the less improved +forms, and the relative proportional numbers of the various inhabitants +of the renewed continent will again be changed; and again there will be +a fair field for natural selection to improve still further the +inhabitants, and thus produce new species. + +That natural selection will always act with extreme slowness, I fully +admit. Its action depends on there being places in the polity of +nature, which can be better occupied by some of the inhabitants of the +country undergoing modification of some kind. The existence of such +places will often depend on physical changes, which are generally very +slow, and on the immigration of better adapted forms having been +checked. But the action of natural selection will probably still oftener +depend on some of the inhabitants becoming slowly modified; the mutual +relations of many of the other inhabitants being thus disturbed. Nothing +can be effected, unless favourable variations occur, and variation +itself is apparently always a very slow process. The process will often +be greatly retarded by free intercrossing. Many will exclaim that these several causes are amply sufficient wholly to stop the action of natural -selection. I do not believe so. On the other hand, I do believe that natural -selection will always act very slowly, often only at long intervals of time, -and generally on only a very few of the inhabitants of the same region at the -same time. I further believe, that this very slow, intermittent action of -natural selection accords perfectly well with what geology tells us of the rate -and manner at which the inhabitants of this world have changed. - -Slow though the process of selection may be, if feeble man can do much by his -powers of artificial selection, I can see no limit to the amount of change, to -the beauty and infinite complexity of the coadaptations between all organic -beings, one with another and with their physical conditions of life, which may -be effected in the long course of time by nature’s power of selection. +selection. I do not believe so. On the other hand, I do believe that +natural selection will always act very slowly, often only at long +intervals of time, and generally on only a very few of the inhabitants +of the same region at the same time. I further believe, that this very +slow, intermittent action of natural selection accords perfectly well +with what geology tells us of the rate and manner at which the +inhabitants of this world have changed. + +Slow though the process of selection may be, if feeble man can do much +by his powers of artificial selection, I can see no limit to the amount +of change, to the beauty and infinite complexity of the coadaptations +between all organic beings, one with another and with their physical +conditions of life, which may be effected in the long course of time by +nature’s power of selection. Extinction.—This subject will be more fully discussed in our chapter on -Geology; but it must be here alluded to from being intimately connected with -natural selection. Natural selection acts solely through the preservation of -variations in some way advantageous, which consequently endure. But as from the -high geometrical powers of increase of all organic beings, each area is already -fully stocked with inhabitants, it follows that as each selected and favoured -form increases in number, so will the less favoured forms decrease and become -rare. Rarity, as geology tells us, is the precursor to extinction. We can, -also, see that any form represented by few individuals will, during -fluctuations in the seasons or in the number of its enemies, run a good chance -of utter extinction. But we may go further than this; for as new forms are -continually and slowly being produced, unless we believe that the number of -specific forms goes on perpetually and almost indefinitely increasing, numbers -inevitably must become extinct. That the number of specific forms has not -indefinitely increased, geology shows us plainly; and indeed we can see reason -why they should not have thus increased, for the number of places in the polity -of nature is not indefinitely great,—not that we have any means of knowing that -any one region has as yet got its maximum of species. Probably no region is as -yet fully stocked, for at the Cape of Good Hope, where more species of plants -are crowded together than in any other quarter of the world, some foreign +Geology; but it must be here alluded to from being intimately connected +with natural selection. Natural selection acts solely through the +preservation of variations in some way advantageous, which consequently +endure. But as from the high geometrical powers of increase of all +organic beings, each area is already fully stocked with inhabitants, it +follows that as each selected and favoured form increases in number, so +will the less favoured forms decrease and become rare. Rarity, as +geology tells us, is the precursor to extinction. We can, also, see that +any form represented by few individuals will, during fluctuations in the +seasons or in the number of its enemies, run a good chance of utter +extinction. But we may go further than this; for as new forms are +continually and slowly being produced, unless we believe that the number +of specific forms goes on perpetually and almost indefinitely +increasing, numbers inevitably must become extinct. That the number of +specific forms has not indefinitely increased, geology shows us plainly; +and indeed we can see reason why they should not have thus increased, +for the number of places in the polity of nature is not indefinitely +great,—not that we have any means of knowing that any one region has as +yet got its maximum of species. Probably no region is as yet fully +stocked, for at the Cape of Good Hope, where more species of plants are +crowded together than in any other quarter of the world, some foreign plants have become naturalised, without causing, as far as we know, the extinction of any natives. -Furthermore, the species which are most numerous in individuals will have the -best chance of producing within any given period favourable variations. We have -evidence of this, in the facts given in the second chapter, showing that it is -the common species which afford the greatest number of recorded varieties, or -incipient species. Hence, rare species will be less quickly modified or -improved within any given period, and they will consequently be beaten in the -race for life by the modified descendants of the commoner species. - -From these several considerations I think it inevitably follows, that as new -species in the course of time are formed through natural selection, others will -become rarer and rarer, and finally extinct. The forms which stand in closest -competition with those undergoing modification and improvement, will naturally -suffer most. And we have seen in the chapter on the Struggle for Existence that -it is the most closely-allied forms,—varieties of the same species, and species -of the same genus or of related genera,—which, from having nearly the same -structure, constitution, and habits, generally come into the severest -competition with each other. Consequently, each new variety or species, during -the progress of its formation, will generally press hardest on its nearest -kindred, and tend to exterminate them. We see the same process of extermination -amongst our domesticated productions, through the selection of improved forms -by man. Many curious instances could be given showing how quickly new breeds of -cattle, sheep, and other animals, and varieties of flowers, take the place of -older and inferior kinds. In Yorkshire, it is historically known that the -ancient black cattle were displaced by the long-horns, and that these “were -swept away by the short-horns” (I quote the words of an agricultural writer) -“as if by some murderous pestilence.” - -Divergence of Character.—The principle, which I have designated by this term, -is of high importance on my theory, and explains, as I believe, several -important facts. In the first place, varieties, even strongly-marked ones, -though having somewhat of the character of species—as is shown by the hopeless -doubts in many cases how to rank them—yet certainly differ from each other far -less than do good and distinct species. Nevertheless, according to my view, -varieties are species in the process of formation, or are, as I have called -them, incipient species. How, then, does the lesser difference between -varieties become augmented into the greater difference between species? That -this does habitually happen, we must infer from most of the innumerable species -throughout nature presenting well-marked differences; whereas varieties, the -supposed prototypes and parents of future well-marked species, present slight -and ill-defined differences. Mere chance, as we may call it, might cause one -variety to differ in some character from its parents, and the offspring of this -variety again to differ from its parent in the very same character and in a -greater degree; but this alone would never account for so habitual and large an -amount of difference as that between varieties of the same species and species -of the same genus. +Furthermore, the species which are most numerous in individuals will +have the best chance of producing within any given period favourable +variations. We have evidence of this, in the facts given in the second +chapter, showing that it is the common species which afford the greatest +number of recorded varieties, or incipient species. Hence, rare species +will be less quickly modified or improved within any given period, and +they will consequently be beaten in the race for life by the modified +descendants of the commoner species. + +From these several considerations I think it inevitably follows, that as +new species in the course of time are formed through natural selection, +others will become rarer and rarer, and finally extinct. The forms which +stand in closest competition with those undergoing modification and +improvement, will naturally suffer most. And we have seen in the chapter +on the Struggle for Existence that it is the most closely-allied +forms,—varieties of the same species, and species of the same genus or +of related genera,—which, from having nearly the same structure, +constitution, and habits, generally come into the severest competition +with each other. Consequently, each new variety or species, during the +progress of its formation, will generally press hardest on its nearest +kindred, and tend to exterminate them. We see the same process of +extermination amongst our domesticated productions, through the +selection of improved forms by man. Many curious instances could be +given showing how quickly new breeds of cattle, sheep, and other +animals, and varieties of flowers, take the place of older and inferior +kinds. In Yorkshire, it is historically known that the ancient black +cattle were displaced by the long-horns, and that these “were swept away +by the short-horns” (I quote the words of an agricultural writer) “as if +by some murderous pestilence.” + +Divergence of Character.—The principle, which I have designated by this +term, is of high importance on my theory, and explains, as I believe, +several important facts. In the first place, varieties, even +strongly-marked ones, though having somewhat of the character of +species—as is shown by the hopeless doubts in many cases how to rank +them—yet certainly differ from each other far less than do good and +distinct species. Nevertheless, according to my view, varieties are +species in the process of formation, or are, as I have called them, +incipient species. How, then, does the lesser difference between +varieties become augmented into the greater difference between species? +That this does habitually happen, we must infer from most of the +innumerable species throughout nature presenting well-marked +differences; whereas varieties, the supposed prototypes and parents of +future well-marked species, present slight and ill-defined differences. +Mere chance, as we may call it, might cause one variety to differ in +some character from its parents, and the offspring of this variety again +to differ from its parent in the very same character and in a greater +degree; but this alone would never account for so habitual and large an +amount of difference as that between varieties of the same species and +species of the same genus. As has always been my practice, let us seek light on this head from our -domestic productions. We shall here find something analogous. A fancier is -struck by a pigeon having a slightly shorter beak; another fancier is struck by -a pigeon having a rather longer beak; and on the acknowledged principle that -“fanciers do not and will not admire a medium standard, but like extremes,” -they both go on (as has actually occurred with tumbler-pigeons) choosing and -breeding from birds with longer and longer beaks, or with shorter and shorter -beaks. Again, we may suppose that at an early period one man preferred swifter -horses; another stronger and more bulky horses. The early differences would be -very slight; in the course of time, from the continued selection of swifter -horses by some breeders, and of stronger ones by others, the differences would -become greater, and would be noted as forming two sub-breeds; finally, after +domestic productions. We shall here find something analogous. A fancier +is struck by a pigeon having a slightly shorter beak; another fancier is +struck by a pigeon having a rather longer beak; and on the acknowledged +principle that “fanciers do not and will not admire a medium standard, +but like extremes,” they both go on (as has actually occurred with +tumbler-pigeons) choosing and breeding from birds with longer and longer +beaks, or with shorter and shorter beaks. Again, we may suppose that at +an early period one man preferred swifter horses; another stronger and +more bulky horses. The early differences would be very slight; in the +course of time, from the continued selection of swifter horses by some +breeders, and of stronger ones by others, the differences would become +greater, and would be noted as forming two sub-breeds; finally, after the lapse of centuries, the sub-breeds would become converted into two -well-established and distinct breeds. As the differences slowly become greater, -the inferior animals with intermediate characters, being neither very swift nor -very strong, will have been neglected, and will have tended to disappear. Here, -then, we see in man’s productions the action of what may be called the -principle of divergence, causing differences, at first barely appreciable, -steadily to increase, and the breeds to diverge in character both from each -other and from their common parent. +well-established and distinct breeds. As the differences slowly become +greater, the inferior animals with intermediate characters, being +neither very swift nor very strong, will have been neglected, and will +have tended to disappear. Here, then, we see in man’s productions the +action of what may be called the principle of divergence, causing +differences, at first barely appreciable, steadily to increase, and the +breeds to diverge in character both from each other and from their +common parent. But how, it may be asked, can any analogous principle apply in nature? I -believe it can and does apply most efficiently, from the simple circumstance -that the more diversified the descendants from any one species become in -structure, constitution, and habits, by so much will they be better enabled to -seize on many and widely diversified places in the polity of nature, and so be -enabled to increase in numbers. - -We can clearly see this in the case of animals with simple habits. Take the -case of a carnivorous quadruped, of which the number that can be supported in -any country has long ago arrived at its full average. If its natural powers of -increase be allowed to act, it can succeed in increasing (the country not -undergoing any change in its conditions) only by its varying descendants -seizing on places at present occupied by other animals: some of them, for -instance, being enabled to feed on new kinds of prey, either dead or alive; -some inhabiting new stations, climbing trees, frequenting water, and some -perhaps becoming less carnivorous. The more diversified in habits and structure -the descendants of our carnivorous animal became, the more places they would be -enabled to occupy. What applies to one animal will apply throughout all time to -all animals—that is, if they vary—for otherwise natural selection can do -nothing. So it will be with plants. It has been experimentally proved, that if -a plot of ground be sown with one species of grass, and a similar plot be sown -with several distinct genera of grasses, a greater number of plants and a -greater weight of dry herbage can thus be raised. The same has been found to -hold good when first one variety and then several mixed varieties of wheat have -been sown on equal spaces of ground. Hence, if any one species of grass were to -go on varying, and those varieties were continually selected which differed -from each other in at all the same manner as distinct species and genera of -grasses differ from each other, a greater number of individual plants of this -species of grass, including its modified descendants, would succeed in living -on the same piece of ground. And we well know that each species and each -variety of grass is annually sowing almost countless seeds; and thus, as it may -be said, is striving its utmost to increase its numbers. Consequently, I cannot -doubt that in the course of many thousands of generations, the most distinct -varieties of any one species of grass would always have the best chance of -succeeding and of increasing in numbers, and thus of supplanting the less -distinct varieties; and varieties, when rendered very distinct from each other, +believe it can and does apply most efficiently, from the simple +circumstance that the more diversified the descendants from any one +species become in structure, constitution, and habits, by so much will +they be better enabled to seize on many and widely diversified places in +the polity of nature, and so be enabled to increase in numbers. + +We can clearly see this in the case of animals with simple habits. Take +the case of a carnivorous quadruped, of which the number that can be +supported in any country has long ago arrived at its full average. If +its natural powers of increase be allowed to act, it can succeed in +increasing (the country not undergoing any change in its conditions) +only by its varying descendants seizing on places at present occupied by +other animals: some of them, for instance, being enabled to feed on new +kinds of prey, either dead or alive; some inhabiting new stations, +climbing trees, frequenting water, and some perhaps becoming less +carnivorous. The more diversified in habits and structure the +descendants of our carnivorous animal became, the more places they would +be enabled to occupy. What applies to one animal will apply throughout +all time to all animals—that is, if they vary—for otherwise natural +selection can do nothing. So it will be with plants. It has been +experimentally proved, that if a plot of ground be sown with one species +of grass, and a similar plot be sown with several distinct genera of +grasses, a greater number of plants and a greater weight of dry herbage +can thus be raised. The same has been found to hold good when first one +variety and then several mixed varieties of wheat have been sown on +equal spaces of ground. Hence, if any one species of grass were to go on +varying, and those varieties were continually selected which differed +from each other in at all the same manner as distinct species and genera +of grasses differ from each other, a greater number of individual plants +of this species of grass, including its modified descendants, would +succeed in living on the same piece of ground. And we well know that +each species and each variety of grass is annually sowing almost +countless seeds; and thus, as it may be said, is striving its utmost to +increase its numbers. Consequently, I cannot doubt that in the course of +many thousands of generations, the most distinct varieties of any one +species of grass would always have the best chance of succeeding and of +increasing in numbers, and thus of supplanting the less distinct +varieties; and varieties, when rendered very distinct from each other, take the rank of species. -The truth of the principle, that the greatest amount of life can be supported -by great diversification of structure, is seen under many natural -circumstances. In an extremely small area, especially if freely open to -immigration, and where the contest between individual and individual must be -severe, we always find great diversity in its inhabitants. For instance, I -found that a piece of turf, three feet by four in size, which had been exposed -for many years to exactly the same conditions, supported twenty species of -plants, and these belonged to eighteen genera and to eight orders, which shows -how much these plants differed from each other. So it is with the plants and -insects on small and uniform islets; and so in small ponds of fresh water. -Farmers find that they can raise most food by a rotation of plants belonging to -the most different orders: nature follows what may be called a simultaneous -rotation. Most of the animals and plants which live close round any small piece -of ground, could live on it (supposing it not to be in any way peculiar in its -nature), and may be said to be striving to the utmost to live there; but, it is -seen, that where they come into the closest competition with each other, the -advantages of diversification of structure, with the accompanying differences -of habit and constitution, determine that the inhabitants, which thus jostle -each other most closely, shall, as a general rule, belong to what we call +The truth of the principle, that the greatest amount of life can be +supported by great diversification of structure, is seen under many +natural circumstances. In an extremely small area, especially if freely +open to immigration, and where the contest between individual and +individual must be severe, we always find great diversity in its +inhabitants. For instance, I found that a piece of turf, three feet by +four in size, which had been exposed for many years to exactly the same +conditions, supported twenty species of plants, and these belonged to +eighteen genera and to eight orders, which shows how much these plants +differed from each other. So it is with the plants and insects on small +and uniform islets; and so in small ponds of fresh water. Farmers find +that they can raise most food by a rotation of plants belonging to the +most different orders: nature follows what may be called a simultaneous +rotation. Most of the animals and plants which live close round any +small piece of ground, could live on it (supposing it not to be in any +way peculiar in its nature), and may be said to be striving to the +utmost to live there; but, it is seen, that where they come into the +closest competition with each other, the advantages of diversification +of structure, with the accompanying differences of habit and +constitution, determine that the inhabitants, which thus jostle each +other most closely, shall, as a general rule, belong to what we call different genera and orders. -The same principle is seen in the naturalisation of plants through man’s agency -in foreign lands. It might have been expected that the plants which have -succeeded in becoming naturalised in any land would generally have been closely -allied to the indigenes; for these are commonly looked at as specially created -and adapted for their own country. It might, also, perhaps have been expected -that naturalised plants would have belonged to a few groups more especially -adapted to certain stations in their new homes. But the case is very different; -and Alph. De Candolle has well remarked in his great and admirable work, that -floras gain by naturalisation, proportionally with the number of the native -genera and species, far more in new genera than in new species. To give a -single instance: in the last edition of Dr. Asa Gray’s ‘Manual of the Flora of -the Northern United States,’ 260 naturalised plants are enumerated, and these -belong to 162 genera. We thus see that these naturalised plants are of a highly -diversified nature. They differ, moreover, to a large extent from the -indigenes, for out of the 162 genera, no less than 100 genera are not there -indigenous, and thus a large proportional addition is made to the genera of -these States. +The same principle is seen in the naturalisation of plants through man’s +agency in foreign lands. It might have been expected that the plants +which have succeeded in becoming naturalised in any land would generally +have been closely allied to the indigenes; for these are commonly looked +at as specially created and adapted for their own country. It might, +also, perhaps have been expected that naturalised plants would have +belonged to a few groups more especially adapted to certain stations in +their new homes. But the case is very different; and Alph. De Candolle +has well remarked in his great and admirable work, that floras gain by +naturalisation, proportionally with the number of the native genera and +species, far more in new genera than in new species. To give a single +instance: in the last edition of Dr. Asa Gray’s ‘Manual of the Flora of +the Northern United States,’ 260 naturalised plants are enumerated, and +these belong to 162 genera. We thus see that these naturalised plants +are of a highly diversified nature. They differ, moreover, to a large +extent from the indigenes, for out of the 162 genera, no less than 100 +genera are not there indigenous, and thus a large proportional addition +is made to the genera of these States. By considering the nature of the plants or animals which have struggled successfully with the indigenes of any country, and have there become -naturalised, we can gain some crude idea in what manner some of the natives -would have had to be modified, in order to have gained an advantage over the -other natives; and we may, I think, at least safely infer that diversification -of structure, amounting to new generic differences, would have been profitable -to them. - -The advantage of diversification in the inhabitants of the same region is, in -fact, the same as that of the physiological division of labour in the organs of -the same individual body—a subject so well elucidated by Milne Edwards. No -physiologist doubts that a stomach by being adapted to digest vegetable matter -alone, or flesh alone, draws most nutriment from these substances. So in the -general economy of any land, the more widely and perfectly the animals and -plants are diversified for different habits of life, so will a greater number -of individuals be capable of there supporting themselves. A set of animals, -with their organisation but little diversified, could hardly compete with a set -more perfectly diversified in structure. It may be doubted, for instance, -whether the Australian marsupials, which are divided into groups differing but -little from each other, and feebly representing, as Mr. Waterhouse and others -have remarked, our carnivorous, ruminant, and rodent mammals, could -successfully compete with these well-pronounced orders. In the Australian -mammals, we see the process of diversification in an early and incomplete stage -of development. After the foregoing discussion, which ought to have been much -amplified, we may, I think, assume that the modified descendants of any one -species will succeed by so much the better as they become more diversified in -structure, and are thus enabled to encroach on places occupied by other beings. -Now let us see how this principle of great benefit being derived from -divergence of character, combined with the principles of natural selection and -of extinction, will tend to act. - -The accompanying diagram will aid us in understanding this rather perplexing -subject. Let A to L represent the species of a genus large in its own country; -these species are supposed to resemble each other in unequal degrees, as is so -generally the case in nature, and as is represented in the diagram by the -letters standing at unequal distances. I have said a large genus, because we -have seen in the second chapter, that on an average more of the species of -large genera vary than of small genera; and the varying species of the large -genera present a greater number of varieties. We have, also, seen that the -species, which are the commonest and the most widely-diffused, vary more than -rare species with restricted ranges. Let (A) be a common, widely-diffused, and -varying species, belonging to a genus large in its own country. The little fan -of diverging dotted lines of unequal lengths proceeding from (A), may represent -its varying offspring. The variations are supposed to be extremely slight, but -of the most diversified nature; they are not supposed all to appear -simultaneously, but often after long intervals of time; nor are they all -supposed to endure for equal periods. Only those variations which are in some -way profitable will be preserved or naturally selected. And here the importance -of the principle of benefit being derived from divergence of character comes -in; for this will generally lead to the most different or divergent variations -(represented by the outer dotted lines) being preserved and accumulated by -natural selection. When a dotted line reaches one of the horizontal lines, and -is there marked by a small numbered letter, a sufficient amount of variation is -supposed to have been accumulated to have formed a fairly well-marked variety, -such as would be thought worthy of record in a systematic work. - -The intervals between the horizontal lines in the diagram, may represent each a -thousand generations; but it would have been better if each had represented ten -thousand generations. After a thousand generations, species (A) is supposed to -have produced two fairly well-marked varieties, namely a^1 and m^1. These two -varieties will generally continue to be exposed to the same conditions which -made their parents variable, and the tendency to variability is in itself -hereditary, consequently they will tend to vary, and generally to vary in -nearly the same manner as their parents varied. Moreover, these two varieties, -being only slightly modified forms, will tend to inherit those advantages which -made their common parent (A) more numerous than most of the other inhabitants -of the same country; they will likewise partake of those more general -advantages which made the genus to which the parent-species belonged, a large -genus in its own country. And these circumstances we know to be favourable to -the production of new varieties. +naturalised, we can gain some crude idea in what manner some of the +natives would have had to be modified, in order to have gained an +advantage over the other natives; and we may, I think, at least safely +infer that diversification of structure, amounting to new generic +differences, would have been profitable to them. + +The advantage of diversification in the inhabitants of the same region +is, in fact, the same as that of the physiological division of labour in +the organs of the same individual body—a subject so well elucidated by +Milne Edwards. No physiologist doubts that a stomach by being adapted to +digest vegetable matter alone, or flesh alone, draws most nutriment from +these substances. So in the general economy of any land, the more widely +and perfectly the animals and plants are diversified for different +habits of life, so will a greater number of individuals be capable of +there supporting themselves. A set of animals, with their organisation +but little diversified, could hardly compete with a set more perfectly +diversified in structure. It may be doubted, for instance, whether the +Australian marsupials, which are divided into groups differing but +little from each other, and feebly representing, as Mr. Waterhouse and +others have remarked, our carnivorous, ruminant, and rodent mammals, +could successfully compete with these well-pronounced orders. In the +Australian mammals, we see the process of diversification in an early +and incomplete stage of development. After the foregoing discussion, +which ought to have been much amplified, we may, I think, assume that +the modified descendants of any one species will succeed by so much the +better as they become more diversified in structure, and are thus +enabled to encroach on places occupied by other beings. Now let us see +how this principle of great benefit being derived from divergence of +character, combined with the principles of natural selection and of +extinction, will tend to act. + +The accompanying diagram will aid us in understanding this rather +perplexing subject. Let A to L represent the species of a genus large in +its own country; these species are supposed to resemble each other in +unequal degrees, as is so generally the case in nature, and as is +represented in the diagram by the letters standing at unequal distances. +I have said a large genus, because we have seen in the second chapter, +that on an average more of the species of large genera vary than of +small genera; and the varying species of the large genera present a +greater number of varieties. We have, also, seen that the species, which +are the commonest and the most widely-diffused, vary more than rare +species with restricted ranges. Let (A) be a common, widely-diffused, +and varying species, belonging to a genus large in its own country. The +little fan of diverging dotted lines of unequal lengths proceeding from +(A), may represent its varying offspring. The variations are supposed to +be extremely slight, but of the most diversified nature; they are not +supposed all to appear simultaneously, but often after long intervals of +time; nor are they all supposed to endure for equal periods. Only those +variations which are in some way profitable will be preserved or +naturally selected. And here the importance of the principle of benefit +being derived from divergence of character comes in; for this will +generally lead to the most different or divergent variations +(represented by the outer dotted lines) being preserved and accumulated +by natural selection. When a dotted line reaches one of the horizontal +lines, and is there marked by a small numbered letter, a sufficient +amount of variation is supposed to have been accumulated to have formed +a fairly well-marked variety, such as would be thought worthy of record +in a systematic work. + +The intervals between the horizontal lines in the diagram, may represent +each a thousand generations; but it would have been better if each had +represented ten thousand generations. After a thousand generations, +species (A) is supposed to have produced two fairly well-marked +varieties, namely a^1 and m^1. These two varieties will generally +continue to be exposed to the same conditions which made their parents +variable, and the tendency to variability is in itself hereditary, +consequently they will tend to vary, and generally to vary in nearly the +same manner as their parents varied. Moreover, these two varieties, +being only slightly modified forms, will tend to inherit those +advantages which made their common parent (A) more numerous than most of +the other inhabitants of the same country; they will likewise partake of +those more general advantages which made the genus to which the +parent-species belonged, a large genus in its own country. And these +circumstances we know to be favourable to the production of new +varieties. If, then, these two varieties be variable, the most divergent of their -variations will generally be preserved during the next thousand generations. -And after this interval, variety a^1 is supposed in the diagram to have -produced variety a^2, which will, owing to the principle of divergence, differ -more from (A) than did variety a^1. Variety m^1 is supposed to have produced -two varieties, namely m^2 and s^2, differing from each other, and more -considerably from their common parent (A). We may continue the process by -similar steps for any length of time; some of the varieties, after each -thousand generations, producing only a single variety, but in a more and more -modified condition, some producing two or three varieties, and some failing to -produce any. Thus the varieties or modified descendants, proceeding from the -common parent (A), will generally go on increasing in number and diverging in -character. In the diagram the process is represented up to the ten-thousandth -generation, and under a condensed and simplified form up to the -fourteen-thousandth generation. - -But I must here remark that I do not suppose that the process ever goes on so -regularly as is represented in the diagram, though in itself made somewhat -irregular. I am far from thinking that the most divergent varieties will -invariably prevail and multiply: a medium form may often long endure, and may -or may not produce more than one modified descendant; for natural selection -will always act according to the nature of the places which are either -unoccupied or not perfectly occupied by other beings; and this will depend on -infinitely complex relations. But as a general rule, the more diversified in -structure the descendants from any one species can be rendered, the more places -they will be enabled to seize on, and the more their modified progeny will be -increased. In our diagram the line of succession is broken at regular intervals -by small numbered letters marking the successive forms which have become -sufficiently distinct to be recorded as varieties. But these breaks are -imaginary, and might have been inserted anywhere, after intervals long enough -to have allowed the accumulation of a considerable amount of divergent -variation. - -As all the modified descendants from a common and widely-diffused species, -belonging to a large genus, will tend to partake of the same advantages which -made their parent successful in life, they will generally go on multiplying in -number as well as diverging in character: this is represented in the diagram by -the several divergent branches proceeding from (A). The modified offspring from -the later and more highly improved branches in the lines of descent, will, it -is probable, often take the place of, and so destroy, the earlier and less -improved branches: this is represented in the diagram by some of the lower -branches not reaching to the upper horizontal lines. In some cases I do not -doubt that the process of modification will be confined to a single line of -descent, and the number of the descendants will not be increased; although the -amount of divergent modification may have been increased in the successive -generations. This case would be represented in the diagram, if all the lines -proceeding from (A) were removed, excepting that from a^1 to a^10. In the same -way, for instance, the English race-horse and English pointer have apparently -both gone on slowly diverging in character from their original stocks, without -either having given off any fresh branches or races. - -After ten thousand generations, species (A) is supposed to have produced three -forms, a^10, f^10, and m^10, which, from having diverged in character during -the successive generations, will have come to differ largely, but perhaps -unequally, from each other and from their common parent. If we suppose the -amount of change between each horizontal line in our diagram to be excessively -small, these three forms may still be only well-marked varieties; or they may -have arrived at the doubtful category of sub-species; but we have only to -suppose the steps in the process of modification to be more numerous or greater -in amount, to convert these three forms into well-defined species: thus the -diagram illustrates the steps by which the small differences distinguishing -varieties are increased into the larger differences distinguishing species. By -continuing the same process for a greater number of generations (as shown in -the diagram in a condensed and simplified manner), we get eight species, marked -by the letters between a^14 and m^14, all descended from (A). Thus, as I -believe, species are multiplied and genera are formed. - -In a large genus it is probable that more than one species would vary. In the -diagram I have assumed that a second species (I) has produced, by analogous -steps, after ten thousand generations, either two well-marked varieties (w^10 -and z^10) or two species, according to the amount of change supposed to be -represented between the horizontal lines. After fourteen thousand generations, -six new species, marked by the letters n^14 to z^14, are supposed to have been -produced. In each genus, the species, which are already extremely different in -character, will generally tend to produce the greatest number of modified -descendants; for these will have the best chance of filling new and widely -different places in the polity of nature: hence in the diagram I have chosen -the extreme species (A), and the nearly extreme species (I), as those which -have largely varied, and have given rise to new varieties and species. The -other nine species (marked by capital letters) of our original genus, may for a -long period continue transmitting unaltered descendants; and this is shown in -the diagram by the dotted lines not prolonged far upwards from want of space. - -But during the process of modification, represented in the diagram, another of -our principles, namely that of extinction, will have played an important part. -As in each fully stocked country natural selection necessarily acts by the -selected form having some advantage in the struggle for life over other forms, -there will be a constant tendency in the improved descendants of any one -species to supplant and exterminate in each stage of descent their predecessors -and their original parent. For it should be remembered that the competition -will generally be most severe between those forms which are most nearly related -to each other in habits, constitution, and structure. Hence all the -intermediate forms between the earlier and later states, that is between the -less and more improved state of a species, as well as the original -parent-species itself, will generally tend to become extinct. So it probably -will be with many whole collateral lines of descent, which will be conquered by -later and improved lines of descent. If, however, the modified offspring of a -species get into some distinct country, or become quickly adapted to some quite -new station, in which child and parent do not come into competition, both may -continue to exist. +variations will generally be preserved during the next thousand +generations. And after this interval, variety a^1 is supposed in the +diagram to have produced variety a^2, which will, owing to the principle +of divergence, differ more from (A) than did variety a^1. Variety m^1 is +supposed to have produced two varieties, namely m^2 and s^2, differing +from each other, and more considerably from their common parent (A). We +may continue the process by similar steps for any length of time; some +of the varieties, after each thousand generations, producing only a +single variety, but in a more and more modified condition, some +producing two or three varieties, and some failing to produce any. Thus +the varieties or modified descendants, proceeding from the common parent +(A), will generally go on increasing in number and diverging in +character. In the diagram the process is represented up to the +ten-thousandth generation, and under a condensed and simplified form up +to the fourteen-thousandth generation. + +But I must here remark that I do not suppose that the process ever goes +on so regularly as is represented in the diagram, though in itself made +somewhat irregular. I am far from thinking that the most divergent +varieties will invariably prevail and multiply: a medium form may often +long endure, and may or may not produce more than one modified +descendant; for natural selection will always act according to the +nature of the places which are either unoccupied or not perfectly +occupied by other beings; and this will depend on infinitely complex +relations. But as a general rule, the more diversified in structure the +descendants from any one species can be rendered, the more places they +will be enabled to seize on, and the more their modified progeny will be +increased. In our diagram the line of succession is broken at regular +intervals by small numbered letters marking the successive forms which +have become sufficiently distinct to be recorded as varieties. But these +breaks are imaginary, and might have been inserted anywhere, after +intervals long enough to have allowed the accumulation of a considerable +amount of divergent variation. + +As all the modified descendants from a common and widely-diffused +species, belonging to a large genus, will tend to partake of the same +advantages which made their parent successful in life, they will +generally go on multiplying in number as well as diverging in character: +this is represented in the diagram by the several divergent branches +proceeding from (A). The modified offspring from the later and more +highly improved branches in the lines of descent, will, it is probable, +often take the place of, and so destroy, the earlier and less improved +branches: this is represented in the diagram by some of the lower +branches not reaching to the upper horizontal lines. In some cases I do +not doubt that the process of modification will be confined to a single +line of descent, and the number of the descendants will not be +increased; although the amount of divergent modification may have been +increased in the successive generations. This case would be represented +in the diagram, if all the lines proceeding from (A) were removed, +excepting that from a^1 to a^10. In the same way, for instance, the +English race-horse and English pointer have apparently both gone on +slowly diverging in character from their original stocks, without either +having given off any fresh branches or races. + +After ten thousand generations, species (A) is supposed to have produced +three forms, a^10, f^10, and m^10, which, from having diverged in +character during the successive generations, will have come to differ +largely, but perhaps unequally, from each other and from their common +parent. If we suppose the amount of change between each horizontal line +in our diagram to be excessively small, these three forms may still be +only well-marked varieties; or they may have arrived at the doubtful +category of sub-species; but we have only to suppose the steps in the +process of modification to be more numerous or greater in amount, to +convert these three forms into well-defined species: thus the diagram +illustrates the steps by which the small differences distinguishing +varieties are increased into the larger differences distinguishing +species. By continuing the same process for a greater number of +generations (as shown in the diagram in a condensed and simplified +manner), we get eight species, marked by the letters between a^14 and +m^14, all descended from (A). Thus, as I believe, species are multiplied +and genera are formed. + +In a large genus it is probable that more than one species would vary. +In the diagram I have assumed that a second species (I) has produced, by +analogous steps, after ten thousand generations, either two well-marked +varieties (w^10 and z^10) or two species, according to the amount of +change supposed to be represented between the horizontal lines. After +fourteen thousand generations, six new species, marked by the letters +n^14 to z^14, are supposed to have been produced. In each genus, the +species, which are already extremely different in character, will +generally tend to produce the greatest number of modified descendants; +for these will have the best chance of filling new and widely different +places in the polity of nature: hence in the diagram I have chosen the +extreme species (A), and the nearly extreme species (I), as those which +have largely varied, and have given rise to new varieties and species. +The other nine species (marked by capital letters) of our original +genus, may for a long period continue transmitting unaltered +descendants; and this is shown in the diagram by the dotted lines not +prolonged far upwards from want of space. + +But during the process of modification, represented in the diagram, +another of our principles, namely that of extinction, will have played +an important part. As in each fully stocked country natural selection +necessarily acts by the selected form having some advantage in the +struggle for life over other forms, there will be a constant tendency in +the improved descendants of any one species to supplant and exterminate +in each stage of descent their predecessors and their original parent. +For it should be remembered that the competition will generally be most +severe between those forms which are most nearly related to each other +in habits, constitution, and structure. Hence all the intermediate forms +between the earlier and later states, that is between the less and more +improved state of a species, as well as the original parent-species +itself, will generally tend to become extinct. So it probably will be +with many whole collateral lines of descent, which will be conquered by +later and improved lines of descent. If, however, the modified offspring +of a species get into some distinct country, or become quickly adapted +to some quite new station, in which child and parent do not come into +competition, both may continue to exist. If then our diagram be assumed to represent a considerable amount of modification, species (A) and all the earlier varieties will have become -extinct, having been replaced by eight new species (a^14 to m^14); and (I) will -have been replaced by six (n^14 to z^14) new species. +extinct, having been replaced by eight new species (a^14 to m^14); and +(I) will have been replaced by six (n^14 to z^14) new species. But we may go further than this. The original species of our genus were -supposed to resemble each other in unequal degrees, as is so generally the case -in nature; species (A) being more nearly related to B, C, and D, than to the -other species; and species (I) more to G, H, K, L, than to the others. These -two species (A) and (I), were also supposed to be very common and widely -diffused species, so that they must originally have had some advantage over -most of the other species of the genus. Their modified descendants, fourteen in -number at the fourteen-thousandth generation, will probably have inherited some -of the same advantages: they have also been modified and improved in a -diversified manner at each stage of descent, so as to have become adapted to -many related places in the natural economy of their country. It seems, -therefore, to me extremely probable that they will have taken the places of, -and thus exterminated, not only their parents (A) and (I), but likewise some of -the original species which were most nearly related to their parents. Hence -very few of the original species will have transmitted offspring to the -fourteen-thousandth generation. We may suppose that only one (F), of the two -species which were least closely related to the other nine original species, -has transmitted descendants to this late stage of descent. - -The new species in our diagram descended from the original eleven species, will -now be fifteen in number. Owing to the divergent tendency of natural selection, -the extreme amount of difference in character between species a^14 and z^14 -will be much greater than that between the most different of the original -eleven species. The new species, moreover, will be allied to each other in a -widely different manner. Of the eight descendants from (A) the three marked a^ -14, q^14, p^14, will be nearly related from having recently branched off from a -^10; b^14 and f^14, from having diverged at an earlier period from a^5, will be -in some degree distinct from the three first-named species; and lastly, o^14, e -^14, and m^14, will be nearly related one to the other, but from having -diverged at the first commencement of the process of modification, will be -widely different from the other five species, and may constitute a sub-genus or -even a distinct genus. - -The six descendants from (I) will form two sub-genera or even genera. But as -the original species (I) differed largely from (A), standing nearly at the -extreme points of the original genus, the six descendants from (I) will, owing -to inheritance, differ considerably from the eight descendants from (A); the -two groups, moreover, are supposed to have gone on diverging in different -directions. The intermediate species, also (and this is a very important -consideration), which connected the original species (A) and (I), have all -become, excepting (F), extinct, and have left no descendants. Hence the six new -species descended from (I), and the eight descended from (A), will have to be -ranked as very distinct genera, or even as distinct sub-families. - -Thus it is, as I believe, that two or more genera are produced by descent, with -modification, from two or more species of the same genus. And the two or more -parent-species are supposed to have descended from some one species of an -earlier genus. In our diagram, this is indicated by the broken lines, beneath -the capital letters, converging in sub-branches downwards towards a single -point; this point representing a single species, the supposed single parent of -our several new sub-genera and genera. - -It is worth while to reflect for a moment on the character of the new species F -^14, which is supposed not to have diverged much in character, but to have -retained the form of (F), either unaltered or altered only in a slight degree. -In this case, its affinities to the other fourteen new species will be of a -curious and circuitous nature. Having descended from a form which stood between -the two parent-species (A) and (I), now supposed to be extinct and unknown, it -will be in some degree intermediate in character between the two groups -descended from these species. But as these two groups have gone on diverging in -character from the type of their parents, the new species (F^14) will not be -directly intermediate between them, but rather between types of the two groups; -and every naturalist will be able to bring some such case before his mind. - -In the diagram, each horizontal line has hitherto been supposed to represent a -thousand generations, but each may represent a million or hundred million -generations, and likewise a section of the successive strata of the earth’s -crust including extinct remains. We shall, when we come to our chapter on -Geology, have to refer again to this subject, and I think we shall then see -that the diagram throws light on the affinities of extinct beings, which, -though generally belonging to the same orders, or families, or genera, with -those now living, yet are often, in some degree, intermediate in character -between existing groups; and we can understand this fact, for the extinct -species lived at very ancient epochs when the branching lines of descent had -diverged less. - -I see no reason to limit the process of modification, as now explained, to the -formation of genera alone. If, in our diagram, we suppose the amount of change -represented by each successive group of diverging dotted lines to be very -great, the forms marked a^14 to p^14, those marked b^14 and f^14, and those -marked o^14 to m^14, will form three very distinct genera. We shall also have -two very distinct genera descended from (I) and as these latter two genera, -both from continued divergence of character and from inheritance from a -different parent, will differ widely from the three genera descended from (A), -the two little groups of genera will form two distinct families, or even -orders, according to the amount of divergent modification supposed to be -represented in the diagram. And the two new families, or orders, will have -descended from two species of the original genus; and these two species are -supposed to have descended from one species of a still more ancient and unknown -genus. - -We have seen that in each country it is the species of the larger genera which -oftenest present varieties or incipient species. This, indeed, might have been -expected; for as natural selection acts through one form having some advantage -over other forms in the struggle for existence, it will chiefly act on those -which already have some advantage; and the largeness of any group shows that -its species have inherited from a common ancestor some advantage in common. -Hence, the struggle for the production of new and modified descendants, will -mainly lie between the larger groups, which are all trying to increase in -number. One large group will slowly conquer another large group, reduce its -numbers, and thus lessen its chance of further variation and improvement. -Within the same large group, the later and more highly perfected sub-groups, -from branching out and seizing on many new places in the polity of Nature, will -constantly tend to supplant and destroy the earlier and less improved -sub-groups. Small and broken groups and sub-groups will finally tend to -disappear. Looking to the future, we can predict that the groups of organic -beings which are now large and triumphant, and which are least broken up, that -is, which as yet have suffered least extinction, will for a long period -continue to increase. But which groups will ultimately prevail, no man can -predict; for we well know that many groups, formerly most extensively -developed, have now become extinct. Looking still more remotely to the future, -we may predict that, owing to the continued and steady increase of the larger -groups, a multitude of smaller groups will become utterly extinct, and leave no -modified descendants; and consequently that of the species living at any one -period, extremely few will transmit descendants to a remote futurity. I shall -have to return to this subject in the chapter on Classification, but I may add -that on this view of extremely few of the more ancient species having -transmitted descendants, and on the view of all the descendants of the same -species making a class, we can understand how it is that there exist but very -few classes in each main division of the animal and vegetable kingdoms. -Although extremely few of the most ancient species may now have living and -modified descendants, yet at the most remote geological period, the earth may -have been as well peopled with many species of many genera, families, orders, -and classes, as at the present day. - -Summary of the Chapter.—If during the long course of ages and under varying -conditions of life, organic beings vary at all in the several parts of their -organisation, and I think this cannot be disputed; if there be, owing to the -high geometrical powers of increase of each species, at some age, season, or -year, a severe struggle for life, and this certainly cannot be disputed; then, -considering the infinite complexity of the relations of all organic beings to -each other and to their conditions of existence, causing an infinite diversity -in structure, constitution, and habits, to be advantageous to them, I think it -would be a most extraordinary fact if no variation ever had occurred useful to -each being’s own welfare, in the same way as so many variations have occurred -useful to man. But if variations useful to any organic being do occur, -assuredly individuals thus characterised will have the best chance of being -preserved in the struggle for life; and from the strong principle of -inheritance they will tend to produce offspring similarly characterised. This -principle of preservation, I have called, for the sake of brevity, Natural -Selection. Natural selection, on the principle of qualities being inherited at -corresponding ages, can modify the egg, seed, or young, as easily as the adult. -Amongst many animals, sexual selection will give its aid to ordinary selection, -by assuring to the most vigorous and best adapted males the greatest number of -offspring. Sexual selection will also give characters useful to the males -alone, in their struggles with other males. - -Whether natural selection has really thus acted in nature, in modifying and -adapting the various forms of life to their several conditions and stations, -must be judged of by the general tenour and balance of evidence given in the -following chapters. But we already see how it entails extinction; and how -largely extinction has acted in the world’s history, geology plainly declares. -Natural selection, also, leads to divergence of character; for more living -beings can be supported on the same area the more they diverge in structure, -habits, and constitution, of which we see proof by looking at the inhabitants -of any small spot or at naturalised productions. Therefore during the -modification of the descendants of any one species, and during the incessant -struggle of all species to increase in numbers, the more diversified these -descendants become, the better will be their chance of succeeding in the battle -of life. Thus the small differences distinguishing varieties of the same -species, will steadily tend to increase till they come to equal the greater -differences between species of the same genus, or even of distinct genera. - -We have seen that it is the common, the widely-diffused, and widely-ranging -species, belonging to the larger genera, which vary most; and these will tend -to transmit to their modified offspring that superiority which now makes them -dominant in their own countries. Natural selection, as has just been remarked, -leads to divergence of character and to much extinction of the less improved -and intermediate forms of life. On these principles, I believe, the nature of -the affinities of all organic beings may be explained. It is a truly wonderful -fact—the wonder of which we are apt to overlook from familiarity—that all -animals and all plants throughout all time and space should be related to each -other in group subordinate to group, in the manner which we everywhere -behold—namely, varieties of the same species most closely related together, -species of the same genus less closely and unequally related together, forming -sections and sub-genera, species of distinct genera much less closely related, -and genera related in different degrees, forming sub-families, families, -orders, sub-classes, and classes. The several subordinate groups in any class +supposed to resemble each other in unequal degrees, as is so generally +the case in nature; species (A) being more nearly related to B, C, and +D, than to the other species; and species (I) more to G, H, K, L, than +to the others. These two species (A) and (I), were also supposed to be +very common and widely diffused species, so that they must originally +have had some advantage over most of the other species of the genus. +Their modified descendants, fourteen in number at the +fourteen-thousandth generation, will probably have inherited some of the +same advantages: they have also been modified and improved in a +diversified manner at each stage of descent, so as to have become +adapted to many related places in the natural economy of their country. +It seems, therefore, to me extremely probable that they will have taken +the places of, and thus exterminated, not only their parents (A) and +(I), but likewise some of the original species which were most nearly +related to their parents. Hence very few of the original species will +have transmitted offspring to the fourteen-thousandth generation. We may +suppose that only one (F), of the two species which were least closely +related to the other nine original species, has transmitted descendants +to this late stage of descent. + +The new species in our diagram descended from the original eleven +species, will now be fifteen in number. Owing to the divergent tendency +of natural selection, the extreme amount of difference in character +between species a^14 and z^14 will be much greater than that between the +most different of the original eleven species. The new species, +moreover, will be allied to each other in a widely different manner. Of +the eight descendants from (A) the three marked a^ 14, q^14, p^14, will +be nearly related from having recently branched off from a ^10; b^14 and +f^14, from having diverged at an earlier period from a^5, will be in +some degree distinct from the three first-named species; and lastly, +o^14, e ^14, and m^14, will be nearly related one to the other, but from +having diverged at the first commencement of the process of +modification, will be widely different from the other five species, and +may constitute a sub-genus or even a distinct genus. + +The six descendants from (I) will form two sub-genera or even genera. +But as the original species (I) differed largely from (A), standing +nearly at the extreme points of the original genus, the six descendants +from (I) will, owing to inheritance, differ considerably from the eight +descendants from (A); the two groups, moreover, are supposed to have +gone on diverging in different directions. The intermediate species, +also (and this is a very important consideration), which connected the +original species (A) and (I), have all become, excepting (F), extinct, +and have left no descendants. Hence the six new species descended from +(I), and the eight descended from (A), will have to be ranked as very +distinct genera, or even as distinct sub-families. + +Thus it is, as I believe, that two or more genera are produced by +descent, with modification, from two or more species of the same genus. +And the two or more parent-species are supposed to have descended from +some one species of an earlier genus. In our diagram, this is indicated +by the broken lines, beneath the capital letters, converging in +sub-branches downwards towards a single point; this point representing a +single species, the supposed single parent of our several new sub-genera +and genera. + +It is worth while to reflect for a moment on the character of the new +species F ^14, which is supposed not to have diverged much in character, +but to have retained the form of (F), either unaltered or altered only +in a slight degree. In this case, its affinities to the other fourteen +new species will be of a curious and circuitous nature. Having descended +from a form which stood between the two parent-species (A) and (I), now +supposed to be extinct and unknown, it will be in some degree +intermediate in character between the two groups descended from these +species. But as these two groups have gone on diverging in character +from the type of their parents, the new species (F^14) will not be +directly intermediate between them, but rather between types of the two +groups; and every naturalist will be able to bring some such case before +his mind. + +In the diagram, each horizontal line has hitherto been supposed to +represent a thousand generations, but each may represent a million or +hundred million generations, and likewise a section of the successive +strata of the earth’s crust including extinct remains. We shall, when we +come to our chapter on Geology, have to refer again to this subject, and +I think we shall then see that the diagram throws light on the +affinities of extinct beings, which, though generally belonging to the +same orders, or families, or genera, with those now living, yet are +often, in some degree, intermediate in character between existing +groups; and we can understand this fact, for the extinct species lived +at very ancient epochs when the branching lines of descent had diverged +less. + +I see no reason to limit the process of modification, as now explained, +to the formation of genera alone. If, in our diagram, we suppose the +amount of change represented by each successive group of diverging +dotted lines to be very great, the forms marked a^14 to p^14, those +marked b^14 and f^14, and those marked o^14 to m^14, will form three +very distinct genera. We shall also have two very distinct genera +descended from (I) and as these latter two genera, both from continued +divergence of character and from inheritance from a different parent, +will differ widely from the three genera descended from (A), the two +little groups of genera will form two distinct families, or even orders, +according to the amount of divergent modification supposed to be +represented in the diagram. And the two new families, or orders, will +have descended from two species of the original genus; and these two +species are supposed to have descended from one species of a still more +ancient and unknown genus. + +We have seen that in each country it is the species of the larger genera +which oftenest present varieties or incipient species. This, indeed, +might have been expected; for as natural selection acts through one form +having some advantage over other forms in the struggle for existence, it +will chiefly act on those which already have some advantage; and the +largeness of any group shows that its species have inherited from a +common ancestor some advantage in common. Hence, the struggle for the +production of new and modified descendants, will mainly lie between the +larger groups, which are all trying to increase in number. One large +group will slowly conquer another large group, reduce its numbers, and +thus lessen its chance of further variation and improvement. Within the +same large group, the later and more highly perfected sub-groups, from +branching out and seizing on many new places in the polity of Nature, +will constantly tend to supplant and destroy the earlier and less +improved sub-groups. Small and broken groups and sub-groups will finally +tend to disappear. Looking to the future, we can predict that the groups +of organic beings which are now large and triumphant, and which are +least broken up, that is, which as yet have suffered least extinction, +will for a long period continue to increase. But which groups will +ultimately prevail, no man can predict; for we well know that many +groups, formerly most extensively developed, have now become extinct. +Looking still more remotely to the future, we may predict that, owing to +the continued and steady increase of the larger groups, a multitude of +smaller groups will become utterly extinct, and leave no modified +descendants; and consequently that of the species living at any one +period, extremely few will transmit descendants to a remote futurity. I +shall have to return to this subject in the chapter on Classification, +but I may add that on this view of extremely few of the more ancient +species having transmitted descendants, and on the view of all the +descendants of the same species making a class, we can understand how it +is that there exist but very few classes in each main division of the +animal and vegetable kingdoms. Although extremely few of the most +ancient species may now have living and modified descendants, yet at the +most remote geological period, the earth may have been as well peopled +with many species of many genera, families, orders, and classes, as at +the present day. + +Summary of the Chapter.—If during the long course of ages and under +varying conditions of life, organic beings vary at all in the several +parts of their organisation, and I think this cannot be disputed; if +there be, owing to the high geometrical powers of increase of each +species, at some age, season, or year, a severe struggle for life, and +this certainly cannot be disputed; then, considering the infinite +complexity of the relations of all organic beings to each other and to +their conditions of existence, causing an infinite diversity in +structure, constitution, and habits, to be advantageous to them, I think +it would be a most extraordinary fact if no variation ever had occurred +useful to each being’s own welfare, in the same way as so many +variations have occurred useful to man. But if variations useful to any +organic being do occur, assuredly individuals thus characterised will +have the best chance of being preserved in the struggle for life; and +from the strong principle of inheritance they will tend to produce +offspring similarly characterised. This principle of preservation, I +have called, for the sake of brevity, Natural Selection. Natural +selection, on the principle of qualities being inherited at +corresponding ages, can modify the egg, seed, or young, as easily as the +adult. Amongst many animals, sexual selection will give its aid to +ordinary selection, by assuring to the most vigorous and best adapted +males the greatest number of offspring. Sexual selection will also give +characters useful to the males alone, in their struggles with other +males. + +Whether natural selection has really thus acted in nature, in modifying +and adapting the various forms of life to their several conditions and +stations, must be judged of by the general tenour and balance of +evidence given in the following chapters. But we already see how it +entails extinction; and how largely extinction has acted in the world’s +history, geology plainly declares. Natural selection, also, leads to +divergence of character; for more living beings can be supported on the +same area the more they diverge in structure, habits, and constitution, +of which we see proof by looking at the inhabitants of any small spot or +at naturalised productions. Therefore during the modification of the +descendants of any one species, and during the incessant struggle of all +species to increase in numbers, the more diversified these descendants +become, the better will be their chance of succeeding in the battle of +life. Thus the small differences distinguishing varieties of the same +species, will steadily tend to increase till they come to equal the +greater differences between species of the same genus, or even of +distinct genera. + +We have seen that it is the common, the widely-diffused, and +widely-ranging species, belonging to the larger genera, which vary most; +and these will tend to transmit to their modified offspring that +superiority which now makes them dominant in their own countries. +Natural selection, as has just been remarked, leads to divergence of +character and to much extinction of the less improved and intermediate +forms of life. On these principles, I believe, the nature of the +affinities of all organic beings may be explained. It is a truly +wonderful fact—the wonder of which we are apt to overlook from +familiarity—that all animals and all plants throughout all time and +space should be related to each other in group subordinate to group, in +the manner which we everywhere behold—namely, varieties of the same +species most closely related together, species of the same genus less +closely and unequally related together, forming sections and sub-genera, +species of distinct genera much less closely related, and genera related +in different degrees, forming sub-families, families, orders, +sub-classes, and classes. The several subordinate groups in any class cannot be ranked in a single file, but seem rather to be clustered round -points, and these round other points, and so on in almost endless cycles. On -the view that each species has been independently created, I can see no -explanation of this great fact in the classification of all organic beings; -but, to the best of my judgment, it is explained through inheritance and the -complex action of natural selection, entailing extinction and divergence of -character, as we have seen illustrated in the diagram. +points, and these round other points, and so on in almost endless +cycles. On the view that each species has been independently created, I +can see no explanation of this great fact in the classification of all +organic beings; but, to the best of my judgment, it is explained through +inheritance and the complex action of natural selection, entailing +extinction and divergence of character, as we have seen illustrated in +the diagram. The affinities of all the beings of the same class have sometimes been -represented by a great tree. I believe this simile largely speaks the truth. -The green and budding twigs may represent existing species; and those produced -during each former year may represent the long succession of extinct species. -At each period of growth all the growing twigs have tried to branch out on all -sides, and to overtop and kill the surrounding twigs and branches, in the same -manner as species and groups of species have tried to overmaster other species -in the great battle for life. The limbs divided into great branches, and these -into lesser and lesser branches, were themselves once, when the tree was small, -budding twigs; and this connexion of the former and present buds by ramifying -branches may well represent the classification of all extinct and living -species in groups subordinate to groups. Of the many twigs which flourished -when the tree was a mere bush, only two or three, now grown into great -branches, yet survive and bear all the other branches; so with the species -which lived during long-past geological periods, very few now have living and -modified descendants. From the first growth of the tree, many a limb and branch -has decayed and dropped off; and these lost branches of various sizes may -represent those whole orders, families, and genera which have now no living -representatives, and which are known to us only from having been found in a -fossil state. As we here and there see a thin straggling branch springing from -a fork low down in a tree, and which by some chance has been favoured and is -still alive on its summit, so we occasionally see an animal like the -Ornithorhynchus or Lepidosiren, which in some small degree connects by its -affinities two large branches of life, and which has apparently been saved from -fatal competition by having inhabited a protected station. As buds give rise by -growth to fresh buds, and these, if vigorous, branch out and overtop on all -sides many a feebler branch, so by generation I believe it has been with the -great Tree of Life, which fills with its dead and broken branches the crust of -the earth, and covers the surface with its ever branching and beautiful -ramifications. - -CHAPTER V. -LAWS OF VARIATION. +represented by a great tree. I believe this simile largely speaks the +truth. The green and budding twigs may represent existing species; and +those produced during each former year may represent the long succession +of extinct species. At each period of growth all the growing twigs have +tried to branch out on all sides, and to overtop and kill the +surrounding twigs and branches, in the same manner as species and groups +of species have tried to overmaster other species in the great battle +for life. The limbs divided into great branches, and these into lesser +and lesser branches, were themselves once, when the tree was small, +budding twigs; and this connexion of the former and present buds by +ramifying branches may well represent the classification of all extinct +and living species in groups subordinate to groups. Of the many twigs +which flourished when the tree was a mere bush, only two or three, now +grown into great branches, yet survive and bear all the other branches; +so with the species which lived during long-past geological periods, +very few now have living and modified descendants. From the first growth +of the tree, many a limb and branch has decayed and dropped off; and +these lost branches of various sizes may represent those whole orders, +families, and genera which have now no living representatives, and which +are known to us only from having been found in a fossil state. As we +here and there see a thin straggling branch springing from a fork low +down in a tree, and which by some chance has been favoured and is still +alive on its summit, so we occasionally see an animal like the +Ornithorhynchus or Lepidosiren, which in some small degree connects by +its affinities two large branches of life, and which has apparently been +saved from fatal competition by having inhabited a protected station. As +buds give rise by growth to fresh buds, and these, if vigorous, branch +out and overtop on all sides many a feebler branch, so by generation I +believe it has been with the great Tree of Life, which fills with its +dead and broken branches the crust of the earth, and covers the surface +with its ever branching and beautiful ramifications. + +CHAPTER V. LAWS OF VARIATION. Effects of external conditions. Use and disuse, combined with natural -selection; organs of flight and of vision. Acclimatisation. Correlation of -growth. Compensation and economy of growth. False correlations. Multiple, -rudimentary, and lowly organised structures variable. Parts developed in an -unusual manner are highly variable: specific characters more variable than -generic: secondary sexual characters variable. Species of the same genus vary -in an analogous manner. Reversions to long lost characters. Summary. - -I have hitherto sometimes spoken as if the variations—so common and multiform -in organic beings under domestication, and in a lesser degree in those in a -state of nature—had been due to chance. This, of course, is a wholly incorrect -expression, but it serves to acknowledge plainly our ignorance of the cause of -each particular variation. Some authors believe it to be as much the function -of the reproductive system to produce individual differences, or very slight -deviations of structure, as to make the child like its parents. But the much -greater variability, as well as the greater frequency of monstrosities, under -domestication or cultivation, than under nature, leads me to believe that -deviations of structure are in some way due to the nature of the conditions of -life, to which the parents and their more remote ancestors have been exposed -during several generations. I have remarked in the first chapter—but a long -catalogue of facts which cannot be here given would be necessary to show the -truth of the remark—that the reproductive system is eminently susceptible to -changes in the conditions of life; and to this system being functionally -disturbed in the parents, I chiefly attribute the varying or plastic condition -of the offspring. The male and female sexual elements seem to be affected -before that union takes place which is to form a new being. In the case of -“sporting” plants, the bud, which in its earliest condition does not apparently -differ essentially from an ovule, is alone affected. But why, because the -reproductive system is disturbed, this or that part should vary more or less, -we are profoundly ignorant. Nevertheless, we can here and there dimly catch a -faint ray of light, and we may feel sure that there must be some cause for each -deviation of structure, however slight. - -How much direct effect difference of climate, food, etc., produces on any being -is extremely doubtful. My impression is, that the effect is extremely small in -the case of animals, but perhaps rather more in that of plants. We may, at -least, safely conclude that such influences cannot have produced the many -striking and complex co-adaptations of structure between one organic being and -another, which we see everywhere throughout nature. Some little influence may -be attributed to climate, food, etc.: thus, E. Forbes speaks confidently that -shells at their southern limit, and when living in shallow water, are more -brightly coloured than those of the same species further north or from greater +selection; organs of flight and of vision. Acclimatisation. Correlation +of growth. Compensation and economy of growth. False correlations. +Multiple, rudimentary, and lowly organised structures variable. Parts +developed in an unusual manner are highly variable: specific characters +more variable than generic: secondary sexual characters variable. +Species of the same genus vary in an analogous manner. Reversions to +long lost characters. Summary. + +I have hitherto sometimes spoken as if the variations—so common and +multiform in organic beings under domestication, and in a lesser degree +in those in a state of nature—had been due to chance. This, of course, +is a wholly incorrect expression, but it serves to acknowledge plainly +our ignorance of the cause of each particular variation. Some authors +believe it to be as much the function of the reproductive system to +produce individual differences, or very slight deviations of structure, +as to make the child like its parents. But the much greater variability, +as well as the greater frequency of monstrosities, under domestication +or cultivation, than under nature, leads me to believe that deviations +of structure are in some way due to the nature of the conditions of +life, to which the parents and their more remote ancestors have been +exposed during several generations. I have remarked in the first +chapter—but a long catalogue of facts which cannot be here given would +be necessary to show the truth of the remark—that the reproductive +system is eminently susceptible to changes in the conditions of life; +and to this system being functionally disturbed in the parents, I +chiefly attribute the varying or plastic condition of the offspring. The +male and female sexual elements seem to be affected before that union +takes place which is to form a new being. In the case of “sporting” +plants, the bud, which in its earliest condition does not apparently +differ essentially from an ovule, is alone affected. But why, because +the reproductive system is disturbed, this or that part should vary more +or less, we are profoundly ignorant. Nevertheless, we can here and there +dimly catch a faint ray of light, and we may feel sure that there must +be some cause for each deviation of structure, however slight. + +How much direct effect difference of climate, food, etc., produces on +any being is extremely doubtful. My impression is, that the effect is +extremely small in the case of animals, but perhaps rather more in that +of plants. We may, at least, safely conclude that such influences cannot +have produced the many striking and complex co-adaptations of structure +between one organic being and another, which we see everywhere +throughout nature. Some little influence may be attributed to climate, +food, etc.: thus, E. Forbes speaks confidently that shells at their +southern limit, and when living in shallow water, are more brightly +coloured than those of the same species further north or from greater depths. Gould believes that birds of the same species are more brightly -coloured under a clear atmosphere, than when living on islands or near the -coast. So with insects, Wollaston is convinced that residence near the sea -affects their colours. Moquin-Tandon gives a list of plants which when growing -near the sea-shore have their leaves in some degree fleshy, though not -elsewhere fleshy. Several other such cases could be given. +coloured under a clear atmosphere, than when living on islands or near +the coast. So with insects, Wollaston is convinced that residence near +the sea affects their colours. Moquin-Tandon gives a list of plants +which when growing near the sea-shore have their leaves in some degree +fleshy, though not elsewhere fleshy. Several other such cases could be +given. The fact of varieties of one species, when they range into the zone of -habitation of other species, often acquiring in a very slight degree some of -the characters of such species, accords with our view that species of all kinds -are only well-marked and permanent varieties. Thus the species of shells which -are confined to tropical and shallow seas are generally brighter-coloured than -those confined to cold and deeper seas. The birds which are confined to -continents are, according to Mr. Gould, brighter-coloured than those of -islands. The insect-species confined to sea-coasts, as every collector knows, -are often brassy or lurid. Plants which live exclusively on the sea-side are -very apt to have fleshy leaves. He who believes in the creation of each -species, will have to say that this shell, for instance, was created with -bright colours for a warm sea; but that this other shell became bright-coloured +habitation of other species, often acquiring in a very slight degree +some of the characters of such species, accords with our view that +species of all kinds are only well-marked and permanent varieties. Thus +the species of shells which are confined to tropical and shallow seas +are generally brighter-coloured than those confined to cold and deeper +seas. The birds which are confined to continents are, according to Mr. +Gould, brighter-coloured than those of islands. The insect-species +confined to sea-coasts, as every collector knows, are often brassy or +lurid. Plants which live exclusively on the sea-side are very apt to +have fleshy leaves. He who believes in the creation of each species, +will have to say that this shell, for instance, was created with bright +colours for a warm sea; but that this other shell became bright-coloured by variation when it ranged into warmer or shallower waters. -When a variation is of the slightest use to a being, we cannot tell how much of -it to attribute to the accumulative action of natural selection, and how much -to the conditions of life. Thus, it is well known to furriers that animals of -the same species have thicker and better fur the more severe the climate is -under which they have lived; but who can tell how much of this difference may -be due to the warmest-clad individuals having been favoured and preserved -during many generations, and how much to the direct action of the severe -climate? for it would appear that climate has some direct action on the hair of -our domestic quadrupeds. - -Instances could be given of the same variety being produced under conditions of -life as different as can well be conceived; and, on the other hand, of -different varieties being produced from the same species under the same -conditions. Such facts show how indirectly the conditions of life must act. -Again, innumerable instances are known to every naturalist of species keeping -true, or not varying at all, although living under the most opposite climates. -Such considerations as these incline me to lay very little weight on the direct -action of the conditions of life. Indirectly, as already remarked, they seem to -play an important part in affecting the reproductive system, and in thus -inducing variability; and natural selection will then accumulate all profitable -variations, however slight, until they become plainly developed and appreciable -by us. - -Effects of Use and Disuse.—From the facts alluded to in the first chapter, I -think there can be little doubt that use in our domestic animals strengthens -and enlarges certain parts, and disuse diminishes them; and that such -modifications are inherited. Under free nature, we can have no standard of -comparison, by which to judge of the effects of long-continued use or disuse, -for we know not the parent-forms; but many animals have structures which can be -explained by the effects of disuse. As Professor Owen has remarked, there is no -greater anomaly in nature than a bird that cannot fly; yet there are several in -this state. The logger-headed duck of South America can only flap along the -surface of the water, and has its wings in nearly the same condition as the -domestic Aylesbury duck. As the larger ground-feeding birds seldom take flight -except to escape danger, I believe that the nearly wingless condition of -several birds, which now inhabit or have lately inhabited several oceanic -islands, tenanted by no beast of prey, has been caused by disuse. The ostrich -indeed inhabits continents and is exposed to danger from which it cannot escape -by flight, but by kicking it can defend itself from enemies, as well as any of -the smaller quadrupeds. We may imagine that the early progenitor of the ostrich -had habits like those of a bustard, and that as natural selection increased in -successive generations the size and weight of its body, its legs were used -more, and its wings less, until they became incapable of flight. - -Kirby has remarked (and I have observed the same fact) that the anterior tarsi, -or feet, of many male dung-feeding beetles are very often broken off; he -examined seventeen specimens in his own collection, and not one had even a -relic left. In the Onites apelles the tarsi are so habitually lost, that the -insect has been described as not having them. In some other genera they are -present, but in a rudimentary condition. In the Ateuchus or sacred beetle of -the Egyptians, they are totally deficient. There is not sufficient evidence to -induce us to believe that mutilations are ever inherited; and I should prefer -explaining the entire absence of the anterior tarsi in Ateuchus, and their -rudimentary condition in some other genera, by the long-continued effects of -disuse in their progenitors; for as the tarsi are almost always lost in many -dung-feeding beetles, they must be lost early in life, and therefore cannot be -much used by these insects. - -In some cases we might easily put down to disuse modifications of structure -which are wholly, or mainly, due to natural selection. Mr. Wollaston has -discovered the remarkable fact that 200 beetles, out of the 550 species -inhabiting Madeira, are so far deficient in wings that they cannot fly; and -that of the twenty-nine endemic genera, no less than twenty-three genera have -all their species in this condition! Several facts, namely, that beetles in -many parts of the world are very frequently blown to sea and perish; that the -beetles in Madeira, as observed by Mr. Wollaston, lie much concealed, until the -wind lulls and the sun shines; that the proportion of wingless beetles is -larger on the exposed Dezertas than in Madeira itself; and especially the -extraordinary fact, so strongly insisted on by Mr. Wollaston, of the almost -entire absence of certain large groups of beetles, elsewhere excessively -numerous, and which groups have habits of life almost necessitating frequent -flight;—these several considerations have made me believe that the wingless -condition of so many Madeira beetles is mainly due to the action of natural -selection, but combined probably with disuse. For during thousands of -successive generations each individual beetle which flew least, either from its -wings having been ever so little less perfectly developed or from indolent -habit, will have had the best chance of surviving from not being blown out to -sea; and, on the other hand, those beetles which most readily took to flight -will oftenest have been blown to sea and thus have been destroyed. +When a variation is of the slightest use to a being, we cannot tell how +much of it to attribute to the accumulative action of natural selection, +and how much to the conditions of life. Thus, it is well known to +furriers that animals of the same species have thicker and better fur +the more severe the climate is under which they have lived; but who can +tell how much of this difference may be due to the warmest-clad +individuals having been favoured and preserved during many generations, +and how much to the direct action of the severe climate? for it would +appear that climate has some direct action on the hair of our domestic +quadrupeds. + +Instances could be given of the same variety being produced under +conditions of life as different as can well be conceived; and, on the +other hand, of different varieties being produced from the same species +under the same conditions. Such facts show how indirectly the conditions +of life must act. Again, innumerable instances are known to every +naturalist of species keeping true, or not varying at all, although +living under the most opposite climates. Such considerations as these +incline me to lay very little weight on the direct action of the +conditions of life. Indirectly, as already remarked, they seem to play +an important part in affecting the reproductive system, and in thus +inducing variability; and natural selection will then accumulate all +profitable variations, however slight, until they become plainly +developed and appreciable by us. + +Effects of Use and Disuse.—From the facts alluded to in the first +chapter, I think there can be little doubt that use in our domestic +animals strengthens and enlarges certain parts, and disuse diminishes +them; and that such modifications are inherited. Under free nature, we +can have no standard of comparison, by which to judge of the effects of +long-continued use or disuse, for we know not the parent-forms; but many +animals have structures which can be explained by the effects of disuse. +As Professor Owen has remarked, there is no greater anomaly in nature +than a bird that cannot fly; yet there are several in this state. The +logger-headed duck of South America can only flap along the surface of +the water, and has its wings in nearly the same condition as the +domestic Aylesbury duck. As the larger ground-feeding birds seldom take +flight except to escape danger, I believe that the nearly wingless +condition of several birds, which now inhabit or have lately inhabited +several oceanic islands, tenanted by no beast of prey, has been caused +by disuse. The ostrich indeed inhabits continents and is exposed to +danger from which it cannot escape by flight, but by kicking it can +defend itself from enemies, as well as any of the smaller quadrupeds. We +may imagine that the early progenitor of the ostrich had habits like +those of a bustard, and that as natural selection increased in +successive generations the size and weight of its body, its legs were +used more, and its wings less, until they became incapable of flight. + +Kirby has remarked (and I have observed the same fact) that the anterior +tarsi, or feet, of many male dung-feeding beetles are very often broken +off; he examined seventeen specimens in his own collection, and not one +had even a relic left. In the Onites apelles the tarsi are so habitually +lost, that the insect has been described as not having them. In some +other genera they are present, but in a rudimentary condition. In the +Ateuchus or sacred beetle of the Egyptians, they are totally deficient. +There is not sufficient evidence to induce us to believe that +mutilations are ever inherited; and I should prefer explaining the +entire absence of the anterior tarsi in Ateuchus, and their rudimentary +condition in some other genera, by the long-continued effects of disuse +in their progenitors; for as the tarsi are almost always lost in many +dung-feeding beetles, they must be lost early in life, and therefore +cannot be much used by these insects. + +In some cases we might easily put down to disuse modifications of +structure which are wholly, or mainly, due to natural selection. Mr. +Wollaston has discovered the remarkable fact that 200 beetles, out of +the 550 species inhabiting Madeira, are so far deficient in wings that +they cannot fly; and that of the twenty-nine endemic genera, no less +than twenty-three genera have all their species in this condition! +Several facts, namely, that beetles in many parts of the world are very +frequently blown to sea and perish; that the beetles in Madeira, as +observed by Mr. Wollaston, lie much concealed, until the wind lulls and +the sun shines; that the proportion of wingless beetles is larger on the +exposed Dezertas than in Madeira itself; and especially the +extraordinary fact, so strongly insisted on by Mr. Wollaston, of the +almost entire absence of certain large groups of beetles, elsewhere +excessively numerous, and which groups have habits of life almost +necessitating frequent flight;—these several considerations have made me +believe that the wingless condition of so many Madeira beetles is mainly +due to the action of natural selection, but combined probably with +disuse. For during thousands of successive generations each individual +beetle which flew least, either from its wings having been ever so +little less perfectly developed or from indolent habit, will have had +the best chance of surviving from not being blown out to sea; and, on +the other hand, those beetles which most readily took to flight will +oftenest have been blown to sea and thus have been destroyed. The insects in Madeira which are not ground-feeders, and which, as the -flower-feeding coleoptera and lepidoptera, must habitually use their wings to -gain their subsistence, have, as Mr. Wollaston suspects, their wings not at all -reduced, but even enlarged. This is quite compatible with the action of natural -selection. For when a new insect first arrived on the island, the tendency of -natural selection to enlarge or to reduce the wings, would depend on whether a -greater number of individuals were saved by successfully battling with the -winds, or by giving up the attempt and rarely or never flying. As with mariners -shipwrecked near a coast, it would have been better for the good swimmers if -they had been able to swim still further, whereas it would have been better for -the bad swimmers if they had not been able to swim at all and had stuck to the -wreck. - -The eyes of moles and of some burrowing rodents are rudimentary in size, and in -some cases are quite covered up by skin and fur. This state of the eyes is -probably due to gradual reduction from disuse, but aided perhaps by natural -selection. In South America, a burrowing rodent, the tuco-tuco, or Ctenomys, is -even more subterranean in its habits than the mole; and I was assured by a -Spaniard, who had often caught them, that they were frequently blind; one which -I kept alive was certainly in this condition, the cause, as appeared on -dissection, having been inflammation of the nictitating membrane. As frequent -inflammation of the eyes must be injurious to any animal, and as eyes are -certainly not indispensable to animals with subterranean habits, a reduction in -their size with the adhesion of the eyelids and growth of fur over them, might -in such case be an advantage; and if so, natural selection would constantly aid -the effects of disuse. - -It is well known that several animals, belonging to the most different classes, -which inhabit the caves of Styria and of Kentucky, are blind. In some of the -crabs the foot-stalk for the eye remains, though the eye is gone; the stand for -the telescope is there, though the telescope with its glasses has been lost. As -it is difficult to imagine that eyes, though useless, could be in any way -injurious to animals living in darkness, I attribute their loss wholly to -disuse. In one of the blind animals, namely, the cave-rat, the eyes are of -immense size; and Professor Silliman thought that it regained, after living -some days in the light, some slight power of vision. In the same manner as in -Madeira the wings of some of the insects have been enlarged, and the wings of -others have been reduced by natural selection aided by use and disuse, so in -the case of the cave-rat natural selection seems to have struggled with the -loss of light and to have increased the size of the eyes; whereas with all the -other inhabitants of the caves, disuse by itself seems to have done its work. - -It is difficult to imagine conditions of life more similar than deep limestone -caverns under a nearly similar climate; so that on the common view of the blind -animals having been separately created for the American and European caverns, -close similarity in their organisation and affinities might have been expected; -but, as Schiödte and others have remarked, this is not the case, and the -cave-insects of the two continents are not more closely allied than might have -been anticipated from the general resemblance of the other inhabitants of North -America and Europe. On my view we must suppose that American animals, having -ordinary powers of vision, slowly migrated by successive generations from the -outer world into the deeper and deeper recesses of the Kentucky caves, as did -European animals into the caves of Europe. We have some evidence of this -gradation of habit; for, as Schiödte remarks, “animals not far remote from -ordinary forms, prepare the transition from light to darkness. Next follow -those that are constructed for twilight; and, last of all, those destined for -total darkness.” By the time that an animal had reached, after numberless -generations, the deepest recesses, disuse will on this view have more or less -perfectly obliterated its eyes, and natural selection will often have effected -other changes, such as an increase in the length of the antennæ or palpi, as a -compensation for blindness. Notwithstanding such modifications, we might expect -still to see in the cave-animals of America, affinities to the other -inhabitants of that continent, and in those of Europe, to the inhabitants of -the European continent. And this is the case with some of the American +flower-feeding coleoptera and lepidoptera, must habitually use their +wings to gain their subsistence, have, as Mr. Wollaston suspects, their +wings not at all reduced, but even enlarged. This is quite compatible +with the action of natural selection. For when a new insect first +arrived on the island, the tendency of natural selection to enlarge or +to reduce the wings, would depend on whether a greater number of +individuals were saved by successfully battling with the winds, or by +giving up the attempt and rarely or never flying. As with mariners +shipwrecked near a coast, it would have been better for the good +swimmers if they had been able to swim still further, whereas it would +have been better for the bad swimmers if they had not been able to swim +at all and had stuck to the wreck. + +The eyes of moles and of some burrowing rodents are rudimentary in size, +and in some cases are quite covered up by skin and fur. This state of +the eyes is probably due to gradual reduction from disuse, but aided +perhaps by natural selection. In South America, a burrowing rodent, the +tuco-tuco, or Ctenomys, is even more subterranean in its habits than the +mole; and I was assured by a Spaniard, who had often caught them, that +they were frequently blind; one which I kept alive was certainly in this +condition, the cause, as appeared on dissection, having been +inflammation of the nictitating membrane. As frequent inflammation of +the eyes must be injurious to any animal, and as eyes are certainly not +indispensable to animals with subterranean habits, a reduction in their +size with the adhesion of the eyelids and growth of fur over them, might +in such case be an advantage; and if so, natural selection would +constantly aid the effects of disuse. + +It is well known that several animals, belonging to the most different +classes, which inhabit the caves of Styria and of Kentucky, are blind. +In some of the crabs the foot-stalk for the eye remains, though the eye +is gone; the stand for the telescope is there, though the telescope with +its glasses has been lost. As it is difficult to imagine that eyes, +though useless, could be in any way injurious to animals living in +darkness, I attribute their loss wholly to disuse. In one of the blind +animals, namely, the cave-rat, the eyes are of immense size; and +Professor Silliman thought that it regained, after living some days in +the light, some slight power of vision. In the same manner as in Madeira +the wings of some of the insects have been enlarged, and the wings of +others have been reduced by natural selection aided by use and disuse, +so in the case of the cave-rat natural selection seems to have struggled +with the loss of light and to have increased the size of the eyes; +whereas with all the other inhabitants of the caves, disuse by itself +seems to have done its work. + +It is difficult to imagine conditions of life more similar than deep +limestone caverns under a nearly similar climate; so that on the common +view of the blind animals having been separately created for the +American and European caverns, close similarity in their organisation +and affinities might have been expected; but, as Schiödte and others +have remarked, this is not the case, and the cave-insects of the two +continents are not more closely allied than might have been anticipated +from the general resemblance of the other inhabitants of North America +and Europe. On my view we must suppose that American animals, having +ordinary powers of vision, slowly migrated by successive generations +from the outer world into the deeper and deeper recesses of the Kentucky +caves, as did European animals into the caves of Europe. We have some +evidence of this gradation of habit; for, as Schiödte remarks, “animals +not far remote from ordinary forms, prepare the transition from light to +darkness. Next follow those that are constructed for twilight; and, last +of all, those destined for total darkness.” By the time that an animal +had reached, after numberless generations, the deepest recesses, disuse +will on this view have more or less perfectly obliterated its eyes, and +natural selection will often have effected other changes, such as an +increase in the length of the antennæ or palpi, as a compensation for +blindness. Notwithstanding such modifications, we might expect still to +see in the cave-animals of America, affinities to the other inhabitants +of that continent, and in those of Europe, to the inhabitants of the +European continent. And this is the case with some of the American cave-animals, as I hear from Professor Dana; and some of the European -cave-insects are very closely allied to those of the surrounding country. It -would be most difficult to give any rational explanation of the affinities of -the blind cave-animals to the other inhabitants of the two continents on the -ordinary view of their independent creation. That several of the inhabitants of -the caves of the Old and New Worlds should be closely related, we might expect -from the well-known relationship of most of their other productions. Far from -feeling any surprise that some of the cave-animals should be very anomalous, as -Agassiz has remarked in regard to the blind fish, the Amblyopsis, and as is the -case with the blind Proteus with reference to the reptiles of Europe, I am only -surprised that more wrecks of ancient life have not been preserved, owing to -the less severe competition to which the inhabitants of these dark abodes will -probably have been exposed. +cave-insects are very closely allied to those of the surrounding +country. It would be most difficult to give any rational explanation of +the affinities of the blind cave-animals to the other inhabitants of the +two continents on the ordinary view of their independent creation. That +several of the inhabitants of the caves of the Old and New Worlds should +be closely related, we might expect from the well-known relationship of +most of their other productions. Far from feeling any surprise that some +of the cave-animals should be very anomalous, as Agassiz has remarked in +regard to the blind fish, the Amblyopsis, and as is the case with the +blind Proteus with reference to the reptiles of Europe, I am only +surprised that more wrecks of ancient life have not been preserved, +owing to the less severe competition to which the inhabitants of these +dark abodes will probably have been exposed. Acclimatisation.—Habit is hereditary with plants, as in the period of -flowering, in the amount of rain requisite for seeds to germinate, in the time -of sleep, etc., and this leads me to say a few words on acclimatisation. As it -is extremely common for species of the same genus to inhabit very hot and very -cold countries, and as I believe that all the species of the same genus have -descended from a single parent, if this view be correct, acclimatisation must -be readily effected during long-continued descent. It is notorious that each -species is adapted to the climate of its own home: species from an arctic or -even from a temperate region cannot endure a tropical climate, or conversely. -So again, many succulent plants cannot endure a damp climate. But the degree of -adaptation of species to the climates under which they live is often overrated. -We may infer this from our frequent inability to predict whether or not an -imported plant will endure our climate, and from the number of plants and -animals brought from warmer countries which here enjoy good health. We have -reason to believe that species in a state of nature are limited in their ranges -by the competition of other organic beings quite as much as, or more than, by -adaptation to particular climates. But whether or not the adaptation be -generally very close, we have evidence, in the case of some few plants, of -their becoming, to a certain extent, naturally habituated to different -temperatures, or becoming acclimatised: thus the pines and rhododendrons, -raised from seed collected by Dr. Hooker from trees growing at different -heights on the Himalaya, were found in this country to possess different -constitutional powers of resisting cold. Mr. Thwaites informs me that he has -observed similar facts in Ceylon, and analogous observations have been made by -Mr. H. C. Watson on European species of plants brought from the Azores to -England. In regard to animals, several authentic cases could be given of -species within historical times having largely extended their range from warmer -to cooler latitudes, and conversely; but we do not positively know that these -animals were strictly adapted to their native climate, but in all ordinary -cases we assume such to be the case; nor do we know that they have subsequently -become acclimatised to their new homes. - -As I believe that our domestic animals were originally chosen by uncivilised -man because they were useful and bred readily under confinement, and not -because they were subsequently found capable of far-extended transportation, I -think the common and extraordinary capacity in our domestic animals of not only -withstanding the most different climates but of being perfectly fertile (a far -severer test) under them, may be used as an argument that a large proportion of -other animals, now in a state of nature, could easily be brought to bear widely -different climates. We must not, however, push the foregoing argument too far, -on account of the probable origin of some of our domestic animals from several -wild stocks: the blood, for instance, of a tropical and arctic wolf or wild dog -may perhaps be mingled in our domestic breeds. The rat and mouse cannot be -considered as domestic animals, but they have been transported by man to many -parts of the world, and now have a far wider range than any other rodent, -living free under the cold climate of Faroe in the north and of the Falklands -in the south, and on many islands in the torrid zones. Hence I am inclined to -look at adaptation to any special climate as a quality readily grafted on an -innate wide flexibility of constitution, which is common to most animals. On -this view, the capacity of enduring the most different climates by man himself -and by his domestic animals, and such facts as that former species of the -elephant and rhinoceros were capable of enduring a glacial climate, whereas the -living species are now all tropical or sub-tropical in their habits, ought not -to be looked at as anomalies, but merely as examples of a very common -flexibility of constitution, brought, under peculiar circumstances, into play. - -How much of the acclimatisation of species to any peculiar climate is due to -mere habit, and how much to the natural selection of varieties having different -innate constitutions, and how much to both means combined, is a very obscure -question. That habit or custom has some influence I must believe, both from -analogy, and from the incessant advice given in agricultural works, even in the -ancient Encyclopædias of China, to be very cautious in transposing animals from -one district to another; for it is not likely that man should have succeeded in -selecting so many breeds and sub-breeds with constitutions specially fitted for -their own districts: the result must, I think, be due to habit. On the other -hand, I can see no reason to doubt that natural selection will continually tend -to preserve those individuals which are born with constitutions best adapted to -their native countries. In treatises on many kinds of cultivated plants, -certain varieties are said to withstand certain climates better than others: -this is very strikingly shown in works on fruit trees published in the United -States, in which certain varieties are habitually recommended for the northern, -and others for the southern States; and as most of these varieties are of -recent origin, they cannot owe their constitutional differences to habit. The -case of the Jerusalem artichoke, which is never propagated by seed, and of -which consequently new varieties have not been produced, has even been -advanced—for it is now as tender as ever it was—as proving that acclimatisation -cannot be effected! The case, also, of the kidney-bean has been often cited for -a similar purpose, and with much greater weight; but until some one will sow, -during a score of generations, his kidney-beans so early that a very large -proportion are destroyed by frost, and then collect seed from the few -survivors, with care to prevent accidental crosses, and then again get seed -from these seedlings, with the same precautions, the experiment cannot be said -to have been even tried. Nor let it be supposed that no differences in the -constitution of seedling kidney-beans ever appear, for an account has been -published how much more hardy some seedlings appeared to be than others. - -On the whole, I think we may conclude that habit, use, and disuse, have, in -some cases, played a considerable part in the modification of the constitution, -and of the structure of various organs; but that the effects of use and disuse -have often been largely combined with, and sometimes overmastered by, the -natural selection of innate differences. - -Correlation of Growth.—I mean by this expression that the whole organisation is -so tied together during its growth and development, that when slight variations -in any one part occur, and are accumulated through natural selection, other -parts become modified. This is a very important subject, most imperfectly -understood. The most obvious case is, that modifications accumulated solely for -the good of the young or larva, will, it may safely be concluded, affect the -structure of the adult; in the same manner as any malconformation affecting the -early embryo, seriously affects the whole organisation of the adult. The +flowering, in the amount of rain requisite for seeds to germinate, in +the time of sleep, etc., and this leads me to say a few words on +acclimatisation. As it is extremely common for species of the same genus +to inhabit very hot and very cold countries, and as I believe that all +the species of the same genus have descended from a single parent, if +this view be correct, acclimatisation must be readily effected during +long-continued descent. It is notorious that each species is adapted to +the climate of its own home: species from an arctic or even from a +temperate region cannot endure a tropical climate, or conversely. So +again, many succulent plants cannot endure a damp climate. But the +degree of adaptation of species to the climates under which they live is +often overrated. We may infer this from our frequent inability to +predict whether or not an imported plant will endure our climate, and +from the number of plants and animals brought from warmer countries +which here enjoy good health. We have reason to believe that species in +a state of nature are limited in their ranges by the competition of +other organic beings quite as much as, or more than, by adaptation to +particular climates. But whether or not the adaptation be generally very +close, we have evidence, in the case of some few plants, of their +becoming, to a certain extent, naturally habituated to different +temperatures, or becoming acclimatised: thus the pines and +rhododendrons, raised from seed collected by Dr. Hooker from trees +growing at different heights on the Himalaya, were found in this country +to possess different constitutional powers of resisting cold. Mr. +Thwaites informs me that he has observed similar facts in Ceylon, and +analogous observations have been made by Mr. H. C. Watson on European +species of plants brought from the Azores to England. In regard to +animals, several authentic cases could be given of species within +historical times having largely extended their range from warmer to +cooler latitudes, and conversely; but we do not positively know that +these animals were strictly adapted to their native climate, but in all +ordinary cases we assume such to be the case; nor do we know that they +have subsequently become acclimatised to their new homes. + +As I believe that our domestic animals were originally chosen by +uncivilised man because they were useful and bred readily under +confinement, and not because they were subsequently found capable of +far-extended transportation, I think the common and extraordinary +capacity in our domestic animals of not only withstanding the most +different climates but of being perfectly fertile (a far severer test) +under them, may be used as an argument that a large proportion of other +animals, now in a state of nature, could easily be brought to bear +widely different climates. We must not, however, push the foregoing +argument too far, on account of the probable origin of some of our +domestic animals from several wild stocks: the blood, for instance, of a +tropical and arctic wolf or wild dog may perhaps be mingled in our +domestic breeds. The rat and mouse cannot be considered as domestic +animals, but they have been transported by man to many parts of the +world, and now have a far wider range than any other rodent, living free +under the cold climate of Faroe in the north and of the Falklands in the +south, and on many islands in the torrid zones. Hence I am inclined to +look at adaptation to any special climate as a quality readily grafted +on an innate wide flexibility of constitution, which is common to most +animals. On this view, the capacity of enduring the most different +climates by man himself and by his domestic animals, and such facts as +that former species of the elephant and rhinoceros were capable of +enduring a glacial climate, whereas the living species are now all +tropical or sub-tropical in their habits, ought not to be looked at as +anomalies, but merely as examples of a very common flexibility of +constitution, brought, under peculiar circumstances, into play. + +How much of the acclimatisation of species to any peculiar climate is +due to mere habit, and how much to the natural selection of varieties +having different innate constitutions, and how much to both means +combined, is a very obscure question. That habit or custom has some +influence I must believe, both from analogy, and from the incessant +advice given in agricultural works, even in the ancient Encyclopædias of +China, to be very cautious in transposing animals from one district to +another; for it is not likely that man should have succeeded in +selecting so many breeds and sub-breeds with constitutions specially +fitted for their own districts: the result must, I think, be due to +habit. On the other hand, I can see no reason to doubt that natural +selection will continually tend to preserve those individuals which are +born with constitutions best adapted to their native countries. In +treatises on many kinds of cultivated plants, certain varieties are said +to withstand certain climates better than others: this is very +strikingly shown in works on fruit trees published in the United States, +in which certain varieties are habitually recommended for the northern, +and others for the southern States; and as most of these varieties are +of recent origin, they cannot owe their constitutional differences to +habit. The case of the Jerusalem artichoke, which is never propagated by +seed, and of which consequently new varieties have not been produced, +has even been advanced—for it is now as tender as ever it was—as proving +that acclimatisation cannot be effected! The case, also, of the +kidney-bean has been often cited for a similar purpose, and with much +greater weight; but until some one will sow, during a score of +generations, his kidney-beans so early that a very large proportion are +destroyed by frost, and then collect seed from the few survivors, with +care to prevent accidental crosses, and then again get seed from these +seedlings, with the same precautions, the experiment cannot be said to +have been even tried. Nor let it be supposed that no differences in the +constitution of seedling kidney-beans ever appear, for an account has +been published how much more hardy some seedlings appeared to be than +others. + +On the whole, I think we may conclude that habit, use, and disuse, have, +in some cases, played a considerable part in the modification of the +constitution, and of the structure of various organs; but that the +effects of use and disuse have often been largely combined with, and +sometimes overmastered by, the natural selection of innate differences. + +Correlation of Growth.—I mean by this expression that the whole +organisation is so tied together during its growth and development, that +when slight variations in any one part occur, and are accumulated +through natural selection, other parts become modified. This is a very +important subject, most imperfectly understood. The most obvious case +is, that modifications accumulated solely for the good of the young or +larva, will, it may safely be concluded, affect the structure of the +adult; in the same manner as any malconformation affecting the early +embryo, seriously affects the whole organisation of the adult. The several parts of the body which are homologous, and which, at an early -embryonic period, are alike, seem liable to vary in an allied manner: we see -this in the right and left sides of the body varying in the same manner; in the -front and hind legs, and even in the jaws and limbs, varying together, for the -lower jaw is believed to be homologous with the limbs. These tendencies, I do -not doubt, may be mastered more or less completely by natural selection: thus a -family of stags once existed with an antler only on one side; and if this had -been of any great use to the breed it might probably have been rendered -permanent by natural selection. - -Homologous parts, as has been remarked by some authors, tend to cohere; this is -often seen in monstrous plants; and nothing is more common than the union of -homologous parts in normal structures, as the union of the petals of the -corolla into a tube. Hard parts seem to affect the form of adjoining soft -parts; it is believed by some authors that the diversity in the shape of the -pelvis in birds causes the remarkable diversity in the shape of their kidneys. -Others believe that the shape of the pelvis in the human mother influences by -pressure the shape of the head of the child. In snakes, according to Schlegel, -the shape of the body and the manner of swallowing determine the position of -several of the most important viscera. - -The nature of the bond of correlation is very frequently quite obscure. M. Is. -Geoffroy St. Hilaire has forcibly remarked, that certain malconformations very -frequently, and that others rarely coexist, without our being able to assign -any reason. What can be more singular than the relation between blue eyes and -deafness in cats, and the tortoise-shell colour with the female sex; the -feathered feet and skin between the outer toes in pigeons, and the presence of -more or less down on the young birds when first hatched, with the future colour -of their plumage; or, again, the relation between the hair and teeth in the -naked Turkish dog, though here probably homology comes into play? With respect -to this latter case of correlation, I think it can hardly be accidental, that -if we pick out the two orders of mammalia which are most abnormal in their -dermal coverings, viz. Cetacea (whales) and Edentata (armadilloes, scaly -ant-eaters, etc.), that these are likewise the most abnormal in their teeth. +embryonic period, are alike, seem liable to vary in an allied manner: we +see this in the right and left sides of the body varying in the same +manner; in the front and hind legs, and even in the jaws and limbs, +varying together, for the lower jaw is believed to be homologous with +the limbs. These tendencies, I do not doubt, may be mastered more or +less completely by natural selection: thus a family of stags once +existed with an antler only on one side; and if this had been of any +great use to the breed it might probably have been rendered permanent by +natural selection. + +Homologous parts, as has been remarked by some authors, tend to cohere; +this is often seen in monstrous plants; and nothing is more common than +the union of homologous parts in normal structures, as the union of the +petals of the corolla into a tube. Hard parts seem to affect the form of +adjoining soft parts; it is believed by some authors that the diversity +in the shape of the pelvis in birds causes the remarkable diversity in +the shape of their kidneys. Others believe that the shape of the pelvis +in the human mother influences by pressure the shape of the head of the +child. In snakes, according to Schlegel, the shape of the body and the +manner of swallowing determine the position of several of the most +important viscera. + +The nature of the bond of correlation is very frequently quite obscure. +M. Is. Geoffroy St. Hilaire has forcibly remarked, that certain +malconformations very frequently, and that others rarely coexist, +without our being able to assign any reason. What can be more singular +than the relation between blue eyes and deafness in cats, and the +tortoise-shell colour with the female sex; the feathered feet and skin +between the outer toes in pigeons, and the presence of more or less down +on the young birds when first hatched, with the future colour of their +plumage; or, again, the relation between the hair and teeth in the naked +Turkish dog, though here probably homology comes into play? With respect +to this latter case of correlation, I think it can hardly be accidental, +that if we pick out the two orders of mammalia which are most abnormal +in their dermal coverings, viz. Cetacea (whales) and Edentata +(armadilloes, scaly ant-eaters, etc.), that these are likewise the most +abnormal in their teeth. I know of no case better adapted to show the importance of the laws of -correlation in modifying important structures, independently of utility and, -therefore, of natural selection, than that of the difference between the outer -and inner flowers in some Compositous and Umbelliferous plants. Every one knows -the difference in the ray and central florets of, for instance, the daisy, and -this difference is often accompanied with the abortion of parts of the flower. -But, in some Compositous plants, the seeds also differ in shape and sculpture; -and even the ovary itself, with its accessory parts, differs, as has been -described by Cassini. These differences have been attributed by some authors to -pressure, and the shape of the seeds in the ray-florets in some Compositæ -countenances this idea; but, in the case of the corolla of the Umbelliferæ, it -is by no means, as Dr. Hooker informs me, in species with the densest heads -that the inner and outer flowers most frequently differ. It might have been -thought that the development of the ray-petals by drawing nourishment from -certain other parts of the flower had caused their abortion; but in some -Compositæ there is a difference in the seeds of the outer and inner florets -without any difference in the corolla. Possibly, these several differences may -be connected with some difference in the flow of nutriment towards the central -and external flowers: we know, at least, that in irregular flowers, those -nearest to the axis are oftenest subject to peloria, and become regular. I may -add, as an instance of this, and of a striking case of correlation, that I have -recently observed in some garden pelargoniums, that the central flower of the -truss often loses the patches of darker colour in the two upper petals; and -that when this occurs, the adherent nectary is quite aborted; when the colour -is absent from only one of the two upper petals, the nectary is only much +correlation in modifying important structures, independently of utility +and, therefore, of natural selection, than that of the difference +between the outer and inner flowers in some Compositous and +Umbelliferous plants. Every one knows the difference in the ray and +central florets of, for instance, the daisy, and this difference is +often accompanied with the abortion of parts of the flower. But, in +some Compositous plants, the seeds also differ in shape and sculpture; +and even the ovary itself, with its accessory parts, differs, as has +been described by Cassini. These differences have been attributed by +some authors to pressure, and the shape of the seeds in the ray-florets +in some Compositæ countenances this idea; but, in the case of the +corolla of the Umbelliferæ, it is by no means, as Dr. Hooker informs me, +in species with the densest heads that the inner and outer flowers most +frequently differ. It might have been thought that the development of +the ray-petals by drawing nourishment from certain other parts of the +flower had caused their abortion; but in some Compositæ there is a +difference in the seeds of the outer and inner florets without any +difference in the corolla. Possibly, these several differences may be +connected with some difference in the flow of nutriment towards the +central and external flowers: we know, at least, that in irregular +flowers, those nearest to the axis are oftenest subject to peloria, and +become regular. I may add, as an instance of this, and of a striking +case of correlation, that I have recently observed in some garden +pelargoniums, that the central flower of the truss often loses the +patches of darker colour in the two upper petals; and that when this +occurs, the adherent nectary is quite aborted; when the colour is absent +from only one of the two upper petals, the nectary is only much shortened. -With respect to the difference in the corolla of the central and exterior -flowers of a head or umbel, I do not feel at all sure that C. C. Sprengel’s -idea that the ray-florets serve to attract insects, whose agency is highly -advantageous in the fertilisation of plants of these two orders, is so -far-fetched, as it may at first appear: and if it be advantageous, natural -selection may have come into play. But in regard to the differences both in the -internal and external structure of the seeds, which are not always correlated -with any differences in the flowers, it seems impossible that they can be in -any way advantageous to the plant: yet in the Umbelliferæ these differences are -of such apparent importance—the seeds being in some cases, according to Tausch, +With respect to the difference in the corolla of the central and +exterior flowers of a head or umbel, I do not feel at all sure that C. +C. Sprengel’s idea that the ray-florets serve to attract insects, whose +agency is highly advantageous in the fertilisation of plants of these +two orders, is so far-fetched, as it may at first appear: and if it be +advantageous, natural selection may have come into play. But in regard +to the differences both in the internal and external structure of the +seeds, which are not always correlated with any differences in the +flowers, it seems impossible that they can be in any way advantageous to +the plant: yet in the Umbelliferæ these differences are of such apparent +importance—the seeds being in some cases, according to Tausch, orthospermous in the exterior flowers and coelospermous in the central -flowers,—that the elder De Candolle founded his main divisions of the order on -analogous differences. Hence we see that modifications of structure, viewed by -systematists as of high value, may be wholly due to unknown laws of correlated -growth, and without being, as far as we can see, of the slightest service to -the species. - -We may often falsely attribute to correlation of growth, structures which are -common to whole groups of species, and which in truth are simply due to -inheritance; for an ancient progenitor may have acquired through natural -selection some one modification in structure, and, after thousands of -generations, some other and independent modification; and these two -modifications, having been transmitted to a whole group of descendants with -diverse habits, would naturally be thought to be correlated in some necessary -manner. So, again, I do not doubt that some apparent correlations, occurring -throughout whole orders, are entirely due to the manner alone in which natural -selection can act. For instance, Alph. De Candolle has remarked that winged -seeds are never found in fruits which do not open: I should explain the rule by -the fact that seeds could not gradually become winged through natural -selection, except in fruits which opened; so that the individual plants -producing seeds which were a little better fitted to be wafted further, might -get an advantage over those producing seed less fitted for dispersal; and this -process could not possibly go on in fruit which did not open. - -The elder Geoffroy and Goethe propounded, at about the same period, their law -of compensation or balancement of growth; or, as Goethe expressed it, “in order -to spend on one side, nature is forced to economise on the other side.” I think -this holds true to a certain extent with our domestic productions: if -nourishment flows to one part or organ in excess, it rarely flows, at least in -excess, to another part; thus it is difficult to get a cow to give much milk -and to fatten readily. The same varieties of the cabbage do not yield abundant -and nutritious foliage and a copious supply of oil-bearing seeds. When the -seeds in our fruits become atrophied, the fruit itself gains largely in size -and quality. In our poultry, a large tuft of feathers on the head is generally -accompanied by a diminished comb, and a large beard by diminished wattles. With -species in a state of nature it can hardly be maintained that the law is of -universal application; but many good observers, more especially botanists, -believe in its truth. I will not, however, here give any instances, for I see -hardly any way of distinguishing between the effects, on the one hand, of a -part being largely developed through natural selection and another and -adjoining part being reduced by this same process or by disuse, and, on the -other hand, the actual withdrawal of nutriment from one part owing to the +flowers,—that the elder De Candolle founded his main divisions of the +order on analogous differences. Hence we see that modifications of +structure, viewed by systematists as of high value, may be wholly due to +unknown laws of correlated growth, and without being, as far as we can +see, of the slightest service to the species. + +We may often falsely attribute to correlation of growth, structures +which are common to whole groups of species, and which in truth are +simply due to inheritance; for an ancient progenitor may have acquired +through natural selection some one modification in structure, and, after +thousands of generations, some other and independent modification; and +these two modifications, having been transmitted to a whole group of +descendants with diverse habits, would naturally be thought to be +correlated in some necessary manner. So, again, I do not doubt that some +apparent correlations, occurring throughout whole orders, are entirely +due to the manner alone in which natural selection can act. For +instance, Alph. De Candolle has remarked that winged seeds are never +found in fruits which do not open: I should explain the rule by the fact +that seeds could not gradually become winged through natural selection, +except in fruits which opened; so that the individual plants producing +seeds which were a little better fitted to be wafted further, might get +an advantage over those producing seed less fitted for dispersal; and +this process could not possibly go on in fruit which did not open. + +The elder Geoffroy and Goethe propounded, at about the same period, +their law of compensation or balancement of growth; or, as Goethe +expressed it, “in order to spend on one side, nature is forced to +economise on the other side.” I think this holds true to a certain +extent with our domestic productions: if nourishment flows to one part +or organ in excess, it rarely flows, at least in excess, to another +part; thus it is difficult to get a cow to give much milk and to fatten +readily. The same varieties of the cabbage do not yield abundant and +nutritious foliage and a copious supply of oil-bearing seeds. When the +seeds in our fruits become atrophied, the fruit itself gains largely in +size and quality. In our poultry, a large tuft of feathers on the head +is generally accompanied by a diminished comb, and a large beard by +diminished wattles. With species in a state of nature it can hardly be +maintained that the law is of universal application; but many good +observers, more especially botanists, believe in its truth. I will not, +however, here give any instances, for I see hardly any way of +distinguishing between the effects, on the one hand, of a part being +largely developed through natural selection and another and adjoining +part being reduced by this same process or by disuse, and, on the other +hand, the actual withdrawal of nutriment from one part owing to the excess of growth in another and adjoining part. I suspect, also, that some of the cases of compensation which have been -advanced, and likewise some other facts, may be merged under a more general -principle, namely, that natural selection is continually trying to economise in -every part of the organisation. If under changed conditions of life a structure -before useful becomes less useful, any diminution, however slight, in its -development, will be seized on by natural selection, for it will profit the -individual not to have its nutriment wasted in building up an useless -structure. I can thus only understand a fact with which I was much struck when -examining cirripedes, and of which many other instances could be given: namely, -that when a cirripede is parasitic within another and is thus protected, it -loses more or less completely its own shell or carapace. This is the case with -the male Ibla, and in a truly extraordinary manner with the Proteolepas: for -the carapace in all other cirripedes consists of the three highly-important -anterior segments of the head enormously developed, and furnished with great -nerves and muscles; but in the parasitic and protected Proteolepas, the whole -anterior part of the head is reduced to the merest rudiment attached to the -bases of the prehensile antennæ. Now the saving of a large and complex -structure, when rendered superfluous by the parasitic habits of the -Proteolepas, though effected by slow steps, would be a decided advantage to -each successive individual of the species; for in the struggle for life to -which every animal is exposed, each individual Proteolepas would have a better -chance of supporting itself, by less nutriment being wasted in developing a -structure now become useless. - -Thus, as I believe, natural selection will always succeed in the long run in -reducing and saving every part of the organisation, as soon as it is rendered -superfluous, without by any means causing some other part to be largely -developed in a corresponding degree. And, conversely, that natural selection -may perfectly well succeed in largely developing any organ, without requiring -as a necessary compensation the reduction of some adjoining part. +advanced, and likewise some other facts, may be merged under a more +general principle, namely, that natural selection is continually trying +to economise in every part of the organisation. If under changed +conditions of life a structure before useful becomes less useful, any +diminution, however slight, in its development, will be seized on by +natural selection, for it will profit the individual not to have its +nutriment wasted in building up an useless structure. I can thus only +understand a fact with which I was much struck when examining +cirripedes, and of which many other instances could be given: namely, +that when a cirripede is parasitic within another and is thus protected, +it loses more or less completely its own shell or carapace. This is the +case with the male Ibla, and in a truly extraordinary manner with the +Proteolepas: for the carapace in all other cirripedes consists of the +three highly-important anterior segments of the head enormously +developed, and furnished with great nerves and muscles; but in the +parasitic and protected Proteolepas, the whole anterior part of the head +is reduced to the merest rudiment attached to the bases of the +prehensile antennæ. Now the saving of a large and complex structure, +when rendered superfluous by the parasitic habits of the Proteolepas, +though effected by slow steps, would be a decided advantage to each +successive individual of the species; for in the struggle for life to +which every animal is exposed, each individual Proteolepas would have a +better chance of supporting itself, by less nutriment being wasted in +developing a structure now become useless. + +Thus, as I believe, natural selection will always succeed in the long +run in reducing and saving every part of the organisation, as soon as it +is rendered superfluous, without by any means causing some other part to +be largely developed in a corresponding degree. And, conversely, that +natural selection may perfectly well succeed in largely developing any +organ, without requiring as a necessary compensation the reduction of +some adjoining part. It seems to be a rule, as remarked by Is. Geoffroy St. Hilaire, both in -varieties and in species, that when any part or organ is repeated many times in -the structure of the same individual (as the vertebræ in snakes, and the -stamens in polyandrous flowers) the number is variable; whereas the number of -the same part or organ, when it occurs in lesser numbers, is constant. The same -author and some botanists have further remarked that multiple parts are also -very liable to variation in structure. Inasmuch as this “vegetative -repetition,” to use Professor Owen’s expression, seems to be a sign of low -organisation; the foregoing remark seems connected with the very general -opinion of naturalists, that beings low in the scale of nature are more -variable than those which are higher. I presume that lowness in this case means -that the several parts of the organisation have been but little specialised for -particular functions; and as long as the same part has to perform diversified -work, we can perhaps see why it should remain variable, that is, why natural -selection should have preserved or rejected each little deviation of form less -carefully than when the part has to serve for one special purpose alone. In the -same way that a knife which has to cut all sorts of things may be of almost any -shape; whilst a tool for some particular object had better be of some -particular shape. Natural selection, it should never be forgotten, can act on -each part of each being, solely through and for its advantage. - -Rudimentary parts, it has been stated by some authors, and I believe with -truth, are apt to be highly variable. We shall have to recur to the general -subject of rudimentary and aborted organs; and I will here only add that their -variability seems to be owing to their uselessness, and therefore to natural -selection having no power to check deviations in their structure. Thus -rudimentary parts are left to the free play of the various laws of growth, to -the effects of long-continued disuse, and to the tendency to reversion. +varieties and in species, that when any part or organ is repeated many +times in the structure of the same individual (as the vertebræ in +snakes, and the stamens in polyandrous flowers) the number is variable; +whereas the number of the same part or organ, when it occurs in lesser +numbers, is constant. The same author and some botanists have further +remarked that multiple parts are also very liable to variation in +structure. Inasmuch as this “vegetative repetition,” to use Professor +Owen’s expression, seems to be a sign of low organisation; the foregoing +remark seems connected with the very general opinion of naturalists, +that beings low in the scale of nature are more variable than those +which are higher. I presume that lowness in this case means that the +several parts of the organisation have been but little specialised for +particular functions; and as long as the same part has to perform +diversified work, we can perhaps see why it should remain variable, that +is, why natural selection should have preserved or rejected each little +deviation of form less carefully than when the part has to serve for one +special purpose alone. In the same way that a knife which has to cut all +sorts of things may be of almost any shape; whilst a tool for some +particular object had better be of some particular shape. Natural +selection, it should never be forgotten, can act on each part of each +being, solely through and for its advantage. + +Rudimentary parts, it has been stated by some authors, and I believe +with truth, are apt to be highly variable. We shall have to recur to the +general subject of rudimentary and aborted organs; and I will here only +add that their variability seems to be owing to their uselessness, and +therefore to natural selection having no power to check deviations in +their structure. Thus rudimentary parts are left to the free play of the +various laws of growth, to the effects of long-continued disuse, and to +the tendency to reversion. A part developed in any species in an extraordinary degree or manner, in -comparison with the same part in allied species, tends to be highly variable -.—Several years ago I was much struck with a remark, nearly to the above -effect, published by Mr. Waterhouse. I infer also from an observation made by -Professor Owen, with respect to the length of the arms of the ourang-outang, -that he has come to a nearly similar conclusion. It is hopeless to attempt to -convince any one of the truth of this proposition without giving the long array -of facts which I have collected, and which cannot possibly be here introduced. -I can only state my conviction that it is a rule of high generality. I am aware -of several causes of error, but I hope that I have made due allowance for them. -It should be understood that the rule by no means applies to any part, however -unusually developed, unless it be unusually developed in comparison with the -same part in closely allied species. Thus, the bat’s wing is a most abnormal -structure in the class mammalia; but the rule would not here apply, because -there is a whole group of bats having wings; it would apply only if some one -species of bat had its wings developed in some remarkable manner in comparison -with the other species of the same genus. The rule applies very strongly in the -case of secondary sexual characters, when displayed in any unusual manner. The -term, secondary sexual characters, used by Hunter, applies to characters which -are attached to one sex, but are not directly connected with the act of -reproduction. The rule applies to males and females; but as females more rarely -offer remarkable secondary sexual characters, it applies more rarely to them. -The rule being so plainly applicable in the case of secondary sexual -characters, may be due to the great variability of these characters, whether or -not displayed in any unusual manner—of which fact I think there can be little -doubt. But that our rule is not confined to secondary sexual characters is -clearly shown in the case of hermaphrodite cirripedes; and I may here add, that -I particularly attended to Mr. Waterhouse’s remark, whilst investigating this -Order, and I am fully convinced that the rule almost invariably holds good with -cirripedes. I shall, in my future work, give a list of the more remarkable -cases; I will here only briefly give one, as it illustrates the rule in its -largest application. The opercular valves of sessile cirripedes (rock -barnacles) are, in every sense of the word, very important structures, and they -differ extremely little even in different genera; but in the several species of -one genus, Pyrgoma, these valves present a marvellous amount of -diversification: the homologous valves in the different species being sometimes -wholly unlike in shape; and the amount of variation in the individuals of -several of the species is so great, that it is no exaggeration to state that -the varieties differ more from each other in the characters of these important -valves than do other species of distinct genera. - -As birds within the same country vary in a remarkably small degree, I have -particularly attended to them, and the rule seems to me certainly to hold good -in this class. I cannot make out that it applies to plants, and this would -seriously have shaken my belief in its truth, had not the great variability in -plants made it particularly difficult to compare their relative degrees of -variability. - -When we see any part or organ developed in a remarkable degree or manner in any -species, the fair presumption is that it is of high importance to that species; -nevertheless the part in this case is eminently liable to variation. Why should -this be so? On the view that each species has been independently created, with -all its parts as we now see them, I can see no explanation. But on the view -that groups of species have descended from other species, and have been -modified through natural selection, I think we can obtain some light. In our -domestic animals, if any part, or the whole animal, be neglected and no -selection be applied, that part (for instance, the comb in the Dorking fowl) or -the whole breed will cease to have a nearly uniform character. The breed will -then be said to have degenerated. In rudimentary organs, and in those which -have been but little specialised for any particular purpose, and perhaps in -polymorphic groups, we see a nearly parallel natural case; for in such cases -natural selection either has not or cannot come into full play, and thus the -organisation is left in a fluctuating condition. But what here more especially -concerns us is, that in our domestic animals those points, which at the present -time are undergoing rapid change by continued selection, are also eminently -liable to variation. Look at the breeds of the pigeon; see what a prodigious -amount of difference there is in the beak of the different tumblers, in the -beak and wattle of the different carriers, in the carriage and tail of our -fantails, etc., these being the points now mainly attended to by English -fanciers. Even in the sub-breeds, as in the short-faced tumbler, it is -notoriously difficult to breed them nearly to perfection, and frequently -individuals are born which depart widely from the standard. There may be truly -said to be a constant struggle going on between, on the one hand, the tendency -to reversion to a less modified state, as well as an innate tendency to further -variability of all kinds, and, on the other hand, the power of steady selection -to keep the breed true. In the long run selection gains the day, and we do not -expect to fail so far as to breed a bird as coarse as a common tumbler from a -good short-faced strain. But as long as selection is rapidly going on, there -may always be expected to be much variability in the structure undergoing -modification. It further deserves notice that these variable characters, -produced by man’s selection, sometimes become attached, from causes quite -unknown to us, more to one sex than to the other, generally to the male sex, as +comparison with the same part in allied species, tends to be highly +variable .—Several years ago I was much struck with a remark, nearly to +the above effect, published by Mr. Waterhouse. I infer also from an +observation made by Professor Owen, with respect to the length of the +arms of the ourang-outang, that he has come to a nearly similar +conclusion. It is hopeless to attempt to convince any one of the truth +of this proposition without giving the long array of facts which I have +collected, and which cannot possibly be here introduced. I can only +state my conviction that it is a rule of high generality. I am aware of +several causes of error, but I hope that I have made due allowance for +them. It should be understood that the rule by no means applies to any +part, however unusually developed, unless it be unusually developed in +comparison with the same part in closely allied species. Thus, the bat’s +wing is a most abnormal structure in the class mammalia; but the rule +would not here apply, because there is a whole group of bats having +wings; it would apply only if some one species of bat had its wings +developed in some remarkable manner in comparison with the other species +of the same genus. The rule applies very strongly in the case of +secondary sexual characters, when displayed in any unusual manner. The +term, secondary sexual characters, used by Hunter, applies to characters +which are attached to one sex, but are not directly connected with the +act of reproduction. The rule applies to males and females; but as +females more rarely offer remarkable secondary sexual characters, it +applies more rarely to them. The rule being so plainly applicable in +the case of secondary sexual characters, may be due to the great +variability of these characters, whether or not displayed in any unusual +manner—of which fact I think there can be little doubt. But that our +rule is not confined to secondary sexual characters is clearly shown in +the case of hermaphrodite cirripedes; and I may here add, that I +particularly attended to Mr. Waterhouse’s remark, whilst investigating +this Order, and I am fully convinced that the rule almost invariably +holds good with cirripedes. I shall, in my future work, give a list of +the more remarkable cases; I will here only briefly give one, as it +illustrates the rule in its largest application. The opercular valves of +sessile cirripedes (rock barnacles) are, in every sense of the word, +very important structures, and they differ extremely little even in +different genera; but in the several species of one genus, Pyrgoma, +these valves present a marvellous amount of diversification: the +homologous valves in the different species being sometimes wholly unlike +in shape; and the amount of variation in the individuals of several of +the species is so great, that it is no exaggeration to state that the +varieties differ more from each other in the characters of these +important valves than do other species of distinct genera. + +As birds within the same country vary in a remarkably small degree, I +have particularly attended to them, and the rule seems to me certainly +to hold good in this class. I cannot make out that it applies to plants, +and this would seriously have shaken my belief in its truth, had not the +great variability in plants made it particularly difficult to compare +their relative degrees of variability. + +When we see any part or organ developed in a remarkable degree or manner +in any species, the fair presumption is that it is of high importance to +that species; nevertheless the part in this case is eminently liable to +variation. Why should this be so? On the view that each species has been +independently created, with all its parts as we now see them, I can see +no explanation. But on the view that groups of species have descended +from other species, and have been modified through natural selection, I +think we can obtain some light. In our domestic animals, if any part, or +the whole animal, be neglected and no selection be applied, that part +(for instance, the comb in the Dorking fowl) or the whole breed will +cease to have a nearly uniform character. The breed will then be said to +have degenerated. In rudimentary organs, and in those which have been +but little specialised for any particular purpose, and perhaps in +polymorphic groups, we see a nearly parallel natural case; for in such +cases natural selection either has not or cannot come into full play, +and thus the organisation is left in a fluctuating condition. But what +here more especially concerns us is, that in our domestic animals those +points, which at the present time are undergoing rapid change by +continued selection, are also eminently liable to variation. Look at the +breeds of the pigeon; see what a prodigious amount of difference there +is in the beak of the different tumblers, in the beak and wattle of the +different carriers, in the carriage and tail of our fantails, etc., +these being the points now mainly attended to by English fanciers. Even +in the sub-breeds, as in the short-faced tumbler, it is notoriously +difficult to breed them nearly to perfection, and frequently individuals +are born which depart widely from the standard. There may be truly said +to be a constant struggle going on between, on the one hand, the +tendency to reversion to a less modified state, as well as an innate +tendency to further variability of all kinds, and, on the other hand, +the power of steady selection to keep the breed true. In the long run +selection gains the day, and we do not expect to fail so far as to breed +a bird as coarse as a common tumbler from a good short-faced strain. But +as long as selection is rapidly going on, there may always be expected +to be much variability in the structure undergoing modification. It +further deserves notice that these variable characters, produced by +man’s selection, sometimes become attached, from causes quite unknown to +us, more to one sex than to the other, generally to the male sex, as with the wattle of carriers and the enlarged crop of pouters. -Now let us turn to nature. When a part has been developed in an extraordinary -manner in any one species, compared with the other species of the same genus, -we may conclude that this part has undergone an extraordinary amount of -modification, since the period when the species branched off from the common -progenitor of the genus. This period will seldom be remote in any extreme -degree, as species very rarely endure for more than one geological period. An -extraordinary amount of modification implies an unusually large and -long-continued amount of variability, which has continually been accumulated by -natural selection for the benefit of the species. But as the variability of the -extraordinarily-developed part or organ has been so great and long-continued -within a period not excessively remote, we might, as a general rule, expect -still to find more variability in such parts than in other parts of the -organisation, which have remained for a much longer period nearly constant. And -this, I am convinced, is the case. That the struggle between natural selection -on the one hand, and the tendency to reversion and variability on the other -hand, will in the course of time cease; and that the most abnormally developed -organs may be made constant, I can see no reason to doubt. Hence when an organ, -however abnormal it may be, has been transmitted in approximately the same -condition to many modified descendants, as in the case of the wing of the bat, -it must have existed, according to my theory, for an immense period in nearly -the same state; and thus it comes to be no more variable than any other -structure. It is only in those cases in which the modification has been -comparatively recent and extraordinarily great that we ought to find the -generative variability, as it may be called, still present in a high degree. -For in this case the variability will seldom as yet have been fixed by the -continued selection of the individuals varying in the required manner and -degree, and by the continued rejection of those tending to revert to a former -and less modified condition. - -The principle included in these remarks may be extended. It is notorious that -specific characters are more variable than generic. To explain by a simple -example what is meant. If some species in a large genus of plants had blue -flowers and some had red, the colour would be only a specific character, and no -one would be surprised at one of the blue species varying into red, or -conversely; but if all the species had blue flowers, the colour would become a -generic character, and its variation would be a more unusual circumstance. I -have chosen this example because an explanation is not in this case applicable, -which most naturalists would advance, namely, that specific characters are more -variable than generic, because they are taken from parts of less physiological +Now let us turn to nature. When a part has been developed in an +extraordinary manner in any one species, compared with the other species +of the same genus, we may conclude that this part has undergone an +extraordinary amount of modification, since the period when the species +branched off from the common progenitor of the genus. This period will +seldom be remote in any extreme degree, as species very rarely endure +for more than one geological period. An extraordinary amount of +modification implies an unusually large and long-continued amount of +variability, which has continually been accumulated by natural selection +for the benefit of the species. But as the variability of the +extraordinarily-developed part or organ has been so great and +long-continued within a period not excessively remote, we might, as a +general rule, expect still to find more variability in such parts than +in other parts of the organisation, which have remained for a much +longer period nearly constant. And this, I am convinced, is the case. +That the struggle between natural selection on the one hand, and the +tendency to reversion and variability on the other hand, will in the +course of time cease; and that the most abnormally developed organs may +be made constant, I can see no reason to doubt. Hence when an organ, +however abnormal it may be, has been transmitted in approximately the +same condition to many modified descendants, as in the case of the wing +of the bat, it must have existed, according to my theory, for an immense +period in nearly the same state; and thus it comes to be no more +variable than any other structure. It is only in those cases in which +the modification has been comparatively recent and extraordinarily great +that we ought to find the generative variability, as it may be called, +still present in a high degree. For in this case the variability will +seldom as yet have been fixed by the continued selection of the +individuals varying in the required manner and degree, and by the +continued rejection of those tending to revert to a former and less +modified condition. + +The principle included in these remarks may be extended. It is notorious +that specific characters are more variable than generic. To explain by a +simple example what is meant. If some species in a large genus of plants +had blue flowers and some had red, the colour would be only a specific +character, and no one would be surprised at one of the blue species +varying into red, or conversely; but if all the species had blue +flowers, the colour would become a generic character, and its variation +would be a more unusual circumstance. I have chosen this example because +an explanation is not in this case applicable, which most naturalists +would advance, namely, that specific characters are more variable than +generic, because they are taken from parts of less physiological importance than those commonly used for classing genera. I believe this -explanation is partly, yet only indirectly, true; I shall, however, have to -return to this subject in our chapter on Classification. It would be almost -superfluous to adduce evidence in support of the above statement, that specific -characters are more variable than generic; but I have repeatedly noticed in -works on natural history, that when an author has remarked with surprise that -some important organ or part, which is generally very constant throughout large -groups of species, has differed considerably in closely-allied species, that it -has, also, been variable in the individuals of some of the species. And this -fact shows that a character, which is generally of generic value, when it sinks -in value and becomes only of specific value, often becomes variable, though its +explanation is partly, yet only indirectly, true; I shall, however, have +to return to this subject in our chapter on Classification. It would be +almost superfluous to adduce evidence in support of the above statement, +that specific characters are more variable than generic; but I have +repeatedly noticed in works on natural history, that when an author has +remarked with surprise that some important organ or part, which is +generally very constant throughout large groups of species, has differed +considerably in closely-allied species, that it has, also, been variable +in the individuals of some of the species. And this fact shows that a +character, which is generally of generic value, when it sinks in value +and becomes only of specific value, often becomes variable, though its physiological importance may remain the same. Something of the same kind -applies to monstrosities: at least Is. Geoffroy St. Hilaire seems to entertain -no doubt, that the more an organ normally differs in the different species of -the same group, the more subject it is to individual anomalies. - -On the ordinary view of each species having been independently created, why -should that part of the structure, which differs from the same part in other -independently-created species of the same genus, be more variable than those -parts which are closely alike in the several species? I do not see that any -explanation can be given. But on the view of species being only strongly marked -and fixed varieties, we might surely expect to find them still often continuing -to vary in those parts of their structure which have varied within a moderately -recent period, and which have thus come to differ. Or to state the case in -another manner:—the points in which all the species of a genus resemble each -other, and in which they differ from the species of some other genus, are -called generic characters; and these characters in common I attribute to -inheritance from a common progenitor, for it can rarely have happened that -natural selection will have modified several species, fitted to more or less -widely-different habits, in exactly the same manner: and as these so-called -generic characters have been inherited from a remote period, since that period -when the species first branched off from their common progenitor, and -subsequently have not varied or come to differ in any degree, or only in a -slight degree, it is not probable that they should vary at the present day. On -the other hand, the points in which species differ from other species of the -same genus, are called specific characters; and as these specific characters -have varied and come to differ within the period of the branching off of the -species from a common progenitor, it is probable that they should still often -be in some degree variable,—at least more variable than those parts of the -organisation which have for a very long period remained constant. - -In connexion with the present subject, I will make only two other remarks. I -think it will be admitted, without my entering on details, that secondary -sexual characters are very variable; I think it also will be admitted that -species of the same group differ from each other more widely in their secondary -sexual characters, than in other parts of their organisation; compare, for -instance, the amount of difference between the males of gallinaceous birds, in -which secondary sexual characters are strongly displayed, with the amount of -difference between their females; and the truth of this proposition will be -granted. The cause of the original variability of secondary sexual characters -is not manifest; but we can see why these characters should not have been +applies to monstrosities: at least Is. Geoffroy St. Hilaire seems to +entertain no doubt, that the more an organ normally differs in the +different species of the same group, the more subject it is to +individual anomalies. + +On the ordinary view of each species having been independently created, +why should that part of the structure, which differs from the same part +in other independently-created species of the same genus, be more +variable than those parts which are closely alike in the several +species? I do not see that any explanation can be given. But on the view +of species being only strongly marked and fixed varieties, we might +surely expect to find them still often continuing to vary in those parts +of their structure which have varied within a moderately recent period, +and which have thus come to differ. Or to state the case in another +manner:—the points in which all the species of a genus resemble each +other, and in which they differ from the species of some other genus, +are called generic characters; and these characters in common I +attribute to inheritance from a common progenitor, for it can rarely +have happened that natural selection will have modified several species, +fitted to more or less widely-different habits, in exactly the same +manner: and as these so-called generic characters have been inherited +from a remote period, since that period when the species first branched +off from their common progenitor, and subsequently have not varied or +come to differ in any degree, or only in a slight degree, it is not +probable that they should vary at the present day. On the other hand, +the points in which species differ from other species of the same genus, +are called specific characters; and as these specific characters have +varied and come to differ within the period of the branching off of the +species from a common progenitor, it is probable that they should still +often be in some degree variable,—at least more variable than those +parts of the organisation which have for a very long period remained +constant. + +In connexion with the present subject, I will make only two other +remarks. I think it will be admitted, without my entering on details, +that secondary sexual characters are very variable; I think it also will +be admitted that species of the same group differ from each other more +widely in their secondary sexual characters, than in other parts of +their organisation; compare, for instance, the amount of difference +between the males of gallinaceous birds, in which secondary sexual +characters are strongly displayed, with the amount of difference between +their females; and the truth of this proposition will be granted. The +cause of the original variability of secondary sexual characters is not +manifest; but we can see why these characters should not have been rendered as constant and uniform as other parts of the organisation; for -secondary sexual characters have been accumulated by sexual selection, which is -less rigid in its action than ordinary selection, as it does not entail death, -but only gives fewer offspring to the less favoured males. Whatever the cause -may be of the variability of secondary sexual characters, as they are highly -variable, sexual selection will have had a wide scope for action, and may thus -readily have succeeded in giving to the species of the same group a greater -amount of difference in their sexual characters, than in other parts of their -structure. - -It is a remarkable fact, that the secondary sexual differences between the two -sexes of the same species are generally displayed in the very same parts of the -organisation in which the different species of the same genus differ from each -other. Of this fact I will give in illustration two instances, the first which -happen to stand on my list; and as the differences in these cases are of a very -unusual nature, the relation can hardly be accidental. The same number of -joints in the tarsi is a character generally common to very large groups of -beetles, but in the Engidæ, as Westwood has remarked, the number varies -greatly; and the number likewise differs in the two sexes of the same species: -again in fossorial hymenoptera, the manner of neuration of the wings is a -character of the highest importance, because common to large groups; but in -certain genera the neuration differs in the different species, and likewise in -the two sexes of the same species. This relation has a clear meaning on my view -of the subject: I look at all the species of the same genus as having as -certainly descended from the same progenitor, as have the two sexes of any one -of the species. Consequently, whatever part of the structure of the common -progenitor, or of its early descendants, became variable; variations of this -part would it is highly probable, be taken advantage of by natural and sexual -selection, in order to fit the several species to their several places in the -economy of nature, and likewise to fit the two sexes of the same species to -each other, or to fit the males and females to different habits of life, or the -males to struggle with other males for the possession of the females. - -Finally, then, I conclude that the greater variability of specific characters, -or those which distinguish species from species, than of generic characters, or -those which the species possess in common;—that the frequent extreme -variability of any part which is developed in a species in an extraordinary -manner in comparison with the same part in its congeners; and the not great -degree of variability in a part, however extraordinarily it may be developed, -if it be common to a whole group of species;—that the great variability of -secondary sexual characters, and the great amount of difference in these same -characters between closely allied species;—that secondary sexual and ordinary +secondary sexual characters have been accumulated by sexual selection, +which is less rigid in its action than ordinary selection, as it does +not entail death, but only gives fewer offspring to the less favoured +males. Whatever the cause may be of the variability of secondary sexual +characters, as they are highly variable, sexual selection will have had +a wide scope for action, and may thus readily have succeeded in giving +to the species of the same group a greater amount of difference in their +sexual characters, than in other parts of their structure. + +It is a remarkable fact, that the secondary sexual differences between +the two sexes of the same species are generally displayed in the very +same parts of the organisation in which the different species of the +same genus differ from each other. Of this fact I will give in +illustration two instances, the first which happen to stand on my list; +and as the differences in these cases are of a very unusual nature, the +relation can hardly be accidental. The same number of joints in the +tarsi is a character generally common to very large groups of beetles, +but in the Engidæ, as Westwood has remarked, the number varies greatly; +and the number likewise differs in the two sexes of the same species: +again in fossorial hymenoptera, the manner of neuration of the wings is +a character of the highest importance, because common to large groups; +but in certain genera the neuration differs in the different species, +and likewise in the two sexes of the same species. This relation has a +clear meaning on my view of the subject: I look at all the species of +the same genus as having as certainly descended from the same +progenitor, as have the two sexes of any one of the species. +Consequently, whatever part of the structure of the common progenitor, +or of its early descendants, became variable; variations of this part +would it is highly probable, be taken advantage of by natural and sexual +selection, in order to fit the several species to their several places +in the economy of nature, and likewise to fit the two sexes of the same +species to each other, or to fit the males and females to different +habits of life, or the males to struggle with other males for the +possession of the females. + +Finally, then, I conclude that the greater variability of specific +characters, or those which distinguish species from species, than of +generic characters, or those which the species possess in common;—that +the frequent extreme variability of any part which is developed in a +species in an extraordinary manner in comparison with the same part in +its congeners; and the not great degree of variability in a part, +however extraordinarily it may be developed, if it be common to a whole +group of species;—that the great variability of secondary sexual +characters, and the great amount of difference in these same characters +between closely allied species;—that secondary sexual and ordinary specific differences are generally displayed in the same parts of the -organisation,—are all principles closely connected together. All being mainly -due to the species of the same group having descended from a common progenitor, -from whom they have inherited much in common,—to parts which have recently and -largely varied being more likely still to go on varying than parts which have -long been inherited and have not varied,—to natural selection having more or -less completely, according to the lapse of time, overmastered the tendency to -reversion and to further variability,—to sexual selection being less rigid than -ordinary selection,—and to variations in the same parts having been accumulated -by natural and sexual selection, and thus adapted for secondary sexual, and for -ordinary specific purposes. - -Distinct species present analogous variations; and a variety of one species -often assumes some of the characters of an allied species, or reverts to some -of the characters of an early progenitor.—These propositions will be most -readily understood by looking to our domestic races. The most distinct breeds -of pigeons, in countries most widely apart, present sub-varieties with reversed -feathers on the head and feathers on the feet,—characters not possessed by the -aboriginal rock-pigeon; these then are analogous variations in two or more -distinct races. The frequent presence of fourteen or even sixteen tail-feathers +organisation,—are all principles closely connected together. All being +mainly due to the species of the same group having descended from a +common progenitor, from whom they have inherited much in common,—to +parts which have recently and largely varied being more likely still to +go on varying than parts which have long been inherited and have not +varied,—to natural selection having more or less completely, according +to the lapse of time, overmastered the tendency to reversion and to +further variability,—to sexual selection being less rigid than ordinary +selection,—and to variations in the same parts having been accumulated +by natural and sexual selection, and thus adapted for secondary sexual, +and for ordinary specific purposes. + +Distinct species present analogous variations; and a variety of one +species often assumes some of the characters of an allied species, or +reverts to some of the characters of an early progenitor.—These +propositions will be most readily understood by looking to our domestic +races. The most distinct breeds of pigeons, in countries most widely +apart, present sub-varieties with reversed feathers on the head and +feathers on the feet,—characters not possessed by the aboriginal +rock-pigeon; these then are analogous variations in two or more distinct +races. The frequent presence of fourteen or even sixteen tail-feathers in the pouter, may be considered as a variation representing the normal -structure of another race, the fantail. I presume that no one will doubt that -all such analogous variations are due to the several races of the pigeon having -inherited from a common parent the same constitution and tendency to variation, -when acted on by similar unknown influences. In the vegetable kingdom we have a -case of analogous variation, in the enlarged stems, or roots as commonly -called, of the Swedish turnip and Ruta baga, plants which several botanists -rank as varieties produced by cultivation from a common parent: if this be not -so, the case will then be one of analogous variation in two so-called distinct -species; and to these a third may be added, namely, the common turnip. -According to the ordinary view of each species having been independently -created, we should have to attribute this similarity in the enlarged stems of -these three plants, not to the vera causa of community of descent, and a -consequent tendency to vary in a like manner, but to three separate yet closely -related acts of creation. - -With pigeons, however, we have another case, namely, the occasional appearance -in all the breeds, of slaty-blue birds with two black bars on the wings, a -white rump, a bar at the end of the tail, with the outer feathers externally -edged near their bases with white. As all these marks are characteristic of the -parent rock-pigeon, I presume that no one will doubt that this is a case of -reversion, and not of a new yet analogous variation appearing in the several -breeds. We may I think confidently come to this conclusion, because, as we have -seen, these coloured marks are eminently liable to appear in the crossed -offspring of two distinct and differently coloured breeds; and in this case -there is nothing in the external conditions of life to cause the reappearance -of the slaty-blue, with the several marks, beyond the influence of the mere act -of crossing on the laws of inheritance. - -No doubt it is a very surprising fact that characters should reappear after -having been lost for many, perhaps for hundreds of generations. But when a -breed has been crossed only once by some other breed, the offspring -occasionally show a tendency to revert in character to the foreign breed for -many generations—some say, for a dozen or even a score of generations. After -twelve generations, the proportion of blood, to use a common expression, of any -one ancestor, is only 1 in 2048; and yet, as we see, it is generally believed -that a tendency to reversion is retained by this very small proportion of -foreign blood. In a breed which has not been crossed, but in which both parents -have lost some character which their progenitor possessed, the tendency, -whether strong or weak, to reproduce the lost character might be, as was -formerly remarked, for all that we can see to the contrary, transmitted for -almost any number of generations. When a character which has been lost in a -breed, reappears after a great number of generations, the most probable -hypothesis is, not that the offspring suddenly takes after an ancestor some -hundred generations distant, but that in each successive generation there has -been a tendency to reproduce the character in question, which at last, under -unknown favourable conditions, gains an ascendancy. For instance, it is -probable that in each generation of the barb-pigeon, which produces most rarely -a blue and black-barred bird, there has been a tendency in each generation in -the plumage to assume this colour. This view is hypothetical, but could be -supported by some facts; and I can see no more abstract improbability in a -tendency to produce any character being inherited for an endless number of -generations, than in quite useless or rudimentary organs being, as we all know -them to be, thus inherited. Indeed, we may sometimes observe a mere tendency to -produce a rudiment inherited: for instance, in the common snapdragon -(Antirrhinum) a rudiment of a fifth stamen so often appears, that this plant -must have an inherited tendency to produce it. +structure of another race, the fantail. I presume that no one will doubt +that all such analogous variations are due to the several races of the +pigeon having inherited from a common parent the same constitution and +tendency to variation, when acted on by similar unknown influences. In +the vegetable kingdom we have a case of analogous variation, in the +enlarged stems, or roots as commonly called, of the Swedish turnip and +Ruta baga, plants which several botanists rank as varieties produced by +cultivation from a common parent: if this be not so, the case will then +be one of analogous variation in two so-called distinct species; and to +these a third may be added, namely, the common turnip. According to the +ordinary view of each species having been independently created, we +should have to attribute this similarity in the enlarged stems of these +three plants, not to the vera causa of community of descent, and a +consequent tendency to vary in a like manner, but to three separate yet +closely related acts of creation. + +With pigeons, however, we have another case, namely, the occasional +appearance in all the breeds, of slaty-blue birds with two black bars on +the wings, a white rump, a bar at the end of the tail, with the outer +feathers externally edged near their bases with white. As all these +marks are characteristic of the parent rock-pigeon, I presume that no +one will doubt that this is a case of reversion, and not of a new yet +analogous variation appearing in the several breeds. We may I think +confidently come to this conclusion, because, as we have seen, these +coloured marks are eminently liable to appear in the crossed offspring +of two distinct and differently coloured breeds; and in this case there +is nothing in the external conditions of life to cause the reappearance +of the slaty-blue, with the several marks, beyond the influence of the +mere act of crossing on the laws of inheritance. + +No doubt it is a very surprising fact that characters should reappear +after having been lost for many, perhaps for hundreds of generations. +But when a breed has been crossed only once by some other breed, the +offspring occasionally show a tendency to revert in character to the +foreign breed for many generations—some say, for a dozen or even a score +of generations. After twelve generations, the proportion of blood, to +use a common expression, of any one ancestor, is only 1 in 2048; and +yet, as we see, it is generally believed that a tendency to reversion is +retained by this very small proportion of foreign blood. In a breed +which has not been crossed, but in which both parents have lost some +character which their progenitor possessed, the tendency, whether strong +or weak, to reproduce the lost character might be, as was formerly +remarked, for all that we can see to the contrary, transmitted for +almost any number of generations. When a character which has been lost +in a breed, reappears after a great number of generations, the most +probable hypothesis is, not that the offspring suddenly takes after an +ancestor some hundred generations distant, but that in each successive +generation there has been a tendency to reproduce the character in +question, which at last, under unknown favourable conditions, gains an +ascendancy. For instance, it is probable that in each generation of the +barb-pigeon, which produces most rarely a blue and black-barred bird, +there has been a tendency in each generation in the plumage to assume +this colour. This view is hypothetical, but could be supported by some +facts; and I can see no more abstract improbability in a tendency to +produce any character being inherited for an endless number of +generations, than in quite useless or rudimentary organs being, as we +all know them to be, thus inherited. Indeed, we may sometimes observe a +mere tendency to produce a rudiment inherited: for instance, in the +common snapdragon (Antirrhinum) a rudiment of a fifth stamen so often +appears, that this plant must have an inherited tendency to produce it. As all the species of the same genus are supposed, on my theory, to have descended from a common parent, it might be expected that they would -occasionally vary in an analogous manner; so that a variety of one species -would resemble in some of its characters another species; this other species -being on my view only a well-marked and permanent variety. But characters thus -gained would probably be of an unimportant nature, for the presence of all -important characters will be governed by natural selection, in accordance with -the diverse habits of the species, and will not be left to the mutual action of -the conditions of life and of a similar inherited constitution. It might -further be expected that the species of the same genus would occasionally -exhibit reversions to lost ancestral characters. As, however, we never know the -exact character of the common ancestor of a group, we could not distinguish -these two cases: if, for instance, we did not know that the rock-pigeon was not +occasionally vary in an analogous manner; so that a variety of one +species would resemble in some of its characters another species; this +other species being on my view only a well-marked and permanent variety. +But characters thus gained would probably be of an unimportant nature, +for the presence of all important characters will be governed by natural +selection, in accordance with the diverse habits of the species, and +will not be left to the mutual action of the conditions of life and of a +similar inherited constitution. It might further be expected that the +species of the same genus would occasionally exhibit reversions to lost +ancestral characters. As, however, we never know the exact character of +the common ancestor of a group, we could not distinguish these two +cases: if, for instance, we did not know that the rock-pigeon was not feather-footed or turn-crowned, we could not have told, whether these -characters in our domestic breeds were reversions or only analogous variations; -but we might have inferred that the blueness was a case of reversion, from the -number of the markings, which are correlated with the blue tint, and which it -does not appear probable would all appear together from simple variation. More -especially we might have inferred this, from the blue colour and marks so often -appearing when distinct breeds of diverse colours are crossed. Hence, though -under nature it must generally be left doubtful, what cases are reversions to -an anciently existing character, and what are new but analogous variations, yet -we ought, on my theory, sometimes to find the varying offspring of a species -assuming characters (either from reversion or from analogous variation) which -already occur in some other members of the same group. And this undoubtedly is -the case in nature. - -A considerable part of the difficulty in recognising a variable species in our -systematic works, is due to its varieties mocking, as it were, some of the -other species of the same genus. A considerable catalogue, also, could be given -of forms intermediate between two other forms, which themselves must be -doubtfully ranked as either varieties or species; and this shows, unless all -these forms be considered as independently created species, that the one in -varying has assumed some of the characters of the other, so as to produce the -intermediate form. But the best evidence is afforded by parts or organs of an -important and uniform nature occasionally varying so as to acquire, in some -degree, the character of the same part or organ in an allied species. I have -collected a long list of such cases; but here, as before, I lie under a great -disadvantage in not being able to give them. I can only repeat that such cases -certainly do occur, and seem to me very remarkable. - -I will, however, give one curious and complex case, not indeed as affecting any -important character, but from occurring in several species of the same genus, -partly under domestication and partly under nature. It is a case apparently of -reversion. The ass not rarely has very distinct transverse bars on its legs, -like those on the legs of a zebra: it has been asserted that these are plainest -in the foal, and from inquiries which I have made, I believe this to be true. -It has also been asserted that the stripe on each shoulder is sometimes double. -The shoulder stripe is certainly very variable in length and outline. A white -ass, but not an albino, has been described without either spinal or -shoulder-stripe; and these stripes are sometimes very obscure, or actually -quite lost, in dark-coloured asses. The koulan of Pallas is said to have been -seen with a double shoulder-stripe. The hemionus has no shoulder-stripe; but -traces of it, as stated by Mr. Blyth and others, occasionally appear: and I -have been informed by Colonel Poole that the foals of this species are -generally striped on the legs, and faintly on the shoulder. The quagga, though -so plainly barred like a zebra over the body, is without bars on the legs; but -Dr. Gray has figured one specimen with very distinct zebra-like bars on the -hocks. - -With respect to the horse, I have collected cases in England of the spinal -stripe in horses of the most distinct breeds, and of all colours; transverse -bars on the legs are not rare in duns, mouse-duns, and in one instance in a -chestnut: a faint shoulder-stripe may sometimes be seen in duns, and I have -seen a trace in a bay horse. My son made a careful examination and sketch for -me of a dun Belgian cart-horse with a double stripe on each shoulder and with -leg-stripes; and a man, whom I can implicitly trust, has examined for me a -small dun Welch pony with three short parallel stripes on each shoulder. - -In the north-west part of India the Kattywar breed of horses is so generally -striped, that, as I hear from Colonel Poole, who examined the breed for the -Indian Government, a horse without stripes is not considered as purely-bred. -The spine is always striped; the legs are generally barred; and the -shoulder-stripe, which is sometimes double and sometimes treble, is common; the -side of the face, moreover, is sometimes striped. The stripes are plainest in -the foal; and sometimes quite disappear in old horses. Colonel Poole has seen -both gray and bay Kattywar horses striped when first foaled. I have, also, -reason to suspect, from information given me by Mr. W. W. Edwards, that with -the English race-horse the spinal stripe is much commoner in the foal than in -the full-grown animal. Without here entering on further details, I may state -that I have collected cases of leg and shoulder stripes in horses of very -different breeds, in various countries from Britain to Eastern China; and from -Norway in the north to the Malay Archipelago in the south. In all parts of the -world these stripes occur far oftenest in duns and mouse-duns; by the term dun -a large range of colour is included, from one between brown and black to a -close approach to cream-colour. +characters in our domestic breeds were reversions or only analogous +variations; but we might have inferred that the blueness was a case of +reversion, from the number of the markings, which are correlated with +the blue tint, and which it does not appear probable would all appear +together from simple variation. More especially we might have inferred +this, from the blue colour and marks so often appearing when distinct +breeds of diverse colours are crossed. Hence, though under nature it +must generally be left doubtful, what cases are reversions to an +anciently existing character, and what are new but analogous variations, +yet we ought, on my theory, sometimes to find the varying offspring of a +species assuming characters (either from reversion or from analogous +variation) which already occur in some other members of the same group. +And this undoubtedly is the case in nature. + +A considerable part of the difficulty in recognising a variable species +in our systematic works, is due to its varieties mocking, as it were, +some of the other species of the same genus. A considerable catalogue, +also, could be given of forms intermediate between two other forms, +which themselves must be doubtfully ranked as either varieties or +species; and this shows, unless all these forms be considered as +independently created species, that the one in varying has assumed some +of the characters of the other, so as to produce the intermediate form. +But the best evidence is afforded by parts or organs of an important and +uniform nature occasionally varying so as to acquire, in some degree, +the character of the same part or organ in an allied species. I have +collected a long list of such cases; but here, as before, I lie under a +great disadvantage in not being able to give them. I can only repeat +that such cases certainly do occur, and seem to me very remarkable. + +I will, however, give one curious and complex case, not indeed as +affecting any important character, but from occurring in several species +of the same genus, partly under domestication and partly under nature. +It is a case apparently of reversion. The ass not rarely has very +distinct transverse bars on its legs, like those on the legs of a zebra: +it has been asserted that these are plainest in the foal, and from +inquiries which I have made, I believe this to be true. It has also +been asserted that the stripe on each shoulder is sometimes double. The +shoulder stripe is certainly very variable in length and outline. A +white ass, but not an albino, has been described without either spinal +or shoulder-stripe; and these stripes are sometimes very obscure, or +actually quite lost, in dark-coloured asses. The koulan of Pallas is +said to have been seen with a double shoulder-stripe. The hemionus has +no shoulder-stripe; but traces of it, as stated by Mr. Blyth and others, +occasionally appear: and I have been informed by Colonel Poole that the +foals of this species are generally striped on the legs, and faintly on +the shoulder. The quagga, though so plainly barred like a zebra over the +body, is without bars on the legs; but Dr. Gray has figured one specimen +with very distinct zebra-like bars on the hocks. + +With respect to the horse, I have collected cases in England of the +spinal stripe in horses of the most distinct breeds, and of all colours; +transverse bars on the legs are not rare in duns, mouse-duns, and in one +instance in a chestnut: a faint shoulder-stripe may sometimes be seen in +duns, and I have seen a trace in a bay horse. My son made a careful +examination and sketch for me of a dun Belgian cart-horse with a double +stripe on each shoulder and with leg-stripes; and a man, whom I can +implicitly trust, has examined for me a small dun Welch pony with three +short parallel stripes on each shoulder. + +In the north-west part of India the Kattywar breed of horses is so +generally striped, that, as I hear from Colonel Poole, who examined the +breed for the Indian Government, a horse without stripes is not +considered as purely-bred. The spine is always striped; the legs are +generally barred; and the shoulder-stripe, which is sometimes double and +sometimes treble, is common; the side of the face, moreover, is +sometimes striped. The stripes are plainest in the foal; and sometimes +quite disappear in old horses. Colonel Poole has seen both gray and bay +Kattywar horses striped when first foaled. I have, also, reason to +suspect, from information given me by Mr. W. W. Edwards, that with the +English race-horse the spinal stripe is much commoner in the foal than +in the full-grown animal. Without here entering on further details, I +may state that I have collected cases of leg and shoulder stripes in +horses of very different breeds, in various countries from Britain to +Eastern China; and from Norway in the north to the Malay Archipelago in +the south. In all parts of the world these stripes occur far oftenest in +duns and mouse-duns; by the term dun a large range of colour is +included, from one between brown and black to a close approach to +cream-colour. I am aware that Colonel Hamilton Smith, who has written on this subject, -believes that the several breeds of the horse have descended from several -aboriginal species—one of which, the dun, was striped; and that the -above-described appearances are all due to ancient crosses with the dun stock. -But I am not at all satisfied with this theory, and should be loth to apply it -to breeds so distinct as the heavy Belgian cart-horse, Welch ponies, cobs, the -lanky Kattywar race, etc., inhabiting the most distant parts of the world. +believes that the several breeds of the horse have descended from +several aboriginal species—one of which, the dun, was striped; and that +the above-described appearances are all due to ancient crosses with the +dun stock. But I am not at all satisfied with this theory, and should +be loth to apply it to breeds so distinct as the heavy Belgian +cart-horse, Welch ponies, cobs, the lanky Kattywar race, etc., +inhabiting the most distant parts of the world. Now let us turn to the effects of crossing the several species of the -horse-genus. Rollin asserts, that the common mule from the ass and horse is -particularly apt to have bars on its legs. I once saw a mule with its legs so -much striped that any one at first would have thought that it must have been -the product of a zebra; and Mr. W. C. Martin, in his excellent treatise on the -horse, has given a figure of a similar mule. In four coloured drawings, which I -have seen, of hybrids between the ass and zebra, the legs were much more -plainly barred than the rest of the body; and in one of them there was a double -shoulder-stripe. In Lord Moreton’s famous hybrid from a chestnut mare and male -quagga, the hybrid, and even the pure offspring subsequently produced from the -mare by a black Arabian sire, were much more plainly barred across the legs -than is even the pure quagga. Lastly, and this is another most remarkable case, -a hybrid has been figured by Dr. Gray (and he informs me that he knows of a -second case) from the ass and the hemionus; and this hybrid, though the ass -seldom has stripes on its legs and the hemionus has none and has not even a -shoulder-stripe, nevertheless had all four legs barred, and had three short -shoulder-stripes, like those on the dun Welch pony, and even had some -zebra-like stripes on the sides of its face. With respect to this last fact, I -was so convinced that not even a stripe of colour appears from what would -commonly be called an accident, that I was led solely from the occurrence of -the face-stripes on this hybrid from the ass and hemionus, to ask Colonel Poole -whether such face-stripes ever occur in the eminently striped Kattywar breed of +horse-genus. Rollin asserts, that the common mule from the ass and horse +is particularly apt to have bars on its legs. I once saw a mule with its +legs so much striped that any one at first would have thought that it +must have been the product of a zebra; and Mr. W. C. Martin, in his +excellent treatise on the horse, has given a figure of a similar mule. +In four coloured drawings, which I have seen, of hybrids between the ass +and zebra, the legs were much more plainly barred than the rest of the +body; and in one of them there was a double shoulder-stripe. In Lord +Moreton’s famous hybrid from a chestnut mare and male quagga, the +hybrid, and even the pure offspring subsequently produced from the mare +by a black Arabian sire, were much more plainly barred across the legs +than is even the pure quagga. Lastly, and this is another most +remarkable case, a hybrid has been figured by Dr. Gray (and he informs +me that he knows of a second case) from the ass and the hemionus; and +this hybrid, though the ass seldom has stripes on its legs and the +hemionus has none and has not even a shoulder-stripe, nevertheless had +all four legs barred, and had three short shoulder-stripes, like those +on the dun Welch pony, and even had some zebra-like stripes on the sides +of its face. With respect to this last fact, I was so convinced that not +even a stripe of colour appears from what would commonly be called an +accident, that I was led solely from the occurrence of the face-stripes +on this hybrid from the ass and hemionus, to ask Colonel Poole whether +such face-stripes ever occur in the eminently striped Kattywar breed of horses, and was, as we have seen, answered in the affirmative. -What now are we to say to these several facts? We see several very distinct -species of the horse-genus becoming, by simple variation, striped on the legs -like a zebra, or striped on the shoulders like an ass. In the horse we see this -tendency strong whenever a dun tint appears—a tint which approaches to that of -the general colouring of the other species of the genus. The appearance of the -stripes is not accompanied by any change of form or by any other new character. -We see this tendency to become striped most strongly displayed in hybrids from -between several of the most distinct species. Now observe the case of the -several breeds of pigeons: they are descended from a pigeon (including two or -three sub-species or geographical races) of a bluish colour, with certain bars -and other marks; and when any breed assumes by simple variation a bluish tint, -these bars and other marks invariably reappear; but without any other change of -form or character. When the oldest and truest breeds of various colours are -crossed, we see a strong tendency for the blue tint and bars and marks to -reappear in the mongrels. I have stated that the most probable hypothesis to -account for the reappearance of very ancient characters, is—that there is a -tendency in the young of each successive generation to produce the long-lost -character, and that this tendency, from unknown causes, sometimes prevails. And -we have just seen that in several species of the horse-genus the stripes are -either plainer or appear more commonly in the young than in the old. Call the -breeds of pigeons, some of which have bred true for centuries, species; and how -exactly parallel is the case with that of the species of the horse-genus! For -myself, I venture confidently to look back thousands on thousands of -generations, and I see an animal striped like a zebra, but perhaps otherwise -very differently constructed, the common parent of our domestic horse, whether -or not it be descended from one or more wild stocks, of the ass, the hemionus, -quagga, and zebra. - -He who believes that each equine species was independently created, will, I -presume, assert that each species has been created with a tendency to vary, -both under nature and under domestication, in this particular manner, so as -often to become striped like other species of the genus; and that each has been -created with a strong tendency, when crossed with species inhabiting distant -quarters of the world, to produce hybrids resembling in their stripes, not -their own parents, but other species of the genus. To admit this view is, as it -seems to me, to reject a real for an unreal, or at least for an unknown, cause. -It makes the works of God a mere mockery and deception; I would almost as soon -believe with the old and ignorant cosmogonists, that fossil shells had never -lived, but had been created in stone so as to mock the shells now living on the -sea-shore. - -Summary.—Our ignorance of the laws of variation is profound. Not in one case -out of a hundred can we pretend to assign any reason why this or that part -differs, more or less, from the same part in the parents. But whenever we have -the means of instituting a comparison, the same laws appear to have acted in -producing the lesser differences between varieties of the same species, and the -greater differences between species of the same genus. The external conditions -of life, as climate and food, etc., seem to have induced some slight -modifications. Habit in producing constitutional differences, and use in -strengthening, and disuse in weakening and diminishing organs, seem to have -been more potent in their effects. Homologous parts tend to vary in the same -way, and homologous parts tend to cohere. Modifications in hard parts and in -external parts sometimes affect softer and internal parts. When one part is -largely developed, perhaps it tends to draw nourishment from the adjoining -parts; and every part of the structure which can be saved without detriment to -the individual, will be saved. Changes of structure at an early age will -generally affect parts subsequently developed; and there are very many other -correlations of growth, the nature of which we are utterly unable to -understand. Multiple parts are variable in number and in structure, perhaps -arising from such parts not having been closely specialised to any particular -function, so that their modifications have not been closely checked by natural -selection. It is probably from this same cause that organic beings low in the -scale of nature are more variable than those which have their whole -organisation more specialised, and are higher in the scale. Rudimentary organs, -from being useless, will be disregarded by natural selection, and hence -probably are variable. Specific characters—that is, the characters which have -come to differ since the several species of the same genus branched off from a -common parent—are more variable than generic characters, or those which have -long been inherited, and have not differed within this same period. In these -remarks we have referred to special parts or organs being still variable, -because they have recently varied and thus come to differ; but we have also -seen in the second Chapter that the same principle applies to the whole -individual; for in a district where many species of any genus are found—that -is, where there has been much former variation and differentiation, or where -the manufactory of new specific forms has been actively at work—there, on an -average, we now find most varieties or incipient species. Secondary sexual -characters are highly variable, and such characters differ much in the species -of the same group. Variability in the same parts of the organisation has -generally been taken advantage of in giving secondary sexual differences to the -sexes of the same species, and specific differences to the several species of -the same genus. Any part or organ developed to an extraordinary size or in an -extraordinary manner, in comparison with the same part or organ in the allied -species, must have gone through an extraordinary amount of modification since -the genus arose; and thus we can understand why it should often still be -variable in a much higher degree than other parts; for variation is a -long-continued and slow process, and natural selection will in such cases not -as yet have had time to overcome the tendency to further variability and to -reversion to a less modified state. But when a species with any +What now are we to say to these several facts? We see several very +distinct species of the horse-genus becoming, by simple variation, +striped on the legs like a zebra, or striped on the shoulders like an +ass. In the horse we see this tendency strong whenever a dun tint +appears—a tint which approaches to that of the general colouring of the +other species of the genus. The appearance of the stripes is not +accompanied by any change of form or by any other new character. We see +this tendency to become striped most strongly displayed in hybrids from +between several of the most distinct species. Now observe the case of +the several breeds of pigeons: they are descended from a pigeon +(including two or three sub-species or geographical races) of a bluish +colour, with certain bars and other marks; and when any breed assumes by +simple variation a bluish tint, these bars and other marks invariably +reappear; but without any other change of form or character. When the +oldest and truest breeds of various colours are crossed, we see a strong +tendency for the blue tint and bars and marks to reappear in the +mongrels. I have stated that the most probable hypothesis to account for +the reappearance of very ancient characters, is—that there is a tendency +in the young of each successive generation to produce the long-lost +character, and that this tendency, from unknown causes, sometimes +prevails. And we have just seen that in several species of the +horse-genus the stripes are either plainer or appear more commonly in +the young than in the old. Call the breeds of pigeons, some of which +have bred true for centuries, species; and how exactly parallel is the +case with that of the species of the horse-genus! For myself, I venture +confidently to look back thousands on thousands of generations, and I +see an animal striped like a zebra, but perhaps otherwise very +differently constructed, the common parent of our domestic horse, +whether or not it be descended from one or more wild stocks, of the ass, +the hemionus, quagga, and zebra. + +He who believes that each equine species was independently created, +will, I presume, assert that each species has been created with a +tendency to vary, both under nature and under domestication, in this +particular manner, so as often to become striped like other species of +the genus; and that each has been created with a strong tendency, when +crossed with species inhabiting distant quarters of the world, to +produce hybrids resembling in their stripes, not their own parents, but +other species of the genus. To admit this view is, as it seems to me, to +reject a real for an unreal, or at least for an unknown, cause. It +makes the works of God a mere mockery and deception; I would almost as +soon believe with the old and ignorant cosmogonists, that fossil shells +had never lived, but had been created in stone so as to mock the shells +now living on the sea-shore. + +Summary.—Our ignorance of the laws of variation is profound. Not in one +case out of a hundred can we pretend to assign any reason why this or +that part differs, more or less, from the same part in the parents. But +whenever we have the means of instituting a comparison, the same laws +appear to have acted in producing the lesser differences between +varieties of the same species, and the greater differences between +species of the same genus. The external conditions of life, as climate +and food, etc., seem to have induced some slight modifications. Habit in +producing constitutional differences, and use in strengthening, and +disuse in weakening and diminishing organs, seem to have been more +potent in their effects. Homologous parts tend to vary in the same way, +and homologous parts tend to cohere. Modifications in hard parts and in +external parts sometimes affect softer and internal parts. When one part +is largely developed, perhaps it tends to draw nourishment from the +adjoining parts; and every part of the structure which can be saved +without detriment to the individual, will be saved. Changes of structure +at an early age will generally affect parts subsequently developed; and +there are very many other correlations of growth, the nature of which we +are utterly unable to understand. Multiple parts are variable in number +and in structure, perhaps arising from such parts not having been +closely specialised to any particular function, so that their +modifications have not been closely checked by natural selection. It is +probably from this same cause that organic beings low in the scale of +nature are more variable than those which have their whole organisation +more specialised, and are higher in the scale. Rudimentary organs, from +being useless, will be disregarded by natural selection, and hence +probably are variable. Specific characters—that is, the characters which +have come to differ since the several species of the same genus branched +off from a common parent—are more variable than generic characters, or +those which have long been inherited, and have not differed within this +same period. In these remarks we have referred to special parts or +organs being still variable, because they have recently varied and thus +come to differ; but we have also seen in the second Chapter that the +same principle applies to the whole individual; for in a district where +many species of any genus are found—that is, where there has been much +former variation and differentiation, or where the manufactory of new +specific forms has been actively at work—there, on an average, we now +find most varieties or incipient species. Secondary sexual characters +are highly variable, and such characters differ much in the species of +the same group. Variability in the same parts of the organisation has +generally been taken advantage of in giving secondary sexual differences +to the sexes of the same species, and specific differences to the +several species of the same genus. Any part or organ developed to an +extraordinary size or in an extraordinary manner, in comparison with the +same part or organ in the allied species, must have gone through an +extraordinary amount of modification since the genus arose; and thus we +can understand why it should often still be variable in a much higher +degree than other parts; for variation is a long-continued and slow +process, and natural selection will in such cases not as yet have had +time to overcome the tendency to further variability and to reversion to +a less modified state. But when a species with any extraordinarily-developed organ has become the parent of many modified -descendants—which on my view must be a very slow process, requiring a long -lapse of time—in this case, natural selection may readily have succeeded in -giving a fixed character to the organ, in however extraordinary a manner it may -be developed. Species inheriting nearly the same constitution from a common -parent and exposed to similar influences will naturally tend to present -analogous variations, and these same species may occasionally revert to some of -the characters of their ancient progenitors. Although new and important -modifications may not arise from reversion and analogous variation, such -modifications will add to the beautiful and harmonious diversity of nature. - -Whatever the cause may be of each slight difference in the offspring from their -parents—and a cause for each must exist—it is the steady accumulation, through -natural selection, of such differences, when beneficial to the individual, that -gives rise to all the more important modifications of structure, by which the -innumerable beings on the face of this earth are enabled to struggle with each -other, and the best adapted to survive. - -CHAPTER VI. -DIFFICULTIES ON THEORY. - -Difficulties on the theory of descent with modification. Transitions. Absence -or rarity of transitional varieties. Transitions in habits of life. Diversified -habits in the same species. Species with habits widely different from those of -their allies. Organs of extreme perfection. Means of transition. Cases of -difficulty. Natura non facit saltum. Organs of small importance. Organs not in -all cases absolutely perfect. The law of Unity of Type and of the Conditions of -Existence embraced by the theory of Natural Selection. - -Long before having arrived at this part of my work, a crowd of difficulties -will have occurred to the reader. Some of them are so grave that to this day I -can never reflect on them without being staggered; but, to the best of my -judgment, the greater number are only apparent, and those that are real are -not, I think, fatal to my theory. - -These difficulties and objections may be classed under the following heads:— - -Firstly, why, if species have descended from other species by insensibly fine -gradations, do we not everywhere see innumerable transitional forms? Why is not -all nature in confusion instead of the species being, as we see them, well -defined? - -Secondly, is it possible that an animal having, for instance, the structure and -habits of a bat, could have been formed by the modification of some animal with -wholly different habits? Can we believe that natural selection could produce, -on the one hand, organs of trifling importance, such as the tail of a giraffe, -which serves as a fly-flapper, and, on the other hand, organs of such wonderful -structure, as the eye, of which we hardly as yet fully understand the -inimitable perfection? - -Thirdly, can instincts be acquired and modified through natural selection? What -shall we say to so marvellous an instinct as that which leads the bee to make -cells, which have practically anticipated the discoveries of profound -mathematicians? - -Fourthly, how can we account for species, when crossed, being sterile and -producing sterile offspring, whereas, when varieties are crossed, their -fertility is unimpaired? - -The two first heads shall be here discussed—Instinct and Hybridism in separate -chapters. - -On the absence or rarity of transitional varieties.—As natural selection acts -solely by the preservation of profitable modifications, each new form will tend -in a fully-stocked country to take the place of, and finally to exterminate, -its own less improved parent or other less-favoured forms with which it comes -into competition. Thus extinction and natural selection will, as we have seen, -go hand in hand. Hence, if we look at each species as descended from some other -unknown form, both the parent and all the transitional varieties will generally -have been exterminated by the very process of formation and perfection of the -new form. - -But, as by this theory innumerable transitional forms must have existed, why do -we not find them embedded in countless numbers in the crust of the earth? It -will be much more convenient to discuss this question in the chapter on the -Imperfection of the geological record; and I will here only state that I -believe the answer mainly lies in the record being incomparably less perfect -than is generally supposed; the imperfection of the record being chiefly due to -organic beings not inhabiting profound depths of the sea, and to their remains -being embedded and preserved to a future age only in masses of sediment -sufficiently thick and extensive to withstand an enormous amount of future -degradation; and such fossiliferous masses can be accumulated only where much -sediment is deposited on the shallow bed of the sea, whilst it slowly subsides. -These contingencies will concur only rarely, and after enormously long -intervals. Whilst the bed of the sea is stationary or is rising, or when very -little sediment is being deposited, there will be blanks in our geological -history. The crust of the earth is a vast museum; but the natural collections -have been made only at intervals of time immensely remote. - -But it may be urged that when several closely-allied species inhabit the same -territory we surely ought to find at the present time many transitional forms. -Let us take a simple case: in travelling from north to south over a continent, -we generally meet at successive intervals with closely allied or representative -species, evidently filling nearly the same place in the natural economy of the -land. These representative species often meet and interlock; and as the one -becomes rarer and rarer, the other becomes more and more frequent, till the one -replaces the other. But if we compare these species where they intermingle, -they are generally as absolutely distinct from each other in every detail of -structure as are specimens taken from the metropolis inhabited by each. By my -theory these allied species have descended from a common parent; and during the -process of modification, each has become adapted to the conditions of life of -its own region, and has supplanted and exterminated its original parent and all -the transitional varieties between its past and present states. Hence we ought -not to expect at the present time to meet with numerous transitional varieties -in each region, though they must have existed there, and may be embedded there -in a fossil condition. But in the intermediate region, having intermediate -conditions of life, why do we not now find closely-linking intermediate -varieties? This difficulty for a long time quite confounded me. But I think it -can be in large part explained. - -In the first place we should be extremely cautious in inferring, because an -area is now continuous, that it has been continuous during a long period. -Geology would lead us to believe that almost every continent has been broken up -into islands even during the later tertiary periods; and in such islands -distinct species might have been separately formed without the possibility of -intermediate varieties existing in the intermediate zones. By changes in the -form of the land and of climate, marine areas now continuous must often have -existed within recent times in a far less continuous and uniform condition than -at present. But I will pass over this way of escaping from the difficulty; for -I believe that many perfectly defined species have been formed on strictly -continuous areas; though I do not doubt that the formerly broken condition of -areas now continuous has played an important part in the formation of new -species, more especially with freely-crossing and wandering animals. +descendants—which on my view must be a very slow process, requiring a +long lapse of time—in this case, natural selection may readily have +succeeded in giving a fixed character to the organ, in however +extraordinary a manner it may be developed. Species inheriting nearly +the same constitution from a common parent and exposed to similar +influences will naturally tend to present analogous variations, and +these same species may occasionally revert to some of the characters of +their ancient progenitors. Although new and important modifications may +not arise from reversion and analogous variation, such modifications +will add to the beautiful and harmonious diversity of nature. + +Whatever the cause may be of each slight difference in the offspring +from their parents—and a cause for each must exist—it is the steady +accumulation, through natural selection, of such differences, when +beneficial to the individual, that gives rise to all the more important +modifications of structure, by which the innumerable beings on the face +of this earth are enabled to struggle with each other, and the best +adapted to survive. + +CHAPTER VI. DIFFICULTIES ON THEORY. + +Difficulties on the theory of descent with modification. Transitions. +Absence or rarity of transitional varieties. Transitions in habits of +life. Diversified habits in the same species. Species with habits widely +different from those of their allies. Organs of extreme perfection. +Means of transition. Cases of difficulty. Natura non facit saltum. +Organs of small importance. Organs not in all cases absolutely perfect. +The law of Unity of Type and of the Conditions of Existence embraced by +the theory of Natural Selection. + +Long before having arrived at this part of my work, a crowd of +difficulties will have occurred to the reader. Some of them are so grave +that to this day I can never reflect on them without being staggered; +but, to the best of my judgment, the greater number are only apparent, +and those that are real are not, I think, fatal to my theory. + +These difficulties and objections may be classed under the following +heads:— + +Firstly, why, if species have descended from other species by insensibly +fine gradations, do we not everywhere see innumerable transitional +forms? Why is not all nature in confusion instead of the species being, +as we see them, well defined? + +Secondly, is it possible that an animal having, for instance, the +structure and habits of a bat, could have been formed by the +modification of some animal with wholly different habits? Can we believe +that natural selection could produce, on the one hand, organs of +trifling importance, such as the tail of a giraffe, which serves as a +fly-flapper, and, on the other hand, organs of such wonderful structure, +as the eye, of which we hardly as yet fully understand the inimitable +perfection? + +Thirdly, can instincts be acquired and modified through natural +selection? What shall we say to so marvellous an instinct as that which +leads the bee to make cells, which have practically anticipated the +discoveries of profound mathematicians? + +Fourthly, how can we account for species, when crossed, being sterile +and producing sterile offspring, whereas, when varieties are crossed, +their fertility is unimpaired? + +The two first heads shall be here discussed—Instinct and Hybridism in +separate chapters. + +On the absence or rarity of transitional varieties.—As natural selection +acts solely by the preservation of profitable modifications, each new +form will tend in a fully-stocked country to take the place of, and +finally to exterminate, its own less improved parent or other +less-favoured forms with which it comes into competition. Thus +extinction and natural selection will, as we have seen, go hand in hand. +Hence, if we look at each species as descended from some other unknown +form, both the parent and all the transitional varieties will generally +have been exterminated by the very process of formation and perfection +of the new form. + +But, as by this theory innumerable transitional forms must have existed, +why do we not find them embedded in countless numbers in the crust of +the earth? It will be much more convenient to discuss this question in +the chapter on the Imperfection of the geological record; and I will +here only state that I believe the answer mainly lies in the record +being incomparably less perfect than is generally supposed; the +imperfection of the record being chiefly due to organic beings not +inhabiting profound depths of the sea, and to their remains being +embedded and preserved to a future age only in masses of sediment +sufficiently thick and extensive to withstand an enormous amount of +future degradation; and such fossiliferous masses can be accumulated +only where much sediment is deposited on the shallow bed of the sea, +whilst it slowly subsides. These contingencies will concur only rarely, +and after enormously long intervals. Whilst the bed of the sea is +stationary or is rising, or when very little sediment is being +deposited, there will be blanks in our geological history. The crust of +the earth is a vast museum; but the natural collections have been made +only at intervals of time immensely remote. + +But it may be urged that when several closely-allied species inhabit the +same territory we surely ought to find at the present time many +transitional forms. Let us take a simple case: in travelling from north +to south over a continent, we generally meet at successive intervals +with closely allied or representative species, evidently filling nearly +the same place in the natural economy of the land. These representative +species often meet and interlock; and as the one becomes rarer and +rarer, the other becomes more and more frequent, till the one replaces +the other. But if we compare these species where they intermingle, they +are generally as absolutely distinct from each other in every detail of +structure as are specimens taken from the metropolis inhabited by each. +By my theory these allied species have descended from a common parent; +and during the process of modification, each has become adapted to the +conditions of life of its own region, and has supplanted and +exterminated its original parent and all the transitional varieties +between its past and present states. Hence we ought not to expect at the +present time to meet with numerous transitional varieties in each +region, though they must have existed there, and may be embedded there +in a fossil condition. But in the intermediate region, having +intermediate conditions of life, why do we not now find closely-linking +intermediate varieties? This difficulty for a long time quite confounded +me. But I think it can be in large part explained. + +In the first place we should be extremely cautious in inferring, because +an area is now continuous, that it has been continuous during a long +period. Geology would lead us to believe that almost every continent +has been broken up into islands even during the later tertiary periods; +and in such islands distinct species might have been separately formed +without the possibility of intermediate varieties existing in the +intermediate zones. By changes in the form of the land and of climate, +marine areas now continuous must often have existed within recent times +in a far less continuous and uniform condition than at present. But I +will pass over this way of escaping from the difficulty; for I believe +that many perfectly defined species have been formed on strictly +continuous areas; though I do not doubt that the formerly broken +condition of areas now continuous has played an important part in the +formation of new species, more especially with freely-crossing and +wandering animals. In looking at species as they are now distributed over a wide area, we -generally find them tolerably numerous over a large territory, then becoming -somewhat abruptly rarer and rarer on the confines, and finally disappearing. -Hence the neutral territory between two representative species is generally -narrow in comparison with the territory proper to each. We see the same fact in -ascending mountains, and sometimes it is quite remarkable how abruptly, as -Alph. De Candolle has observed, a common alpine species disappears. The same -fact has been noticed by Forbes in sounding the depths of the sea with the -dredge. To those who look at climate and the physical conditions of life as the -all-important elements of distribution, these facts ought to cause surprise, as -climate and height or depth graduate away insensibly. But when we bear in mind -that almost every species, even in its metropolis, would increase immensely in -numbers, were it not for other competing species; that nearly all either prey -on or serve as prey for others; in short, that each organic being is either -directly or indirectly related in the most important manner to other organic -beings, we must see that the range of the inhabitants of any country by no -means exclusively depends on insensibly changing physical conditions, but in -large part on the presence of other species, on which it depends, or by which -it is destroyed, or with which it comes into competition; and as these species -are already defined objects (however they may have become so), not blending one -into another by insensible gradations, the range of any one species, depending -as it does on the range of others, will tend to be sharply defined. Moreover, -each species on the confines of its range, where it exists in lessened numbers, -will, during fluctuations in the number of its enemies or of its prey, or in -the seasons, be extremely liable to utter extermination; and thus its -geographical range will come to be still more sharply defined. +generally find them tolerably numerous over a large territory, then +becoming somewhat abruptly rarer and rarer on the confines, and finally +disappearing. Hence the neutral territory between two representative +species is generally narrow in comparison with the territory proper to +each. We see the same fact in ascending mountains, and sometimes it is +quite remarkable how abruptly, as Alph. De Candolle has observed, a +common alpine species disappears. The same fact has been noticed by +Forbes in sounding the depths of the sea with the dredge. To those who +look at climate and the physical conditions of life as the all-important +elements of distribution, these facts ought to cause surprise, as +climate and height or depth graduate away insensibly. But when we bear +in mind that almost every species, even in its metropolis, would +increase immensely in numbers, were it not for other competing species; +that nearly all either prey on or serve as prey for others; in short, +that each organic being is either directly or indirectly related in the +most important manner to other organic beings, we must see that the +range of the inhabitants of any country by no means exclusively depends +on insensibly changing physical conditions, but in large part on the +presence of other species, on which it depends, or by which it is +destroyed, or with which it comes into competition; and as these species +are already defined objects (however they may have become so), not +blending one into another by insensible gradations, the range of any one +species, depending as it does on the range of others, will tend to be +sharply defined. Moreover, each species on the confines of its range, +where it exists in lessened numbers, will, during fluctuations in the +number of its enemies or of its prey, or in the seasons, be extremely +liable to utter extermination; and thus its geographical range will come +to be still more sharply defined. If I am right in believing that allied or representative species, when -inhabiting a continuous area, are generally so distributed that each has a wide -range, with a comparatively narrow neutral territory between them, in which -they become rather suddenly rarer and rarer; then, as varieties do not -essentially differ from species, the same rule will probably apply to both; and -if we in imagination adapt a varying species to a very large area, we shall -have to adapt two varieties to two large areas, and a third variety to a narrow -intermediate zone. The intermediate variety, consequently, will exist in lesser -numbers from inhabiting a narrow and lesser area; and practically, as far as I -can make out, this rule holds good with varieties in a state of nature. I have -met with striking instances of the rule in the case of varieties intermediate -between well-marked varieties in the genus Balanus. And it would appear from -information given me by Mr. Watson, Dr. Asa Gray, and Mr. Wollaston, that -generally when varieties intermediate between two other forms occur, they are -much rarer numerically than the forms which they connect. Now, if we may trust -these facts and inferences, and therefore conclude that varieties linking two -other varieties together have generally existed in lesser numbers than the -forms which they connect, then, I think, we can understand why intermediate -varieties should not endure for very long periods;—why as a general rule they +inhabiting a continuous area, are generally so distributed that each has +a wide range, with a comparatively narrow neutral territory between +them, in which they become rather suddenly rarer and rarer; then, as +varieties do not essentially differ from species, the same rule will +probably apply to both; and if we in imagination adapt a varying species +to a very large area, we shall have to adapt two varieties to two large +areas, and a third variety to a narrow intermediate zone. The +intermediate variety, consequently, will exist in lesser numbers from +inhabiting a narrow and lesser area; and practically, as far as I can +make out, this rule holds good with varieties in a state of nature. I +have met with striking instances of the rule in the case of varieties +intermediate between well-marked varieties in the genus Balanus. And it +would appear from information given me by Mr. Watson, Dr. Asa Gray, and +Mr. Wollaston, that generally when varieties intermediate between two +other forms occur, they are much rarer numerically than the forms which +they connect. Now, if we may trust these facts and inferences, and +therefore conclude that varieties linking two other varieties together +have generally existed in lesser numbers than the forms which they +connect, then, I think, we can understand why intermediate varieties +should not endure for very long periods;—why as a general rule they should be exterminated and disappear, sooner than the forms which they originally linked together. -For any form existing in lesser numbers would, as already remarked, run a -greater chance of being exterminated than one existing in large numbers; and in -this particular case the intermediate form would be eminently liable to the -inroads of closely allied forms existing on both sides of it. But a far more -important consideration, as I believe, is that, during the process of further -modification, by which two varieties are supposed on my theory to be converted -and perfected into two distinct species, the two which exist in larger numbers -from inhabiting larger areas, will have a great advantage over the intermediate -variety, which exists in smaller numbers in a narrow and intermediate zone. For -forms existing in larger numbers will always have a better chance, within any -given period, of presenting further favourable variations for natural selection -to seize on, than will the rarer forms which exist in lesser numbers. Hence, -the more common forms, in the race for life, will tend to beat and supplant the -less common forms, for these will be more slowly modified and improved. It is -the same principle which, as I believe, accounts for the common species in each -country, as shown in the second chapter, presenting on an average a greater -number of well-marked varieties than do the rarer species. I may illustrate -what I mean by supposing three varieties of sheep to be kept, one adapted to an -extensive mountainous region; a second to a comparatively narrow, hilly tract; -and a third to wide plains at the base; and that the inhabitants are all trying -with equal steadiness and skill to improve their stocks by selection; the -chances in this case will be strongly in favour of the great holders on the -mountains or on the plains improving their breeds more quickly than the small -holders on the intermediate narrow, hilly tract; and consequently the improved -mountain or plain breed will soon take the place of the less improved hill -breed; and thus the two breeds, which originally existed in greater numbers, -will come into close contact with each other, without the interposition of the -supplanted, intermediate hill-variety. - -To sum up, I believe that species come to be tolerably well-defined objects, -and do not at any one period present an inextricable chaos of varying and -intermediate links: firstly, because new varieties are very slowly formed, for -variation is a very slow process, and natural selection can do nothing until -favourable variations chance to occur, and until a place in the natural polity -of the country can be better filled by some modification of some one or more of -its inhabitants. And such new places will depend on slow changes of climate, or -on the occasional immigration of new inhabitants, and, probably, in a still -more important degree, on some of the old inhabitants becoming slowly modified, -with the new forms thus produced and the old ones acting and reacting on each -other. So that, in any one region and at any one time, we ought only to see a -few species presenting slight modifications of structure in some degree -permanent; and this assuredly we do see. - -Secondly, areas now continuous must often have existed within the recent period -in isolated portions, in which many forms, more especially amongst the classes -which unite for each birth and wander much, may have separately been rendered -sufficiently distinct to rank as representative species. In this case, -intermediate varieties between the several representative species and their -common parent, must formerly have existed in each broken portion of the land, -but these links will have been supplanted and exterminated during the process -of natural selection, so that they will no longer exist in a living state. - -Thirdly, when two or more varieties have been formed in different portions of a -strictly continuous area, intermediate varieties will, it is probable, at first -have been formed in the intermediate zones, but they will generally have had a -short duration. For these intermediate varieties will, from reasons already -assigned (namely from what we know of the actual distribution of closely allied -or representative species, and likewise of acknowledged varieties), exist in -the intermediate zones in lesser numbers than the varieties which they tend to -connect. From this cause alone the intermediate varieties will be liable to -accidental extermination; and during the process of further modification -through natural selection, they will almost certainly be beaten and supplanted -by the forms which they connect; for these from existing in greater numbers -will, in the aggregate, present more variation, and thus be further improved -through natural selection and gain further advantages. - -Lastly, looking not to any one time, but to all time, if my theory be true, -numberless intermediate varieties, linking most closely all the species of the -same group together, must assuredly have existed; but the very process of -natural selection constantly tends, as has been so often remarked, to -exterminate the parent forms and the intermediate links. Consequently evidence -of their former existence could be found only amongst fossil remains, which are -preserved, as we shall in a future chapter attempt to show, in an extremely -imperfect and intermittent record. +For any form existing in lesser numbers would, as already remarked, run +a greater chance of being exterminated than one existing in large +numbers; and in this particular case the intermediate form would be +eminently liable to the inroads of closely allied forms existing on both +sides of it. But a far more important consideration, as I believe, is +that, during the process of further modification, by which two varieties +are supposed on my theory to be converted and perfected into two +distinct species, the two which exist in larger numbers from inhabiting +larger areas, will have a great advantage over the intermediate variety, +which exists in smaller numbers in a narrow and intermediate zone. For +forms existing in larger numbers will always have a better chance, +within any given period, of presenting further favourable variations for +natural selection to seize on, than will the rarer forms which exist in +lesser numbers. Hence, the more common forms, in the race for life, will +tend to beat and supplant the less common forms, for these will be more +slowly modified and improved. It is the same principle which, as I +believe, accounts for the common species in each country, as shown in +the second chapter, presenting on an average a greater number of +well-marked varieties than do the rarer species. I may illustrate what I +mean by supposing three varieties of sheep to be kept, one adapted to an +extensive mountainous region; a second to a comparatively narrow, hilly +tract; and a third to wide plains at the base; and that the inhabitants +are all trying with equal steadiness and skill to improve their stocks +by selection; the chances in this case will be strongly in favour of the +great holders on the mountains or on the plains improving their breeds +more quickly than the small holders on the intermediate narrow, hilly +tract; and consequently the improved mountain or plain breed will soon +take the place of the less improved hill breed; and thus the two breeds, +which originally existed in greater numbers, will come into close +contact with each other, without the interposition of the supplanted, +intermediate hill-variety. + +To sum up, I believe that species come to be tolerably well-defined +objects, and do not at any one period present an inextricable chaos of +varying and intermediate links: firstly, because new varieties are very +slowly formed, for variation is a very slow process, and natural +selection can do nothing until favourable variations chance to occur, +and until a place in the natural polity of the country can be better +filled by some modification of some one or more of its inhabitants. And +such new places will depend on slow changes of climate, or on the +occasional immigration of new inhabitants, and, probably, in a still +more important degree, on some of the old inhabitants becoming slowly +modified, with the new forms thus produced and the old ones acting and +reacting on each other. So that, in any one region and at any one time, +we ought only to see a few species presenting slight modifications of +structure in some degree permanent; and this assuredly we do see. + +Secondly, areas now continuous must often have existed within the recent +period in isolated portions, in which many forms, more especially +amongst the classes which unite for each birth and wander much, may have +separately been rendered sufficiently distinct to rank as representative +species. In this case, intermediate varieties between the several +representative species and their common parent, must formerly have +existed in each broken portion of the land, but these links will have +been supplanted and exterminated during the process of natural +selection, so that they will no longer exist in a living state. + +Thirdly, when two or more varieties have been formed in different +portions of a strictly continuous area, intermediate varieties will, it +is probable, at first have been formed in the intermediate zones, but +they will generally have had a short duration. For these intermediate +varieties will, from reasons already assigned (namely from what we know +of the actual distribution of closely allied or representative species, +and likewise of acknowledged varieties), exist in the intermediate zones +in lesser numbers than the varieties which they tend to connect. From +this cause alone the intermediate varieties will be liable to accidental +extermination; and during the process of further modification through +natural selection, they will almost certainly be beaten and supplanted +by the forms which they connect; for these from existing in greater +numbers will, in the aggregate, present more variation, and thus be +further improved through natural selection and gain further advantages. + +Lastly, looking not to any one time, but to all time, if my theory be +true, numberless intermediate varieties, linking most closely all the +species of the same group together, must assuredly have existed; but the +very process of natural selection constantly tends, as has been so often +remarked, to exterminate the parent forms and the intermediate links. +Consequently evidence of their former existence could be found only +amongst fossil remains, which are preserved, as we shall in a future +chapter attempt to show, in an extremely imperfect and intermittent +record. On the origin and transitions of organic beings with peculiar habits and -structure.—It has been asked by the opponents of such views as I hold, how, for -instance, a land carnivorous animal could have been converted into one with -aquatic habits; for how could the animal in its transitional state have -subsisted? It would be easy to show that within the same group carnivorous -animals exist having every intermediate grade between truly aquatic and -strictly terrestrial habits; and as each exists by a struggle for life, it is -clear that each is well adapted in its habits to its place in nature. Look at -the Mustela vison of North America, which has webbed feet and which resembles -an otter in its fur, short legs, and form of tail; during summer this animal -dives for and preys on fish, but during the long winter it leaves the frozen -waters, and preys like other polecats on mice and land animals. If a different -case had been taken, and it had been asked how an insectivorous quadruped could -possibly have been converted into a flying bat, the question would have been -far more difficult, and I could have given no answer. Yet I think such -difficulties have very little weight. - -Here, as on other occasions, I lie under a heavy disadvantage, for out of the -many striking cases which I have collected, I can give only one or two -instances of transitional habits and structures in closely allied species of -the same genus; and of diversified habits, either constant or occasional, in -the same species. And it seems to me that nothing less than a long list of such -cases is sufficient to lessen the difficulty in any particular case like that -of the bat. - -Look at the family of squirrels; here we have the finest gradation from animals -with their tails only slightly flattened, and from others, as Sir J. Richardson -has remarked, with the posterior part of their bodies rather wide and with the -skin on their flanks rather full, to the so-called flying squirrels; and flying -squirrels have their limbs and even the base of the tail united by a broad -expanse of skin, which serves as a parachute and allows them to glide through -the air to an astonishing distance from tree to tree. We cannot doubt that each -structure is of use to each kind of squirrel in its own country, by enabling it -to escape birds or beasts of prey, or to collect food more quickly, or, as -there is reason to believe, by lessening the danger from occasional falls. But -it does not follow from this fact that the structure of each squirrel is the -best that it is possible to conceive under all natural conditions. Let the -climate and vegetation change, let other competing rodents or new beasts of -prey immigrate, or old ones become modified, and all analogy would lead us to -believe that some at least of the squirrels would decrease in numbers or become -exterminated, unless they also became modified and improved in structure in a -corresponding manner. Therefore, I can see no difficulty, more especially under -changing conditions of life, in the continued preservation of individuals with -fuller and fuller flank-membranes, each modification being useful, each being -propagated, until by the accumulated effects of this process of natural -selection, a perfect so-called flying squirrel was produced. - -Now look at the Galeopithecus or flying lemur, which formerly was falsely -ranked amongst bats. It has an extremely wide flank-membrane, stretching from -the corners of the jaw to the tail, and including the limbs and the elongated -fingers: the flank membrane is, also, furnished with an extensor muscle. -Although no graduated links of structure, fitted for gliding through the air, -now connect the Galeopithecus with the other Lemuridæ, yet I can see no -difficulty in supposing that such links formerly existed, and that each had -been formed by the same steps as in the case of the less perfectly gliding -squirrels; and that each grade of structure had been useful to its possessor. -Nor can I see any insuperable difficulty in further believing it possible that -the membrane-connected fingers and fore-arm of the Galeopithecus might be -greatly lengthened by natural selection; and this, as far as the organs of -flight are concerned, would convert it into a bat. In bats which have the -wing-membrane extended from the top of the shoulder to the tail, including the -hind-legs, we perhaps see traces of an apparatus originally constructed for -gliding through the air rather than for flight. - -If about a dozen genera of birds had become extinct or were unknown, who would -have ventured to have surmised that birds might have existed which used their -wings solely as flappers, like the logger-headed duck (Micropterus of Eyton); -as fins in the water and front legs on the land, like the penguin; as sails, -like the ostrich; and functionally for no purpose, like the Apteryx. Yet the -structure of each of these birds is good for it, under the conditions of life -to which it is exposed, for each has to live by a struggle; but it is not -necessarily the best possible under all possible conditions. It must not be -inferred from these remarks that any of the grades of wing-structure here -alluded to, which perhaps may all have resulted from disuse, indicate the -natural steps by which birds have acquired their perfect power of flight; but +structure.—It has been asked by the opponents of such views as I hold, +how, for instance, a land carnivorous animal could have been converted +into one with aquatic habits; for how could the animal in its +transitional state have subsisted? It would be easy to show that within +the same group carnivorous animals exist having every intermediate grade +between truly aquatic and strictly terrestrial habits; and as each +exists by a struggle for life, it is clear that each is well adapted in +its habits to its place in nature. Look at the Mustela vison of North +America, which has webbed feet and which resembles an otter in its fur, +short legs, and form of tail; during summer this animal dives for and +preys on fish, but during the long winter it leaves the frozen waters, +and preys like other polecats on mice and land animals. If a different +case had been taken, and it had been asked how an insectivorous +quadruped could possibly have been converted into a flying bat, the +question would have been far more difficult, and I could have given no +answer. Yet I think such difficulties have very little weight. + +Here, as on other occasions, I lie under a heavy disadvantage, for out +of the many striking cases which I have collected, I can give only one +or two instances of transitional habits and structures in closely allied +species of the same genus; and of diversified habits, either constant or +occasional, in the same species. And it seems to me that nothing less +than a long list of such cases is sufficient to lessen the difficulty in +any particular case like that of the bat. + +Look at the family of squirrels; here we have the finest gradation from +animals with their tails only slightly flattened, and from others, as +Sir J. Richardson has remarked, with the posterior part of their bodies +rather wide and with the skin on their flanks rather full, to the +so-called flying squirrels; and flying squirrels have their limbs and +even the base of the tail united by a broad expanse of skin, which +serves as a parachute and allows them to glide through the air to an +astonishing distance from tree to tree. We cannot doubt that each +structure is of use to each kind of squirrel in its own country, by +enabling it to escape birds or beasts of prey, or to collect food more +quickly, or, as there is reason to believe, by lessening the danger from +occasional falls. But it does not follow from this fact that the +structure of each squirrel is the best that it is possible to conceive +under all natural conditions. Let the climate and vegetation change, let +other competing rodents or new beasts of prey immigrate, or old ones +become modified, and all analogy would lead us to believe that some at +least of the squirrels would decrease in numbers or become exterminated, +unless they also became modified and improved in structure in a +corresponding manner. Therefore, I can see no difficulty, more +especially under changing conditions of life, in the continued +preservation of individuals with fuller and fuller flank-membranes, each +modification being useful, each being propagated, until by the +accumulated effects of this process of natural selection, a perfect +so-called flying squirrel was produced. + +Now look at the Galeopithecus or flying lemur, which formerly was +falsely ranked amongst bats. It has an extremely wide flank-membrane, +stretching from the corners of the jaw to the tail, and including the +limbs and the elongated fingers: the flank membrane is, also, furnished +with an extensor muscle. Although no graduated links of structure, +fitted for gliding through the air, now connect the Galeopithecus with +the other Lemuridæ, yet I can see no difficulty in supposing that such +links formerly existed, and that each had been formed by the same steps +as in the case of the less perfectly gliding squirrels; and that each +grade of structure had been useful to its possessor. Nor can I see any +insuperable difficulty in further believing it possible that the +membrane-connected fingers and fore-arm of the Galeopithecus might be +greatly lengthened by natural selection; and this, as far as the organs +of flight are concerned, would convert it into a bat. In bats which have +the wing-membrane extended from the top of the shoulder to the tail, +including the hind-legs, we perhaps see traces of an apparatus +originally constructed for gliding through the air rather than for +flight. + +If about a dozen genera of birds had become extinct or were unknown, who +would have ventured to have surmised that birds might have existed which +used their wings solely as flappers, like the logger-headed duck +(Micropterus of Eyton); as fins in the water and front legs on the land, +like the penguin; as sails, like the ostrich; and functionally for no +purpose, like the Apteryx. Yet the structure of each of these birds is +good for it, under the conditions of life to which it is exposed, for +each has to live by a struggle; but it is not necessarily the best +possible under all possible conditions. It must not be inferred from +these remarks that any of the grades of wing-structure here alluded to, +which perhaps may all have resulted from disuse, indicate the natural +steps by which birds have acquired their perfect power of flight; but they serve, at least, to show what diversified means of transition are possible. -Seeing that a few members of such water-breathing classes as the Crustacea and -Mollusca are adapted to live on the land, and seeing that we have flying birds -and mammals, flying insects of the most diversified types, and formerly had -flying reptiles, it is conceivable that flying-fish, which now glide far -through the air, slightly rising and turning by the aid of their fluttering -fins, might have been modified into perfectly winged animals. If this had been -effected, who would have ever imagined that in an early transitional state they -had been inhabitants of the open ocean, and had used their incipient organs of -flight exclusively, as far as we know, to escape being devoured by other fish? - -When we see any structure highly perfected for any particular habit, as the -wings of a bird for flight, we should bear in mind that animals displaying -early transitional grades of the structure will seldom continue to exist to the -present day, for they will have been supplanted by the very process of -perfection through natural selection. Furthermore, we may conclude that -transitional grades between structures fitted for very different habits of life -will rarely have been developed at an early period in great numbers and under -many subordinate forms. Thus, to return to our imaginary illustration of the -flying-fish, it does not seem probable that fishes capable of true flight would -have been developed under many subordinate forms, for taking prey of many kinds -in many ways, on the land and in the water, until their organs of flight had -come to a high stage of perfection, so as to have given them a decided -advantage over other animals in the battle for life. Hence the chance of -discovering species with transitional grades of structure in a fossil condition -will always be less, from their having existed in lesser numbers, than in the -case of species with fully developed structures. - -I will now give two or three instances of diversified and of changed habits in -the individuals of the same species. When either case occurs, it would be easy -for natural selection to fit the animal, by some modification of its structure, -for its changed habits, or exclusively for one of its several different habits. -But it is difficult to tell, and immaterial for us, whether habits generally -change first and structure afterwards; or whether slight modifications of -structure lead to changed habits; both probably often change almost -simultaneously. Of cases of changed habits it will suffice merely to allude to -that of the many British insects which now feed on exotic plants, or -exclusively on artificial substances. Of diversified habits innumerable -instances could be given: I have often watched a tyrant flycatcher (Saurophagus -sulphuratus) in South America, hovering over one spot and then proceeding to -another, like a kestrel, and at other times standing stationary on the margin -of water, and then dashing like a kingfisher at a fish. In our own country the -larger titmouse (Parus major) may be seen climbing branches, almost like a -creeper; it often, like a shrike, kills small birds by blows on the head; and I -have many times seen and heard it hammering the seeds of the yew on a branch, -and thus breaking them like a nuthatch. In North America the black bear was -seen by Hearne swimming for hours with widely open mouth, thus catching, like a -whale, insects in the water. Even in so extreme a case as this, if the supply -of insects were constant, and if better adapted competitors did not already -exist in the country, I can see no difficulty in a race of bears being -rendered, by natural selection, more and more aquatic in their structure and -habits, with larger and larger mouths, till a creature was produced as -monstrous as a whale. - -As we sometimes see individuals of a species following habits widely different -from those both of their own species and of the other species of the same -genus, we might expect, on my theory, that such individuals would occasionally -have given rise to new species, having anomalous habits, and with their -structure either slightly or considerably modified from that of their proper -type. And such instances do occur in nature. Can a more striking instance of -adaptation be given than that of a woodpecker for climbing trees and for -seizing insects in the chinks of the bark? Yet in North America there are -woodpeckers which feed largely on fruit, and others with elongated wings which -chase insects on the wing; and on the plains of La Plata, where not a tree -grows, there is a woodpecker, which in every essential part of its -organisation, even in its colouring, in the harsh tone of its voice, and -undulatory flight, told me plainly of its close blood-relationship to our -common species; yet it is a woodpecker which never climbs a tree! - -Petrels are the most aërial and oceanic of birds, yet in the quiet Sounds of -Tierra del Fuego, the Puffinuria berardi, in its general habits, in its -astonishing power of diving, its manner of swimming, and of flying when -unwillingly it takes flight, would be mistaken by any one for an auk or grebe; -nevertheless, it is essentially a petrel, but with many parts of its -organisation profoundly modified. On the other hand, the acutest observer by -examining the dead body of the water-ouzel would never have suspected its -sub-aquatic habits; yet this anomalous member of the strictly terrestrial -thrush family wholly subsists by diving,—grasping the stones with its feet and -using its wings under water. +Seeing that a few members of such water-breathing classes as the +Crustacea and Mollusca are adapted to live on the land, and seeing that +we have flying birds and mammals, flying insects of the most diversified +types, and formerly had flying reptiles, it is conceivable that +flying-fish, which now glide far through the air, slightly rising and +turning by the aid of their fluttering fins, might have been modified +into perfectly winged animals. If this had been effected, who would have +ever imagined that in an early transitional state they had been +inhabitants of the open ocean, and had used their incipient organs of +flight exclusively, as far as we know, to escape being devoured by other +fish? + +When we see any structure highly perfected for any particular habit, as +the wings of a bird for flight, we should bear in mind that animals +displaying early transitional grades of the structure will seldom +continue to exist to the present day, for they will have been supplanted +by the very process of perfection through natural selection. +Furthermore, we may conclude that transitional grades between structures +fitted for very different habits of life will rarely have been developed +at an early period in great numbers and under many subordinate forms. +Thus, to return to our imaginary illustration of the flying-fish, it +does not seem probable that fishes capable of true flight would have +been developed under many subordinate forms, for taking prey of many +kinds in many ways, on the land and in the water, until their organs of +flight had come to a high stage of perfection, so as to have given them +a decided advantage over other animals in the battle for life. Hence the +chance of discovering species with transitional grades of structure in a +fossil condition will always be less, from their having existed in +lesser numbers, than in the case of species with fully developed +structures. + +I will now give two or three instances of diversified and of changed +habits in the individuals of the same species. When either case occurs, +it would be easy for natural selection to fit the animal, by some +modification of its structure, for its changed habits, or exclusively +for one of its several different habits. But it is difficult to tell, +and immaterial for us, whether habits generally change first and +structure afterwards; or whether slight modifications of structure lead +to changed habits; both probably often change almost simultaneously. Of +cases of changed habits it will suffice merely to allude to that of the +many British insects which now feed on exotic plants, or exclusively on +artificial substances. Of diversified habits innumerable instances could +be given: I have often watched a tyrant flycatcher (Saurophagus +sulphuratus) in South America, hovering over one spot and then +proceeding to another, like a kestrel, and at other times standing +stationary on the margin of water, and then dashing like a kingfisher at +a fish. In our own country the larger titmouse (Parus major) may be seen +climbing branches, almost like a creeper; it often, like a shrike, kills +small birds by blows on the head; and I have many times seen and heard +it hammering the seeds of the yew on a branch, and thus breaking them +like a nuthatch. In North America the black bear was seen by Hearne +swimming for hours with widely open mouth, thus catching, like a whale, +insects in the water. Even in so extreme a case as this, if the supply +of insects were constant, and if better adapted competitors did not +already exist in the country, I can see no difficulty in a race of bears +being rendered, by natural selection, more and more aquatic in their +structure and habits, with larger and larger mouths, till a creature was +produced as monstrous as a whale. + +As we sometimes see individuals of a species following habits widely +different from those both of their own species and of the other species +of the same genus, we might expect, on my theory, that such individuals +would occasionally have given rise to new species, having anomalous +habits, and with their structure either slightly or considerably +modified from that of their proper type. And such instances do occur in +nature. Can a more striking instance of adaptation be given than that of +a woodpecker for climbing trees and for seizing insects in the chinks of +the bark? Yet in North America there are woodpeckers which feed largely +on fruit, and others with elongated wings which chase insects on the +wing; and on the plains of La Plata, where not a tree grows, there is a +woodpecker, which in every essential part of its organisation, even in +its colouring, in the harsh tone of its voice, and undulatory flight, +told me plainly of its close blood-relationship to our common species; +yet it is a woodpecker which never climbs a tree! + +Petrels are the most aërial and oceanic of birds, yet in the quiet +Sounds of Tierra del Fuego, the Puffinuria berardi, in its general +habits, in its astonishing power of diving, its manner of swimming, and +of flying when unwillingly it takes flight, would be mistaken by any one +for an auk or grebe; nevertheless, it is essentially a petrel, but with +many parts of its organisation profoundly modified. On the other hand, +the acutest observer by examining the dead body of the water-ouzel would +never have suspected its sub-aquatic habits; yet this anomalous member +of the strictly terrestrial thrush family wholly subsists by +diving,—grasping the stones with its feet and using its wings under +water. He who believes that each being has been created as we now see it, must -occasionally have felt surprise when he has met with an animal having habits -and structure not at all in agreement. What can be plainer than that the webbed -feet of ducks and geese are formed for swimming? yet there are upland geese -with webbed feet which rarely or never go near the water; and no one except -Audubon has seen the frigate-bird, which has all its four toes webbed, alight -on the surface of the sea. On the other hand, grebes and coots are eminently -aquatic, although their toes are only bordered by membrane. What seems plainer -than that the long toes of grallatores are formed for walking over swamps and -floating plants, yet the water-hen is nearly as aquatic as the coot; and the -landrail nearly as terrestrial as the quail or partridge. In such cases, and -many others could be given, habits have changed without a corresponding change -of structure. The webbed feet of the upland goose may be said to have become -rudimentary in function, though not in structure. In the frigate-bird, the -deeply-scooped membrane between the toes shows that structure has begun to -change. - -He who believes in separate and innumerable acts of creation will say, that in -these cases it has pleased the Creator to cause a being of one type to take the -place of one of another type; but this seems to me only restating the fact in -dignified language. He who believes in the struggle for existence and in the -principle of natural selection, will acknowledge that every organic being is -constantly endeavouring to increase in numbers; and that if any one being vary -ever so little, either in habits or structure, and thus gain an advantage over -some other inhabitant of the country, it will seize on the place of that -inhabitant, however different it may be from its own place. Hence it will cause -him no surprise that there should be geese and frigate-birds with webbed feet, -either living on the dry land or most rarely alighting on the water; that there -should be long-toed corncrakes living in meadows instead of in swamps; that -there should be woodpeckers where not a tree grows; that there should be diving -thrushes, and petrels with the habits of auks. - -Organs of extreme perfection and complication.—To suppose that the eye, with -all its inimitable contrivances for adjusting the focus to different distances, -for admitting different amounts of light, and for the correction of spherical -and chromatic aberration, could have been formed by natural selection, seems, I -freely confess, absurd in the highest possible degree. Yet reason tells me, -that if numerous gradations from a perfect and complex eye to one very -imperfect and simple, each grade being useful to its possessor, can be shown to -exist; if further, the eye does vary ever so slightly, and the variations be -inherited, which is certainly the case; and if any variation or modification in -the organ be ever useful to an animal under changing conditions of life, then -the difficulty of believing that a perfect and complex eye could be formed by -natural selection, though insuperable by our imagination, can hardly be -considered real. How a nerve comes to be sensitive to light, hardly concerns us -more than how life itself first originated; but I may remark that several facts -make me suspect that any sensitive nerve may be rendered sensitive to light, -and likewise to those coarser vibrations of the air which produce sound. +occasionally have felt surprise when he has met with an animal having +habits and structure not at all in agreement. What can be plainer than +that the webbed feet of ducks and geese are formed for swimming? yet +there are upland geese with webbed feet which rarely or never go near +the water; and no one except Audubon has seen the frigate-bird, which +has all its four toes webbed, alight on the surface of the sea. On the +other hand, grebes and coots are eminently aquatic, although their toes +are only bordered by membrane. What seems plainer than that the long +toes of grallatores are formed for walking over swamps and floating +plants, yet the water-hen is nearly as aquatic as the coot; and the +landrail nearly as terrestrial as the quail or partridge. In such cases, +and many others could be given, habits have changed without a +corresponding change of structure. The webbed feet of the upland goose +may be said to have become rudimentary in function, though not in +structure. In the frigate-bird, the deeply-scooped membrane between the +toes shows that structure has begun to change. + +He who believes in separate and innumerable acts of creation will say, +that in these cases it has pleased the Creator to cause a being of one +type to take the place of one of another type; but this seems to me only +restating the fact in dignified language. He who believes in the +struggle for existence and in the principle of natural selection, will +acknowledge that every organic being is constantly endeavouring to +increase in numbers; and that if any one being vary ever so little, +either in habits or structure, and thus gain an advantage over some +other inhabitant of the country, it will seize on the place of that +inhabitant, however different it may be from its own place. Hence it +will cause him no surprise that there should be geese and frigate-birds +with webbed feet, either living on the dry land or most rarely alighting +on the water; that there should be long-toed corncrakes living in +meadows instead of in swamps; that there should be woodpeckers where not +a tree grows; that there should be diving thrushes, and petrels with the +habits of auks. + +Organs of extreme perfection and complication.—To suppose that the eye, +with all its inimitable contrivances for adjusting the focus to +different distances, for admitting different amounts of light, and for +the correction of spherical and chromatic aberration, could have been +formed by natural selection, seems, I freely confess, absurd in the +highest possible degree. Yet reason tells me, that if numerous +gradations from a perfect and complex eye to one very imperfect and +simple, each grade being useful to its possessor, can be shown to exist; +if further, the eye does vary ever so slightly, and the variations be +inherited, which is certainly the case; and if any variation or +modification in the organ be ever useful to an animal under changing +conditions of life, then the difficulty of believing that a perfect and +complex eye could be formed by natural selection, though insuperable by +our imagination, can hardly be considered real. How a nerve comes to be +sensitive to light, hardly concerns us more than how life itself first +originated; but I may remark that several facts make me suspect that any +sensitive nerve may be rendered sensitive to light, and likewise to +those coarser vibrations of the air which produce sound. In looking for the gradations by which an organ in any species has been -perfected, we ought to look exclusively to its lineal ancestors; but this is -scarcely ever possible, and we are forced in each case to look to species of -the same group, that is to the collateral descendants from the same original -parent-form, in order to see what gradations are possible, and for the chance -of some gradations having been transmitted from the earlier stages of descent, -in an unaltered or little altered condition. Amongst existing Vertebrata, we -find but a small amount of gradation in the structure of the eye, and from -fossil species we can learn nothing on this head. In this great class we should -probably have to descend far beneath the lowest known fossiliferous stratum to +perfected, we ought to look exclusively to its lineal ancestors; but +this is scarcely ever possible, and we are forced in each case to look +to species of the same group, that is to the collateral descendants from +the same original parent-form, in order to see what gradations are +possible, and for the chance of some gradations having been transmitted +from the earlier stages of descent, in an unaltered or little altered +condition. Amongst existing Vertebrata, we find but a small amount of +gradation in the structure of the eye, and from fossil species we can +learn nothing on this head. In this great class we should probably have +to descend far beneath the lowest known fossiliferous stratum to discover the earlier stages, by which the eye has been perfected. -In the Articulata we can commence a series with an optic nerve merely coated -with pigment, and without any other mechanism; and from this low stage, -numerous gradations of structure, branching off in two fundamentally different -lines, can be shown to exist, until we reach a moderately high stage of -perfection. In certain crustaceans, for instance, there is a double cornea, the -inner one divided into facets, within each of which there is a lens-shaped -swelling. In other crustaceans the transparent cones which are coated by -pigment, and which properly act only by excluding lateral pencils of light, are -convex at their upper ends and must act by convergence; and at their lower ends -there seems to be an imperfect vitreous substance. With these facts, here far -too briefly and imperfectly given, which show that there is much graduated -diversity in the eyes of living crustaceans, and bearing in mind how small the -number of living animals is in proportion to those which have become extinct, I -can see no very great difficulty (not more than in the case of many other -structures) in believing that natural selection has converted the simple -apparatus of an optic nerve merely coated with pigment and invested by -transparent membrane, into an optical instrument as perfect as is possessed by -any member of the great Articulate class. - -He who will go thus far, if he find on finishing this treatise that large -bodies of facts, otherwise inexplicable, can be explained by the theory of -descent, ought not to hesitate to go further, and to admit that a structure -even as perfect as the eye of an eagle might be formed by natural selection, -although in this case he does not know any of the transitional grades. His -reason ought to conquer his imagination; though I have felt the difficulty far -too keenly to be surprised at any degree of hesitation in extending the -principle of natural selection to such startling lengths. - -It is scarcely possible to avoid comparing the eye to a telescope. We know that -this instrument has been perfected by the long-continued efforts of the highest -human intellects; and we naturally infer that the eye has been formed by a -somewhat analogous process. But may not this inference be presumptuous? Have we -any right to assume that the Creator works by intellectual powers like those of -man? If we must compare the eye to an optical instrument, we ought in -imagination to take a thick layer of transparent tissue, with a nerve sensitive -to light beneath, and then suppose every part of this layer to be continually -changing slowly in density, so as to separate into layers of different -densities and thicknesses, placed at different distances from each other, and -with the surfaces of each layer slowly changing in form. Further we must -suppose that there is a power always intently watching each slight accidental -alteration in the transparent layers; and carefully selecting each alteration -which, under varied circumstances, may in any way, or in any degree, tend to -produce a distincter image. We must suppose each new state of the instrument to -be multiplied by the million; and each to be preserved till a better be -produced, and then the old ones to be destroyed. In living bodies, variation -will cause the slight alterations, generation will multiply them almost -infinitely, and natural selection will pick out with unerring skill each -improvement. Let this process go on for millions on millions of years; and -during each year on millions of individuals of many kinds; and may we not -believe that a living optical instrument might thus be formed as superior to -one of glass, as the works of the Creator are to those of man? - -If it could be demonstrated that any complex organ existed, which could not -possibly have been formed by numerous, successive, slight modifications, my -theory would absolutely break down. But I can find out no such case. No doubt -many organs exist of which we do not know the transitional grades, more -especially if we look to much-isolated species, round which, according to my -theory, there has been much extinction. Or again, if we look to an organ common -to all the members of a large class, for in this latter case the organ must -have been first formed at an extremely remote period, since which all the many -members of the class have been developed; and in order to discover the early -transitional grades through which the organ has passed, we should have to look -to very ancient ancestral forms, long since become extinct. - -We should be extremely cautious in concluding that an organ could not have been -formed by transitional gradations of some kind. Numerous cases could be given -amongst the lower animals of the same organ performing at the same time wholly -distinct functions; thus the alimentary canal respires, digests, and excretes -in the larva of the dragon-fly and in the fish Cobites. In the Hydra, the -animal may be turned inside out, and the exterior surface will then digest and -the stomach respire. In such cases natural selection might easily specialise, -if any advantage were thus gained, a part or organ, which had performed two -functions, for one function alone, and thus wholly change its nature by -insensible steps. Two distinct organs sometimes perform simultaneously the same -function in the same individual; to give one instance, there are fish with -gills or branchiæ that breathe the air dissolved in the water, at the same time -that they breathe free air in their swimbladders, this latter organ having a -ductus pneumaticus for its supply, and being divided by highly vascular -partitions. In these cases, one of the two organs might with ease be modified -and perfected so as to perform all the work by itself, being aided during the -process of modification by the other organ; and then this other organ might be -modified for some other and quite distinct purpose, or be quite obliterated. - -The illustration of the swimbladder in fishes is a good one, because it shows -us clearly the highly important fact that an organ originally constructed for -one purpose, namely flotation, may be converted into one for a wholly different -purpose, namely respiration. The swimbladder has, also, been worked in as an -accessory to the auditory organs of certain fish, or, for I do not know which -view is now generally held, a part of the auditory apparatus has been worked in -as a complement to the swimbladder. All physiologists admit that the -swimbladder is homologous, or “ideally similar,” in position and structure with -the lungs of the higher vertebrate animals: hence there seems to me to be no -great difficulty in believing that natural selection has actually converted a +In the Articulata we can commence a series with an optic nerve merely +coated with pigment, and without any other mechanism; and from this low +stage, numerous gradations of structure, branching off in two +fundamentally different lines, can be shown to exist, until we reach a +moderately high stage of perfection. In certain crustaceans, for +instance, there is a double cornea, the inner one divided into facets, +within each of which there is a lens-shaped swelling. In other +crustaceans the transparent cones which are coated by pigment, and which +properly act only by excluding lateral pencils of light, are convex at +their upper ends and must act by convergence; and at their lower ends +there seems to be an imperfect vitreous substance. With these facts, +here far too briefly and imperfectly given, which show that there is +much graduated diversity in the eyes of living crustaceans, and bearing +in mind how small the number of living animals is in proportion to those +which have become extinct, I can see no very great difficulty (not more +than in the case of many other structures) in believing that natural +selection has converted the simple apparatus of an optic nerve merely +coated with pigment and invested by transparent membrane, into an +optical instrument as perfect as is possessed by any member of the great +Articulate class. + +He who will go thus far, if he find on finishing this treatise that +large bodies of facts, otherwise inexplicable, can be explained by the +theory of descent, ought not to hesitate to go further, and to admit +that a structure even as perfect as the eye of an eagle might be formed +by natural selection, although in this case he does not know any of the +transitional grades. His reason ought to conquer his imagination; though +I have felt the difficulty far too keenly to be surprised at any degree +of hesitation in extending the principle of natural selection to such +startling lengths. + +It is scarcely possible to avoid comparing the eye to a telescope. We +know that this instrument has been perfected by the long-continued +efforts of the highest human intellects; and we naturally infer that the +eye has been formed by a somewhat analogous process. But may not this +inference be presumptuous? Have we any right to assume that the Creator +works by intellectual powers like those of man? If we must compare the +eye to an optical instrument, we ought in imagination to take a thick +layer of transparent tissue, with a nerve sensitive to light beneath, +and then suppose every part of this layer to be continually changing +slowly in density, so as to separate into layers of different densities +and thicknesses, placed at different distances from each other, and with +the surfaces of each layer slowly changing in form. Further we must +suppose that there is a power always intently watching each slight +accidental alteration in the transparent layers; and carefully selecting +each alteration which, under varied circumstances, may in any way, or in +any degree, tend to produce a distincter image. We must suppose each new +state of the instrument to be multiplied by the million; and each to be +preserved till a better be produced, and then the old ones to be +destroyed. In living bodies, variation will cause the slight +alterations, generation will multiply them almost infinitely, and +natural selection will pick out with unerring skill each improvement. +Let this process go on for millions on millions of years; and during +each year on millions of individuals of many kinds; and may we not +believe that a living optical instrument might thus be formed as +superior to one of glass, as the works of the Creator are to those of +man? + +If it could be demonstrated that any complex organ existed, which could +not possibly have been formed by numerous, successive, slight +modifications, my theory would absolutely break down. But I can find out +no such case. No doubt many organs exist of which we do not know the +transitional grades, more especially if we look to much-isolated +species, round which, according to my theory, there has been much +extinction. Or again, if we look to an organ common to all the members +of a large class, for in this latter case the organ must have been first +formed at an extremely remote period, since which all the many members +of the class have been developed; and in order to discover the early +transitional grades through which the organ has passed, we should have +to look to very ancient ancestral forms, long since become extinct. + +We should be extremely cautious in concluding that an organ could not +have been formed by transitional gradations of some kind. Numerous cases +could be given amongst the lower animals of the same organ performing at +the same time wholly distinct functions; thus the alimentary canal +respires, digests, and excretes in the larva of the dragon-fly and in +the fish Cobites. In the Hydra, the animal may be turned inside out, and +the exterior surface will then digest and the stomach respire. In such +cases natural selection might easily specialise, if any advantage were +thus gained, a part or organ, which had performed two functions, for one +function alone, and thus wholly change its nature by insensible steps. +Two distinct organs sometimes perform simultaneously the same function +in the same individual; to give one instance, there are fish with gills +or branchiæ that breathe the air dissolved in the water, at the same +time that they breathe free air in their swimbladders, this latter organ +having a ductus pneumaticus for its supply, and being divided by highly +vascular partitions. In these cases, one of the two organs might with +ease be modified and perfected so as to perform all the work by itself, +being aided during the process of modification by the other organ; and +then this other organ might be modified for some other and quite +distinct purpose, or be quite obliterated. + +The illustration of the swimbladder in fishes is a good one, because it +shows us clearly the highly important fact that an organ originally +constructed for one purpose, namely flotation, may be converted into one +for a wholly different purpose, namely respiration. The swimbladder has, +also, been worked in as an accessory to the auditory organs of certain +fish, or, for I do not know which view is now generally held, a part of +the auditory apparatus has been worked in as a complement to the +swimbladder. All physiologists admit that the swimbladder is homologous, +or “ideally similar,” in position and structure with the lungs of the +higher vertebrate animals: hence there seems to me to be no great +difficulty in believing that natural selection has actually converted a swimbladder into a lung, or organ used exclusively for respiration. -I can, indeed, hardly doubt that all vertebrate animals having true lungs have -descended by ordinary generation from an ancient prototype, of which we know -nothing, furnished with a floating apparatus or swimbladder. We can thus, as I -infer from Professor Owen’s interesting description of these parts, understand -the strange fact that every particle of food and drink which we swallow has to -pass over the orifice of the trachea, with some risk of falling into the lungs, -notwithstanding the beautiful contrivance by which the glottis is closed. In -the higher Vertebrata the branchiæ have wholly disappeared—the slits on the -sides of the neck and the loop-like course of the arteries still marking in the -embryo their former position. But it is conceivable that the now utterly lost -branchiæ might have been gradually worked in by natural selection for some -quite distinct purpose: in the same manner as, on the view entertained by some -naturalists that the branchiæ and dorsal scales of Annelids are homologous with -the wings and wing-covers of insects, it is probable that organs which at a -very ancient period served for respiration have been actually converted into -organs of flight. - -In considering transitions of organs, it is so important to bear in mind the -probability of conversion from one function to another, that I will give one -more instance. Pedunculated cirripedes have two minute folds of skin, called by -me the ovigerous frena, which serve, through the means of a sticky secretion, -to retain the eggs until they are hatched within the sack. These cirripedes -have no branchiæ, the whole surface of the body and sack, including the small -frena, serving for respiration. The Balanidæ or sessile cirripedes, on the -other hand, have no ovigerous frena, the eggs lying loose at the bottom of the -sack, in the well-enclosed shell; but they have large folded branchiæ. Now I -think no one will dispute that the ovigerous frena in the one family are -strictly homologous with the branchiæ of the other family; indeed, they -graduate into each other. Therefore I do not doubt that little folds of skin, -which originally served as ovigerous frena, but which, likewise, very slightly -aided the act of respiration, have been gradually converted by natural -selection into branchiæ, simply through an increase in their size and the -obliteration of their adhesive glands. If all pedunculated cirripedes had -become extinct, and they have already suffered far more extinction than have -sessile cirripedes, who would ever have imagined that the branchiæ in this -latter family had originally existed as organs for preventing the ova from -being washed out of the sack? - -Although we must be extremely cautious in concluding that any organ could not -possibly have been produced by successive transitional gradations, yet, -undoubtedly, grave cases of difficulty occur, some of which will be discussed -in my future work. - -One of the gravest is that of neuter insects, which are often very differently -constructed from either the males or fertile females; but this case will be -treated of in the next chapter. The electric organs of fishes offer another -case of special difficulty; it is impossible to conceive by what steps these -wondrous organs have been produced; but, as Owen and others have remarked, -their intimate structure closely resembles that of common muscle; and as it has -lately been shown that Rays have an organ closely analogous to the electric -apparatus, and yet do not, as Matteuchi asserts, discharge any electricity, we -must own that we are far too ignorant to argue that no transition of any kind -is possible. - -The electric organs offer another and even more serious difficulty; for they -occur in only about a dozen fishes, of which several are widely remote in their -affinities. Generally when the same organ appears in several members of the -same class, especially if in members having very different habits of life, we -may attribute its presence to inheritance from a common ancestor; and its -absence in some of the members to its loss through disuse or natural selection. -But if the electric organs had been inherited from one ancient progenitor thus -provided, we might have expected that all electric fishes would have been -specially related to each other. Nor does geology at all lead to the belief -that formerly most fishes had electric organs, which most of their modified +I can, indeed, hardly doubt that all vertebrate animals having true +lungs have descended by ordinary generation from an ancient prototype, +of which we know nothing, furnished with a floating apparatus or +swimbladder. We can thus, as I infer from Professor Owen’s interesting +description of these parts, understand the strange fact that every +particle of food and drink which we swallow has to pass over the orifice +of the trachea, with some risk of falling into the lungs, +notwithstanding the beautiful contrivance by which the glottis is +closed. In the higher Vertebrata the branchiæ have wholly +disappeared—the slits on the sides of the neck and the loop-like course +of the arteries still marking in the embryo their former position. But +it is conceivable that the now utterly lost branchiæ might have been +gradually worked in by natural selection for some quite distinct +purpose: in the same manner as, on the view entertained by some +naturalists that the branchiæ and dorsal scales of Annelids are +homologous with the wings and wing-covers of insects, it is probable +that organs which at a very ancient period served for respiration have +been actually converted into organs of flight. + +In considering transitions of organs, it is so important to bear in mind +the probability of conversion from one function to another, that I will +give one more instance. Pedunculated cirripedes have two minute folds of +skin, called by me the ovigerous frena, which serve, through the means +of a sticky secretion, to retain the eggs until they are hatched within +the sack. These cirripedes have no branchiæ, the whole surface of the +body and sack, including the small frena, serving for respiration. The +Balanidæ or sessile cirripedes, on the other hand, have no ovigerous +frena, the eggs lying loose at the bottom of the sack, in the +well-enclosed shell; but they have large folded branchiæ. Now I think no +one will dispute that the ovigerous frena in the one family are strictly +homologous with the branchiæ of the other family; indeed, they graduate +into each other. Therefore I do not doubt that little folds of skin, +which originally served as ovigerous frena, but which, likewise, very +slightly aided the act of respiration, have been gradually converted by +natural selection into branchiæ, simply through an increase in their +size and the obliteration of their adhesive glands. If all pedunculated +cirripedes had become extinct, and they have already suffered far more +extinction than have sessile cirripedes, who would ever have imagined +that the branchiæ in this latter family had originally existed as organs +for preventing the ova from being washed out of the sack? + +Although we must be extremely cautious in concluding that any organ +could not possibly have been produced by successive transitional +gradations, yet, undoubtedly, grave cases of difficulty occur, some of +which will be discussed in my future work. + +One of the gravest is that of neuter insects, which are often very +differently constructed from either the males or fertile females; but +this case will be treated of in the next chapter. The electric organs of +fishes offer another case of special difficulty; it is impossible to +conceive by what steps these wondrous organs have been produced; but, as +Owen and others have remarked, their intimate structure closely +resembles that of common muscle; and as it has lately been shown that +Rays have an organ closely analogous to the electric apparatus, and yet +do not, as Matteuchi asserts, discharge any electricity, we must own +that we are far too ignorant to argue that no transition of any kind is +possible. + +The electric organs offer another and even more serious difficulty; for +they occur in only about a dozen fishes, of which several are widely +remote in their affinities. Generally when the same organ appears in +several members of the same class, especially if in members having very +different habits of life, we may attribute its presence to inheritance +from a common ancestor; and its absence in some of the members to its +loss through disuse or natural selection. But if the electric organs +had been inherited from one ancient progenitor thus provided, we might +have expected that all electric fishes would have been specially related +to each other. Nor does geology at all lead to the belief that formerly +most fishes had electric organs, which most of their modified descendants have lost. The presence of luminous organs in a few insects, belonging to different families and orders, offers a parallel case of difficulty. Other cases could be given; for instance in plants, the very -curious contrivance of a mass of pollen-grains, borne on a foot-stalk with a -sticky gland at the end, is the same in Orchis and Asclepias,—genera almost as -remote as possible amongst flowering plants. In all these cases of two very -distinct species furnished with apparently the same anomalous organ, it should -be observed that, although the general appearance and function of the organ may -be the same, yet some fundamental difference can generally be detected. I am -inclined to believe that in nearly the same way as two men have sometimes -independently hit on the very same invention, so natural selection, working for -the good of each being and taking advantage of analogous variations, has -sometimes modified in very nearly the same manner two parts in two organic -beings, which owe but little of their structure in common to inheritance from -the same ancestor. - -Although in many cases it is most difficult to conjecture by what transitions -an organ could have arrived at its present state; yet, considering that the -proportion of living and known forms to the extinct and unknown is very small, -I have been astonished how rarely an organ can be named, towards which no -transitional grade is known to lead. The truth of this remark is indeed shown -by that old canon in natural history of “Natura non facit saltum.” We meet with -this admission in the writings of almost every experienced naturalist; or, as -Milne Edwards has well expressed it, nature is prodigal in variety, but niggard -in innovation. Why, on the theory of Creation, should this be so? Why should -all the parts and organs of many independent beings, each supposed to have been -separately created for its proper place in nature, be so invariably linked -together by graduated steps? Why should not Nature have taken a leap from -structure to structure? On the theory of natural selection, we can clearly -understand why she should not; for natural selection can act only by taking -advantage of slight successive variations; she can never take a leap, but must -advance by the shortest and slowest steps. - -Organs of little apparent importance.—As natural selection acts by life and -death,—by the preservation of individuals with any favourable variation, and by -the destruction of those with any unfavourable deviation of structure,—I have -sometimes felt much difficulty in understanding the origin of simple parts, of -which the importance does not seem sufficient to cause the preservation of -successively varying individuals. I have sometimes felt as much difficulty, -though of a very different kind, on this head, as in the case of an organ as -perfect and complex as the eye. - -In the first place, we are much too ignorant in regard to the whole economy of -any one organic being, to say what slight modifications would be of importance -or not. In a former chapter I have given instances of most trifling characters, -such as the down on fruit and the colour of the flesh, which, from determining -the attacks of insects or from being correlated with constitutional -differences, might assuredly be acted on by natural selection. The tail of the -giraffe looks like an artificially constructed fly-flapper; and it seems at -first incredible that this could have been adapted for its present purpose by -successive slight modifications, each better and better, for so trifling an -object as driving away flies; yet we should pause before being too positive -even in this case, for we know that the distribution and existence of cattle +curious contrivance of a mass of pollen-grains, borne on a foot-stalk +with a sticky gland at the end, is the same in Orchis and +Asclepias,—genera almost as remote as possible amongst flowering plants. +In all these cases of two very distinct species furnished with +apparently the same anomalous organ, it should be observed that, +although the general appearance and function of the organ may be the +same, yet some fundamental difference can generally be detected. I am +inclined to believe that in nearly the same way as two men have +sometimes independently hit on the very same invention, so natural +selection, working for the good of each being and taking advantage of +analogous variations, has sometimes modified in very nearly the same +manner two parts in two organic beings, which owe but little of their +structure in common to inheritance from the same ancestor. + +Although in many cases it is most difficult to conjecture by what +transitions an organ could have arrived at its present state; yet, +considering that the proportion of living and known forms to the extinct +and unknown is very small, I have been astonished how rarely an organ +can be named, towards which no transitional grade is known to lead. The +truth of this remark is indeed shown by that old canon in natural +history of “Natura non facit saltum.” We meet with this admission in the +writings of almost every experienced naturalist; or, as Milne Edwards +has well expressed it, nature is prodigal in variety, but niggard in +innovation. Why, on the theory of Creation, should this be so? Why +should all the parts and organs of many independent beings, each +supposed to have been separately created for its proper place in nature, +be so invariably linked together by graduated steps? Why should not +Nature have taken a leap from structure to structure? On the theory of +natural selection, we can clearly understand why she should not; for +natural selection can act only by taking advantage of slight successive +variations; she can never take a leap, but must advance by the shortest +and slowest steps. + +Organs of little apparent importance.—As natural selection acts by life +and death,—by the preservation of individuals with any favourable +variation, and by the destruction of those with any unfavourable +deviation of structure,—I have sometimes felt much difficulty in +understanding the origin of simple parts, of which the importance does +not seem sufficient to cause the preservation of successively varying +individuals. I have sometimes felt as much difficulty, though of a very +different kind, on this head, as in the case of an organ as perfect and +complex as the eye. + +In the first place, we are much too ignorant in regard to the whole +economy of any one organic being, to say what slight modifications would +be of importance or not. In a former chapter I have given instances of +most trifling characters, such as the down on fruit and the colour of +the flesh, which, from determining the attacks of insects or from being +correlated with constitutional differences, might assuredly be acted on +by natural selection. The tail of the giraffe looks like an artificially +constructed fly-flapper; and it seems at first incredible that this +could have been adapted for its present purpose by successive slight +modifications, each better and better, for so trifling an object as +driving away flies; yet we should pause before being too positive even +in this case, for we know that the distribution and existence of cattle and other animals in South America absolutely depends on their power of -resisting the attacks of insects: so that individuals which could by any means -defend themselves from these small enemies, would be able to range into new -pastures and thus gain a great advantage. It is not that the larger quadrupeds -are actually destroyed (except in some rare cases) by the flies, but they are -incessantly harassed and their strength reduced, so that they are more subject -to disease, or not so well enabled in a coming dearth to search for food, or to -escape from beasts of prey. - -Organs now of trifling importance have probably in some cases been of high -importance to an early progenitor, and, after having been slowly perfected at a -former period, have been transmitted in nearly the same state, although now -become of very slight use; and any actually injurious deviations in their -structure will always have been checked by natural selection. Seeing how -important an organ of locomotion the tail is in most aquatic animals, its -general presence and use for many purposes in so many land animals, which in -their lungs or modified swim-bladders betray their aquatic origin, may perhaps -be thus accounted for. A well-developed tail having been formed in an aquatic -animal, it might subsequently come to be worked in for all sorts of purposes, -as a fly-flapper, an organ of prehension, or as an aid in turning, as with the -dog, though the aid must be slight, for the hare, with hardly any tail, can -double quickly enough. - -In the second place, we may sometimes attribute importance to characters which -are really of very little importance, and which have originated from quite -secondary causes, independently of natural selection. We should remember that -climate, food, etc., probably have some little direct influence on the -organisation; that characters reappear from the law of reversion; that -correlation of growth will have had a most important influence in modifying -various structures; and finally, that sexual selection will often have largely -modified the external characters of animals having a will, to give one male an -advantage in fighting with another or in charming the females. Moreover when a -modification of structure has primarily arisen from the above or other unknown -causes, it may at first have been of no advantage to the species, but may -subsequently have been taken advantage of by the descendants of the species -under new conditions of life and with newly acquired habits. +resisting the attacks of insects: so that individuals which could by any +means defend themselves from these small enemies, would be able to range +into new pastures and thus gain a great advantage. It is not that the +larger quadrupeds are actually destroyed (except in some rare cases) by +the flies, but they are incessantly harassed and their strength reduced, +so that they are more subject to disease, or not so well enabled in a +coming dearth to search for food, or to escape from beasts of prey. + +Organs now of trifling importance have probably in some cases been of +high importance to an early progenitor, and, after having been slowly +perfected at a former period, have been transmitted in nearly the same +state, although now become of very slight use; and any actually +injurious deviations in their structure will always have been checked by +natural selection. Seeing how important an organ of locomotion the tail +is in most aquatic animals, its general presence and use for many +purposes in so many land animals, which in their lungs or modified +swim-bladders betray their aquatic origin, may perhaps be thus accounted +for. A well-developed tail having been formed in an aquatic animal, it +might subsequently come to be worked in for all sorts of purposes, as a +fly-flapper, an organ of prehension, or as an aid in turning, as with +the dog, though the aid must be slight, for the hare, with hardly any +tail, can double quickly enough. + +In the second place, we may sometimes attribute importance to characters +which are really of very little importance, and which have originated +from quite secondary causes, independently of natural selection. We +should remember that climate, food, etc., probably have some little +direct influence on the organisation; that characters reappear from the +law of reversion; that correlation of growth will have had a most +important influence in modifying various structures; and finally, that +sexual selection will often have largely modified the external +characters of animals having a will, to give one male an advantage in +fighting with another or in charming the females. Moreover when a +modification of structure has primarily arisen from the above or other +unknown causes, it may at first have been of no advantage to the +species, but may subsequently have been taken advantage of by the +descendants of the species under new conditions of life and with newly +acquired habits. To give a few instances to illustrate these latter remarks. If green -woodpeckers alone had existed, and we did not know that there were many black -and pied kinds, I dare say that we should have thought that the green colour -was a beautiful adaptation to hide this tree-frequenting bird from its enemies; -and consequently that it was a character of importance and might have been -acquired through natural selection; as it is, I have no doubt that the colour -is due to some quite distinct cause, probably to sexual selection. A trailing -bamboo in the Malay Archipelago climbs the loftiest trees by the aid of -exquisitely constructed hooks clustered around the ends of the branches, and -this contrivance, no doubt, is of the highest service to the plant; but as we -see nearly similar hooks on many trees which are not climbers, the hooks on the -bamboo may have arisen from unknown laws of growth, and have been subsequently -taken advantage of by the plant undergoing further modification and becoming a -climber. The naked skin on the head of a vulture is generally looked at as a -direct adaptation for wallowing in putridity; and so it may be, or it may -possibly be due to the direct action of putrid matter; but we should be very -cautious in drawing any such inference, when we see that the skin on the head -of the clean-feeding male turkey is likewise naked. The sutures in the skulls +woodpeckers alone had existed, and we did not know that there were many +black and pied kinds, I dare say that we should have thought that the +green colour was a beautiful adaptation to hide this tree-frequenting +bird from its enemies; and consequently that it was a character of +importance and might have been acquired through natural selection; as it +is, I have no doubt that the colour is due to some quite distinct cause, +probably to sexual selection. A trailing bamboo in the Malay Archipelago +climbs the loftiest trees by the aid of exquisitely constructed hooks +clustered around the ends of the branches, and this contrivance, no +doubt, is of the highest service to the plant; but as we see nearly +similar hooks on many trees which are not climbers, the hooks on the +bamboo may have arisen from unknown laws of growth, and have been +subsequently taken advantage of by the plant undergoing further +modification and becoming a climber. The naked skin on the head of a +vulture is generally looked at as a direct adaptation for wallowing in +putridity; and so it may be, or it may possibly be due to the direct +action of putrid matter; but we should be very cautious in drawing any +such inference, when we see that the skin on the head of the +clean-feeding male turkey is likewise naked. The sutures in the skulls of young mammals have been advanced as a beautiful adaptation for aiding -parturition, and no doubt they facilitate, or may be indispensable for this -act; but as sutures occur in the skulls of young birds and reptiles, which have -only to escape from a broken egg, we may infer that this structure has arisen -from the laws of growth, and has been taken advantage of in the parturition of -the higher animals. - -We are profoundly ignorant of the causes producing slight and unimportant -variations; and we are immediately made conscious of this by reflecting on the -differences in the breeds of our domesticated animals in different -countries,—more especially in the less civilized countries where there has been -but little artificial selection. Careful observers are convinced that a damp -climate affects the growth of the hair, and that with the hair the horns are -correlated. Mountain breeds always differ from lowland breeds; and a -mountainous country would probably affect the hind limbs from exercising them -more, and possibly even the form of the pelvis; and then by the law of -homologous variation, the front limbs and even the head would probably be -affected. The shape, also, of the pelvis might affect by pressure the shape of -the head of the young in the womb. The laborious breathing necessary in high -regions would, we have some reason to believe, increase the size of the chest; +parturition, and no doubt they facilitate, or may be indispensable for +this act; but as sutures occur in the skulls of young birds and +reptiles, which have only to escape from a broken egg, we may infer that +this structure has arisen from the laws of growth, and has been taken +advantage of in the parturition of the higher animals. + +We are profoundly ignorant of the causes producing slight and +unimportant variations; and we are immediately made conscious of this by +reflecting on the differences in the breeds of our domesticated animals +in different countries,—more especially in the less civilized countries +where there has been but little artificial selection. Careful observers +are convinced that a damp climate affects the growth of the hair, and +that with the hair the horns are correlated. Mountain breeds always +differ from lowland breeds; and a mountainous country would probably +affect the hind limbs from exercising them more, and possibly even the +form of the pelvis; and then by the law of homologous variation, the +front limbs and even the head would probably be affected. The shape, +also, of the pelvis might affect by pressure the shape of the head of +the young in the womb. The laborious breathing necessary in high regions +would, we have some reason to believe, increase the size of the chest; and again correlation would come into play. Animals kept by savages in -different countries often have to struggle for their own subsistence, and would -be exposed to a certain extent to natural selection, and individuals with -slightly different constitutions would succeed best under different climates; -and there is reason to believe that constitution and colour are correlated. A -good observer, also, states that in cattle susceptibility to the attacks of -flies is correlated with colour, as is the liability to be poisoned by certain -plants; so that colour would be thus subjected to the action of natural -selection. But we are far too ignorant to speculate on the relative importance -of the several known and unknown laws of variation; and I have here alluded to -them only to show that, if we are unable to account for the characteristic -differences of our domestic breeds, which nevertheless we generally admit to -have arisen through ordinary generation, we ought not to lay too much stress on -our ignorance of the precise cause of the slight analogous differences between -species. I might have adduced for this same purpose the differences between the -races of man, which are so strongly marked; I may add that some little light -can apparently be thrown on the origin of these differences, chiefly through -sexual selection of a particular kind, but without here entering on copious +different countries often have to struggle for their own subsistence, +and would be exposed to a certain extent to natural selection, and +individuals with slightly different constitutions would succeed best +under different climates; and there is reason to believe that +constitution and colour are correlated. A good observer, also, states +that in cattle susceptibility to the attacks of flies is correlated with +colour, as is the liability to be poisoned by certain plants; so that +colour would be thus subjected to the action of natural selection. But +we are far too ignorant to speculate on the relative importance of the +several known and unknown laws of variation; and I have here alluded to +them only to show that, if we are unable to account for the +characteristic differences of our domestic breeds, which nevertheless we +generally admit to have arisen through ordinary generation, we ought not +to lay too much stress on our ignorance of the precise cause of the +slight analogous differences between species. I might have adduced for +this same purpose the differences between the races of man, which are so +strongly marked; I may add that some little light can apparently be +thrown on the origin of these differences, chiefly through sexual +selection of a particular kind, but without here entering on copious details my reasoning would appear frivolous. -The foregoing remarks lead me to say a few words on the protest lately made by -some naturalists, against the utilitarian doctrine that every detail of -structure has been produced for the good of its possessor. They believe that -very many structures have been created for beauty in the eyes of man, or for -mere variety. This doctrine, if true, would be absolutely fatal to my theory. -Yet I fully admit that many structures are of no direct use to their -possessors. Physical conditions probably have had some little effect on -structure, quite independently of any good thus gained. Correlation of growth -has no doubt played a most important part, and a useful modification of one -part will often have entailed on other parts diversified changes of no direct -use. So again characters which formerly were useful, or which formerly had -arisen from correlation of growth, or from other unknown cause, may reappear -from the law of reversion, though now of no direct use. The effects of sexual -selection, when displayed in beauty to charm the females, can be called useful -only in rather a forced sense. But by far the most important consideration is -that the chief part of the organisation of every being is simply due to -inheritance; and consequently, though each being assuredly is well fitted for -its place in nature, many structures now have no direct relation to the habits -of life of each species. Thus, we can hardly believe that the webbed feet of -the upland goose or of the frigate-bird are of special use to these birds; we -cannot believe that the same bones in the arm of the monkey, in the fore leg of -the horse, in the wing of the bat, and in the flipper of the seal, are of -special use to these animals. We may safely attribute these structures to -inheritance. But to the progenitor of the upland goose and of the frigate-bird, -webbed feet no doubt were as useful as they now are to the most aquatic of -existing birds. So we may believe that the progenitor of the seal had not a -flipper, but a foot with five toes fitted for walking or grasping; and we may -further venture to believe that the several bones in the limbs of the monkey, -horse, and bat, which have been inherited from a common progenitor, were -formerly of more special use to that progenitor, or its progenitors, than they -now are to these animals having such widely diversified habits. Therefore we -may infer that these several bones might have been acquired through natural -selection, subjected formerly, as now, to the several laws of inheritance, -reversion, correlation of growth, etc. Hence every detail of structure in every -living creature (making some little allowance for the direct action of physical -conditions) may be viewed, either as having been of special use to some -ancestral form, or as being now of special use to the descendants of this -form—either directly, or indirectly through the complex laws of growth. - -Natural selection cannot possibly produce any modification in any one species -exclusively for the good of another species; though throughout nature one -species incessantly takes advantage of, and profits by, the structure of -another. But natural selection can and does often produce structures for the -direct injury of other species, as we see in the fang of the adder, and in the -ovipositor of the ichneumon, by which its eggs are deposited in the living -bodies of other insects. If it could be proved that any part of the structure -of any one species had been formed for the exclusive good of another species, -it would annihilate my theory, for such could not have been produced through -natural selection. Although many statements may be found in works on natural -history to this effect, I cannot find even one which seems to me of any weight. -It is admitted that the rattlesnake has a poison-fang for its own defence and -for the destruction of its prey; but some authors suppose that at the same time -this snake is furnished with a rattle for its own injury, namely, to warn its -prey to escape. I would almost as soon believe that the cat curls the end of -its tail when preparing to spring, in order to warn the doomed mouse. But I -have not space here to enter on this and other such cases. - -Natural selection will never produce in a being anything injurious to itself, -for natural selection acts solely by and for the good of each. No organ will be -formed, as Paley has remarked, for the purpose of causing pain or for doing an -injury to its possessor. If a fair balance be struck between the good and evil -caused by each part, each will be found on the whole advantageous. After the -lapse of time, under changing conditions of life, if any part comes to be -injurious, it will be modified; or if it be not so, the being will become -extinct, as myriads have become extinct. - -Natural selection tends only to make each organic being as perfect as, or -slightly more perfect than, the other inhabitants of the same country with -which it has to struggle for existence. And we see that this is the degree of -perfection attained under nature. The endemic productions of New Zealand, for -instance, are perfect one compared with another; but they are now rapidly -yielding before the advancing legions of plants and animals introduced from -Europe. Natural selection will not produce absolute perfection, nor do we -always meet, as far as we can judge, with this high standard under nature. The -correction for the aberration of light is said, on high authority, not to be -perfect even in that most perfect organ, the eye. If our reason leads us to -admire with enthusiasm a multitude of inimitable contrivances in nature, this -same reason tells us, though we may easily err on both sides, that some other -contrivances are less perfect. Can we consider the sting of the wasp or of the -bee as perfect, which, when used against many attacking animals, cannot be -withdrawn, owing to the backward serratures, and so inevitably causes the death -of the insect by tearing out its viscera? - -If we look at the sting of the bee, as having originally existed in a remote -progenitor as a boring and serrated instrument, like that in so many members of -the same great order, and which has been modified but not perfected for its -present purpose, with the poison originally adapted to cause galls subsequently -intensified, we can perhaps understand how it is that the use of the sting -should so often cause the insect’s own death: for if on the whole the power of -stinging be useful to the community, it will fulfil all the requirements of -natural selection, though it may cause the death of some few members. If we -admire the truly wonderful power of scent by which the males of many insects -find their females, can we admire the production for this single purpose of -thousands of drones, which are utterly useless to the community for any other -end, and which are ultimately slaughtered by their industrious and sterile -sisters? It may be difficult, but we ought to admire the savage instinctive -hatred of the queen-bee, which urges her instantly to destroy the young queens -her daughters as soon as born, or to perish herself in the combat; for -undoubtedly this is for the good of the community; and maternal love or -maternal hatred, though the latter fortunately is most rare, is all the same to -the inexorable principle of natural selection. If we admire the several -ingenious contrivances, by which the flowers of the orchis and of many other -plants are fertilised through insect agency, can we consider as equally perfect -the elaboration by our fir-trees of dense clouds of pollen, in order that a few -granules may be wafted by a chance breeze on to the ovules? - -Summary of Chapter.—We have in this chapter discussed some of the difficulties -and objections which may be urged against my theory. Many of them are very -grave; but I think that in the discussion light has been thrown on several -facts, which on the theory of independent acts of creation are utterly obscure. -We have seen that species at any one period are not indefinitely variable, and -are not linked together by a multitude of intermediate gradations, partly -because the process of natural selection will always be very slow, and will -act, at any one time, only on a very few forms; and partly because the very -process of natural selection almost implies the continual supplanting and -extinction of preceding and intermediate gradations. Closely allied species, -now living on a continuous area, must often have been formed when the area was -not continuous, and when the conditions of life did not insensibly graduate -away from one part to another. When two varieties are formed in two districts -of a continuous area, an intermediate variety will often be formed, fitted for -an intermediate zone; but from reasons assigned, the intermediate variety will -usually exist in lesser numbers than the two forms which it connects; -consequently the two latter, during the course of further modification, from -existing in greater numbers, will have a great advantage over the less numerous -intermediate variety, and will thus generally succeed in supplanting and -exterminating it. - -We have seen in this chapter how cautious we should be in concluding that the -most different habits of life could not graduate into each other; that a bat, -for instance, could not have been formed by natural selection from an animal -which at first could only glide through the air. - -We have seen that a species may under new conditions of life change its habits, -or have diversified habits, with some habits very unlike those of its nearest -congeners. Hence we can understand, bearing in mind that each organic being is -trying to live wherever it can live, how it has arisen that there are upland -geese with webbed feet, ground woodpeckers, diving thrushes, and petrels with -the habits of auks. - -Although the belief that an organ so perfect as the eye could have been formed -by natural selection, is more than enough to stagger any one; yet in the case -of any organ, if we know of a long series of gradations in complexity, each -good for its possessor, then, under changing conditions of life, there is no -logical impossibility in the acquirement of any conceivable degree of -perfection through natural selection. In the cases in which we know of no -intermediate or transitional states, we should be very cautious in concluding -that none could have existed, for the homologies of many organs and their -intermediate states show that wonderful metamorphoses in function are at least -possible. For instance, a swim-bladder has apparently been converted into an -air-breathing lung. The same organ having performed simultaneously very -different functions, and then having been specialised for one function; and two -very distinct organs having performed at the same time the same function, the -one having been perfected whilst aided by the other, must often have largely +The foregoing remarks lead me to say a few words on the protest lately +made by some naturalists, against the utilitarian doctrine that every +detail of structure has been produced for the good of its possessor. +They believe that very many structures have been created for beauty in +the eyes of man, or for mere variety. This doctrine, if true, would be +absolutely fatal to my theory. Yet I fully admit that many structures +are of no direct use to their possessors. Physical conditions probably +have had some little effect on structure, quite independently of any +good thus gained. Correlation of growth has no doubt played a most +important part, and a useful modification of one part will often have +entailed on other parts diversified changes of no direct use. So again +characters which formerly were useful, or which formerly had arisen from +correlation of growth, or from other unknown cause, may reappear from +the law of reversion, though now of no direct use. The effects of sexual +selection, when displayed in beauty to charm the females, can be called +useful only in rather a forced sense. But by far the most important +consideration is that the chief part of the organisation of every being +is simply due to inheritance; and consequently, though each being +assuredly is well fitted for its place in nature, many structures now +have no direct relation to the habits of life of each species. Thus, we +can hardly believe that the webbed feet of the upland goose or of the +frigate-bird are of special use to these birds; we cannot believe that +the same bones in the arm of the monkey, in the fore leg of the horse, +in the wing of the bat, and in the flipper of the seal, are of special +use to these animals. We may safely attribute these structures to +inheritance. But to the progenitor of the upland goose and of the +frigate-bird, webbed feet no doubt were as useful as they now are to the +most aquatic of existing birds. So we may believe that the progenitor of +the seal had not a flipper, but a foot with five toes fitted for walking +or grasping; and we may further venture to believe that the several +bones in the limbs of the monkey, horse, and bat, which have been +inherited from a common progenitor, were formerly of more special use to +that progenitor, or its progenitors, than they now are to these animals +having such widely diversified habits. Therefore we may infer that these +several bones might have been acquired through natural selection, +subjected formerly, as now, to the several laws of inheritance, +reversion, correlation of growth, etc. Hence every detail of structure +in every living creature (making some little allowance for the direct +action of physical conditions) may be viewed, either as having been of +special use to some ancestral form, or as being now of special use to +the descendants of this form—either directly, or indirectly through the +complex laws of growth. + +Natural selection cannot possibly produce any modification in any one +species exclusively for the good of another species; though throughout +nature one species incessantly takes advantage of, and profits by, the +structure of another. But natural selection can and does often produce +structures for the direct injury of other species, as we see in the fang +of the adder, and in the ovipositor of the ichneumon, by which its eggs +are deposited in the living bodies of other insects. If it could be +proved that any part of the structure of any one species had been formed +for the exclusive good of another species, it would annihilate my +theory, for such could not have been produced through natural selection. +Although many statements may be found in works on natural history to +this effect, I cannot find even one which seems to me of any weight. It +is admitted that the rattlesnake has a poison-fang for its own defence +and for the destruction of its prey; but some authors suppose that at +the same time this snake is furnished with a rattle for its own injury, +namely, to warn its prey to escape. I would almost as soon believe that +the cat curls the end of its tail when preparing to spring, in order to +warn the doomed mouse. But I have not space here to enter on this and +other such cases. + +Natural selection will never produce in a being anything injurious to +itself, for natural selection acts solely by and for the good of each. +No organ will be formed, as Paley has remarked, for the purpose of +causing pain or for doing an injury to its possessor. If a fair balance +be struck between the good and evil caused by each part, each will be +found on the whole advantageous. After the lapse of time, under changing +conditions of life, if any part comes to be injurious, it will be +modified; or if it be not so, the being will become extinct, as myriads +have become extinct. + +Natural selection tends only to make each organic being as perfect as, +or slightly more perfect than, the other inhabitants of the same country +with which it has to struggle for existence. And we see that this is the +degree of perfection attained under nature. The endemic productions of +New Zealand, for instance, are perfect one compared with another; but +they are now rapidly yielding before the advancing legions of plants and +animals introduced from Europe. Natural selection will not produce +absolute perfection, nor do we always meet, as far as we can judge, with +this high standard under nature. The correction for the aberration of +light is said, on high authority, not to be perfect even in that most +perfect organ, the eye. If our reason leads us to admire with enthusiasm +a multitude of inimitable contrivances in nature, this same reason tells +us, though we may easily err on both sides, that some other contrivances +are less perfect. Can we consider the sting of the wasp or of the bee as +perfect, which, when used against many attacking animals, cannot be +withdrawn, owing to the backward serratures, and so inevitably causes +the death of the insect by tearing out its viscera? + +If we look at the sting of the bee, as having originally existed in a +remote progenitor as a boring and serrated instrument, like that in so +many members of the same great order, and which has been modified but +not perfected for its present purpose, with the poison originally +adapted to cause galls subsequently intensified, we can perhaps +understand how it is that the use of the sting should so often cause the +insect’s own death: for if on the whole the power of stinging be useful +to the community, it will fulfil all the requirements of natural +selection, though it may cause the death of some few members. If we +admire the truly wonderful power of scent by which the males of many +insects find their females, can we admire the production for this single +purpose of thousands of drones, which are utterly useless to the +community for any other end, and which are ultimately slaughtered by +their industrious and sterile sisters? It may be difficult, but we ought +to admire the savage instinctive hatred of the queen-bee, which urges +her instantly to destroy the young queens her daughters as soon as born, +or to perish herself in the combat; for undoubtedly this is for the good +of the community; and maternal love or maternal hatred, though the +latter fortunately is most rare, is all the same to the inexorable +principle of natural selection. If we admire the several ingenious +contrivances, by which the flowers of the orchis and of many other +plants are fertilised through insect agency, can we consider as equally +perfect the elaboration by our fir-trees of dense clouds of pollen, in +order that a few granules may be wafted by a chance breeze on to the +ovules? + +Summary of Chapter.—We have in this chapter discussed some of the +difficulties and objections which may be urged against my theory. Many +of them are very grave; but I think that in the discussion light has +been thrown on several facts, which on the theory of independent acts of +creation are utterly obscure. We have seen that species at any one +period are not indefinitely variable, and are not linked together by a +multitude of intermediate gradations, partly because the process of +natural selection will always be very slow, and will act, at any one +time, only on a very few forms; and partly because the very process of +natural selection almost implies the continual supplanting and +extinction of preceding and intermediate gradations. Closely allied +species, now living on a continuous area, must often have been formed +when the area was not continuous, and when the conditions of life did +not insensibly graduate away from one part to another. When two +varieties are formed in two districts of a continuous area, an +intermediate variety will often be formed, fitted for an intermediate +zone; but from reasons assigned, the intermediate variety will usually +exist in lesser numbers than the two forms which it connects; +consequently the two latter, during the course of further modification, +from existing in greater numbers, will have a great advantage over the +less numerous intermediate variety, and will thus generally succeed in +supplanting and exterminating it. + +We have seen in this chapter how cautious we should be in concluding +that the most different habits of life could not graduate into each +other; that a bat, for instance, could not have been formed by natural +selection from an animal which at first could only glide through the +air. + +We have seen that a species may under new conditions of life change its +habits, or have diversified habits, with some habits very unlike those +of its nearest congeners. Hence we can understand, bearing in mind that +each organic being is trying to live wherever it can live, how it has +arisen that there are upland geese with webbed feet, ground woodpeckers, +diving thrushes, and petrels with the habits of auks. + +Although the belief that an organ so perfect as the eye could have been +formed by natural selection, is more than enough to stagger any one; yet +in the case of any organ, if we know of a long series of gradations in +complexity, each good for its possessor, then, under changing conditions +of life, there is no logical impossibility in the acquirement of any +conceivable degree of perfection through natural selection. In the cases +in which we know of no intermediate or transitional states, we should be +very cautious in concluding that none could have existed, for the +homologies of many organs and their intermediate states show that +wonderful metamorphoses in function are at least possible. For instance, +a swim-bladder has apparently been converted into an air-breathing lung. +The same organ having performed simultaneously very different functions, +and then having been specialised for one function; and two very distinct +organs having performed at the same time the same function, the one +having been perfected whilst aided by the other, must often have largely facilitated transitions. -We are far too ignorant, in almost every case, to be enabled to assert that any -part or organ is so unimportant for the welfare of a species, that -modifications in its structure could not have been slowly accumulated by means -of natural selection. But we may confidently believe that many modifications, -wholly due to the laws of growth, and at first in no way advantageous to a -species, have been subsequently taken advantage of by the still further -modified descendants of this species. We may, also, believe that a part -formerly of high importance has often been retained (as the tail of an aquatic -animal by its terrestrial descendants), though it has become of such small -importance that it could not, in its present state, have been acquired by -natural selection,—a power which acts solely by the preservation of profitable +We are far too ignorant, in almost every case, to be enabled to assert +that any part or organ is so unimportant for the welfare of a species, +that modifications in its structure could not have been slowly +accumulated by means of natural selection. But we may confidently +believe that many modifications, wholly due to the laws of growth, and +at first in no way advantageous to a species, have been subsequently +taken advantage of by the still further modified descendants of this +species. We may, also, believe that a part formerly of high importance +has often been retained (as the tail of an aquatic animal by its +terrestrial descendants), though it has become of such small importance +that it could not, in its present state, have been acquired by natural +selection,—a power which acts solely by the preservation of profitable variations in the struggle for life. -Natural selection will produce nothing in one species for the exclusive good or -injury of another; though it may well produce parts, organs, and excretions -highly useful or even indispensable, or highly injurious to another species, -but in all cases at the same time useful to the owner. Natural selection in -each well-stocked country, must act chiefly through the competition of the -inhabitants one with another, and consequently will produce perfection, or -strength in the battle for life, only according to the standard of that -country. Hence the inhabitants of one country, generally the smaller one, will -often yield, as we see they do yield, to the inhabitants of another and -generally larger country. For in the larger country there will have existed -more individuals, and more diversified forms, and the competition will have -been severer, and thus the standard of perfection will have been rendered -higher. Natural selection will not necessarily produce absolute perfection; -nor, as far as we can judge by our limited faculties, can absolute perfection -be everywhere found. - -On the theory of natural selection we can clearly understand the full meaning -of that old canon in natural history, “Natura non facit saltum.” This canon, if -we look only to the present inhabitants of the world, is not strictly correct, -but if we include all those of past times, it must by my theory be strictly -true. - -It is generally acknowledged that all organic beings have been formed on two -great laws—Unity of Type, and the Conditions of Existence. By unity of type is -meant that fundamental agreement in structure, which we see in organic beings -of the same class, and which is quite independent of their habits of life. On -my theory, unity of type is explained by unity of descent. The expression of -conditions of existence, so often insisted on by the illustrious Cuvier, is -fully embraced by the principle of natural selection. For natural selection -acts by either now adapting the varying parts of each being to its organic and -inorganic conditions of life; or by having adapted them during long-past -periods of time: the adaptations being aided in some cases by use and disuse, -being slightly affected by the direct action of the external conditions of -life, and being in all cases subjected to the several laws of growth. Hence, in -fact, the law of the Conditions of Existence is the higher law; as it includes, -through the inheritance of former adaptations, that of Unity of Type. - -CHAPTER VII. -INSTINCT. - -Instincts comparable with habits, but different in their origin. Instincts -graduated. Aphides and ants. Instincts variable. Domestic instincts, their -origin. Natural instincts of the cuckoo, ostrich, and parasitic bees. -Slave-making ants. Hive-bee, its cell-making instinct. Difficulties on the -theory of the Natural Selection of instincts. Neuter or sterile insects. -Summary. +Natural selection will produce nothing in one species for the exclusive +good or injury of another; though it may well produce parts, organs, and +excretions highly useful or even indispensable, or highly injurious to +another species, but in all cases at the same time useful to the owner. +Natural selection in each well-stocked country, must act chiefly through +the competition of the inhabitants one with another, and consequently +will produce perfection, or strength in the battle for life, only +according to the standard of that country. Hence the inhabitants of one +country, generally the smaller one, will often yield, as we see they do +yield, to the inhabitants of another and generally larger country. For +in the larger country there will have existed more individuals, and more +diversified forms, and the competition will have been severer, and thus +the standard of perfection will have been rendered higher. Natural +selection will not necessarily produce absolute perfection; nor, as far +as we can judge by our limited faculties, can absolute perfection be +everywhere found. + +On the theory of natural selection we can clearly understand the full +meaning of that old canon in natural history, “Natura non facit saltum.” +This canon, if we look only to the present inhabitants of the world, is +not strictly correct, but if we include all those of past times, it must +by my theory be strictly true. + +It is generally acknowledged that all organic beings have been formed on +two great laws—Unity of Type, and the Conditions of Existence. By unity +of type is meant that fundamental agreement in structure, which we see +in organic beings of the same class, and which is quite independent of +their habits of life. On my theory, unity of type is explained by unity +of descent. The expression of conditions of existence, so often insisted +on by the illustrious Cuvier, is fully embraced by the principle of +natural selection. For natural selection acts by either now adapting the +varying parts of each being to its organic and inorganic conditions of +life; or by having adapted them during long-past periods of time: the +adaptations being aided in some cases by use and disuse, being slightly +affected by the direct action of the external conditions of life, and +being in all cases subjected to the several laws of growth. Hence, in +fact, the law of the Conditions of Existence is the higher law; as it +includes, through the inheritance of former adaptations, that of Unity +of Type. + +CHAPTER VII. INSTINCT. -The subject of instinct might have been worked into the previous chapters; but -I have thought that it would be more convenient to treat the subject -separately, especially as so wonderful an instinct as that of the hive-bee -making its cells will probably have occurred to many readers, as a difficulty -sufficient to overthrow my whole theory. I must premise, that I have nothing to -do with the origin of the primary mental powers, any more than I have with that -of life itself. We are concerned only with the diversities of instinct and of -the other mental qualities of animals within the same class. - -I will not attempt any definition of instinct. It would be easy to show that -several distinct mental actions are commonly embraced by this term; but every -one understands what is meant, when it is said that instinct impels the cuckoo -to migrate and to lay her eggs in other birds’ nests. An action, which we -ourselves should require experience to enable us to perform, when performed by -an animal, more especially by a very young one, without any experience, and -when performed by many individuals in the same way, without their knowing for -what purpose it is performed, is usually said to be instinctive. But I could -show that none of these characters of instinct are universal. A little dose, as -Pierre Huber expresses it, of judgment or reason, often comes into play, even -in animals very low in the scale of nature. - -Frederick Cuvier and several of the older metaphysicians have compared instinct -with habit. This comparison gives, I think, a remarkably accurate notion of the -frame of mind under which an instinctive action is performed, but not of its -origin. How unconsciously many habitual actions are performed, indeed not -rarely in direct opposition to our conscious will! yet they may be modified by -the will or reason. Habits easily become associated with other habits, and with -certain periods of time and states of the body. When once acquired, they often -remain constant throughout life. Several other points of resemblance between -instincts and habits could be pointed out. As in repeating a well-known song, -so in instincts, one action follows another by a sort of rhythm; if a person be -interrupted in a song, or in repeating anything by rote, he is generally forced -to go back to recover the habitual train of thought: so P. Huber found it was -with a caterpillar, which makes a very complicated hammock; for if he took a -caterpillar which had completed its hammock up to, say, the sixth stage of -construction, and put it into a hammock completed up only to the third stage, -the caterpillar simply re-performed the fourth, fifth, and sixth stages of -construction. If, however, a caterpillar were taken out of a hammock made up, -for instance, to the third stage, and were put into one finished up to the -sixth stage, so that much of its work was already done for it, far from feeling -the benefit of this, it was much embarrassed, and, in order to complete its -hammock, seemed forced to start from the third stage, where it had left off, -and thus tried to complete the already finished work. - -If we suppose any habitual action to become inherited—and I think it can be -shown that this does sometimes happen—then the resemblance between what -originally was a habit and an instinct becomes so close as not to be -distinguished. If Mozart, instead of playing the pianoforte at three years old -with wonderfully little practice, had played a tune with no practice at all, he -might truly be said to have done so instinctively. But it would be the most -serious error to suppose that the greater number of instincts have been -acquired by habit in one generation, and then transmitted by inheritance to -succeeding generations. It can be clearly shown that the most wonderful -instincts with which we are acquainted, namely, those of the hive-bee and of -many ants, could not possibly have been thus acquired. - -It will be universally admitted that instincts are as important as corporeal -structure for the welfare of each species, under its present conditions of -life. Under changed conditions of life, it is at least possible that slight -modifications of instinct might be profitable to a species; and if it can be -shown that instincts do vary ever so little, then I can see no difficulty in -natural selection preserving and continually accumulating variations of -instinct to any extent that may be profitable. It is thus, as I believe, that -all the most complex and wonderful instincts have originated. As modifications -of corporeal structure arise from, and are increased by, use or habit, and are -diminished or lost by disuse, so I do not doubt it has been with instincts. But -I believe that the effects of habit are of quite subordinate importance to the -effects of the natural selection of what may be called accidental variations of -instincts;—that is of variations produced by the same unknown causes which -produce slight deviations of bodily structure. - -No complex instinct can possibly be produced through natural selection, except -by the slow and gradual accumulation of numerous, slight, yet profitable, -variations. Hence, as in the case of corporeal structures, we ought to find in -nature, not the actual transitional gradations by which each complex instinct -has been acquired—for these could be found only in the lineal ancestors of each -species—but we ought to find in the collateral lines of descent some evidence -of such gradations; or we ought at least to be able to show that gradations of -some kind are possible; and this we certainly can do. I have been surprised to -find, making allowance for the instincts of animals having been but little -observed except in Europe and North America, and for no instinct being known -amongst extinct species, how very generally gradations, leading to the most -complex instincts, can be discovered. The canon of “Natura non facit saltum” -applies with almost equal force to instincts as to bodily organs. Changes of -instinct may sometimes be facilitated by the same species having different -instincts at different periods of life, or at different seasons of the year, or -when placed under different circumstances, etc.; in which case either one or -the other instinct might be preserved by natural selection. And such instances -of diversity of instinct in the same species can be shown to occur in nature. - -Again as in the case of corporeal structure, and conformably with my theory, -the instinct of each species is good for itself, but has never, as far as we -can judge, been produced for the exclusive good of others. One of the strongest -instances of an animal apparently performing an action for the sole good of -another, with which I am acquainted, is that of aphides voluntarily yielding -their sweet excretion to ants: that they do so voluntarily, the following facts -show. I removed all the ants from a group of about a dozen aphides on a -dock-plant, and prevented their attendance during several hours. After this -interval, I felt sure that the aphides would want to excrete. I watched them -for some time through a lens, but not one excreted; I then tickled and stroked -them with a hair in the same manner, as well as I could, as the ants do with -their antennæ; but not one excreted. Afterwards I allowed an ant to visit them, -and it immediately seemed, by its eager way of running about, to be well aware -what a rich flock it had discovered; it then began to play with its antennæ on -the abdomen first of one aphis and then of another; and each aphis, as soon as -it felt the antennæ, immediately lifted up its abdomen and excreted a limpid -drop of sweet juice, which was eagerly devoured by the ant. Even the quite -young aphides behaved in this manner, showing that the action was instinctive, -and not the result of experience. But as the excretion is extremely viscid, it -is probably a convenience to the aphides to have it removed; and therefore -probably the aphides do not instinctively excrete for the sole good of the -ants. Although I do not believe that any animal in the world performs an action -for the exclusive good of another of a distinct species, yet each species tries -to take advantage of the instincts of others, as each takes advantage of the -weaker bodily structure of others. So again, in some few cases, certain -instincts cannot be considered as absolutely perfect; but as details on this -and other such points are not indispensable, they may be here passed over. - -As some degree of variation in instincts under a state of nature, and the -inheritance of such variations, are indispensable for the action of natural -selection, as many instances as possible ought to have been here given; but -want of space prevents me. I can only assert, that instincts certainly do -vary—for instance, the migratory instinct, both in extent and direction, and in -its total loss. So it is with the nests of birds, which vary partly in -dependence on the situations chosen, and on the nature and temperature of the -country inhabited, but often from causes wholly unknown to us: Audubon has -given several remarkable cases of differences in nests of the same species in -the northern and southern United States. Fear of any particular enemy is -certainly an instinctive quality, as may be seen in nestling birds, though it -is strengthened by experience, and by the sight of fear of the same enemy in -other animals. But fear of man is slowly acquired, as I have elsewhere shown, -by various animals inhabiting desert islands; and we may see an instance of -this, even in England, in the greater wildness of all our large birds than of -our small birds; for the large birds have been most persecuted by man. We may -safely attribute the greater wildness of our large birds to this cause; for in -uninhabited islands large birds are not more fearful than small; and the -magpie, so wary in England, is tame in Norway, as is the hooded crow in Egypt. - -That the general disposition of individuals of the same species, born in a -state of nature, is extremely diversified, can be shown by a multitude of -facts. Several cases also, could be given, of occasional and strange habits in -certain species, which might, if advantageous to the species, give rise, -through natural selection, to quite new instincts. But I am well aware that -these general statements, without facts given in detail, can produce but a -feeble effect on the reader’s mind. I can only repeat my assurance, that I do -not speak without good evidence. - -The possibility, or even probability, of inherited variations of instinct in a -state of nature will be strengthened by briefly considering a few cases under -domestication. We shall thus also be enabled to see the respective parts which -habit and the selection of so-called accidental variations have played in -modifying the mental qualities of our domestic animals. A number of curious and -authentic instances could be given of the inheritance of all shades of -disposition and tastes, and likewise of the oddest tricks, associated with -certain frames of mind or periods of time. But let us look to the familiar case -of the several breeds of dogs: it cannot be doubted that young pointers (I have -myself seen a striking instance) will sometimes point and even back other dogs -the very first time that they are taken out; retrieving is certainly in some -degree inherited by retrievers; and a tendency to run round, instead of at, a -flock of sheep, by shepherd-dogs. I cannot see that these actions, performed -without experience by the young, and in nearly the same manner by each -individual, performed with eager delight by each breed, and without the end -being known,—for the young pointer can no more know that he points to aid his -master, than the white butterfly knows why she lays her eggs on the leaf of the +Instincts comparable with habits, but different in their origin. +Instincts graduated. Aphides and ants. Instincts variable. Domestic +instincts, their origin. Natural instincts of the cuckoo, ostrich, and +parasitic bees. Slave-making ants. Hive-bee, its cell-making instinct. +Difficulties on the theory of the Natural Selection of instincts. Neuter +or sterile insects. Summary. + +The subject of instinct might have been worked into the previous +chapters; but I have thought that it would be more convenient to treat +the subject separately, especially as so wonderful an instinct as that +of the hive-bee making its cells will probably have occurred to many +readers, as a difficulty sufficient to overthrow my whole theory. I must +premise, that I have nothing to do with the origin of the primary mental +powers, any more than I have with that of life itself. We are concerned +only with the diversities of instinct and of the other mental qualities +of animals within the same class. + +I will not attempt any definition of instinct. It would be easy to show +that several distinct mental actions are commonly embraced by this term; +but every one understands what is meant, when it is said that instinct +impels the cuckoo to migrate and to lay her eggs in other birds’ nests. +An action, which we ourselves should require experience to enable us to +perform, when performed by an animal, more especially by a very young +one, without any experience, and when performed by many individuals in +the same way, without their knowing for what purpose it is performed, is +usually said to be instinctive. But I could show that none of these +characters of instinct are universal. A little dose, as Pierre Huber +expresses it, of judgment or reason, often comes into play, even in +animals very low in the scale of nature. + +Frederick Cuvier and several of the older metaphysicians have compared +instinct with habit. This comparison gives, I think, a remarkably +accurate notion of the frame of mind under which an instinctive action +is performed, but not of its origin. How unconsciously many habitual +actions are performed, indeed not rarely in direct opposition to our +conscious will! yet they may be modified by the will or reason. Habits +easily become associated with other habits, and with certain periods of +time and states of the body. When once acquired, they often remain +constant throughout life. Several other points of resemblance between +instincts and habits could be pointed out. As in repeating a well-known +song, so in instincts, one action follows another by a sort of rhythm; +if a person be interrupted in a song, or in repeating anything by rote, +he is generally forced to go back to recover the habitual train of +thought: so P. Huber found it was with a caterpillar, which makes a very +complicated hammock; for if he took a caterpillar which had completed +its hammock up to, say, the sixth stage of construction, and put it into +a hammock completed up only to the third stage, the caterpillar simply +re-performed the fourth, fifth, and sixth stages of construction. If, +however, a caterpillar were taken out of a hammock made up, for +instance, to the third stage, and were put into one finished up to the +sixth stage, so that much of its work was already done for it, far from +feeling the benefit of this, it was much embarrassed, and, in order to +complete its hammock, seemed forced to start from the third stage, where +it had left off, and thus tried to complete the already finished work. + +If we suppose any habitual action to become inherited—and I think it can +be shown that this does sometimes happen—then the resemblance between +what originally was a habit and an instinct becomes so close as not to +be distinguished. If Mozart, instead of playing the pianoforte at three +years old with wonderfully little practice, had played a tune with no +practice at all, he might truly be said to have done so instinctively. +But it would be the most serious error to suppose that the greater +number of instincts have been acquired by habit in one generation, and +then transmitted by inheritance to succeeding generations. It can be +clearly shown that the most wonderful instincts with which we are +acquainted, namely, those of the hive-bee and of many ants, could not +possibly have been thus acquired. + +It will be universally admitted that instincts are as important as +corporeal structure for the welfare of each species, under its present +conditions of life. Under changed conditions of life, it is at least +possible that slight modifications of instinct might be profitable to a +species; and if it can be shown that instincts do vary ever so little, +then I can see no difficulty in natural selection preserving and +continually accumulating variations of instinct to any extent that may +be profitable. It is thus, as I believe, that all the most complex and +wonderful instincts have originated. As modifications of corporeal +structure arise from, and are increased by, use or habit, and are +diminished or lost by disuse, so I do not doubt it has been with +instincts. But I believe that the effects of habit are of quite +subordinate importance to the effects of the natural selection of what +may be called accidental variations of instincts;—that is of variations +produced by the same unknown causes which produce slight deviations of +bodily structure. + +No complex instinct can possibly be produced through natural selection, +except by the slow and gradual accumulation of numerous, slight, yet +profitable, variations. Hence, as in the case of corporeal structures, +we ought to find in nature, not the actual transitional gradations by +which each complex instinct has been acquired—for these could be found +only in the lineal ancestors of each species—but we ought to find in the +collateral lines of descent some evidence of such gradations; or we +ought at least to be able to show that gradations of some kind are +possible; and this we certainly can do. I have been surprised to find, +making allowance for the instincts of animals having been but little +observed except in Europe and North America, and for no instinct being +known amongst extinct species, how very generally gradations, leading to +the most complex instincts, can be discovered. The canon of “Natura non +facit saltum” applies with almost equal force to instincts as to bodily +organs. Changes of instinct may sometimes be facilitated by the same +species having different instincts at different periods of life, or at +different seasons of the year, or when placed under different +circumstances, etc.; in which case either one or the other instinct +might be preserved by natural selection. And such instances of diversity +of instinct in the same species can be shown to occur in nature. + +Again as in the case of corporeal structure, and conformably with my +theory, the instinct of each species is good for itself, but has never, +as far as we can judge, been produced for the exclusive good of others. +One of the strongest instances of an animal apparently performing an +action for the sole good of another, with which I am acquainted, is that +of aphides voluntarily yielding their sweet excretion to ants: that they +do so voluntarily, the following facts show. I removed all the ants from +a group of about a dozen aphides on a dock-plant, and prevented their +attendance during several hours. After this interval, I felt sure that +the aphides would want to excrete. I watched them for some time through +a lens, but not one excreted; I then tickled and stroked them with a +hair in the same manner, as well as I could, as the ants do with their +antennæ; but not one excreted. Afterwards I allowed an ant to visit +them, and it immediately seemed, by its eager way of running about, to +be well aware what a rich flock it had discovered; it then began to play +with its antennæ on the abdomen first of one aphis and then of another; +and each aphis, as soon as it felt the antennæ, immediately lifted up +its abdomen and excreted a limpid drop of sweet juice, which was eagerly +devoured by the ant. Even the quite young aphides behaved in this +manner, showing that the action was instinctive, and not the result of +experience. But as the excretion is extremely viscid, it is probably a +convenience to the aphides to have it removed; and therefore probably +the aphides do not instinctively excrete for the sole good of the ants. +Although I do not believe that any animal in the world performs an +action for the exclusive good of another of a distinct species, yet each +species tries to take advantage of the instincts of others, as each +takes advantage of the weaker bodily structure of others. So again, in +some few cases, certain instincts cannot be considered as absolutely +perfect; but as details on this and other such points are not +indispensable, they may be here passed over. + +As some degree of variation in instincts under a state of nature, and +the inheritance of such variations, are indispensable for the action of +natural selection, as many instances as possible ought to have been here +given; but want of space prevents me. I can only assert, that instincts +certainly do vary—for instance, the migratory instinct, both in extent +and direction, and in its total loss. So it is with the nests of birds, +which vary partly in dependence on the situations chosen, and on the +nature and temperature of the country inhabited, but often from causes +wholly unknown to us: Audubon has given several remarkable cases of +differences in nests of the same species in the northern and southern +United States. Fear of any particular enemy is certainly an instinctive +quality, as may be seen in nestling birds, though it is strengthened by +experience, and by the sight of fear of the same enemy in other animals. +But fear of man is slowly acquired, as I have elsewhere shown, by +various animals inhabiting desert islands; and we may see an instance of +this, even in England, in the greater wildness of all our large birds +than of our small birds; for the large birds have been most persecuted +by man. We may safely attribute the greater wildness of our large birds +to this cause; for in uninhabited islands large birds are not more +fearful than small; and the magpie, so wary in England, is tame in +Norway, as is the hooded crow in Egypt. + +That the general disposition of individuals of the same species, born in +a state of nature, is extremely diversified, can be shown by a multitude +of facts. Several cases also, could be given, of occasional and strange +habits in certain species, which might, if advantageous to the species, +give rise, through natural selection, to quite new instincts. But I am +well aware that these general statements, without facts given in detail, +can produce but a feeble effect on the reader’s mind. I can only repeat +my assurance, that I do not speak without good evidence. + +The possibility, or even probability, of inherited variations of +instinct in a state of nature will be strengthened by briefly +considering a few cases under domestication. We shall thus also be +enabled to see the respective parts which habit and the selection of +so-called accidental variations have played in modifying the mental +qualities of our domestic animals. A number of curious and authentic +instances could be given of the inheritance of all shades of disposition +and tastes, and likewise of the oddest tricks, associated with certain +frames of mind or periods of time. But let us look to the familiar case +of the several breeds of dogs: it cannot be doubted that young pointers +(I have myself seen a striking instance) will sometimes point and even +back other dogs the very first time that they are taken out; retrieving +is certainly in some degree inherited by retrievers; and a tendency to +run round, instead of at, a flock of sheep, by shepherd-dogs. I cannot +see that these actions, performed without experience by the young, and +in nearly the same manner by each individual, performed with eager +delight by each breed, and without the end being known,—for the young +pointer can no more know that he points to aid his master, than the +white butterfly knows why she lays her eggs on the leaf of the cabbage,—I cannot see that these actions differ essentially from true -instincts. If we were to see one kind of wolf, when young and without any -training, as soon as it scented its prey, stand motionless like a statue, and -then slowly crawl forward with a peculiar gait; and another kind of wolf -rushing round, instead of at, a herd of deer, and driving them to a distant -point, we should assuredly call these actions instinctive. Domestic instincts, -as they may be called, are certainly far less fixed or invariable than natural -instincts; but they have been acted on by far less rigorous selection, and have -been transmitted for an incomparably shorter period, under less fixed -conditions of life. - -How strongly these domestic instincts, habits, and dispositions are inherited, -and how curiously they become mingled, is well shown when different breeds of -dogs are crossed. Thus it is known that a cross with a bull-dog has affected -for many generations the courage and obstinacy of greyhounds; and a cross with -a greyhound has given to a whole family of shepherd-dogs a tendency to hunt -hares. These domestic instincts, when thus tested by crossing, resemble natural -instincts, which in a like manner become curiously blended together, and for a -long period exhibit traces of the instincts of either parent: for example, Le -Roy describes a dog, whose great-grandfather was a wolf, and this dog showed a -trace of its wild parentage only in one way, by not coming in a straight line -to his master when called. +instincts. If we were to see one kind of wolf, when young and without +any training, as soon as it scented its prey, stand motionless like a +statue, and then slowly crawl forward with a peculiar gait; and another +kind of wolf rushing round, instead of at, a herd of deer, and driving +them to a distant point, we should assuredly call these actions +instinctive. Domestic instincts, as they may be called, are certainly +far less fixed or invariable than natural instincts; but they have been +acted on by far less rigorous selection, and have been transmitted for +an incomparably shorter period, under less fixed conditions of life. + +How strongly these domestic instincts, habits, and dispositions are +inherited, and how curiously they become mingled, is well shown when +different breeds of dogs are crossed. Thus it is known that a cross with +a bull-dog has affected for many generations the courage and obstinacy +of greyhounds; and a cross with a greyhound has given to a whole family +of shepherd-dogs a tendency to hunt hares. These domestic instincts, +when thus tested by crossing, resemble natural instincts, which in a +like manner become curiously blended together, and for a long period +exhibit traces of the instincts of either parent: for example, Le Roy +describes a dog, whose great-grandfather was a wolf, and this dog showed +a trace of its wild parentage only in one way, by not coming in a +straight line to his master when called. Domestic instincts are sometimes spoken of as actions which have become -inherited solely from long-continued and compulsory habit, but this, I think, -is not true. No one would ever have thought of teaching, or probably could have -taught, the tumbler-pigeon to tumble,—an action which, as I have witnessed, is -performed by young birds, that have never seen a pigeon tumble. We may believe -that some one pigeon showed a slight tendency to this strange habit, and that -the long-continued selection of the best individuals in successive generations -made tumblers what they now are; and near Glasgow there are house-tumblers, as -I hear from Mr. Brent, which cannot fly eighteen inches high without going head -over heels. It may be doubted whether any one would have thought of training a -dog to point, had not some one dog naturally shown a tendency in this line; and -this is known occasionally to happen, as I once saw in a pure terrier. When the -first tendency was once displayed, methodical selection and the inherited -effects of compulsory training in each successive generation would soon -complete the work; and unconscious selection is still at work, as each man -tries to procure, without intending to improve the breed, dogs which will stand -and hunt best. On the other hand, habit alone in some cases has sufficed; no -animal is more difficult to tame than the young of the wild rabbit; scarcely -any animal is tamer than the young of the tame rabbit; but I do not suppose -that domestic rabbits have ever been selected for tameness; and I presume that -we must attribute the whole of the inherited change from extreme wildness to -extreme tameness, simply to habit and long-continued close confinement. - -Natural instincts are lost under domestication: a remarkable instance of this -is seen in those breeds of fowls which very rarely or never become “broody,” -that is, never wish to sit on their eggs. Familiarity alone prevents our seeing -how universally and largely the minds of our domestic animals have been -modified by domestication. It is scarcely possible to doubt that the love of -man has become instinctive in the dog. All wolves, foxes, jackals, and species -of the cat genus, when kept tame, are most eager to attack poultry, sheep, and -pigs; and this tendency has been found incurable in dogs which have been -brought home as puppies from countries, such as Tierra del Fuego and Australia, -where the savages do not keep these domestic animals. How rarely, on the other -hand, do our civilised dogs, even when quite young, require to be taught not to -attack poultry, sheep, and pigs! No doubt they occasionally do make an attack, -and are then beaten; and if not cured, they are destroyed; so that habit, with -some degree of selection, has probably concurred in civilising by inheritance -our dogs. On the other hand, young chickens have lost, wholly by habit, that -fear of the dog and cat which no doubt was originally instinctive in them, in -the same way as it is so plainly instinctive in young pheasants, though reared -under a hen. It is not that chickens have lost all fear, but fear only of dogs -and cats, for if the hen gives the danger-chuckle, they will run (more +inherited solely from long-continued and compulsory habit, but this, I +think, is not true. No one would ever have thought of teaching, or +probably could have taught, the tumbler-pigeon to tumble,—an action +which, as I have witnessed, is performed by young birds, that have never +seen a pigeon tumble. We may believe that some one pigeon showed a +slight tendency to this strange habit, and that the long-continued +selection of the best individuals in successive generations made +tumblers what they now are; and near Glasgow there are house-tumblers, +as I hear from Mr. Brent, which cannot fly eighteen inches high without +going head over heels. It may be doubted whether any one would have +thought of training a dog to point, had not some one dog naturally shown +a tendency in this line; and this is known occasionally to happen, as I +once saw in a pure terrier. When the first tendency was once displayed, +methodical selection and the inherited effects of compulsory training in +each successive generation would soon complete the work; and unconscious +selection is still at work, as each man tries to procure, without +intending to improve the breed, dogs which will stand and hunt best. On +the other hand, habit alone in some cases has sufficed; no animal is +more difficult to tame than the young of the wild rabbit; scarcely any +animal is tamer than the young of the tame rabbit; but I do not suppose +that domestic rabbits have ever been selected for tameness; and I +presume that we must attribute the whole of the inherited change from +extreme wildness to extreme tameness, simply to habit and long-continued +close confinement. + +Natural instincts are lost under domestication: a remarkable instance of +this is seen in those breeds of fowls which very rarely or never become +“broody,” that is, never wish to sit on their eggs. Familiarity alone +prevents our seeing how universally and largely the minds of our +domestic animals have been modified by domestication. It is scarcely +possible to doubt that the love of man has become instinctive in the +dog. All wolves, foxes, jackals, and species of the cat genus, when kept +tame, are most eager to attack poultry, sheep, and pigs; and this +tendency has been found incurable in dogs which have been brought home +as puppies from countries, such as Tierra del Fuego and Australia, where +the savages do not keep these domestic animals. How rarely, on the other +hand, do our civilised dogs, even when quite young, require to be taught +not to attack poultry, sheep, and pigs! No doubt they occasionally do +make an attack, and are then beaten; and if not cured, they are +destroyed; so that habit, with some degree of selection, has probably +concurred in civilising by inheritance our dogs. On the other hand, +young chickens have lost, wholly by habit, that fear of the dog and cat +which no doubt was originally instinctive in them, in the same way as it +is so plainly instinctive in young pheasants, though reared under a hen. +It is not that chickens have lost all fear, but fear only of dogs and +cats, for if the hen gives the danger-chuckle, they will run (more especially young turkeys) from under her, and conceal themselves in the -surrounding grass or thickets; and this is evidently done for the instinctive -purpose of allowing, as we see in wild ground-birds, their mother to fly away. -But this instinct retained by our chickens has become useless under -domestication, for the mother-hen has almost lost by disuse the power of -flight. - -Hence, we may conclude, that domestic instincts have been acquired and natural -instincts have been lost partly by habit, and partly by man selecting and -accumulating during successive generations, peculiar mental habits and actions, -which at first appeared from what we must in our ignorance call an accident. In -some cases compulsory habit alone has sufficed to produce such inherited mental -changes; in other cases compulsory habit has done nothing, and all has been the -result of selection, pursued both methodically and unconsciously; but in most +surrounding grass or thickets; and this is evidently done for the +instinctive purpose of allowing, as we see in wild ground-birds, their +mother to fly away. But this instinct retained by our chickens has +become useless under domestication, for the mother-hen has almost lost +by disuse the power of flight. + +Hence, we may conclude, that domestic instincts have been acquired and +natural instincts have been lost partly by habit, and partly by man +selecting and accumulating during successive generations, peculiar +mental habits and actions, which at first appeared from what we must in +our ignorance call an accident. In some cases compulsory habit alone has +sufficed to produce such inherited mental changes; in other cases +compulsory habit has done nothing, and all has been the result of +selection, pursued both methodically and unconsciously; but in most cases, probably, habit and selection have acted together. -We shall, perhaps, best understand how instincts in a state of nature have -become modified by selection, by considering a few cases. I will select only -three, out of the several which I shall have to discuss in my future -work,—namely, the instinct which leads the cuckoo to lay her eggs in other -birds’ nests; the slave-making instinct of certain ants; and the comb-making -power of the hive-bee: these two latter instincts have generally, and most -justly, been ranked by naturalists as the most wonderful of all known -instincts. - -It is now commonly admitted that the more immediate and final cause of the -cuckoo’s instinct is, that she lays her eggs, not daily, but at intervals of -two or three days; so that, if she were to make her own nest and sit on her own -eggs, those first laid would have to be left for some time unincubated, or -there would be eggs and young birds of different ages in the same nest. If this -were the case, the process of laying and hatching might be inconveniently long, -more especially as she has to migrate at a very early period; and the first -hatched young would probably have to be fed by the male alone. But the American -cuckoo is in this predicament; for she makes her own nest and has eggs and -young successively hatched, all at the same time. It has been asserted that the -American cuckoo occasionally lays her eggs in other birds’ nests; but I hear on -the high authority of Dr. Brewer, that this is a mistake. Nevertheless, I could -give several instances of various birds which have been known occasionally to -lay their eggs in other birds’ nests. Now let us suppose that the ancient -progenitor of our European cuckoo had the habits of the American cuckoo; but -that occasionally she laid an egg in another bird’s nest. If the old bird -profited by this occasional habit, or if the young were made more vigorous by -advantage having been taken of the mistaken maternal instinct of another bird, -than by their own mother’s care, encumbered as she can hardly fail to be by -having eggs and young of different ages at the same time; then the old birds or -the fostered young would gain an advantage. And analogy would lead me to -believe, that the young thus reared would be apt to follow by inheritance the -occasional and aberrant habit of their mother, and in their turn would be apt -to lay their eggs in other birds’ nests, and thus be successful in rearing -their young. By a continued process of this nature, I believe that the strange -instinct of our cuckoo could be, and has been, generated. I may add that, -according to Dr. Gray and to some other observers, the European cuckoo has not -utterly lost all maternal love and care for her own offspring. - -The occasional habit of birds laying their eggs in other birds’ nests, either -of the same or of a distinct species, is not very uncommon with the Gallinaceæ; -and this perhaps explains the origin of a singular instinct in the allied group -of ostriches. For several hen ostriches, at least in the case of the American -species, unite and lay first a few eggs in one nest and then in another; and -these are hatched by the males. This instinct may probably be accounted for by -the fact of the hens laying a large number of eggs; but, as in the case of the -cuckoo, at intervals of two or three days. This instinct, however, of the -American ostrich has not as yet been perfected; for a surprising number of eggs -lie strewed over the plains, so that in one day’s hunting I picked up no less -than twenty lost and wasted eggs. - -Many bees are parasitic, and always lay their eggs in the nests of bees of -other kinds. This case is more remarkable than that of the cuckoo; for these -bees have not only their instincts but their structure modified in accordance -with their parasitic habits; for they do not possess the pollen-collecting -apparatus which would be necessary if they had to store food for their own -young. Some species, likewise, of Sphegidæ (wasp-like insects) are parasitic on -other species; and M. Fabre has lately shown good reason for believing that -although the Tachytes nigra generally makes its own burrow and stores it with -paralysed prey for its own larvæ to feed on, yet that when this insect finds a -burrow already made and stored by another sphex, it takes advantage of the -prize, and becomes for the occasion parasitic. In this case, as with the -supposed case of the cuckoo, I can see no difficulty in natural selection -making an occasional habit permanent, if of advantage to the species, and if -the insect whose nest and stored food are thus feloniously appropriated, be not -thus exterminated. - -Slave-making instinct.—This remarkable instinct was first discovered in the -Formica (Polyerges) rufescens by Pierre Huber, a better observer even than his -celebrated father. This ant is absolutely dependent on its slaves; without -their aid, the species would certainly become extinct in a single year. The -males and fertile females do no work. The workers or sterile females, though -most energetic and courageous in capturing slaves, do no other work. They are -incapable of making their own nests, or of feeding their own larvæ. When the -old nest is found inconvenient, and they have to migrate, it is the slaves -which determine the migration, and actually carry their masters in their jaws. -So utterly helpless are the masters, that when Huber shut up thirty of them -without a slave, but with plenty of the food which they like best, and with -their larvæ and pupæ to stimulate them to work, they did nothing; they could -not even feed themselves, and many perished of hunger. Huber then introduced a -single slave (F. fusca), and she instantly set to work, fed and saved the -survivors; made some cells and tended the larvæ, and put all to rights. What -can be more extraordinary than these well-ascertained facts? If we had not -known of any other slave-making ant, it would have been hopeless to have -speculated how so wonderful an instinct could have been perfected. +We shall, perhaps, best understand how instincts in a state of nature +have become modified by selection, by considering a few cases. I will +select only three, out of the several which I shall have to discuss in +my future work,—namely, the instinct which leads the cuckoo to lay her +eggs in other birds’ nests; the slave-making instinct of certain ants; +and the comb-making power of the hive-bee: these two latter instincts +have generally, and most justly, been ranked by naturalists as the most +wonderful of all known instincts. + +It is now commonly admitted that the more immediate and final cause of +the cuckoo’s instinct is, that she lays her eggs, not daily, but at +intervals of two or three days; so that, if she were to make her own +nest and sit on her own eggs, those first laid would have to be left for +some time unincubated, or there would be eggs and young birds of +different ages in the same nest. If this were the case, the process of +laying and hatching might be inconveniently long, more especially as she +has to migrate at a very early period; and the first hatched young would +probably have to be fed by the male alone. But the American cuckoo is in +this predicament; for she makes her own nest and has eggs and young +successively hatched, all at the same time. It has been asserted that +the American cuckoo occasionally lays her eggs in other birds’ nests; +but I hear on the high authority of Dr. Brewer, that this is a mistake. +Nevertheless, I could give several instances of various birds which have +been known occasionally to lay their eggs in other birds’ nests. Now let +us suppose that the ancient progenitor of our European cuckoo had the +habits of the American cuckoo; but that occasionally she laid an egg in +another bird’s nest. If the old bird profited by this occasional habit, +or if the young were made more vigorous by advantage having been taken +of the mistaken maternal instinct of another bird, than by their own +mother’s care, encumbered as she can hardly fail to be by having eggs +and young of different ages at the same time; then the old birds or the +fostered young would gain an advantage. And analogy would lead me to +believe, that the young thus reared would be apt to follow by +inheritance the occasional and aberrant habit of their mother, and in +their turn would be apt to lay their eggs in other birds’ nests, and +thus be successful in rearing their young. By a continued process of +this nature, I believe that the strange instinct of our cuckoo could be, +and has been, generated. I may add that, according to Dr. Gray and to +some other observers, the European cuckoo has not utterly lost all +maternal love and care for her own offspring. + +The occasional habit of birds laying their eggs in other birds’ nests, +either of the same or of a distinct species, is not very uncommon with +the Gallinaceæ; and this perhaps explains the origin of a singular +instinct in the allied group of ostriches. For several hen ostriches, at +least in the case of the American species, unite and lay first a few +eggs in one nest and then in another; and these are hatched by the +males. This instinct may probably be accounted for by the fact of the +hens laying a large number of eggs; but, as in the case of the cuckoo, +at intervals of two or three days. This instinct, however, of the +American ostrich has not as yet been perfected; for a surprising number +of eggs lie strewed over the plains, so that in one day’s hunting I +picked up no less than twenty lost and wasted eggs. + +Many bees are parasitic, and always lay their eggs in the nests of bees +of other kinds. This case is more remarkable than that of the cuckoo; +for these bees have not only their instincts but their structure +modified in accordance with their parasitic habits; for they do not +possess the pollen-collecting apparatus which would be necessary if they +had to store food for their own young. Some species, likewise, of +Sphegidæ (wasp-like insects) are parasitic on other species; and M. +Fabre has lately shown good reason for believing that although the +Tachytes nigra generally makes its own burrow and stores it with +paralysed prey for its own larvæ to feed on, yet that when this insect +finds a burrow already made and stored by another sphex, it takes +advantage of the prize, and becomes for the occasion parasitic. In this +case, as with the supposed case of the cuckoo, I can see no difficulty +in natural selection making an occasional habit permanent, if of +advantage to the species, and if the insect whose nest and stored food +are thus feloniously appropriated, be not thus exterminated. + +Slave-making instinct.—This remarkable instinct was first discovered in +the Formica (Polyerges) rufescens by Pierre Huber, a better observer +even than his celebrated father. This ant is absolutely dependent on its +slaves; without their aid, the species would certainly become extinct in +a single year. The males and fertile females do no work. The workers or +sterile females, though most energetic and courageous in capturing +slaves, do no other work. They are incapable of making their own nests, +or of feeding their own larvæ. When the old nest is found inconvenient, +and they have to migrate, it is the slaves which determine the +migration, and actually carry their masters in their jaws. So utterly +helpless are the masters, that when Huber shut up thirty of them without +a slave, but with plenty of the food which they like best, and with +their larvæ and pupæ to stimulate them to work, they did nothing; they +could not even feed themselves, and many perished of hunger. Huber then +introduced a single slave (F. fusca), and she instantly set to work, fed +and saved the survivors; made some cells and tended the larvæ, and put +all to rights. What can be more extraordinary than these +well-ascertained facts? If we had not known of any other slave-making +ant, it would have been hopeless to have speculated how so wonderful an +instinct could have been perfected. Formica sanguinea was likewise first discovered by P. Huber to be a -slave-making ant. This species is found in the southern parts of England, and -its habits have been attended to by Mr. F. Smith, of the British Museum, to -whom I am much indebted for information on this and other subjects. Although -fully trusting to the statements of Huber and Mr. Smith, I tried to approach -the subject in a sceptical frame of mind, as any one may well be excused for -doubting the truth of so extraordinary and odious an instinct as that of making -slaves. Hence I will give the observations which I have myself made, in some -little detail. I opened fourteen nests of F. sanguinea, and found a few slaves -in all. Males and fertile females of the slave-species are found only in their -own proper communities, and have never been observed in the nests of F. -sanguinea. The slaves are black and not above half the size of their red -masters, so that the contrast in their appearance is very great. When the nest -is slightly disturbed, the slaves occasionally come out, and like their masters -are much agitated and defend the nest: when the nest is much disturbed and the -larvæ and pupæ are exposed, the slaves work energetically with their masters in -carrying them away to a place of safety. Hence, it is clear, that the slaves -feel quite at home. During the months of June and July, on three successive -years, I have watched for many hours several nests in Surrey and Sussex, and -never saw a slave either leave or enter a nest. As, during these months, the -slaves are very few in number, I thought that they might behave differently -when more numerous; but Mr. Smith informs me that he has watched the nests at -various hours during May, June and August, both in Surrey and Hampshire, and -has never seen the slaves, though present in large numbers in August, either -leave or enter the nest. Hence he considers them as strictly household slaves. -The masters, on the other hand, may be constantly seen bringing in materials -for the nest, and food of all kinds. During the present year, however, in the -month of July, I came across a community with an unusually large stock of -slaves, and I observed a few slaves mingled with their masters leaving the -nest, and marching along the same road to a tall Scotch-fir-tree, twenty-five -yards distant, which they ascended together, probably in search of aphides or -cocci. According to Huber, who had ample opportunities for observation, in -Switzerland the slaves habitually work with their masters in making the nest, -and they alone open and close the doors in the morning and evening; and, as -Huber expressly states, their principal office is to search for aphides. This -difference in the usual habits of the masters and slaves in the two countries, -probably depends merely on the slaves being captured in greater numbers in -Switzerland than in England. - -One day I fortunately chanced to witness a migration from one nest to another, -and it was a most interesting spectacle to behold the masters carefully -carrying, as Huber has described, their slaves in their jaws. Another day my -attention was struck by about a score of the slave-makers haunting the same -spot, and evidently not in search of food; they approached and were vigorously -repulsed by an independent community of the slave species (F. fusca); sometimes -as many as three of these ants clinging to the legs of the slave-making F. -sanguinea. The latter ruthlessly killed their small opponents, and carried -their dead bodies as food to their nest, twenty-nine yards distant; but they -were prevented from getting any pupæ to rear as slaves. I then dug up a small -parcel of the pupæ of F. fusca from another nest, and put them down on a bare -spot near the place of combat; they were eagerly seized, and carried off by the -tyrants, who perhaps fancied that, after all, they had been victorious in their -late combat. - -At the same time I laid on the same place a small parcel of the pupæ of another -species, F. flava, with a few of these little yellow ants still clinging to the -fragments of the nest. This species is sometimes, though rarely, made into -slaves, as has been described by Mr. Smith. Although so small a species, it is -very courageous, and I have seen it ferociously attack other ants. In one -instance I found to my surprise an independent community of F. flava under a -stone beneath a nest of the slave-making F. sanguinea; and when I had -accidentally disturbed both nests, the little ants attacked their big -neighbours with surprising courage. Now I was curious to ascertain whether F. -sanguinea could distinguish the pupæ of F. fusca, which they habitually make -into slaves, from those of the little and furious F. flava, which they rarely -capture, and it was evident that they did at once distinguish them: for we have -seen that they eagerly and instantly seized the pupæ of F. fusca, whereas they -were much terrified when they came across the pupæ, or even the earth from the -nest of F. flava, and quickly ran away; but in about a quarter of an hour, -shortly after all the little yellow ants had crawled away, they took heart and -carried off the pupæ. - -One evening I visited another community of F. sanguinea, and found a number of -these ants entering their nest, carrying the dead bodies of F. fusca (showing -that it was not a migration) and numerous pupæ. I traced the returning file -burthened with booty, for about forty yards, to a very thick clump of heath, -whence I saw the last individual of F. sanguinea emerge, carrying a pupa; but I -was not able to find the desolated nest in the thick heath. The nest, however, -must have been close at hand, for two or three individuals of F. fusca were -rushing about in the greatest agitation, and one was perched motionless with -its own pupa in its mouth on the top of a spray of heath over its ravaged home. - -Such are the facts, though they did not need confirmation by me, in regard to -the wonderful instinct of making slaves. Let it be observed what a contrast the -instinctive habits of F. sanguinea present with those of the F. rufescens. The -latter does not build its own nest, does not determine its own migrations, does -not collect food for itself or its young, and cannot even feed itself: it is -absolutely dependent on its numerous slaves. Formica sanguinea, on the other -hand, possesses much fewer slaves, and in the early part of the summer -extremely few. The masters determine when and where a new nest shall be formed, -and when they migrate, the masters carry the slaves. Both in Switzerland and +slave-making ant. This species is found in the southern parts of +England, and its habits have been attended to by Mr. F. Smith, of the +British Museum, to whom I am much indebted for information on this and +other subjects. Although fully trusting to the statements of Huber and +Mr. Smith, I tried to approach the subject in a sceptical frame of mind, +as any one may well be excused for doubting the truth of so +extraordinary and odious an instinct as that of making slaves. Hence I +will give the observations which I have myself made, in some little +detail. I opened fourteen nests of F. sanguinea, and found a few slaves +in all. Males and fertile females of the slave-species are found only in +their own proper communities, and have never been observed in the nests +of F. sanguinea. The slaves are black and not above half the size of +their red masters, so that the contrast in their appearance is very +great. When the nest is slightly disturbed, the slaves occasionally come +out, and like their masters are much agitated and defend the nest: when +the nest is much disturbed and the larvæ and pupæ are exposed, the +slaves work energetically with their masters in carrying them away to a +place of safety. Hence, it is clear, that the slaves feel quite at home. +During the months of June and July, on three successive years, I have +watched for many hours several nests in Surrey and Sussex, and never saw +a slave either leave or enter a nest. As, during these months, the +slaves are very few in number, I thought that they might behave +differently when more numerous; but Mr. Smith informs me that he has +watched the nests at various hours during May, June and August, both in +Surrey and Hampshire, and has never seen the slaves, though present in +large numbers in August, either leave or enter the nest. Hence he +considers them as strictly household slaves. The masters, on the other +hand, may be constantly seen bringing in materials for the nest, and +food of all kinds. During the present year, however, in the month of +July, I came across a community with an unusually large stock of slaves, +and I observed a few slaves mingled with their masters leaving the nest, +and marching along the same road to a tall Scotch-fir-tree, twenty-five +yards distant, which they ascended together, probably in search of +aphides or cocci. According to Huber, who had ample opportunities for +observation, in Switzerland the slaves habitually work with their +masters in making the nest, and they alone open and close the doors in +the morning and evening; and, as Huber expressly states, their principal +office is to search for aphides. This difference in the usual habits of +the masters and slaves in the two countries, probably depends merely on +the slaves being captured in greater numbers in Switzerland than in +England. + +One day I fortunately chanced to witness a migration from one nest to +another, and it was a most interesting spectacle to behold the masters +carefully carrying, as Huber has described, their slaves in their jaws. +Another day my attention was struck by about a score of the slave-makers +haunting the same spot, and evidently not in search of food; they +approached and were vigorously repulsed by an independent community of +the slave species (F. fusca); sometimes as many as three of these ants +clinging to the legs of the slave-making F. sanguinea. The latter +ruthlessly killed their small opponents, and carried their dead bodies +as food to their nest, twenty-nine yards distant; but they were +prevented from getting any pupæ to rear as slaves. I then dug up a small +parcel of the pupæ of F. fusca from another nest, and put them down on a +bare spot near the place of combat; they were eagerly seized, and +carried off by the tyrants, who perhaps fancied that, after all, they +had been victorious in their late combat. + +At the same time I laid on the same place a small parcel of the pupæ of +another species, F. flava, with a few of these little yellow ants still +clinging to the fragments of the nest. This species is sometimes, though +rarely, made into slaves, as has been described by Mr. Smith. Although +so small a species, it is very courageous, and I have seen it +ferociously attack other ants. In one instance I found to my surprise an +independent community of F. flava under a stone beneath a nest of the +slave-making F. sanguinea; and when I had accidentally disturbed both +nests, the little ants attacked their big neighbours with surprising +courage. Now I was curious to ascertain whether F. sanguinea could +distinguish the pupæ of F. fusca, which they habitually make into +slaves, from those of the little and furious F. flava, which they rarely +capture, and it was evident that they did at once distinguish them: for +we have seen that they eagerly and instantly seized the pupæ of F. +fusca, whereas they were much terrified when they came across the pupæ, +or even the earth from the nest of F. flava, and quickly ran away; but +in about a quarter of an hour, shortly after all the little yellow ants +had crawled away, they took heart and carried off the pupæ. + +One evening I visited another community of F. sanguinea, and found a +number of these ants entering their nest, carrying the dead bodies of F. +fusca (showing that it was not a migration) and numerous pupæ. I traced +the returning file burthened with booty, for about forty yards, to a +very thick clump of heath, whence I saw the last individual of F. +sanguinea emerge, carrying a pupa; but I was not able to find the +desolated nest in the thick heath. The nest, however, must have been +close at hand, for two or three individuals of F. fusca were rushing +about in the greatest agitation, and one was perched motionless with its +own pupa in its mouth on the top of a spray of heath over its ravaged +home. + +Such are the facts, though they did not need confirmation by me, in +regard to the wonderful instinct of making slaves. Let it be observed +what a contrast the instinctive habits of F. sanguinea present with +those of the F. rufescens. The latter does not build its own nest, does +not determine its own migrations, does not collect food for itself or +its young, and cannot even feed itself: it is absolutely dependent on +its numerous slaves. Formica sanguinea, on the other hand, possesses +much fewer slaves, and in the early part of the summer extremely few. +The masters determine when and where a new nest shall be formed, and +when they migrate, the masters carry the slaves. Both in Switzerland and England the slaves seem to have the exclusive care of the larvæ, and the -masters alone go on slave-making expeditions. In Switzerland the slaves and -masters work together, making and bringing materials for the nest: both, but -chiefly the slaves, tend, and milk as it may be called, their aphides; and thus -both collect food for the community. In England the masters alone usually leave -the nest to collect building materials and food for themselves, their slaves -and larvæ. So that the masters in this country receive much less service from -their slaves than they do in Switzerland. - -By what steps the instinct of F. sanguinea originated I will not pretend to -conjecture. But as ants, which are not slave-makers, will, as I have seen, -carry off pupæ of other species, if scattered near their nests, it is possible -that pupæ originally stored as food might become developed; and the ants thus -unintentionally reared would then follow their proper instincts, and do what -work they could. If their presence proved useful to the species which had -seized them—if it were more advantageous to this species to capture workers -than to procreate them—the habit of collecting pupæ originally for food might -by natural selection be strengthened and rendered permanent for the very -different purpose of raising slaves. When the instinct was once acquired, if -carried out to a much less extent even than in our British F. sanguinea, which, -as we have seen, is less aided by its slaves than the same species in +masters alone go on slave-making expeditions. In Switzerland the slaves +and masters work together, making and bringing materials for the nest: +both, but chiefly the slaves, tend, and milk as it may be called, their +aphides; and thus both collect food for the community. In England the +masters alone usually leave the nest to collect building materials and +food for themselves, their slaves and larvæ. So that the masters in this +country receive much less service from their slaves than they do in +Switzerland. + +By what steps the instinct of F. sanguinea originated I will not pretend +to conjecture. But as ants, which are not slave-makers, will, as I have +seen, carry off pupæ of other species, if scattered near their nests, it +is possible that pupæ originally stored as food might become developed; +and the ants thus unintentionally reared would then follow their proper +instincts, and do what work they could. If their presence proved useful +to the species which had seized them—if it were more advantageous to +this species to capture workers than to procreate them—the habit of +collecting pupæ originally for food might by natural selection be +strengthened and rendered permanent for the very different purpose of +raising slaves. When the instinct was once acquired, if carried out to a +much less extent even than in our British F. sanguinea, which, as we +have seen, is less aided by its slaves than the same species in Switzerland, I can see no difficulty in natural selection increasing and -modifying the instinct—always supposing each modification to be of use to the -species—until an ant was formed as abjectly dependent on its slaves as is the -Formica rufescens. - -Cell-making instinct of the Hive-Bee.—I will not here enter on minute details -on this subject, but will merely give an outline of the conclusions at which I -have arrived. He must be a dull man who can examine the exquisite structure of -a comb, so beautifully adapted to its end, without enthusiastic admiration. We -hear from mathematicians that bees have practically solved a recondite problem, -and have made their cells of the proper shape to hold the greatest possible -amount of honey, with the least possible consumption of precious wax in their -construction. It has been remarked that a skilful workman, with fitting tools -and measures, would find it very difficult to make cells of wax of the true -form, though this is perfectly effected by a crowd of bees working in a dark -hive. Grant whatever instincts you please, and it seems at first quite -inconceivable how they can make all the necessary angles and planes, or even -perceive when they are correctly made. But the difficulty is not nearly so -great as it at first appears: all this beautiful work can be shown, I think, to -follow from a few very simple instincts. - -I was led to investigate this subject by Mr. Waterhouse, who has shown that the -form of the cell stands in close relation to the presence of adjoining cells; -and the following view may, perhaps, be considered only as a modification of -his theory. Let us look to the great principle of gradation, and see whether -Nature does not reveal to us her method of work. At one end of a short series -we have humble-bees, which use their old cocoons to hold honey, sometimes -adding to them short tubes of wax, and likewise making separate and very -irregular rounded cells of wax. At the other end of the series we have the -cells of the hive-bee, placed in a double layer: each cell, as is well known, -is an hexagonal prism, with the basal edges of its six sides bevelled so as to -join on to a pyramid, formed of three rhombs. These rhombs have certain angles, -and the three which form the pyramidal base of a single cell on one side of the -comb, enter into the composition of the bases of three adjoining cells on the -opposite side. In the series between the extreme perfection of the cells of the -hive-bee and the simplicity of those of the humble-bee, we have the cells of -the Mexican Melipona domestica, carefully described and figured by Pierre -Huber. The Melipona itself is intermediate in structure between the hive and -humble bee, but more nearly related to the latter: it forms a nearly regular -waxen comb of cylindrical cells, in which the young are hatched, and, in -addition, some large cells of wax for holding honey. These latter cells are -nearly spherical and of nearly equal sizes, and are aggregated into an -irregular mass. But the important point to notice, is that these cells are -always made at that degree of nearness to each other, that they would have -intersected or broken into each other, if the spheres had been completed; but -this is never permitted, the bees building perfectly flat walls of wax between -the spheres which thus tend to intersect. Hence each cell consists of an outer -spherical portion and of two, three, or more perfectly flat surfaces, according -as the cell adjoins two, three or more other cells. When one cell comes into -contact with three other cells, which, from the spheres being nearly of the -same size, is very frequently and necessarily the case, the three flat surfaces -are united into a pyramid; and this pyramid, as Huber has remarked, is -manifestly a gross imitation of the three-sided pyramidal basis of the cell of -the hive-bee. As in the cells of the hive-bee, so here, the three plane -surfaces in any one cell necessarily enter into the construction of three -adjoining cells. It is obvious that the Melipona saves wax by this manner of -building; for the flat walls between the adjoining cells are not double, but -are of the same thickness as the outer spherical portions, and yet each flat +modifying the instinct—always supposing each modification to be of use +to the species—until an ant was formed as abjectly dependent on its +slaves as is the Formica rufescens. + +Cell-making instinct of the Hive-Bee.—I will not here enter on minute +details on this subject, but will merely give an outline of the +conclusions at which I have arrived. He must be a dull man who can +examine the exquisite structure of a comb, so beautifully adapted to its +end, without enthusiastic admiration. We hear from mathematicians that +bees have practically solved a recondite problem, and have made their +cells of the proper shape to hold the greatest possible amount of honey, +with the least possible consumption of precious wax in their +construction. It has been remarked that a skilful workman, with fitting +tools and measures, would find it very difficult to make cells of wax of +the true form, though this is perfectly effected by a crowd of bees +working in a dark hive. Grant whatever instincts you please, and it +seems at first quite inconceivable how they can make all the necessary +angles and planes, or even perceive when they are correctly made. But +the difficulty is not nearly so great as it at first appears: all this +beautiful work can be shown, I think, to follow from a few very simple +instincts. + +I was led to investigate this subject by Mr. Waterhouse, who has shown +that the form of the cell stands in close relation to the presence of +adjoining cells; and the following view may, perhaps, be considered only +as a modification of his theory. Let us look to the great principle of +gradation, and see whether Nature does not reveal to us her method of +work. At one end of a short series we have humble-bees, which use their +old cocoons to hold honey, sometimes adding to them short tubes of wax, +and likewise making separate and very irregular rounded cells of wax. At +the other end of the series we have the cells of the hive-bee, placed in +a double layer: each cell, as is well known, is an hexagonal prism, with +the basal edges of its six sides bevelled so as to join on to a pyramid, +formed of three rhombs. These rhombs have certain angles, and the three +which form the pyramidal base of a single cell on one side of the comb, +enter into the composition of the bases of three adjoining cells on the +opposite side. In the series between the extreme perfection of the cells +of the hive-bee and the simplicity of those of the humble-bee, we have +the cells of the Mexican Melipona domestica, carefully described and +figured by Pierre Huber. The Melipona itself is intermediate in +structure between the hive and humble bee, but more nearly related to +the latter: it forms a nearly regular waxen comb of cylindrical cells, +in which the young are hatched, and, in addition, some large cells of +wax for holding honey. These latter cells are nearly spherical and of +nearly equal sizes, and are aggregated into an irregular mass. But the +important point to notice, is that these cells are always made at that +degree of nearness to each other, that they would have intersected or +broken into each other, if the spheres had been completed; but this is +never permitted, the bees building perfectly flat walls of wax between +the spheres which thus tend to intersect. Hence each cell consists of an +outer spherical portion and of two, three, or more perfectly flat +surfaces, according as the cell adjoins two, three or more other cells. +When one cell comes into contact with three other cells, which, from the +spheres being nearly of the same size, is very frequently and +necessarily the case, the three flat surfaces are united into a pyramid; +and this pyramid, as Huber has remarked, is manifestly a gross imitation +of the three-sided pyramidal basis of the cell of the hive-bee. As in +the cells of the hive-bee, so here, the three plane surfaces in any one +cell necessarily enter into the construction of three adjoining cells. +It is obvious that the Melipona saves wax by this manner of building; +for the flat walls between the adjoining cells are not double, but are +of the same thickness as the outer spherical portions, and yet each flat portion forms a part of two cells. -Reflecting on this case, it occurred to me that if the Melipona had made its -spheres at some given distance from each other, and had made them of equal -sizes and had arranged them symmetrically in a double layer, the resulting -structure would probably have been as perfect as the comb of the hive-bee. -Accordingly I wrote to Professor Miller, of Cambridge, and this geometer has -kindly read over the following statement, drawn up from his information, and -tells me that it is strictly correct:— - -If a number of equal spheres be described with their centres placed in two -parallel layers; with the centre of each sphere at the distance of radius x the -square root of 2 or radius x 1.41421 (or at some lesser distance), from the -centres of the six surrounding spheres in the same layer; and at the same -distance from the centres of the adjoining spheres in the other and parallel -layer; then, if planes of intersection between the several spheres in both -layers be formed, there will result a double layer of hexagonal prisms united -together by pyramidal bases formed of three rhombs; and the rhombs and the -sides of the hexagonal prisms will have every angle identically the same with -the best measurements which have been made of the cells of the hive-bee. - -Hence we may safely conclude that if we could slightly modify the instincts -already possessed by the Melipona, and in themselves not very wonderful, this -bee would make a structure as wonderfully perfect as that of the hive-bee. We -must suppose the Melipona to make her cells truly spherical, and of equal -sizes; and this would not be very surprising, seeing that she already does so -to a certain extent, and seeing what perfectly cylindrical burrows in wood many -insects can make, apparently by turning round on a fixed point. We must suppose -the Melipona to arrange her cells in level layers, as she already does her +Reflecting on this case, it occurred to me that if the Melipona had made +its spheres at some given distance from each other, and had made them of +equal sizes and had arranged them symmetrically in a double layer, the +resulting structure would probably have been as perfect as the comb of +the hive-bee. Accordingly I wrote to Professor Miller, of Cambridge, +and this geometer has kindly read over the following statement, drawn up +from his information, and tells me that it is strictly correct:— + +If a number of equal spheres be described with their centres placed in +two parallel layers; with the centre of each sphere at the distance of +radius x the square root of 2 or radius x 1.41421 (or at some lesser +distance), from the centres of the six surrounding spheres in the same +layer; and at the same distance from the centres of the adjoining +spheres in the other and parallel layer; then, if planes of intersection +between the several spheres in both layers be formed, there will result +a double layer of hexagonal prisms united together by pyramidal bases +formed of three rhombs; and the rhombs and the sides of the hexagonal +prisms will have every angle identically the same with the best +measurements which have been made of the cells of the hive-bee. + +Hence we may safely conclude that if we could slightly modify the +instincts already possessed by the Melipona, and in themselves not very +wonderful, this bee would make a structure as wonderfully perfect as +that of the hive-bee. We must suppose the Melipona to make her cells +truly spherical, and of equal sizes; and this would not be very +surprising, seeing that she already does so to a certain extent, and +seeing what perfectly cylindrical burrows in wood many insects can make, +apparently by turning round on a fixed point. We must suppose the +Melipona to arrange her cells in level layers, as she already does her cylindrical cells; and we must further suppose, and this is the greatest -difficulty, that she can somehow judge accurately at what distance to stand -from her fellow-labourers when several are making their spheres; but she is -already so far enabled to judge of distance, that she always describes her -spheres so as to intersect largely; and then she unites the points of -intersection by perfectly flat surfaces. We have further to suppose, but this -is no difficulty, that after hexagonal prisms have been formed by the -intersection of adjoining spheres in the same layer, she can prolong the -hexagon to any length requisite to hold the stock of honey; in the same way as -the rude humble-bee adds cylinders of wax to the circular mouths of her old -cocoons. By such modifications of instincts in themselves not very -wonderful,—hardly more wonderful than those which guide a bird to make its -nest,—I believe that the hive-bee has acquired, through natural selection, her -inimitable architectural powers. - -But this theory can be tested by experiment. Following the example of Mr. -Tegetmeier, I separated two combs, and put between them a long, thick, square -strip of wax: the bees instantly began to excavate minute circular pits in it; -and as they deepened these little pits, they made them wider and wider until -they were converted into shallow basins, appearing to the eye perfectly true or -parts of a sphere, and of about the diameter of a cell. It was most interesting -to me to observe that wherever several bees had begun to excavate these basins -near together, they had begun their work at such a distance from each other, -that by the time the basins had acquired the above stated width (i.e. about the -width of an ordinary cell), and were in depth about one sixth of the diameter -of the sphere of which they formed a part, the rims of the basins intersected -or broke into each other. As soon as this occurred, the bees ceased to -excavate, and began to build up flat walls of wax on the lines of intersection -between the basins, so that each hexagonal prism was built upon the festooned -edge of a smooth basin, instead of on the straight edges of a three-sided -pyramid as in the case of ordinary cells. - -I then put into the hive, instead of a thick, square piece of wax, a thin and -narrow, knife-edged ridge, coloured with vermilion. The bees instantly began on -both sides to excavate little basins near to each other, in the same way as -before; but the ridge of wax was so thin, that the bottoms of the basins, if -they had been excavated to the same depth as in the former experiment, would -have broken into each other from the opposite sides. The bees, however, did not -suffer this to happen, and they stopped their excavations in due time; so that -the basins, as soon as they had been a little deepened, came to have flat -bottoms; and these flat bottoms, formed by thin little plates of the vermilion -wax having been left ungnawed, were situated, as far as the eye could judge, -exactly along the planes of imaginary intersection between the basins on the -opposite sides of the ridge of wax. In parts, only little bits, in other parts, -large portions of a rhombic plate had been left between the opposed basins, but -the work, from the unnatural state of things, had not been neatly performed. -The bees must have worked at very nearly the same rate on the opposite sides of -the ridge of vermilion wax, as they circularly gnawed away and deepened the -basins on both sides, in order to have succeeded in thus leaving flat plates -between the basins, by stopping work along the intermediate planes or planes of -intersection. - -Considering how flexible thin wax is, I do not see that there is any difficulty -in the bees, whilst at work on the two sides of a strip of wax, perceiving when -they have gnawed the wax away to the proper thinness, and then stopping their -work. In ordinary combs it has appeared to me that the bees do not always -succeed in working at exactly the same rate from the opposite sides; for I have -noticed half-completed rhombs at the base of a just-commenced cell, which were -slightly concave on one side, where I suppose that the bees had excavated too -quickly, and convex on the opposed side, where the bees had worked less -quickly. In one well-marked instance, I put the comb back into the hive, and -allowed the bees to go on working for a short time, and again examined the -cell, and I found that the rhombic plate had been completed, and had become -perfectly flat: it was absolutely impossible, from the extreme thinness of the -little rhombic plate, that they could have effected this by gnawing away the -convex side; and I suspect that the bees in such cases stand in the opposed -cells and push and bend the ductile and warm wax (which as I have tried is -easily done) into its proper intermediate plane, and thus flatten it. - -From the experiment of the ridge of vermilion wax, we can clearly see that if -the bees were to build for themselves a thin wall of wax, they could make their -cells of the proper shape, by standing at the proper distance from each other, -by excavating at the same rate, and by endeavouring to make equal spherical -hollows, but never allowing the spheres to break into each other. Now bees, as -may be clearly seen by examining the edge of a growing comb, do make a rough, -circumferential wall or rim all round the comb; and they gnaw into this from -the opposite sides, always working circularly as they deepen each cell. They do -not make the whole three-sided pyramidal base of any one cell at the same time, -but only the one rhombic plate which stands on the extreme growing margin, or -the two plates, as the case may be; and they never complete the upper edges of -the rhombic plates, until the hexagonal walls are commenced. Some of these -statements differ from those made by the justly celebrated elder Huber, but I -am convinced of their accuracy; and if I had space, I could show that they are -conformable with my theory. +difficulty, that she can somehow judge accurately at what distance to +stand from her fellow-labourers when several are making their spheres; +but she is already so far enabled to judge of distance, that she always +describes her spheres so as to intersect largely; and then she unites +the points of intersection by perfectly flat surfaces. We have further +to suppose, but this is no difficulty, that after hexagonal prisms have +been formed by the intersection of adjoining spheres in the same layer, +she can prolong the hexagon to any length requisite to hold the stock of +honey; in the same way as the rude humble-bee adds cylinders of wax to +the circular mouths of her old cocoons. By such modifications of +instincts in themselves not very wonderful,—hardly more wonderful than +those which guide a bird to make its nest,—I believe that the hive-bee +has acquired, through natural selection, her inimitable architectural +powers. + +But this theory can be tested by experiment. Following the example of +Mr. Tegetmeier, I separated two combs, and put between them a long, +thick, square strip of wax: the bees instantly began to excavate minute +circular pits in it; and as they deepened these little pits, they made +them wider and wider until they were converted into shallow basins, +appearing to the eye perfectly true or parts of a sphere, and of about +the diameter of a cell. It was most interesting to me to observe that +wherever several bees had begun to excavate these basins near together, +they had begun their work at such a distance from each other, that by +the time the basins had acquired the above stated width (i.e. about the +width of an ordinary cell), and were in depth about one sixth of the +diameter of the sphere of which they formed a part, the rims of the +basins intersected or broke into each other. As soon as this occurred, +the bees ceased to excavate, and began to build up flat walls of wax on +the lines of intersection between the basins, so that each hexagonal +prism was built upon the festooned edge of a smooth basin, instead of on +the straight edges of a three-sided pyramid as in the case of ordinary +cells. + +I then put into the hive, instead of a thick, square piece of wax, a +thin and narrow, knife-edged ridge, coloured with vermilion. The bees +instantly began on both sides to excavate little basins near to each +other, in the same way as before; but the ridge of wax was so thin, that +the bottoms of the basins, if they had been excavated to the same depth +as in the former experiment, would have broken into each other from the +opposite sides. The bees, however, did not suffer this to happen, and +they stopped their excavations in due time; so that the basins, as soon +as they had been a little deepened, came to have flat bottoms; and these +flat bottoms, formed by thin little plates of the vermilion wax having +been left ungnawed, were situated, as far as the eye could judge, +exactly along the planes of imaginary intersection between the basins on +the opposite sides of the ridge of wax. In parts, only little bits, in +other parts, large portions of a rhombic plate had been left between the +opposed basins, but the work, from the unnatural state of things, had +not been neatly performed. The bees must have worked at very nearly the +same rate on the opposite sides of the ridge of vermilion wax, as they +circularly gnawed away and deepened the basins on both sides, in order +to have succeeded in thus leaving flat plates between the basins, by +stopping work along the intermediate planes or planes of intersection. + +Considering how flexible thin wax is, I do not see that there is any +difficulty in the bees, whilst at work on the two sides of a strip of +wax, perceiving when they have gnawed the wax away to the proper +thinness, and then stopping their work. In ordinary combs it has +appeared to me that the bees do not always succeed in working at exactly +the same rate from the opposite sides; for I have noticed half-completed +rhombs at the base of a just-commenced cell, which were slightly concave +on one side, where I suppose that the bees had excavated too quickly, +and convex on the opposed side, where the bees had worked less quickly. +In one well-marked instance, I put the comb back into the hive, and +allowed the bees to go on working for a short time, and again examined +the cell, and I found that the rhombic plate had been completed, and had +become perfectly flat: it was absolutely impossible, from the extreme +thinness of the little rhombic plate, that they could have effected this +by gnawing away the convex side; and I suspect that the bees in such +cases stand in the opposed cells and push and bend the ductile and warm +wax (which as I have tried is easily done) into its proper intermediate +plane, and thus flatten it. + +From the experiment of the ridge of vermilion wax, we can clearly see +that if the bees were to build for themselves a thin wall of wax, they +could make their cells of the proper shape, by standing at the proper +distance from each other, by excavating at the same rate, and by +endeavouring to make equal spherical hollows, but never allowing the +spheres to break into each other. Now bees, as may be clearly seen by +examining the edge of a growing comb, do make a rough, circumferential +wall or rim all round the comb; and they gnaw into this from the +opposite sides, always working circularly as they deepen each cell. They +do not make the whole three-sided pyramidal base of any one cell at the +same time, but only the one rhombic plate which stands on the extreme +growing margin, or the two plates, as the case may be; and they never +complete the upper edges of the rhombic plates, until the hexagonal +walls are commenced. Some of these statements differ from those made by +the justly celebrated elder Huber, but I am convinced of their accuracy; +and if I had space, I could show that they are conformable with my +theory. Huber’s statement that the very first cell is excavated out of a little -parallel-sided wall of wax, is not, as far as I have seen, strictly correct; -the first commencement having always been a little hood of wax; but I will not -here enter on these details. We see how important a part excavation plays in -the construction of the cells; but it would be a great error to suppose that -the bees cannot build up a rough wall of wax in the proper position—that is, -along the plane of intersection between two adjoining spheres. I have several -specimens showing clearly that they can do this. Even in the rude -circumferential rim or wall of wax round a growing comb, flexures may sometimes -be observed, corresponding in position to the planes of the rhombic basal -plates of future cells. But the rough wall of wax has in every case to be -finished off, by being largely gnawed away on both sides. The manner in which -the bees build is curious; they always make the first rough wall from ten to -twenty times thicker than the excessively thin finished wall of the cell, which -will ultimately be left. We shall understand how they work, by supposing masons -first to pile up a broad ridge of cement, and then to begin cutting it away -equally on both sides near the ground, till a smooth, very thin wall is left in -the middle; the masons always piling up the cut-away cement, and adding fresh -cement, on the summit of the ridge. We shall thus have a thin wall steadily -growing upward; but always crowned by a gigantic coping. From all the cells, -both those just commenced and those completed, being thus crowned by a strong -coping of wax, the bees can cluster and crawl over the comb without injuring -the delicate hexagonal walls, which are only about one four-hundredth of an -inch in thickness; the plates of the pyramidal basis being about twice as -thick. By this singular manner of building, strength is continually given to +parallel-sided wall of wax, is not, as far as I have seen, strictly +correct; the first commencement having always been a little hood of wax; +but I will not here enter on these details. We see how important a part +excavation plays in the construction of the cells; but it would be a +great error to suppose that the bees cannot build up a rough wall of wax +in the proper position—that is, along the plane of intersection between +two adjoining spheres. I have several specimens showing clearly that +they can do this. Even in the rude circumferential rim or wall of wax +round a growing comb, flexures may sometimes be observed, corresponding +in position to the planes of the rhombic basal plates of future cells. +But the rough wall of wax has in every case to be finished off, by being +largely gnawed away on both sides. The manner in which the bees build is +curious; they always make the first rough wall from ten to twenty times +thicker than the excessively thin finished wall of the cell, which will +ultimately be left. We shall understand how they work, by supposing +masons first to pile up a broad ridge of cement, and then to begin +cutting it away equally on both sides near the ground, till a smooth, +very thin wall is left in the middle; the masons always piling up the +cut-away cement, and adding fresh cement, on the summit of the ridge. We +shall thus have a thin wall steadily growing upward; but always crowned +by a gigantic coping. From all the cells, both those just commenced and +those completed, being thus crowned by a strong coping of wax, the bees +can cluster and crawl over the comb without injuring the delicate +hexagonal walls, which are only about one four-hundredth of an inch in +thickness; the plates of the pyramidal basis being about twice as thick. +By this singular manner of building, strength is continually given to the comb, with the utmost ultimate economy of wax. -It seems at first to add to the difficulty of understanding how the cells are -made, that a multitude of bees all work together; one bee after working a short -time at one cell going to another, so that, as Huber has stated, a score of -individuals work even at the commencement of the first cell. I was able -practically to show this fact, by covering the edges of the hexagonal walls of -a single cell, or the extreme margin of the circumferential rim of a growing -comb, with an extremely thin layer of melted vermilion wax; and I invariably -found that the colour was most delicately diffused by the bees—as delicately as -a painter could have done with his brush—by atoms of the coloured wax having -been taken from the spot on which it had been placed, and worked into the -growing edges of the cells all round. The work of construction seems to be a -sort of balance struck between many bees, all instinctively standing at the -same relative distance from each other, all trying to sweep equal spheres, and -then building up, or leaving ungnawed, the planes of intersection between these -spheres. It was really curious to note in cases of difficulty, as when two -pieces of comb met at an angle, how often the bees would entirely pull down and -rebuild in different ways the same cell, sometimes recurring to a shape which -they had at first rejected. - -When bees have a place on which they can stand in their proper positions for -working,—for instance, on a slip of wood, placed directly under the middle of a -comb growing downwards so that the comb has to be built over one face of the -slip—in this case the bees can lay the foundations of one wall of a new -hexagon, in its strictly proper place, projecting beyond the other completed -cells. It suffices that the bees should be enabled to stand at their proper -relative distances from each other and from the walls of the last completed -cells, and then, by striking imaginary spheres, they can build up a wall -intermediate between two adjoining spheres; but, as far as I have seen, they -never gnaw away and finish off the angles of a cell till a large part both of -that cell and of the adjoining cells has been built. This capacity in bees of -laying down under certain circumstances a rough wall in its proper place -between two just-commenced cells, is important, as it bears on a fact, which -seems at first quite subversive of the foregoing theory; namely, that the cells -on the extreme margin of wasp-combs are sometimes strictly hexagonal; but I -have not space here to enter on this subject. Nor does there seem to me any -great difficulty in a single insect (as in the case of a queen-wasp) making -hexagonal cells, if she work alternately on the inside and outside of two or -three cells commenced at the same time, always standing at the proper relative -distance from the parts of the cells just begun, sweeping spheres or cylinders, -and building up intermediate planes. It is even conceivable that an insect +It seems at first to add to the difficulty of understanding how the +cells are made, that a multitude of bees all work together; one bee +after working a short time at one cell going to another, so that, as +Huber has stated, a score of individuals work even at the commencement +of the first cell. I was able practically to show this fact, by covering +the edges of the hexagonal walls of a single cell, or the extreme margin +of the circumferential rim of a growing comb, with an extremely thin +layer of melted vermilion wax; and I invariably found that the colour +was most delicately diffused by the bees—as delicately as a painter +could have done with his brush—by atoms of the coloured wax having been +taken from the spot on which it had been placed, and worked into the +growing edges of the cells all round. The work of construction seems to +be a sort of balance struck between many bees, all instinctively +standing at the same relative distance from each other, all trying to +sweep equal spheres, and then building up, or leaving ungnawed, the +planes of intersection between these spheres. It was really curious to +note in cases of difficulty, as when two pieces of comb met at an angle, +how often the bees would entirely pull down and rebuild in different +ways the same cell, sometimes recurring to a shape which they had at +first rejected. + +When bees have a place on which they can stand in their proper positions +for working,—for instance, on a slip of wood, placed directly under the +middle of a comb growing downwards so that the comb has to be built over +one face of the slip—in this case the bees can lay the foundations of +one wall of a new hexagon, in its strictly proper place, projecting +beyond the other completed cells. It suffices that the bees should be +enabled to stand at their proper relative distances from each other and +from the walls of the last completed cells, and then, by striking +imaginary spheres, they can build up a wall intermediate between two +adjoining spheres; but, as far as I have seen, they never gnaw away and +finish off the angles of a cell till a large part both of that cell and +of the adjoining cells has been built. This capacity in bees of laying +down under certain circumstances a rough wall in its proper place +between two just-commenced cells, is important, as it bears on a fact, +which seems at first quite subversive of the foregoing theory; namely, +that the cells on the extreme margin of wasp-combs are sometimes +strictly hexagonal; but I have not space here to enter on this subject. +Nor does there seem to me any great difficulty in a single insect (as in +the case of a queen-wasp) making hexagonal cells, if she work +alternately on the inside and outside of two or three cells commenced at +the same time, always standing at the proper relative distance from the +parts of the cells just begun, sweeping spheres or cylinders, and +building up intermediate planes. It is even conceivable that an insect might, by fixing on a point at which to commence a cell, and then moving -outside, first to one point, and then to five other points, at the proper -relative distances from the central point and from each other, strike the -planes of intersection, and so make an isolated hexagon: but I am not aware -that any such case has been observed; nor would any good be derived from a -single hexagon being built, as in its construction more materials would be -required than for a cylinder. - -As natural selection acts only by the accumulation of slight modifications of -structure or instinct, each profitable to the individual under its conditions -of life, it may reasonably be asked, how a long and graduated succession of -modified architectural instincts, all tending towards the present perfect plan -of construction, could have profited the progenitors of the hive-bee? I think -the answer is not difficult: it is known that bees are often hard pressed to -get sufficient nectar; and I am informed by Mr. Tegetmeier that it has been -experimentally found that no less than from twelve to fifteen pounds of dry -sugar are consumed by a hive of bees for the secretion of each pound of wax; so -that a prodigious quantity of fluid nectar must be collected and consumed by -the bees in a hive for the secretion of the wax necessary for the construction -of their combs. Moreover, many bees have to remain idle for many days during -the process of secretion. A large store of honey is indispensable to support a -large stock of bees during the winter; and the security of the hive is known -mainly to depend on a large number of bees being supported. Hence the saving of -wax by largely saving honey must be a most important element of success in any -family of bees. Of course the success of any species of bee may be dependent on -the number of its parasites or other enemies, or on quite distinct causes, and -so be altogether independent of the quantity of honey which the bees could -collect. But let us suppose that this latter circumstance determined, as it -probably often does determine, the numbers of a humble-bee which could exist in -a country; and let us further suppose that the community lived throughout the -winter, and consequently required a store of honey: there can in this case be -no doubt that it would be an advantage to our humble-bee, if a slight -modification of her instinct led her to make her waxen cells near together, so -as to intersect a little; for a wall in common even to two adjoining cells, +outside, first to one point, and then to five other points, at the +proper relative distances from the central point and from each other, +strike the planes of intersection, and so make an isolated hexagon: but +I am not aware that any such case has been observed; nor would any good +be derived from a single hexagon being built, as in its construction +more materials would be required than for a cylinder. + +As natural selection acts only by the accumulation of slight +modifications of structure or instinct, each profitable to the +individual under its conditions of life, it may reasonably be asked, how +a long and graduated succession of modified architectural instincts, all +tending towards the present perfect plan of construction, could have +profited the progenitors of the hive-bee? I think the answer is not +difficult: it is known that bees are often hard pressed to get +sufficient nectar; and I am informed by Mr. Tegetmeier that it has been +experimentally found that no less than from twelve to fifteen pounds of +dry sugar are consumed by a hive of bees for the secretion of each pound +of wax; so that a prodigious quantity of fluid nectar must be collected +and consumed by the bees in a hive for the secretion of the wax +necessary for the construction of their combs. Moreover, many bees have +to remain idle for many days during the process of secretion. A large +store of honey is indispensable to support a large stock of bees during +the winter; and the security of the hive is known mainly to depend on a +large number of bees being supported. Hence the saving of wax by largely +saving honey must be a most important element of success in any family +of bees. Of course the success of any species of bee may be dependent on +the number of its parasites or other enemies, or on quite distinct +causes, and so be altogether independent of the quantity of honey which +the bees could collect. But let us suppose that this latter circumstance +determined, as it probably often does determine, the numbers of a +humble-bee which could exist in a country; and let us further suppose +that the community lived throughout the winter, and consequently +required a store of honey: there can in this case be no doubt that it +would be an advantage to our humble-bee, if a slight modification of her +instinct led her to make her waxen cells near together, so as to +intersect a little; for a wall in common even to two adjoining cells, would save some little wax. Hence it would continually be more and more -advantageous to our humble-bee, if she were to make her cells more and more -regular, nearer together, and aggregated into a mass, like the cells of the -Melipona; for in this case a large part of the bounding surface of each cell -would serve to bound other cells, and much wax would be saved. Again, from the -same cause, it would be advantageous to the Melipona, if she were to make her -cells closer together, and more regular in every way than at present; for then, -as we have seen, the spherical surfaces would wholly disappear, and would all -be replaced by plane surfaces; and the Melipona would make a comb as perfect as -that of the hive-bee. Beyond this stage of perfection in architecture, natural -selection could not lead; for the comb of the hive-bee, as far as we can see, -is absolutely perfect in economising wax. - -Thus, as I believe, the most wonderful of all known instincts, that of the -hive-bee, can be explained by natural selection having taken advantage of -numerous, successive, slight modifications of simpler instincts; natural -selection having by slow degrees, more and more perfectly, led the bees to -sweep equal spheres at a given distance from each other in a double layer, and -to build up and excavate the wax along the planes of intersection. The bees, of -course, no more knowing that they swept their spheres at one particular -distance from each other, than they know what are the several angles of the -hexagonal prisms and of the basal rhombic plates. The motive power of the -process of natural selection having been economy of wax; that individual swarm -which wasted least honey in the secretion of wax, having succeeded best, and -having transmitted by inheritance its newly acquired economical instinct to new -swarms, which in their turn will have had the best chance of succeeding in the -struggle for existence. - -No doubt many instincts of very difficult explanation could be opposed to the -theory of natural selection,—cases, in which we cannot see how an instinct -could possibly have originated; cases, in which no intermediate gradations are -known to exist; cases of instinct of apparently such trifling importance, that -they could hardly have been acted on by natural selection; cases of instincts -almost identically the same in animals so remote in the scale of nature, that -we cannot account for their similarity by inheritance from a common parent, and -must therefore believe that they have been acquired by independent acts of -natural selection. I will not here enter on these several cases, but will +advantageous to our humble-bee, if she were to make her cells more and +more regular, nearer together, and aggregated into a mass, like the +cells of the Melipona; for in this case a large part of the bounding +surface of each cell would serve to bound other cells, and much wax +would be saved. Again, from the same cause, it would be advantageous to +the Melipona, if she were to make her cells closer together, and more +regular in every way than at present; for then, as we have seen, the +spherical surfaces would wholly disappear, and would all be replaced by +plane surfaces; and the Melipona would make a comb as perfect as that of +the hive-bee. Beyond this stage of perfection in architecture, natural +selection could not lead; for the comb of the hive-bee, as far as we can +see, is absolutely perfect in economising wax. + +Thus, as I believe, the most wonderful of all known instincts, that of +the hive-bee, can be explained by natural selection having taken +advantage of numerous, successive, slight modifications of simpler +instincts; natural selection having by slow degrees, more and more +perfectly, led the bees to sweep equal spheres at a given distance from +each other in a double layer, and to build up and excavate the wax along +the planes of intersection. The bees, of course, no more knowing that +they swept their spheres at one particular distance from each other, +than they know what are the several angles of the hexagonal prisms and +of the basal rhombic plates. The motive power of the process of natural +selection having been economy of wax; that individual swarm which wasted +least honey in the secretion of wax, having succeeded best, and having +transmitted by inheritance its newly acquired economical instinct to new +swarms, which in their turn will have had the best chance of succeeding +in the struggle for existence. + +No doubt many instincts of very difficult explanation could be opposed +to the theory of natural selection,—cases, in which we cannot see how an +instinct could possibly have originated; cases, in which no intermediate +gradations are known to exist; cases of instinct of apparently such +trifling importance, that they could hardly have been acted on by +natural selection; cases of instincts almost identically the same in +animals so remote in the scale of nature, that we cannot account for +their similarity by inheritance from a common parent, and must therefore +believe that they have been acquired by independent acts of natural +selection. I will not here enter on these several cases, but will confine myself to one special difficulty, which at first appeared to me -insuperable, and actually fatal to my whole theory. I allude to the neuters or -sterile females in insect-communities: for these neuters often differ widely in -instinct and in structure from both the males and fertile females, and yet, -from being sterile, they cannot propagate their kind. - -The subject well deserves to be discussed at great length, but I will here take -only a single case, that of working or sterile ants. How the workers have been -rendered sterile is a difficulty; but not much greater than that of any other -striking modification of structure; for it can be shown that some insects and -other articulate animals in a state of nature occasionally become sterile; and -if such insects had been social, and it had been profitable to the community -that a number should have been annually born capable of work, but incapable of -procreation, I can see no very great difficulty in this being effected by -natural selection. But I must pass over this preliminary difficulty. The great -difficulty lies in the working ants differing widely from both the males and -the fertile females in structure, as in the shape of the thorax and in being -destitute of wings and sometimes of eyes, and in instinct. As far as instinct -alone is concerned, the prodigious difference in this respect between the -workers and the perfect females, would have been far better exemplified by the -hive-bee. If a working ant or other neuter insect had been an animal in the -ordinary state, I should have unhesitatingly assumed that all its characters -had been slowly acquired through natural selection; namely, by an individual -having been born with some slight profitable modification of structure, this -being inherited by its offspring, which again varied and were again selected, -and so onwards. But with the working ant we have an insect differing greatly -from its parents, yet absolutely sterile; so that it could never have -transmitted successively acquired modifications of structure or instinct to its -progeny. It may well be asked how is it possible to reconcile this case with -the theory of natural selection? - -First, let it be remembered that we have innumerable instances, both in our -domestic productions and in those in a state of nature, of all sorts of -differences of structure which have become correlated to certain ages, and to -either sex. We have differences correlated not only to one sex, but to that -short period alone when the reproductive system is active, as in the nuptial -plumage of many birds, and in the hooked jaws of the male salmon. We have even -slight differences in the horns of different breeds of cattle in relation to an -artificially imperfect state of the male sex; for oxen of certain breeds have -longer horns than in other breeds, in comparison with the horns of the bulls or -cows of these same breeds. Hence I can see no real difficulty in any character -having become correlated with the sterile condition of certain members of -insect-communities: the difficulty lies in understanding how such correlated -modifications of structure could have been slowly accumulated by natural -selection. - -This difficulty, though appearing insuperable, is lessened, or, as I believe, -disappears, when it is remembered that selection may be applied to the family, -as well as to the individual, and may thus gain the desired end. Thus, a -well-flavoured vegetable is cooked, and the individual is destroyed; but the -horticulturist sows seeds of the same stock, and confidently expects to get -nearly the same variety; breeders of cattle wish the flesh and fat to be well -marbled together; the animal has been slaughtered, but the breeder goes with -confidence to the same family. I have such faith in the powers of selection, -that I do not doubt that a breed of cattle, always yielding oxen with -extraordinarily long horns, could be slowly formed by carefully watching which -individual bulls and cows, when matched, produced oxen with the longest horns; -and yet no one ox could ever have propagated its kind. Thus I believe it has -been with social insects: a slight modification of structure, or instinct, -correlated with the sterile condition of certain members of the community, has -been advantageous to the community: consequently the fertile males and females -of the same community flourished, and transmitted to their fertile offspring a -tendency to produce sterile members having the same modification. And I believe -that this process has been repeated, until that prodigious amount of difference -between the fertile and sterile females of the same species has been produced, -which we see in many social insects. - -But we have not as yet touched on the climax of the difficulty; namely, the -fact that the neuters of several ants differ, not only from the fertile females -and males, but from each other, sometimes to an almost incredible degree, and -are thus divided into two or even three castes. The castes, moreover, do not -generally graduate into each other, but are perfectly well defined; being as -distinct from each other, as are any two species of the same genus, or rather -as any two genera of the same family. Thus in Eciton, there are working and -soldier neuters, with jaws and instincts extraordinarily different: in -Cryptocerus, the workers of one caste alone carry a wonderful sort of shield on -their heads, the use of which is quite unknown: in the Mexican Myrmecocystus, -the workers of one caste never leave the nest; they are fed by the workers of -another caste, and they have an enormously developed abdomen which secretes a -sort of honey, supplying the place of that excreted by the aphides, or the -domestic cattle as they may be called, which our European ants guard or -imprison. +insuperable, and actually fatal to my whole theory. I allude to the +neuters or sterile females in insect-communities: for these neuters +often differ widely in instinct and in structure from both the males and +fertile females, and yet, from being sterile, they cannot propagate +their kind. + +The subject well deserves to be discussed at great length, but I will +here take only a single case, that of working or sterile ants. How the +workers have been rendered sterile is a difficulty; but not much greater +than that of any other striking modification of structure; for it can be +shown that some insects and other articulate animals in a state of +nature occasionally become sterile; and if such insects had been social, +and it had been profitable to the community that a number should have +been annually born capable of work, but incapable of procreation, I can +see no very great difficulty in this being effected by natural +selection. But I must pass over this preliminary difficulty. The great +difficulty lies in the working ants differing widely from both the males +and the fertile females in structure, as in the shape of the thorax and +in being destitute of wings and sometimes of eyes, and in instinct. As +far as instinct alone is concerned, the prodigious difference in this +respect between the workers and the perfect females, would have been far +better exemplified by the hive-bee. If a working ant or other neuter +insect had been an animal in the ordinary state, I should have +unhesitatingly assumed that all its characters had been slowly acquired +through natural selection; namely, by an individual having been born +with some slight profitable modification of structure, this being +inherited by its offspring, which again varied and were again selected, +and so onwards. But with the working ant we have an insect differing +greatly from its parents, yet absolutely sterile; so that it could never +have transmitted successively acquired modifications of structure or +instinct to its progeny. It may well be asked how is it possible to +reconcile this case with the theory of natural selection? + +First, let it be remembered that we have innumerable instances, both in +our domestic productions and in those in a state of nature, of all sorts +of differences of structure which have become correlated to certain +ages, and to either sex. We have differences correlated not only to one +sex, but to that short period alone when the reproductive system is +active, as in the nuptial plumage of many birds, and in the hooked jaws +of the male salmon. We have even slight differences in the horns of +different breeds of cattle in relation to an artificially imperfect +state of the male sex; for oxen of certain breeds have longer horns than +in other breeds, in comparison with the horns of the bulls or cows of +these same breeds. Hence I can see no real difficulty in any character +having become correlated with the sterile condition of certain members +of insect-communities: the difficulty lies in understanding how such +correlated modifications of structure could have been slowly accumulated +by natural selection. + +This difficulty, though appearing insuperable, is lessened, or, as I +believe, disappears, when it is remembered that selection may be applied +to the family, as well as to the individual, and may thus gain the +desired end. Thus, a well-flavoured vegetable is cooked, and the +individual is destroyed; but the horticulturist sows seeds of the same +stock, and confidently expects to get nearly the same variety; breeders +of cattle wish the flesh and fat to be well marbled together; the animal +has been slaughtered, but the breeder goes with confidence to the same +family. I have such faith in the powers of selection, that I do not +doubt that a breed of cattle, always yielding oxen with extraordinarily +long horns, could be slowly formed by carefully watching which +individual bulls and cows, when matched, produced oxen with the longest +horns; and yet no one ox could ever have propagated its kind. Thus I +believe it has been with social insects: a slight modification of +structure, or instinct, correlated with the sterile condition of certain +members of the community, has been advantageous to the community: +consequently the fertile males and females of the same community +flourished, and transmitted to their fertile offspring a tendency to +produce sterile members having the same modification. And I believe that +this process has been repeated, until that prodigious amount of +difference between the fertile and sterile females of the same species +has been produced, which we see in many social insects. + +But we have not as yet touched on the climax of the difficulty; namely, +the fact that the neuters of several ants differ, not only from the +fertile females and males, but from each other, sometimes to an almost +incredible degree, and are thus divided into two or even three castes. +The castes, moreover, do not generally graduate into each other, but are +perfectly well defined; being as distinct from each other, as are any +two species of the same genus, or rather as any two genera of the same +family. Thus in Eciton, there are working and soldier neuters, with jaws +and instincts extraordinarily different: in Cryptocerus, the workers of +one caste alone carry a wonderful sort of shield on their heads, the use +of which is quite unknown: in the Mexican Myrmecocystus, the workers of +one caste never leave the nest; they are fed by the workers of another +caste, and they have an enormously developed abdomen which secretes a +sort of honey, supplying the place of that excreted by the aphides, or +the domestic cattle as they may be called, which our European ants guard +or imprison. It will indeed be thought that I have an overweening confidence in the -principle of natural selection, when I do not admit that such wonderful and -well-established facts at once annihilate my theory. In the simpler case of -neuter insects all of one caste or of the same kind, which have been rendered -by natural selection, as I believe to be quite possible, different from the -fertile males and females,—in this case, we may safely conclude from the -analogy of ordinary variations, that each successive, slight, profitable -modification did not probably at first appear in all the individual neuters in -the same nest, but in a few alone; and that by the long-continued selection of -the fertile parents which produced most neuters with the profitable -modification, all the neuters ultimately came to have the desired character. On -this view we ought occasionally to find neuter-insects of the same species, in -the same nest, presenting gradations of structure; and this we do find, even -often, considering how few neuter-insects out of Europe have been carefully -examined. Mr. F. Smith has shown how surprisingly the neuters of several -British ants differ from each other in size and sometimes in colour; and that -the extreme forms can sometimes be perfectly linked together by individuals -taken out of the same nest: I have myself compared perfect gradations of this -kind. It often happens that the larger or the smaller sized workers are the -most numerous; or that both large and small are numerous, with those of an -intermediate size scanty in numbers. Formica flava has larger and smaller -workers, with some of intermediate size; and, in this species, as Mr. F. Smith -has observed, the larger workers have simple eyes (ocelli), which though small -can be plainly distinguished, whereas the smaller workers have their ocelli -rudimentary. Having carefully dissected several specimens of these workers, I -can affirm that the eyes are far more rudimentary in the smaller workers than -can be accounted for merely by their proportionally lesser size; and I fully -believe, though I dare not assert so positively, that the workers of -intermediate size have their ocelli in an exactly intermediate condition. So -that we here have two bodies of sterile workers in the same nest, differing not -only in size, but in their organs of vision, yet connected by some few members -in an intermediate condition. I may digress by adding, that if the smaller -workers had been the most useful to the community, and those males and females -had been continually selected, which produced more and more of the smaller -workers, until all the workers had come to be in this condition; we should then -have had a species of ant with neuters very nearly in the same condition with -those of Myrmica. For the workers of Myrmica have not even rudiments of ocelli, -though the male and female ants of this genus have well-developed ocelli. - -I may give one other case: so confidently did I expect to find gradations in -important points of structure between the different castes of neuters in the -same species, that I gladly availed myself of Mr. F. Smith’s offer of numerous -specimens from the same nest of the driver ant (Anomma) of West Africa. The -reader will perhaps best appreciate the amount of difference in these workers, -by my giving not the actual measurements, but a strictly accurate illustration: -the difference was the same as if we were to see a set of workmen building a -house of whom many were five feet four inches high, and many sixteen feet high; -but we must suppose that the larger workmen had heads four instead of three -times as big as those of the smaller men, and jaws nearly five times as big. -The jaws, moreover, of the working ants of the several sizes differed -wonderfully in shape, and in the form and number of the teeth. But the -important fact for us is, that though the workers can be grouped into castes of -different sizes, yet they graduate insensibly into each other, as does the -widely-different structure of their jaws. I speak confidently on this latter -point, as Mr. Lubbock made drawings for me with the camera lucida of the jaws -which I had dissected from the workers of the several sizes. - -With these facts before me, I believe that natural selection, by acting on the -fertile parents, could form a species which should regularly produce neuters, -either all of large size with one form of jaw, or all of small size with jaws -having a widely different structure; or lastly, and this is our climax of -difficulty, one set of workers of one size and structure, and simultaneously -another set of workers of a different size and structure;—a graduated series -having been first formed, as in the case of the driver ant, and then the -extreme forms, from being the most useful to the community, having been -produced in greater and greater numbers through the natural selection of the -parents which generated them; until none with an intermediate structure were -produced. - -Thus, as I believe, the wonderful fact of two distinctly defined castes of -sterile workers existing in the same nest, both widely different from each -other and from their parents, has originated. We can see how useful their -production may have been to a social community of insects, on the same -principle that the division of labour is useful to civilised man. As ants work -by inherited instincts and by inherited tools or weapons, and not by acquired -knowledge and manufactured instruments, a perfect division of labour could be -effected with them only by the workers being sterile; for had they been -fertile, they would have intercrossed, and their instincts and structure would -have become blended. And nature has, as I believe, effected this admirable -division of labour in the communities of ants, by the means of natural -selection. But I am bound to confess, that, with all my faith in this -principle, I should never have anticipated that natural selection could have -been efficient in so high a degree, had not the case of these neuter insects -convinced me of the fact. I have, therefore, discussed this case, at some -little but wholly insufficient length, in order to show the power of natural +principle of natural selection, when I do not admit that such wonderful +and well-established facts at once annihilate my theory. In the simpler +case of neuter insects all of one caste or of the same kind, which have +been rendered by natural selection, as I believe to be quite possible, +different from the fertile males and females,—in this case, we may +safely conclude from the analogy of ordinary variations, that each +successive, slight, profitable modification did not probably at first +appear in all the individual neuters in the same nest, but in a few +alone; and that by the long-continued selection of the fertile parents +which produced most neuters with the profitable modification, all the +neuters ultimately came to have the desired character. On this view we +ought occasionally to find neuter-insects of the same species, in the +same nest, presenting gradations of structure; and this we do find, even +often, considering how few neuter-insects out of Europe have been +carefully examined. Mr. F. Smith has shown how surprisingly the neuters +of several British ants differ from each other in size and sometimes in +colour; and that the extreme forms can sometimes be perfectly linked +together by individuals taken out of the same nest: I have myself +compared perfect gradations of this kind. It often happens that the +larger or the smaller sized workers are the most numerous; or that both +large and small are numerous, with those of an intermediate size scanty +in numbers. Formica flava has larger and smaller workers, with some of +intermediate size; and, in this species, as Mr. F. Smith has observed, +the larger workers have simple eyes (ocelli), which though small can be +plainly distinguished, whereas the smaller workers have their ocelli +rudimentary. Having carefully dissected several specimens of these +workers, I can affirm that the eyes are far more rudimentary in the +smaller workers than can be accounted for merely by their proportionally +lesser size; and I fully believe, though I dare not assert so +positively, that the workers of intermediate size have their ocelli in +an exactly intermediate condition. So that we here have two bodies of +sterile workers in the same nest, differing not only in size, but in +their organs of vision, yet connected by some few members in an +intermediate condition. I may digress by adding, that if the smaller +workers had been the most useful to the community, and those males and +females had been continually selected, which produced more and more of +the smaller workers, until all the workers had come to be in this +condition; we should then have had a species of ant with neuters very +nearly in the same condition with those of Myrmica. For the workers of +Myrmica have not even rudiments of ocelli, though the male and female +ants of this genus have well-developed ocelli. + +I may give one other case: so confidently did I expect to find +gradations in important points of structure between the different castes +of neuters in the same species, that I gladly availed myself of Mr. F. +Smith’s offer of numerous specimens from the same nest of the driver ant +(Anomma) of West Africa. The reader will perhaps best appreciate the +amount of difference in these workers, by my giving not the actual +measurements, but a strictly accurate illustration: the difference was +the same as if we were to see a set of workmen building a house of whom +many were five feet four inches high, and many sixteen feet high; but we +must suppose that the larger workmen had heads four instead of three +times as big as those of the smaller men, and jaws nearly five times as +big. The jaws, moreover, of the working ants of the several sizes +differed wonderfully in shape, and in the form and number of the teeth. +But the important fact for us is, that though the workers can be grouped +into castes of different sizes, yet they graduate insensibly into each +other, as does the widely-different structure of their jaws. I speak +confidently on this latter point, as Mr. Lubbock made drawings for me +with the camera lucida of the jaws which I had dissected from the +workers of the several sizes. + +With these facts before me, I believe that natural selection, by acting +on the fertile parents, could form a species which should regularly +produce neuters, either all of large size with one form of jaw, or all +of small size with jaws having a widely different structure; or lastly, +and this is our climax of difficulty, one set of workers of one size and +structure, and simultaneously another set of workers of a different size +and structure;—a graduated series having been first formed, as in the +case of the driver ant, and then the extreme forms, from being the most +useful to the community, having been produced in greater and greater +numbers through the natural selection of the parents which generated +them; until none with an intermediate structure were produced. + +Thus, as I believe, the wonderful fact of two distinctly defined castes +of sterile workers existing in the same nest, both widely different from +each other and from their parents, has originated. We can see how useful +their production may have been to a social community of insects, on the +same principle that the division of labour is useful to civilised man. +As ants work by inherited instincts and by inherited tools or weapons, +and not by acquired knowledge and manufactured instruments, a perfect +division of labour could be effected with them only by the workers being +sterile; for had they been fertile, they would have intercrossed, and +their instincts and structure would have become blended. And nature has, +as I believe, effected this admirable division of labour in the +communities of ants, by the means of natural selection. But I am bound +to confess, that, with all my faith in this principle, I should never +have anticipated that natural selection could have been efficient in so +high a degree, had not the case of these neuter insects convinced me of +the fact. I have, therefore, discussed this case, at some little but +wholly insufficient length, in order to show the power of natural selection, and likewise because this is by far the most serious special difficulty, which my theory has encountered. The case, also, is very -interesting, as it proves that with animals, as with plants, any amount of -modification in structure can be effected by the accumulation of numerous, -slight, and as we must call them accidental, variations, which are in any -manner profitable, without exercise or habit having come into play. For no -amount of exercise, or habit, or volition, in the utterly sterile members of a -community could possibly have affected the structure or instincts of the -fertile members, which alone leave descendants. I am surprised that no one has -advanced this demonstrative case of neuter insects, against the well-known -doctrine of Lamarck. - -Summary.—I have endeavoured briefly in this chapter to show that the mental -qualities of our domestic animals vary, and that the variations are inherited. -Still more briefly I have attempted to show that instincts vary slightly in a -state of nature. No one will dispute that instincts are of the highest -importance to each animal. Therefore I can see no difficulty, under changing -conditions of life, in natural selection accumulating slight modifications of -instinct to any extent, in any useful direction. In some cases habit or use and -disuse have probably come into play. I do not pretend that the facts given in -this chapter strengthen in any great degree my theory; but none of the cases of -difficulty, to the best of my judgment, annihilate it. On the other hand, the -fact that instincts are not always absolutely perfect and are liable to -mistakes;—that no instinct has been produced for the exclusive good of other -animals, but that each animal takes advantage of the instincts of others;—that -the canon in natural history, of “natura non facit saltum” is applicable to -instincts as well as to corporeal structure, and is plainly explicable on the -foregoing views, but is otherwise inexplicable,—all tend to corroborate the -theory of natural selection. +interesting, as it proves that with animals, as with plants, any amount +of modification in structure can be effected by the accumulation of +numerous, slight, and as we must call them accidental, variations, which +are in any manner profitable, without exercise or habit having come into +play. For no amount of exercise, or habit, or volition, in the utterly +sterile members of a community could possibly have affected the +structure or instincts of the fertile members, which alone leave +descendants. I am surprised that no one has advanced this demonstrative +case of neuter insects, against the well-known doctrine of Lamarck. + +Summary.—I have endeavoured briefly in this chapter to show that the +mental qualities of our domestic animals vary, and that the variations +are inherited. Still more briefly I have attempted to show that +instincts vary slightly in a state of nature. No one will dispute that +instincts are of the highest importance to each animal. Therefore I can +see no difficulty, under changing conditions of life, in natural +selection accumulating slight modifications of instinct to any extent, +in any useful direction. In some cases habit or use and disuse have +probably come into play. I do not pretend that the facts given in this +chapter strengthen in any great degree my theory; but none of the cases +of difficulty, to the best of my judgment, annihilate it. On the other +hand, the fact that instincts are not always absolutely perfect and are +liable to mistakes;—that no instinct has been produced for the exclusive +good of other animals, but that each animal takes advantage of the +instincts of others;—that the canon in natural history, of “natura non +facit saltum” is applicable to instincts as well as to corporeal +structure, and is plainly explicable on the foregoing views, but is +otherwise inexplicable,—all tend to corroborate the theory of natural +selection. This theory is, also, strengthened by some few other facts in regard to -instincts; as by that common case of closely allied, but certainly distinct, -species, when inhabiting distant parts of the world and living under -considerably different conditions of life, yet often retaining nearly the same -instincts. For instance, we can understand on the principle of inheritance, how -it is that the thrush of South America lines its nest with mud, in the same -peculiar manner as does our British thrush: how it is that the male wrens -(Troglodytes) of North America, build “cock-nests,” to roost in, like the males -of our distinct Kitty-wrens,—a habit wholly unlike that of any other known -bird. Finally, it may not be a logical deduction, but to my imagination it is -far more satisfactory to look at such instincts as the young cuckoo ejecting -its foster-brothers,—ants making slaves,—the larvæ of ichneumonidæ feeding -within the live bodies of caterpillars,—not as specially endowed or created -instincts, but as small consequences of one general law, leading to the -advancement of all organic beings, namely, multiply, vary, let the strongest -live and the weakest die. - -CHAPTER VIII. -HYBRIDISM. - -Distinction between the sterility of first crosses and of hybrids. Sterility -various in degree, not universal, affected by close interbreeding, removed by -domestication. Laws governing the sterility of hybrids. Sterility not a special -endowment, but incidental on other differences. Causes of the sterility of -first crosses and of hybrids. Parallelism between the effects of changed -conditions of life and crossing. Fertility of varieties when crossed and of -their mongrel offspring not universal. Hybrids and mongrels compared -independently of their fertility. Summary. +instincts; as by that common case of closely allied, but certainly +distinct, species, when inhabiting distant parts of the world and living +under considerably different conditions of life, yet often retaining +nearly the same instincts. For instance, we can understand on the +principle of inheritance, how it is that the thrush of South America +lines its nest with mud, in the same peculiar manner as does our British +thrush: how it is that the male wrens (Troglodytes) of North America, +build “cock-nests,” to roost in, like the males of our distinct +Kitty-wrens,—a habit wholly unlike that of any other known bird. +Finally, it may not be a logical deduction, but to my imagination it is +far more satisfactory to look at such instincts as the young cuckoo +ejecting its foster-brothers,—ants making slaves,—the larvæ of +ichneumonidæ feeding within the live bodies of caterpillars,—not as +specially endowed or created instincts, but as small consequences of one +general law, leading to the advancement of all organic beings, namely, +multiply, vary, let the strongest live and the weakest die. + +CHAPTER VIII. HYBRIDISM. + +Distinction between the sterility of first crosses and of hybrids. +Sterility various in degree, not universal, affected by close +interbreeding, removed by domestication. Laws governing the sterility of +hybrids. Sterility not a special endowment, but incidental on other +differences. Causes of the sterility of first crosses and of hybrids. +Parallelism between the effects of changed conditions of life and +crossing. Fertility of varieties when crossed and of their mongrel +offspring not universal. Hybrids and mongrels compared independently of +their fertility. Summary. The view generally entertained by naturalists is that species, when -intercrossed, have been specially endowed with the quality of sterility, in -order to prevent the confusion of all organic forms. This view certainly seems -at first probable, for species within the same country could hardly have kept -distinct had they been capable of crossing freely. The importance of the fact -that hybrids are very generally sterile, has, I think, been much underrated by -some late writers. On the theory of natural selection the case is especially -important, inasmuch as the sterility of hybrids could not possibly be of any -advantage to them, and therefore could not have been acquired by the continued -preservation of successive profitable degrees of sterility. I hope, however, to -be able to show that sterility is not a specially acquired or endowed quality, -but is incidental on other acquired differences. - -In treating this subject, two classes of facts, to a large extent fundamentally -different, have generally been confounded together; namely, the sterility of -two species when first crossed, and the sterility of the hybrids produced from -them. +intercrossed, have been specially endowed with the quality of sterility, +in order to prevent the confusion of all organic forms. This view +certainly seems at first probable, for species within the same country +could hardly have kept distinct had they been capable of crossing +freely. The importance of the fact that hybrids are very generally +sterile, has, I think, been much underrated by some late writers. On the +theory of natural selection the case is especially important, inasmuch +as the sterility of hybrids could not possibly be of any advantage to +them, and therefore could not have been acquired by the continued +preservation of successive profitable degrees of sterility. I hope, +however, to be able to show that sterility is not a specially acquired +or endowed quality, but is incidental on other acquired differences. + +In treating this subject, two classes of facts, to a large extent +fundamentally different, have generally been confounded together; +namely, the sterility of two species when first crossed, and the +sterility of the hybrids produced from them. Pure species have of course their organs of reproduction in a perfect -condition, yet when intercrossed they produce either few or no offspring. -Hybrids, on the other hand, have their reproductive organs functionally -impotent, as may be clearly seen in the state of the male element in both -plants and animals; though the organs themselves are perfect in structure, as -far as the microscope reveals. In the first case the two sexual elements which -go to form the embryo are perfect; in the second case they are either not at -all developed, or are imperfectly developed. This distinction is important, -when the cause of the sterility, which is common to the two cases, has to be -considered. The distinction has probably been slurred over, owing to the -sterility in both cases being looked on as a special endowment, beyond the -province of our reasoning powers. - -The fertility of varieties, that is of the forms known or believed to have -descended from common parents, when intercrossed, and likewise the fertility of -their mongrel offspring, is, on my theory, of equal importance with the -sterility of species; for it seems to make a broad and clear distinction -between varieties and species. - -First, for the sterility of species when crossed and of their hybrid offspring. -It is impossible to study the several memoirs and works of those two -conscientious and admirable observers, Kölreuter and Gärtner, who almost -devoted their lives to this subject, without being deeply impressed with the -high generality of some degree of sterility. Kölreuter makes the rule -universal; but then he cuts the knot, for in ten cases in which he found two -forms, considered by most authors as distinct species, quite fertile together, -he unhesitatingly ranks them as varieties. Gärtner, also, makes the rule -equally universal; and he disputes the entire fertility of Kölreuter’s ten -cases. But in these and in many other cases, Gärtner is obliged carefully to -count the seeds, in order to show that there is any degree of sterility. He -always compares the maximum number of seeds produced by two species when -crossed and by their hybrid offspring, with the average number produced by both -pure parent-species in a state of nature. But a serious cause of error seems to -me to be here introduced: a plant to be hybridised must be castrated, and, what -is often more important, must be secluded in order to prevent pollen being -brought to it by insects from other plants. Nearly all the plants -experimentised on by Gärtner were potted, and apparently were kept in a chamber -in his house. That these processes are often injurious to the fertility of a -plant cannot be doubted; for Gärtner gives in his table about a score of cases -of plants which he castrated, and artificially fertilised with their own -pollen, and (excluding all cases such as the Leguminosæ, in which there is an -acknowledged difficulty in the manipulation) half of these twenty plants had -their fertility in some degree impaired. Moreover, as Gärtner during several -years repeatedly crossed the primrose and cowslip, which we have such good -reason to believe to be varieties, and only once or twice succeeded in getting -fertile seed; as he found the common red and blue pimpernels (Anagallis -arvensis and coerulea), which the best botanists rank as varieties, absolutely -sterile together; and as he came to the same conclusion in several other -analogous cases; it seems to me that we may well be permitted to doubt whether -many other species are really so sterile, when intercrossed, as Gärtner -believes. - -It is certain, on the one hand, that the sterility of various species when -crossed is so different in degree and graduates away so insensibly, and, on the -other hand, that the fertility of pure species is so easily affected by various -circumstances, that for all practical purposes it is most difficult to say -where perfect fertility ends and sterility begins. I think no better evidence -of this can be required than that the two most experienced observers who have -ever lived, namely, Kölreuter and Gärtner, should have arrived at diametrically -opposite conclusions in regard to the very same species. It is also most -instructive to compare—but I have not space here to enter on details—the -evidence advanced by our best botanists on the question whether certain -doubtful forms should be ranked as species or varieties, with the evidence from +condition, yet when intercrossed they produce either few or no +offspring. Hybrids, on the other hand, have their reproductive organs +functionally impotent, as may be clearly seen in the state of the male +element in both plants and animals; though the organs themselves are +perfect in structure, as far as the microscope reveals. In the first +case the two sexual elements which go to form the embryo are perfect; in +the second case they are either not at all developed, or are imperfectly +developed. This distinction is important, when the cause of the +sterility, which is common to the two cases, has to be considered. The +distinction has probably been slurred over, owing to the sterility in +both cases being looked on as a special endowment, beyond the province +of our reasoning powers. + +The fertility of varieties, that is of the forms known or believed to +have descended from common parents, when intercrossed, and likewise the +fertility of their mongrel offspring, is, on my theory, of equal +importance with the sterility of species; for it seems to make a broad +and clear distinction between varieties and species. + +First, for the sterility of species when crossed and of their hybrid +offspring. It is impossible to study the several memoirs and works of +those two conscientious and admirable observers, Kölreuter and Gärtner, +who almost devoted their lives to this subject, without being deeply +impressed with the high generality of some degree of sterility. +Kölreuter makes the rule universal; but then he cuts the knot, for in +ten cases in which he found two forms, considered by most authors as +distinct species, quite fertile together, he unhesitatingly ranks them +as varieties. Gärtner, also, makes the rule equally universal; and he +disputes the entire fertility of Kölreuter’s ten cases. But in these and +in many other cases, Gärtner is obliged carefully to count the seeds, in +order to show that there is any degree of sterility. He always compares +the maximum number of seeds produced by two species when crossed and by +their hybrid offspring, with the average number produced by both pure +parent-species in a state of nature. But a serious cause of error seems +to me to be here introduced: a plant to be hybridised must be castrated, +and, what is often more important, must be secluded in order to prevent +pollen being brought to it by insects from other plants. Nearly all the +plants experimentised on by Gärtner were potted, and apparently were +kept in a chamber in his house. That these processes are often injurious +to the fertility of a plant cannot be doubted; for Gärtner gives in his +table about a score of cases of plants which he castrated, and +artificially fertilised with their own pollen, and (excluding all cases +such as the Leguminosæ, in which there is an acknowledged difficulty in +the manipulation) half of these twenty plants had their fertility in +some degree impaired. Moreover, as Gärtner during several years +repeatedly crossed the primrose and cowslip, which we have such good +reason to believe to be varieties, and only once or twice succeeded in +getting fertile seed; as he found the common red and blue pimpernels +(Anagallis arvensis and coerulea), which the best botanists rank as +varieties, absolutely sterile together; and as he came to the same +conclusion in several other analogous cases; it seems to me that we may +well be permitted to doubt whether many other species are really so +sterile, when intercrossed, as Gärtner believes. + +It is certain, on the one hand, that the sterility of various species +when crossed is so different in degree and graduates away so insensibly, +and, on the other hand, that the fertility of pure species is so easily +affected by various circumstances, that for all practical purposes it is +most difficult to say where perfect fertility ends and sterility begins. +I think no better evidence of this can be required than that the two +most experienced observers who have ever lived, namely, Kölreuter and +Gärtner, should have arrived at diametrically opposite conclusions in +regard to the very same species. It is also most instructive to +compare—but I have not space here to enter on details—the evidence +advanced by our best botanists on the question whether certain doubtful +forms should be ranked as species or varieties, with the evidence from fertility adduced by different hybridisers, or by the same author, from -experiments made during different years. It can thus be shown that neither -sterility nor fertility affords any clear distinction between species and -varieties; but that the evidence from this source graduates away, and is -doubtful in the same degree as is the evidence derived from other -constitutional and structural differences. - -In regard to the sterility of hybrids in successive generations; though Gärtner -was enabled to rear some hybrids, carefully guarding them from a cross with -either pure parent, for six or seven, and in one case for ten generations, yet -he asserts positively that their fertility never increased, but generally -greatly decreased. I do not doubt that this is usually the case, and that the -fertility often suddenly decreases in the first few generations. Nevertheless I -believe that in all these experiments the fertility has been diminished by an -independent cause, namely, from close interbreeding. I have collected so large -a body of facts, showing that close interbreeding lessens fertility, and, on -the other hand, that an occasional cross with a distinct individual or variety -increases fertility, that I cannot doubt the correctness of this almost -universal belief amongst breeders. Hybrids are seldom raised by -experimentalists in great numbers; and as the parent-species, or other allied -hybrids, generally grow in the same garden, the visits of insects must be -carefully prevented during the flowering season: hence hybrids will generally -be fertilised during each generation by their own individual pollen; and I am -convinced that this would be injurious to their fertility, already lessened by -their hybrid origin. I am strengthened in this conviction by a remarkable -statement repeatedly made by Gärtner, namely, that if even the less fertile -hybrids be artificially fertilised with hybrid pollen of the same kind, their -fertility, notwithstanding the frequent ill effects of manipulation, sometimes -decidedly increases, and goes on increasing. Now, in artificial fertilisation -pollen is as often taken by chance (as I know from my own experience) from the -anthers of another flower, as from the anthers of the flower itself which is to -be fertilised; so that a cross between two flowers, though probably on the same -plant, would be thus effected. Moreover, whenever complicated experiments are -in progress, so careful an observer as Gärtner would have castrated his -hybrids, and this would have insured in each generation a cross with the pollen -from a distinct flower, either from the same plant or from another plant of the -same hybrid nature. And thus, the strange fact of the increase of fertility in -the successive generations of artificially fertilised hybrids may, I believe, -be accounted for by close interbreeding having been avoided. +experiments made during different years. It can thus be shown that +neither sterility nor fertility affords any clear distinction between +species and varieties; but that the evidence from this source graduates +away, and is doubtful in the same degree as is the evidence derived from +other constitutional and structural differences. + +In regard to the sterility of hybrids in successive generations; though +Gärtner was enabled to rear some hybrids, carefully guarding them from a +cross with either pure parent, for six or seven, and in one case for ten +generations, yet he asserts positively that their fertility never +increased, but generally greatly decreased. I do not doubt that this is +usually the case, and that the fertility often suddenly decreases in the +first few generations. Nevertheless I believe that in all these +experiments the fertility has been diminished by an independent cause, +namely, from close interbreeding. I have collected so large a body of +facts, showing that close interbreeding lessens fertility, and, on the +other hand, that an occasional cross with a distinct individual or +variety increases fertility, that I cannot doubt the correctness of this +almost universal belief amongst breeders. Hybrids are seldom raised by +experimentalists in great numbers; and as the parent-species, or other +allied hybrids, generally grow in the same garden, the visits of insects +must be carefully prevented during the flowering season: hence hybrids +will generally be fertilised during each generation by their own +individual pollen; and I am convinced that this would be injurious to +their fertility, already lessened by their hybrid origin. I am +strengthened in this conviction by a remarkable statement repeatedly +made by Gärtner, namely, that if even the less fertile hybrids be +artificially fertilised with hybrid pollen of the same kind, their +fertility, notwithstanding the frequent ill effects of manipulation, +sometimes decidedly increases, and goes on increasing. Now, in +artificial fertilisation pollen is as often taken by chance (as I know +from my own experience) from the anthers of another flower, as from the +anthers of the flower itself which is to be fertilised; so that a cross +between two flowers, though probably on the same plant, would be thus +effected. Moreover, whenever complicated experiments are in progress, so +careful an observer as Gärtner would have castrated his hybrids, and +this would have insured in each generation a cross with the pollen from +a distinct flower, either from the same plant or from another plant of +the same hybrid nature. And thus, the strange fact of the increase of +fertility in the successive generations of artificially fertilised +hybrids may, I believe, be accounted for by close interbreeding having +been avoided. Now let us turn to the results arrived at by the third most experienced -hybridiser, namely, the Honourable and Reverend W. Herbert. He is as emphatic -in his conclusion that some hybrids are perfectly fertile—as fertile as the -pure parent-species—as are Kölreuter and Gärtner that some degree of sterility -between distinct species is a universal law of nature. He experimentised on -some of the very same species as did Gärtner. The difference in their results -may, I think, be in part accounted for by Herbert’s great horticultural skill, -and by his having hothouses at his command. Of his many important statements I -will here give only a single one as an example, namely, that “every ovule in a -pod of Crinum capense fertilised by C. revolutum produced a plant, which (he -says) I never saw to occur in a case of its natural fecundation.” So that we -here have perfect, or even more than commonly perfect, fertility in a first -cross between two distinct species. - -This case of the Crinum leads me to refer to a most singular fact, namely, that -there are individual plants, as with certain species of Lobelia, and with all -the species of the genus Hippeastrum, which can be far more easily fertilised -by the pollen of another and distinct species, than by their own pollen. For -these plants have been found to yield seed to the pollen of a distinct species, -though quite sterile with their own pollen, notwithstanding that their own -pollen was found to be perfectly good, for it fertilised distinct species. So -that certain individual plants and all the individuals of certain species can -actually be hybridised much more readily than they can be self-fertilised! For -instance, a bulb of Hippeastrum aulicum produced four flowers; three were -fertilised by Herbert with their own pollen, and the fourth was subsequently -fertilised by the pollen of a compound hybrid descended from three other and -distinct species: the result was that “the ovaries of the three first flowers -soon ceased to grow, and after a few days perished entirely, whereas the pod -impregnated by the pollen of the hybrid made vigorous growth and rapid progress -to maturity, and bore good seed, which vegetated freely.” In a letter to me, in -1839, Mr. Herbert told me that he had then tried the experiment during five -years, and he continued to try it during several subsequent years, and always -with the same result. This result has, also, been confirmed by other observers -in the case of Hippeastrum with its sub-genera, and in the case of some other -genera, as Lobelia, Passiflora and Verbascum. Although the plants in these -experiments appeared perfectly healthy, and although both the ovules and pollen -of the same flower were perfectly good with respect to other species, yet as -they were functionally imperfect in their mutual self-action, we must infer -that the plants were in an unnatural state. Nevertheless these facts show on -what slight and mysterious causes the lesser or greater fertility of species -when crossed, in comparison with the same species when self-fertilised, -sometimes depends. - -The practical experiments of horticulturists, though not made with scientific -precision, deserve some notice. It is notorious in how complicated a manner the -species of Pelargonium, Fuchsia, Calceolaria, Petunia, Rhododendron, etc., have -been crossed, yet many of these hybrids seed freely. For instance, Herbert -asserts that a hybrid from Calceolaria integrifolia and plantaginea, species -most widely dissimilar in general habit, “reproduced itself as perfectly as if -it had been a natural species from the mountains of Chile.” I have taken some -pains to ascertain the degree of fertility of some of the complex crosses of -Rhododendrons, and I am assured that many of them are perfectly fertile. Mr. C. -Noble, for instance, informs me that he raises stocks for grafting from a -hybrid between Rhododendron Ponticum and Catawbiense, and that this hybrid -“seeds as freely as it is possible to imagine.” Had hybrids, when fairly -treated, gone on decreasing in fertility in each successive generation, as -Gärtner believes to be the case, the fact would have been notorious to -nurserymen. Horticulturists raise large beds of the same hybrids, and such -alone are fairly treated, for by insect agency the several individuals of the -same hybrid variety are allowed to freely cross with each other, and the -injurious influence of close interbreeding is thus prevented. Any one may -readily convince himself of the efficiency of insect-agency by examining the -flowers of the more sterile kinds of hybrid rhododendrons, which produce no -pollen, for he will find on their stigmas plenty of pollen brought from other +hybridiser, namely, the Honourable and Reverend W. Herbert. He is as +emphatic in his conclusion that some hybrids are perfectly fertile—as +fertile as the pure parent-species—as are Kölreuter and Gärtner that +some degree of sterility between distinct species is a universal law of +nature. He experimentised on some of the very same species as did +Gärtner. The difference in their results may, I think, be in part +accounted for by Herbert’s great horticultural skill, and by his having +hothouses at his command. Of his many important statements I will here +give only a single one as an example, namely, that “every ovule in a pod +of Crinum capense fertilised by C. revolutum produced a plant, which (he +says) I never saw to occur in a case of its natural fecundation.” So +that we here have perfect, or even more than commonly perfect, fertility +in a first cross between two distinct species. + +This case of the Crinum leads me to refer to a most singular fact, +namely, that there are individual plants, as with certain species of +Lobelia, and with all the species of the genus Hippeastrum, which can be +far more easily fertilised by the pollen of another and distinct +species, than by their own pollen. For these plants have been found to +yield seed to the pollen of a distinct species, though quite sterile +with their own pollen, notwithstanding that their own pollen was found +to be perfectly good, for it fertilised distinct species. So that +certain individual plants and all the individuals of certain species can +actually be hybridised much more readily than they can be +self-fertilised! For instance, a bulb of Hippeastrum aulicum produced +four flowers; three were fertilised by Herbert with their own pollen, +and the fourth was subsequently fertilised by the pollen of a compound +hybrid descended from three other and distinct species: the result was +that “the ovaries of the three first flowers soon ceased to grow, and +after a few days perished entirely, whereas the pod impregnated by the +pollen of the hybrid made vigorous growth and rapid progress to +maturity, and bore good seed, which vegetated freely.” In a letter to +me, in 1839, Mr. Herbert told me that he had then tried the experiment +during five years, and he continued to try it during several subsequent +years, and always with the same result. This result has, also, been +confirmed by other observers in the case of Hippeastrum with its +sub-genera, and in the case of some other genera, as Lobelia, Passiflora +and Verbascum. Although the plants in these experiments appeared +perfectly healthy, and although both the ovules and pollen of the same +flower were perfectly good with respect to other species, yet as they +were functionally imperfect in their mutual self-action, we must infer +that the plants were in an unnatural state. Nevertheless these facts +show on what slight and mysterious causes the lesser or greater +fertility of species when crossed, in comparison with the same species +when self-fertilised, sometimes depends. + +The practical experiments of horticulturists, though not made with +scientific precision, deserve some notice. It is notorious in how +complicated a manner the species of Pelargonium, Fuchsia, Calceolaria, +Petunia, Rhododendron, etc., have been crossed, yet many of these +hybrids seed freely. For instance, Herbert asserts that a hybrid from +Calceolaria integrifolia and plantaginea, species most widely dissimilar +in general habit, “reproduced itself as perfectly as if it had been a +natural species from the mountains of Chile.” I have taken some pains to +ascertain the degree of fertility of some of the complex crosses of +Rhododendrons, and I am assured that many of them are perfectly fertile. +Mr. C. Noble, for instance, informs me that he raises stocks for +grafting from a hybrid between Rhododendron Ponticum and Catawbiense, +and that this hybrid “seeds as freely as it is possible to imagine.” Had +hybrids, when fairly treated, gone on decreasing in fertility in each +successive generation, as Gärtner believes to be the case, the fact +would have been notorious to nurserymen. Horticulturists raise large +beds of the same hybrids, and such alone are fairly treated, for by +insect agency the several individuals of the same hybrid variety are +allowed to freely cross with each other, and the injurious influence of +close interbreeding is thus prevented. Any one may readily convince +himself of the efficiency of insect-agency by examining the flowers of +the more sterile kinds of hybrid rhododendrons, which produce no pollen, +for he will find on their stigmas plenty of pollen brought from other flowers. -In regard to animals, much fewer experiments have been carefully tried than -with plants. If our systematic arrangements can be trusted, that is if the -genera of animals are as distinct from each other, as are the genera of plants, -then we may infer that animals more widely separated in the scale of nature can -be more easily crossed than in the case of plants; but the hybrids themselves -are, I think, more sterile. I doubt whether any case of a perfectly fertile -hybrid animal can be considered as thoroughly well authenticated. It should, -however, be borne in mind that, owing to few animals breeding freely under -confinement, few experiments have been fairly tried: for instance, the -canary-bird has been crossed with nine other finches, but as not one of these -nine species breeds freely in confinement, we have no right to expect that the -first crosses between them and the canary, or that their hybrids, should be -perfectly fertile. Again, with respect to the fertility in successive -generations of the more fertile hybrid animals, I hardly know of an instance in -which two families of the same hybrid have been raised at the same time from -different parents, so as to avoid the ill effects of close interbreeding. On -the contrary, brothers and sisters have usually been crossed in each successive -generation, in opposition to the constantly repeated admonition of every -breeder. And in this case, it is not at all surprising that the inherent -sterility in the hybrids should have gone on increasing. If we were to act -thus, and pair brothers and sisters in the case of any pure animal, which from -any cause had the least tendency to sterility, the breed would assuredly be -lost in a very few generations. - -Although I do not know of any thoroughly well-authenticated cases of perfectly -fertile hybrid animals, I have some reason to believe that the hybrids from -Cervulus vaginalis and Reevesii, and from Phasianus colchicus with P. torquatus -and with P. versicolor are perfectly fertile. The hybrids from the common and -Chinese geese (A. cygnoides), species which are so different that they are -generally ranked in distinct genera, have often bred in this country with -either pure parent, and in one single instance they have bred inter se. This -was effected by Mr. Eyton, who raised two hybrids from the same parents but -from different hatches; and from these two birds he raised no less than eight -hybrids (grandchildren of the pure geese) from one nest. In India, however, -these cross-bred geese must be far more fertile; for I am assured by two -eminently capable judges, namely Mr. Blyth and Capt. Hutton, that whole flocks -of these crossed geese are kept in various parts of the country; and as they -are kept for profit, where neither pure parent-species exists, they must -certainly be highly fertile. - -A doctrine which originated with Pallas, has been largely accepted by modern -naturalists; namely, that most of our domestic animals have descended from two -or more aboriginal species, since commingled by intercrossing. On this view, -the aboriginal species must either at first have produced quite fertile -hybrids, or the hybrids must have become in subsequent generations quite -fertile under domestication. This latter alternative seems to me the most -probable, and I am inclined to believe in its truth, although it rests on no -direct evidence. I believe, for instance, that our dogs have descended from -several wild stocks; yet, with perhaps the exception of certain indigenous -domestic dogs of South America, all are quite fertile together; and analogy -makes me greatly doubt, whether the several aboriginal species would at first -have freely bred together and have produced quite fertile hybrids. So again -there is reason to believe that our European and the humped Indian cattle are -quite fertile together; but from facts communicated to me by Mr. Blyth, I think -they must be considered as distinct species. On this view of the origin of many -of our domestic animals, we must either give up the belief of the almost -universal sterility of distinct species of animals when crossed; or we must -look at sterility, not as an indelible characteristic, but as one capable of -being removed by domestication. - -Finally, looking to all the ascertained facts on the intercrossing of plants -and animals, it may be concluded that some degree of sterility, both in first -crosses and in hybrids,is an extremely general result; but that it cannot, -under our present state of knowledge, be considered as absolutely universal. - -Laws governing the Sterility of first Crosses and of Hybrids.—We will now -consider a little more in detail the circumstances and rules governing the -sterility of first crosses and of hybrids. Our chief object will be to see -whether or not the rules indicate that species have specially been endowed with -this quality, in order to prevent their crossing and blending together in utter -confusion. The following rules and conclusions are chiefly drawn up from -Gärtner’s admirable work on the hybridisation of plants. I have taken much -pains to ascertain how far the rules apply to animals, and considering how -scanty our knowledge is in regard to hybrid animals, I have been surprised to -find how generally the same rules apply to both kingdoms. - -It has been already remarked, that the degree of fertility, both of first -crosses and of hybrids, graduates from zero to perfect fertility. It is -surprising in how many curious ways this gradation can be shown to exist; but -only the barest outline of the facts can here be given. When pollen from a -plant of one family is placed on the stigma of a plant of a distinct family, it -exerts no more influence than so much inorganic dust. From this absolute zero -of fertility, the pollen of different species of the same genus applied to the -stigma of some one species, yields a perfect gradation in the number of seeds -produced, up to nearly complete or even quite complete fertility; and, as we -have seen, in certain abnormal cases, even to an excess of fertility, beyond -that which the plant’s own pollen will produce. So in hybrids themselves, there -are some which never have produced, and probably never would produce, even with -the pollen of either pure parent, a single fertile seed: but in some of these -cases a first trace of fertility may be detected, by the pollen of one of the -pure parent-species causing the flower of the hybrid to wither earlier than it -otherwise would have done; and the early withering of the flower is well known -to be a sign of incipient fertilisation. From this extreme degree of sterility -we have self-fertilised hybrids producing a greater and greater number of seeds -up to perfect fertility. - -Hybrids from two species which are very difficult to cross, and which rarely -produce any offspring, are generally very sterile; but the parallelism between -the difficulty of making a first cross, and the sterility of the hybrids thus -produced—two classes of facts which are generally confounded together—is by no -means strict. There are many cases, in which two pure species can be united -with unusual facility, and produce numerous hybrid-offspring, yet these hybrids -are remarkably sterile. On the other hand, there are species which can be -crossed very rarely, or with extreme difficulty, but the hybrids, when at last -produced, are very fertile. Even within the limits of the same genus, for -instance in Dianthus, these two opposite cases occur. - -The fertility, both of first crosses and of hybrids, is more easily affected by -unfavourable conditions, than is the fertility of pure species. But the degree -of fertility is likewise innately variable; for it is not always the same when -the same two species are crossed under the same circumstances, but depends in -part upon the constitution of the individuals which happen to have been chosen -for the experiment. So it is with hybrids, for their degree of fertility is -often found to differ greatly in the several individuals raised from seed out -of the same capsule and exposed to exactly the same conditions. - -By the term systematic affinity is meant, the resemblance between species in -structure and in constitution, more especially in the structure of parts which -are of high physiological importance and which differ little in the allied -species. Now the fertility of first crosses between species, and of the hybrids -produced from them, is largely governed by their systematic affinity. This is -clearly shown by hybrids never having been raised between species ranked by -systematists in distinct families; and on the other hand, by very closely -allied species generally uniting with facility. But the correspondence between -systematic affinity and the facility of crossing is by no means strict. A -multitude of cases could be given of very closely allied species which will not -unite, or only with extreme difficulty; and on the other hand of very distinct -species which unite with the utmost facility. In the same family there may be a -genus, as Dianthus, in which very many species can most readily be crossed; and -another genus, as Silene, in which the most persevering efforts have failed to -produce between extremely close species a single hybrid. Even within the limits -of the same genus, we meet with this same difference; for instance, the many -species of Nicotiana have been more largely crossed than the species of almost -any other genus; but Gärtner found that N. acuminata, which is not a -particularly distinct species, obstinately failed to fertilise, or to be -fertilised by, no less than eight other species of Nicotiana. Very many -analogous facts could be given. - -No one has been able to point out what kind, or what amount, of difference in -any recognisable character is sufficient to prevent two species crossing. It -can be shown that plants most widely different in habit and general appearance, -and having strongly marked differences in every part of the flower, even in the -pollen, in the fruit, and in the cotyledons, can be crossed. Annual and -perennial plants, deciduous and evergreen trees, plants inhabiting different -stations and fitted for extremely different climates, can often be crossed with -ease. - -By a reciprocal cross between two species, I mean the case, for instance, of a -stallion-horse being first crossed with a female-ass, and then a male-ass with -a mare: these two species may then be said to have been reciprocally crossed. -There is often the widest possible difference in the facility of making -reciprocal crosses. Such cases are highly important, for they prove that the -capacity in any two species to cross is often completely independent of their -systematic affinity, or of any recognisable difference in their whole -organisation. On the other hand, these cases clearly show that the capacity for -crossing is connected with constitutional differences imperceptible by us, and +In regard to animals, much fewer experiments have been carefully tried +than with plants. If our systematic arrangements can be trusted, that is +if the genera of animals are as distinct from each other, as are the +genera of plants, then we may infer that animals more widely separated +in the scale of nature can be more easily crossed than in the case of +plants; but the hybrids themselves are, I think, more sterile. I doubt +whether any case of a perfectly fertile hybrid animal can be considered +as thoroughly well authenticated. It should, however, be borne in mind +that, owing to few animals breeding freely under confinement, few +experiments have been fairly tried: for instance, the canary-bird has +been crossed with nine other finches, but as not one of these nine +species breeds freely in confinement, we have no right to expect that +the first crosses between them and the canary, or that their hybrids, +should be perfectly fertile. Again, with respect to the fertility in +successive generations of the more fertile hybrid animals, I hardly know +of an instance in which two families of the same hybrid have been raised +at the same time from different parents, so as to avoid the ill effects +of close interbreeding. On the contrary, brothers and sisters have +usually been crossed in each successive generation, in opposition to the +constantly repeated admonition of every breeder. And in this case, it is +not at all surprising that the inherent sterility in the hybrids should +have gone on increasing. If we were to act thus, and pair brothers and +sisters in the case of any pure animal, which from any cause had the +least tendency to sterility, the breed would assuredly be lost in a very +few generations. + +Although I do not know of any thoroughly well-authenticated cases of +perfectly fertile hybrid animals, I have some reason to believe that the +hybrids from Cervulus vaginalis and Reevesii, and from Phasianus +colchicus with P. torquatus and with P. versicolor are perfectly +fertile. The hybrids from the common and Chinese geese (A. cygnoides), +species which are so different that they are generally ranked in +distinct genera, have often bred in this country with either pure +parent, and in one single instance they have bred inter se. This was +effected by Mr. Eyton, who raised two hybrids from the same parents but +from different hatches; and from these two birds he raised no less than +eight hybrids (grandchildren of the pure geese) from one nest. In India, +however, these cross-bred geese must be far more fertile; for I am +assured by two eminently capable judges, namely Mr. Blyth and Capt. +Hutton, that whole flocks of these crossed geese are kept in various +parts of the country; and as they are kept for profit, where neither +pure parent-species exists, they must certainly be highly fertile. + +A doctrine which originated with Pallas, has been largely accepted by +modern naturalists; namely, that most of our domestic animals have +descended from two or more aboriginal species, since commingled by +intercrossing. On this view, the aboriginal species must either at first +have produced quite fertile hybrids, or the hybrids must have become in +subsequent generations quite fertile under domestication. This latter +alternative seems to me the most probable, and I am inclined to believe +in its truth, although it rests on no direct evidence. I believe, for +instance, that our dogs have descended from several wild stocks; yet, +with perhaps the exception of certain indigenous domestic dogs of South +America, all are quite fertile together; and analogy makes me greatly +doubt, whether the several aboriginal species would at first have freely +bred together and have produced quite fertile hybrids. So again there is +reason to believe that our European and the humped Indian cattle are +quite fertile together; but from facts communicated to me by Mr. Blyth, +I think they must be considered as distinct species. On this view of the +origin of many of our domestic animals, we must either give up the +belief of the almost universal sterility of distinct species of animals +when crossed; or we must look at sterility, not as an indelible +characteristic, but as one capable of being removed by domestication. + +Finally, looking to all the ascertained facts on the intercrossing of +plants and animals, it may be concluded that some degree of sterility, +both in first crosses and in hybrids,is an extremely general result; but +that it cannot, under our present state of knowledge, be considered as +absolutely universal. + +Laws governing the Sterility of first Crosses and of Hybrids.—We will +now consider a little more in detail the circumstances and rules +governing the sterility of first crosses and of hybrids. Our chief +object will be to see whether or not the rules indicate that species +have specially been endowed with this quality, in order to prevent their +crossing and blending together in utter confusion. The following rules +and conclusions are chiefly drawn up from Gärtner’s admirable work on +the hybridisation of plants. I have taken much pains to ascertain how +far the rules apply to animals, and considering how scanty our knowledge +is in regard to hybrid animals, I have been surprised to find how +generally the same rules apply to both kingdoms. + +It has been already remarked, that the degree of fertility, both of +first crosses and of hybrids, graduates from zero to perfect fertility. +It is surprising in how many curious ways this gradation can be shown to +exist; but only the barest outline of the facts can here be given. When +pollen from a plant of one family is placed on the stigma of a plant of +a distinct family, it exerts no more influence than so much inorganic +dust. From this absolute zero of fertility, the pollen of different +species of the same genus applied to the stigma of some one species, +yields a perfect gradation in the number of seeds produced, up to nearly +complete or even quite complete fertility; and, as we have seen, in +certain abnormal cases, even to an excess of fertility, beyond that +which the plant’s own pollen will produce. So in hybrids themselves, +there are some which never have produced, and probably never would +produce, even with the pollen of either pure parent, a single fertile +seed: but in some of these cases a first trace of fertility may be +detected, by the pollen of one of the pure parent-species causing the +flower of the hybrid to wither earlier than it otherwise would have +done; and the early withering of the flower is well known to be a sign +of incipient fertilisation. From this extreme degree of sterility we +have self-fertilised hybrids producing a greater and greater number of +seeds up to perfect fertility. + +Hybrids from two species which are very difficult to cross, and which +rarely produce any offspring, are generally very sterile; but the +parallelism between the difficulty of making a first cross, and the +sterility of the hybrids thus produced—two classes of facts which are +generally confounded together—is by no means strict. There are many +cases, in which two pure species can be united with unusual facility, +and produce numerous hybrid-offspring, yet these hybrids are remarkably +sterile. On the other hand, there are species which can be crossed very +rarely, or with extreme difficulty, but the hybrids, when at last +produced, are very fertile. Even within the limits of the same genus, +for instance in Dianthus, these two opposite cases occur. + +The fertility, both of first crosses and of hybrids, is more easily +affected by unfavourable conditions, than is the fertility of pure +species. But the degree of fertility is likewise innately variable; for +it is not always the same when the same two species are crossed under +the same circumstances, but depends in part upon the constitution of the +individuals which happen to have been chosen for the experiment. So it +is with hybrids, for their degree of fertility is often found to differ +greatly in the several individuals raised from seed out of the same +capsule and exposed to exactly the same conditions. + +By the term systematic affinity is meant, the resemblance between +species in structure and in constitution, more especially in the +structure of parts which are of high physiological importance and which +differ little in the allied species. Now the fertility of first crosses +between species, and of the hybrids produced from them, is largely +governed by their systematic affinity. This is clearly shown by hybrids +never having been raised between species ranked by systematists in +distinct families; and on the other hand, by very closely allied species +generally uniting with facility. But the correspondence between +systematic affinity and the facility of crossing is by no means strict. +A multitude of cases could be given of very closely allied species which +will not unite, or only with extreme difficulty; and on the other hand +of very distinct species which unite with the utmost facility. In the +same family there may be a genus, as Dianthus, in which very many +species can most readily be crossed; and another genus, as Silene, in +which the most persevering efforts have failed to produce between +extremely close species a single hybrid. Even within the limits of the +same genus, we meet with this same difference; for instance, the many +species of Nicotiana have been more largely crossed than the species of +almost any other genus; but Gärtner found that N. acuminata, which is +not a particularly distinct species, obstinately failed to fertilise, or +to be fertilised by, no less than eight other species of Nicotiana. Very +many analogous facts could be given. + +No one has been able to point out what kind, or what amount, of +difference in any recognisable character is sufficient to prevent two +species crossing. It can be shown that plants most widely different in +habit and general appearance, and having strongly marked differences in +every part of the flower, even in the pollen, in the fruit, and in the +cotyledons, can be crossed. Annual and perennial plants, deciduous and +evergreen trees, plants inhabiting different stations and fitted for +extremely different climates, can often be crossed with ease. + +By a reciprocal cross between two species, I mean the case, for +instance, of a stallion-horse being first crossed with a female-ass, and +then a male-ass with a mare: these two species may then be said to have +been reciprocally crossed. There is often the widest possible +difference in the facility of making reciprocal crosses. Such cases are +highly important, for they prove that the capacity in any two species to +cross is often completely independent of their systematic affinity, or +of any recognisable difference in their whole organisation. On the other +hand, these cases clearly show that the capacity for crossing is +connected with constitutional differences imperceptible by us, and confined to the reproductive system. This difference in the result of reciprocal crosses between the same two species was long ago observed by -Kölreuter. To give an instance: Mirabilis jalappa can easily be fertilised by -the pollen of M. longiflora, and the hybrids thus produced are sufficiently -fertile; but Kölreuter tried more than two hundred times, during eight -following years, to fertilise reciprocally M. longiflora with the pollen of M. -jalappa, and utterly failed. Several other equally striking cases could be -given. Thuret has observed the same fact with certain sea-weeds or Fuci. -Gärtner, moreover, found that this difference of facility in making reciprocal -crosses is extremely common in a lesser degree. He has observed it even between -forms so closely related (as Matthiola annua and glabra) that many botanists -rank them only as varieties. It is also a remarkable fact, that hybrids raised -from reciprocal crosses, though of course compounded of the very same two -species, the one species having first been used as the father and then as the -mother, generally differ in fertility in a small, and occasionally in a high -degree. - -Several other singular rules could be given from Gärtner: for instance, some -species have a remarkable power of crossing with other species; other species -of the same genus have a remarkable power of impressing their likeness on their -hybrid offspring; but these two powers do not at all necessarily go together. -There are certain hybrids which instead of having, as is usual, an intermediate -character between their two parents, always closely resemble one of them; and -such hybrids, though externally so like one of their pure parent-species, are -with rare exceptions extremely sterile. So again amongst hybrids which are -usually intermediate in structure between their parents, exceptional and -abnormal individuals sometimes are born, which closely resemble one of their -pure parents; and these hybrids are almost always utterly sterile, even when -the other hybrids raised from seed from the same capsule have a considerable -degree of fertility. These facts show how completely fertility in the hybrid is -independent of its external resemblance to either pure parent. - -Considering the several rules now given, which govern the fertility of first -crosses and of hybrids, we see that when forms, which must be considered as -good and distinct species, are united, their fertility graduates from zero to -perfect fertility, or even to fertility under certain conditions in excess. -That their fertility, besides being eminently susceptible to favourable and -unfavourable conditions, is innately variable. That it is by no means always -the same in degree in the first cross and in the hybrids produced from this -cross. That the fertility of hybrids is not related to the degree in which they -resemble in external appearance either parent. And lastly, that the facility of -making a first cross between any two species is not always governed by their -systematic affinity or degree of resemblance to each other. This latter -statement is clearly proved by reciprocal crosses between the same two species, -for according as the one species or the other is used as the father or the -mother, there is generally some difference, and occasionally the widest -possible difference, in the facility of effecting an union. The hybrids, -moreover, produced from reciprocal crosses often differ in fertility. - -Now do these complex and singular rules indicate that species have been endowed -with sterility simply to prevent their becoming confounded in nature? I think -not. For why should the sterility be so extremely different in degree, when -various species are crossed, all of which we must suppose it would be equally -important to keep from blending together? Why should the degree of sterility be -innately variable in the individuals of the same species? Why should some -species cross with facility, and yet produce very sterile hybrids; and other -species cross with extreme difficulty, and yet produce fairly fertile hybrids? -Why should there often be so great a difference in the result of a reciprocal -cross between the same two species? Why, it may even be asked, has the -production of hybrids been permitted? to grant to species the special power of -producing hybrids, and then to stop their further propagation by different -degrees of sterility, not strictly related to the facility of the first union -between their parents, seems to be a strange arrangement. - -The foregoing rules and facts, on the other hand, appear to me clearly to -indicate that the sterility both of first crosses and of hybrids is simply -incidental or dependent on unknown differences, chiefly in the reproductive -systems, of the species which are crossed. The differences being of so peculiar -and limited a nature, that, in reciprocal crosses between two species the male -sexual element of the one will often freely act on the female sexual element of -the other, but not in a reversed direction. It will be advisable to explain a -little more fully by an example what I mean by sterility being incidental on -other differences, and not a specially endowed quality. As the capacity of one -plant to be grafted or budded on another is so entirely unimportant for its -welfare in a state of nature, I presume that no one will suppose that this -capacity is a specially endowed quality, but will admit that it is incidental -on differences in the laws of growth of the two plants. We can sometimes see -the reason why one tree will not take on another, from differences in their -rate of growth, in the hardness of their wood, in the period of the flow or -nature of their sap, etc.; but in a multitude of cases we can assign no reason -whatever. Great diversity in the size of two plants, one being woody and the -other herbaceous, one being evergreen and the other deciduous, and adaptation -to widely different climates, does not always prevent the two grafting -together. As in hybridisation, so with grafting, the capacity is limited by -systematic affinity, for no one has been able to graft trees together belonging -to quite distinct families; and, on the other hand, closely allied species, and -varieties of the same species, can usually, but not invariably, be grafted with -ease. But this capacity, as in hybridisation, is by no means absolutely -governed by systematic affinity. Although many distinct genera within the same -family have been grafted together, in other cases species of the same genus -will not take on each other. The pear can be grafted far more readily on the -quince, which is ranked as a distinct genus, than on the apple, which is a -member of the same genus. Even different varieties of the pear take with -different degrees of facility on the quince; so do different varieties of the -apricot and peach on certain varieties of the plum. - -As Gärtner found that there was sometimes an innate difference in different -individuals of the same two species in crossing; so Sagaret believes this to be -the case with different individuals of the same two species in being grafted -together. As in reciprocal crosses, the facility of effecting an union is often -very far from equal, so it sometimes is in grafting; the common gooseberry, for -instance, cannot be grafted on the currant, whereas the currant will take, -though with difficulty, on the gooseberry. - -We have seen that the sterility of hybrids, which have their reproductive -organs in an imperfect condition, is a very different case from the difficulty -of uniting two pure species, which have their reproductive organs perfect; yet -these two distinct cases run to a certain extent parallel. Something analogous -occurs in grafting; for Thouin found that three species of Robinia, which -seeded freely on their own roots, and which could be grafted with no great -difficulty on another species, when thus grafted were rendered barren. On the -other hand, certain species of Sorbus, when grafted on other species, yielded -twice as much fruit as when on their own roots. We are reminded by this latter -fact of the extraordinary case of Hippeastrum, Lobelia, etc., which seeded much -more freely when fertilised with the pollen of distinct species, than when -self-fertilised with their own pollen. - -We thus see, that although there is a clear and fundamental difference between -the mere adhesion of grafted stocks, and the union of the male and female -elements in the act of reproduction, yet that there is a rude degree of -parallelism in the results of grafting and of crossing distinct species. And as -we must look at the curious and complex laws governing the facility with which -trees can be grafted on each other as incidental on unknown differences in -their vegetative systems, so I believe that the still more complex laws -governing the facility of first crosses, are incidental on unknown differences, -chiefly in their reproductive systems. These differences, in both cases, follow -to a certain extent, as might have been expected, systematic affinity, by which -every kind of resemblance and dissimilarity between organic beings is attempted -to be expressed. The facts by no means seem to me to indicate that the greater -or lesser difficulty of either grafting or crossing together various species -has been a special endowment; although in the case of crossing, the difficulty -is as important for the endurance and stability of specific forms, as in the -case of grafting it is unimportant for their welfare. - -Causes of the Sterility of first Crosses and of Hybrids.—We may now look a -little closer at the probable causes of the sterility of first crosses and of -hybrids. These two cases are fundamentally different, for, as just remarked, in -the union of two pure species the male and female sexual elements are perfect, -whereas in hybrids they are imperfect. Even in first crosses, the greater or -lesser difficulty in effecting a union apparently depends on several distinct -causes. There must sometimes be a physical impossibility in the male element -reaching the ovule, as would be the case with a plant having a pistil too long -for the pollen-tubes to reach the ovarium. It has also been observed that when -pollen of one species is placed on the stigma of a distantly allied species, -though the pollen-tubes protrude, they do not penetrate the stigmatic surface. -Again, the male element may reach the female element, but be incapable of -causing an embryo to be developed, as seems to have been the case with some of -Thuret’s experiments on Fuci. No explanation can be given of these facts, any -more than why certain trees cannot be grafted on others. Lastly, an embryo may -be developed, and then perish at an early period. This latter alternative has -not been sufficiently attended to; but I believe, from observations -communicated to me by Mr. Hewitt, who has had great experience in hybridising -gallinaceous birds, that the early death of the embryo is a very frequent cause -of sterility in first crosses. I was at first very unwilling to believe in this -view; as hybrids, when once born, are generally healthy and long-lived, as we -see in the case of the common mule. Hybrids, however, are differently -circumstanced before and after birth: when born and living in a country where -their two parents can live, they are generally placed under suitable conditions -of life. But a hybrid partakes of only half of the nature and constitution of -its mother, and therefore before birth, as long as it is nourished within its -mother’s womb or within the egg or seed produced by the mother, it may be -exposed to conditions in some degree unsuitable, and consequently be liable to -perish at an early period; more especially as all very young beings seem -eminently sensitive to injurious or unnatural conditions of life. +Kölreuter. To give an instance: Mirabilis jalappa can easily be +fertilised by the pollen of M. longiflora, and the hybrids thus produced +are sufficiently fertile; but Kölreuter tried more than two hundred +times, during eight following years, to fertilise reciprocally M. +longiflora with the pollen of M. jalappa, and utterly failed. Several +other equally striking cases could be given. Thuret has observed the +same fact with certain sea-weeds or Fuci. Gärtner, moreover, found that +this difference of facility in making reciprocal crosses is extremely +common in a lesser degree. He has observed it even between forms so +closely related (as Matthiola annua and glabra) that many botanists rank +them only as varieties. It is also a remarkable fact, that hybrids +raised from reciprocal crosses, though of course compounded of the very +same two species, the one species having first been used as the father +and then as the mother, generally differ in fertility in a small, and +occasionally in a high degree. + +Several other singular rules could be given from Gärtner: for instance, +some species have a remarkable power of crossing with other species; +other species of the same genus have a remarkable power of impressing +their likeness on their hybrid offspring; but these two powers do not at +all necessarily go together. There are certain hybrids which instead of +having, as is usual, an intermediate character between their two +parents, always closely resemble one of them; and such hybrids, though +externally so like one of their pure parent-species, are with rare +exceptions extremely sterile. So again amongst hybrids which are usually +intermediate in structure between their parents, exceptional and +abnormal individuals sometimes are born, which closely resemble one of +their pure parents; and these hybrids are almost always utterly sterile, +even when the other hybrids raised from seed from the same capsule have +a considerable degree of fertility. These facts show how completely +fertility in the hybrid is independent of its external resemblance to +either pure parent. + +Considering the several rules now given, which govern the fertility of +first crosses and of hybrids, we see that when forms, which must be +considered as good and distinct species, are united, their fertility +graduates from zero to perfect fertility, or even to fertility under +certain conditions in excess. That their fertility, besides being +eminently susceptible to favourable and unfavourable conditions, is +innately variable. That it is by no means always the same in degree in +the first cross and in the hybrids produced from this cross. That the +fertility of hybrids is not related to the degree in which they resemble +in external appearance either parent. And lastly, that the facility of +making a first cross between any two species is not always governed by +their systematic affinity or degree of resemblance to each other. This +latter statement is clearly proved by reciprocal crosses between the +same two species, for according as the one species or the other is used +as the father or the mother, there is generally some difference, and +occasionally the widest possible difference, in the facility of +effecting an union. The hybrids, moreover, produced from reciprocal +crosses often differ in fertility. + +Now do these complex and singular rules indicate that species have been +endowed with sterility simply to prevent their becoming confounded in +nature? I think not. For why should the sterility be so extremely +different in degree, when various species are crossed, all of which we +must suppose it would be equally important to keep from blending +together? Why should the degree of sterility be innately variable in the +individuals of the same species? Why should some species cross with +facility, and yet produce very sterile hybrids; and other species cross +with extreme difficulty, and yet produce fairly fertile hybrids? Why +should there often be so great a difference in the result of a +reciprocal cross between the same two species? Why, it may even be +asked, has the production of hybrids been permitted? to grant to species +the special power of producing hybrids, and then to stop their further +propagation by different degrees of sterility, not strictly related to +the facility of the first union between their parents, seems to be a +strange arrangement. + +The foregoing rules and facts, on the other hand, appear to me clearly +to indicate that the sterility both of first crosses and of hybrids is +simply incidental or dependent on unknown differences, chiefly in the +reproductive systems, of the species which are crossed. The differences +being of so peculiar and limited a nature, that, in reciprocal crosses +between two species the male sexual element of the one will often freely +act on the female sexual element of the other, but not in a reversed +direction. It will be advisable to explain a little more fully by an +example what I mean by sterility being incidental on other differences, +and not a specially endowed quality. As the capacity of one plant to be +grafted or budded on another is so entirely unimportant for its welfare +in a state of nature, I presume that no one will suppose that this +capacity is a specially endowed quality, but will admit that it is +incidental on differences in the laws of growth of the two plants. We +can sometimes see the reason why one tree will not take on another, from +differences in their rate of growth, in the hardness of their wood, in +the period of the flow or nature of their sap, etc.; but in a multitude +of cases we can assign no reason whatever. Great diversity in the size +of two plants, one being woody and the other herbaceous, one being +evergreen and the other deciduous, and adaptation to widely different +climates, does not always prevent the two grafting together. As in +hybridisation, so with grafting, the capacity is limited by systematic +affinity, for no one has been able to graft trees together belonging to +quite distinct families; and, on the other hand, closely allied species, +and varieties of the same species, can usually, but not invariably, be +grafted with ease. But this capacity, as in hybridisation, is by no +means absolutely governed by systematic affinity. Although many distinct +genera within the same family have been grafted together, in other cases +species of the same genus will not take on each other. The pear can be +grafted far more readily on the quince, which is ranked as a distinct +genus, than on the apple, which is a member of the same genus. Even +different varieties of the pear take with different degrees of facility +on the quince; so do different varieties of the apricot and peach on +certain varieties of the plum. + +As Gärtner found that there was sometimes an innate difference in +different individuals of the same two species in crossing; so Sagaret +believes this to be the case with different individuals of the same two +species in being grafted together. As in reciprocal crosses, the +facility of effecting an union is often very far from equal, so it +sometimes is in grafting; the common gooseberry, for instance, cannot be +grafted on the currant, whereas the currant will take, though with +difficulty, on the gooseberry. + +We have seen that the sterility of hybrids, which have their +reproductive organs in an imperfect condition, is a very different case +from the difficulty of uniting two pure species, which have their +reproductive organs perfect; yet these two distinct cases run to a +certain extent parallel. Something analogous occurs in grafting; for +Thouin found that three species of Robinia, which seeded freely on their +own roots, and which could be grafted with no great difficulty on +another species, when thus grafted were rendered barren. On the other +hand, certain species of Sorbus, when grafted on other species, yielded +twice as much fruit as when on their own roots. We are reminded by this +latter fact of the extraordinary case of Hippeastrum, Lobelia, etc., +which seeded much more freely when fertilised with the pollen of +distinct species, than when self-fertilised with their own pollen. + +We thus see, that although there is a clear and fundamental difference +between the mere adhesion of grafted stocks, and the union of the male +and female elements in the act of reproduction, yet that there is a rude +degree of parallelism in the results of grafting and of crossing +distinct species. And as we must look at the curious and complex laws +governing the facility with which trees can be grafted on each other as +incidental on unknown differences in their vegetative systems, so I +believe that the still more complex laws governing the facility of first +crosses, are incidental on unknown differences, chiefly in their +reproductive systems. These differences, in both cases, follow to a +certain extent, as might have been expected, systematic affinity, by +which every kind of resemblance and dissimilarity between organic beings +is attempted to be expressed. The facts by no means seem to me to +indicate that the greater or lesser difficulty of either grafting or +crossing together various species has been a special endowment; although +in the case of crossing, the difficulty is as important for the +endurance and stability of specific forms, as in the case of grafting it +is unimportant for their welfare. + +Causes of the Sterility of first Crosses and of Hybrids.—We may now look +a little closer at the probable causes of the sterility of first crosses +and of hybrids. These two cases are fundamentally different, for, as +just remarked, in the union of two pure species the male and female +sexual elements are perfect, whereas in hybrids they are imperfect. Even +in first crosses, the greater or lesser difficulty in effecting a union +apparently depends on several distinct causes. There must sometimes be a +physical impossibility in the male element reaching the ovule, as would +be the case with a plant having a pistil too long for the pollen-tubes +to reach the ovarium. It has also been observed that when pollen of one +species is placed on the stigma of a distantly allied species, though +the pollen-tubes protrude, they do not penetrate the stigmatic surface. +Again, the male element may reach the female element, but be incapable +of causing an embryo to be developed, as seems to have been the case +with some of Thuret’s experiments on Fuci. No explanation can be given +of these facts, any more than why certain trees cannot be grafted on +others. Lastly, an embryo may be developed, and then perish at an early +period. This latter alternative has not been sufficiently attended to; +but I believe, from observations communicated to me by Mr. Hewitt, who +has had great experience in hybridising gallinaceous birds, that the +early death of the embryo is a very frequent cause of sterility in first +crosses. I was at first very unwilling to believe in this view; as +hybrids, when once born, are generally healthy and long-lived, as we see +in the case of the common mule. Hybrids, however, are differently +circumstanced before and after birth: when born and living in a country +where their two parents can live, they are generally placed under +suitable conditions of life. But a hybrid partakes of only half of the +nature and constitution of its mother, and therefore before birth, as +long as it is nourished within its mother’s womb or within the egg or +seed produced by the mother, it may be exposed to conditions in some +degree unsuitable, and consequently be liable to perish at an early +period; more especially as all very young beings seem eminently +sensitive to injurious or unnatural conditions of life. In regard to the sterility of hybrids, in which the sexual elements are imperfectly developed, the case is very different. I have more than once -alluded to a large body of facts, which I have collected, showing that when -animals and plants are removed from their natural conditions, they are -extremely liable to have their reproductive systems seriously affected. This, -in fact, is the great bar to the domestication of animals. Between the -sterility thus superinduced and that of hybrids, there are many points of -similarity. In both cases the sterility is independent of general health, and -is often accompanied by excess of size or great luxuriance. In both cases, the -sterility occurs in various degrees; in both, the male element is the most -liable to be affected; but sometimes the female more than the male. In both, -the tendency goes to a certain extent with systematic affinity, for whole -groups of animals and plants are rendered impotent by the same unnatural -conditions; and whole groups of species tend to produce sterile hybrids. On the -other hand, one species in a group will sometimes resist great changes of -conditions with unimpaired fertility; and certain species in a group will -produce unusually fertile hybrids. No one can tell, till he tries, whether any -particular animal will breed under confinement or any plant seed freely under -culture; nor can he tell, till he tries, whether any two species of a genus -will produce more or less sterile hybrids. Lastly, when organic beings are -placed during several generations under conditions not natural to them, they -are extremely liable to vary, which is due, as I believe, to their reproductive -systems having been specially affected, though in a lesser degree than when -sterility ensues. So it is with hybrids, for hybrids in successive generations -are eminently liable to vary, as every experimentalist has observed. +alluded to a large body of facts, which I have collected, showing that +when animals and plants are removed from their natural conditions, they +are extremely liable to have their reproductive systems seriously +affected. This, in fact, is the great bar to the domestication of +animals. Between the sterility thus superinduced and that of hybrids, +there are many points of similarity. In both cases the sterility is +independent of general health, and is often accompanied by excess of +size or great luxuriance. In both cases, the sterility occurs in various +degrees; in both, the male element is the most liable to be affected; +but sometimes the female more than the male. In both, the tendency goes +to a certain extent with systematic affinity, for whole groups of +animals and plants are rendered impotent by the same unnatural +conditions; and whole groups of species tend to produce sterile hybrids. +On the other hand, one species in a group will sometimes resist great +changes of conditions with unimpaired fertility; and certain species in +a group will produce unusually fertile hybrids. No one can tell, till he +tries, whether any particular animal will breed under confinement or any +plant seed freely under culture; nor can he tell, till he tries, whether +any two species of a genus will produce more or less sterile hybrids. +Lastly, when organic beings are placed during several generations under +conditions not natural to them, they are extremely liable to vary, which +is due, as I believe, to their reproductive systems having been +specially affected, though in a lesser degree than when sterility +ensues. So it is with hybrids, for hybrids in successive generations are +eminently liable to vary, as every experimentalist has observed. Thus we see that when organic beings are placed under new and unnatural -conditions, and when hybrids are produced by the unnatural crossing of two -species, the reproductive system, independently of the general state of health, -is affected by sterility in a very similar manner. In the one case, the -conditions of life have been disturbed, though often in so slight a degree as -to be inappreciable by us; in the other case, or that of hybrids, the external -conditions have remained the same, but the organisation has been disturbed by -two different structures and constitutions having been blended into one. For it -is scarcely possible that two organisations should be compounded into one, -without some disturbance occurring in the development, or periodical action, or -mutual relation of the different parts and organs one to another, or to the -conditions of life. When hybrids are able to breed inter se, they transmit to -their offspring from generation to generation the same compounded organisation, -and hence we need not be surprised that their sterility, though in some degree -variable, rarely diminishes. - -It must, however, be confessed that we cannot understand, excepting on vague -hypotheses, several facts with respect to the sterility of hybrids; for -instance, the unequal fertility of hybrids produced from reciprocal crosses; or -the increased sterility in those hybrids which occasionally and exceptionally -resemble closely either pure parent. Nor do I pretend that the foregoing -remarks go to the root of the matter: no explanation is offered why an -organism, when placed under unnatural conditions, is rendered sterile. All that -I have attempted to show, is that in two cases, in some respects allied, -sterility is the common result,—in the one case from the conditions of life -having been disturbed, in the other case from the organisation having been -disturbed by two organisations having been compounded into one. - -It may seem fanciful, but I suspect that a similar parallelism extends to an -allied yet very different class of facts. It is an old and almost universal -belief, founded, I think, on a considerable body of evidence, that slight -changes in the conditions of life are beneficial to all living things. We see -this acted on by farmers and gardeners in their frequent exchanges of seed, -tubers, etc., from one soil or climate to another, and back again. During the -convalescence of animals, we plainly see that great benefit is derived from -almost any change in the habits of life. Again, both with plants and animals, -there is abundant evidence, that a cross between very distinct individuals of -the same species, that is between members of different strains or sub-breeds, -gives vigour and fertility to the offspring. I believe, indeed, from the facts -alluded to in our fourth chapter, that a certain amount of crossing is -indispensable even with hermaphrodites; and that close interbreeding continued -during several generations between the nearest relations, especially if these -be kept under the same conditions of life, always induces weakness and -sterility in the progeny. - -Hence it seems that, on the one hand, slight changes in the conditions of life -benefit all organic beings, and on the other hand, that slight crosses, that is -crosses between the males and females of the same species which have varied and -become slightly different, give vigour and fertility to the offspring. But we -have seen that greater changes, or changes of a particular nature, often render -organic beings in some degree sterile; and that greater crosses, that is -crosses between males and females which have become widely or specifically -different, produce hybrids which are generally sterile in some degree. I cannot -persuade myself that this parallelism is an accident or an illusion. Both -series of facts seem to be connected together by some common but unknown bond, +conditions, and when hybrids are produced by the unnatural crossing of +two species, the reproductive system, independently of the general state +of health, is affected by sterility in a very similar manner. In the one +case, the conditions of life have been disturbed, though often in so +slight a degree as to be inappreciable by us; in the other case, or that +of hybrids, the external conditions have remained the same, but the +organisation has been disturbed by two different structures and +constitutions having been blended into one. For it is scarcely possible +that two organisations should be compounded into one, without some +disturbance occurring in the development, or periodical action, or +mutual relation of the different parts and organs one to another, or to +the conditions of life. When hybrids are able to breed inter se, they +transmit to their offspring from generation to generation the same +compounded organisation, and hence we need not be surprised that their +sterility, though in some degree variable, rarely diminishes. + +It must, however, be confessed that we cannot understand, excepting on +vague hypotheses, several facts with respect to the sterility of +hybrids; for instance, the unequal fertility of hybrids produced from +reciprocal crosses; or the increased sterility in those hybrids which +occasionally and exceptionally resemble closely either pure parent. Nor +do I pretend that the foregoing remarks go to the root of the matter: no +explanation is offered why an organism, when placed under unnatural +conditions, is rendered sterile. All that I have attempted to show, is +that in two cases, in some respects allied, sterility is the common +result,—in the one case from the conditions of life having been +disturbed, in the other case from the organisation having been disturbed +by two organisations having been compounded into one. + +It may seem fanciful, but I suspect that a similar parallelism extends +to an allied yet very different class of facts. It is an old and almost +universal belief, founded, I think, on a considerable body of evidence, +that slight changes in the conditions of life are beneficial to all +living things. We see this acted on by farmers and gardeners in their +frequent exchanges of seed, tubers, etc., from one soil or climate to +another, and back again. During the convalescence of animals, we plainly +see that great benefit is derived from almost any change in the habits +of life. Again, both with plants and animals, there is abundant +evidence, that a cross between very distinct individuals of the same +species, that is between members of different strains or sub-breeds, +gives vigour and fertility to the offspring. I believe, indeed, from the +facts alluded to in our fourth chapter, that a certain amount of +crossing is indispensable even with hermaphrodites; and that close +interbreeding continued during several generations between the nearest +relations, especially if these be kept under the same conditions of +life, always induces weakness and sterility in the progeny. + +Hence it seems that, on the one hand, slight changes in the conditions +of life benefit all organic beings, and on the other hand, that slight +crosses, that is crosses between the males and females of the same +species which have varied and become slightly different, give vigour and +fertility to the offspring. But we have seen that greater changes, or +changes of a particular nature, often render organic beings in some +degree sterile; and that greater crosses, that is crosses between males +and females which have become widely or specifically different, produce +hybrids which are generally sterile in some degree. I cannot persuade +myself that this parallelism is an accident or an illusion. Both series +of facts seem to be connected together by some common but unknown bond, which is essentially related to the principle of life. -Fertility of Varieties when crossed, and of their Mongrel offspring.—It may be -urged, as a most forcible argument, that there must be some essential -distinction between species and varieties, and that there must be some error in -all the foregoing remarks, inasmuch as varieties, however much they may differ -from each other in external appearance, cross with perfect facility, and yield -perfectly fertile offspring. I fully admit that this is almost invariably the -case. But if we look to varieties produced under nature, we are immediately -involved in hopeless difficulties; for if two hitherto reputed varieties be -found in any degree sterile together, they are at once ranked by most -naturalists as species. For instance, the blue and red pimpernel, the primrose -and cowslip, which are considered by many of our best botanists as varieties, -are said by Gärtner not to be quite fertile when crossed, and he consequently -ranks them as undoubted species. If we thus argue in a circle, the fertility of -all varieties produced under nature will assuredly have to be granted. - -If we turn to varieties, produced, or supposed to have been produced, under -domestication, we are still involved in doubt. For when it is stated, for -instance, that the German Spitz dog unites more easily than other dogs with -foxes, or that certain South American indigenous domestic dogs do not readily -cross with European dogs, the explanation which will occur to everyone, and -probably the true one, is that these dogs have descended from several -aboriginally distinct species. Nevertheless the perfect fertility of so many -domestic varieties, differing widely from each other in appearance, for -instance of the pigeon or of the cabbage, is a remarkable fact; more especially -when we reflect how many species there are, which, though resembling each other -most closely, are utterly sterile when intercrossed. Several considerations, -however, render the fertility of domestic varieties less remarkable than at -first appears. It can, in the first place, be clearly shown that mere external -dissimilarity between two species does not determine their greater or lesser -degree of sterility when crossed; and we may apply the same rule to domestic -varieties. In the second place, some eminent naturalists believe that a long -course of domestication tends to eliminate sterility in the successive -generations of hybrids, which were at first only slightly sterile; and if this -be so, we surely ought not to expect to find sterility both appearing and -disappearing under nearly the same conditions of life. Lastly, and this seems -to me by far the most important consideration, new races of animals and plants -are produced under domestication by man’s methodical and unconscious power of -selection, for his own use and pleasure: he neither wishes to select, nor could -select, slight differences in the reproductive system, or other constitutional -differences correlated with the reproductive system. He supplies his several -varieties with the same food; treats them in nearly the same manner, and does -not wish to alter their general habits of life. Nature acts uniformly and -slowly during vast periods of time on the whole organisation, in any way which -may be for each creature’s own good; and thus she may, either directly, or more -probably indirectly, through correlation, modify the reproductive system in the -several descendants from any one species. Seeing this difference in the process -of selection, as carried on by man and nature, we need not be surprised at some -difference in the result. - -I have as yet spoken as if the varieties of the same species were invariably -fertile when intercrossed. But it seems to me impossible to resist the evidence -of the existence of a certain amount of sterility in the few following cases, -which I will briefly abstract. The evidence is at least as good as that from -which we believe in the sterility of a multitude of species. The evidence is, -also, derived from hostile witnesses, who in all other cases consider fertility -and sterility as safe criterions of specific distinction. Gärtner kept during -several years a dwarf kind of maize with yellow seeds, and a tall variety with -red seeds, growing near each other in his garden; and although these plants -have separated sexes, they never naturally crossed. He then fertilised thirteen -flowers of the one with the pollen of the other; but only a single head -produced any seed, and this one head produced only five grains. Manipulation in -this case could not have been injurious, as the plants have separated sexes. No -one, I believe, has suspected that these varieties of maize are distinct -species; and it is important to notice that the hybrid plants thus raised were -themselves perfectly fertile; so that even Gärtner did not venture to consider -the two varieties as specifically distinct. - -Girou de Buzareingues crossed three varieties of gourd, which like the maize -has separated sexes, and he asserts that their mutual fertilisation is by so -much the less easy as their differences are greater. How far these experiments -may be trusted, I know not; but the forms experimentised on, are ranked by -Sagaret, who mainly founds his classification by the test of infertility, as -varieties. - -The following case is far more remarkable, and seems at first quite incredible; -but it is the result of an astonishing number of experiments made during many -years on nine species of Verbascum, by so good an observer and so hostile a -witness, as Gärtner: namely, that yellow and white varieties of the same -species of Verbascum when intercrossed produce less seed, than do either -coloured varieties when fertilised with pollen from their own coloured flowers. -Moreover, he asserts that when yellow and white varieties of one species are -crossed with yellow and white varieties of a distinct species, more seed is -produced by the crosses between the same coloured flowers, than between those -which are differently coloured. Yet these varieties of Verbascum present no -other difference besides the mere colour of the flower; and one variety can +Fertility of Varieties when crossed, and of their Mongrel offspring.—It +may be urged, as a most forcible argument, that there must be some +essential distinction between species and varieties, and that there must +be some error in all the foregoing remarks, inasmuch as varieties, +however much they may differ from each other in external appearance, +cross with perfect facility, and yield perfectly fertile offspring. I +fully admit that this is almost invariably the case. But if we look to +varieties produced under nature, we are immediately involved in hopeless +difficulties; for if two hitherto reputed varieties be found in any +degree sterile together, they are at once ranked by most naturalists as +species. For instance, the blue and red pimpernel, the primrose and +cowslip, which are considered by many of our best botanists as +varieties, are said by Gärtner not to be quite fertile when crossed, and +he consequently ranks them as undoubted species. If we thus argue in a +circle, the fertility of all varieties produced under nature will +assuredly have to be granted. + +If we turn to varieties, produced, or supposed to have been produced, +under domestication, we are still involved in doubt. For when it is +stated, for instance, that the German Spitz dog unites more easily than +other dogs with foxes, or that certain South American indigenous +domestic dogs do not readily cross with European dogs, the explanation +which will occur to everyone, and probably the true one, is that these +dogs have descended from several aboriginally distinct species. +Nevertheless the perfect fertility of so many domestic varieties, +differing widely from each other in appearance, for instance of the +pigeon or of the cabbage, is a remarkable fact; more especially when we +reflect how many species there are, which, though resembling each other +most closely, are utterly sterile when intercrossed. Several +considerations, however, render the fertility of domestic varieties less +remarkable than at first appears. It can, in the first place, be clearly +shown that mere external dissimilarity between two species does not +determine their greater or lesser degree of sterility when crossed; and +we may apply the same rule to domestic varieties. In the second place, +some eminent naturalists believe that a long course of domestication +tends to eliminate sterility in the successive generations of hybrids, +which were at first only slightly sterile; and if this be so, we surely +ought not to expect to find sterility both appearing and disappearing +under nearly the same conditions of life. Lastly, and this seems to me +by far the most important consideration, new races of animals and plants +are produced under domestication by man’s methodical and unconscious +power of selection, for his own use and pleasure: he neither wishes to +select, nor could select, slight differences in the reproductive system, +or other constitutional differences correlated with the reproductive +system. He supplies his several varieties with the same food; treats +them in nearly the same manner, and does not wish to alter their general +habits of life. Nature acts uniformly and slowly during vast periods of +time on the whole organisation, in any way which may be for each +creature’s own good; and thus she may, either directly, or more probably +indirectly, through correlation, modify the reproductive system in the +several descendants from any one species. Seeing this difference in the +process of selection, as carried on by man and nature, we need not be +surprised at some difference in the result. + +I have as yet spoken as if the varieties of the same species were +invariably fertile when intercrossed. But it seems to me impossible to +resist the evidence of the existence of a certain amount of sterility in +the few following cases, which I will briefly abstract. The evidence is +at least as good as that from which we believe in the sterility of a +multitude of species. The evidence is, also, derived from hostile +witnesses, who in all other cases consider fertility and sterility as +safe criterions of specific distinction. Gärtner kept during several +years a dwarf kind of maize with yellow seeds, and a tall variety with +red seeds, growing near each other in his garden; and although these +plants have separated sexes, they never naturally crossed. He then +fertilised thirteen flowers of the one with the pollen of the other; but +only a single head produced any seed, and this one head produced only +five grains. Manipulation in this case could not have been injurious, as +the plants have separated sexes. No one, I believe, has suspected that +these varieties of maize are distinct species; and it is important to +notice that the hybrid plants thus raised were themselves perfectly +fertile; so that even Gärtner did not venture to consider the two +varieties as specifically distinct. + +Girou de Buzareingues crossed three varieties of gourd, which like the +maize has separated sexes, and he asserts that their mutual +fertilisation is by so much the less easy as their differences are +greater. How far these experiments may be trusted, I know not; but the +forms experimentised on, are ranked by Sagaret, who mainly founds his +classification by the test of infertility, as varieties. + +The following case is far more remarkable, and seems at first quite +incredible; but it is the result of an astonishing number of experiments +made during many years on nine species of Verbascum, by so good an +observer and so hostile a witness, as Gärtner: namely, that yellow and +white varieties of the same species of Verbascum when intercrossed +produce less seed, than do either coloured varieties when fertilised +with pollen from their own coloured flowers. Moreover, he asserts that +when yellow and white varieties of one species are crossed with yellow +and white varieties of a distinct species, more seed is produced by the +crosses between the same coloured flowers, than between those which are +differently coloured. Yet these varieties of Verbascum present no other +difference besides the mere colour of the flower; and one variety can sometimes be raised from the seed of the other. -From observations which I have made on certain varieties of hollyhock, I am -inclined to suspect that they present analogous facts. - -Kölreuter, whose accuracy has been confirmed by every subsequent observer, has -proved the remarkable fact, that one variety of the common tobacco is more -fertile, when crossed with a widely distinct species, than are the other -varieties. He experimentised on five forms, which are commonly reputed to be -varieties, and which he tested by the severest trial, namely, by reciprocal -crosses, and he found their mongrel offspring perfectly fertile. But one of -these five varieties, when used either as father or mother, and crossed with -the Nicotiana glutinosa, always yielded hybrids not so sterile as those which -were produced from the four other varieties when crossed with N. glutinosa. -Hence the reproductive system of this one variety must have been in some manner +From observations which I have made on certain varieties of hollyhock, I +am inclined to suspect that they present analogous facts. + +Kölreuter, whose accuracy has been confirmed by every subsequent +observer, has proved the remarkable fact, that one variety of the common +tobacco is more fertile, when crossed with a widely distinct species, +than are the other varieties. He experimentised on five forms, which are +commonly reputed to be varieties, and which he tested by the severest +trial, namely, by reciprocal crosses, and he found their mongrel +offspring perfectly fertile. But one of these five varieties, when used +either as father or mother, and crossed with the Nicotiana glutinosa, +always yielded hybrids not so sterile as those which were produced from +the four other varieties when crossed with N. glutinosa. Hence the +reproductive system of this one variety must have been in some manner and in some degree modified. -From these facts; from the great difficulty of ascertaining the infertility of -varieties in a state of nature, for a supposed variety if infertile in any -degree would generally be ranked as species; from man selecting only external -characters in the production of the most distinct domestic varieties, and from -not wishing or being able to produce recondite and functional differences in -the reproductive system; from these several considerations and facts, I do not -think that the very general fertility of varieties can be proved to be of -universal occurrence, or to form a fundamental distinction between varieties -and species. The general fertility of varieties does not seem to me sufficient -to overthrow the view which I have taken with respect to the very general, but -not invariable, sterility of first crosses and of hybrids, namely, that it is -not a special endowment, but is incidental on slowly acquired modifications, -more especially in the reproductive systems of the forms which are crossed. - -Hybrids and Mongrels compared, independently of their fertility.—Independently -of the question of fertility, the offspring of species when crossed and of -varieties when crossed may be compared in several other respects. Gärtner, -whose strong wish was to draw a marked line of distinction between species and -varieties, could find very few and, as it seems to me, quite unimportant -differences between the so-called hybrid offspring of species, and the -so-called mongrel offspring of varieties. And, on the other hand, they agree -most closely in very many important respects. - -I shall here discuss this subject with extreme brevity. The most important -distinction is, that in the first generation mongrels are more variable than -hybrids; but Gärtner admits that hybrids from species which have long been -cultivated are often variable in the first generation; and I have myself seen -striking instances of this fact. Gärtner further admits that hybrids between -very closely allied species are more variable than those from very distinct -species; and this shows that the difference in the degree of variability -graduates away. When mongrels and the more fertile hybrids are propagated for -several generations an extreme amount of variability in their offspring is -notorious; but some few cases both of hybrids and mongrels long retaining -uniformity of character could be given. The variability, however, in the -successive generations of mongrels is, perhaps, greater than in hybrids. - -This greater variability of mongrels than of hybrids does not seem to me at all -surprising. For the parents of mongrels are varieties, and mostly domestic -varieties (very few experiments having been tried on natural varieties), and -this implies in most cases that there has been recent variability; and -therefore we might expect that such variability would often continue and be -super-added to that arising from the mere act of crossing. The slight degree of -variability in hybrids from the first cross or in the first generation, in -contrast with their extreme variability in the succeeding generations, is a -curious fact and deserves attention. For it bears on and corroborates the view -which I have taken on the cause of ordinary variability; namely, that it is due -to the reproductive system being eminently sensitive to any change in the -conditions of life, being thus often rendered either impotent or at least -incapable of its proper function of producing offspring identical with the -parent-form. Now hybrids in the first generation are descended from species -(excluding those long cultivated) which have not had their reproductive systems -in any way affected, and they are not variable; but hybrids themselves have -their reproductive systems seriously affected, and their descendants are highly -variable. - -But to return to our comparison of mongrels and hybrids: Gärtner states that -mongrels are more liable than hybrids to revert to either parent-form; but -this, if it be true, is certainly only a difference in degree. Gärtner further -insists that when any two species, although most closely allied to each other, -are crossed with a third species, the hybrids are widely different from each -other; whereas if two very distinct varieties of one species are crossed with -another species, the hybrids do not differ much. But this conclusion, as far as -I can make out, is founded on a single experiment; and seems directly opposed -to the results of several experiments made by Kölreuter. - -These alone are the unimportant differences, which Gärtner is able to point -out, between hybrid and mongrel plants. On the other hand, the resemblance in -mongrels and in hybrids to their respective parents, more especially in hybrids -produced from nearly related species, follows according to Gärtner the same -laws. When two species are crossed, one has sometimes a prepotent power of -impressing its likeness on the hybrid; and so I believe it to be with varieties -of plants. With animals one variety certainly often has this prepotent power -over another variety. Hybrid plants produced from a reciprocal cross, generally -resemble each other closely; and so it is with mongrels from a reciprocal -cross. Both hybrids and mongrels can be reduced to either pure parent-form, by -repeated crosses in successive generations with either parent. - -These several remarks are apparently applicable to animals; but the subject is -here excessively complicated, partly owing to the existence of secondary sexual -characters; but more especially owing to prepotency in transmitting likeness -running more strongly in one sex than in the other, both when one species is -crossed with another, and when one variety is crossed with another variety. For -instance, I think those authors are right, who maintain that the ass has a -prepotent power over the horse, so that both the mule and the hinny more -resemble the ass than the horse; but that the prepotency runs more strongly in -the male-ass than in the female, so that the mule, which is the offspring of -the male-ass and mare, is more like an ass, than is the hinny, which is the -offspring of the female-ass and stallion. - -Much stress has been laid by some authors on the supposed fact, that mongrel -animals alone are born closely like one of their parents; but it can be shown -that this does sometimes occur with hybrids; yet I grant much less frequently -with hybrids than with mongrels. Looking to the cases which I have collected of -cross-bred animals closely resembling one parent, the resemblances seem chiefly -confined to characters almost monstrous in their nature, and which have -suddenly appeared—such as albinism, melanism, deficiency of tail or horns, or -additional fingers and toes; and do not relate to characters which have been -slowly acquired by selection. Consequently, sudden reversions to the perfect -character of either parent would be more likely to occur with mongrels, which -are descended from varieties often suddenly produced and semi-monstrous in -character, than with hybrids, which are descended from species slowly and -naturally produced. On the whole I entirely agree with Dr. Prosper Lucas, who, -after arranging an enormous body of facts with respect to animals, comes to the -conclusion, that the laws of resemblance of the child to its parents are the -same, whether the two parents differ much or little from each other, namely in -the union of individuals of the same variety, or of different varieties, or of +From these facts; from the great difficulty of ascertaining the +infertility of varieties in a state of nature, for a supposed variety if +infertile in any degree would generally be ranked as species; from man +selecting only external characters in the production of the most +distinct domestic varieties, and from not wishing or being able to +produce recondite and functional differences in the reproductive system; +from these several considerations and facts, I do not think that the +very general fertility of varieties can be proved to be of universal +occurrence, or to form a fundamental distinction between varieties and +species. The general fertility of varieties does not seem to me +sufficient to overthrow the view which I have taken with respect to the +very general, but not invariable, sterility of first crosses and of +hybrids, namely, that it is not a special endowment, but is incidental +on slowly acquired modifications, more especially in the reproductive +systems of the forms which are crossed. + +Hybrids and Mongrels compared, independently of their +fertility.—Independently of the question of fertility, the offspring of +species when crossed and of varieties when crossed may be compared in +several other respects. Gärtner, whose strong wish was to draw a marked +line of distinction between species and varieties, could find very few +and, as it seems to me, quite unimportant differences between the +so-called hybrid offspring of species, and the so-called mongrel +offspring of varieties. And, on the other hand, they agree most closely +in very many important respects. + +I shall here discuss this subject with extreme brevity. The most +important distinction is, that in the first generation mongrels are more +variable than hybrids; but Gärtner admits that hybrids from species +which have long been cultivated are often variable in the first +generation; and I have myself seen striking instances of this fact. +Gärtner further admits that hybrids between very closely allied species +are more variable than those from very distinct species; and this shows +that the difference in the degree of variability graduates away. When +mongrels and the more fertile hybrids are propagated for several +generations an extreme amount of variability in their offspring is +notorious; but some few cases both of hybrids and mongrels long +retaining uniformity of character could be given. The variability, +however, in the successive generations of mongrels is, perhaps, greater +than in hybrids. + +This greater variability of mongrels than of hybrids does not seem to me +at all surprising. For the parents of mongrels are varieties, and mostly +domestic varieties (very few experiments having been tried on natural +varieties), and this implies in most cases that there has been recent +variability; and therefore we might expect that such variability would +often continue and be super-added to that arising from the mere act of +crossing. The slight degree of variability in hybrids from the first +cross or in the first generation, in contrast with their extreme +variability in the succeeding generations, is a curious fact and +deserves attention. For it bears on and corroborates the view which I +have taken on the cause of ordinary variability; namely, that it is due +to the reproductive system being eminently sensitive to any change in +the conditions of life, being thus often rendered either impotent or at +least incapable of its proper function of producing offspring identical +with the parent-form. Now hybrids in the first generation are descended +from species (excluding those long cultivated) which have not had their +reproductive systems in any way affected, and they are not variable; but +hybrids themselves have their reproductive systems seriously affected, +and their descendants are highly variable. + +But to return to our comparison of mongrels and hybrids: Gärtner states +that mongrels are more liable than hybrids to revert to either +parent-form; but this, if it be true, is certainly only a difference in +degree. Gärtner further insists that when any two species, although most +closely allied to each other, are crossed with a third species, the +hybrids are widely different from each other; whereas if two very +distinct varieties of one species are crossed with another species, the +hybrids do not differ much. But this conclusion, as far as I can make +out, is founded on a single experiment; and seems directly opposed to +the results of several experiments made by Kölreuter. + +These alone are the unimportant differences, which Gärtner is able to +point out, between hybrid and mongrel plants. On the other hand, the +resemblance in mongrels and in hybrids to their respective parents, more +especially in hybrids produced from nearly related species, follows +according to Gärtner the same laws. When two species are crossed, one +has sometimes a prepotent power of impressing its likeness on the +hybrid; and so I believe it to be with varieties of plants. With animals +one variety certainly often has this prepotent power over another +variety. Hybrid plants produced from a reciprocal cross, generally +resemble each other closely; and so it is with mongrels from a +reciprocal cross. Both hybrids and mongrels can be reduced to either +pure parent-form, by repeated crosses in successive generations with +either parent. + +These several remarks are apparently applicable to animals; but the +subject is here excessively complicated, partly owing to the existence +of secondary sexual characters; but more especially owing to prepotency +in transmitting likeness running more strongly in one sex than in the +other, both when one species is crossed with another, and when one +variety is crossed with another variety. For instance, I think those +authors are right, who maintain that the ass has a prepotent power over +the horse, so that both the mule and the hinny more resemble the ass +than the horse; but that the prepotency runs more strongly in the +male-ass than in the female, so that the mule, which is the offspring of +the male-ass and mare, is more like an ass, than is the hinny, which is +the offspring of the female-ass and stallion. + +Much stress has been laid by some authors on the supposed fact, that +mongrel animals alone are born closely like one of their parents; but it +can be shown that this does sometimes occur with hybrids; yet I grant +much less frequently with hybrids than with mongrels. Looking to the +cases which I have collected of cross-bred animals closely resembling +one parent, the resemblances seem chiefly confined to characters almost +monstrous in their nature, and which have suddenly appeared—such as +albinism, melanism, deficiency of tail or horns, or additional fingers +and toes; and do not relate to characters which have been slowly +acquired by selection. Consequently, sudden reversions to the perfect +character of either parent would be more likely to occur with mongrels, +which are descended from varieties often suddenly produced and +semi-monstrous in character, than with hybrids, which are descended from +species slowly and naturally produced. On the whole I entirely agree +with Dr. Prosper Lucas, who, after arranging an enormous body of facts +with respect to animals, comes to the conclusion, that the laws of +resemblance of the child to its parents are the same, whether the two +parents differ much or little from each other, namely in the union of +individuals of the same variety, or of different varieties, or of distinct species. -Laying aside the question of fertility and sterility, in all other respects -there seems to be a general and close similarity in the offspring of crossed -species, and of crossed varieties. If we look at species as having been -specially created, and at varieties as having been produced by secondary laws, -this similarity would be an astonishing fact. But it harmonises perfectly with -the view that there is no essential distinction between species and varieties. - -Summary of Chapter.—First crosses between forms sufficiently distinct to be -ranked as species, and their hybrids, are very generally, but not universally, -sterile. The sterility is of all degrees, and is often so slight that the two -most careful experimentalists who have ever lived, have come to diametrically -opposite conclusions in ranking forms by this test. The sterility is innately -variable in individuals of the same species, and is eminently susceptible of -favourable and unfavourable conditions. The degree of sterility does not -strictly follow systematic affinity, but is governed by several curious and -complex laws. It is generally different, and sometimes widely different, in -reciprocal crosses between the same two species. It is not always equal in -degree in a first cross and in the hybrid produced from this cross. - -In the same manner as in grafting trees, the capacity of one species or variety -to take on another, is incidental on generally unknown differences in their -vegetative systems, so in crossing, the greater or less facility of one species -to unite with another, is incidental on unknown differences in their -reproductive systems. There is no more reason to think that species have been -specially endowed with various degrees of sterility to prevent them crossing -and blending in nature, than to think that trees have been specially endowed -with various and somewhat analogous degrees of difficulty in being grafted -together in order to prevent them becoming inarched in our forests. +Laying aside the question of fertility and sterility, in all other +respects there seems to be a general and close similarity in the +offspring of crossed species, and of crossed varieties. If we look at +species as having been specially created, and at varieties as having +been produced by secondary laws, this similarity would be an astonishing +fact. But it harmonises perfectly with the view that there is no +essential distinction between species and varieties. + +Summary of Chapter.—First crosses between forms sufficiently distinct to +be ranked as species, and their hybrids, are very generally, but not +universally, sterile. The sterility is of all degrees, and is often so +slight that the two most careful experimentalists who have ever lived, +have come to diametrically opposite conclusions in ranking forms by this +test. The sterility is innately variable in individuals of the same +species, and is eminently susceptible of favourable and unfavourable +conditions. The degree of sterility does not strictly follow systematic +affinity, but is governed by several curious and complex laws. It is +generally different, and sometimes widely different, in reciprocal +crosses between the same two species. It is not always equal in degree +in a first cross and in the hybrid produced from this cross. + +In the same manner as in grafting trees, the capacity of one species or +variety to take on another, is incidental on generally unknown +differences in their vegetative systems, so in crossing, the greater or +less facility of one species to unite with another, is incidental on +unknown differences in their reproductive systems. There is no more +reason to think that species have been specially endowed with various +degrees of sterility to prevent them crossing and blending in nature, +than to think that trees have been specially endowed with various and +somewhat analogous degrees of difficulty in being grafted together in +order to prevent them becoming inarched in our forests. The sterility of first crosses between pure species, which have their -reproductive systems perfect, seems to depend on several circumstances; in some -cases largely on the early death of the embryo. The sterility of hybrids, which -have their reproductive systems imperfect, and which have had this system and -their whole organisation disturbed by being compounded of two distinct species, -seems closely allied to that sterility which so frequently affects pure -species, when their natural conditions of life have been disturbed. This view -is supported by a parallelism of another kind;—namely, that the crossing of -forms only slightly different is favourable to the vigour and fertility of -their offspring; and that slight changes in the conditions of life are -apparently favourable to the vigour and fertility of all organic beings. It is -not surprising that the degree of difficulty in uniting two species, and the -degree of sterility of their hybrid-offspring should generally correspond, -though due to distinct causes; for both depend on the amount of difference of -some kind between the species which are crossed. Nor is it surprising that the -facility of effecting a first cross, the fertility of the hybrids produced, and -the capacity of being grafted together—though this latter capacity evidently -depends on widely different circumstances—should all run, to a certain extent, -parallel with the systematic affinity of the forms which are subjected to +reproductive systems perfect, seems to depend on several circumstances; +in some cases largely on the early death of the embryo. The sterility of +hybrids, which have their reproductive systems imperfect, and which have +had this system and their whole organisation disturbed by being +compounded of two distinct species, seems closely allied to that +sterility which so frequently affects pure species, when their natural +conditions of life have been disturbed. This view is supported by a +parallelism of another kind;—namely, that the crossing of forms only +slightly different is favourable to the vigour and fertility of their +offspring; and that slight changes in the conditions of life are +apparently favourable to the vigour and fertility of all organic beings. +It is not surprising that the degree of difficulty in uniting two +species, and the degree of sterility of their hybrid-offspring should +generally correspond, though due to distinct causes; for both depend on +the amount of difference of some kind between the species which are +crossed. Nor is it surprising that the facility of effecting a first +cross, the fertility of the hybrids produced, and the capacity of being +grafted together—though this latter capacity evidently depends on widely +different circumstances—should all run, to a certain extent, parallel +with the systematic affinity of the forms which are subjected to experiment; for systematic affinity attempts to express all kinds of resemblance between all species. -First crosses between forms known to be varieties, or sufficiently alike to be -considered as varieties, and their mongrel offspring, are very generally, but -not quite universally, fertile. Nor is this nearly general and perfect -fertility surprising, when we remember how liable we are to argue in a circle -with respect to varieties in a state of nature; and when we remember that the -greater number of varieties have been produced under domestication by the -selection of mere external differences, and not of differences in the -reproductive system. In all other respects, excluding fertility, there is a -close general resemblance between hybrids and mongrels. Finally, then, the -facts briefly given in this chapter do not seem to me opposed to, but even -rather to support the view, that there is no fundamental distinction between -species and varieties. - -CHAPTER IX. -ON THE IMPERFECTION OF THE GEOLOGICAL RECORD. - -On the absence of intermediate varieties at the present day. On the nature of -extinct intermediate varieties; on their number. On the vast lapse of time, as -inferred from the rate of deposition and of denudation. On the poorness of our -palæontological collections. On the intermittence of geological formations. On -the absence of intermediate varieties in any one formation. On the sudden -appearance of groups of species. On their sudden appearance in the lowest known -fossiliferous strata. - -In the sixth chapter I enumerated the chief objections which might be justly -urged against the views maintained in this volume. Most of them have now been -discussed. One, namely the distinctness of specific forms, and their not being -blended together by innumerable transitional links, is a very obvious -difficulty. I assigned reasons why such links do not commonly occur at the -present day, under the circumstances apparently most favourable for their -presence, namely on an extensive and continuous area with graduated physical -conditions. I endeavoured to show, that the life of each species depends in a -more important manner on the presence of other already defined organic forms, -than on climate; and, therefore, that the really governing conditions of life -do not graduate away quite insensibly like heat or moisture. I endeavoured, -also, to show that intermediate varieties, from existing in lesser numbers than -the forms which they connect, will generally be beaten out and exterminated -during the course of further modification and improvement. The main cause, -however, of innumerable intermediate links not now occurring everywhere -throughout nature depends on the very process of natural selection, through -which new varieties continually take the places of and exterminate their -parent-forms. But just in proportion as this process of extermination has acted -on an enormous scale, so must the number of intermediate varieties, which have -formerly existed on the earth, be truly enormous. Why then is not every -geological formation and every stratum full of such intermediate links? Geology -assuredly does not reveal any such finely graduated organic chain; and this, -perhaps, is the most obvious and gravest objection which can be urged against -my theory. The explanation lies, as I believe, in the extreme imperfection of -the geological record. - -In the first place it should always be borne in mind what sort of intermediate -forms must, on my theory, have formerly existed. I have found it difficult, -when looking at any two species, to avoid picturing to myself, forms directly -intermediate between them. But this is a wholly false view; we should always -look for forms intermediate between each species and a common but unknown -progenitor; and the progenitor will generally have differed in some respects -from all its modified descendants. To give a simple illustration: the fantail -and pouter pigeons have both descended from the rock-pigeon; if we possessed -all the intermediate varieties which have ever existed, we should have an -extremely close series between both and the rock-pigeon; but we should have no -varieties directly intermediate between the fantail and pouter; none, for -instance, combining a tail somewhat expanded with a crop somewhat enlarged, the -characteristic features of these two breeds. These two breeds, moreover, have -become so much modified, that if we had no historical or indirect evidence -regarding their origin, it would not have been possible to have determined from -a mere comparison of their structure with that of the rock-pigeon, whether they -had descended from this species or from some other allied species, such as C. -oenas. - -So with natural species, if we look to forms very distinct, for instance to the -horse and tapir, we have no reason to suppose that links ever existed directly -intermediate between them, but between each and an unknown common parent. The -common parent will have had in its whole organisation much general resemblance -to the tapir and to the horse; but in some points of structure may have -differed considerably from both, even perhaps more than they differ from each -other. Hence in all such cases, we should be unable to recognise the -parent-form of any two or more species, even if we closely compared the -structure of the parent with that of its modified descendants, unless at the -same time we had a nearly perfect chain of the intermediate links. - -It is just possible by my theory, that one of two living forms might have -descended from the other; for instance, a horse from a tapir; and in this case -direct intermediate links will have existed between them. But such a case would -imply that one form had remained for a very long period unaltered, whilst its -descendants had undergone a vast amount of change; and the principle of -competition between organism and organism, between child and parent, will -render this a very rare event; for in all cases the new and improved forms of -life will tend to supplant the old and unimproved forms. - -By the theory of natural selection all living species have been connected with -the parent-species of each genus, by differences not greater than we see -between the varieties of the same species at the present day; and these -parent-species, now generally extinct, have in their turn been similarly -connected with more ancient species; and so on backwards, always converging to -the common ancestor of each great class. So that the number of intermediate and -transitional links, between all living and extinct species, must have been -inconceivably great. But assuredly, if this theory be true, such have lived -upon this earth. - -On the lapse of Time.—Independently of our not finding fossil remains of such -infinitely numerous connecting links, it may be objected, that time will not -have sufficed for so great an amount of organic change, all changes having been -effected very slowly through natural selection. It is hardly possible for me -even to recall to the reader, who may not be a practical geologist, the facts -leading the mind feebly to comprehend the lapse of time. He who can read Sir -Charles Lyell’s grand work on the Principles of Geology, which the future -historian will recognise as having produced a revolution in natural science, -yet does not admit how incomprehensibly vast have been the past periods of -time, may at once close this volume. Not that it suffices to study the -Principles of Geology, or to read special treatises by different observers on -separate formations, and to mark how each author attempts to give an inadequate -idea of the duration of each formation or even each stratum. A man must for -years examine for himself great piles of superimposed strata, and watch the sea -at work grinding down old rocks and making fresh sediment, before he can hope -to comprehend anything of the lapse of time, the monuments of which we see -around us. - -It is good to wander along lines of sea-coast, when formed of moderately hard -rocks, and mark the process of degradation. The tides in most cases reach the -cliffs only for a short time twice a day, and the waves eat into them only when -they are charged with sand or pebbles; for there is reason to believe that pure -water can effect little or nothing in wearing away rock. At last the base of -the cliff is undermined, huge fragments fall down, and these remaining fixed, -have to be worn away, atom by atom, until reduced in size they can be rolled -about by the waves, and then are more quickly ground into pebbles, sand, or -mud. But how often do we see along the bases of retreating cliffs rounded -boulders, all thickly clothed by marine productions, showing how little they -are abraded and how seldom they are rolled about! Moreover, if we follow for a -few miles any line of rocky cliff, which is undergoing degradation, we find -that it is only here and there, along a short length or round a promontory, -that the cliffs are at the present time suffering. The appearance of the -surface and the vegetation show that elsewhere years have elapsed since the -waters washed their base. +First crosses between forms known to be varieties, or sufficiently alike +to be considered as varieties, and their mongrel offspring, are very +generally, but not quite universally, fertile. Nor is this nearly +general and perfect fertility surprising, when we remember how liable we +are to argue in a circle with respect to varieties in a state of nature; +and when we remember that the greater number of varieties have been +produced under domestication by the selection of mere external +differences, and not of differences in the reproductive system. In all +other respects, excluding fertility, there is a close general +resemblance between hybrids and mongrels. Finally, then, the facts +briefly given in this chapter do not seem to me opposed to, but even +rather to support the view, that there is no fundamental distinction +between species and varieties. + +CHAPTER IX. ON THE IMPERFECTION OF THE GEOLOGICAL RECORD. + +On the absence of intermediate varieties at the present day. On the +nature of extinct intermediate varieties; on their number. On the vast +lapse of time, as inferred from the rate of deposition and of +denudation. On the poorness of our palæontological collections. On the +intermittence of geological formations. On the absence of intermediate +varieties in any one formation. On the sudden appearance of groups of +species. On their sudden appearance in the lowest known fossiliferous +strata. + +In the sixth chapter I enumerated the chief objections which might be +justly urged against the views maintained in this volume. Most of them +have now been discussed. One, namely the distinctness of specific forms, +and their not being blended together by innumerable transitional links, +is a very obvious difficulty. I assigned reasons why such links do not +commonly occur at the present day, under the circumstances apparently +most favourable for their presence, namely on an extensive and +continuous area with graduated physical conditions. I endeavoured to +show, that the life of each species depends in a more important manner +on the presence of other already defined organic forms, than on climate; +and, therefore, that the really governing conditions of life do not +graduate away quite insensibly like heat or moisture. I endeavoured, +also, to show that intermediate varieties, from existing in lesser +numbers than the forms which they connect, will generally be beaten out +and exterminated during the course of further modification and +improvement. The main cause, however, of innumerable intermediate links +not now occurring everywhere throughout nature depends on the very +process of natural selection, through which new varieties continually +take the places of and exterminate their parent-forms. But just in +proportion as this process of extermination has acted on an enormous +scale, so must the number of intermediate varieties, which have formerly +existed on the earth, be truly enormous. Why then is not every +geological formation and every stratum full of such intermediate links? +Geology assuredly does not reveal any such finely graduated organic +chain; and this, perhaps, is the most obvious and gravest objection +which can be urged against my theory. The explanation lies, as I +believe, in the extreme imperfection of the geological record. + +In the first place it should always be borne in mind what sort of +intermediate forms must, on my theory, have formerly existed. I have +found it difficult, when looking at any two species, to avoid picturing +to myself, forms directly intermediate between them. But this is a +wholly false view; we should always look for forms intermediate between +each species and a common but unknown progenitor; and the progenitor +will generally have differed in some respects from all its modified +descendants. To give a simple illustration: the fantail and pouter +pigeons have both descended from the rock-pigeon; if we possessed all +the intermediate varieties which have ever existed, we should have an +extremely close series between both and the rock-pigeon; but we should +have no varieties directly intermediate between the fantail and pouter; +none, for instance, combining a tail somewhat expanded with a crop +somewhat enlarged, the characteristic features of these two breeds. +These two breeds, moreover, have become so much modified, that if we had +no historical or indirect evidence regarding their origin, it would not +have been possible to have determined from a mere comparison of their +structure with that of the rock-pigeon, whether they had descended from +this species or from some other allied species, such as C. oenas. + +So with natural species, if we look to forms very distinct, for instance +to the horse and tapir, we have no reason to suppose that links ever +existed directly intermediate between them, but between each and an +unknown common parent. The common parent will have had in its whole +organisation much general resemblance to the tapir and to the horse; but +in some points of structure may have differed considerably from both, +even perhaps more than they differ from each other. Hence in all such +cases, we should be unable to recognise the parent-form of any two or +more species, even if we closely compared the structure of the parent +with that of its modified descendants, unless at the same time we had a +nearly perfect chain of the intermediate links. + +It is just possible by my theory, that one of two living forms might +have descended from the other; for instance, a horse from a tapir; and +in this case direct intermediate links will have existed between them. +But such a case would imply that one form had remained for a very long +period unaltered, whilst its descendants had undergone a vast amount of +change; and the principle of competition between organism and organism, +between child and parent, will render this a very rare event; for in all +cases the new and improved forms of life will tend to supplant the old +and unimproved forms. + +By the theory of natural selection all living species have been +connected with the parent-species of each genus, by differences not +greater than we see between the varieties of the same species at the +present day; and these parent-species, now generally extinct, have in +their turn been similarly connected with more ancient species; and so on +backwards, always converging to the common ancestor of each great class. +So that the number of intermediate and transitional links, between all +living and extinct species, must have been inconceivably great. But +assuredly, if this theory be true, such have lived upon this earth. + +On the lapse of Time.—Independently of our not finding fossil remains of +such infinitely numerous connecting links, it may be objected, that time +will not have sufficed for so great an amount of organic change, all +changes having been effected very slowly through natural selection. It +is hardly possible for me even to recall to the reader, who may not be a +practical geologist, the facts leading the mind feebly to comprehend the +lapse of time. He who can read Sir Charles Lyell’s grand work on the +Principles of Geology, which the future historian will recognise as +having produced a revolution in natural science, yet does not admit how +incomprehensibly vast have been the past periods of time, may at once +close this volume. Not that it suffices to study the Principles of +Geology, or to read special treatises by different observers on separate +formations, and to mark how each author attempts to give an inadequate +idea of the duration of each formation or even each stratum. A man must +for years examine for himself great piles of superimposed strata, and +watch the sea at work grinding down old rocks and making fresh sediment, +before he can hope to comprehend anything of the lapse of time, the +monuments of which we see around us. + +It is good to wander along lines of sea-coast, when formed of moderately +hard rocks, and mark the process of degradation. The tides in most cases +reach the cliffs only for a short time twice a day, and the waves eat +into them only when they are charged with sand or pebbles; for there is +reason to believe that pure water can effect little or nothing in +wearing away rock. At last the base of the cliff is undermined, huge +fragments fall down, and these remaining fixed, have to be worn away, +atom by atom, until reduced in size they can be rolled about by the +waves, and then are more quickly ground into pebbles, sand, or mud. But +how often do we see along the bases of retreating cliffs rounded +boulders, all thickly clothed by marine productions, showing how little +they are abraded and how seldom they are rolled about! Moreover, if we +follow for a few miles any line of rocky cliff, which is undergoing +degradation, we find that it is only here and there, along a short +length or round a promontory, that the cliffs are at the present time +suffering. The appearance of the surface and the vegetation show that +elsewhere years have elapsed since the waters washed their base. He who most closely studies the action of the sea on our shores, will, I -believe, be most deeply impressed with the slowness with which rocky coasts are -worn away. The observations on this head by Hugh Miller, and by that excellent -observer Mr. Smith of Jordan Hill, are most impressive. With the mind thus -impressed, let any one examine beds of conglomerate many thousand feet in -thickness, which, though probably formed at a quicker rate than many other -deposits, yet, from being formed of worn and rounded pebbles, each of which -bears the stamp of time, are good to show how slowly the mass has been -accumulated. Let him remember Lyell’s profound remark, that the thickness and -extent of sedimentary formations are the result and measure of the degradation +believe, be most deeply impressed with the slowness with which rocky +coasts are worn away. The observations on this head by Hugh Miller, and +by that excellent observer Mr. Smith of Jordan Hill, are most +impressive. With the mind thus impressed, let any one examine beds of +conglomerate many thousand feet in thickness, which, though probably +formed at a quicker rate than many other deposits, yet, from being +formed of worn and rounded pebbles, each of which bears the stamp of +time, are good to show how slowly the mass has been accumulated. Let him +remember Lyell’s profound remark, that the thickness and extent of +sedimentary formations are the result and measure of the degradation which the earth’s crust has elsewhere suffered. And what an amount of -degradation is implied by the sedimentary deposits of many countries! Professor -Ramsay has given me the maximum thickness, in most cases from actual -measurement, in a few cases from estimate, of each formation in different parts -of Great Britain; and this is the result:— +degradation is implied by the sedimentary deposits of many countries! +Professor Ramsay has given me the maximum thickness, in most cases from +actual measurement, in a few cases from estimate, of each formation in +different parts of Great Britain; and this is the result:— - Feet + Feet - Palæozoic strata (not including igneous beds)...57,154. - Secondary strata................................13,190. - Tertiary strata..................................2,240. + Palæozoic strata (not including igneous beds)...57,154. Secondary + strata................................13,190. Tertiary + strata..................................2,240. —making altogether 72,584 feet; that is, very nearly thirteen and -three-quarters British miles. Some of these formations, which are represented -in England by thin beds, are thousands of feet in thickness on the Continent. -Moreover, between each successive formation, we have, in the opinion of most -geologists, enormously long blank periods. So that the lofty pile of -sedimentary rocks in Britain, gives but an inadequate idea of the time which -has elapsed during their accumulation; yet what time this must have consumed! -Good observers have estimated that sediment is deposited by the great -Mississippi river at the rate of only 600 feet in a hundred thousand years. -This estimate may be quite erroneous; yet, considering over what wide spaces -very fine sediment is transported by the currents of the sea, the process of -accumulation in any one area must be extremely slow. - -But the amount of denudation which the strata have in many places suffered, -independently of the rate of accumulation of the degraded matter, probably -offers the best evidence of the lapse of time. I remember having been much -struck with the evidence of denudation, when viewing volcanic islands, which -have been worn by the waves and pared all round into perpendicular cliffs of -one or two thousand feet in height; for the gentle slope of the lava-streams, -due to their formerly liquid state, showed at a glance how far the hard, rocky -beds had once extended into the open ocean. The same story is still more -plainly told by faults,—those great cracks along which the strata have been -upheaved on one side, or thrown down on the other, to the height or depth of -thousands of feet; for since the crust cracked, the surface of the land has -been so completely planed down by the action of the sea, that no trace of these -vast dislocations is externally visible. - -The Craven fault, for instance, extends for upwards of 30 miles, and along this -line the vertical displacement of the strata has varied from 600 to 3000 feet. -Professor Ramsay has published an account of a downthrow in Anglesea of 2300 -feet; and he informs me that he fully believes there is one in Merionethshire -of 12,000 feet; yet in these cases there is nothing on the surface to show such -prodigious movements; the pile of rocks on the one or other side having been -smoothly swept away. The consideration of these facts impresses my mind almost -in the same manner as does the vain endeavour to grapple with the idea of +three-quarters British miles. Some of these formations, which are +represented in England by thin beds, are thousands of feet in thickness +on the Continent. Moreover, between each successive formation, we have, +in the opinion of most geologists, enormously long blank periods. So +that the lofty pile of sedimentary rocks in Britain, gives but an +inadequate idea of the time which has elapsed during their accumulation; +yet what time this must have consumed! Good observers have estimated +that sediment is deposited by the great Mississippi river at the rate of +only 600 feet in a hundred thousand years. This estimate may be quite +erroneous; yet, considering over what wide spaces very fine sediment is +transported by the currents of the sea, the process of accumulation in +any one area must be extremely slow. + +But the amount of denudation which the strata have in many places +suffered, independently of the rate of accumulation of the degraded +matter, probably offers the best evidence of the lapse of time. I +remember having been much struck with the evidence of denudation, when +viewing volcanic islands, which have been worn by the waves and pared +all round into perpendicular cliffs of one or two thousand feet in +height; for the gentle slope of the lava-streams, due to their formerly +liquid state, showed at a glance how far the hard, rocky beds had once +extended into the open ocean. The same story is still more plainly told +by faults,—those great cracks along which the strata have been upheaved +on one side, or thrown down on the other, to the height or depth of +thousands of feet; for since the crust cracked, the surface of the land +has been so completely planed down by the action of the sea, that no +trace of these vast dislocations is externally visible. + +The Craven fault, for instance, extends for upwards of 30 miles, and +along this line the vertical displacement of the strata has varied from +600 to 3000 feet. Professor Ramsay has published an account of a +downthrow in Anglesea of 2300 feet; and he informs me that he fully +believes there is one in Merionethshire of 12,000 feet; yet in these +cases there is nothing on the surface to show such prodigious movements; +the pile of rocks on the one or other side having been smoothly swept +away. The consideration of these facts impresses my mind almost in the +same manner as does the vain endeavour to grapple with the idea of eternity. -I am tempted to give one other case, the well-known one of the denudation of -the Weald. Though it must be admitted that the denudation of the Weald has been -a mere trifle, in comparison with that which has removed masses of our -palæozoic strata, in parts ten thousand feet in thickness, as shown in -Professor Ramsay’s masterly memoir on this subject. Yet it is an admirable -lesson to stand on the North Downs and to look at the distant South Downs; for, -remembering that at no great distance to the west the northern and southern -escarpments meet and close, one can safely picture to oneself the great dome of -rocks which must have covered up the Weald within so limited a period as since -the latter part of the Chalk formation. The distance from the northern to the -southern Downs is about 22 miles, and the thickness of the several formations -is on an average about 1100 feet, as I am informed by Professor Ramsay. But if, -as some geologists suppose, a range of older rocks underlies the Weald, on the -flanks of which the overlying sedimentary deposits might have accumulated in -thinner masses than elsewhere, the above estimate would be erroneous; but this -source of doubt probably would not greatly affect the estimate as applied to -the western extremity of the district. If, then, we knew the rate at which the -sea commonly wears away a line of cliff of any given height, we could measure -the time requisite to have denuded the Weald. This, of course, cannot be done; -but we may, in order to form some crude notion on the subject, assume that the -sea would eat into cliffs 500 feet in height at the rate of one inch in a -century. This will at first appear much too small an allowance; but it is the -same as if we were to assume a cliff one yard in height to be eaten back along -a whole line of coast at the rate of one yard in nearly every twenty-two years. -I doubt whether any rock, even as soft as chalk, would yield at this rate -excepting on the most exposed coasts; though no doubt the degradation of a -lofty cliff would be more rapid from the breakage of the fallen fragments. On -the other hand, I do not believe that any line of coast, ten or twenty miles in -length, ever suffers degradation at the same time along its whole indented -length; and we must remember that almost all strata contain harder layers or -nodules, which from long resisting attrition form a breakwater at the base. -Hence, under ordinary circumstances, I conclude that for a cliff 500 feet in -height, a denudation of one inch per century for the whole length would be an -ample allowance. At this rate, on the above data, the denudation of the Weald -must have required 306,662,400 years; or say three hundred million years. +I am tempted to give one other case, the well-known one of the +denudation of the Weald. Though it must be admitted that the denudation +of the Weald has been a mere trifle, in comparison with that which has +removed masses of our palæozoic strata, in parts ten thousand feet in +thickness, as shown in Professor Ramsay’s masterly memoir on this +subject. Yet it is an admirable lesson to stand on the North Downs and +to look at the distant South Downs; for, remembering that at no great +distance to the west the northern and southern escarpments meet and +close, one can safely picture to oneself the great dome of rocks which +must have covered up the Weald within so limited a period as since the +latter part of the Chalk formation. The distance from the northern to +the southern Downs is about 22 miles, and the thickness of the several +formations is on an average about 1100 feet, as I am informed by +Professor Ramsay. But if, as some geologists suppose, a range of older +rocks underlies the Weald, on the flanks of which the overlying +sedimentary deposits might have accumulated in thinner masses than +elsewhere, the above estimate would be erroneous; but this source of +doubt probably would not greatly affect the estimate as applied to the +western extremity of the district. If, then, we knew the rate at which +the sea commonly wears away a line of cliff of any given height, we +could measure the time requisite to have denuded the Weald. This, of +course, cannot be done; but we may, in order to form some crude notion +on the subject, assume that the sea would eat into cliffs 500 feet in +height at the rate of one inch in a century. This will at first appear +much too small an allowance; but it is the same as if we were to assume +a cliff one yard in height to be eaten back along a whole line of coast +at the rate of one yard in nearly every twenty-two years. I doubt +whether any rock, even as soft as chalk, would yield at this rate +excepting on the most exposed coasts; though no doubt the degradation of +a lofty cliff would be more rapid from the breakage of the fallen +fragments. On the other hand, I do not believe that any line of coast, +ten or twenty miles in length, ever suffers degradation at the same time +along its whole indented length; and we must remember that almost all +strata contain harder layers or nodules, which from long resisting +attrition form a breakwater at the base. Hence, under ordinary +circumstances, I conclude that for a cliff 500 feet in height, a +denudation of one inch per century for the whole length would be an +ample allowance. At this rate, on the above data, the denudation of the +Weald must have required 306,662,400 years; or say three hundred million +years. The action of fresh water on the gently inclined Wealden district, when -upraised, could hardly have been great, but it would somewhat reduce the above -estimate. On the other hand, during oscillations of level, which we know this -area has undergone, the surface may have existed for millions of years as land, -and thus have escaped the action of the sea: when deeply submerged for perhaps -equally long periods, it would, likewise, have escaped the action of the -coast-waves. So that in all probability a far longer period than 300 million -years has elapsed since the latter part of the Secondary period. - -I have made these few remarks because it is highly important for us to gain -some notion, however imperfect, of the lapse of years. During each of these -years, over the whole world, the land and the water has been peopled by hosts -of living forms. What an infinite number of generations, which the mind cannot -grasp, must have succeeded each other in the long roll of years! Now turn to -our richest geological museums, and what a paltry display we behold! - -On the poorness of our Palæontological collections.—That our palæontological -collections are very imperfect, is admitted by every one. The remark of that -admirable palæontologist, the late Edward Forbes, should not be forgotten, -namely, that numbers of our fossil species are known and named from single and -often broken specimens, or from a few specimens collected on some one spot. -Only a small portion of the surface of the earth has been geologically -explored, and no part with sufficient care, as the important discoveries made -every year in Europe prove. No organism wholly soft can be preserved. Shells -and bones will decay and disappear when left on the bottom of the sea, where +upraised, could hardly have been great, but it would somewhat reduce the +above estimate. On the other hand, during oscillations of level, which +we know this area has undergone, the surface may have existed for +millions of years as land, and thus have escaped the action of the sea: +when deeply submerged for perhaps equally long periods, it would, +likewise, have escaped the action of the coast-waves. So that in all +probability a far longer period than 300 million years has elapsed since +the latter part of the Secondary period. + +I have made these few remarks because it is highly important for us to +gain some notion, however imperfect, of the lapse of years. During each +of these years, over the whole world, the land and the water has been +peopled by hosts of living forms. What an infinite number of +generations, which the mind cannot grasp, must have succeeded each other +in the long roll of years! Now turn to our richest geological museums, +and what a paltry display we behold! + +On the poorness of our Palæontological collections.—That our +palæontological collections are very imperfect, is admitted by every +one. The remark of that admirable palæontologist, the late Edward +Forbes, should not be forgotten, namely, that numbers of our fossil +species are known and named from single and often broken specimens, or +from a few specimens collected on some one spot. Only a small portion +of the surface of the earth has been geologically explored, and no part +with sufficient care, as the important discoveries made every year in +Europe prove. No organism wholly soft can be preserved. Shells and bones +will decay and disappear when left on the bottom of the sea, where sediment is not accumulating. I believe we are continually taking a most -erroneous view, when we tacitly admit to ourselves that sediment is being -deposited over nearly the whole bed of the sea, at a rate sufficiently quick to -embed and preserve fossil remains. Throughout an enormously large proportion of -the ocean, the bright blue tint of the water bespeaks its purity. The many -cases on record of a formation conformably covered, after an enormous interval -of time, by another and later formation, without the underlying bed having -suffered in the interval any wear and tear, seem explicable only on the view of -the bottom of the sea not rarely lying for ages in an unaltered condition. The -remains which do become embedded, if in sand or gravel, will when the beds are -upraised generally be dissolved by the percolation of rain-water. I suspect -that but few of the very many animals which live on the beach between high and -low watermark are preserved. For instance, the several species of the -Chthamalinæ (a sub-family of sessile cirripedes) coat the rocks all over the -world in infinite numbers: they are all strictly littoral, with the exception -of a single Mediterranean species, which inhabits deep water and has been found -fossil in Sicily, whereas not one other species has hitherto been found in any -tertiary formation: yet it is now known that the genus Chthamalus existed -during the chalk period. The molluscan genus Chiton offers a partially +erroneous view, when we tacitly admit to ourselves that sediment is +being deposited over nearly the whole bed of the sea, at a rate +sufficiently quick to embed and preserve fossil remains. Throughout an +enormously large proportion of the ocean, the bright blue tint of the +water bespeaks its purity. The many cases on record of a formation +conformably covered, after an enormous interval of time, by another and +later formation, without the underlying bed having suffered in the +interval any wear and tear, seem explicable only on the view of the +bottom of the sea not rarely lying for ages in an unaltered condition. +The remains which do become embedded, if in sand or gravel, will when +the beds are upraised generally be dissolved by the percolation of +rain-water. I suspect that but few of the very many animals which live +on the beach between high and low watermark are preserved. For instance, +the several species of the Chthamalinæ (a sub-family of sessile +cirripedes) coat the rocks all over the world in infinite numbers: they +are all strictly littoral, with the exception of a single Mediterranean +species, which inhabits deep water and has been found fossil in Sicily, +whereas not one other species has hitherto been found in any tertiary +formation: yet it is now known that the genus Chthamalus existed during +the chalk period. The molluscan genus Chiton offers a partially analogous case. -With respect to the terrestrial productions which lived during the Secondary -and Palæozoic periods, it is superfluous to state that our evidence from fossil -remains is fragmentary in an extreme degree. For instance, not a land shell is -known belonging to either of these vast periods, with one exception discovered -by Sir C. Lyell in the carboniferous strata of North America. In regard to -mammiferous remains, a single glance at the historical table published in the -Supplement to Lyell’s Manual, will bring home the truth, how accidental and -rare is their preservation, far better than pages of detail. Nor is their -rarity surprising, when we remember how large a proportion of the bones of +With respect to the terrestrial productions which lived during the +Secondary and Palæozoic periods, it is superfluous to state that our +evidence from fossil remains is fragmentary in an extreme degree. For +instance, not a land shell is known belonging to either of these vast +periods, with one exception discovered by Sir C. Lyell in the +carboniferous strata of North America. In regard to mammiferous remains, +a single glance at the historical table published in the Supplement to +Lyell’s Manual, will bring home the truth, how accidental and rare is +their preservation, far better than pages of detail. Nor is their rarity +surprising, when we remember how large a proportion of the bones of tertiary mammals have been discovered either in caves or in lacustrine -deposits; and that not a cave or true lacustrine bed is known belonging to the -age of our secondary or palæozoic formations. - -But the imperfection in the geological record mainly results from another and -more important cause than any of the foregoing; namely, from the several -formations being separated from each other by wide intervals of time. When we -see the formations tabulated in written works, or when we follow them in -nature, it is difficult to avoid believing that they are closely consecutive. -But we know, for instance, from Sir R. Murchison’s great work on Russia, what -wide gaps there are in that country between the superimposed formations; so it -is in North America, and in many other parts of the world. The most skilful -geologist, if his attention had been exclusively confined to these large -territories, would never have suspected that during the periods which were -blank and barren in his own country, great piles of sediment, charged with new -and peculiar forms of life, had elsewhere been accumulated. And if in each -separate territory, hardly any idea can be formed of the length of time which -has elapsed between the consecutive formations, we may infer that this could -nowhere be ascertained. The frequent and great changes in the mineralogical -composition of consecutive formations, generally implying great changes in the -geography of the surrounding lands, whence the sediment has been derived, -accords with the belief of vast intervals of time having elapsed between each -formation. - -But we can, I think, see why the geological formations of each region are -almost invariably intermittent; that is, have not followed each other in close -sequence. Scarcely any fact struck me more when examining many hundred miles of -the South American coasts, which have been upraised several hundred feet within -the recent period, than the absence of any recent deposits sufficiently -extensive to last for even a short geological period. Along the whole west -coast, which is inhabited by a peculiar marine fauna, tertiary beds are so -scantily developed, that no record of several successive and peculiar marine -faunas will probably be preserved to a distant age. A little reflection will -explain why along the rising coast of the western side of South America, no -extensive formations with recent or tertiary remains can anywhere be found, -though the supply of sediment must for ages have been great, from the enormous -degradation of the coast-rocks and from muddy streams entering the sea. The -explanation, no doubt, is, that the littoral and sub-littoral deposits are -continually worn away, as soon as they are brought up by the slow and gradual -rising of the land within the grinding action of the coast-waves. - -We may, I think, safely conclude that sediment must be accumulated in extremely -thick, solid, or extensive masses, in order to withstand the incessant action -of the waves, when first upraised and during subsequent oscillations of level. -Such thick and extensive accumulations of sediment may be formed in two ways; -either, in profound depths of the sea, in which case, judging from the -researches of E. Forbes, we may conclude that the bottom will be inhabited by -extremely few animals, and the mass when upraised will give a most imperfect -record of the forms of life which then existed; or, sediment may be accumulated -to any thickness and extent over a shallow bottom, if it continue slowly to -subside. In this latter case, as long as the rate of subsidence and supply of -sediment nearly balance each other, the sea will remain shallow and favourable -for life, and thus a fossiliferous formation thick enough, when upraised, to -resist any amount of degradation, may be formed. - -I am convinced that all our ancient formations, which are rich in fossils, have -thus been formed during subsidence. Since publishing my views on this subject -in 1845, I have watched the progress of Geology, and have been surprised to -note how author after author, in treating of this or that great formation, has -come to the conclusion that it was accumulated during subsidence. I may add, -that the only ancient tertiary formation on the west coast of South America, -which has been bulky enough to resist such degradation as it has as yet -suffered, but which will hardly last to a distant geological age, was certainly -deposited during a downward oscillation of level, and thus gained considerable +deposits; and that not a cave or true lacustrine bed is known belonging +to the age of our secondary or palæozoic formations. + +But the imperfection in the geological record mainly results from +another and more important cause than any of the foregoing; namely, from +the several formations being separated from each other by wide intervals +of time. When we see the formations tabulated in written works, or when +we follow them in nature, it is difficult to avoid believing that they +are closely consecutive. But we know, for instance, from Sir R. +Murchison’s great work on Russia, what wide gaps there are in that +country between the superimposed formations; so it is in North America, +and in many other parts of the world. The most skilful geologist, if his +attention had been exclusively confined to these large territories, +would never have suspected that during the periods which were blank and +barren in his own country, great piles of sediment, charged with new and +peculiar forms of life, had elsewhere been accumulated. And if in each +separate territory, hardly any idea can be formed of the length of time +which has elapsed between the consecutive formations, we may infer that +this could nowhere be ascertained. The frequent and great changes in the +mineralogical composition of consecutive formations, generally implying +great changes in the geography of the surrounding lands, whence the +sediment has been derived, accords with the belief of vast intervals of +time having elapsed between each formation. + +But we can, I think, see why the geological formations of each region +are almost invariably intermittent; that is, have not followed each +other in close sequence. Scarcely any fact struck me more when examining +many hundred miles of the South American coasts, which have been +upraised several hundred feet within the recent period, than the absence +of any recent deposits sufficiently extensive to last for even a short +geological period. Along the whole west coast, which is inhabited by a +peculiar marine fauna, tertiary beds are so scantily developed, that no +record of several successive and peculiar marine faunas will probably be +preserved to a distant age. A little reflection will explain why along +the rising coast of the western side of South America, no extensive +formations with recent or tertiary remains can anywhere be found, though +the supply of sediment must for ages have been great, from the enormous +degradation of the coast-rocks and from muddy streams entering the sea. +The explanation, no doubt, is, that the littoral and sub-littoral +deposits are continually worn away, as soon as they are brought up by +the slow and gradual rising of the land within the grinding action of +the coast-waves. + +We may, I think, safely conclude that sediment must be accumulated in +extremely thick, solid, or extensive masses, in order to withstand the +incessant action of the waves, when first upraised and during subsequent +oscillations of level. Such thick and extensive accumulations of +sediment may be formed in two ways; either, in profound depths of the +sea, in which case, judging from the researches of E. Forbes, we may +conclude that the bottom will be inhabited by extremely few animals, and +the mass when upraised will give a most imperfect record of the forms of +life which then existed; or, sediment may be accumulated to any +thickness and extent over a shallow bottom, if it continue slowly to +subside. In this latter case, as long as the rate of subsidence and +supply of sediment nearly balance each other, the sea will remain +shallow and favourable for life, and thus a fossiliferous formation +thick enough, when upraised, to resist any amount of degradation, may be +formed. + +I am convinced that all our ancient formations, which are rich in +fossils, have thus been formed during subsidence. Since publishing my +views on this subject in 1845, I have watched the progress of Geology, +and have been surprised to note how author after author, in treating of +this or that great formation, has come to the conclusion that it was +accumulated during subsidence. I may add, that the only ancient tertiary +formation on the west coast of South America, which has been bulky +enough to resist such degradation as it has as yet suffered, but which +will hardly last to a distant geological age, was certainly deposited +during a downward oscillation of level, and thus gained considerable thickness. -All geological facts tell us plainly that each area has undergone numerous slow -oscillations of level, and apparently these oscillations have affected wide -spaces. Consequently formations rich in fossils and sufficiently thick and -extensive to resist subsequent degradation, may have been formed over wide -spaces during periods of subsidence, but only where the supply of sediment was -sufficient to keep the sea shallow and to embed and preserve the remains before -they had time to decay. On the other hand, as long as the bed of the sea -remained stationary, thick deposits could not have been accumulated in the -shallow parts, which are the most favourable to life. Still less could this -have happened during the alternate periods of elevation; or, to speak more -accurately, the beds which were then accumulated will have been destroyed by -being upraised and brought within the limits of the coast-action. - -Thus the geological record will almost necessarily be rendered intermittent. I -feel much confidence in the truth of these views, for they are in strict -accordance with the general principles inculcated by Sir C. Lyell; and E. -Forbes independently arrived at a similar conclusion. - -One remark is here worth a passing notice. During periods of elevation the area -of the land and of the adjoining shoal parts of the sea will be increased, and -new stations will often be formed;—all circumstances most favourable, as -previously explained, for the formation of new varieties and species; but -during such periods there will generally be a blank in the geological record. -On the other hand, during subsidence, the inhabited area and number of -inhabitants will decrease (excepting the productions on the shores of a -continent when first broken up into an archipelago), and consequently during -subsidence, though there will be much extinction, fewer new varieties or -species will be formed; and it is during these very periods of subsidence, that -our great deposits rich in fossils have been accumulated. Nature may almost be -said to have guarded against the frequent discovery of her transitional or -linking forms. - -From the foregoing considerations it cannot be doubted that the geological -record, viewed as a whole, is extremely imperfect; but if we confine our -attention to any one formation, it becomes more difficult to understand, why we -do not therein find closely graduated varieties between the allied species -which lived at its commencement and at its close. Some cases are on record of -the same species presenting distinct varieties in the upper and lower parts of -the same formation, but, as they are rare, they may be here passed over. -Although each formation has indisputably required a vast number of years for -its deposition, I can see several reasons why each should not include a -graduated series of links between the species which then lived; but I can by no -means pretend to assign due proportional weight to the following +All geological facts tell us plainly that each area has undergone +numerous slow oscillations of level, and apparently these oscillations +have affected wide spaces. Consequently formations rich in fossils and +sufficiently thick and extensive to resist subsequent degradation, may +have been formed over wide spaces during periods of subsidence, but only +where the supply of sediment was sufficient to keep the sea shallow and +to embed and preserve the remains before they had time to decay. On the +other hand, as long as the bed of the sea remained stationary, thick +deposits could not have been accumulated in the shallow parts, which are +the most favourable to life. Still less could this have happened during +the alternate periods of elevation; or, to speak more accurately, the +beds which were then accumulated will have been destroyed by being +upraised and brought within the limits of the coast-action. + +Thus the geological record will almost necessarily be rendered +intermittent. I feel much confidence in the truth of these views, for +they are in strict accordance with the general principles inculcated by +Sir C. Lyell; and E. Forbes independently arrived at a similar +conclusion. + +One remark is here worth a passing notice. During periods of elevation +the area of the land and of the adjoining shoal parts of the sea will be +increased, and new stations will often be formed;—all circumstances most +favourable, as previously explained, for the formation of new varieties +and species; but during such periods there will generally be a blank in +the geological record. On the other hand, during subsidence, the +inhabited area and number of inhabitants will decrease (excepting the +productions on the shores of a continent when first broken up into an +archipelago), and consequently during subsidence, though there will be +much extinction, fewer new varieties or species will be formed; and it +is during these very periods of subsidence, that our great deposits rich +in fossils have been accumulated. Nature may almost be said to have +guarded against the frequent discovery of her transitional or linking +forms. + +From the foregoing considerations it cannot be doubted that the +geological record, viewed as a whole, is extremely imperfect; but if we +confine our attention to any one formation, it becomes more difficult to +understand, why we do not therein find closely graduated varieties +between the allied species which lived at its commencement and at its +close. Some cases are on record of the same species presenting distinct +varieties in the upper and lower parts of the same formation, but, as +they are rare, they may be here passed over. Although each formation +has indisputably required a vast number of years for its deposition, I +can see several reasons why each should not include a graduated series +of links between the species which then lived; but I can by no means +pretend to assign due proportional weight to the following considerations. -Although each formation may mark a very long lapse of years, each perhaps is -short compared with the period requisite to change one species into another. I -am aware that two palæontologists, whose opinions are worthy of much deference, -namely Bronn and Woodward, have concluded that the average duration of each -formation is twice or thrice as long as the average duration of specific forms. -But insuperable difficulties, as it seems to me, prevent us coming to any just -conclusion on this head. When we see a species first appearing in the middle of -any formation, it would be rash in the extreme to infer that it had not -elsewhere previously existed. So again when we find a species disappearing -before the uppermost layers have been deposited, it would be equally rash to -suppose that it then became wholly extinct. We forget how small the area of -Europe is compared with the rest of the world; nor have the several stages of -the same formation throughout Europe been correlated with perfect accuracy. +Although each formation may mark a very long lapse of years, each +perhaps is short compared with the period requisite to change one +species into another. I am aware that two palæontologists, whose +opinions are worthy of much deference, namely Bronn and Woodward, have +concluded that the average duration of each formation is twice or thrice +as long as the average duration of specific forms. But insuperable +difficulties, as it seems to me, prevent us coming to any just +conclusion on this head. When we see a species first appearing in the +middle of any formation, it would be rash in the extreme to infer that +it had not elsewhere previously existed. So again when we find a species +disappearing before the uppermost layers have been deposited, it would +be equally rash to suppose that it then became wholly extinct. We forget +how small the area of Europe is compared with the rest of the world; nor +have the several stages of the same formation throughout Europe been +correlated with perfect accuracy. With marine animals of all kinds, we may safely infer a large amount of -migration during climatal and other changes; and when we see a species first -appearing in any formation, the probability is that it only then first -immigrated into that area. It is well known, for instance, that several species -appeared somewhat earlier in the palæozoic beds of North America than in those -of Europe; time having apparently been required for their migration from the -American to the European seas. In examining the latest deposits of various -quarters of the world, it has everywhere been noted, that some few still -existing species are common in the deposit, but have become extinct in the -immediately surrounding sea; or, conversely, that some are now abundant in the -neighbouring sea, but are rare or absent in this particular deposit. It is an -excellent lesson to reflect on the ascertained amount of migration of the -inhabitants of Europe during the Glacial period, which forms only a part of one -whole geological period; and likewise to reflect on the great changes of level, -on the inordinately great change of climate, on the prodigious lapse of time, -all included within this same glacial period. Yet it may be doubted whether in -any quarter of the world, sedimentary deposits, including fossil remains, have -gone on accumulating within the same area during the whole of this period. It -is not, for instance, probable that sediment was deposited during the whole of -the glacial period near the mouth of the Mississippi, within that limit of -depth at which marine animals can flourish; for we know what vast geographical -changes occurred in other parts of America during this space of time. When such -beds as were deposited in shallow water near the mouth of the Mississippi -during some part of the glacial period shall have been upraised, organic -remains will probably first appear and disappear at different levels, owing to -the migration of species and to geographical changes. And in the distant -future, a geologist examining these beds, might be tempted to conclude that the -average duration of life of the embedded fossils had been less than that of the -glacial period, instead of having been really far greater, that is extending -from before the glacial epoch to the present day. - -In order to get a perfect gradation between two forms in the upper and lower -parts of the same formation, the deposit must have gone on accumulating for a -very long period, in order to have given sufficient time for the slow process -of variation; hence the deposit will generally have to be a very thick one; and -the species undergoing modification will have had to live on the same area -throughout this whole time. But we have seen that a thick fossiliferous -formation can only be accumulated during a period of subsidence; and to keep -the depth approximately the same, which is necessary in order to enable the -same species to live on the same space, the supply of sediment must nearly have -counterbalanced the amount of subsidence. But this same movement of subsidence -will often tend to sink the area whence the sediment is derived, and thus -diminish the supply whilst the downward movement continues. In fact, this -nearly exact balancing between the supply of sediment and the amount of -subsidence is probably a rare contingency; for it has been observed by more -than one palæontologist, that very thick deposits are usually barren of organic -remains, except near their upper or lower limits. - -It would seem that each separate formation, like the whole pile of formations -in any country, has generally been intermittent in its accumulation. When we -see, as is so often the case, a formation composed of beds of different -mineralogical composition, we may reasonably suspect that the process of -deposition has been much interrupted, as a change in the currents of the sea -and a supply of sediment of a different nature will generally have been due to -geographical changes requiring much time. Nor will the closest inspection of a -formation give any idea of the time which its deposition has consumed. Many -instances could be given of beds only a few feet in thickness, representing -formations, elsewhere thousands of feet in thickness, and which must have -required an enormous period for their accumulation; yet no one ignorant of this -fact would have suspected the vast lapse of time represented by the thinner -formation. Many cases could be given of the lower beds of a formation having -been upraised, denuded, submerged, and then re-covered by the upper beds of the -same formation,—facts, showing what wide, yet easily overlooked, intervals have -occurred in its accumulation. In other cases we have the plainest evidence in -great fossilised trees, still standing upright as they grew, of many long -intervals of time and changes of level during the process of deposition, which -would never even have been suspected, had not the trees chanced to have been -preserved: thus, Messrs. Lyell and Dawson found carboniferous beds 1400 feet -thick in Nova Scotia, with ancient root-bearing strata, one above the other, at -no less than sixty-eight different levels. Hence, when the same species occur -at the bottom, middle, and top of a formation, the probability is that they -have not lived on the same spot during the whole period of deposition, but have -disappeared and reappeared, perhaps many times, during the same geological -period. So that if such species were to undergo a considerable amount of -modification during any one geological period, a section would not probably -include all the fine intermediate gradations which must on my theory have -existed between them, but abrupt, though perhaps very slight, changes of form. - -It is all-important to remember that naturalists have no golden rule by which -to distinguish species and varieties; they grant some little variability to -each species, but when they meet with a somewhat greater amount of difference -between any two forms, they rank both as species, unless they are enabled to -connect them together by close intermediate gradations. And this from the -reasons just assigned we can seldom hope to effect in any one geological -section. Supposing B and C to be two species, and a third, A, to be found in an -underlying bed; even if A were strictly intermediate between B and C, it would -simply be ranked as a third and distinct species, unless at the same time it -could be most closely connected with either one or both forms by intermediate -varieties. Nor should it be forgotten, as before explained, that A might be the -actual progenitor of B and C, and yet might not at all necessarily be strictly -intermediate between them in all points of structure. So that we might obtain -the parent-species and its several modified descendants from the lower and -upper beds of a formation, and unless we obtained numerous transitional -gradations, we should not recognise their relationship, and should consequently -be compelled to rank them all as distinct species. - -It is notorious on what excessively slight differences many palæontologists -have founded their species; and they do this the more readily if the specimens -come from different sub-stages of the same formation. Some experienced -conchologists are now sinking many of the very fine species of D’Orbigny and -others into the rank of varieties; and on this view we do find the kind of -evidence of change which on my theory we ought to find. Moreover, if we look to -rather wider intervals, namely, to distinct but consecutive stages of the same -great formation, we find that the embedded fossils, though almost universally -ranked as specifically different, yet are far more closely allied to each other -than are the species found in more widely separated formations; but to this -subject I shall have to return in the following chapter. - -One other consideration is worth notice: with animals and plants that can -propagate rapidly and are not highly locomotive, there is reason to suspect, as -we have formerly seen, that their varieties are generally at first local; and -that such local varieties do not spread widely and supplant their parent-forms -until they have been modified and perfected in some considerable degree. -According to this view, the chance of discovering in a formation in any one -country all the early stages of transition between any two forms, is small, for -the successive changes are supposed to have been local or confined to some one -spot. Most marine animals have a wide range; and we have seen that with plants -it is those which have the widest range, that oftenest present varieties; so -that with shells and other marine animals, it is probably those which have had -the widest range, far exceeding the limits of the known geological formations -of Europe, which have oftenest given rise, first to local varieties and -ultimately to new species; and this again would greatly lessen the chance of -our being able to trace the stages of transition in any one geological -formation. - -It should not be forgotten, that at the present day, with perfect specimens for -examination, two forms can seldom be connected by intermediate varieties and -thus proved to be the same species, until many specimens have been collected -from many places; and in the case of fossil species this could rarely be -effected by palæontologists. We shall, perhaps, best perceive the improbability -of our being enabled to connect species by numerous, fine, intermediate, fossil -links, by asking ourselves whether, for instance, geologists at some future -period will be able to prove, that our different breeds of cattle, sheep, -horses, and dogs have descended from a single stock or from several aboriginal -stocks; or, again, whether certain sea-shells inhabiting the shores of North -America, which are ranked by some conchologists as distinct species from their -European representatives, and by other conchologists as only varieties, are -really varieties or are, as it is called, specifically distinct. This could be -effected only by the future geologist discovering in a fossil state numerous -intermediate gradations; and such success seems to me improbable in the highest +migration during climatal and other changes; and when we see a species +first appearing in any formation, the probability is that it only then +first immigrated into that area. It is well known, for instance, that +several species appeared somewhat earlier in the palæozoic beds of North +America than in those of Europe; time having apparently been required +for their migration from the American to the European seas. In examining +the latest deposits of various quarters of the world, it has everywhere +been noted, that some few still existing species are common in the +deposit, but have become extinct in the immediately surrounding sea; or, +conversely, that some are now abundant in the neighbouring sea, but are +rare or absent in this particular deposit. It is an excellent lesson to +reflect on the ascertained amount of migration of the inhabitants of +Europe during the Glacial period, which forms only a part of one whole +geological period; and likewise to reflect on the great changes of +level, on the inordinately great change of climate, on the prodigious +lapse of time, all included within this same glacial period. Yet it may +be doubted whether in any quarter of the world, sedimentary deposits, +including fossil remains, have gone on accumulating within the same area +during the whole of this period. It is not, for instance, probable that +sediment was deposited during the whole of the glacial period near the +mouth of the Mississippi, within that limit of depth at which marine +animals can flourish; for we know what vast geographical changes +occurred in other parts of America during this space of time. When such +beds as were deposited in shallow water near the mouth of the +Mississippi during some part of the glacial period shall have been +upraised, organic remains will probably first appear and disappear at +different levels, owing to the migration of species and to geographical +changes. And in the distant future, a geologist examining these beds, +might be tempted to conclude that the average duration of life of the +embedded fossils had been less than that of the glacial period, instead +of having been really far greater, that is extending from before the +glacial epoch to the present day. + +In order to get a perfect gradation between two forms in the upper and +lower parts of the same formation, the deposit must have gone on +accumulating for a very long period, in order to have given sufficient +time for the slow process of variation; hence the deposit will generally +have to be a very thick one; and the species undergoing modification +will have had to live on the same area throughout this whole time. But +we have seen that a thick fossiliferous formation can only be +accumulated during a period of subsidence; and to keep the depth +approximately the same, which is necessary in order to enable the same +species to live on the same space, the supply of sediment must nearly +have counterbalanced the amount of subsidence. But this same movement of +subsidence will often tend to sink the area whence the sediment is +derived, and thus diminish the supply whilst the downward movement +continues. In fact, this nearly exact balancing between the supply of +sediment and the amount of subsidence is probably a rare contingency; +for it has been observed by more than one palæontologist, that very +thick deposits are usually barren of organic remains, except near their +upper or lower limits. + +It would seem that each separate formation, like the whole pile of +formations in any country, has generally been intermittent in its +accumulation. When we see, as is so often the case, a formation composed +of beds of different mineralogical composition, we may reasonably +suspect that the process of deposition has been much interrupted, as a +change in the currents of the sea and a supply of sediment of a +different nature will generally have been due to geographical changes +requiring much time. Nor will the closest inspection of a formation give +any idea of the time which its deposition has consumed. Many instances +could be given of beds only a few feet in thickness, representing +formations, elsewhere thousands of feet in thickness, and which must +have required an enormous period for their accumulation; yet no one +ignorant of this fact would have suspected the vast lapse of time +represented by the thinner formation. Many cases could be given of the +lower beds of a formation having been upraised, denuded, submerged, and +then re-covered by the upper beds of the same formation,—facts, showing +what wide, yet easily overlooked, intervals have occurred in its +accumulation. In other cases we have the plainest evidence in great +fossilised trees, still standing upright as they grew, of many long +intervals of time and changes of level during the process of deposition, +which would never even have been suspected, had not the trees chanced to +have been preserved: thus, Messrs. Lyell and Dawson found carboniferous +beds 1400 feet thick in Nova Scotia, with ancient root-bearing strata, +one above the other, at no less than sixty-eight different levels. +Hence, when the same species occur at the bottom, middle, and top of a +formation, the probability is that they have not lived on the same spot +during the whole period of deposition, but have disappeared and +reappeared, perhaps many times, during the same geological period. So +that if such species were to undergo a considerable amount of +modification during any one geological period, a section would not +probably include all the fine intermediate gradations which must on my +theory have existed between them, but abrupt, though perhaps very +slight, changes of form. + +It is all-important to remember that naturalists have no golden rule by +which to distinguish species and varieties; they grant some little +variability to each species, but when they meet with a somewhat greater +amount of difference between any two forms, they rank both as species, +unless they are enabled to connect them together by close intermediate +gradations. And this from the reasons just assigned we can seldom hope +to effect in any one geological section. Supposing B and C to be two +species, and a third, A, to be found in an underlying bed; even if A +were strictly intermediate between B and C, it would simply be ranked as +a third and distinct species, unless at the same time it could be most +closely connected with either one or both forms by intermediate +varieties. Nor should it be forgotten, as before explained, that A might +be the actual progenitor of B and C, and yet might not at all +necessarily be strictly intermediate between them in all points of +structure. So that we might obtain the parent-species and its several +modified descendants from the lower and upper beds of a formation, and +unless we obtained numerous transitional gradations, we should not +recognise their relationship, and should consequently be compelled to +rank them all as distinct species. + +It is notorious on what excessively slight differences many +palæontologists have founded their species; and they do this the more +readily if the specimens come from different sub-stages of the same +formation. Some experienced conchologists are now sinking many of the +very fine species of D’Orbigny and others into the rank of varieties; +and on this view we do find the kind of evidence of change which on my +theory we ought to find. Moreover, if we look to rather wider intervals, +namely, to distinct but consecutive stages of the same great formation, +we find that the embedded fossils, though almost universally ranked as +specifically different, yet are far more closely allied to each other +than are the species found in more widely separated formations; but to +this subject I shall have to return in the following chapter. + +One other consideration is worth notice: with animals and plants that +can propagate rapidly and are not highly locomotive, there is reason to +suspect, as we have formerly seen, that their varieties are generally at +first local; and that such local varieties do not spread widely and +supplant their parent-forms until they have been modified and perfected +in some considerable degree. According to this view, the chance of +discovering in a formation in any one country all the early stages of +transition between any two forms, is small, for the successive changes +are supposed to have been local or confined to some one spot. Most +marine animals have a wide range; and we have seen that with plants it +is those which have the widest range, that oftenest present varieties; +so that with shells and other marine animals, it is probably those which +have had the widest range, far exceeding the limits of the known +geological formations of Europe, which have oftenest given rise, first +to local varieties and ultimately to new species; and this again would +greatly lessen the chance of our being able to trace the stages of +transition in any one geological formation. + +It should not be forgotten, that at the present day, with perfect +specimens for examination, two forms can seldom be connected by +intermediate varieties and thus proved to be the same species, until +many specimens have been collected from many places; and in the case of +fossil species this could rarely be effected by palæontologists. We +shall, perhaps, best perceive the improbability of our being enabled to +connect species by numerous, fine, intermediate, fossil links, by asking +ourselves whether, for instance, geologists at some future period will +be able to prove, that our different breeds of cattle, sheep, horses, +and dogs have descended from a single stock or from several aboriginal +stocks; or, again, whether certain sea-shells inhabiting the shores of +North America, which are ranked by some conchologists as distinct +species from their European representatives, and by other conchologists +as only varieties, are really varieties or are, as it is called, +specifically distinct. This could be effected only by the future +geologist discovering in a fossil state numerous intermediate +gradations; and such success seems to me improbable in the highest degree. -Geological research, though it has added numerous species to existing and -extinct genera, and has made the intervals between some few groups less wide -than they otherwise would have been, yet has done scarcely anything in breaking -down the distinction between species, by connecting them together by numerous, -fine, intermediate varieties; and this not having been effected, is probably -the gravest and most obvious of all the many objections which may be urged -against my views. Hence it will be worth while to sum up the foregoing remarks, -under an imaginary illustration. The Malay Archipelago is of about the size of -Europe from the North Cape to the Mediterranean, and from Britain to Russia; -and therefore equals all the geological formations which have been examined -with any accuracy, excepting those of the United States of America. I fully -agree with Mr. Godwin-Austen, that the present condition of the Malay -Archipelago, with its numerous large islands separated by wide and shallow -seas, probably represents the former state of Europe, when most of our -formations were accumulating. The Malay Archipelago is one of the richest -regions of the whole world in organic beings; yet if all the species were to be -collected which have ever lived there, how imperfectly would they represent the -natural history of the world! - -But we have every reason to believe that the terrestrial productions of the -archipelago would be preserved in an excessively imperfect manner in the -formations which we suppose to be there accumulating. I suspect that not many -of the strictly littoral animals, or of those which lived on naked submarine -rocks, would be embedded; and those embedded in gravel or sand, would not -endure to a distant epoch. Wherever sediment did not accumulate on the bed of -the sea, or where it did not accumulate at a sufficient rate to protect organic -bodies from decay, no remains could be preserved. - -In our archipelago, I believe that fossiliferous formations could be formed of -sufficient thickness to last to an age, as distant in futurity as the secondary -formations lie in the past, only during periods of subsidence. These periods of -subsidence would be separated from each other by enormous intervals, during -which the area would be either stationary or rising; whilst rising, each -fossiliferous formation would be destroyed, almost as soon as accumulated, by -the incessant coast-action, as we now see on the shores of South America. -During the periods of subsidence there would probably be much extinction of -life; during the periods of elevation, there would be much variation, but the +Geological research, though it has added numerous species to existing +and extinct genera, and has made the intervals between some few groups +less wide than they otherwise would have been, yet has done scarcely +anything in breaking down the distinction between species, by connecting +them together by numerous, fine, intermediate varieties; and this not +having been effected, is probably the gravest and most obvious of all +the many objections which may be urged against my views. Hence it will +be worth while to sum up the foregoing remarks, under an imaginary +illustration. The Malay Archipelago is of about the size of Europe from +the North Cape to the Mediterranean, and from Britain to Russia; and +therefore equals all the geological formations which have been examined +with any accuracy, excepting those of the United States of America. I +fully agree with Mr. Godwin-Austen, that the present condition of the +Malay Archipelago, with its numerous large islands separated by wide and +shallow seas, probably represents the former state of Europe, when most +of our formations were accumulating. The Malay Archipelago is one of the +richest regions of the whole world in organic beings; yet if all the +species were to be collected which have ever lived there, how +imperfectly would they represent the natural history of the world! + +But we have every reason to believe that the terrestrial productions of +the archipelago would be preserved in an excessively imperfect manner in +the formations which we suppose to be there accumulating. I suspect that +not many of the strictly littoral animals, or of those which lived on +naked submarine rocks, would be embedded; and those embedded in gravel +or sand, would not endure to a distant epoch. Wherever sediment did not +accumulate on the bed of the sea, or where it did not accumulate at a +sufficient rate to protect organic bodies from decay, no remains could +be preserved. + +In our archipelago, I believe that fossiliferous formations could be +formed of sufficient thickness to last to an age, as distant in futurity +as the secondary formations lie in the past, only during periods of +subsidence. These periods of subsidence would be separated from each +other by enormous intervals, during which the area would be either +stationary or rising; whilst rising, each fossiliferous formation would +be destroyed, almost as soon as accumulated, by the incessant +coast-action, as we now see on the shores of South America. During the +periods of subsidence there would probably be much extinction of life; +during the periods of elevation, there would be much variation, but the geological record would then be least perfect. -It may be doubted whether the duration of any one great period of subsidence -over the whole or part of the archipelago, together with a contemporaneous -accumulation of sediment, would exceed the average duration of the same -specific forms; and these contingencies are indispensable for the preservation -of all the transitional gradations between any two or more species. If such -gradations were not fully preserved, transitional varieties would merely appear -as so many distinct species. It is, also, probable that each great period of -subsidence would be interrupted by oscillations of level, and that slight -climatal changes would intervene during such lengthy periods; and in these -cases the inhabitants of the archipelago would have to migrate, and no closely -consecutive record of their modifications could be preserved in any one -formation. - -Very many of the marine inhabitants of the archipelago now range thousands of -miles beyond its confines; and analogy leads me to believe that it would be -chiefly these far-ranging species which would oftenest produce new varieties; -and the varieties would at first generally be local or confined to one place, -but if possessed of any decided advantage, or when further modified and -improved, they would slowly spread and supplant their parent-forms. When such -varieties returned to their ancient homes, as they would differ from their -former state, in a nearly uniform, though perhaps extremely slight degree, they -would, according to the principles followed by many palæontologists, be ranked +It may be doubted whether the duration of any one great period of +subsidence over the whole or part of the archipelago, together with a +contemporaneous accumulation of sediment, would exceed the average +duration of the same specific forms; and these contingencies are +indispensable for the preservation of all the transitional gradations +between any two or more species. If such gradations were not fully +preserved, transitional varieties would merely appear as so many +distinct species. It is, also, probable that each great period of +subsidence would be interrupted by oscillations of level, and that +slight climatal changes would intervene during such lengthy periods; and +in these cases the inhabitants of the archipelago would have to migrate, +and no closely consecutive record of their modifications could be +preserved in any one formation. + +Very many of the marine inhabitants of the archipelago now range +thousands of miles beyond its confines; and analogy leads me to believe +that it would be chiefly these far-ranging species which would oftenest +produce new varieties; and the varieties would at first generally be +local or confined to one place, but if possessed of any decided +advantage, or when further modified and improved, they would slowly +spread and supplant their parent-forms. When such varieties returned to +their ancient homes, as they would differ from their former state, in a +nearly uniform, though perhaps extremely slight degree, they would, +according to the principles followed by many palæontologists, be ranked as new and distinct species. -If then, there be some degree of truth in these remarks, we have no right to -expect to find in our geological formations, an infinite number of those fine -transitional forms, which on my theory assuredly have connected all the past -and present species of the same group into one long and branching chain of -life. We ought only to look for a few links, some more closely, some more -distantly related to each other; and these links, let them be ever so close, if -found in different stages of the same formation, would, by most -palæontologists, be ranked as distinct species. But I do not pretend that I -should ever have suspected how poor a record of the mutations of life, the best -preserved geological section presented, had not the difficulty of our not -discovering innumerable transitional links between the species which appeared -at the commencement and close of each formation, pressed so hardly on my +If then, there be some degree of truth in these remarks, we have no +right to expect to find in our geological formations, an infinite number +of those fine transitional forms, which on my theory assuredly have +connected all the past and present species of the same group into one +long and branching chain of life. We ought only to look for a few links, +some more closely, some more distantly related to each other; and these +links, let them be ever so close, if found in different stages of the +same formation, would, by most palæontologists, be ranked as distinct +species. But I do not pretend that I should ever have suspected how poor +a record of the mutations of life, the best preserved geological section +presented, had not the difficulty of our not discovering innumerable +transitional links between the species which appeared at the +commencement and close of each formation, pressed so hardly on my theory. -On the sudden appearance of whole groups of Allied Species.—The abrupt manner -in which whole groups of species suddenly appear in certain formations, has -been urged by several palæontologists, for instance, by Agassiz, Pictet, and by -none more forcibly than by Professor Sedgwick, as a fatal objection to the -belief in the transmutation of species. If numerous species, belonging to the -same genera or families, have really started into life all at once, the fact -would be fatal to the theory of descent with slow modification through natural -selection. For the development of a group of forms, all of which have descended -from some one progenitor, must have been an extremely slow process; and the -progenitors must have lived long ages before their modified descendants. But we -continually over-rate the perfection of the geological record, and falsely -infer, because certain genera or families have not been found beneath a certain -stage, that they did not exist before that stage. We continually forget how -large the world is, compared with the area over which our geological formations -have been carefully examined; we forget that groups of species may elsewhere -have long existed and have slowly multiplied before they invaded the ancient -archipelagoes of Europe and of the United States. We do not make due allowance -for the enormous intervals of time, which have probably elapsed between our -consecutive formations,—longer perhaps in some cases than the time required for -the accumulation of each formation. These intervals will have given time for -the multiplication of species from some one or some few parent-forms; and in -the succeeding formation such species will appear as if suddenly created. - -I may here recall a remark formerly made, namely that it might require a long -succession of ages to adapt an organism to some new and peculiar line of life, -for instance to fly through the air; but that when this had been effected, and -a few species had thus acquired a great advantage over other organisms, a -comparatively short time would be necessary to produce many divergent forms, -which would be able to spread rapidly and widely throughout the world. - -I will now give a few examples to illustrate these remarks; and to show how -liable we are to error in supposing that whole groups of species have suddenly -been produced. I may recall the well-known fact that in geological treatises, -published not many years ago, the great class of mammals was always spoken of -as having abruptly come in at the commencement of the tertiary series. And now -one of the richest known accumulations of fossil mammals belongs to the middle -of the secondary series; and one true mammal has been discovered in the new red -sandstone at nearly the commencement of this great series. Cuvier used to urge -that no monkey occurred in any tertiary stratum; but now extinct species have -been discovered in India, South America, and in Europe even as far back as the -eocene stage. The most striking case, however, is that of the Whale family; as -these animals have huge bones, are marine, and range over the world, the fact -of not a single bone of a whale having been discovered in any secondary -formation, seemed fully to justify the belief that this great and distinct -order had been suddenly produced in the interval between the latest secondary -and earliest tertiary formation. But now we may read in the Supplement to -Lyell’s ‘Manual,’ published in 1858, clear evidence of the existence of whales -in the upper greensand, some time before the close of the secondary period. - -I may give another instance, which from having passed under my own eyes has -much struck me. In a memoir on Fossil Sessile Cirripedes, I have stated that, -from the number of existing and extinct tertiary species; from the -extraordinary abundance of the individuals of many species all over the world, -from the Arctic regions to the equator, inhabiting various zones of depths from -the upper tidal limits to 50 fathoms; from the perfect manner in which -specimens are preserved in the oldest tertiary beds; from the ease with which -even a fragment of a valve can be recognised; from all these circumstances, I -inferred that had sessile cirripedes existed during the secondary periods, they -would certainly have been preserved and discovered; and as not one species had -been discovered in beds of this age, I concluded that this great group had been -suddenly developed at the commencement of the tertiary series. This was a sore -trouble to me, adding as I thought one more instance of the abrupt appearance -of a great group of species. But my work had hardly been published, when a -skilful palæontologist, M. Bosquet, sent me a drawing of a perfect specimen of -an unmistakeable sessile cirripede, which he had himself extracted from the -chalk of Belgium. And, as if to make the case as striking as possible, this -sessile cirripede was a Chthamalus, a very common, large, and ubiquitous genus, -of which not one specimen has as yet been found even in any tertiary stratum. -Hence we now positively know that sessile cirripedes existed during the -secondary period; and these cirripedes might have been the progenitors of our -many tertiary and existing species. - -The case most frequently insisted on by palæontologists of the apparently -sudden appearance of a whole group of species, is that of the teleostean -fishes, low down in the Chalk period. This group includes the large majority of -existing species. Lately, Professor Pictet has carried their existence one -sub-stage further back; and some palæontologists believe that certain much -older fishes, of which the affinities are as yet imperfectly known, are really -teleostean. Assuming, however, that the whole of them did appear, as Agassiz -believes, at the commencement of the chalk formation, the fact would certainly -be highly remarkable; but I cannot see that it would be an insuperable -difficulty on my theory, unless it could likewise be shown that the species of -this group appeared suddenly and simultaneously throughout the world at this -same period. It is almost superfluous to remark that hardly any fossil-fish are -known from south of the equator; and by running through Pictet’s Palæontology -it will be seen that very few species are known from several formations in -Europe. Some few families of fish now have a confined range; the teleostean -fish might formerly have had a similarly confined range, and after having been -largely developed in some one sea, might have spread widely. Nor have we any -right to suppose that the seas of the world have always been so freely open -from south to north as they are at present. Even at this day, if the Malay -Archipelago were converted into land, the tropical parts of the Indian Ocean -would form a large and perfectly enclosed basin, in which any great group of -marine animals might be multiplied; and here they would remain confined, until -some of the species became adapted to a cooler climate, and were enabled to -double the southern capes of Africa or Australia, and thus reach other and -distant seas. - -From these and similar considerations, but chiefly from our ignorance of the -geology of other countries beyond the confines of Europe and the United States; -and from the revolution in our palæontological ideas on many points, which the -discoveries of even the last dozen years have effected, it seems to me to be -about as rash in us to dogmatize on the succession of organic beings throughout -the world, as it would be for a naturalist to land for five minutes on some one -barren point in Australia, and then to discuss the number and range of its -productions. +On the sudden appearance of whole groups of Allied Species.—The abrupt +manner in which whole groups of species suddenly appear in certain +formations, has been urged by several palæontologists, for instance, by +Agassiz, Pictet, and by none more forcibly than by Professor Sedgwick, +as a fatal objection to the belief in the transmutation of species. If +numerous species, belonging to the same genera or families, have really +started into life all at once, the fact would be fatal to the theory of +descent with slow modification through natural selection. For the +development of a group of forms, all of which have descended from some +one progenitor, must have been an extremely slow process; and the +progenitors must have lived long ages before their modified descendants. +But we continually over-rate the perfection of the geological record, +and falsely infer, because certain genera or families have not been +found beneath a certain stage, that they did not exist before that +stage. We continually forget how large the world is, compared with the +area over which our geological formations have been carefully examined; +we forget that groups of species may elsewhere have long existed and +have slowly multiplied before they invaded the ancient archipelagoes of +Europe and of the United States. We do not make due allowance for the +enormous intervals of time, which have probably elapsed between our +consecutive formations,—longer perhaps in some cases than the time +required for the accumulation of each formation. These intervals will +have given time for the multiplication of species from some one or some +few parent-forms; and in the succeeding formation such species will +appear as if suddenly created. + +I may here recall a remark formerly made, namely that it might require a +long succession of ages to adapt an organism to some new and peculiar +line of life, for instance to fly through the air; but that when this +had been effected, and a few species had thus acquired a great advantage +over other organisms, a comparatively short time would be necessary to +produce many divergent forms, which would be able to spread rapidly and +widely throughout the world. + +I will now give a few examples to illustrate these remarks; and to show +how liable we are to error in supposing that whole groups of species +have suddenly been produced. I may recall the well-known fact that in +geological treatises, published not many years ago, the great class of +mammals was always spoken of as having abruptly come in at the +commencement of the tertiary series. And now one of the richest known +accumulations of fossil mammals belongs to the middle of the secondary +series; and one true mammal has been discovered in the new red sandstone +at nearly the commencement of this great series. Cuvier used to urge +that no monkey occurred in any tertiary stratum; but now extinct species +have been discovered in India, South America, and in Europe even as far +back as the eocene stage. The most striking case, however, is that of +the Whale family; as these animals have huge bones, are marine, and +range over the world, the fact of not a single bone of a whale having +been discovered in any secondary formation, seemed fully to justify the +belief that this great and distinct order had been suddenly produced in +the interval between the latest secondary and earliest tertiary +formation. But now we may read in the Supplement to Lyell’s ‘Manual,’ +published in 1858, clear evidence of the existence of whales in the +upper greensand, some time before the close of the secondary period. + +I may give another instance, which from having passed under my own eyes +has much struck me. In a memoir on Fossil Sessile Cirripedes, I have +stated that, from the number of existing and extinct tertiary species; +from the extraordinary abundance of the individuals of many species all +over the world, from the Arctic regions to the equator, inhabiting +various zones of depths from the upper tidal limits to 50 fathoms; from +the perfect manner in which specimens are preserved in the oldest +tertiary beds; from the ease with which even a fragment of a valve can +be recognised; from all these circumstances, I inferred that had sessile +cirripedes existed during the secondary periods, they would certainly +have been preserved and discovered; and as not one species had been +discovered in beds of this age, I concluded that this great group had +been suddenly developed at the commencement of the tertiary series. This +was a sore trouble to me, adding as I thought one more instance of the +abrupt appearance of a great group of species. But my work had hardly +been published, when a skilful palæontologist, M. Bosquet, sent me a +drawing of a perfect specimen of an unmistakeable sessile cirripede, +which he had himself extracted from the chalk of Belgium. And, as if to +make the case as striking as possible, this sessile cirripede was a +Chthamalus, a very common, large, and ubiquitous genus, of which not one +specimen has as yet been found even in any tertiary stratum. Hence we +now positively know that sessile cirripedes existed during the secondary +period; and these cirripedes might have been the progenitors of our many +tertiary and existing species. + +The case most frequently insisted on by palæontologists of the +apparently sudden appearance of a whole group of species, is that of the +teleostean fishes, low down in the Chalk period. This group includes the +large majority of existing species. Lately, Professor Pictet has carried +their existence one sub-stage further back; and some palæontologists +believe that certain much older fishes, of which the affinities are as +yet imperfectly known, are really teleostean. Assuming, however, that +the whole of them did appear, as Agassiz believes, at the commencement +of the chalk formation, the fact would certainly be highly remarkable; +but I cannot see that it would be an insuperable difficulty on my +theory, unless it could likewise be shown that the species of this group +appeared suddenly and simultaneously throughout the world at this same +period. It is almost superfluous to remark that hardly any fossil-fish +are known from south of the equator; and by running through Pictet’s +Palæontology it will be seen that very few species are known from +several formations in Europe. Some few families of fish now have a +confined range; the teleostean fish might formerly have had a similarly +confined range, and after having been largely developed in some one sea, +might have spread widely. Nor have we any right to suppose that the seas +of the world have always been so freely open from south to north as they +are at present. Even at this day, if the Malay Archipelago were +converted into land, the tropical parts of the Indian Ocean would form a +large and perfectly enclosed basin, in which any great group of marine +animals might be multiplied; and here they would remain confined, until +some of the species became adapted to a cooler climate, and were enabled +to double the southern capes of Africa or Australia, and thus reach +other and distant seas. + +From these and similar considerations, but chiefly from our ignorance of +the geology of other countries beyond the confines of Europe and the +United States; and from the revolution in our palæontological ideas on +many points, which the discoveries of even the last dozen years have +effected, it seems to me to be about as rash in us to dogmatize on the +succession of organic beings throughout the world, as it would be for a +naturalist to land for five minutes on some one barren point in +Australia, and then to discuss the number and range of its productions. On the sudden appearance of groups of Allied Species in the lowest known -fossiliferous strata.—There is another and allied difficulty, which is much -graver. I allude to the manner in which numbers of species of the same group, -suddenly appear in the lowest known fossiliferous rocks. Most of the arguments -which have convinced me that all the existing species of the same group have -descended from one progenitor, apply with nearly equal force to the earliest -known species. For instance, I cannot doubt that all the Silurian trilobites -have descended from some one crustacean, which must have lived long before the -Silurian age, and which probably differed greatly from any known animal. Some -of the most ancient Silurian animals, as the Nautilus, Lingula, etc., do not -differ much from living species; and it cannot on my theory be supposed, that -these old species were the progenitors of all the species of the orders to -which they belong, for they do not present characters in any degree -intermediate between them. If, moreover, they had been the progenitors of these -orders, they would almost certainly have been long ago supplanted and -exterminated by their numerous and improved descendants. - -Consequently, if my theory be true, it is indisputable that before the lowest -Silurian stratum was deposited, long periods elapsed, as long as, or probably -far longer than, the whole interval from the Silurian age to the present day; -and that during these vast, yet quite unknown, periods of time, the world -swarmed with living creatures. - -To the question why we do not find records of these vast primordial periods, I -can give no satisfactory answer. Several of the most eminent geologists, with -Sir R. Murchison at their head, are convinced that we see in the organic -remains of the lowest Silurian stratum the dawn of life on this planet. Other -highly competent judges, as Lyell and the late E. Forbes, dispute this -conclusion. We should not forget that only a small portion of the world is -known with accuracy. M. Barrande has lately added another and lower stage to -the Silurian system, abounding with new and peculiar species. Traces of life -have been detected in the Longmynd beds beneath Barrande’s so-called primordial -zone. The presence of phosphatic nodules and bituminous matter in some of the -lowest azoic rocks, probably indicates the former existence of life at these -periods. But the difficulty of understanding the absence of vast piles of -fossiliferous strata, which on my theory no doubt were somewhere accumulated -before the Silurian epoch, is very great. If these most ancient beds had been -wholly worn away by denudation, or obliterated by metamorphic action, we ought -to find only small remnants of the formations next succeeding them in age, and -these ought to be very generally in a metamorphosed condition. But the -descriptions which we now possess of the Silurian deposits over immense -territories in Russia and in North America, do not support the view, that the -older a formation is, the more it has suffered the extremity of denudation and +fossiliferous strata.—There is another and allied difficulty, which is +much graver. I allude to the manner in which numbers of species of the +same group, suddenly appear in the lowest known fossiliferous rocks. +Most of the arguments which have convinced me that all the existing +species of the same group have descended from one progenitor, apply with +nearly equal force to the earliest known species. For instance, I cannot +doubt that all the Silurian trilobites have descended from some one +crustacean, which must have lived long before the Silurian age, and +which probably differed greatly from any known animal. Some of the most +ancient Silurian animals, as the Nautilus, Lingula, etc., do not differ +much from living species; and it cannot on my theory be supposed, that +these old species were the progenitors of all the species of the orders +to which they belong, for they do not present characters in any degree +intermediate between them. If, moreover, they had been the progenitors +of these orders, they would almost certainly have been long ago +supplanted and exterminated by their numerous and improved descendants. + +Consequently, if my theory be true, it is indisputable that before the +lowest Silurian stratum was deposited, long periods elapsed, as long as, +or probably far longer than, the whole interval from the Silurian age to +the present day; and that during these vast, yet quite unknown, periods +of time, the world swarmed with living creatures. + +To the question why we do not find records of these vast primordial +periods, I can give no satisfactory answer. Several of the most eminent +geologists, with Sir R. Murchison at their head, are convinced that we +see in the organic remains of the lowest Silurian stratum the dawn of +life on this planet. Other highly competent judges, as Lyell and the +late E. Forbes, dispute this conclusion. We should not forget that only +a small portion of the world is known with accuracy. M. Barrande has +lately added another and lower stage to the Silurian system, abounding +with new and peculiar species. Traces of life have been detected in the +Longmynd beds beneath Barrande’s so-called primordial zone. The presence +of phosphatic nodules and bituminous matter in some of the lowest azoic +rocks, probably indicates the former existence of life at these periods. +But the difficulty of understanding the absence of vast piles of +fossiliferous strata, which on my theory no doubt were somewhere +accumulated before the Silurian epoch, is very great. If these most +ancient beds had been wholly worn away by denudation, or obliterated by +metamorphic action, we ought to find only small remnants of the +formations next succeeding them in age, and these ought to be very +generally in a metamorphosed condition. But the descriptions which we +now possess of the Silurian deposits over immense territories in Russia +and in North America, do not support the view, that the older a +formation is, the more it has suffered the extremity of denudation and metamorphism. -The case at present must remain inexplicable; and may be truly urged as a valid -argument against the views here entertained. To show that it may hereafter -receive some explanation, I will give the following hypothesis. From the nature -of the organic remains, which do not appear to have inhabited profound depths, -in the several formations of Europe and of the United States; and from the -amount of sediment, miles in thickness, of which the formations are composed, -we may infer that from first to last large islands or tracts of land, whence -the sediment was derived, occurred in the neighbourhood of the existing -continents of Europe and North America. But we do not know what was the state -of things in the intervals between the successive formations; whether Europe -and the United States during these intervals existed as dry land, or as a -submarine surface near land, on which sediment was not deposited, or again as -the bed of an open and unfathomable sea. - -Looking to the existing oceans, which are thrice as extensive as the land, we -see them studded with many islands; but not one oceanic island is as yet known -to afford even a remnant of any palæozoic or secondary formation. Hence we may -perhaps infer, that during the palæozoic and secondary periods, neither -continents nor continental islands existed where our oceans now extend; for had -they existed there, palæozoic and secondary formations would in all probability -have been accumulated from sediment derived from their wear and tear; and would -have been at least partially upheaved by the oscillations of level, which we -may fairly conclude must have intervened during these enormously long periods. -If then we may infer anything from these facts, we may infer that where our -oceans now extend, oceans have extended from the remotest period of which we -have any record; and on the other hand, that where continents now exist, large -tracts of land have existed, subjected no doubt to great oscillations of level, -since the earliest silurian period. The coloured map appended to my volume on -Coral Reefs, led me to conclude that the great oceans are still mainly areas of -subsidence, the great archipelagoes still areas of oscillations of level, and -the continents areas of elevation. But have we any right to assume that things -have thus remained from eternity? Our continents seem to have been formed by a -preponderance, during many oscillations of level, of the force of elevation; -but may not the areas of preponderant movement have changed in the lapse of -ages? At a period immeasurably antecedent to the silurian epoch, continents may -have existed where oceans are now spread out; and clear and open oceans may -have existed where our continents now stand. Nor should we be justified in -assuming that if, for instance, the bed of the Pacific Ocean were now converted -into a continent, we should there find formations older than the silurian -strata, supposing such to have been formerly deposited; for it might well -happen that strata which had subsided some miles nearer to the centre of the -earth, and which had been pressed on by an enormous weight of superincumbent -water, might have undergone far more metamorphic action than strata which have -always remained nearer to the surface. The immense areas in some parts of the -world, for instance in South America, of bare metamorphic rocks, which must -have been heated under great pressure, have always seemed to me to require some -special explanation; and we may perhaps believe that we see in these large -areas, the many formations long anterior to the silurian epoch in a completely -metamorphosed condition. +The case at present must remain inexplicable; and may be truly urged as +a valid argument against the views here entertained. To show that it may +hereafter receive some explanation, I will give the following +hypothesis. From the nature of the organic remains, which do not appear +to have inhabited profound depths, in the several formations of Europe +and of the United States; and from the amount of sediment, miles in +thickness, of which the formations are composed, we may infer that from +first to last large islands or tracts of land, whence the sediment was +derived, occurred in the neighbourhood of the existing continents of +Europe and North America. But we do not know what was the state of +things in the intervals between the successive formations; whether +Europe and the United States during these intervals existed as dry land, +or as a submarine surface near land, on which sediment was not +deposited, or again as the bed of an open and unfathomable sea. + +Looking to the existing oceans, which are thrice as extensive as the +land, we see them studded with many islands; but not one oceanic island +is as yet known to afford even a remnant of any palæozoic or secondary +formation. Hence we may perhaps infer, that during the palæozoic and +secondary periods, neither continents nor continental islands existed +where our oceans now extend; for had they existed there, palæozoic and +secondary formations would in all probability have been accumulated from +sediment derived from their wear and tear; and would have been at least +partially upheaved by the oscillations of level, which we may fairly +conclude must have intervened during these enormously long periods. If +then we may infer anything from these facts, we may infer that where our +oceans now extend, oceans have extended from the remotest period of +which we have any record; and on the other hand, that where continents +now exist, large tracts of land have existed, subjected no doubt to +great oscillations of level, since the earliest silurian period. The +coloured map appended to my volume on Coral Reefs, led me to conclude +that the great oceans are still mainly areas of subsidence, the great +archipelagoes still areas of oscillations of level, and the continents +areas of elevation. But have we any right to assume that things have +thus remained from eternity? Our continents seem to have been formed by +a preponderance, during many oscillations of level, of the force of +elevation; but may not the areas of preponderant movement have changed +in the lapse of ages? At a period immeasurably antecedent to the +silurian epoch, continents may have existed where oceans are now spread +out; and clear and open oceans may have existed where our continents now +stand. Nor should we be justified in assuming that if, for instance, the +bed of the Pacific Ocean were now converted into a continent, we should +there find formations older than the silurian strata, supposing such to +have been formerly deposited; for it might well happen that strata which +had subsided some miles nearer to the centre of the earth, and which had +been pressed on by an enormous weight of superincumbent water, might +have undergone far more metamorphic action than strata which have always +remained nearer to the surface. The immense areas in some parts of the +world, for instance in South America, of bare metamorphic rocks, which +must have been heated under great pressure, have always seemed to me to +require some special explanation; and we may perhaps believe that we see +in these large areas, the many formations long anterior to the silurian +epoch in a completely metamorphosed condition. The several difficulties here discussed, namely our not finding in the -successive formations infinitely numerous transitional links between the many -species which now exist or have existed; the sudden manner in which whole -groups of species appear in our European formations; the almost entire absence, -as at present known, of fossiliferous formations beneath the Silurian strata, -are all undoubtedly of the gravest nature. We see this in the plainest manner -by the fact that all the most eminent palæontologists, namely Cuvier, Owen, -Agassiz, Barrande, Falconer, E. Forbes, etc., and all our greatest geologists, -as Lyell, Murchison, Sedgwick, etc., have unanimously, often vehemently, -maintained the immutability of species. But I have reason to believe that one -great authority, Sir Charles Lyell, from further reflexion entertains grave +successive formations infinitely numerous transitional links between the +many species which now exist or have existed; the sudden manner in which +whole groups of species appear in our European formations; the almost +entire absence, as at present known, of fossiliferous formations beneath +the Silurian strata, are all undoubtedly of the gravest nature. We see +this in the plainest manner by the fact that all the most eminent +palæontologists, namely Cuvier, Owen, Agassiz, Barrande, Falconer, E. +Forbes, etc., and all our greatest geologists, as Lyell, Murchison, +Sedgwick, etc., have unanimously, often vehemently, maintained the +immutability of species. But I have reason to believe that one great +authority, Sir Charles Lyell, from further reflexion entertains grave doubts on this subject. I feel how rash it is to differ from these great -authorities, to whom, with others, we owe all our knowledge. Those who think -the natural geological record in any degree perfect, and who do not attach much -weight to the facts and arguments of other kinds given in this volume, will -undoubtedly at once reject my theory. For my part, following out Lyell’s -metaphor, I look at the natural geological record, as a history of the world -imperfectly kept, and written in a changing dialect; of this history we possess -the last volume alone, relating only to two or three countries. Of this volume, -only here and there a short chapter has been preserved; and of each page, only -here and there a few lines. Each word of the slowly-changing language, in which -the history is supposed to be written, being more or less different in the -interrupted succession of chapters, may represent the apparently abruptly -changed forms of life, entombed in our consecutive, but widely separated -formations. On this view, the difficulties above discussed are greatly -diminished, or even disappear. - -CHAPTER X. -ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS. - -On the slow and successive appearance of new species. On their different rates -of change. Species once lost do not reappear. Groups of species follow the same -general rules in their appearance and disappearance as do single species. On -Extinction. On simultaneous changes in the forms of life throughout the world. -On the affinities of extinct species to each other and to living species. On -the state of development of ancient forms. On the succession of the same types -within the same areas. Summary of preceding and present chapters. - -Let us now see whether the several facts and rules relating to the geological -succession of organic beings, better accord with the common view of the -immutability of species, or with that of their slow and gradual modification, -through descent and natural selection. - -New species have appeared very slowly, one after another, both on the land and -in the waters. Lyell has shown that it is hardly possible to resist the -evidence on this head in the case of the several tertiary stages; and every -year tends to fill up the blanks between them, and to make the percentage -system of lost and new forms more gradual. In some of the most recent beds, -though undoubtedly of high antiquity if measured by years, only one or two -species are lost forms, and only one or two are new forms, having here appeared -for the first time, either locally, or, as far as we know, on the face of the -earth. If we may trust the observations of Philippi in Sicily, the successive -changes in the marine inhabitants of that island have been many and most -gradual. The secondary formations are more broken; but, as Bronn has remarked, -neither the appearance nor disappearance of their many now extinct species has -been simultaneous in each separate formation. - -Species of different genera and classes have not changed at the same rate, or -in the same degree. In the oldest tertiary beds a few living shells may still -be found in the midst of a multitude of extinct forms. Falconer has given a -striking instance of a similar fact, in an existing crocodile associated with -many strange and lost mammals and reptiles in the sub-Himalayan deposits. The -Silurian Lingula differs but little from the living species of this genus; -whereas most of the other Silurian Molluscs and all the Crustaceans have -changed greatly. The productions of the land seem to change at a quicker rate -than those of the sea, of which a striking instance has lately been observed in -Switzerland. There is some reason to believe that organisms, considered high in -the scale of nature, change more quickly than those that are low: though there -are exceptions to this rule. The amount of organic change, as Pictet has -remarked, does not strictly correspond with the succession of our geological -formations; so that between each two consecutive formations, the forms of life -have seldom changed in exactly the same degree. Yet if we compare any but the -most closely related formations, all the species will be found to have -undergone some change. When a species has once disappeared from the face of the -earth, we have reason to believe that the same identical form never reappears. -The strongest apparent exception to this latter rule, is that of the so-called -“colonies” of M. Barrande, which intrude for a period in the midst of an older -formation, and then allow the pre-existing fauna to reappear; but Lyell’s -explanation, namely, that it is a case of temporary migration from a distinct -geographical province, seems to me satisfactory. - -These several facts accord well with my theory. I believe in no fixed law of -development, causing all the inhabitants of a country to change abruptly, or -simultaneously, or to an equal degree. The process of modification must be -extremely slow. The variability of each species is quite independent of that of -all others. Whether such variability be taken advantage of by natural -selection, and whether the variations be accumulated to a greater or lesser -amount, thus causing a greater or lesser amount of modification in the varying -species, depends on many complex contingencies,—on the variability being of a -beneficial nature, on the power of intercrossing, on the rate of breeding, on -the slowly changing physical conditions of the country, and more especially on -the nature of the other inhabitants with which the varying species comes into -competition. Hence it is by no means surprising that one species should retain -the same identical form much longer than others; or, if changing, that it -should change less. We see the same fact in geographical distribution; for -instance, in the land-shells and coleopterous insects of Madeira having come to -differ considerably from their nearest allies on the continent of Europe, -whereas the marine shells and birds have remained unaltered. We can perhaps -understand the apparently quicker rate of change in terrestrial and in more -highly organised productions compared with marine and lower productions, by the -more complex relations of the higher beings to their organic and inorganic -conditions of life, as explained in a former chapter. When many of the -inhabitants of a country have become modified and improved, we can understand, -on the principle of competition, and on that of the many all-important -relations of organism to organism, that any form which does not become in some -degree modified and improved, will be liable to be exterminated. Hence we can -see why all the species in the same region do at last, if we look to wide -enough intervals of time, become modified; for those which do not change will -become extinct. - -In members of the same class the average amount of change, during long and -equal periods of time, may, perhaps, be nearly the same; but as the -accumulation of long-enduring fossiliferous formations depends on great masses -of sediment having been deposited on areas whilst subsiding, our formations -have been almost necessarily accumulated at wide and irregularly intermittent -intervals; consequently the amount of organic change exhibited by the fossils -embedded in consecutive formations is not equal. Each formation, on this view, -does not mark a new and complete act of creation, but only an occasional scene, -taken almost at hazard, in a slowly changing drama. - -We can clearly understand why a species when once lost should never reappear, -even if the very same conditions of life, organic and inorganic, should recur. -For though the offspring of one species might be adapted (and no doubt this has -occurred in innumerable instances) to fill the exact place of another species -in the economy of nature, and thus supplant it; yet the two forms—the old and -the new—would not be identically the same; for both would almost certainly -inherit different characters from their distinct progenitors. For instance, it -is just possible, if our fantail-pigeons were all destroyed, that fanciers, by -striving during long ages for the same object, might make a new breed hardly -distinguishable from our present fantail; but if the parent rock-pigeon were -also destroyed, and in nature we have every reason to believe that the -parent-form will generally be supplanted and exterminated by its improved -offspring, it is quite incredible that a fantail, identical with the existing -breed, could be raised from any other species of pigeon, or even from the other -well-established races of the domestic pigeon, for the newly-formed fantail -would be almost sure to inherit from its new progenitor some slight -characteristic differences. - -Groups of species, that is, genera and families, follow the same general rules -in their appearance and disappearance as do single species, changing more or -less quickly, and in a greater or lesser degree. A group does not reappear -after it has once disappeared; or its existence, as long as it lasts, is -continuous. I am aware that there are some apparent exceptions to this rule, -but the exceptions are surprisingly few, so few, that E. Forbes, Pictet, and -Woodward (though all strongly opposed to such views as I maintain) admit its -truth; and the rule strictly accords with my theory. For as all the species of -the same group have descended from some one species, it is clear that as long -as any species of the group have appeared in the long succession of ages, so -long must its members have continuously existed, in order to have generated -either new and modified or the same old and unmodified forms. Species of the -genus Lingula, for instance, must have continuously existed by an unbroken -succession of generations, from the lowest Silurian stratum to the present day. - -We have seen in the last chapter that the species of a group sometimes falsely -appear to have come in abruptly; and I have attempted to give an explanation of -this fact, which if true would have been fatal to my views. But such cases are -certainly exceptional; the general rule being a gradual increase in number, -till the group reaches its maximum, and then, sooner or later, it gradually -decreases. If the number of the species of a genus, or the number of the genera -of a family, be represented by a vertical line of varying thickness, crossing -the successive geological formations in which the species are found, the line -will sometimes falsely appear to begin at its lower end, not in a sharp point, -but abruptly; it then gradually thickens upwards, sometimes keeping for a space -of equal thickness, and ultimately thins out in the upper beds, marking the -decrease and final extinction of the species. This gradual increase in number -of the species of a group is strictly conformable with my theory; as the -species of the same genus, and the genera of the same family, can increase only -slowly and progressively; for the process of modification and the production of -a number of allied forms must be slow and gradual,—one species giving rise -first to two or three varieties, these being slowly converted into species, -which in their turn produce by equally slow steps other species, and so on, -like the branching of a great tree from a single stem, till the group becomes +authorities, to whom, with others, we owe all our knowledge. Those who +think the natural geological record in any degree perfect, and who do +not attach much weight to the facts and arguments of other kinds given +in this volume, will undoubtedly at once reject my theory. For my part, +following out Lyell’s metaphor, I look at the natural geological record, +as a history of the world imperfectly kept, and written in a changing +dialect; of this history we possess the last volume alone, relating only +to two or three countries. Of this volume, only here and there a short +chapter has been preserved; and of each page, only here and there a few +lines. Each word of the slowly-changing language, in which the history +is supposed to be written, being more or less different in the +interrupted succession of chapters, may represent the apparently +abruptly changed forms of life, entombed in our consecutive, but widely +separated formations. On this view, the difficulties above discussed are +greatly diminished, or even disappear. + +CHAPTER X. ON THE GEOLOGICAL SUCCESSION OF ORGANIC BEINGS. + +On the slow and successive appearance of new species. On their different +rates of change. Species once lost do not reappear. Groups of species +follow the same general rules in their appearance and disappearance as +do single species. On Extinction. On simultaneous changes in the forms +of life throughout the world. On the affinities of extinct species to +each other and to living species. On the state of development of ancient +forms. On the succession of the same types within the same areas. +Summary of preceding and present chapters. + +Let us now see whether the several facts and rules relating to the +geological succession of organic beings, better accord with the common +view of the immutability of species, or with that of their slow and +gradual modification, through descent and natural selection. + +New species have appeared very slowly, one after another, both on the +land and in the waters. Lyell has shown that it is hardly possible to +resist the evidence on this head in the case of the several tertiary +stages; and every year tends to fill up the blanks between them, and to +make the percentage system of lost and new forms more gradual. In some +of the most recent beds, though undoubtedly of high antiquity if +measured by years, only one or two species are lost forms, and only one +or two are new forms, having here appeared for the first time, either +locally, or, as far as we know, on the face of the earth. If we may +trust the observations of Philippi in Sicily, the successive changes in +the marine inhabitants of that island have been many and most gradual. +The secondary formations are more broken; but, as Bronn has remarked, +neither the appearance nor disappearance of their many now extinct +species has been simultaneous in each separate formation. + +Species of different genera and classes have not changed at the same +rate, or in the same degree. In the oldest tertiary beds a few living +shells may still be found in the midst of a multitude of extinct forms. +Falconer has given a striking instance of a similar fact, in an existing +crocodile associated with many strange and lost mammals and reptiles in +the sub-Himalayan deposits. The Silurian Lingula differs but little from +the living species of this genus; whereas most of the other Silurian +Molluscs and all the Crustaceans have changed greatly. The productions +of the land seem to change at a quicker rate than those of the sea, of +which a striking instance has lately been observed in Switzerland. There +is some reason to believe that organisms, considered high in the scale +of nature, change more quickly than those that are low: though there are +exceptions to this rule. The amount of organic change, as Pictet has +remarked, does not strictly correspond with the succession of our +geological formations; so that between each two consecutive formations, +the forms of life have seldom changed in exactly the same degree. Yet if +we compare any but the most closely related formations, all the species +will be found to have undergone some change. When a species has once +disappeared from the face of the earth, we have reason to believe that +the same identical form never reappears. The strongest apparent +exception to this latter rule, is that of the so-called “colonies” of M. +Barrande, which intrude for a period in the midst of an older formation, +and then allow the pre-existing fauna to reappear; but Lyell’s +explanation, namely, that it is a case of temporary migration from a +distinct geographical province, seems to me satisfactory. + +These several facts accord well with my theory. I believe in no fixed +law of development, causing all the inhabitants of a country to change +abruptly, or simultaneously, or to an equal degree. The process of +modification must be extremely slow. The variability of each species is +quite independent of that of all others. Whether such variability be +taken advantage of by natural selection, and whether the variations be +accumulated to a greater or lesser amount, thus causing a greater or +lesser amount of modification in the varying species, depends on many +complex contingencies,—on the variability being of a beneficial nature, +on the power of intercrossing, on the rate of breeding, on the slowly +changing physical conditions of the country, and more especially on the +nature of the other inhabitants with which the varying species comes +into competition. Hence it is by no means surprising that one species +should retain the same identical form much longer than others; or, if +changing, that it should change less. We see the same fact in +geographical distribution; for instance, in the land-shells and +coleopterous insects of Madeira having come to differ considerably from +their nearest allies on the continent of Europe, whereas the marine +shells and birds have remained unaltered. We can perhaps understand the +apparently quicker rate of change in terrestrial and in more highly +organised productions compared with marine and lower productions, by the +more complex relations of the higher beings to their organic and +inorganic conditions of life, as explained in a former chapter. When +many of the inhabitants of a country have become modified and improved, +we can understand, on the principle of competition, and on that of the +many all-important relations of organism to organism, that any form +which does not become in some degree modified and improved, will be +liable to be exterminated. Hence we can see why all the species in the +same region do at last, if we look to wide enough intervals of time, +become modified; for those which do not change will become extinct. + +In members of the same class the average amount of change, during long +and equal periods of time, may, perhaps, be nearly the same; but as the +accumulation of long-enduring fossiliferous formations depends on great +masses of sediment having been deposited on areas whilst subsiding, our +formations have been almost necessarily accumulated at wide and +irregularly intermittent intervals; consequently the amount of organic +change exhibited by the fossils embedded in consecutive formations is +not equal. Each formation, on this view, does not mark a new and +complete act of creation, but only an occasional scene, taken almost at +hazard, in a slowly changing drama. + +We can clearly understand why a species when once lost should never +reappear, even if the very same conditions of life, organic and +inorganic, should recur. For though the offspring of one species might +be adapted (and no doubt this has occurred in innumerable instances) to +fill the exact place of another species in the economy of nature, and +thus supplant it; yet the two forms—the old and the new—would not be +identically the same; for both would almost certainly inherit different +characters from their distinct progenitors. For instance, it is just +possible, if our fantail-pigeons were all destroyed, that fanciers, by +striving during long ages for the same object, might make a new breed +hardly distinguishable from our present fantail; but if the parent +rock-pigeon were also destroyed, and in nature we have every reason to +believe that the parent-form will generally be supplanted and +exterminated by its improved offspring, it is quite incredible that a +fantail, identical with the existing breed, could be raised from any +other species of pigeon, or even from the other well-established races +of the domestic pigeon, for the newly-formed fantail would be almost +sure to inherit from its new progenitor some slight characteristic +differences. + +Groups of species, that is, genera and families, follow the same general +rules in their appearance and disappearance as do single species, +changing more or less quickly, and in a greater or lesser degree. A +group does not reappear after it has once disappeared; or its existence, +as long as it lasts, is continuous. I am aware that there are some +apparent exceptions to this rule, but the exceptions are surprisingly +few, so few, that E. Forbes, Pictet, and Woodward (though all strongly +opposed to such views as I maintain) admit its truth; and the rule +strictly accords with my theory. For as all the species of the same +group have descended from some one species, it is clear that as long as +any species of the group have appeared in the long succession of ages, +so long must its members have continuously existed, in order to have +generated either new and modified or the same old and unmodified forms. +Species of the genus Lingula, for instance, must have continuously +existed by an unbroken succession of generations, from the lowest +Silurian stratum to the present day. + +We have seen in the last chapter that the species of a group sometimes +falsely appear to have come in abruptly; and I have attempted to give an +explanation of this fact, which if true would have been fatal to my +views. But such cases are certainly exceptional; the general rule being +a gradual increase in number, till the group reaches its maximum, and +then, sooner or later, it gradually decreases. If the number of the +species of a genus, or the number of the genera of a family, be +represented by a vertical line of varying thickness, crossing the +successive geological formations in which the species are found, the +line will sometimes falsely appear to begin at its lower end, not in a +sharp point, but abruptly; it then gradually thickens upwards, sometimes +keeping for a space of equal thickness, and ultimately thins out in the +upper beds, marking the decrease and final extinction of the species. +This gradual increase in number of the species of a group is strictly +conformable with my theory; as the species of the same genus, and the +genera of the same family, can increase only slowly and progressively; +for the process of modification and the production of a number of allied +forms must be slow and gradual,—one species giving rise first to two or +three varieties, these being slowly converted into species, which in +their turn produce by equally slow steps other species, and so on, like +the branching of a great tree from a single stem, till the group becomes large. -On Extinction.—We have as yet spoken only incidentally of the disappearance of -species and of groups of species. On the theory of natural selection the -extinction of old forms and the production of new and improved forms are -intimately connected together. The old notion of all the inhabitants of the -earth having been swept away at successive periods by catastrophes, is very -generally given up, even by those geologists, as Elie de Beaumont, Murchison, -Barrande, etc., whose general views would naturally lead them to this -conclusion. On the contrary, we have every reason to believe, from the study of -the tertiary formations, that species and groups of species gradually -disappear, one after another, first from one spot, then from another, and -finally from the world. Both single species and whole groups of species last -for very unequal periods; some groups, as we have seen, having endured from the -earliest known dawn of life to the present day; some having disappeared before -the close of the palæozoic period. No fixed law seems to determine the length -of time during which any single species or any single genus endures. There is -reason to believe that the complete extinction of the species of a group is -generally a slower process than their production: if the appearance and -disappearance of a group of species be represented, as before, by a vertical -line of varying thickness, the line is found to taper more gradually at its -upper end, which marks the progress of extermination, than at its lower end, -which marks the first appearance and increase in numbers of the species. In -some cases, however, the extermination of whole groups of beings, as of -ammonites towards the close of the secondary period, has been wonderfully -sudden. - -The whole subject of the extinction of species has been involved in the most -gratuitous mystery. Some authors have even supposed that as the individual has -a definite length of life, so have species a definite duration. No one I think -can have marvelled more at the extinction of species, than I have done. When I -found in La Plata the tooth of a horse embedded with the remains of Mastodon, -Megatherium, Toxodon, and other extinct monsters, which all co-existed with -still living shells at a very late geological period, I was filled with -astonishment; for seeing that the horse, since its introduction by the -Spaniards into South America, has run wild over the whole country and has -increased in numbers at an unparalleled rate, I asked myself what could so -recently have exterminated the former horse under conditions of life apparently -so favourable. But how utterly groundless was my astonishment! Professor Owen -soon perceived that the tooth, though so like that of the existing horse, -belonged to an extinct species. Had this horse been still living, but in some -degree rare, no naturalist would have felt the least surprise at its rarity; -for rarity is the attribute of a vast number of species of all classes, in all -countries. If we ask ourselves why this or that species is rare, we answer that -something is unfavourable in its conditions of life; but what that something -is, we can hardly ever tell. On the supposition of the fossil horse still -existing as a rare species, we might have felt certain from the analogy of all -other mammals, even of the slow-breeding elephant, and from the history of the +On Extinction.—We have as yet spoken only incidentally of the +disappearance of species and of groups of species. On the theory of +natural selection the extinction of old forms and the production of new +and improved forms are intimately connected together. The old notion of +all the inhabitants of the earth having been swept away at successive +periods by catastrophes, is very generally given up, even by those +geologists, as Elie de Beaumont, Murchison, Barrande, etc., whose +general views would naturally lead them to this conclusion. On the +contrary, we have every reason to believe, from the study of the +tertiary formations, that species and groups of species gradually +disappear, one after another, first from one spot, then from another, +and finally from the world. Both single species and whole groups of +species last for very unequal periods; some groups, as we have seen, +having endured from the earliest known dawn of life to the present day; +some having disappeared before the close of the palæozoic period. No +fixed law seems to determine the length of time during which any single +species or any single genus endures. There is reason to believe that the +complete extinction of the species of a group is generally a slower +process than their production: if the appearance and disappearance of a +group of species be represented, as before, by a vertical line of +varying thickness, the line is found to taper more gradually at its +upper end, which marks the progress of extermination, than at its lower +end, which marks the first appearance and increase in numbers of the +species. In some cases, however, the extermination of whole groups of +beings, as of ammonites towards the close of the secondary period, has +been wonderfully sudden. + +The whole subject of the extinction of species has been involved in the +most gratuitous mystery. Some authors have even supposed that as the +individual has a definite length of life, so have species a definite +duration. No one I think can have marvelled more at the extinction of +species, than I have done. When I found in La Plata the tooth of a horse +embedded with the remains of Mastodon, Megatherium, Toxodon, and other +extinct monsters, which all co-existed with still living shells at a +very late geological period, I was filled with astonishment; for seeing +that the horse, since its introduction by the Spaniards into South +America, has run wild over the whole country and has increased in +numbers at an unparalleled rate, I asked myself what could so recently +have exterminated the former horse under conditions of life apparently +so favourable. But how utterly groundless was my astonishment! Professor +Owen soon perceived that the tooth, though so like that of the existing +horse, belonged to an extinct species. Had this horse been still living, +but in some degree rare, no naturalist would have felt the least +surprise at its rarity; for rarity is the attribute of a vast number of +species of all classes, in all countries. If we ask ourselves why this +or that species is rare, we answer that something is unfavourable in its +conditions of life; but what that something is, we can hardly ever tell. +On the supposition of the fossil horse still existing as a rare species, +we might have felt certain from the analogy of all other mammals, even +of the slow-breeding elephant, and from the history of the naturalisation of the domestic horse in South America, that under more -favourable conditions it would in a very few years have stocked the whole -continent. But we could not have told what the unfavourable conditions were -which checked its increase, whether some one or several contingencies, and at -what period of the horse’s life, and in what degree, they severally acted. If -the conditions had gone on, however slowly, becoming less and less favourable, -we assuredly should not have perceived the fact, yet the fossil horse would -certainly have become rarer and rarer, and finally extinct;—its place being -seized on by some more successful competitor. - -It is most difficult always to remember that the increase of every living being -is constantly being checked by unperceived injurious agencies; and that these -same unperceived agencies are amply sufficient to cause rarity, and finally -extinction. We see in many cases in the more recent tertiary formations, that -rarity precedes extinction; and we know that this has been the progress of -events with those animals which have been exterminated, either locally or -wholly, through man’s agency. I may repeat what I published in 1845, namely, -that to admit that species generally become rare before they become extinct—to -feel no surprise at the rarity of a species, and yet to marvel greatly when it -ceases to exist, is much the same as to admit that sickness in the individual -is the forerunner of death—to feel no surprise at sickness, but when the sick -man dies, to wonder and to suspect that he died by some unknown deed of -violence. +favourable conditions it would in a very few years have stocked the +whole continent. But we could not have told what the unfavourable +conditions were which checked its increase, whether some one or several +contingencies, and at what period of the horse’s life, and in what +degree, they severally acted. If the conditions had gone on, however +slowly, becoming less and less favourable, we assuredly should not have +perceived the fact, yet the fossil horse would certainly have become +rarer and rarer, and finally extinct;—its place being seized on by some +more successful competitor. + +It is most difficult always to remember that the increase of every +living being is constantly being checked by unperceived injurious +agencies; and that these same unperceived agencies are amply sufficient +to cause rarity, and finally extinction. We see in many cases in the +more recent tertiary formations, that rarity precedes extinction; and we +know that this has been the progress of events with those animals which +have been exterminated, either locally or wholly, through man’s agency. +I may repeat what I published in 1845, namely, that to admit that +species generally become rare before they become extinct—to feel no +surprise at the rarity of a species, and yet to marvel greatly when it +ceases to exist, is much the same as to admit that sickness in the +individual is the forerunner of death—to feel no surprise at sickness, +but when the sick man dies, to wonder and to suspect that he died by +some unknown deed of violence. The theory of natural selection is grounded on the belief that each new -variety, and ultimately each new species, is produced and maintained by having -some advantage over those with which it comes into competition; and the -consequent extinction of less-favoured forms almost inevitably follows. It is -the same with our domestic productions: when a new and slightly improved -variety has been raised, it at first supplants the less improved varieties in -the same neighbourhood; when much improved it is transported far and near, like -our short-horn cattle, and takes the place of other breeds in other countries. -Thus the appearance of new forms and the disappearance of old forms, both -natural and artificial, are bound together. In certain flourishing groups, the -number of new specific forms which have been produced within a given time is -probably greater than that of the old forms which have been exterminated; but -we know that the number of species has not gone on indefinitely increasing, at -least during the later geological periods, so that looking to later times we -may believe that the production of new forms has caused the extinction of about -the same number of old forms. +variety, and ultimately each new species, is produced and maintained by +having some advantage over those with which it comes into competition; +and the consequent extinction of less-favoured forms almost inevitably +follows. It is the same with our domestic productions: when a new and +slightly improved variety has been raised, it at first supplants the +less improved varieties in the same neighbourhood; when much improved it +is transported far and near, like our short-horn cattle, and takes the +place of other breeds in other countries. Thus the appearance of new +forms and the disappearance of old forms, both natural and artificial, +are bound together. In certain flourishing groups, the number of new +specific forms which have been produced within a given time is probably +greater than that of the old forms which have been exterminated; but we +know that the number of species has not gone on indefinitely increasing, +at least during the later geological periods, so that looking to later +times we may believe that the production of new forms has caused the +extinction of about the same number of old forms. The competition will generally be most severe, as formerly explained and -illustrated by examples, between the forms which are most like each other in -all respects. Hence the improved and modified descendants of a species will -generally cause the extermination of the parent-species; and if many new forms -have been developed from any one species, the nearest allies of that species, -i.e. the species of the same genus, will be the most liable to extermination. -Thus, as I believe, a number of new species descended from one species, that is -a new genus, comes to supplant an old genus, belonging to the same family. But -it must often have happened that a new species belonging to some one group will -have seized on the place occupied by a species belonging to a distinct group, -and thus caused its extermination; and if many allied forms be developed from -the successful intruder, many will have to yield their places; and it will -generally be allied forms, which will suffer from some inherited inferiority in -common. But whether it be species belonging to the same or to a distinct class, -which yield their places to other species which have been modified and -improved, a few of the sufferers may often long be preserved, from being fitted -to some peculiar line of life, or from inhabiting some distant and isolated -station, where they have escaped severe competition. For instance, a single -species of Trigonia, a great genus of shells in the secondary formations, -survives in the Australian seas; and a few members of the great and almost -extinct group of Ganoid fishes still inhabit our fresh waters. Therefore the -utter extinction of a group is generally, as we have seen, a slower process -than its production. +illustrated by examples, between the forms which are most like each +other in all respects. Hence the improved and modified descendants of a +species will generally cause the extermination of the parent-species; +and if many new forms have been developed from any one species, the +nearest allies of that species, i.e. the species of the same genus, will +be the most liable to extermination. Thus, as I believe, a number of +new species descended from one species, that is a new genus, comes to +supplant an old genus, belonging to the same family. But it must often +have happened that a new species belonging to some one group will have +seized on the place occupied by a species belonging to a distinct group, +and thus caused its extermination; and if many allied forms be developed +from the successful intruder, many will have to yield their places; and +it will generally be allied forms, which will suffer from some inherited +inferiority in common. But whether it be species belonging to the same +or to a distinct class, which yield their places to other species which +have been modified and improved, a few of the sufferers may often long +be preserved, from being fitted to some peculiar line of life, or from +inhabiting some distant and isolated station, where they have escaped +severe competition. For instance, a single species of Trigonia, a great +genus of shells in the secondary formations, survives in the Australian +seas; and a few members of the great and almost extinct group of Ganoid +fishes still inhabit our fresh waters. Therefore the utter extinction of +a group is generally, as we have seen, a slower process than its +production. With respect to the apparently sudden extermination of whole families or -orders, as of Trilobites at the close of the palæozoic period and of Ammonites -at the close of the secondary period, we must remember what has been already -said on the probable wide intervals of time between our consecutive formations; -and in these intervals there may have been much slow extermination. Moreover, -when by sudden immigration or by unusually rapid development, many species of a -new group have taken possession of a new area, they will have exterminated in a -correspondingly rapid manner many of the old inhabitants; and the forms which -thus yield their places will commonly be allied, for they will partake of some +orders, as of Trilobites at the close of the palæozoic period and of +Ammonites at the close of the secondary period, we must remember what +has been already said on the probable wide intervals of time between our +consecutive formations; and in these intervals there may have been much +slow extermination. Moreover, when by sudden immigration or by unusually +rapid development, many species of a new group have taken possession of +a new area, they will have exterminated in a correspondingly rapid +manner many of the old inhabitants; and the forms which thus yield their +places will commonly be allied, for they will partake of some inferiority in common. -Thus, as it seems to me, the manner in which single species and whole groups of -species become extinct, accords well with the theory of natural selection. We -need not marvel at extinction; if we must marvel, let it be at our presumption -in imagining for a moment that we understand the many complex contingencies, on -which the existence of each species depends. If we forget for an instant, that -each species tends to increase inordinately, and that some check is always in -action, yet seldom perceived by us, the whole economy of nature will be utterly -obscured. Whenever we can precisely say why this species is more abundant in -individuals than that; why this species and not another can be naturalised in a -given country; then, and not till then, we may justly feel surprise why we -cannot account for the extinction of this particular species or group of -species. +Thus, as it seems to me, the manner in which single species and whole +groups of species become extinct, accords well with the theory of +natural selection. We need not marvel at extinction; if we must marvel, +let it be at our presumption in imagining for a moment that we +understand the many complex contingencies, on which the existence of +each species depends. If we forget for an instant, that each species +tends to increase inordinately, and that some check is always in action, +yet seldom perceived by us, the whole economy of nature will be utterly +obscured. Whenever we can precisely say why this species is more +abundant in individuals than that; why this species and not another can +be naturalised in a given country; then, and not till then, we may +justly feel surprise why we cannot account for the extinction of this +particular species or group of species. On the Forms of Life changing almost simultaneously throughout the World -.—Scarcely any palæontological discovery is more striking than the fact, that -the forms of life change almost simultaneously throughout the world. Thus our -European Chalk formation can be recognised in many distant parts of the world, -under the most different climates, where not a fragment of the mineral chalk -itself can be found; namely, in North America, in equatorial South America, in -Tierra del Fuego, at the Cape of Good Hope, and in the peninsula of India. For -at these distant points, the organic remains in certain beds present an -unmistakeable degree of resemblance to those of the Chalk. It is not that the -same species are met with; for in some cases not one species is identically the -same, but they belong to the same families, genera, and sections of genera, and -sometimes are similarly characterised in such trifling points as mere -superficial sculpture. Moreover other forms, which are not found in the Chalk -of Europe, but which occur in the formations either above or below, are -similarly absent at these distant points of the world. In the several -successive palæozoic formations of Russia, Western Europe and North America, a -similar parallelism in the forms of life has been observed by several authors: -so it is, according to Lyell, with the several European and North American -tertiary deposits. Even if the few fossil species which are common to the Old -and New Worlds be kept wholly out of view, the general parallelism in the -successive forms of life, in the stages of the widely separated palæozoic and -tertiary periods, would still be manifest, and the several formations could be +.—Scarcely any palæontological discovery is more striking than the fact, +that the forms of life change almost simultaneously throughout the +world. Thus our European Chalk formation can be recognised in many +distant parts of the world, under the most different climates, where not +a fragment of the mineral chalk itself can be found; namely, in North +America, in equatorial South America, in Tierra del Fuego, at the Cape +of Good Hope, and in the peninsula of India. For at these distant +points, the organic remains in certain beds present an unmistakeable +degree of resemblance to those of the Chalk. It is not that the same +species are met with; for in some cases not one species is identically +the same, but they belong to the same families, genera, and sections of +genera, and sometimes are similarly characterised in such trifling +points as mere superficial sculpture. Moreover other forms, which are +not found in the Chalk of Europe, but which occur in the formations +either above or below, are similarly absent at these distant points of +the world. In the several successive palæozoic formations of Russia, +Western Europe and North America, a similar parallelism in the forms of +life has been observed by several authors: so it is, according to Lyell, +with the several European and North American tertiary deposits. Even if +the few fossil species which are common to the Old and New Worlds be +kept wholly out of view, the general parallelism in the successive forms +of life, in the stages of the widely separated palæozoic and tertiary +periods, would still be manifest, and the several formations could be easily correlated. -These observations, however, relate to the marine inhabitants of distant parts -of the world: we have not sufficient data to judge whether the productions of -the land and of fresh water change at distant points in the same parallel -manner. We may doubt whether they have thus changed: if the Megatherium, -Mylodon, Macrauchenia, and Toxodon had been brought to Europe from La Plata, -without any information in regard to their geological position, no one would -have suspected that they had coexisted with still living sea-shells; but as -these anomalous monsters coexisted with the Mastodon and Horse, it might at -least have been inferred that they had lived during one of the latter tertiary -stages. - -When the marine forms of life are spoken of as having changed simultaneously -throughout the world, it must not be supposed that this expression relates to -the same thousandth or hundred-thousandth year, or even that it has a very -strict geological sense; for if all the marine animals which live at the -present day in Europe, and all those that lived in Europe during the -pleistocene period (an enormously remote period as measured by years, including -the whole glacial epoch), were to be compared with those now living in South -America or in Australia, the most skilful naturalist would hardly be able to -say whether the existing or the pleistocene inhabitants of Europe resembled -most closely those of the southern hemisphere. So, again, several highly -competent observers believe that the existing productions of the United States -are more closely related to those which lived in Europe during certain later -tertiary stages, than to those which now live here; and if this be so, it is -evident that fossiliferous beds deposited at the present day on the shores of -North America would hereafter be liable to be classed with somewhat older -European beds. Nevertheless, looking to a remotely future epoch, there can, I -think, be little doubt that all the more modern marine formations, namely, the -upper pliocene, the pleistocene and strictly modern beds, of Europe, North and -South America, and Australia, from containing fossil remains in some degree -allied, and from not including those forms which are only found in the older -underlying deposits, would be correctly ranked as simultaneous in a geological +These observations, however, relate to the marine inhabitants of distant +parts of the world: we have not sufficient data to judge whether the +productions of the land and of fresh water change at distant points in +the same parallel manner. We may doubt whether they have thus changed: +if the Megatherium, Mylodon, Macrauchenia, and Toxodon had been brought +to Europe from La Plata, without any information in regard to their +geological position, no one would have suspected that they had coexisted +with still living sea-shells; but as these anomalous monsters coexisted +with the Mastodon and Horse, it might at least have been inferred that +they had lived during one of the latter tertiary stages. + +When the marine forms of life are spoken of as having changed +simultaneously throughout the world, it must not be supposed that this +expression relates to the same thousandth or hundred-thousandth year, or +even that it has a very strict geological sense; for if all the marine +animals which live at the present day in Europe, and all those that +lived in Europe during the pleistocene period (an enormously remote +period as measured by years, including the whole glacial epoch), were to +be compared with those now living in South America or in Australia, the +most skilful naturalist would hardly be able to say whether the existing +or the pleistocene inhabitants of Europe resembled most closely those of +the southern hemisphere. So, again, several highly competent observers +believe that the existing productions of the United States are more +closely related to those which lived in Europe during certain later +tertiary stages, than to those which now live here; and if this be so, +it is evident that fossiliferous beds deposited at the present day on +the shores of North America would hereafter be liable to be classed with +somewhat older European beds. Nevertheless, looking to a remotely future +epoch, there can, I think, be little doubt that all the more modern +marine formations, namely, the upper pliocene, the pleistocene and +strictly modern beds, of Europe, North and South America, and Australia, +from containing fossil remains in some degree allied, and from not +including those forms which are only found in the older underlying +deposits, would be correctly ranked as simultaneous in a geological sense. -The fact of the forms of life changing simultaneously, in the above large -sense, at distant parts of the world, has greatly struck those admirable -observers, MM. de Verneuil and d’Archiac. After referring to the parallelism of -the palæozoic forms of life in various parts of Europe, they add, “If struck by -this strange sequence, we turn our attention to North America, and there -discover a series of analogous phenomena, it will appear certain that all these -modifications of species, their extinction, and the introduction of new ones, -cannot be owing to mere changes in marine currents or other causes more or less -local and temporary, but depend on general laws which govern the whole animal -kingdom.” M. Barrande has made forcible remarks to precisely the same effect. -It is, indeed, quite futile to look to changes of currents, climate, or other -physical conditions, as the cause of these great mutations in the forms of life -throughout the world, under the most different climates. We must, as Barrande -has remarked, look to some special law. We shall see this more clearly when we -treat of the present distribution of organic beings, and find how slight is the -relation between the physical conditions of various countries, and the nature -of their inhabitants. - -This great fact of the parallel succession of the forms of life throughout the -world, is explicable on the theory of natural selection. New species are formed -by new varieties arising, which have some advantage over older forms; and those -forms, which are already dominant, or have some advantage over the other forms -in their own country, would naturally oftenest give rise to new varieties or -incipient species; for these latter must be victorious in a still higher degree -in order to be preserved and to survive. We have distinct evidence on this -head, in the plants which are dominant, that is, which are commonest in their -own homes, and are most widely diffused, having produced the greatest number of -new varieties. It is also natural that the dominant, varying, and far-spreading -species, which already have invaded to a certain extent the territories of -other species, should be those which would have the best chance of spreading -still further, and of giving rise in new countries to new varieties and -species. The process of diffusion may often be very slow, being dependent on -climatal and geographical changes, or on strange accidents, but in the long run -the dominant forms will generally succeed in spreading. The diffusion would, it -is probable, be slower with the terrestrial inhabitants of distinct continents -than with the marine inhabitants of the continuous sea. We might therefore -expect to find, as we apparently do find, a less strict degree of parallel -succession in the productions of the land than of the sea. - -Dominant species spreading from any region might encounter still more dominant -species, and then their triumphant course, or even their existence, would -cease. We know not at all precisely what are all the conditions most favourable -for the multiplication of new and dominant species; but we can, I think, -clearly see that a number of individuals, from giving a better chance of the -appearance of favourable variations, and that severe competition with many -already existing forms, would be highly favourable, as would be the power of -spreading into new territories. A certain amount of isolation, recurring at -long intervals of time, would probably be also favourable, as before explained. -One quarter of the world may have been most favourable for the production of -new and dominant species on the land, and another for those in the waters of -the sea. If two great regions had been for a long period favourably -circumstanced in an equal degree, whenever their inhabitants met, the battle -would be prolonged and severe; and some from one birthplace and some from the -other might be victorious. But in the course of time, the forms dominant in the -highest degree, wherever produced, would tend everywhere to prevail. As they -prevailed, they would cause the extinction of other and inferior forms; and as -these inferior forms would be allied in groups by inheritance, whole groups -would tend slowly to disappear; though here and there a single member might -long be enabled to survive. +The fact of the forms of life changing simultaneously, in the above +large sense, at distant parts of the world, has greatly struck those +admirable observers, MM. de Verneuil and d’Archiac. After referring to +the parallelism of the palæozoic forms of life in various parts of +Europe, they add, “If struck by this strange sequence, we turn our +attention to North America, and there discover a series of analogous +phenomena, it will appear certain that all these modifications of +species, their extinction, and the introduction of new ones, cannot be +owing to mere changes in marine currents or other causes more or less +local and temporary, but depend on general laws which govern the whole +animal kingdom.” M. Barrande has made forcible remarks to precisely the +same effect. It is, indeed, quite futile to look to changes of +currents, climate, or other physical conditions, as the cause of these +great mutations in the forms of life throughout the world, under the +most different climates. We must, as Barrande has remarked, look to some +special law. We shall see this more clearly when we treat of the present +distribution of organic beings, and find how slight is the relation +between the physical conditions of various countries, and the nature of +their inhabitants. + +This great fact of the parallel succession of the forms of life +throughout the world, is explicable on the theory of natural selection. +New species are formed by new varieties arising, which have some +advantage over older forms; and those forms, which are already dominant, +or have some advantage over the other forms in their own country, would +naturally oftenest give rise to new varieties or incipient species; for +these latter must be victorious in a still higher degree in order to be +preserved and to survive. We have distinct evidence on this head, in the +plants which are dominant, that is, which are commonest in their own +homes, and are most widely diffused, having produced the greatest number +of new varieties. It is also natural that the dominant, varying, and +far-spreading species, which already have invaded to a certain extent +the territories of other species, should be those which would have the +best chance of spreading still further, and of giving rise in new +countries to new varieties and species. The process of diffusion may +often be very slow, being dependent on climatal and geographical +changes, or on strange accidents, but in the long run the dominant forms +will generally succeed in spreading. The diffusion would, it is +probable, be slower with the terrestrial inhabitants of distinct +continents than with the marine inhabitants of the continuous sea. We +might therefore expect to find, as we apparently do find, a less strict +degree of parallel succession in the productions of the land than of the +sea. + +Dominant species spreading from any region might encounter still more +dominant species, and then their triumphant course, or even their +existence, would cease. We know not at all precisely what are all the +conditions most favourable for the multiplication of new and dominant +species; but we can, I think, clearly see that a number of individuals, +from giving a better chance of the appearance of favourable variations, +and that severe competition with many already existing forms, would be +highly favourable, as would be the power of spreading into new +territories. A certain amount of isolation, recurring at long intervals +of time, would probably be also favourable, as before explained. One +quarter of the world may have been most favourable for the production of +new and dominant species on the land, and another for those in the +waters of the sea. If two great regions had been for a long period +favourably circumstanced in an equal degree, whenever their inhabitants +met, the battle would be prolonged and severe; and some from one +birthplace and some from the other might be victorious. But in the +course of time, the forms dominant in the highest degree, wherever +produced, would tend everywhere to prevail. As they prevailed, they +would cause the extinction of other and inferior forms; and as these +inferior forms would be allied in groups by inheritance, whole groups +would tend slowly to disappear; though here and there a single member +might long be enabled to survive. Thus, as it seems to me, the parallel, and, taken in a large sense, simultaneous, succession of the same forms of life throughout the world, -accords well with the principle of new species having been formed by dominant -species spreading widely and varying; the new species thus produced being -themselves dominant owing to inheritance, and to having already had some -advantage over their parents or over other species; these again spreading, -varying, and producing new species. The forms which are beaten and which yield -their places to the new and victorious forms, will generally be allied in -groups, from inheriting some inferiority in common; and therefore as new and -improved groups spread throughout the world, old groups will disappear from the -world; and the succession of forms in both ways will everywhere tend to -correspond. - -There is one other remark connected with this subject worth making. I have -given my reasons for believing that all our greater fossiliferous formations -were deposited during periods of subsidence; and that blank intervals of vast -duration occurred during the periods when the bed of the sea was either -stationary or rising, and likewise when sediment was not thrown down quickly -enough to embed and preserve organic remains. During these long and blank -intervals I suppose that the inhabitants of each region underwent a -considerable amount of modification and extinction, and that there was much -migration from other parts of the world. As we have reason to believe that -large areas are affected by the same movement, it is probable that strictly -contemporaneous formations have often been accumulated over very wide spaces in -the same quarter of the world; but we are far from having any right to conclude -that this has invariably been the case, and that large areas have invariably -been affected by the same movements. When two formations have been deposited in -two regions during nearly, but not exactly the same period, we should find in -both, from the causes explained in the foregoing paragraphs, the same general -succession in the forms of life; but the species would not exactly correspond; -for there will have been a little more time in the one region than in the other -for modification, extinction, and immigration. - -I suspect that cases of this nature have occurred in Europe. Mr. Prestwich, in -his admirable Memoirs on the eocene deposits of England and France, is able to -draw a close general parallelism between the successive stages in the two -countries; but when he compares certain stages in England with those in France, -although he finds in both a curious accordance in the numbers of the species -belonging to the same genera, yet the species themselves differ in a manner -very difficult to account for, considering the proximity of the two -areas,—unless, indeed, it be assumed that an isthmus separated two seas -inhabited by distinct, but contemporaneous, faunas. Lyell has made similar -observations on some of the later tertiary formations. Barrande, also, shows -that there is a striking general parallelism in the successive Silurian -deposits of Bohemia and Scandinavia; nevertheless he finds a surprising amount -of difference in the species. If the several formations in these regions have -not been deposited during the same exact periods,—a formation in one region -often corresponding with a blank interval in the other,—and if in both regions -the species have gone on slowly changing during the accumulation of the several -formations and during the long intervals of time between them; in this case, -the several formations in the two regions could be arranged in the same order, -in accordance with the general succession of the form of life, and the order -would falsely appear to be strictly parallel; nevertheless the species would -not all be the same in the apparently corresponding stages in the two regions. - -On the Affinities of extinct Species to each other, and to living forms.—Let us -now look to the mutual affinities of extinct and living species. They all fall -into one grand natural system; and this fact is at once explained on the -principle of descent. The more ancient any form is, the more, as a general -rule, it differs from living forms. But, as Buckland long ago remarked, all -fossils can be classed either in still existing groups, or between them. That -the extinct forms of life help to fill up the wide intervals between existing -genera, families, and orders, cannot be disputed. For if we confine our -attention either to the living or to the extinct alone, the series is far less -perfect than if we combine both into one general system. With respect to the -Vertebrata, whole pages could be filled with striking illustrations from our -great palæontologist, Owen, showing how extinct animals fall in between -existing groups. Cuvier ranked the Ruminants and Pachyderms, as the two most -distinct orders of mammals; but Owen has discovered so many fossil links, that -he has had to alter the whole classification of these two orders; and has -placed certain pachyderms in the same sub-order with ruminants: for example, he -dissolves by fine gradations the apparently wide difference between the pig and -the camel. In regard to the Invertebrata, Barrande, and a higher authority -could not be named, asserts that he is every day taught that palæozoic animals, -though belonging to the same orders, families, or genera with those living at -the present day, were not at this early epoch limited in such distinct groups -as they now are. - -Some writers have objected to any extinct species or group of species being -considered as intermediate between living species or groups. If by this term it -is meant that an extinct form is directly intermediate in all its characters -between two living forms, the objection is probably valid. But I apprehend that -in a perfectly natural classification many fossil species would have to stand -between living species, and some extinct genera between living genera, even -between genera belonging to distinct families. The most common case, especially -with respect to very distinct groups, such as fish and reptiles, seems to be, -that supposing them to be distinguished at the present day from each other by a -dozen characters, the ancient members of the same two groups would be +accords well with the principle of new species having been formed by +dominant species spreading widely and varying; the new species thus +produced being themselves dominant owing to inheritance, and to having +already had some advantage over their parents or over other species; +these again spreading, varying, and producing new species. The forms +which are beaten and which yield their places to the new and victorious +forms, will generally be allied in groups, from inheriting some +inferiority in common; and therefore as new and improved groups spread +throughout the world, old groups will disappear from the world; and the +succession of forms in both ways will everywhere tend to correspond. + +There is one other remark connected with this subject worth making. I +have given my reasons for believing that all our greater fossiliferous +formations were deposited during periods of subsidence; and that blank +intervals of vast duration occurred during the periods when the bed of +the sea was either stationary or rising, and likewise when sediment was +not thrown down quickly enough to embed and preserve organic remains. +During these long and blank intervals I suppose that the inhabitants of +each region underwent a considerable amount of modification and +extinction, and that there was much migration from other parts of the +world. As we have reason to believe that large areas are affected by the +same movement, it is probable that strictly contemporaneous formations +have often been accumulated over very wide spaces in the same quarter of +the world; but we are far from having any right to conclude that this +has invariably been the case, and that large areas have invariably been +affected by the same movements. When two formations have been deposited +in two regions during nearly, but not exactly the same period, we should +find in both, from the causes explained in the foregoing paragraphs, the +same general succession in the forms of life; but the species would not +exactly correspond; for there will have been a little more time in the +one region than in the other for modification, extinction, and +immigration. + +I suspect that cases of this nature have occurred in Europe. Mr. +Prestwich, in his admirable Memoirs on the eocene deposits of England +and France, is able to draw a close general parallelism between the +successive stages in the two countries; but when he compares certain +stages in England with those in France, although he finds in both a +curious accordance in the numbers of the species belonging to the same +genera, yet the species themselves differ in a manner very difficult to +account for, considering the proximity of the two areas,—unless, indeed, +it be assumed that an isthmus separated two seas inhabited by distinct, +but contemporaneous, faunas. Lyell has made similar observations on some +of the later tertiary formations. Barrande, also, shows that there is a +striking general parallelism in the successive Silurian deposits of +Bohemia and Scandinavia; nevertheless he finds a surprising amount of +difference in the species. If the several formations in these regions +have not been deposited during the same exact periods,—a formation in +one region often corresponding with a blank interval in the other,—and +if in both regions the species have gone on slowly changing during the +accumulation of the several formations and during the long intervals of +time between them; in this case, the several formations in the two +regions could be arranged in the same order, in accordance with the +general succession of the form of life, and the order would falsely +appear to be strictly parallel; nevertheless the species would not all +be the same in the apparently corresponding stages in the two regions. + +On the Affinities of extinct Species to each other, and to living +forms.—Let us now look to the mutual affinities of extinct and living +species. They all fall into one grand natural system; and this fact is +at once explained on the principle of descent. The more ancient any form +is, the more, as a general rule, it differs from living forms. But, as +Buckland long ago remarked, all fossils can be classed either in still +existing groups, or between them. That the extinct forms of life help to +fill up the wide intervals between existing genera, families, and +orders, cannot be disputed. For if we confine our attention either to +the living or to the extinct alone, the series is far less perfect than +if we combine both into one general system. With respect to the +Vertebrata, whole pages could be filled with striking illustrations from +our great palæontologist, Owen, showing how extinct animals fall in +between existing groups. Cuvier ranked the Ruminants and Pachyderms, as +the two most distinct orders of mammals; but Owen has discovered so many +fossil links, that he has had to alter the whole classification of these +two orders; and has placed certain pachyderms in the same sub-order with +ruminants: for example, he dissolves by fine gradations the apparently +wide difference between the pig and the camel. In regard to the +Invertebrata, Barrande, and a higher authority could not be named, +asserts that he is every day taught that palæozoic animals, though +belonging to the same orders, families, or genera with those living at +the present day, were not at this early epoch limited in such distinct +groups as they now are. + +Some writers have objected to any extinct species or group of species +being considered as intermediate between living species or groups. If by +this term it is meant that an extinct form is directly intermediate in +all its characters between two living forms, the objection is probably +valid. But I apprehend that in a perfectly natural classification many +fossil species would have to stand between living species, and some +extinct genera between living genera, even between genera belonging to +distinct families. The most common case, especially with respect to very +distinct groups, such as fish and reptiles, seems to be, that supposing +them to be distinguished at the present day from each other by a dozen +characters, the ancient members of the same two groups would be distinguished by a somewhat lesser number of characters, so that the two -groups, though formerly quite distinct, at that period made some small approach -to each other. - -It is a common belief that the more ancient a form is, by so much the more it -tends to connect by some of its characters groups now widely separated from -each other. This remark no doubt must be restricted to those groups which have -undergone much change in the course of geological ages; and it would be -difficult to prove the truth of the proposition, for every now and then even a -living animal, as the Lepidosiren, is discovered having affinities directed -towards very distinct groups. Yet if we compare the older Reptiles and -Batrachians, the older Fish, the older Cephalopods, and the eocene Mammals, -with the more recent members of the same classes, we must admit that there is +groups, though formerly quite distinct, at that period made some small +approach to each other. + +It is a common belief that the more ancient a form is, by so much the +more it tends to connect by some of its characters groups now widely +separated from each other. This remark no doubt must be restricted to +those groups which have undergone much change in the course of +geological ages; and it would be difficult to prove the truth of the +proposition, for every now and then even a living animal, as the +Lepidosiren, is discovered having affinities directed towards very +distinct groups. Yet if we compare the older Reptiles and Batrachians, +the older Fish, the older Cephalopods, and the eocene Mammals, with the +more recent members of the same classes, we must admit that there is some truth in the remark. -Let us see how far these several facts and inferences accord with the theory of -descent with modification. As the subject is somewhat complex, I must request -the reader to turn to the diagram in the fourth chapter. We may suppose that -the numbered letters represent genera, and the dotted lines diverging from them -the species in each genus. The diagram is much too simple, too few genera and -too few species being given, but this is unimportant for us. The horizontal -lines may represent successive geological formations, and all the forms beneath -the uppermost line may be considered as extinct. The three existing genera, a^ -14, q^14, p^14, will form a small family; b^14 and f^14 a closely allied family -or sub-family; and o^14, e^14, m^14, a third family. These three families, -together with the many extinct genera on the several lines of descent diverging -from the parent-form A, will form an order; for all will have inherited -something in common from their ancient and common progenitor. On the principle -of the continued tendency to divergence of character, which was formerly -illustrated by this diagram, the more recent any form is, the more it will -generally differ from its ancient progenitor. Hence we can understand the rule -that the most ancient fossils differ most from existing forms. We must not, -however, assume that divergence of character is a necessary contingency; it -depends solely on the descendants from a species being thus enabled to seize on -many and different places in the economy of nature. Therefore it is quite -possible, as we have seen in the case of some Silurian forms, that a species -might go on being slightly modified in relation to its slightly altered -conditions of life, and yet retain throughout a vast period the same general -characteristics. This is represented in the diagram by the letter F^14. - -All the many forms, extinct and recent, descended from A, make, as before -remarked, one order; and this order, from the continued effects of extinction -and divergence of character, has become divided into several sub-families and -families, some of which are supposed to have perished at different periods, and -some to have endured to the present day. +Let us see how far these several facts and inferences accord with the +theory of descent with modification. As the subject is somewhat complex, +I must request the reader to turn to the diagram in the fourth chapter. +We may suppose that the numbered letters represent genera, and the +dotted lines diverging from them the species in each genus. The diagram +is much too simple, too few genera and too few species being given, but +this is unimportant for us. The horizontal lines may represent +successive geological formations, and all the forms beneath the +uppermost line may be considered as extinct. The three existing genera, +a^ 14, q^14, p^14, will form a small family; b^14 and f^14 a closely +allied family or sub-family; and o^14, e^14, m^14, a third family. These +three families, together with the many extinct genera on the several +lines of descent diverging from the parent-form A, will form an order; +for all will have inherited something in common from their ancient and +common progenitor. On the principle of the continued tendency to +divergence of character, which was formerly illustrated by this diagram, +the more recent any form is, the more it will generally differ from its +ancient progenitor. Hence we can understand the rule that the most +ancient fossils differ most from existing forms. We must not, however, +assume that divergence of character is a necessary contingency; it +depends solely on the descendants from a species being thus enabled to +seize on many and different places in the economy of nature. Therefore +it is quite possible, as we have seen in the case of some Silurian +forms, that a species might go on being slightly modified in relation to +its slightly altered conditions of life, and yet retain throughout a +vast period the same general characteristics. This is represented in the +diagram by the letter F^14. + +All the many forms, extinct and recent, descended from A, make, as +before remarked, one order; and this order, from the continued effects +of extinction and divergence of character, has become divided into +several sub-families and families, some of which are supposed to have +perished at different periods, and some to have endured to the present +day. By looking at the diagram we can see that if many of the extinct forms, supposed to be embedded in the successive formations, were discovered at -several points low down in the series, the three existing families on the -uppermost line would be rendered less distinct from each other. If, for -instance, the genera a^1, a^5, a^10, f^8, m^3, m^6, m^9 were disinterred, these -three families would be so closely linked together that they probably would -have to be united into one great family, in nearly the same manner as has -occurred with ruminants and pachyderms. Yet he who objected to call the extinct -genera, which thus linked the living genera of three families together, -intermediate in character, would be justified, as they are intermediate, not -directly, but only by a long and circuitous course through many widely -different forms. If many extinct forms were to be discovered above one of the -middle horizontal lines or geological formations—for instance, above Number -VI.—but none from beneath this line, then only the two families on the left -hand (namely, a^14, etc., and b^14, etc.) would have to be united into one -family; and the two other families (namely, a^14 to f^14 now including five -genera, and o^14 to m^14) would yet remain distinct. These two families, -however, would be less distinct from each other than they were before the -discovery of the fossils. If, for instance, we suppose the existing genera of -the two families to differ from each other by a dozen characters, in this case -the genera, at the early period marked VI., would differ by a lesser number of -characters; for at this early stage of descent they have not diverged in -character from the common progenitor of the order, nearly so much as they -subsequently diverged. Thus it comes that ancient and extinct genera are often -in some slight degree intermediate in character between their modified +several points low down in the series, the three existing families on +the uppermost line would be rendered less distinct from each other. If, +for instance, the genera a^1, a^5, a^10, f^8, m^3, m^6, m^9 were +disinterred, these three families would be so closely linked together +that they probably would have to be united into one great family, in +nearly the same manner as has occurred with ruminants and pachyderms. +Yet he who objected to call the extinct genera, which thus linked the +living genera of three families together, intermediate in character, +would be justified, as they are intermediate, not directly, but only by +a long and circuitous course through many widely different forms. If +many extinct forms were to be discovered above one of the middle +horizontal lines or geological formations—for instance, above Number +VI.—but none from beneath this line, then only the two families on the +left hand (namely, a^14, etc., and b^14, etc.) would have to be united +into one family; and the two other families (namely, a^14 to f^14 now +including five genera, and o^14 to m^14) would yet remain distinct. +These two families, however, would be less distinct from each other than +they were before the discovery of the fossils. If, for instance, we +suppose the existing genera of the two families to differ from each +other by a dozen characters, in this case the genera, at the early +period marked VI., would differ by a lesser number of characters; for at +this early stage of descent they have not diverged in character from the +common progenitor of the order, nearly so much as they subsequently +diverged. Thus it comes that ancient and extinct genera are often in +some slight degree intermediate in character between their modified descendants, or between their collateral relations. -In nature the case will be far more complicated than is represented in the -diagram; for the groups will have been more numerous, they will have endured -for extremely unequal lengths of time, and will have been modified in various -degrees. As we possess only the last volume of the geological record, and that -in a very broken condition, we have no right to expect, except in very rare -cases, to fill up wide intervals in the natural system, and thus unite distinct -families or orders. All that we have a right to expect, is that those groups, -which have within known geological periods undergone much modification, should -in the older formations make some slight approach to each other; so that the -older members should differ less from each other in some of their characters -than do the existing members of the same groups; and this by the concurrent -evidence of our best palæontologists seems frequently to be the case. - -Thus, on the theory of descent with modification, the main facts with respect -to the mutual affinities of the extinct forms of life to each other and to -living forms, seem to me explained in a satisfactory manner. And they are -wholly inexplicable on any other view. - -On this same theory, it is evident that the fauna of any great period in the -earth’s history will be intermediate in general character between that which -preceded and that which succeeded it. Thus, the species which lived at the -sixth great stage of descent in the diagram are the modified offspring of those -which lived at the fifth stage, and are the parents of those which became still -more modified at the seventh stage; hence they could hardly fail to be nearly -intermediate in character between the forms of life above and below. We must, -however, allow for the entire extinction of some preceding forms, and for the -coming in of quite new forms by immigration, and for a large amount of -modification, during the long and blank intervals between the successive -formations. Subject to these allowances, the fauna of each geological period -undoubtedly is intermediate in character, between the preceding and succeeding -faunas. I need give only one instance, namely, the manner in which the fossils -of the Devonian system, when this system was first discovered, were at once -recognised by palæontologists as intermediate in character between those of the -overlying carboniferous, and underlying Silurian system. But each fauna is not -necessarily exactly intermediate, as unequal intervals of time have elapsed -between consecutive formations. - -It is no real objection to the truth of the statement, that the fauna of each -period as a whole is nearly intermediate in character between the preceding and -succeeding faunas, that certain genera offer exceptions to the rule. For -instance, mastodons and elephants, when arranged by Dr. Falconer in two series, -first according to their mutual affinities and then according to their periods -of existence, do not accord in arrangement. The species extreme in character -are not the oldest, or the most recent; nor are those which are intermediate in -character, intermediate in age. But supposing for an instant, in this and other -such cases, that the record of the first appearance and disappearance of the -species was perfect, we have no reason to believe that forms successively -produced necessarily endure for corresponding lengths of time: a very ancient -form might occasionally last much longer than a form elsewhere subsequently -produced, especially in the case of terrestrial productions inhabiting -separated districts. To compare small things with great: if the principal -living and extinct races of the domestic pigeon were arranged as well as they -could be in serial affinity, this arrangement would not closely accord with the -order in time of their production, and still less with the order of their -disappearance; for the parent rock-pigeon now lives; and many varieties between -the rock-pigeon and the carrier have become extinct; and carriers which are -extreme in the important character of length of beak originated earlier than -short-beaked tumblers, which are at the opposite end of the series in this same -respect. +In nature the case will be far more complicated than is represented in +the diagram; for the groups will have been more numerous, they will have +endured for extremely unequal lengths of time, and will have been +modified in various degrees. As we possess only the last volume of the +geological record, and that in a very broken condition, we have no right +to expect, except in very rare cases, to fill up wide intervals in the +natural system, and thus unite distinct families or orders. All that we +have a right to expect, is that those groups, which have within known +geological periods undergone much modification, should in the older +formations make some slight approach to each other; so that the older +members should differ less from each other in some of their characters +than do the existing members of the same groups; and this by the +concurrent evidence of our best palæontologists seems frequently to be +the case. + +Thus, on the theory of descent with modification, the main facts with +respect to the mutual affinities of the extinct forms of life to each +other and to living forms, seem to me explained in a satisfactory +manner. And they are wholly inexplicable on any other view. + +On this same theory, it is evident that the fauna of any great period in +the earth’s history will be intermediate in general character between +that which preceded and that which succeeded it. Thus, the species which +lived at the sixth great stage of descent in the diagram are the +modified offspring of those which lived at the fifth stage, and are the +parents of those which became still more modified at the seventh stage; +hence they could hardly fail to be nearly intermediate in character +between the forms of life above and below. We must, however, allow for +the entire extinction of some preceding forms, and for the coming in of +quite new forms by immigration, and for a large amount of modification, +during the long and blank intervals between the successive formations. +Subject to these allowances, the fauna of each geological period +undoubtedly is intermediate in character, between the preceding and +succeeding faunas. I need give only one instance, namely, the manner in +which the fossils of the Devonian system, when this system was first +discovered, were at once recognised by palæontologists as intermediate +in character between those of the overlying carboniferous, and +underlying Silurian system. But each fauna is not necessarily exactly +intermediate, as unequal intervals of time have elapsed between +consecutive formations. + +It is no real objection to the truth of the statement, that the fauna of +each period as a whole is nearly intermediate in character between the +preceding and succeeding faunas, that certain genera offer exceptions to +the rule. For instance, mastodons and elephants, when arranged by Dr. +Falconer in two series, first according to their mutual affinities and +then according to their periods of existence, do not accord in +arrangement. The species extreme in character are not the oldest, or the +most recent; nor are those which are intermediate in character, +intermediate in age. But supposing for an instant, in this and other +such cases, that the record of the first appearance and disappearance of +the species was perfect, we have no reason to believe that forms +successively produced necessarily endure for corresponding lengths of +time: a very ancient form might occasionally last much longer than a +form elsewhere subsequently produced, especially in the case of +terrestrial productions inhabiting separated districts. To compare small +things with great: if the principal living and extinct races of the +domestic pigeon were arranged as well as they could be in serial +affinity, this arrangement would not closely accord with the order in +time of their production, and still less with the order of their +disappearance; for the parent rock-pigeon now lives; and many varieties +between the rock-pigeon and the carrier have become extinct; and +carriers which are extreme in the important character of length of beak +originated earlier than short-beaked tumblers, which are at the opposite +end of the series in this same respect. Closely connected with the statement, that the organic remains from an -intermediate formation are in some degree intermediate in character, is the -fact, insisted on by all palæontologists, that fossils from two consecutive -formations are far more closely related to each other, than are the fossils -from two remote formations. Pictet gives as a well-known instance, the general -resemblance of the organic remains from the several stages of the chalk -formation, though the species are distinct in each stage. This fact alone, from -its generality, seems to have shaken Professor Pictet in his firm belief in the -immutability of species. He who is acquainted with the distribution of existing -species over the globe, will not attempt to account for the close resemblance -of the distinct species in closely consecutive formations, by the physical -conditions of the ancient areas having remained nearly the same. Let it be -remembered that the forms of life, at least those inhabiting the sea, have -changed almost simultaneously throughout the world, and therefore under the -most different climates and conditions. Consider the prodigious vicissitudes of -climate during the pleistocene period, which includes the whole glacial period, -and note how little the specific forms of the inhabitants of the sea have been -affected. - -On the theory of descent, the full meaning of the fact of fossil remains from -closely consecutive formations, though ranked as distinct species, being -closely related, is obvious. As the accumulation of each formation has often -been interrupted, and as long blank intervals have intervened between -successive formations, we ought not to expect to find, as I attempted to show -in the last chapter, in any one or two formations all the intermediate -varieties between the species which appeared at the commencement and close of -these periods; but we ought to find after intervals, very long as measured by -years, but only moderately long as measured geologically, closely allied forms, -or, as they have been called by some authors, representative species; and these -we assuredly do find. We find, in short, such evidence of the slow and scarcely -sensible mutation of specific forms, as we have a just right to expect to find. - -On the state of Development of Ancient Forms.—There has been much discussion -whether recent forms are more highly developed than ancient. I will not here -enter on this subject, for naturalists have not as yet defined to each other’s -satisfaction what is meant by high and low forms. But in one particular sense -the more recent forms must, on my theory, be higher than the more ancient; for -each new species is formed by having had some advantage in the struggle for -life over other and preceding forms. If under a nearly similar climate, the -eocene inhabitants of one quarter of the world were put into competition with -the existing inhabitants of the same or some other quarter, the eocene fauna or -flora would certainly be beaten and exterminated; as would a secondary fauna by -an eocene, and a palæozoic fauna by a secondary fauna. I do not doubt that this -process of improvement has affected in a marked and sensible manner the -organisation of the more recent and victorious forms of life, in comparison -with the ancient and beaten forms; but I can see no way of testing this sort of -progress. Crustaceans, for instance, not the highest in their own class, may -have beaten the highest molluscs. From the extraordinary manner in which -European productions have recently spread over New Zealand, and have seized on -places which must have been previously occupied, we may believe, if all the -animals and plants of Great Britain were set free in New Zealand, that in the -course of time a multitude of British forms would become thoroughly naturalized -there, and would exterminate many of the natives. On the other hand, from what -we see now occurring in New Zealand, and from hardly a single inhabitant of the -southern hemisphere having become wild in any part of Europe, we may doubt, if -all the productions of New Zealand were set free in Great Britain, whether any -considerable number would be enabled to seize on places now occupied by our -native plants and animals. Under this point of view, the productions of Great -Britain may be said to be higher than those of New Zealand. Yet the most -skilful naturalist from an examination of the species of the two countries -could not have foreseen this result. - -Agassiz insists that ancient animals resemble to a certain extent the embryos -of recent animals of the same classes; or that the geological succession of -extinct forms is in some degree parallel to the embryological development of -recent forms. I must follow Pictet and Huxley in thinking that the truth of -this doctrine is very far from proved. Yet I fully expect to see it hereafter -confirmed, at least in regard to subordinate groups, which have branched off -from each other within comparatively recent times. For this doctrine of Agassiz -accords well with the theory of natural selection. In a future chapter I shall -attempt to show that the adult differs from its embryo, owing to variations -supervening at a not early age, and being inherited at a corresponding age. -This process, whilst it leaves the embryo almost unaltered, continually adds, -in the course of successive generations, more and more difference to the adult. - -Thus the embryo comes to be left as a sort of picture, preserved by nature, of -the ancient and less modified condition of each animal. This view may be true, -and yet it may never be capable of full proof. Seeing, for instance, that the -oldest known mammals, reptiles, and fish strictly belong to their own proper -classes, though some of these old forms are in a slight degree less distinct -from each other than are the typical members of the same groups at the present -day, it would be vain to look for animals having the common embryological -character of the Vertebrata, until beds far beneath the lowest Silurian strata -are discovered—a discovery of which the chance is very small. - -On the Succession of the same Types within the same areas, during the later -tertiary periods.—Mr. Clift many years ago showed that the fossil mammals from -the Australian caves were closely allied to the living marsupials of that -continent. In South America, a similar relationship is manifest, even to an -uneducated eye, in the gigantic pieces of armour like those of the armadillo, -found in several parts of La Plata; and Professor Owen has shown in the most -striking manner that most of the fossil mammals, buried there in such numbers, -are related to South American types. This relationship is even more clearly -seen in the wonderful collection of fossil bones made by MM. Lund and Clausen -in the caves of Brazil. I was so much impressed with these facts that I +intermediate formation are in some degree intermediate in character, is +the fact, insisted on by all palæontologists, that fossils from two +consecutive formations are far more closely related to each other, than +are the fossils from two remote formations. Pictet gives as a well-known +instance, the general resemblance of the organic remains from the +several stages of the chalk formation, though the species are distinct +in each stage. This fact alone, from its generality, seems to have +shaken Professor Pictet in his firm belief in the immutability of +species. He who is acquainted with the distribution of existing species +over the globe, will not attempt to account for the close resemblance of +the distinct species in closely consecutive formations, by the physical +conditions of the ancient areas having remained nearly the same. Let it +be remembered that the forms of life, at least those inhabiting the sea, +have changed almost simultaneously throughout the world, and therefore +under the most different climates and conditions. Consider the +prodigious vicissitudes of climate during the pleistocene period, which +includes the whole glacial period, and note how little the specific +forms of the inhabitants of the sea have been affected. + +On the theory of descent, the full meaning of the fact of fossil remains +from closely consecutive formations, though ranked as distinct species, +being closely related, is obvious. As the accumulation of each formation +has often been interrupted, and as long blank intervals have intervened +between successive formations, we ought not to expect to find, as I +attempted to show in the last chapter, in any one or two formations all +the intermediate varieties between the species which appeared at the +commencement and close of these periods; but we ought to find after +intervals, very long as measured by years, but only moderately long as +measured geologically, closely allied forms, or, as they have been +called by some authors, representative species; and these we assuredly +do find. We find, in short, such evidence of the slow and scarcely +sensible mutation of specific forms, as we have a just right to expect +to find. + +On the state of Development of Ancient Forms.—There has been much +discussion whether recent forms are more highly developed than ancient. +I will not here enter on this subject, for naturalists have not as yet +defined to each other’s satisfaction what is meant by high and low +forms. But in one particular sense the more recent forms must, on my +theory, be higher than the more ancient; for each new species is formed +by having had some advantage in the struggle for life over other and +preceding forms. If under a nearly similar climate, the eocene +inhabitants of one quarter of the world were put into competition with +the existing inhabitants of the same or some other quarter, the eocene +fauna or flora would certainly be beaten and exterminated; as would a +secondary fauna by an eocene, and a palæozoic fauna by a secondary +fauna. I do not doubt that this process of improvement has affected in a +marked and sensible manner the organisation of the more recent and +victorious forms of life, in comparison with the ancient and beaten +forms; but I can see no way of testing this sort of progress. +Crustaceans, for instance, not the highest in their own class, may have +beaten the highest molluscs. From the extraordinary manner in which +European productions have recently spread over New Zealand, and have +seized on places which must have been previously occupied, we may +believe, if all the animals and plants of Great Britain were set free in +New Zealand, that in the course of time a multitude of British forms +would become thoroughly naturalized there, and would exterminate many of +the natives. On the other hand, from what we see now occurring in New +Zealand, and from hardly a single inhabitant of the southern hemisphere +having become wild in any part of Europe, we may doubt, if all the +productions of New Zealand were set free in Great Britain, whether any +considerable number would be enabled to seize on places now occupied by +our native plants and animals. Under this point of view, the productions +of Great Britain may be said to be higher than those of New Zealand. Yet +the most skilful naturalist from an examination of the species of the +two countries could not have foreseen this result. + +Agassiz insists that ancient animals resemble to a certain extent the +embryos of recent animals of the same classes; or that the geological +succession of extinct forms is in some degree parallel to the +embryological development of recent forms. I must follow Pictet and +Huxley in thinking that the truth of this doctrine is very far from +proved. Yet I fully expect to see it hereafter confirmed, at least in +regard to subordinate groups, which have branched off from each other +within comparatively recent times. For this doctrine of Agassiz accords +well with the theory of natural selection. In a future chapter I shall +attempt to show that the adult differs from its embryo, owing to +variations supervening at a not early age, and being inherited at a +corresponding age. This process, whilst it leaves the embryo almost +unaltered, continually adds, in the course of successive generations, +more and more difference to the adult. + +Thus the embryo comes to be left as a sort of picture, preserved by +nature, of the ancient and less modified condition of each animal. This +view may be true, and yet it may never be capable of full proof. Seeing, +for instance, that the oldest known mammals, reptiles, and fish strictly +belong to their own proper classes, though some of these old forms are +in a slight degree less distinct from each other than are the typical +members of the same groups at the present day, it would be vain to look +for animals having the common embryological character of the Vertebrata, +until beds far beneath the lowest Silurian strata are discovered—a +discovery of which the chance is very small. + +On the Succession of the same Types within the same areas, during the +later tertiary periods.—Mr. Clift many years ago showed that the fossil +mammals from the Australian caves were closely allied to the living +marsupials of that continent. In South America, a similar relationship +is manifest, even to an uneducated eye, in the gigantic pieces of armour +like those of the armadillo, found in several parts of La Plata; and +Professor Owen has shown in the most striking manner that most of the +fossil mammals, buried there in such numbers, are related to South +American types. This relationship is even more clearly seen in the +wonderful collection of fossil bones made by MM. Lund and Clausen in the +caves of Brazil. I was so much impressed with these facts that I strongly insisted, in 1839 and 1845, on this “law of the succession of -types,”—on “this wonderful relationship in the same continent between the dead -and the living.” Professor Owen has subsequently extended the same -generalisation to the mammals of the Old World. We see the same law in this -author’s restorations of the extinct and gigantic birds of New Zealand. We see -it also in the birds of the caves of Brazil. Mr. Woodward has shown that the -same law holds good with sea-shells, but from the wide distribution of most -genera of molluscs, it is not well displayed by them. Other cases could be -added, as the relation between the extinct and living land-shells of Madeira; -and between the extinct and living brackish-water shells of the Aralo-Caspian -Sea. - -Now what does this remarkable law of the succession of the same types within -the same areas mean? He would be a bold man, who after comparing the present -climate of Australia and of parts of South America under the same latitude, -would attempt to account, on the one hand, by dissimilar physical conditions -for the dissimilarity of the inhabitants of these two continents, and, on the -other hand, by similarity of conditions, for the uniformity of the same types -in each during the later tertiary periods. Nor can it be pretended that it is -an immutable law that marsupials should have been chiefly or solely produced in -Australia; or that Edentata and other American types should have been solely -produced in South America. For we know that Europe in ancient times was peopled -by numerous marsupials; and I have shown in the publications above alluded to, -that in America the law of distribution of terrestrial mammals was formerly -different from what it now is. North America formerly partook strongly of the -present character of the southern half of the continent; and the southern half -was formerly more closely allied, than it is at present, to the northern half. -In a similar manner we know from Falconer and Cautley’s discoveries, that -northern India was formerly more closely related in its mammals to Africa than -it is at the present time. Analogous facts could be given in relation to the -distribution of marine animals. - -On the theory of descent with modification, the great law of the long enduring, -but not immutable, succession of the same types within the same areas, is at -once explained; for the inhabitants of each quarter of the world will obviously -tend to leave in that quarter, during the next succeeding period of time, -closely allied though in some degree modified descendants. If the inhabitants -of one continent formerly differed greatly from those of another continent, so -will their modified descendants still differ in nearly the same manner and -degree. But after very long intervals of time and after great geographical -changes, permitting much inter-migration, the feebler will yield to the more -dominant forms, and there will be nothing immutable in the laws of past and -present distribution. - -It may be asked in ridicule, whether I suppose that the megatherium and other -allied huge monsters have left behind them in South America the sloth, -armadillo, and anteater, as their degenerate descendants. This cannot for an -instant be admitted. These huge animals have become wholly extinct, and have -left no progeny. But in the caves of Brazil, there are many extinct species -which are closely allied in size and in other characters to the species still -living in South America; and some of these fossils may be the actual -progenitors of living species. It must not be forgotten that, on my theory, all -the species of the same genus have descended from some one species; so that if -six genera, each having eight species, be found in one geological formation, -and in the next succeeding formation there be six other allied or -representative genera with the same number of species, then we may conclude -that only one species of each of the six older genera has left modified -descendants, constituting the six new genera. The other seven species of the -old genera have all died out and have left no progeny. Or, which would probably -be a far commoner case, two or three species of two or three alone of the six -older genera will have been the parents of the six new genera; the other old -species and the other whole genera having become utterly extinct. In failing -orders, with the genera and species decreasing in numbers, as apparently is the -case of the Edentata of South America, still fewer genera and species will have -left modified blood-descendants. - -Summary of the preceding and present Chapters.—I have attempted to show that -the geological record is extremely imperfect; that only a small portion of the -globe has been geologically explored with care; that only certain classes of -organic beings have been largely preserved in a fossil state; that the number -both of specimens and of species, preserved in our museums, is absolutely as -nothing compared with the incalculable number of generations which must have -passed away even during a single formation; that, owing to subsidence being -necessary for the accumulation of fossiliferous deposits thick enough to resist -future degradation, enormous intervals of time have elapsed between the -successive formations; that there has probably been more extinction during the -periods of subsidence, and more variation during the periods of elevation, and -during the latter the record will have been least perfectly kept; that each -single formation has not been continuously deposited; that the duration of each -formation is, perhaps, short compared with the average duration of specific -forms; that migration has played an important part in the first appearance of -new forms in any one area and formation; that widely ranging species are those -which have varied most, and have oftenest given rise to new species; and that -varieties have at first often been local. All these causes taken conjointly, -must have tended to make the geological record extremely imperfect, and will to -a large extent explain why we do not find interminable varieties, connecting -together all the extinct and existing forms of life by the finest graduated -steps. - -He who rejects these views on the nature of the geological record, will rightly -reject my whole theory. For he may ask in vain where are the numberless -transitional links which must formerly have connected the closely allied or -representative species, found in the several stages of the same great -formation. He may disbelieve in the enormous intervals of time which have -elapsed between our consecutive formations; he may overlook how important a -part migration must have played, when the formations of any one great region -alone, as that of Europe, are considered; he may urge the apparent, but often -falsely apparent, sudden coming in of whole groups of species. He may ask where -are the remains of those infinitely numerous organisms which must have existed -long before the first bed of the Silurian system was deposited: I can answer -this latter question only hypothetically, by saying that as far as we can see, -where our oceans now extend they have for an enormous period extended, and -where our oscillating continents now stand they have stood ever since the -Silurian epoch; but that long before that period, the world may have presented -a wholly different aspect; and that the older continents, formed of formations -older than any known to us, may now all be in a metamorphosed condition, or may -lie buried under the ocean. +types,”—on “this wonderful relationship in the same continent between +the dead and the living.” Professor Owen has subsequently extended the +same generalisation to the mammals of the Old World. We see the same law +in this author’s restorations of the extinct and gigantic birds of New +Zealand. We see it also in the birds of the caves of Brazil. Mr. +Woodward has shown that the same law holds good with sea-shells, but +from the wide distribution of most genera of molluscs, it is not well +displayed by them. Other cases could be added, as the relation between +the extinct and living land-shells of Madeira; and between the extinct +and living brackish-water shells of the Aralo-Caspian Sea. + +Now what does this remarkable law of the succession of the same types +within the same areas mean? He would be a bold man, who after comparing +the present climate of Australia and of parts of South America under the +same latitude, would attempt to account, on the one hand, by dissimilar +physical conditions for the dissimilarity of the inhabitants of these +two continents, and, on the other hand, by similarity of conditions, for +the uniformity of the same types in each during the later tertiary +periods. Nor can it be pretended that it is an immutable law that +marsupials should have been chiefly or solely produced in Australia; or +that Edentata and other American types should have been solely produced +in South America. For we know that Europe in ancient times was peopled +by numerous marsupials; and I have shown in the publications above +alluded to, that in America the law of distribution of terrestrial +mammals was formerly different from what it now is. North America +formerly partook strongly of the present character of the southern half +of the continent; and the southern half was formerly more closely +allied, than it is at present, to the northern half. In a similar +manner we know from Falconer and Cautley’s discoveries, that northern +India was formerly more closely related in its mammals to Africa than it +is at the present time. Analogous facts could be given in relation to +the distribution of marine animals. + +On the theory of descent with modification, the great law of the long +enduring, but not immutable, succession of the same types within the +same areas, is at once explained; for the inhabitants of each quarter of +the world will obviously tend to leave in that quarter, during the next +succeeding period of time, closely allied though in some degree modified +descendants. If the inhabitants of one continent formerly differed +greatly from those of another continent, so will their modified +descendants still differ in nearly the same manner and degree. But after +very long intervals of time and after great geographical changes, +permitting much inter-migration, the feebler will yield to the more +dominant forms, and there will be nothing immutable in the laws of past +and present distribution. + +It may be asked in ridicule, whether I suppose that the megatherium and +other allied huge monsters have left behind them in South America the +sloth, armadillo, and anteater, as their degenerate descendants. This +cannot for an instant be admitted. These huge animals have become wholly +extinct, and have left no progeny. But in the caves of Brazil, there are +many extinct species which are closely allied in size and in other +characters to the species still living in South America; and some of +these fossils may be the actual progenitors of living species. It must +not be forgotten that, on my theory, all the species of the same genus +have descended from some one species; so that if six genera, each having +eight species, be found in one geological formation, and in the next +succeeding formation there be six other allied or representative genera +with the same number of species, then we may conclude that only one +species of each of the six older genera has left modified descendants, +constituting the six new genera. The other seven species of the old +genera have all died out and have left no progeny. Or, which would +probably be a far commoner case, two or three species of two or three +alone of the six older genera will have been the parents of the six new +genera; the other old species and the other whole genera having become +utterly extinct. In failing orders, with the genera and species +decreasing in numbers, as apparently is the case of the Edentata of +South America, still fewer genera and species will have left modified +blood-descendants. + +Summary of the preceding and present Chapters.—I have attempted to show +that the geological record is extremely imperfect; that only a small +portion of the globe has been geologically explored with care; that only +certain classes of organic beings have been largely preserved in a +fossil state; that the number both of specimens and of species, +preserved in our museums, is absolutely as nothing compared with the +incalculable number of generations which must have passed away even +during a single formation; that, owing to subsidence being necessary for +the accumulation of fossiliferous deposits thick enough to resist future +degradation, enormous intervals of time have elapsed between the +successive formations; that there has probably been more extinction +during the periods of subsidence, and more variation during the periods +of elevation, and during the latter the record will have been least +perfectly kept; that each single formation has not been continuously +deposited; that the duration of each formation is, perhaps, short +compared with the average duration of specific forms; that migration has +played an important part in the first appearance of new forms in any one +area and formation; that widely ranging species are those which have +varied most, and have oftenest given rise to new species; and that +varieties have at first often been local. All these causes taken +conjointly, must have tended to make the geological record extremely +imperfect, and will to a large extent explain why we do not find +interminable varieties, connecting together all the extinct and existing +forms of life by the finest graduated steps. + +He who rejects these views on the nature of the geological record, will +rightly reject my whole theory. For he may ask in vain where are the +numberless transitional links which must formerly have connected the +closely allied or representative species, found in the several stages of +the same great formation. He may disbelieve in the enormous intervals of +time which have elapsed between our consecutive formations; he may +overlook how important a part migration must have played, when the +formations of any one great region alone, as that of Europe, are +considered; he may urge the apparent, but often falsely apparent, sudden +coming in of whole groups of species. He may ask where are the remains +of those infinitely numerous organisms which must have existed long +before the first bed of the Silurian system was deposited: I can answer +this latter question only hypothetically, by saying that as far as we +can see, where our oceans now extend they have for an enormous period +extended, and where our oscillating continents now stand they have stood +ever since the Silurian epoch; but that long before that period, the +world may have presented a wholly different aspect; and that the older +continents, formed of formations older than any known to us, may now all +be in a metamorphosed condition, or may lie buried under the ocean. Passing from these difficulties, all the other great leading facts in palæontology seem to me simply to follow on the theory of descent with -modification through natural selection. We can thus understand how it is that -new species come in slowly and successively; how species of different classes -do not necessarily change together, or at the same rate, or in the same degree; -yet in the long run that all undergo modification to some extent. The -extinction of old forms is the almost inevitable consequence of the production -of new forms. We can understand why when a species has once disappeared it -never reappears. Groups of species increase in numbers slowly, and endure for -unequal periods of time; for the process of modification is necessarily slow, -and depends on many complex contingencies. The dominant species of the larger +modification through natural selection. We can thus understand how it is +that new species come in slowly and successively; how species of +different classes do not necessarily change together, or at the same +rate, or in the same degree; yet in the long run that all undergo +modification to some extent. The extinction of old forms is the almost +inevitable consequence of the production of new forms. We can understand +why when a species has once disappeared it never reappears. Groups of +species increase in numbers slowly, and endure for unequal periods of +time; for the process of modification is necessarily slow, and depends +on many complex contingencies. The dominant species of the larger dominant groups tend to leave many modified descendants, and thus new -sub-groups and groups are formed. As these are formed, the species of the less -vigorous groups, from their inferiority inherited from a common progenitor, -tend to become extinct together, and to leave no modified offspring on the face -of the earth. But the utter extinction of a whole group of species may often be -a very slow process, from the survival of a few descendants, lingering in -protected and isolated situations. When a group has once wholly disappeared, it -does not reappear; for the link of generation has been broken. - -We can understand how the spreading of the dominant forms of life, which are -those that oftenest vary, will in the long run tend to people the world with -allied, but modified, descendants; and these will generally succeed in taking -the places of those groups of species which are their inferiors in the struggle -for existence. Hence, after long intervals of time, the productions of the -world will appear to have changed simultaneously. - -We can understand how it is that all the forms of life, ancient and recent, -make together one grand system; for all are connected by generation. We can -understand, from the continued tendency to divergence of character, why the -more ancient a form is, the more it generally differs from those now living. -Why ancient and extinct forms often tend to fill up gaps between existing -forms, sometimes blending two groups previously classed as distinct into one; -but more commonly only bringing them a little closer together. The more ancient -a form is, the more often, apparently, it displays characters in some degree -intermediate between groups now distinct; for the more ancient a form is, the -more nearly it will be related to, and consequently resemble, the common -progenitor of groups, since become widely divergent. Extinct forms are seldom -directly intermediate between existing forms; but are intermediate only by a -long and circuitous course through many extinct and very different forms. We -can clearly see why the organic remains of closely consecutive formations are -more closely allied to each other, than are those of remote formations; for the -forms are more closely linked together by generation: we can clearly see why -the remains of an intermediate formation are intermediate in character. - -The inhabitants of each successive period in the world’s history have beaten -their predecessors in the race for life, and are, in so far, higher in the -scale of nature; and this may account for that vague yet ill-defined sentiment, -felt by many palæontologists, that organisation on the whole has progressed. If -it should hereafter be proved that ancient animals resemble to a certain extent -the embryos of more recent animals of the same class, the fact will be -intelligible. The succession of the same types of structure within the same -areas during the later geological periods ceases to be mysterious, and is -simply explained by inheritance. - -If then the geological record be as imperfect as I believe it to be, and it may -at least be asserted that the record cannot be proved to be much more perfect, -the main objections to the theory of natural selection are greatly diminished -or disappear. On the other hand, all the chief laws of palæontology plainly -proclaim, as it seems to me, that species have been produced by ordinary -generation: old forms having been supplanted by new and improved forms of life, -produced by the laws of variation still acting round us, and preserved by -Natural Selection. - -CHAPTER XI. -GEOGRAPHICAL DISTRIBUTION. +sub-groups and groups are formed. As these are formed, the species of +the less vigorous groups, from their inferiority inherited from a common +progenitor, tend to become extinct together, and to leave no modified +offspring on the face of the earth. But the utter extinction of a whole +group of species may often be a very slow process, from the survival of +a few descendants, lingering in protected and isolated situations. When +a group has once wholly disappeared, it does not reappear; for the link +of generation has been broken. + +We can understand how the spreading of the dominant forms of life, which +are those that oftenest vary, will in the long run tend to people the +world with allied, but modified, descendants; and these will generally +succeed in taking the places of those groups of species which are their +inferiors in the struggle for existence. Hence, after long intervals of +time, the productions of the world will appear to have changed +simultaneously. + +We can understand how it is that all the forms of life, ancient and +recent, make together one grand system; for all are connected by +generation. We can understand, from the continued tendency to divergence +of character, why the more ancient a form is, the more it generally +differs from those now living. Why ancient and extinct forms often tend +to fill up gaps between existing forms, sometimes blending two groups +previously classed as distinct into one; but more commonly only bringing +them a little closer together. The more ancient a form is, the more +often, apparently, it displays characters in some degree intermediate +between groups now distinct; for the more ancient a form is, the more +nearly it will be related to, and consequently resemble, the common +progenitor of groups, since become widely divergent. Extinct forms are +seldom directly intermediate between existing forms; but are +intermediate only by a long and circuitous course through many extinct +and very different forms. We can clearly see why the organic remains of +closely consecutive formations are more closely allied to each other, +than are those of remote formations; for the forms are more closely +linked together by generation: we can clearly see why the remains of an +intermediate formation are intermediate in character. + +The inhabitants of each successive period in the world’s history have +beaten their predecessors in the race for life, and are, in so far, +higher in the scale of nature; and this may account for that vague yet +ill-defined sentiment, felt by many palæontologists, that organisation +on the whole has progressed. If it should hereafter be proved that +ancient animals resemble to a certain extent the embryos of more recent +animals of the same class, the fact will be intelligible. The succession +of the same types of structure within the same areas during the later +geological periods ceases to be mysterious, and is simply explained by +inheritance. + +If then the geological record be as imperfect as I believe it to be, and +it may at least be asserted that the record cannot be proved to be much +more perfect, the main objections to the theory of natural selection are +greatly diminished or disappear. On the other hand, all the chief laws +of palæontology plainly proclaim, as it seems to me, that species have +been produced by ordinary generation: old forms having been supplanted +by new and improved forms of life, produced by the laws of variation +still acting round us, and preserved by Natural Selection. + +CHAPTER XI. GEOGRAPHICAL DISTRIBUTION. Present distribution cannot be accounted for by differences in physical -conditions. Importance of barriers. Affinity of the productions of the same -continent. Centres of creation. Means of dispersal, by changes of climate and -of the level of the land, and by occasional means. Dispersal during the Glacial -period co-extensive with the world. - -In considering the distribution of organic beings over the face of the globe, -the first great fact which strikes us is, that neither the similarity nor the -dissimilarity of the inhabitants of various regions can be accounted for by -their climatal and other physical conditions. Of late, almost every author who -has studied the subject has come to this conclusion. The case of America alone -would almost suffice to prove its truth: for if we exclude the northern parts -where the circumpolar land is almost continuous, all authors agree that one of -the most fundamental divisions in geographical distribution is that between the -New and Old Worlds; yet if we travel over the vast American continent, from the -central parts of the United States to its extreme southern point, we meet with -the most diversified conditions; the most humid districts, arid deserts, lofty -mountains, grassy plains, forests, marshes, lakes, and great rivers, under -almost every temperature. There is hardly a climate or condition in the Old -World which cannot be paralleled in the New—at least as closely as the same -species generally require; for it is a most rare case to find a group of -organisms confined to any small spot, having conditions peculiar in only a -slight degree; for instance, small areas in the Old World could be pointed out -hotter than any in the New World, yet these are not inhabited by a peculiar -fauna or flora. Notwithstanding this parallelism in the conditions of the Old -and New Worlds, how widely different are their living productions! - -In the southern hemisphere, if we compare large tracts of land in Australia, -South Africa, and western South America, between latitudes 25° and 35°, we -shall find parts extremely similar in all their conditions, yet it would not be -possible to point out three faunas and floras more utterly dissimilar. Or again -we may compare the productions of South America south of lat. 35° with those -north of 25°, which consequently inhabit a considerably different climate, and -they will be found incomparably more closely related to each other, than they -are to the productions of Australia or Africa under nearly the same climate. -Analogous facts could be given with respect to the inhabitants of the sea. - -A second great fact which strikes us in our general review is, that barriers of -any kind, or obstacles to free migration, are related in a close and important -manner to the differences between the productions of various regions. We see -this in the great difference of nearly all the terrestrial productions of the -New and Old Worlds, excepting in the northern parts, where the land almost -joins, and where, under a slightly different climate, there might have been -free migration for the northern temperate forms, as there now is for the -strictly arctic productions. We see the same fact in the great difference -between the inhabitants of Australia, Africa, and South America under the same -latitude: for these countries are almost as much isolated from each other as is -possible. On each continent, also, we see the same fact; for on the opposite -sides of lofty and continuous mountain-ranges, and of great deserts, and +conditions. Importance of barriers. Affinity of the productions of the +same continent. Centres of creation. Means of dispersal, by changes of +climate and of the level of the land, and by occasional means. Dispersal +during the Glacial period co-extensive with the world. + +In considering the distribution of organic beings over the face of the +globe, the first great fact which strikes us is, that neither the +similarity nor the dissimilarity of the inhabitants of various regions +can be accounted for by their climatal and other physical conditions. Of +late, almost every author who has studied the subject has come to this +conclusion. The case of America alone would almost suffice to prove its +truth: for if we exclude the northern parts where the circumpolar land +is almost continuous, all authors agree that one of the most fundamental +divisions in geographical distribution is that between the New and Old +Worlds; yet if we travel over the vast American continent, from the +central parts of the United States to its extreme southern point, we +meet with the most diversified conditions; the most humid districts, +arid deserts, lofty mountains, grassy plains, forests, marshes, lakes, +and great rivers, under almost every temperature. There is hardly a +climate or condition in the Old World which cannot be paralleled in the +New—at least as closely as the same species generally require; for it is +a most rare case to find a group of organisms confined to any small +spot, having conditions peculiar in only a slight degree; for instance, +small areas in the Old World could be pointed out hotter than any in the +New World, yet these are not inhabited by a peculiar fauna or flora. +Notwithstanding this parallelism in the conditions of the Old and New +Worlds, how widely different are their living productions! + +In the southern hemisphere, if we compare large tracts of land in +Australia, South Africa, and western South America, between latitudes +25° and 35°, we shall find parts extremely similar in all their +conditions, yet it would not be possible to point out three faunas and +floras more utterly dissimilar. Or again we may compare the productions +of South America south of lat. 35° with those north of 25°, which +consequently inhabit a considerably different climate, and they will be +found incomparably more closely related to each other, than they are to +the productions of Australia or Africa under nearly the same climate. +Analogous facts could be given with respect to the inhabitants of the +sea. + +A second great fact which strikes us in our general review is, that +barriers of any kind, or obstacles to free migration, are related in a +close and important manner to the differences between the productions of +various regions. We see this in the great difference of nearly all the +terrestrial productions of the New and Old Worlds, excepting in the +northern parts, where the land almost joins, and where, under a slightly +different climate, there might have been free migration for the northern +temperate forms, as there now is for the strictly arctic productions. We +see the same fact in the great difference between the inhabitants of +Australia, Africa, and South America under the same latitude: for these +countries are almost as much isolated from each other as is possible. On +each continent, also, we see the same fact; for on the opposite sides of +lofty and continuous mountain-ranges, and of great deserts, and sometimes even of large rivers, we find different productions; though as mountain chains, deserts, etc., are not as impassable, or likely to have -endured so long as the oceans separating continents, the differences are very -inferior in degree to those characteristic of distinct continents. +endured so long as the oceans separating continents, the differences are +very inferior in degree to those characteristic of distinct continents. Turning to the sea, we find the same law. No two marine faunas are more -distinct, with hardly a fish, shell, or crab in common, than those of the -eastern and western shores of South and Central America; yet these great faunas -are separated only by the narrow, but impassable, isthmus of Panama. Westward -of the shores of America, a wide space of open ocean extends, with not an -island as a halting-place for emigrants; here we have a barrier of another -kind, and as soon as this is passed we meet in the eastern islands of the -Pacific, with another and totally distinct fauna. So that here three marine -faunas range far northward and southward, in parallel lines not far from each -other, under corresponding climates; but from being separated from each other -by impassable barriers, either of land or open sea, they are wholly distinct. -On the other hand, proceeding still further westward from the eastern islands -of the tropical parts of the Pacific, we encounter no impassable barriers, and -we have innumerable islands as halting-places, until after travelling over a -hemisphere we come to the shores of Africa; and over this vast space we meet -with no well-defined and distinct marine faunas. Although hardly one shell, -crab or fish is common to the above-named three approximate faunas of Eastern -and Western America and the eastern Pacific islands, yet many fish range from -the Pacific into the Indian Ocean, and many shells are common to the eastern -islands of the Pacific and the eastern shores of Africa, on almost exactly -opposite meridians of longitude. +distinct, with hardly a fish, shell, or crab in common, than those of +the eastern and western shores of South and Central America; yet these +great faunas are separated only by the narrow, but impassable, isthmus +of Panama. Westward of the shores of America, a wide space of open ocean +extends, with not an island as a halting-place for emigrants; here we +have a barrier of another kind, and as soon as this is passed we meet in +the eastern islands of the Pacific, with another and totally distinct +fauna. So that here three marine faunas range far northward and +southward, in parallel lines not far from each other, under +corresponding climates; but from being separated from each other by +impassable barriers, either of land or open sea, they are wholly +distinct. On the other hand, proceeding still further westward from the +eastern islands of the tropical parts of the Pacific, we encounter no +impassable barriers, and we have innumerable islands as halting-places, +until after travelling over a hemisphere we come to the shores of +Africa; and over this vast space we meet with no well-defined and +distinct marine faunas. Although hardly one shell, crab or fish is +common to the above-named three approximate faunas of Eastern and +Western America and the eastern Pacific islands, yet many fish range +from the Pacific into the Indian Ocean, and many shells are common to +the eastern islands of the Pacific and the eastern shores of Africa, on +almost exactly opposite meridians of longitude. A third great fact, partly included in the foregoing statements, is the -affinity of the productions of the same continent or sea, though the species -themselves are distinct at different points and stations. It is a law of the -widest generality, and every continent offers innumerable instances. -Nevertheless the naturalist in travelling, for instance, from north to south -never fails to be struck by the manner in which successive groups of beings, -specifically distinct, yet clearly related, replace each other. He hears from -closely allied, yet distinct kinds of birds, notes nearly similar, and sees -their nests similarly constructed, but not quite alike, with eggs coloured in -nearly the same manner. The plains near the Straits of Magellan are inhabited -by one species of Rhea (American ostrich), and northward the plains of La Plata -by another species of the same genus; and not by a true ostrich or emeu, like -those found in Africa and Australia under the same latitude. On these same -plains of La Plata, we see the agouti and bizcacha, animals having nearly the -same habits as our hares and rabbits and belonging to the same order of -Rodents, but they plainly display an American type of structure. We ascend the -lofty peaks of the Cordillera and we find an alpine species of bizcacha; we -look to the waters, and we do not find the beaver or musk-rat, but the coypu -and capybara, rodents of the American type. Innumerable other instances could -be given. If we look to the islands off the American shore, however much they -may differ in geological structure, the inhabitants, though they may be all -peculiar species, are essentially American. We may look back to past ages, as -shown in the last chapter, and we find American types then prevalent on the -American continent and in the American seas. We see in these facts some deep -organic bond, prevailing throughout space and time, over the same areas of land -and water, and independent of their physical conditions. The naturalist must -feel little curiosity, who is not led to inquire what this bond is. - -This bond, on my theory, is simply inheritance, that cause which alone, as far -as we positively know, produces organisms quite like, or, as we see in the case -of varieties nearly like each other. The dissimilarity of the inhabitants of -different regions may be attributed to modification through natural selection, -and in a quite subordinate degree to the direct influence of different physical -conditions. The degree of dissimilarity will depend on the migration of the -more dominant forms of life from one region into another having been effected -with more or less ease, at periods more or less remote;—on the nature and -number of the former immigrants;—and on their action and reaction, in their -mutual struggles for life;—the relation of organism to organism being, as I -have already often remarked, the most important of all relations. Thus the high -importance of barriers comes into play by checking migration; as does time for -the slow process of modification through natural selection. Widely-ranging -species, abounding in individuals, which have already triumphed over many -competitors in their own widely-extended homes will have the best chance of -seizing on new places, when they spread into new countries. In their new homes -they will be exposed to new conditions, and will frequently undergo further +affinity of the productions of the same continent or sea, though the +species themselves are distinct at different points and stations. It is +a law of the widest generality, and every continent offers innumerable +instances. Nevertheless the naturalist in travelling, for instance, +from north to south never fails to be struck by the manner in which +successive groups of beings, specifically distinct, yet clearly related, +replace each other. He hears from closely allied, yet distinct kinds of +birds, notes nearly similar, and sees their nests similarly constructed, +but not quite alike, with eggs coloured in nearly the same manner. The +plains near the Straits of Magellan are inhabited by one species of Rhea +(American ostrich), and northward the plains of La Plata by another +species of the same genus; and not by a true ostrich or emeu, like those +found in Africa and Australia under the same latitude. On these same +plains of La Plata, we see the agouti and bizcacha, animals having +nearly the same habits as our hares and rabbits and belonging to the +same order of Rodents, but they plainly display an American type of +structure. We ascend the lofty peaks of the Cordillera and we find an +alpine species of bizcacha; we look to the waters, and we do not find +the beaver or musk-rat, but the coypu and capybara, rodents of the +American type. Innumerable other instances could be given. If we look to +the islands off the American shore, however much they may differ in +geological structure, the inhabitants, though they may be all peculiar +species, are essentially American. We may look back to past ages, as +shown in the last chapter, and we find American types then prevalent on +the American continent and in the American seas. We see in these facts +some deep organic bond, prevailing throughout space and time, over the +same areas of land and water, and independent of their physical +conditions. The naturalist must feel little curiosity, who is not led to +inquire what this bond is. + +This bond, on my theory, is simply inheritance, that cause which alone, +as far as we positively know, produces organisms quite like, or, as we +see in the case of varieties nearly like each other. The dissimilarity +of the inhabitants of different regions may be attributed to +modification through natural selection, and in a quite subordinate +degree to the direct influence of different physical conditions. The +degree of dissimilarity will depend on the migration of the more +dominant forms of life from one region into another having been effected +with more or less ease, at periods more or less remote;—on the nature +and number of the former immigrants;—and on their action and reaction, +in their mutual struggles for life;—the relation of organism to organism +being, as I have already often remarked, the most important of all +relations. Thus the high importance of barriers comes into play by +checking migration; as does time for the slow process of modification +through natural selection. Widely-ranging species, abounding in +individuals, which have already triumphed over many competitors in their +own widely-extended homes will have the best chance of seizing on new +places, when they spread into new countries. In their new homes they +will be exposed to new conditions, and will frequently undergo further modification and improvement; and thus they will become still further -victorious, and will produce groups of modified descendants. On this principle -of inheritance with modification, we can understand how it is that sections of -genera, whole genera, and even families are confined to the same areas, as is -so commonly and notoriously the case. +victorious, and will produce groups of modified descendants. On this +principle of inheritance with modification, we can understand how it is +that sections of genera, whole genera, and even families are confined to +the same areas, as is so commonly and notoriously the case. I believe, as was remarked in the last chapter, in no law of necessary -development. As the variability of each species is an independent property, and -will be taken advantage of by natural selection, only so far as it profits the -individual in its complex struggle for life, so the degree of modification in -different species will be no uniform quantity. If, for instance, a number of -species, which stand in direct competition with each other, migrate in a body -into a new and afterwards isolated country, they will be little liable to -modification; for neither migration nor isolation in themselves can do -anything. These principles come into play only by bringing organisms into new -relations with each other, and in a lesser degree with the surrounding physical -conditions. As we have seen in the last chapter that some forms have retained -nearly the same character from an enormously remote geological period, so -certain species have migrated over vast spaces, and have not become greatly -modified. - -On these views, it is obvious, that the several species of the same genus, -though inhabiting the most distant quarters of the world, must originally have -proceeded from the same source, as they have descended from the same -progenitor. In the case of those species, which have undergone during whole -geological periods but little modification, there is not much difficulty in -believing that they may have migrated from the same region; for during the vast -geographical and climatal changes which will have supervened since ancient -times, almost any amount of migration is possible. But in many other cases, in -which we have reason to believe that the species of a genus have been produced -within comparatively recent times, there is great difficulty on this head. It -is also obvious that the individuals of the same species, though now inhabiting -distant and isolated regions, must have proceeded from one spot, where their -parents were first produced: for, as explained in the last chapter, it is -incredible that individuals identically the same should ever have been produced -through natural selection from parents specifically distinct. +development. As the variability of each species is an independent +property, and will be taken advantage of by natural selection, only so +far as it profits the individual in its complex struggle for life, so +the degree of modification in different species will be no uniform +quantity. If, for instance, a number of species, which stand in direct +competition with each other, migrate in a body into a new and afterwards +isolated country, they will be little liable to modification; for +neither migration nor isolation in themselves can do anything. These +principles come into play only by bringing organisms into new relations +with each other, and in a lesser degree with the surrounding physical +conditions. As we have seen in the last chapter that some forms have +retained nearly the same character from an enormously remote geological +period, so certain species have migrated over vast spaces, and have not +become greatly modified. + +On these views, it is obvious, that the several species of the same +genus, though inhabiting the most distant quarters of the world, must +originally have proceeded from the same source, as they have descended +from the same progenitor. In the case of those species, which have +undergone during whole geological periods but little modification, there +is not much difficulty in believing that they may have migrated from the +same region; for during the vast geographical and climatal changes which +will have supervened since ancient times, almost any amount of migration +is possible. But in many other cases, in which we have reason to believe +that the species of a genus have been produced within comparatively +recent times, there is great difficulty on this head. It is also obvious +that the individuals of the same species, though now inhabiting distant +and isolated regions, must have proceeded from one spot, where their +parents were first produced: for, as explained in the last chapter, it +is incredible that individuals identically the same should ever have +been produced through natural selection from parents specifically +distinct. We are thus brought to the question which has been largely discussed by -naturalists, namely, whether species have been created at one or more points of -the earth’s surface. Undoubtedly there are very many cases of extreme -difficulty, in understanding how the same species could possibly have migrated -from some one point to the several distant and isolated points, where now -found. Nevertheless the simplicity of the view that each species was first -produced within a single region captivates the mind. He who rejects it, rejects -the vera causa of ordinary generation with subsequent migration, and calls in -the agency of a miracle. It is universally admitted, that in most cases the -area inhabited by a species is continuous; and when a plant or animal inhabits -two points so distant from each other, or with an interval of such a nature, -that the space could not be easily passed over by migration, the fact is given -as something remarkable and exceptional. The capacity of migrating across the -sea is more distinctly limited in terrestrial mammals, than perhaps in any -other organic beings; and, accordingly, we find no inexplicable cases of the -same mammal inhabiting distant points of the world. No geologist will feel any -difficulty in such cases as Great Britain having been formerly united to -Europe, and consequently possessing the same quadrupeds. But if the same -species can be produced at two separate points, why do we not find a single -mammal common to Europe and Australia or South America? The conditions of life -are nearly the same, so that a multitude of European animals and plants have -become naturalised in America and Australia; and some of the aboriginal plants -are identically the same at these distant points of the northern and southern -hemispheres? The answer, as I believe, is, that mammals have not been able to -migrate, whereas some plants, from their varied means of dispersal, have -migrated across the vast and broken interspace. The great and striking -influence which barriers of every kind have had on distribution, is -intelligible only on the view that the great majority of species have been -produced on one side alone, and have not been able to migrate to the other -side. Some few families, many sub-families, very many genera, and a still -greater number of sections of genera are confined to a single region; and it -has been observed by several naturalists, that the most natural genera, or -those genera in which the species are most closely related to each other, are -generally local, or confined to one area. What a strange anomaly it would be, -if, when coming one step lower in the series, to the individuals of the same -species, a directly opposite rule prevailed; and species were not local, but -had been produced in two or more distinct areas! - -Hence it seems to me, as it has to many other naturalists, that the view of -each species having been produced in one area alone, and having subsequently -migrated from that area as far as its powers of migration and subsistence under -past and present conditions permitted, is the most probable. Undoubtedly many -cases occur, in which we cannot explain how the same species could have passed -from one point to the other. But the geographical and climatal changes, which -have certainly occurred within recent geological times, must have interrupted -or rendered discontinuous the formerly continuous range of many species. So -that we are reduced to consider whether the exceptions to continuity of range -are so numerous and of so grave a nature, that we ought to give up the belief, -rendered probable by general considerations, that each species has been -produced within one area, and has migrated thence as far as it could. It would -be hopelessly tedious to discuss all the exceptional cases of the same species, -now living at distant and separated points; nor do I for a moment pretend that -any explanation could be offered of many such cases. But after some preliminary -remarks, I will discuss a few of the most striking classes of facts; namely, -the existence of the same species on the summits of distant mountain-ranges, -and at distant points in the arctic and antarctic regions; and secondly (in the -following chapter), the wide distribution of freshwater productions; and -thirdly, the occurrence of the same terrestrial species on islands and on the -mainland, though separated by hundreds of miles of open sea. If the existence -of the same species at distant and isolated points of the earth’s surface, can -in many instances be explained on the view of each species having migrated from -a single birthplace; then, considering our ignorance with respect to former -climatal and geographical changes and various occasional means of transport, -the belief that this has been the universal law, seems to me incomparably the -safest. - -In discussing this subject, we shall be enabled at the same time to consider a -point equally important for us, namely, whether the several distinct species of -a genus, which on my theory have all descended from a common progenitor, can -have migrated (undergoing modification during some part of their migration) -from the area inhabited by their progenitor. If it can be shown to be almost -invariably the case, that a region, of which most of its inhabitants are -closely related to, or belong to the same genera with the species of a second -region, has probably received at some former period immigrants from this other -region, my theory will be strengthened; for we can clearly understand, on the -principle of modification, why the inhabitants of a region should be related to -those of another region, whence it has been stocked. A volcanic island, for -instance, upheaved and formed at the distance of a few hundreds of miles from a -continent, would probably receive from it in the course of time a few -colonists, and their descendants, though modified, would still be plainly -related by inheritance to the inhabitants of the continent. Cases of this -nature are common, and are, as we shall hereafter more fully see, inexplicable -on the theory of independent creation. This view of the relation of species in -one region to those in another, does not differ much (by substituting the word -variety for species) from that lately advanced in an ingenious paper by Mr. -Wallace, in which he concludes, that “every species has come into existence -coincident both in space and time with a pre-existing closely allied species.” -And I now know from correspondence, that this coincidence he attributes to -generation with modification. +naturalists, namely, whether species have been created at one or more +points of the earth’s surface. Undoubtedly there are very many cases of +extreme difficulty, in understanding how the same species could possibly +have migrated from some one point to the several distant and isolated +points, where now found. Nevertheless the simplicity of the view that +each species was first produced within a single region captivates the +mind. He who rejects it, rejects the vera causa of ordinary generation +with subsequent migration, and calls in the agency of a miracle. It is +universally admitted, that in most cases the area inhabited by a species +is continuous; and when a plant or animal inhabits two points so distant +from each other, or with an interval of such a nature, that the space +could not be easily passed over by migration, the fact is given as +something remarkable and exceptional. The capacity of migrating across +the sea is more distinctly limited in terrestrial mammals, than perhaps +in any other organic beings; and, accordingly, we find no inexplicable +cases of the same mammal inhabiting distant points of the world. No +geologist will feel any difficulty in such cases as Great Britain having +been formerly united to Europe, and consequently possessing the same +quadrupeds. But if the same species can be produced at two separate +points, why do we not find a single mammal common to Europe and +Australia or South America? The conditions of life are nearly the same, +so that a multitude of European animals and plants have become +naturalised in America and Australia; and some of the aboriginal plants +are identically the same at these distant points of the northern and +southern hemispheres? The answer, as I believe, is, that mammals have +not been able to migrate, whereas some plants, from their varied means +of dispersal, have migrated across the vast and broken interspace. The +great and striking influence which barriers of every kind have had on +distribution, is intelligible only on the view that the great majority +of species have been produced on one side alone, and have not been able +to migrate to the other side. Some few families, many sub-families, very +many genera, and a still greater number of sections of genera are +confined to a single region; and it has been observed by several +naturalists, that the most natural genera, or those genera in which the +species are most closely related to each other, are generally local, or +confined to one area. What a strange anomaly it would be, if, when +coming one step lower in the series, to the individuals of the same +species, a directly opposite rule prevailed; and species were not local, +but had been produced in two or more distinct areas! + +Hence it seems to me, as it has to many other naturalists, that the view +of each species having been produced in one area alone, and having +subsequently migrated from that area as far as its powers of migration +and subsistence under past and present conditions permitted, is the most +probable. Undoubtedly many cases occur, in which we cannot explain how +the same species could have passed from one point to the other. But the +geographical and climatal changes, which have certainly occurred within +recent geological times, must have interrupted or rendered discontinuous +the formerly continuous range of many species. So that we are reduced to +consider whether the exceptions to continuity of range are so numerous +and of so grave a nature, that we ought to give up the belief, rendered +probable by general considerations, that each species has been produced +within one area, and has migrated thence as far as it could. It would be +hopelessly tedious to discuss all the exceptional cases of the same +species, now living at distant and separated points; nor do I for a +moment pretend that any explanation could be offered of many such cases. +But after some preliminary remarks, I will discuss a few of the most +striking classes of facts; namely, the existence of the same species on +the summits of distant mountain-ranges, and at distant points in the +arctic and antarctic regions; and secondly (in the following chapter), +the wide distribution of freshwater productions; and thirdly, the +occurrence of the same terrestrial species on islands and on the +mainland, though separated by hundreds of miles of open sea. If the +existence of the same species at distant and isolated points of the +earth’s surface, can in many instances be explained on the view of each +species having migrated from a single birthplace; then, considering our +ignorance with respect to former climatal and geographical changes and +various occasional means of transport, the belief that this has been the +universal law, seems to me incomparably the safest. + +In discussing this subject, we shall be enabled at the same time to +consider a point equally important for us, namely, whether the several +distinct species of a genus, which on my theory have all descended from +a common progenitor, can have migrated (undergoing modification during +some part of their migration) from the area inhabited by their +progenitor. If it can be shown to be almost invariably the case, that a +region, of which most of its inhabitants are closely related to, or +belong to the same genera with the species of a second region, has +probably received at some former period immigrants from this other +region, my theory will be strengthened; for we can clearly understand, +on the principle of modification, why the inhabitants of a region should +be related to those of another region, whence it has been stocked. A +volcanic island, for instance, upheaved and formed at the distance of a +few hundreds of miles from a continent, would probably receive from it +in the course of time a few colonists, and their descendants, though +modified, would still be plainly related by inheritance to the +inhabitants of the continent. Cases of this nature are common, and are, +as we shall hereafter more fully see, inexplicable on the theory of +independent creation. This view of the relation of species in one region +to those in another, does not differ much (by substituting the word +variety for species) from that lately advanced in an ingenious paper by +Mr. Wallace, in which he concludes, that “every species has come into +existence coincident both in space and time with a pre-existing closely +allied species.” And I now know from correspondence, that this +coincidence he attributes to generation with modification. The previous remarks on “single and multiple centres of creation” do not -directly bear on another allied question,—namely whether all the individuals of -the same species have descended from a single pair, or single hermaphrodite, or -whether, as some authors suppose, from many individuals simultaneously created. -With those organic beings which never intercross (if such exist), the species, -on my theory, must have descended from a succession of improved varieties, -which will never have blended with other individuals or varieties, but will -have supplanted each other; so that, at each successive stage of modification -and improvement, all the individuals of each variety will have descended from a -single parent. But in the majority of cases, namely, with all organisms which -habitually unite for each birth, or which often intercross, I believe that -during the slow process of modification the individuals of the species will -have been kept nearly uniform by intercrossing; so that many individuals will -have gone on simultaneously changing, and the whole amount of modification will -not have been due, at each stage, to descent from a single parent. To -illustrate what I mean: our English racehorses differ slightly from the horses -of every other breed; but they do not owe their difference and superiority to -descent from any single pair, but to continued care in selecting and training -many individuals during many generations. +directly bear on another allied question,—namely whether all the +individuals of the same species have descended from a single pair, or +single hermaphrodite, or whether, as some authors suppose, from many +individuals simultaneously created. With those organic beings which +never intercross (if such exist), the species, on my theory, must have +descended from a succession of improved varieties, which will never have +blended with other individuals or varieties, but will have supplanted +each other; so that, at each successive stage of modification and +improvement, all the individuals of each variety will have descended +from a single parent. But in the majority of cases, namely, with all +organisms which habitually unite for each birth, or which often +intercross, I believe that during the slow process of modification the +individuals of the species will have been kept nearly uniform by +intercrossing; so that many individuals will have gone on simultaneously +changing, and the whole amount of modification will not have been due, +at each stage, to descent from a single parent. To illustrate what I +mean: our English racehorses differ slightly from the horses of every +other breed; but they do not owe their difference and superiority to +descent from any single pair, but to continued care in selecting and +training many individuals during many generations. Before discussing the three classes of facts, which I have selected as -presenting the greatest amount of difficulty on the theory of “single centres -of creation,” I must say a few words on the means of dispersal. - -Means of Dispersal.—Sir C. Lyell and other authors have ably treated this -subject. I can give here only the briefest abstract of the more important -facts. Change of climate must have had a powerful influence on migration: a -region when its climate was different may have been a high road for migration, -but now be impassable; I shall, however, presently have to discuss this branch -of the subject in some detail. Changes of level in the land must also have been -highly influential: a narrow isthmus now separates two marine faunas; submerge -it, or let it formerly have been submerged, and the two faunas will now blend -or may formerly have blended: where the sea now extends, land may at a former -period have connected islands or possibly even continents together, and thus +presenting the greatest amount of difficulty on the theory of “single +centres of creation,” I must say a few words on the means of dispersal. + +Means of Dispersal.—Sir C. Lyell and other authors have ably treated +this subject. I can give here only the briefest abstract of the more +important facts. Change of climate must have had a powerful influence on +migration: a region when its climate was different may have been a high +road for migration, but now be impassable; I shall, however, presently +have to discuss this branch of the subject in some detail. Changes of +level in the land must also have been highly influential: a narrow +isthmus now separates two marine faunas; submerge it, or let it formerly +have been submerged, and the two faunas will now blend or may formerly +have blended: where the sea now extends, land may at a former period +have connected islands or possibly even continents together, and thus have allowed terrestrial productions to pass from one to the other. No -geologist will dispute that great mutations of level have occurred within the -period of existing organisms. Edward Forbes insisted that all the islands in -the Atlantic must recently have been connected with Europe or Africa, and -Europe likewise with America. Other authors have thus hypothetically bridged -over every ocean, and have united almost every island to some mainland. If -indeed the arguments used by Forbes are to be trusted, it must be admitted that -scarcely a single island exists which has not recently been united to some -continent. This view cuts the Gordian knot of the dispersal of the same species -to the most distant points, and removes many a difficulty: but to the best of -my judgment we are not authorized in admitting such enormous geographical -changes within the period of existing species. It seems to me that we have -abundant evidence of great oscillations of level in our continents; but not of -such vast changes in their position and extension, as to have united them -within the recent period to each other and to the several intervening oceanic -islands. I freely admit the former existence of many islands, now buried -beneath the sea, which may have served as halting places for plants and for -many animals during their migration. In the coral-producing oceans such sunken -islands are now marked, as I believe, by rings of coral or atolls standing over -them. Whenever it is fully admitted, as I believe it will some day be, that -each species has proceeded from a single birthplace, and when in the course of -time we know something definite about the means of distribution, we shall be -enabled to speculate with security on the former extension of the land. But I -do not believe that it will ever be proved that within the recent period -continents which are now quite separate, have been continuously, or almost -continuously, united with each other, and with the many existing oceanic -islands. Several facts in distribution,—such as the great difference in the -marine faunas on the opposite sides of almost every continent,—the close -relation of the tertiary inhabitants of several lands and even seas to their -present inhabitants,—a certain degree of relation (as we shall hereafter see) -between the distribution of mammals and the depth of the sea,—these and other -such facts seem to me opposed to the admission of such prodigious geographical -revolutions within the recent period, as are necessitated on the view advanced -by Forbes and admitted by his many followers. The nature and relative -proportions of the inhabitants of oceanic islands likewise seem to me opposed -to the belief of their former continuity with continents. Nor does their almost -universally volcanic composition favour the admission that they are the wrecks -of sunken continents;—if they had originally existed as mountain-ranges on the -land, some at least of the islands would have been formed, like other -mountain-summits, of granite, metamorphic schists, old fossiliferous or other -such rocks, instead of consisting of mere piles of volcanic matter. - -I must now say a few words on what are called accidental means, but which more -properly might be called occasional means of distribution. I shall here confine -myself to plants. In botanical works, this or that plant is stated to be ill -adapted for wide dissemination; but for transport across the sea, the greater -or less facilities may be said to be almost wholly unknown. Until I tried, with -Mr. Berkeley’s aid, a few experiments, it was not even known how far seeds -could resist the injurious action of sea-water. To my surprise I found that out -of 87 kinds, 64 germinated after an immersion of 28 days, and a few survived an -immersion of 137 days. For convenience sake I chiefly tried small seeds, -without the capsule or fruit; and as all of these sank in a few days, they -could not be floated across wide spaces of the sea, whether or not they were -injured by the salt-water. Afterwards I tried some larger fruits, capsules, -etc., and some of these floated for a long time. It is well known what a -difference there is in the buoyancy of green and seasoned timber; and it -occurred to me that floods might wash down plants or branches, and that these -might be dried on the banks, and then by a fresh rise in the stream be washed -into the sea. Hence I was led to dry stems and branches of 94 plants with ripe -fruit, and to place them on sea water. The majority sank quickly, but some -which whilst green floated for a very short time, when dried floated much -longer; for instance, ripe hazel-nuts sank immediately, but when dried, they -floated for 90 days and afterwards when planted they germinated; an asparagus -plant with ripe berries floated for 23 days, when dried it floated for 85 days, -and the seeds afterwards germinated: the ripe seeds of Helosciadium sank in two -days, when dried they floated for above 90 days, and afterwards germinated. -Altogether out of the 94 dried plants, 18 floated for above 28 days, and some -of the 18 floated for a very much longer period. So that as 64/87 seeds -germinated after an immersion of 28 days; and as 18/94 plants with ripe fruit -(but not all the same species as in the foregoing experiment) floated, after -being dried, for above 28 days, as far as we may infer anything from these -scanty facts, we may conclude that the seeds of 14/100 plants of any country -might be floated by sea-currents during 28 days, and would retain their power -of germination. In Johnston’s Physical Atlas, the average rate of the several -Atlantic currents is 33 miles per diem (some currents running at the rate of 60 -miles per diem); on this average, the seeds of 14/100 plants belonging to one -country might be floated across 924 miles of sea to another country; and when -stranded, if blown to a favourable spot by an inland gale, they would -germinate. - -Subsequently to my experiments, M. Martens tried similar ones, but in a much -better manner, for he placed the seeds in a box in the actual sea, so that they -were alternately wet and exposed to the air like really floating plants. He -tried 98 seeds, mostly different from mine; but he chose many large fruits and -likewise seeds from plants which live near the sea; and this would have -favoured the average length of their flotation and of their resistance to the -injurious action of the salt-water. On the other hand he did not previously dry -the plants or branches with the fruit; and this, as we have seen, would have -caused some of them to have floated much longer. The result was that 18/98 of -his seeds floated for 42 days, and were then capable of germination. But I do -not doubt that plants exposed to the waves would float for a less time than -those protected from violent movement as in our experiments. Therefore it would -perhaps be safer to assume that the seeds of about 10/100 plants of a flora, -after having been dried, could be floated across a space of sea 900 miles in -width, and would then germinate. The fact of the larger fruits often floating -longer than the small, is interesting; as plants with large seeds or fruit -could hardly be transported by any other means; and Alph. de Candolle has shown -that such plants generally have restricted ranges. - -But seeds may be occasionally transported in another manner. Drift timber is -thrown up on most islands, even on those in the midst of the widest oceans; and -the natives of the coral-islands in the Pacific, procure stones for their -tools, solely from the roots of drifted trees, these stones being a valuable -royal tax. I find on examination, that when irregularly shaped stones are -embedded in the roots of trees, small parcels of earth are very frequently -enclosed in their interstices and behind them,—so perfectly that not a particle -could be washed away in the longest transport: out of one small portion of -earth thus completely enclosed by wood in an oak about 50 years old, three -dicotyledonous plants germinated: I am certain of the accuracy of this -observation. Again, I can show that the carcasses of birds, when floating on -the sea, sometimes escape being immediately devoured; and seeds of many kinds -in the crops of floating birds long retain their vitality: peas and vetches, -for instance, are killed by even a few days’ immersion in sea-water; but some -taken out of the crop of a pigeon, which had floated on artificial salt-water -for 30 days, to my surprise nearly all germinated. +geologist will dispute that great mutations of level have occurred +within the period of existing organisms. Edward Forbes insisted that all +the islands in the Atlantic must recently have been connected with +Europe or Africa, and Europe likewise with America. Other authors have +thus hypothetically bridged over every ocean, and have united almost +every island to some mainland. If indeed the arguments used by Forbes +are to be trusted, it must be admitted that scarcely a single island +exists which has not recently been united to some continent. This view +cuts the Gordian knot of the dispersal of the same species to the most +distant points, and removes many a difficulty: but to the best of my +judgment we are not authorized in admitting such enormous geographical +changes within the period of existing species. It seems to me that we +have abundant evidence of great oscillations of level in our continents; +but not of such vast changes in their position and extension, as to have +united them within the recent period to each other and to the several +intervening oceanic islands. I freely admit the former existence of many +islands, now buried beneath the sea, which may have served as halting +places for plants and for many animals during their migration. In the +coral-producing oceans such sunken islands are now marked, as I believe, +by rings of coral or atolls standing over them. Whenever it is fully +admitted, as I believe it will some day be, that each species has +proceeded from a single birthplace, and when in the course of time we +know something definite about the means of distribution, we shall be +enabled to speculate with security on the former extension of the land. +But I do not believe that it will ever be proved that within the recent +period continents which are now quite separate, have been continuously, +or almost continuously, united with each other, and with the many +existing oceanic islands. Several facts in distribution,—such as the +great difference in the marine faunas on the opposite sides of almost +every continent,—the close relation of the tertiary inhabitants of +several lands and even seas to their present inhabitants,—a certain +degree of relation (as we shall hereafter see) between the distribution +of mammals and the depth of the sea,—these and other such facts seem to +me opposed to the admission of such prodigious geographical revolutions +within the recent period, as are necessitated on the view advanced by +Forbes and admitted by his many followers. The nature and relative +proportions of the inhabitants of oceanic islands likewise seem to me +opposed to the belief of their former continuity with continents. Nor +does their almost universally volcanic composition favour the admission +that they are the wrecks of sunken continents;—if they had originally +existed as mountain-ranges on the land, some at least of the islands +would have been formed, like other mountain-summits, of granite, +metamorphic schists, old fossiliferous or other such rocks, instead of +consisting of mere piles of volcanic matter. + +I must now say a few words on what are called accidental means, but +which more properly might be called occasional means of distribution. I +shall here confine myself to plants. In botanical works, this or that +plant is stated to be ill adapted for wide dissemination; but for +transport across the sea, the greater or less facilities may be said to +be almost wholly unknown. Until I tried, with Mr. Berkeley’s aid, a few +experiments, it was not even known how far seeds could resist the +injurious action of sea-water. To my surprise I found that out of 87 +kinds, 64 germinated after an immersion of 28 days, and a few survived +an immersion of 137 days. For convenience sake I chiefly tried small +seeds, without the capsule or fruit; and as all of these sank in a few +days, they could not be floated across wide spaces of the sea, whether +or not they were injured by the salt-water. Afterwards I tried some +larger fruits, capsules, etc., and some of these floated for a long +time. It is well known what a difference there is in the buoyancy of +green and seasoned timber; and it occurred to me that floods might wash +down plants or branches, and that these might be dried on the banks, and +then by a fresh rise in the stream be washed into the sea. Hence I was +led to dry stems and branches of 94 plants with ripe fruit, and to place +them on sea water. The majority sank quickly, but some which whilst +green floated for a very short time, when dried floated much longer; for +instance, ripe hazel-nuts sank immediately, but when dried, they floated +for 90 days and afterwards when planted they germinated; an asparagus +plant with ripe berries floated for 23 days, when dried it floated for +85 days, and the seeds afterwards germinated: the ripe seeds of +Helosciadium sank in two days, when dried they floated for above 90 +days, and afterwards germinated. Altogether out of the 94 dried plants, +18 floated for above 28 days, and some of the 18 floated for a very much +longer period. So that as 64/87 seeds germinated after an immersion of +28 days; and as 18/94 plants with ripe fruit (but not all the same +species as in the foregoing experiment) floated, after being dried, for +above 28 days, as far as we may infer anything from these scanty facts, +we may conclude that the seeds of 14/100 plants of any country might be +floated by sea-currents during 28 days, and would retain their power of +germination. In Johnston’s Physical Atlas, the average rate of the +several Atlantic currents is 33 miles per diem (some currents running at +the rate of 60 miles per diem); on this average, the seeds of 14/100 +plants belonging to one country might be floated across 924 miles of sea +to another country; and when stranded, if blown to a favourable spot by +an inland gale, they would germinate. + +Subsequently to my experiments, M. Martens tried similar ones, but in a +much better manner, for he placed the seeds in a box in the actual sea, +so that they were alternately wet and exposed to the air like really +floating plants. He tried 98 seeds, mostly different from mine; but he +chose many large fruits and likewise seeds from plants which live near +the sea; and this would have favoured the average length of their +flotation and of their resistance to the injurious action of the +salt-water. On the other hand he did not previously dry the plants or +branches with the fruit; and this, as we have seen, would have caused +some of them to have floated much longer. The result was that 18/98 of +his seeds floated for 42 days, and were then capable of germination. But +I do not doubt that plants exposed to the waves would float for a less +time than those protected from violent movement as in our experiments. +Therefore it would perhaps be safer to assume that the seeds of about +10/100 plants of a flora, after having been dried, could be floated +across a space of sea 900 miles in width, and would then germinate. The +fact of the larger fruits often floating longer than the small, is +interesting; as plants with large seeds or fruit could hardly be +transported by any other means; and Alph. de Candolle has shown that +such plants generally have restricted ranges. + +But seeds may be occasionally transported in another manner. Drift +timber is thrown up on most islands, even on those in the midst of the +widest oceans; and the natives of the coral-islands in the Pacific, +procure stones for their tools, solely from the roots of drifted trees, +these stones being a valuable royal tax. I find on examination, that +when irregularly shaped stones are embedded in the roots of trees, small +parcels of earth are very frequently enclosed in their interstices and +behind them,—so perfectly that not a particle could be washed away in +the longest transport: out of one small portion of earth thus completely +enclosed by wood in an oak about 50 years old, three dicotyledonous +plants germinated: I am certain of the accuracy of this observation. +Again, I can show that the carcasses of birds, when floating on the sea, +sometimes escape being immediately devoured; and seeds of many kinds in +the crops of floating birds long retain their vitality: peas and +vetches, for instance, are killed by even a few days’ immersion in +sea-water; but some taken out of the crop of a pigeon, which had floated +on artificial salt-water for 30 days, to my surprise nearly all +germinated. Living birds can hardly fail to be highly effective agents in the -transportation of seeds. I could give many facts showing how frequently birds -of many kinds are blown by gales to vast distances across the ocean. We may I -think safely assume that under such circumstances their rate of flight would -often be 35 miles an hour; and some authors have given a far higher estimate. I -have never seen an instance of nutritious seeds passing through the intestines -of a bird; but hard seeds of fruit will pass uninjured through even the -digestive organs of a turkey. In the course of two months, I picked up in my -garden 12 kinds of seeds, out of the excrement of small birds, and these seemed -perfect, and some of them, which I tried, germinated. But the following fact is -more important: the crops of birds do not secrete gastric juice, and do not in -the least injure, as I know by trial, the germination of seeds; now after a -bird has found and devoured a large supply of food, it is positively asserted -that all the grains do not pass into the gizzard for 12 or even 18 hours. A -bird in this interval might easily be blown to the distance of 500 miles, and -hawks are known to look out for tired birds, and the contents of their torn -crops might thus readily get scattered. Mr. Brent informs me that a friend of -his had to give up flying carrier-pigeons from France to England, as the hawks -on the English coast destroyed so many on their arrival. Some hawks and owls -bolt their prey whole, and after an interval of from twelve to twenty hours, -disgorge pellets, which, as I know from experiments made in the Zoological -Gardens, include seeds capable of germination. Some seeds of the oat, wheat, -millet, canary, hemp, clover, and beet germinated after having been from twelve -to twenty-one hours in the stomachs of different birds of prey; and two seeds -of beet grew after having been thus retained for two days and fourteen hours. -Freshwater fish, I find, eat seeds of many land and water plants: fish are -frequently devoured by birds, and thus the seeds might be transported from -place to place. I forced many kinds of seeds into the stomachs of dead fish, -and then gave their bodies to fishing-eagles, storks, and pelicans; these birds -after an interval of many hours, either rejected the seeds in pellets or passed -them in their excrement; and several of these seeds retained their power of -germination. Certain seeds, however, were always killed by this process. - -Although the beaks and feet of birds are generally quite clean, I can show that -earth sometimes adheres to them: in one instance I removed twenty-two grains of -dry argillaceous earth from one foot of a partridge, and in this earth there -was a pebble quite as large as the seed of a vetch. Thus seeds might -occasionally be transported to great distances; for many facts could be given -showing that soil almost everywhere is charged with seeds. Reflect for a moment -on the millions of quails which annually cross the Mediterranean; and can we -doubt that the earth adhering to their feet would sometimes include a few -minute seeds? But I shall presently have to recur to this subject. - -As icebergs are known to be sometimes loaded with earth and stones, and have -even carried brushwood, bones, and the nest of a land-bird, I can hardly doubt -that they must occasionally have transported seeds from one part to another of -the arctic and antarctic regions, as suggested by Lyell; and during the Glacial -period from one part of the now temperate regions to another. In the Azores, -from the large number of the species of plants common to Europe, in comparison -with the plants of other oceanic islands nearer to the mainland, and (as -remarked by Mr. H. C. Watson) from the somewhat northern character of the flora -in comparison with the latitude, I suspected that these islands had been partly -stocked by ice-borne seeds, during the Glacial epoch. At my request Sir C. -Lyell wrote to M. Hartung to inquire whether he had observed erratic boulders -on these islands, and he answered that he had found large fragments of granite -and other rocks, which do not occur in the archipelago. Hence we may safely -infer that icebergs formerly landed their rocky burthens on the shores of these -mid-ocean islands, and it is at least possible that they may have brought -thither the seeds of northern plants. - -Considering that the several above means of transport, and that several other -means, which without doubt remain to be discovered, have been in action year -after year, for centuries and tens of thousands of years, it would I think be a -marvellous fact if many plants had not thus become widely transported. These -means of transport are sometimes called accidental, but this is not strictly -correct: the currents of the sea are not accidental, nor is the direction of -prevalent gales of wind. It should be observed that scarcely any means of -transport would carry seeds for very great distances; for seeds do not retain -their vitality when exposed for a great length of time to the action of -seawater; nor could they be long carried in the crops or intestines of birds. -These means, however, would suffice for occasional transport across tracts of +transportation of seeds. I could give many facts showing how frequently +birds of many kinds are blown by gales to vast distances across the +ocean. We may I think safely assume that under such circumstances their +rate of flight would often be 35 miles an hour; and some authors have +given a far higher estimate. I have never seen an instance of nutritious +seeds passing through the intestines of a bird; but hard seeds of fruit +will pass uninjured through even the digestive organs of a turkey. In +the course of two months, I picked up in my garden 12 kinds of seeds, +out of the excrement of small birds, and these seemed perfect, and some +of them, which I tried, germinated. But the following fact is more +important: the crops of birds do not secrete gastric juice, and do not +in the least injure, as I know by trial, the germination of seeds; now +after a bird has found and devoured a large supply of food, it is +positively asserted that all the grains do not pass into the gizzard for +12 or even 18 hours. A bird in this interval might easily be blown to +the distance of 500 miles, and hawks are known to look out for tired +birds, and the contents of their torn crops might thus readily get +scattered. Mr. Brent informs me that a friend of his had to give up +flying carrier-pigeons from France to England, as the hawks on the +English coast destroyed so many on their arrival. Some hawks and owls +bolt their prey whole, and after an interval of from twelve to twenty +hours, disgorge pellets, which, as I know from experiments made in the +Zoological Gardens, include seeds capable of germination. Some seeds of +the oat, wheat, millet, canary, hemp, clover, and beet germinated after +having been from twelve to twenty-one hours in the stomachs of different +birds of prey; and two seeds of beet grew after having been thus +retained for two days and fourteen hours. Freshwater fish, I find, eat +seeds of many land and water plants: fish are frequently devoured by +birds, and thus the seeds might be transported from place to place. I +forced many kinds of seeds into the stomachs of dead fish, and then gave +their bodies to fishing-eagles, storks, and pelicans; these birds after +an interval of many hours, either rejected the seeds in pellets or +passed them in their excrement; and several of these seeds retained +their power of germination. Certain seeds, however, were always killed +by this process. + +Although the beaks and feet of birds are generally quite clean, I can +show that earth sometimes adheres to them: in one instance I removed +twenty-two grains of dry argillaceous earth from one foot of a +partridge, and in this earth there was a pebble quite as large as the +seed of a vetch. Thus seeds might occasionally be transported to great +distances; for many facts could be given showing that soil almost +everywhere is charged with seeds. Reflect for a moment on the millions +of quails which annually cross the Mediterranean; and can we doubt that +the earth adhering to their feet would sometimes include a few minute +seeds? But I shall presently have to recur to this subject. + +As icebergs are known to be sometimes loaded with earth and stones, and +have even carried brushwood, bones, and the nest of a land-bird, I can +hardly doubt that they must occasionally have transported seeds from one +part to another of the arctic and antarctic regions, as suggested by +Lyell; and during the Glacial period from one part of the now temperate +regions to another. In the Azores, from the large number of the species +of plants common to Europe, in comparison with the plants of other +oceanic islands nearer to the mainland, and (as remarked by Mr. H. C. +Watson) from the somewhat northern character of the flora in comparison +with the latitude, I suspected that these islands had been partly +stocked by ice-borne seeds, during the Glacial epoch. At my request Sir +C. Lyell wrote to M. Hartung to inquire whether he had observed erratic +boulders on these islands, and he answered that he had found large +fragments of granite and other rocks, which do not occur in the +archipelago. Hence we may safely infer that icebergs formerly landed +their rocky burthens on the shores of these mid-ocean islands, and it is +at least possible that they may have brought thither the seeds of +northern plants. + +Considering that the several above means of transport, and that several +other means, which without doubt remain to be discovered, have been in +action year after year, for centuries and tens of thousands of years, it +would I think be a marvellous fact if many plants had not thus become +widely transported. These means of transport are sometimes called +accidental, but this is not strictly correct: the currents of the sea +are not accidental, nor is the direction of prevalent gales of wind. It +should be observed that scarcely any means of transport would carry +seeds for very great distances; for seeds do not retain their vitality +when exposed for a great length of time to the action of seawater; nor +could they be long carried in the crops or intestines of birds. These +means, however, would suffice for occasional transport across tracts of sea some hundred miles in breadth, or from island to island, or from a -continent to a neighbouring island, but not from one distant continent to -another. The floras of distant continents would not by such means become -mingled in any great degree; but would remain as distinct as we now see them to -be. The currents, from their course, would never bring seeds from North America -to Britain, though they might and do bring seeds from the West Indies to our -western shores, where, if not killed by so long an immersion in salt-water, -they could not endure our climate. Almost every year, one or two land-birds are -blown across the whole Atlantic Ocean, from North America to the western shores -of Ireland and England; but seeds could be transported by these wanderers only -by one means, namely, in dirt sticking to their feet, which is in itself a rare -accident. Even in this case, how small would the chance be of a seed falling on -favourable soil, and coming to maturity! But it would be a great error to argue -that because a well-stocked island, like Great Britain, has not, as far as is -known (and it would be very difficult to prove this), received within the last -few centuries, through occasional means of transport, immigrants from Europe or -any other continent, that a poorly-stocked island, though standing more remote -from the mainland, would not receive colonists by similar means. I do not doubt -that out of twenty seeds or animals transported to an island, even if far less -well-stocked than Britain, scarcely more than one would be so well fitted to -its new home, as to become naturalised. But this, as it seems to me, is no -valid argument against what would be effected by occasional means of transport, -during the long lapse of geological time, whilst an island was being upheaved -and formed, and before it had become fully stocked with inhabitants. On almost -bare land, with few or no destructive insects or birds living there, nearly -every seed, which chanced to arrive, would be sure to germinate and survive. - -Dispersal during the Glacial period.—The identity of many plants and animals, -on mountain-summits, separated from each other by hundreds of miles of -lowlands, where the Alpine species could not possibly exist, is one of the most -striking cases known of the same species living at distant points, without the -apparent possibility of their having migrated from one to the other. It is -indeed a remarkable fact to see so many of the same plants living on the snowy -regions of the Alps or Pyrenees, and in the extreme northern parts of Europe; -but it is far more remarkable, that the plants on the White Mountains, in the -United States of America, are all the same with those of Labrador, and nearly -all the same, as we hear from Asa Gray, with those on the loftiest mountains of -Europe. Even as long ago as 1747, such facts led Gmelin to conclude that the -same species must have been independently created at several distinct points; -and we might have remained in this same belief, had not Agassiz and others -called vivid attention to the Glacial period, which, as we shall immediately -see, affords a simple explanation of these facts. We have evidence of almost -every conceivable kind, organic and inorganic, that within a very recent -geological period, central Europe and North America suffered under an Arctic -climate. The ruins of a house burnt by fire do not tell their tale more -plainly, than do the mountains of Scotland and Wales, with their scored flanks, -polished surfaces, and perched boulders, of the icy streams with which their -valleys were lately filled. So greatly has the climate of Europe changed, that -in Northern Italy, gigantic moraines, left by old glaciers, are now clothed by -the vine and maize. Throughout a large part of the United States, erratic -boulders, and rocks scored by drifted icebergs and coast-ice, plainly reveal a -former cold period. +continent to a neighbouring island, but not from one distant continent +to another. The floras of distant continents would not by such means +become mingled in any great degree; but would remain as distinct as we +now see them to be. The currents, from their course, would never bring +seeds from North America to Britain, though they might and do bring +seeds from the West Indies to our western shores, where, if not killed +by so long an immersion in salt-water, they could not endure our +climate. Almost every year, one or two land-birds are blown across the +whole Atlantic Ocean, from North America to the western shores of +Ireland and England; but seeds could be transported by these wanderers +only by one means, namely, in dirt sticking to their feet, which is in +itself a rare accident. Even in this case, how small would the chance be +of a seed falling on favourable soil, and coming to maturity! But it +would be a great error to argue that because a well-stocked island, like +Great Britain, has not, as far as is known (and it would be very +difficult to prove this), received within the last few centuries, +through occasional means of transport, immigrants from Europe or any +other continent, that a poorly-stocked island, though standing more +remote from the mainland, would not receive colonists by similar means. +I do not doubt that out of twenty seeds or animals transported to an +island, even if far less well-stocked than Britain, scarcely more than +one would be so well fitted to its new home, as to become naturalised. +But this, as it seems to me, is no valid argument against what would be +effected by occasional means of transport, during the long lapse of +geological time, whilst an island was being upheaved and formed, and +before it had become fully stocked with inhabitants. On almost bare +land, with few or no destructive insects or birds living there, nearly +every seed, which chanced to arrive, would be sure to germinate and +survive. + +Dispersal during the Glacial period.—The identity of many plants and +animals, on mountain-summits, separated from each other by hundreds of +miles of lowlands, where the Alpine species could not possibly exist, is +one of the most striking cases known of the same species living at +distant points, without the apparent possibility of their having +migrated from one to the other. It is indeed a remarkable fact to see so +many of the same plants living on the snowy regions of the Alps or +Pyrenees, and in the extreme northern parts of Europe; but it is far +more remarkable, that the plants on the White Mountains, in the United +States of America, are all the same with those of Labrador, and nearly +all the same, as we hear from Asa Gray, with those on the loftiest +mountains of Europe. Even as long ago as 1747, such facts led Gmelin to +conclude that the same species must have been independently created at +several distinct points; and we might have remained in this same belief, +had not Agassiz and others called vivid attention to the Glacial period, +which, as we shall immediately see, affords a simple explanation of +these facts. We have evidence of almost every conceivable kind, organic +and inorganic, that within a very recent geological period, central +Europe and North America suffered under an Arctic climate. The ruins of +a house burnt by fire do not tell their tale more plainly, than do the +mountains of Scotland and Wales, with their scored flanks, polished +surfaces, and perched boulders, of the icy streams with which their +valleys were lately filled. So greatly has the climate of Europe +changed, that in Northern Italy, gigantic moraines, left by old +glaciers, are now clothed by the vine and maize. Throughout a large part +of the United States, erratic boulders, and rocks scored by drifted +icebergs and coast-ice, plainly reveal a former cold period. The former influence of the glacial climate on the distribution of the -inhabitants of Europe, as explained with remarkable clearness by Edward Forbes, -is substantially as follows. But we shall follow the changes more readily, by -supposing a new glacial period to come slowly on, and then pass away, as -formerly occurred. As the cold came on, and as each more southern zone became -fitted for arctic beings and ill-fitted for their former more temperate -inhabitants, the latter would be supplanted and arctic productions would take -their places. The inhabitants of the more temperate regions would at the same -time travel southward, unless they were stopped by barriers, in which case they -would perish. The mountains would become covered with snow and ice, and their -former Alpine inhabitants would descend to the plains. By the time that the -cold had reached its maximum, we should have a uniform arctic fauna and flora, -covering the central parts of Europe, as far south as the Alps and Pyrenees, -and even stretching into Spain. The now temperate regions of the United States -would likewise be covered by arctic plants and animals, and these would be -nearly the same with those of Europe; for the present circumpolar inhabitants, -which we suppose to have everywhere travelled southward, are remarkably uniform -round the world. We may suppose that the Glacial period came on a little -earlier or later in North America than in Europe, so will the southern -migration there have been a little earlier or later; but this will make no -difference in the final result. - -As the warmth returned, the arctic forms would retreat northward, closely -followed up in their retreat by the productions of the more temperate regions. -And as the snow melted from the bases of the mountains, the arctic forms would -seize on the cleared and thawed ground, always ascending higher and higher, as -the warmth increased, whilst their brethren were pursuing their northern -journey. Hence, when the warmth had fully returned, the same arctic species, -which had lately lived in a body together on the lowlands of the Old and New -Worlds, would be left isolated on distant mountain-summits (having been +inhabitants of Europe, as explained with remarkable clearness by Edward +Forbes, is substantially as follows. But we shall follow the changes +more readily, by supposing a new glacial period to come slowly on, and +then pass away, as formerly occurred. As the cold came on, and as each +more southern zone became fitted for arctic beings and ill-fitted for +their former more temperate inhabitants, the latter would be supplanted +and arctic productions would take their places. The inhabitants of the +more temperate regions would at the same time travel southward, unless +they were stopped by barriers, in which case they would perish. The +mountains would become covered with snow and ice, and their former +Alpine inhabitants would descend to the plains. By the time that the +cold had reached its maximum, we should have a uniform arctic fauna and +flora, covering the central parts of Europe, as far south as the Alps +and Pyrenees, and even stretching into Spain. The now temperate regions +of the United States would likewise be covered by arctic plants and +animals, and these would be nearly the same with those of Europe; for +the present circumpolar inhabitants, which we suppose to have everywhere +travelled southward, are remarkably uniform round the world. We may +suppose that the Glacial period came on a little earlier or later in +North America than in Europe, so will the southern migration there have +been a little earlier or later; but this will make no difference in the +final result. + +As the warmth returned, the arctic forms would retreat northward, +closely followed up in their retreat by the productions of the more +temperate regions. And as the snow melted from the bases of the +mountains, the arctic forms would seize on the cleared and thawed +ground, always ascending higher and higher, as the warmth increased, +whilst their brethren were pursuing their northern journey. Hence, when +the warmth had fully returned, the same arctic species, which had lately +lived in a body together on the lowlands of the Old and New Worlds, +would be left isolated on distant mountain-summits (having been exterminated on all lesser heights) and in the arctic regions of both hemispheres. -Thus we can understand the identity of many plants at points so immensely -remote as on the mountains of the United States and of Europe. We can thus also -understand the fact that the Alpine plants of each mountain-range are more -especially related to the arctic forms living due north or nearly due north of -them: for the migration as the cold came on, and the re-migration on the -returning warmth, will generally have been due south and north. The Alpine -plants, for example, of Scotland, as remarked by Mr. H. C. Watson, and those of -the Pyrenees, as remarked by Ramond, are more especially allied to the plants -of northern Scandinavia; those of the United States to Labrador; those of the +Thus we can understand the identity of many plants at points so +immensely remote as on the mountains of the United States and of Europe. +We can thus also understand the fact that the Alpine plants of each +mountain-range are more especially related to the arctic forms living +due north or nearly due north of them: for the migration as the cold +came on, and the re-migration on the returning warmth, will generally +have been due south and north. The Alpine plants, for example, of +Scotland, as remarked by Mr. H. C. Watson, and those of the Pyrenees, as +remarked by Ramond, are more especially allied to the plants of northern +Scandinavia; those of the United States to Labrador; those of the mountains of Siberia to the arctic regions of that country. These views, -grounded as they are on the perfectly well-ascertained occurrence of a former -Glacial period, seem to me to explain in so satisfactory a manner the present -distribution of the Alpine and Arctic productions of Europe and America, that -when in other regions we find the same species on distant mountain-summits, we -may almost conclude without other evidence, that a colder climate permitted -their former migration across the low intervening tracts, since become too warm -for their existence. - -If the climate, since the Glacial period, has ever been in any degree warmer -than at present (as some geologists in the United States believe to have been -the case, chiefly from the distribution of the fossil Gnathodon), then the -arctic and temperate productions will at a very late period have marched a -little further north, and subsequently have retreated to their present homes; -but I have met with no satisfactory evidence with respect to this intercalated -slightly warmer period, since the Glacial period. +grounded as they are on the perfectly well-ascertained occurrence of a +former Glacial period, seem to me to explain in so satisfactory a manner +the present distribution of the Alpine and Arctic productions of Europe +and America, that when in other regions we find the same species on +distant mountain-summits, we may almost conclude without other evidence, +that a colder climate permitted their former migration across the low +intervening tracts, since become too warm for their existence. + +If the climate, since the Glacial period, has ever been in any degree +warmer than at present (as some geologists in the United States believe +to have been the case, chiefly from the distribution of the fossil +Gnathodon), then the arctic and temperate productions will at a very +late period have marched a little further north, and subsequently have +retreated to their present homes; but I have met with no satisfactory +evidence with respect to this intercalated slightly warmer period, since +the Glacial period. The arctic forms, during their long southern migration and re-migration northward, will have been exposed to nearly the same climate, and, as is -especially to be noticed, they will have kept in a body together; consequently -their mutual relations will not have been much disturbed, and, in accordance -with the principles inculcated in this volume, they will not have been liable -to much modification. But with our Alpine productions, left isolated from the -moment of the returning warmth, first at the bases and ultimately on the -summits of the mountains, the case will have been somewhat different; for it is -not likely that all the same arctic species will have been left on mountain -ranges distant from each other, and have survived there ever since; they will, -also, in all probability have become mingled with ancient Alpine species, which -must have existed on the mountains before the commencement of the Glacial -epoch, and which during its coldest period will have been temporarily driven -down to the plains; they will, also, have been exposed to somewhat different -climatal influences. Their mutual relations will thus have been in some degree -disturbed; consequently they will have been liable to modification; and this we -find has been the case; for if we compare the present Alpine plants and animals -of the several great European mountain-ranges, though very many of the species -are identically the same, some present varieties, some are ranked as doubtful -forms, and some few are distinct yet closely allied or representative species. - -In illustrating what, as I believe, actually took place during the Glacial -period, I assumed that at its commencement the arctic productions were as -uniform round the polar regions as they are at the present day. But the -foregoing remarks on distribution apply not only to strictly arctic forms, but -also to many sub-arctic and to some few northern temperate forms, for some of -these are the same on the lower mountains and on the plains of North America -and Europe; and it may be reasonably asked how I account for the necessary -degree of uniformity of the sub-arctic and northern temperate forms round the -world, at the commencement of the Glacial period. At the present day, the -sub-arctic and northern temperate productions of the Old and New Worlds are -separated from each other by the Atlantic Ocean and by the extreme northern -part of the Pacific. During the Glacial period, when the inhabitants of the Old -and New Worlds lived further southwards than at present, they must have been -still more completely separated by wider spaces of ocean. I believe the above -difficulty may be surmounted by looking to still earlier changes of climate of -an opposite nature. We have good reason to believe that during the newer -Pliocene period, before the Glacial epoch, and whilst the majority of the -inhabitants of the world were specifically the same as now, the climate was -warmer than at the present day. Hence we may suppose that the organisms now -living under the climate of latitude 60°, during the Pliocene period lived +especially to be noticed, they will have kept in a body together; +consequently their mutual relations will not have been much disturbed, +and, in accordance with the principles inculcated in this volume, they +will not have been liable to much modification. But with our Alpine +productions, left isolated from the moment of the returning warmth, +first at the bases and ultimately on the summits of the mountains, the +case will have been somewhat different; for it is not likely that all +the same arctic species will have been left on mountain ranges distant +from each other, and have survived there ever since; they will, also, in +all probability have become mingled with ancient Alpine species, which +must have existed on the mountains before the commencement of the +Glacial epoch, and which during its coldest period will have been +temporarily driven down to the plains; they will, also, have been +exposed to somewhat different climatal influences. Their mutual +relations will thus have been in some degree disturbed; consequently +they will have been liable to modification; and this we find has been +the case; for if we compare the present Alpine plants and animals of the +several great European mountain-ranges, though very many of the species +are identically the same, some present varieties, some are ranked as +doubtful forms, and some few are distinct yet closely allied or +representative species. + +In illustrating what, as I believe, actually took place during the +Glacial period, I assumed that at its commencement the arctic +productions were as uniform round the polar regions as they are at the +present day. But the foregoing remarks on distribution apply not only to +strictly arctic forms, but also to many sub-arctic and to some few +northern temperate forms, for some of these are the same on the lower +mountains and on the plains of North America and Europe; and it may be +reasonably asked how I account for the necessary degree of uniformity of +the sub-arctic and northern temperate forms round the world, at the +commencement of the Glacial period. At the present day, the sub-arctic +and northern temperate productions of the Old and New Worlds are +separated from each other by the Atlantic Ocean and by the extreme +northern part of the Pacific. During the Glacial period, when the +inhabitants of the Old and New Worlds lived further southwards than at +present, they must have been still more completely separated by wider +spaces of ocean. I believe the above difficulty may be surmounted by +looking to still earlier changes of climate of an opposite nature. We +have good reason to believe that during the newer Pliocene period, +before the Glacial epoch, and whilst the majority of the inhabitants of +the world were specifically the same as now, the climate was warmer than +at the present day. Hence we may suppose that the organisms now living +under the climate of latitude 60°, during the Pliocene period lived further north under the Polar Circle, in latitude 66°-67°; and that the -strictly arctic productions then lived on the broken land still nearer to the -pole. Now if we look at a globe, we shall see that under the Polar Circle there -is almost continuous land from western Europe, through Siberia, to eastern -America. And to this continuity of the circumpolar land, and to the consequent -freedom for intermigration under a more favourable climate, I attribute the -necessary amount of uniformity in the sub-arctic and northern temperate -productions of the Old and New Worlds, at a period anterior to the Glacial -epoch. +strictly arctic productions then lived on the broken land still nearer +to the pole. Now if we look at a globe, we shall see that under the +Polar Circle there is almost continuous land from western Europe, +through Siberia, to eastern America. And to this continuity of the +circumpolar land, and to the consequent freedom for intermigration under +a more favourable climate, I attribute the necessary amount of +uniformity in the sub-arctic and northern temperate productions of the +Old and New Worlds, at a period anterior to the Glacial epoch. Believing, from reasons before alluded to, that our continents have long -remained in nearly the same relative position, though subjected to large, but -partial oscillations of level, I am strongly inclined to extend the above view, -and to infer that during some earlier and still warmer period, such as the -older Pliocene period, a large number of the same plants and animals inhabited -the almost continuous circumpolar land; and that these plants and animals, both -in the Old and New Worlds, began slowly to migrate southwards as the climate -became less warm, long before the commencement of the Glacial period. We now -see, as I believe, their descendants, mostly in a modified condition, in the -central parts of Europe and the United States. On this view we can understand -the relationship, with very little identity, between the productions of North -America and Europe,—a relationship which is most remarkable, considering the -distance of the two areas, and their separation by the Atlantic Ocean. We can -further understand the singular fact remarked on by several observers, that the -productions of Europe and America during the later tertiary stages were more -closely related to each other than they are at the present time; for during -these warmer periods the northern parts of the Old and New Worlds will have -been almost continuously united by land, serving as a bridge, since rendered +remained in nearly the same relative position, though subjected to +large, but partial oscillations of level, I am strongly inclined to +extend the above view, and to infer that during some earlier and still +warmer period, such as the older Pliocene period, a large number of the +same plants and animals inhabited the almost continuous circumpolar +land; and that these plants and animals, both in the Old and New Worlds, +began slowly to migrate southwards as the climate became less warm, long +before the commencement of the Glacial period. We now see, as I believe, +their descendants, mostly in a modified condition, in the central parts +of Europe and the United States. On this view we can understand the +relationship, with very little identity, between the productions of +North America and Europe,—a relationship which is most remarkable, +considering the distance of the two areas, and their separation by the +Atlantic Ocean. We can further understand the singular fact remarked on +by several observers, that the productions of Europe and America during +the later tertiary stages were more closely related to each other than +they are at the present time; for during these warmer periods the +northern parts of the Old and New Worlds will have been almost +continuously united by land, serving as a bridge, since rendered impassable by cold, for the inter-migration of their inhabitants. -During the slowly decreasing warmth of the Pliocene period, as soon as the -species in common, which inhabited the New and Old Worlds, migrated south of -the Polar Circle, they must have been completely cut off from each other. This -separation, as far as the more temperate productions are concerned, took place -long ages ago. And as the plants and animals migrated southward, they will have -become mingled in the one great region with the native American productions, -and have had to compete with them; and in the other great region, with those of -the Old World. Consequently we have here everything favourable for much -modification,—for far more modification than with the Alpine productions, left -isolated, within a much more recent period, on the several mountain-ranges and -on the arctic lands of the two Worlds. Hence it has come, that when we compare -the now living productions of the temperate regions of the New and Old Worlds, -we find very few identical species (though Asa Gray has lately shown that more -plants are identical than was formerly supposed), but we find in every great -class many forms, which some naturalists rank as geographical races, and others -as distinct species; and a host of closely allied or representative forms which -are ranked by all naturalists as specifically distinct. - -As on the land, so in the waters of the sea, a slow southern migration of a -marine fauna, which during the Pliocene or even a somewhat earlier period, was -nearly uniform along the continuous shores of the Polar Circle, will account, -on the theory of modification, for many closely allied forms now living in -areas completely sundered. Thus, I think, we can understand the presence of -many existing and tertiary representative forms on the eastern and western -shores of temperate North America; and the still more striking case of many -closely allied crustaceans (as described in Dana’s admirable work), of some -fish and other marine animals, in the Mediterranean and in the seas of -Japan,—areas now separated by a continent and by nearly a hemisphere of -equatorial ocean. - -These cases of relationship, without identity, of the inhabitants of seas now -disjoined, and likewise of the past and present inhabitants of the temperate -lands of North America and Europe, are inexplicable on the theory of creation. -We cannot say that they have been created alike, in correspondence with the -nearly similar physical conditions of the areas; for if we compare, for -instance, certain parts of South America with the southern continents of the -Old World, we see countries closely corresponding in all their physical -conditions, but with their inhabitants utterly dissimilar. - -But we must return to our more immediate subject, the Glacial period. I am -convinced that Forbes’s view may be largely extended. In Europe we have the -plainest evidence of the cold period, from the western shores of Britain to the -Oural range, and southward to the Pyrenees. We may infer, from the frozen -mammals and nature of the mountain vegetation, that Siberia was similarly -affected. Along the Himalaya, at points 900 miles apart, glaciers have left the -marks of their former low descent; and in Sikkim, Dr. Hooker saw maize growing -on gigantic ancient moraines. South of the equator, we have some direct -evidence of former glacial action in New Zealand; and the same plants, found on -widely separated mountains in this island, tell the same story. If one account -which has been published can be trusted, we have direct evidence of glacial -action in the south-eastern corner of Australia. - -Looking to America; in the northern half, ice-borne fragments of rock have been -observed on the eastern side as far south as lat. 36°-37°, and on the shores of -the Pacific, where the climate is now so different, as far south as lat. 46 -deg; erratic boulders have, also, been noticed on the Rocky Mountains. In the -Cordillera of Equatorial South America, glaciers once extended far below their -present level. In central Chile I was astonished at the structure of a vast -mound of detritus, about 800 feet in height, crossing a valley of the Andes; -and this I now feel convinced was a gigantic moraine, left far below any -existing glacier. Further south on both sides of the continent, from lat. 41° -to the southernmost extremity, we have the clearest evidence of former glacial +During the slowly decreasing warmth of the Pliocene period, as soon as +the species in common, which inhabited the New and Old Worlds, migrated +south of the Polar Circle, they must have been completely cut off from +each other. This separation, as far as the more temperate productions +are concerned, took place long ages ago. And as the plants and animals +migrated southward, they will have become mingled in the one great +region with the native American productions, and have had to compete +with them; and in the other great region, with those of the Old World. +Consequently we have here everything favourable for much +modification,—for far more modification than with the Alpine +productions, left isolated, within a much more recent period, on the +several mountain-ranges and on the arctic lands of the two Worlds. Hence +it has come, that when we compare the now living productions of the +temperate regions of the New and Old Worlds, we find very few identical +species (though Asa Gray has lately shown that more plants are identical +than was formerly supposed), but we find in every great class many +forms, which some naturalists rank as geographical races, and others as +distinct species; and a host of closely allied or representative forms +which are ranked by all naturalists as specifically distinct. + +As on the land, so in the waters of the sea, a slow southern migration +of a marine fauna, which during the Pliocene or even a somewhat earlier +period, was nearly uniform along the continuous shores of the Polar +Circle, will account, on the theory of modification, for many closely +allied forms now living in areas completely sundered. Thus, I think, we +can understand the presence of many existing and tertiary representative +forms on the eastern and western shores of temperate North America; and +the still more striking case of many closely allied crustaceans (as +described in Dana’s admirable work), of some fish and other marine +animals, in the Mediterranean and in the seas of Japan,—areas now +separated by a continent and by nearly a hemisphere of equatorial ocean. + +These cases of relationship, without identity, of the inhabitants of +seas now disjoined, and likewise of the past and present inhabitants of +the temperate lands of North America and Europe, are inexplicable on the +theory of creation. We cannot say that they have been created alike, in +correspondence with the nearly similar physical conditions of the areas; +for if we compare, for instance, certain parts of South America with the +southern continents of the Old World, we see countries closely +corresponding in all their physical conditions, but with their +inhabitants utterly dissimilar. + +But we must return to our more immediate subject, the Glacial period. I +am convinced that Forbes’s view may be largely extended. In Europe we +have the plainest evidence of the cold period, from the western shores +of Britain to the Oural range, and southward to the Pyrenees. We may +infer, from the frozen mammals and nature of the mountain vegetation, +that Siberia was similarly affected. Along the Himalaya, at points 900 +miles apart, glaciers have left the marks of their former low descent; +and in Sikkim, Dr. Hooker saw maize growing on gigantic ancient +moraines. South of the equator, we have some direct evidence of former +glacial action in New Zealand; and the same plants, found on widely +separated mountains in this island, tell the same story. If one account +which has been published can be trusted, we have direct evidence of +glacial action in the south-eastern corner of Australia. + +Looking to America; in the northern half, ice-borne fragments of rock +have been observed on the eastern side as far south as lat. 36°-37°, and +on the shores of the Pacific, where the climate is now so different, as +far south as lat. 46 deg; erratic boulders have, also, been noticed on +the Rocky Mountains. In the Cordillera of Equatorial South America, +glaciers once extended far below their present level. In central Chile I +was astonished at the structure of a vast mound of detritus, about 800 +feet in height, crossing a valley of the Andes; and this I now feel +convinced was a gigantic moraine, left far below any existing glacier. +Further south on both sides of the continent, from lat. 41° to the +southernmost extremity, we have the clearest evidence of former glacial action, in huge boulders transported far from their parent source. We do not know that the Glacial epoch was strictly simultaneous at these -several far distant points on opposite sides of the world. But we have good -evidence in almost every case, that the epoch was included within the latest -geological period. We have, also, excellent evidence, that it endured for an -enormous time, as measured by years, at each point. The cold may have come on, -or have ceased, earlier at one point of the globe than at another, but seeing -that it endured for long at each, and that it was contemporaneous in a -geological sense, it seems to me probable that it was, during a part at least -of the period, actually simultaneous throughout the world. Without some -distinct evidence to the contrary, we may at least admit as probable that the -glacial action was simultaneous on the eastern and western sides of North -America, in the Cordillera under the equator and under the warmer temperate -zones, and on both sides of the southern extremity of the continent. If this be -admitted, it is difficult to avoid believing that the temperature of the whole -world was at this period simultaneously cooler. But it would suffice for my -purpose, if the temperature was at the same time lower along certain broad -belts of longitude. - -On this view of the whole world, or at least of broad longitudinal belts, -having been simultaneously colder from pole to pole, much light can be thrown -on the present distribution of identical and allied species. In America, Dr. -Hooker has shown that between forty and fifty of the flowering plants of Tierra -del Fuego, forming no inconsiderable part of its scanty flora, are common to -Europe, enormously remote as these two points are; and there are many closely -allied species. On the lofty mountains of equatorial America a host of peculiar -species belonging to European genera occur. On the highest mountains of Brazil, -some few European genera were found by Gardner, which do not exist in the wide -intervening hot countries. So on the Silla of Caraccas the illustrious Humboldt -long ago found species belonging to genera characteristic of the Cordillera. On -the mountains of Abyssinia, several European forms and some few representatives -of the peculiar flora of the Cape of Good Hope occur. At the Cape of Good Hope -a very few European species, believed not to have been introduced by man, and -on the mountains, some few representative European forms are found, which have -not been discovered in the intertropical parts of Africa. On the Himalaya, and -on the isolated mountain-ranges of the peninsula of India, on the heights of -Ceylon, and on the volcanic cones of Java, many plants occur, either -identically the same or representing each other, and at the same time -representing plants of Europe, not found in the intervening hot lowlands. A -list of the genera collected on the loftier peaks of Java raises a picture of a -collection made on a hill in Europe! Still more striking is the fact that -southern Australian forms are clearly represented by plants growing on the -summits of the mountains of Borneo. Some of these Australian forms, as I hear -from Dr. Hooker, extend along the heights of the peninsula of Malacca, and are -thinly scattered, on the one hand over India and on the other as far north as +several far distant points on opposite sides of the world. But we have +good evidence in almost every case, that the epoch was included within +the latest geological period. We have, also, excellent evidence, that it +endured for an enormous time, as measured by years, at each point. The +cold may have come on, or have ceased, earlier at one point of the globe +than at another, but seeing that it endured for long at each, and that +it was contemporaneous in a geological sense, it seems to me probable +that it was, during a part at least of the period, actually simultaneous +throughout the world. Without some distinct evidence to the contrary, we +may at least admit as probable that the glacial action was simultaneous +on the eastern and western sides of North America, in the Cordillera +under the equator and under the warmer temperate zones, and on both +sides of the southern extremity of the continent. If this be admitted, +it is difficult to avoid believing that the temperature of the whole +world was at this period simultaneously cooler. But it would suffice for +my purpose, if the temperature was at the same time lower along certain +broad belts of longitude. + +On this view of the whole world, or at least of broad longitudinal +belts, having been simultaneously colder from pole to pole, much light +can be thrown on the present distribution of identical and allied +species. In America, Dr. Hooker has shown that between forty and fifty +of the flowering plants of Tierra del Fuego, forming no inconsiderable +part of its scanty flora, are common to Europe, enormously remote as +these two points are; and there are many closely allied species. On the +lofty mountains of equatorial America a host of peculiar species +belonging to European genera occur. On the highest mountains of Brazil, +some few European genera were found by Gardner, which do not exist in +the wide intervening hot countries. So on the Silla of Caraccas the +illustrious Humboldt long ago found species belonging to genera +characteristic of the Cordillera. On the mountains of Abyssinia, several +European forms and some few representatives of the peculiar flora of the +Cape of Good Hope occur. At the Cape of Good Hope a very few European +species, believed not to have been introduced by man, and on the +mountains, some few representative European forms are found, which have +not been discovered in the intertropical parts of Africa. On the +Himalaya, and on the isolated mountain-ranges of the peninsula of India, +on the heights of Ceylon, and on the volcanic cones of Java, many plants +occur, either identically the same or representing each other, and at +the same time representing plants of Europe, not found in the +intervening hot lowlands. A list of the genera collected on the loftier +peaks of Java raises a picture of a collection made on a hill in Europe! +Still more striking is the fact that southern Australian forms are +clearly represented by plants growing on the summits of the mountains of +Borneo. Some of these Australian forms, as I hear from Dr. Hooker, +extend along the heights of the peninsula of Malacca, and are thinly +scattered, on the one hand over India and on the other as far north as Japan. -On the southern mountains of Australia, Dr. F. Müller has discovered several -European species; other species, not introduced by man, occur on the lowlands; -and a long list can be given, as I am informed by Dr. Hooker, of European -genera, found in Australia, but not in the intermediate torrid regions. In the -admirable ‘Introduction to the Flora of New Zealand,’ by Dr. Hooker, analogous -and striking facts are given in regard to the plants of that large island. -Hence we see that throughout the world, the plants growing on the more lofty -mountains, and on the temperate lowlands of the northern and southern -hemispheres, are sometimes identically the same; but they are much oftener +On the southern mountains of Australia, Dr. F. Müller has discovered +several European species; other species, not introduced by man, occur on +the lowlands; and a long list can be given, as I am informed by Dr. +Hooker, of European genera, found in Australia, but not in the +intermediate torrid regions. In the admirable ‘Introduction to the Flora +of New Zealand,’ by Dr. Hooker, analogous and striking facts are given +in regard to the plants of that large island. Hence we see that +throughout the world, the plants growing on the more lofty mountains, +and on the temperate lowlands of the northern and southern hemispheres, +are sometimes identically the same; but they are much oftener specifically distinct, though related to each other in a most remarkable manner. -This brief abstract applies to plants alone: some strictly analogous facts -could be given on the distribution of terrestrial animals. In marine -productions, similar cases occur; as an example, I may quote a remark by the -highest authority, Professor Dana, that “it is certainly a wonderful fact that -New Zealand should have a closer resemblance in its crustacea to Great Britain, -its antipode, than to any other part of the world.” Sir J. Richardson, also, -speaks of the reappearance on the shores of New Zealand, Tasmania, etc., of -northern forms of fish. Dr. Hooker informs me that twenty-five species of Algæ -are common to New Zealand and to Europe, but have not been found in the -intermediate tropical seas. - -It should be observed that the northern species and forms found in the southern -parts of the southern hemisphere, and on the mountain-ranges of the -intertropical regions, are not arctic, but belong to the northern temperate -zones. As Mr. H. C. Watson has recently remarked, “In receding from polar -towards equatorial latitudes, the Alpine or mountain floras really become less -and less arctic.” Many of the forms living on the mountains of the warmer -regions of the earth and in the southern hemisphere are of doubtful value, -being ranked by some naturalists as specifically distinct, by others as -varieties; but some are certainly identical, and many, though closely related -to northern forms, must be ranked as distinct species. - -Now let us see what light can be thrown on the foregoing facts, on the belief, -supported as it is by a large body of geological evidence, that the whole -world, or a large part of it, was during the Glacial period simultaneously much -colder than at present. The Glacial period, as measured by years, must have -been very long; and when we remember over what vast spaces some naturalised -plants and animals have spread within a few centuries, this period will have -been ample for any amount of migration. As the cold came slowly on, all the -tropical plants and other productions will have retreated from both sides -towards the equator, followed in the rear by the temperate productions, and -these by the arctic; but with the latter we are not now concerned. The tropical -plants probably suffered much extinction; how much no one can say; perhaps -formerly the tropics supported as many species as we see at the present day -crowded together at the Cape of Good Hope, and in parts of temperate Australia. -As we know that many tropical plants and animals can withstand a considerable -amount of cold, many might have escaped extermination during a moderate fall of -temperature, more especially by escaping into the warmest spots. But the great -fact to bear in mind is, that all tropical productions will have suffered to a -certain extent. On the other hand, the temperate productions, after migrating -nearer to the equator, though they will have been placed under somewhat new -conditions, will have suffered less. And it is certain that many temperate -plants, if protected from the inroads of competitors, can withstand a much -warmer climate than their own. Hence, it seems to me possible, bearing in mind -that the tropical productions were in a suffering state and could not have -presented a firm front against intruders, that a certain number of the more -vigorous and dominant temperate forms might have penetrated the native ranks -and have reached or even crossed the equator. The invasion would, of course, -have been greatly favoured by high land, and perhaps by a dry climate; for Dr. -Falconer informs me that it is the damp with the heat of the tropics which is -so destructive to perennial plants from a temperate climate. On the other hand, -the most humid and hottest districts will have afforded an asylum to the -tropical natives. The mountain-ranges north-west of the Himalaya, and the long -line of the Cordillera, seem to have afforded two great lines of invasion: and -it is a striking fact, lately communicated to me by Dr. Hooker, that all the -flowering plants, about forty-six in number, common to Tierra del Fuego and to -Europe still exist in North America, which must have lain on the line of march. -But I do not doubt that some temperate productions entered and crossed even the -lowlands of the tropics at the period when the cold was most intense,—when -arctic forms had migrated some twenty-five degrees of latitude from their -native country and covered the land at the foot of the Pyrenees. At this period -of extreme cold, I believe that the climate under the equator at the level of -the sea was about the same with that now felt there at the height of six or -seven thousand feet. During this the coldest period, I suppose that large -spaces of the tropical lowlands were clothed with a mingled tropical and -temperate vegetation, like that now growing with strange luxuriance at the base -of the Himalaya, as graphically described by Hooker. - -Thus, as I believe, a considerable number of plants, a few terrestrial animals, -and some marine productions, migrated during the Glacial period from the -northern and southern temperate zones into the intertropical regions, and some -even crossed the equator. As the warmth returned, these temperate forms would -naturally ascend the higher mountains, being exterminated on the lowlands; -those which had not reached the equator, would re-migrate northward or -southward towards their former homes; but the forms, chiefly northern, which -had crossed the equator, would travel still further from their homes into the -more temperate latitudes of the opposite hemisphere. Although we have reason to -believe from geological evidence that the whole body of arctic shells underwent -scarcely any modification during their long southern migration and re-migration -northward, the case may have been wholly different with those intruding forms -which settled themselves on the intertropical mountains, and in the southern -hemisphere. These being surrounded by strangers will have had to compete with -many new forms of life; and it is probable that selected modifications in their -structure, habits, and constitutions will have profited them. Thus many of -these wanderers, though still plainly related by inheritance to their brethren -of the northern or southern hemispheres, now exist in their new homes as -well-marked varieties or as distinct species. - -It is a remarkable fact, strongly insisted on by Hooker in regard to America, -and by Alph. de Candolle in regard to Australia, that many more identical -plants and allied forms have apparently migrated from the north to the south, -than in a reversed direction. We see, however, a few southern vegetable forms -on the mountains of Borneo and Abyssinia. I suspect that this preponderant -migration from north to south is due to the greater extent of land in the -north, and to the northern forms having existed in their own homes in greater -numbers, and having consequently been advanced through natural selection and -competition to a higher stage of perfection or dominating power, than the -southern forms. And thus, when they became commingled during the Glacial -period, the northern forms were enabled to beat the less powerful southern -forms. Just in the same manner as we see at the present day, that very many -European productions cover the ground in La Plata, and in a lesser degree in -Australia, and have to a certain extent beaten the natives; whereas extremely -few southern forms have become naturalised in any part of Europe, though hides, -wool, and other objects likely to carry seeds have been largely imported into -Europe during the last two or three centuries from La Plata, and during the -last thirty or forty years from Australia. Something of the same kind must have -occurred on the intertropical mountains: no doubt before the Glacial period -they were stocked with endemic Alpine forms; but these have almost everywhere -largely yielded to the more dominant forms, generated in the larger areas and -more efficient workshops of the north. In many islands the native productions -are nearly equalled or even outnumbered by the naturalised; and if the natives -have not been actually exterminated, their numbers have been greatly reduced, -and this is the first stage towards extinction. A mountain is an island on the -land; and the intertropical mountains before the Glacial period must have been -completely isolated; and I believe that the productions of these islands on the -land yielded to those produced within the larger areas of the north, just in -the same way as the productions of real islands have everywhere lately yielded -to continental forms, naturalised by man’s agency. - -I am far from supposing that all difficulties are removed on the view here -given in regard to the range and affinities of the allied species which live in -the northern and southern temperate zones and on the mountains of the -intertropical regions. Very many difficulties remain to be solved. I do not -pretend to indicate the exact lines and means of migration, or the reason why -certain species and not others have migrated; why certain species have been -modified and have given rise to new groups of forms, and others have remained -unaltered. We cannot hope to explain such facts, until we can say why one -species and not another becomes naturalised by man’s agency in a foreign land; -why one ranges twice or thrice as far, and is twice or thrice as common, as -another species within their own homes. +This brief abstract applies to plants alone: some strictly analogous +facts could be given on the distribution of terrestrial animals. In +marine productions, similar cases occur; as an example, I may quote a +remark by the highest authority, Professor Dana, that “it is certainly a +wonderful fact that New Zealand should have a closer resemblance in its +crustacea to Great Britain, its antipode, than to any other part of the +world.” Sir J. Richardson, also, speaks of the reappearance on the +shores of New Zealand, Tasmania, etc., of northern forms of fish. Dr. +Hooker informs me that twenty-five species of Algæ are common to New +Zealand and to Europe, but have not been found in the intermediate +tropical seas. + +It should be observed that the northern species and forms found in the +southern parts of the southern hemisphere, and on the mountain-ranges of +the intertropical regions, are not arctic, but belong to the northern +temperate zones. As Mr. H. C. Watson has recently remarked, “In receding +from polar towards equatorial latitudes, the Alpine or mountain floras +really become less and less arctic.” Many of the forms living on the +mountains of the warmer regions of the earth and in the southern +hemisphere are of doubtful value, being ranked by some naturalists as +specifically distinct, by others as varieties; but some are certainly +identical, and many, though closely related to northern forms, must be +ranked as distinct species. + +Now let us see what light can be thrown on the foregoing facts, on the +belief, supported as it is by a large body of geological evidence, that +the whole world, or a large part of it, was during the Glacial period +simultaneously much colder than at present. The Glacial period, as +measured by years, must have been very long; and when we remember over +what vast spaces some naturalised plants and animals have spread within +a few centuries, this period will have been ample for any amount of +migration. As the cold came slowly on, all the tropical plants and other +productions will have retreated from both sides towards the equator, +followed in the rear by the temperate productions, and these by the +arctic; but with the latter we are not now concerned. The tropical +plants probably suffered much extinction; how much no one can say; +perhaps formerly the tropics supported as many species as we see at the +present day crowded together at the Cape of Good Hope, and in parts of +temperate Australia. As we know that many tropical plants and animals +can withstand a considerable amount of cold, many might have escaped +extermination during a moderate fall of temperature, more especially by +escaping into the warmest spots. But the great fact to bear in mind is, +that all tropical productions will have suffered to a certain extent. On +the other hand, the temperate productions, after migrating nearer to the +equator, though they will have been placed under somewhat new +conditions, will have suffered less. And it is certain that many +temperate plants, if protected from the inroads of competitors, can +withstand a much warmer climate than their own. Hence, it seems to me +possible, bearing in mind that the tropical productions were in a +suffering state and could not have presented a firm front against +intruders, that a certain number of the more vigorous and dominant +temperate forms might have penetrated the native ranks and have reached +or even crossed the equator. The invasion would, of course, have been +greatly favoured by high land, and perhaps by a dry climate; for Dr. +Falconer informs me that it is the damp with the heat of the tropics +which is so destructive to perennial plants from a temperate climate. On +the other hand, the most humid and hottest districts will have afforded +an asylum to the tropical natives. The mountain-ranges north-west of the +Himalaya, and the long line of the Cordillera, seem to have afforded two +great lines of invasion: and it is a striking fact, lately communicated +to me by Dr. Hooker, that all the flowering plants, about forty-six in +number, common to Tierra del Fuego and to Europe still exist in North +America, which must have lain on the line of march. But I do not doubt +that some temperate productions entered and crossed even the lowlands of +the tropics at the period when the cold was most intense,—when arctic +forms had migrated some twenty-five degrees of latitude from their +native country and covered the land at the foot of the Pyrenees. At this +period of extreme cold, I believe that the climate under the equator at +the level of the sea was about the same with that now felt there at the +height of six or seven thousand feet. During this the coldest period, I +suppose that large spaces of the tropical lowlands were clothed with a +mingled tropical and temperate vegetation, like that now growing with +strange luxuriance at the base of the Himalaya, as graphically described +by Hooker. + +Thus, as I believe, a considerable number of plants, a few terrestrial +animals, and some marine productions, migrated during the Glacial period +from the northern and southern temperate zones into the intertropical +regions, and some even crossed the equator. As the warmth returned, +these temperate forms would naturally ascend the higher mountains, being +exterminated on the lowlands; those which had not reached the equator, +would re-migrate northward or southward towards their former homes; but +the forms, chiefly northern, which had crossed the equator, would travel +still further from their homes into the more temperate latitudes of the +opposite hemisphere. Although we have reason to believe from geological +evidence that the whole body of arctic shells underwent scarcely any +modification during their long southern migration and re-migration +northward, the case may have been wholly different with those intruding +forms which settled themselves on the intertropical mountains, and in +the southern hemisphere. These being surrounded by strangers will have +had to compete with many new forms of life; and it is probable that +selected modifications in their structure, habits, and constitutions +will have profited them. Thus many of these wanderers, though still +plainly related by inheritance to their brethren of the northern or +southern hemispheres, now exist in their new homes as well-marked +varieties or as distinct species. + +It is a remarkable fact, strongly insisted on by Hooker in regard to +America, and by Alph. de Candolle in regard to Australia, that many more +identical plants and allied forms have apparently migrated from the +north to the south, than in a reversed direction. We see, however, a few +southern vegetable forms on the mountains of Borneo and Abyssinia. I +suspect that this preponderant migration from north to south is due to +the greater extent of land in the north, and to the northern forms +having existed in their own homes in greater numbers, and having +consequently been advanced through natural selection and competition to +a higher stage of perfection or dominating power, than the southern +forms. And thus, when they became commingled during the Glacial period, +the northern forms were enabled to beat the less powerful southern +forms. Just in the same manner as we see at the present day, that very +many European productions cover the ground in La Plata, and in a lesser +degree in Australia, and have to a certain extent beaten the natives; +whereas extremely few southern forms have become naturalised in any part +of Europe, though hides, wool, and other objects likely to carry seeds +have been largely imported into Europe during the last two or three +centuries from La Plata, and during the last thirty or forty years from +Australia. Something of the same kind must have occurred on the +intertropical mountains: no doubt before the Glacial period they were +stocked with endemic Alpine forms; but these have almost everywhere +largely yielded to the more dominant forms, generated in the larger +areas and more efficient workshops of the north. In many islands the +native productions are nearly equalled or even outnumbered by the +naturalised; and if the natives have not been actually exterminated, +their numbers have been greatly reduced, and this is the first stage +towards extinction. A mountain is an island on the land; and the +intertropical mountains before the Glacial period must have been +completely isolated; and I believe that the productions of these islands +on the land yielded to those produced within the larger areas of the +north, just in the same way as the productions of real islands have +everywhere lately yielded to continental forms, naturalised by man’s +agency. + +I am far from supposing that all difficulties are removed on the view +here given in regard to the range and affinities of the allied species +which live in the northern and southern temperate zones and on the +mountains of the intertropical regions. Very many difficulties remain to +be solved. I do not pretend to indicate the exact lines and means of +migration, or the reason why certain species and not others have +migrated; why certain species have been modified and have given rise to +new groups of forms, and others have remained unaltered. We cannot hope +to explain such facts, until we can say why one species and not another +becomes naturalised by man’s agency in a foreign land; why one ranges +twice or thrice as far, and is twice or thrice as common, as another +species within their own homes. I have said that many difficulties remain to be solved: some of the most -remarkable are stated with admirable clearness by Dr. Hooker in his botanical -works on the antarctic regions. These cannot be here discussed. I will only say -that as far as regards the occurrence of identical species at points so -enormously remote as Kerguelen Land, New Zealand, and Fuegia, I believe that -towards the close of the Glacial period, icebergs, as suggested by Lyell, have -been largely concerned in their dispersal. But the existence of several quite -distinct species, belonging to genera exclusively confined to the south, at -these and other distant points of the southern hemisphere, is, on my theory of -descent with modification, a far more remarkable case of difficulty. For some -of these species are so distinct, that we cannot suppose that there has been -time since the commencement of the Glacial period for their migration, and for -their subsequent modification to the necessary degree. The facts seem to me to -indicate that peculiar and very distinct species have migrated in radiating -lines from some common centre; and I am inclined to look in the southern, as in -the northern hemisphere, to a former and warmer period, before the commencement -of the Glacial period, when the antarctic lands, now covered with ice, -supported a highly peculiar and isolated flora. I suspect that before this -flora was exterminated by the Glacial epoch, a few forms were widely dispersed -to various points of the southern hemisphere by occasional means of transport, -and by the aid, as halting-places, of existing and now sunken islands, and -perhaps at the commencement of the Glacial period, by icebergs. By these means, -as I believe, the southern shores of America, Australia, New Zealand have -become slightly tinted by the same peculiar forms of vegetable life. - -Sir C. Lyell in a striking passage has speculated, in language almost identical -with mine, on the effects of great alternations of climate on geographical -distribution. I believe that the world has recently felt one of his great -cycles of change; and that on this view, combined with modification through -natural selection, a multitude of facts in the present distribution both of the -same and of allied forms of life can be explained. The living waters may be -said to have flowed during one short period from the north and from the south, -and to have crossed at the equator; but to have flowed with greater force from -the north so as to have freely inundated the south. As the tide leaves its -drift in horizontal lines, though rising higher on the shores where the tide +remarkable are stated with admirable clearness by Dr. Hooker in his +botanical works on the antarctic regions. These cannot be here +discussed. I will only say that as far as regards the occurrence of +identical species at points so enormously remote as Kerguelen Land, New +Zealand, and Fuegia, I believe that towards the close of the Glacial +period, icebergs, as suggested by Lyell, have been largely concerned in +their dispersal. But the existence of several quite distinct species, +belonging to genera exclusively confined to the south, at these and +other distant points of the southern hemisphere, is, on my theory of +descent with modification, a far more remarkable case of difficulty. For +some of these species are so distinct, that we cannot suppose that there +has been time since the commencement of the Glacial period for their +migration, and for their subsequent modification to the necessary +degree. The facts seem to me to indicate that peculiar and very distinct +species have migrated in radiating lines from some common centre; and I +am inclined to look in the southern, as in the northern hemisphere, to a +former and warmer period, before the commencement of the Glacial period, +when the antarctic lands, now covered with ice, supported a highly +peculiar and isolated flora. I suspect that before this flora was +exterminated by the Glacial epoch, a few forms were widely dispersed to +various points of the southern hemisphere by occasional means of +transport, and by the aid, as halting-places, of existing and now sunken +islands, and perhaps at the commencement of the Glacial period, by +icebergs. By these means, as I believe, the southern shores of America, +Australia, New Zealand have become slightly tinted by the same peculiar +forms of vegetable life. + +Sir C. Lyell in a striking passage has speculated, in language almost +identical with mine, on the effects of great alternations of climate on +geographical distribution. I believe that the world has recently felt +one of his great cycles of change; and that on this view, combined with +modification through natural selection, a multitude of facts in the +present distribution both of the same and of allied forms of life can be +explained. The living waters may be said to have flowed during one short +period from the north and from the south, and to have crossed at the +equator; but to have flowed with greater force from the north so as to +have freely inundated the south. As the tide leaves its drift in +horizontal lines, though rising higher on the shores where the tide rises highest, so have the living waters left their living drift on our -mountain-summits, in a line gently rising from the arctic lowlands to a great -height under the equator. The various beings thus left stranded may be compared -with savage races of man, driven up and surviving in the mountain-fastnesses of -almost every land, which serve as a record, full of interest to us, of the -former inhabitants of the surrounding lowlands. - -CHAPTER XII. -GEOGRAPHICAL DISTRIBUTION—continued. - -Distribution of fresh-water productions. On the inhabitants of oceanic islands. -Absence of Batrachians and of terrestrial Mammals. On the relation of the -inhabitants of islands to those of the nearest mainland. On colonisation from -the nearest source with subsequent modification. Summary of the last and -present chapters. - -As lakes and river-systems are separated from each other by barriers of land, -it might have been thought that fresh-water productions would not have ranged -widely within the same country, and as the sea is apparently a still more -impassable barrier, that they never would have extended to distant countries. -But the case is exactly the reverse. Not only have many fresh-water species, -belonging to quite different classes, an enormous range, but allied species -prevail in a remarkable manner throughout the world. I well remember, when -first collecting in the fresh waters of Brazil, feeling much surprise at the -similarity of the fresh-water insects, shells, etc., and at the dissimilarity -of the surrounding terrestrial beings, compared with those of Britain. +mountain-summits, in a line gently rising from the arctic lowlands to a +great height under the equator. The various beings thus left stranded +may be compared with savage races of man, driven up and surviving in the +mountain-fastnesses of almost every land, which serve as a record, full +of interest to us, of the former inhabitants of the surrounding +lowlands. + +CHAPTER XII. GEOGRAPHICAL DISTRIBUTION—continued. + +Distribution of fresh-water productions. On the inhabitants of oceanic +islands. Absence of Batrachians and of terrestrial Mammals. On the +relation of the inhabitants of islands to those of the nearest mainland. +On colonisation from the nearest source with subsequent modification. +Summary of the last and present chapters. + +As lakes and river-systems are separated from each other by barriers of +land, it might have been thought that fresh-water productions would not +have ranged widely within the same country, and as the sea is apparently +a still more impassable barrier, that they never would have extended to +distant countries. But the case is exactly the reverse. Not only have +many fresh-water species, belonging to quite different classes, an +enormous range, but allied species prevail in a remarkable manner +throughout the world. I well remember, when first collecting in the +fresh waters of Brazil, feeling much surprise at the similarity of the +fresh-water insects, shells, etc., and at the dissimilarity of the +surrounding terrestrial beings, compared with those of Britain. But this power in fresh-water productions of ranging widely, though so -unexpected, can, I think, in most cases be explained by their having become -fitted, in a manner highly useful to them, for short and frequent migrations -from pond to pond, or from stream to stream; and liability to wide dispersal -would follow from this capacity as an almost necessary consequence. We can here -consider only a few cases. In regard to fish, I believe that the same species -never occur in the fresh waters of distant continents. But on the same -continent the species often range widely and almost capriciously; for two -river-systems will have some fish in common and some different. A few facts -seem to favour the possibility of their occasional transport by accidental -means; like that of the live fish not rarely dropped by whirlwinds in India, -and the vitality of their ova when removed from the water. But I am inclined to -attribute the dispersal of fresh-water fish mainly to slight changes within the -recent period in the level of the land, having caused rivers to flow into each -other. Instances, also, could be given of this having occurred during floods, -without any change of level. We have evidence in the loess of the Rhine of -considerable changes of level in the land within a very recent geological -period, and when the surface was peopled by existing land and fresh-water -shells. The wide difference of the fish on opposite sides of continuous -mountain-ranges, which from an early period must have parted river-systems and -completely prevented their inosculation, seems to lead to this same conclusion. -With respect to allied fresh-water fish occurring at very distant points of the -world, no doubt there are many cases which cannot at present be explained: but -some fresh-water fish belong to very ancient forms, and in such cases there -will have been ample time for great geographical changes, and consequently time -and means for much migration. In the second place, salt-water fish can with -care be slowly accustomed to live in fresh water; and, according to -Valenciennes, there is hardly a single group of fishes confined exclusively to -fresh water, so that we may imagine that a marine member of a fresh-water group -might travel far along the shores of the sea, and subsequently become modified -and adapted to the fresh waters of a distant land. - -Some species of fresh-water shells have a very wide range, and allied species, -which, on my theory, are descended from a common parent and must have proceeded -from a single source, prevail throughout the world. Their distribution at first -perplexed me much, as their ova are not likely to be transported by birds, and -they are immediately killed by sea water, as are the adults. I could not even -understand how some naturalised species have rapidly spread throughout the same -country. But two facts, which I have observed—and no doubt many others remain -to be observed—throw some light on this subject. When a duck suddenly emerges -from a pond covered with duck-weed, I have twice seen these little plants -adhering to its back; and it has happened to me, in removing a little duck-weed -from one aquarium to another, that I have quite unintentionally stocked the one -with fresh-water shells from the other. But another agency is perhaps more -effectual: I suspended a duck’s feet, which might represent those of a bird -sleeping in a natural pond, in an aquarium, where many ova of fresh-water -shells were hatching; and I found that numbers of the extremely minute and just -hatched shells crawled on the feet, and clung to them so firmly that when taken -out of the water they could not be jarred off, though at a somewhat more -advanced age they would voluntarily drop off. These just hatched molluscs, -though aquatic in their nature, survived on the duck’s feet, in damp air, from -twelve to twenty hours; and in this length of time a duck or heron might fly at -least six or seven hundred miles, and would be sure to alight on a pool or -rivulet, if blown across sea to an oceanic island or to any other distant -point. Sir Charles Lyell also informs me that a Dyticus has been caught with an -Ancylus (a fresh-water shell like a limpet) firmly adhering to it; and a -water-beetle of the same family, a Colymbetes, once flew on board the ‘Beagle,’ -when forty-five miles distant from the nearest land: how much farther it might -have flown with a favouring gale no one can tell. +unexpected, can, I think, in most cases be explained by their having +become fitted, in a manner highly useful to them, for short and frequent +migrations from pond to pond, or from stream to stream; and liability to +wide dispersal would follow from this capacity as an almost necessary +consequence. We can here consider only a few cases. In regard to fish, I +believe that the same species never occur in the fresh waters of distant +continents. But on the same continent the species often range widely and +almost capriciously; for two river-systems will have some fish in common +and some different. A few facts seem to favour the possibility of their +occasional transport by accidental means; like that of the live fish not +rarely dropped by whirlwinds in India, and the vitality of their ova +when removed from the water. But I am inclined to attribute the +dispersal of fresh-water fish mainly to slight changes within the recent +period in the level of the land, having caused rivers to flow into each +other. Instances, also, could be given of this having occurred during +floods, without any change of level. We have evidence in the loess of +the Rhine of considerable changes of level in the land within a very +recent geological period, and when the surface was peopled by existing +land and fresh-water shells. The wide difference of the fish on opposite +sides of continuous mountain-ranges, which from an early period must +have parted river-systems and completely prevented their inosculation, +seems to lead to this same conclusion. With respect to allied +fresh-water fish occurring at very distant points of the world, no doubt +there are many cases which cannot at present be explained: but some +fresh-water fish belong to very ancient forms, and in such cases there +will have been ample time for great geographical changes, and +consequently time and means for much migration. In the second place, +salt-water fish can with care be slowly accustomed to live in fresh +water; and, according to Valenciennes, there is hardly a single group of +fishes confined exclusively to fresh water, so that we may imagine that +a marine member of a fresh-water group might travel far along the shores +of the sea, and subsequently become modified and adapted to the fresh +waters of a distant land. + +Some species of fresh-water shells have a very wide range, and allied +species, which, on my theory, are descended from a common parent and +must have proceeded from a single source, prevail throughout the world. +Their distribution at first perplexed me much, as their ova are not +likely to be transported by birds, and they are immediately killed by +sea water, as are the adults. I could not even understand how some +naturalised species have rapidly spread throughout the same country. But +two facts, which I have observed—and no doubt many others remain to be +observed—throw some light on this subject. When a duck suddenly emerges +from a pond covered with duck-weed, I have twice seen these little +plants adhering to its back; and it has happened to me, in removing a +little duck-weed from one aquarium to another, that I have quite +unintentionally stocked the one with fresh-water shells from the other. +But another agency is perhaps more effectual: I suspended a duck’s feet, +which might represent those of a bird sleeping in a natural pond, in an +aquarium, where many ova of fresh-water shells were hatching; and I +found that numbers of the extremely minute and just hatched shells +crawled on the feet, and clung to them so firmly that when taken out of +the water they could not be jarred off, though at a somewhat more +advanced age they would voluntarily drop off. These just hatched +molluscs, though aquatic in their nature, survived on the duck’s feet, +in damp air, from twelve to twenty hours; and in this length of time a +duck or heron might fly at least six or seven hundred miles, and would +be sure to alight on a pool or rivulet, if blown across sea to an +oceanic island or to any other distant point. Sir Charles Lyell also +informs me that a Dyticus has been caught with an Ancylus (a fresh-water +shell like a limpet) firmly adhering to it; and a water-beetle of the +same family, a Colymbetes, once flew on board the ‘Beagle,’ when +forty-five miles distant from the nearest land: how much farther it +might have flown with a favouring gale no one can tell. With respect to plants, it has long been known what enormous ranges many -fresh-water and even marsh-species have, both over continents and to the most -remote oceanic islands. This is strikingly shown, as remarked by Alph. de -Candolle, in large groups of terrestrial plants, which have only a very few -aquatic members; for these latter seem immediately to acquire, as if in -consequence, a very wide range. I think favourable means of dispersal explain -this fact. I have before mentioned that earth occasionally, though rarely, -adheres in some quantity to the feet and beaks of birds. Wading birds, which -frequent the muddy edges of ponds, if suddenly flushed, would be the most -likely to have muddy feet. Birds of this order I can show are the greatest -wanderers, and are occasionally found on the most remote and barren islands in -the open ocean; they would not be likely to alight on the surface of the sea, -so that the dirt would not be washed off their feet; when making land, they -would be sure to fly to their natural fresh-water haunts. I do not believe that -botanists are aware how charged the mud of ponds is with seeds: I have tried -several little experiments, but will here give only the most striking case: I -took in February three table-spoonfuls of mud from three different points, -beneath water, on the edge of a little pond; this mud when dry weighed only 6 3 -/4 ounces; I kept it covered up in my study for six months, pulling up and -counting each plant as it grew; the plants were of many kinds, and were -altogether 537 in number; and yet the viscid mud was all contained in a -breakfast cup! Considering these facts, I think it would be an inexplicable -circumstance if water-birds did not transport the seeds of fresh-water plants -to vast distances, and if consequently the range of these plants was not very -great. The same agency may have come into play with the eggs of some of the -smaller fresh-water animals. - -Other and unknown agencies probably have also played a part. I have stated that -fresh-water fish eat some kinds of seeds, though they reject many other kinds -after having swallowed them; even small fish swallow seeds of moderate size, as -of the yellow water-lily and Potamogeton. Herons and other birds, century after -century, have gone on daily devouring fish; they then take flight and go to -other waters, or are blown across the sea; and we have seen that seeds retain -their power of germination, when rejected in pellets or in excrement, many -hours afterwards. When I saw the great size of the seeds of that fine -water-lily, the Nelumbium, and remembered Alph. de Candolle’s remarks on this -plant, I thought that its distribution must remain quite inexplicable; but -Audubon states that he found the seeds of the great southern water-lily -(probably, according to Dr. Hooker, the Nelumbium luteum) in a heron’s stomach; -although I do not know the fact, yet analogy makes me believe that a heron -flying to another pond and getting a hearty meal of fish, would probably reject -from its stomach a pellet containing the seeds of the Nelumbium undigested; or -the seeds might be dropped by the bird whilst feeding its young, in the same -way as fish are known sometimes to be dropped. - -In considering these several means of distribution, it should be remembered -that when a pond or stream is first formed, for instance, on a rising islet, it -will be unoccupied; and a single seed or egg will have a good chance of -succeeding. Although there will always be a struggle for life between the -individuals of the species, however few, already occupying any pond, yet as the -number of kinds is small, compared with those on the land, the competition will -probably be less severe between aquatic than between terrestrial species; -consequently an intruder from the waters of a foreign country, would have a -better chance of seizing on a place, than in the case of terrestrial colonists. -We should, also, remember that some, perhaps many, fresh-water productions are -low in the scale of nature, and that we have reason to believe that such low -beings change or become modified less quickly than the high; and this will give -longer time than the average for the migration of the same aquatic species. We -should not forget the probability of many species having formerly ranged as -continuously as fresh-water productions ever can range, over immense areas, and -having subsequently become extinct in intermediate regions. But the wide -distribution of fresh-water plants and of the lower animals, whether retaining -the same identical form or in some degree modified, I believe mainly depends on -the wide dispersal of their seeds and eggs by animals, more especially by -fresh-water birds, which have large powers of flight, and naturally travel from -one to another and often distant piece of water. Nature, like a careful -gardener, thus takes her seeds from a bed of a particular nature, and drops -them in another equally well fitted for them. - -On the Inhabitants of Oceanic Islands.—We now come to the last of the three -classes of facts, which I have selected as presenting the greatest amount of -difficulty, on the view that all the individuals both of the same and of allied -species have descended from a single parent; and therefore have all proceeded -from a common birthplace, notwithstanding that in the course of time they have -come to inhabit distant points of the globe. I have already stated that I -cannot honestly admit Forbes’s view on continental extensions, which, if -legitimately followed out, would lead to the belief that within the recent -period all existing islands have been nearly or quite joined to some continent. -This view would remove many difficulties, but it would not, I think, explain -all the facts in regard to insular productions. In the following remarks I -shall not confine myself to the mere question of dispersal; but shall consider -some other facts, which bear on the truth of the two theories of independent -creation and of descent with modification. +fresh-water and even marsh-species have, both over continents and to the +most remote oceanic islands. This is strikingly shown, as remarked by +Alph. de Candolle, in large groups of terrestrial plants, which have +only a very few aquatic members; for these latter seem immediately to +acquire, as if in consequence, a very wide range. I think favourable +means of dispersal explain this fact. I have before mentioned that earth +occasionally, though rarely, adheres in some quantity to the feet and +beaks of birds. Wading birds, which frequent the muddy edges of ponds, +if suddenly flushed, would be the most likely to have muddy feet. Birds +of this order I can show are the greatest wanderers, and are +occasionally found on the most remote and barren islands in the open +ocean; they would not be likely to alight on the surface of the sea, so +that the dirt would not be washed off their feet; when making land, they +would be sure to fly to their natural fresh-water haunts. I do not +believe that botanists are aware how charged the mud of ponds is with +seeds: I have tried several little experiments, but will here give only +the most striking case: I took in February three table-spoonfuls of mud +from three different points, beneath water, on the edge of a little +pond; this mud when dry weighed only 6 3 /4 ounces; I kept it covered up +in my study for six months, pulling up and counting each plant as it +grew; the plants were of many kinds, and were altogether 537 in number; +and yet the viscid mud was all contained in a breakfast cup! Considering +these facts, I think it would be an inexplicable circumstance if +water-birds did not transport the seeds of fresh-water plants to vast +distances, and if consequently the range of these plants was not very +great. The same agency may have come into play with the eggs of some of +the smaller fresh-water animals. + +Other and unknown agencies probably have also played a part. I have +stated that fresh-water fish eat some kinds of seeds, though they reject +many other kinds after having swallowed them; even small fish swallow +seeds of moderate size, as of the yellow water-lily and Potamogeton. +Herons and other birds, century after century, have gone on daily +devouring fish; they then take flight and go to other waters, or are +blown across the sea; and we have seen that seeds retain their power of +germination, when rejected in pellets or in excrement, many hours +afterwards. When I saw the great size of the seeds of that fine +water-lily, the Nelumbium, and remembered Alph. de Candolle’s remarks on +this plant, I thought that its distribution must remain quite +inexplicable; but Audubon states that he found the seeds of the great +southern water-lily (probably, according to Dr. Hooker, the Nelumbium +luteum) in a heron’s stomach; although I do not know the fact, yet +analogy makes me believe that a heron flying to another pond and getting +a hearty meal of fish, would probably reject from its stomach a pellet +containing the seeds of the Nelumbium undigested; or the seeds might be +dropped by the bird whilst feeding its young, in the same way as fish +are known sometimes to be dropped. + +In considering these several means of distribution, it should be +remembered that when a pond or stream is first formed, for instance, on +a rising islet, it will be unoccupied; and a single seed or egg will +have a good chance of succeeding. Although there will always be a +struggle for life between the individuals of the species, however few, +already occupying any pond, yet as the number of kinds is small, +compared with those on the land, the competition will probably be less +severe between aquatic than between terrestrial species; consequently an +intruder from the waters of a foreign country, would have a better +chance of seizing on a place, than in the case of terrestrial colonists. +We should, also, remember that some, perhaps many, fresh-water +productions are low in the scale of nature, and that we have reason to +believe that such low beings change or become modified less quickly than +the high; and this will give longer time than the average for the +migration of the same aquatic species. We should not forget the +probability of many species having formerly ranged as continuously as +fresh-water productions ever can range, over immense areas, and having +subsequently become extinct in intermediate regions. But the wide +distribution of fresh-water plants and of the lower animals, whether +retaining the same identical form or in some degree modified, I believe +mainly depends on the wide dispersal of their seeds and eggs by animals, +more especially by fresh-water birds, which have large powers of flight, +and naturally travel from one to another and often distant piece of +water. Nature, like a careful gardener, thus takes her seeds from a bed +of a particular nature, and drops them in another equally well fitted +for them. + +On the Inhabitants of Oceanic Islands.—We now come to the last of the +three classes of facts, which I have selected as presenting the greatest +amount of difficulty, on the view that all the individuals both of the +same and of allied species have descended from a single parent; and +therefore have all proceeded from a common birthplace, notwithstanding +that in the course of time they have come to inhabit distant points of +the globe. I have already stated that I cannot honestly admit Forbes’s +view on continental extensions, which, if legitimately followed out, +would lead to the belief that within the recent period all existing +islands have been nearly or quite joined to some continent. This view +would remove many difficulties, but it would not, I think, explain all +the facts in regard to insular productions. In the following remarks I +shall not confine myself to the mere question of dispersal; but shall +consider some other facts, which bear on the truth of the two theories +of independent creation and of descent with modification. The species of all kinds which inhabit oceanic islands are few in number -compared with those on equal continental areas: Alph. de Candolle admits this -for plants, and Wollaston for insects. If we look to the large size and varied -stations of New Zealand, extending over 780 miles of latitude, and compare its -flowering plants, only 750 in number, with those on an equal area at the Cape -of Good Hope or in Australia, we must, I think, admit that something quite -independently of any difference in physical conditions has caused so great a -difference in number. Even the uniform county of Cambridge has 847 plants, and -the little island of Anglesea 764, but a few ferns and a few introduced plants -are included in these numbers, and the comparison in some other respects is not -quite fair. We have evidence that the barren island of Ascension aboriginally -possessed under half-a-dozen flowering plants; yet many have become naturalised -on it, as they have on New Zealand and on every other oceanic island which can -be named. In St. Helena there is reason to believe that the naturalised plants -and animals have nearly or quite exterminated many native productions. He who -admits the doctrine of the creation of each separate species, will have to -admit, that a sufficient number of the best adapted plants and animals have not -been created on oceanic islands; for man has unintentionally stocked them from -various sources far more fully and perfectly than has nature. - -Although in oceanic islands the number of kinds of inhabitants is scanty, the -proportion of endemic species (i.e. those found nowhere else in the world) is -often extremely large. If we compare, for instance, the number of the endemic -land-shells in Madeira, or of the endemic birds in the Galapagos Archipelago, -with the number found on any continent, and then compare the area of the -islands with that of the continent, we shall see that this is true. This fact -might have been expected on my theory, for, as already explained, species -occasionally arriving after long intervals in a new and isolated district, and -having to compete with new associates, will be eminently liable to -modification, and will often produce groups of modified descendants. But it by -no means follows, that, because in an island nearly all the species of one -class are peculiar, those of another class, or of another section of the same -class, are peculiar; and this difference seems to depend on the species which -do not become modified having immigrated with facility and in a body, so that -their mutual relations have not been much disturbed. Thus in the Galapagos -Islands nearly every land-bird, but only two out of the eleven marine birds, -are peculiar; and it is obvious that marine birds could arrive at these islands -more easily than land-birds. Bermuda, on the other hand, which lies at about -the same distance from North America as the Galapagos Islands do from South -America, and which has a very peculiar soil, does not possess one endemic land -bird; and we know from Mr. J. M. Jones’s admirable account of Bermuda, that -very many North American birds, during their great annual migrations, visit -either periodically or occasionally this island. Madeira does not possess one -peculiar bird, and many European and African birds are almost every year blown -there, as I am informed by Mr. E. V. Harcourt. So that these two islands of -Bermuda and Madeira have been stocked by birds, which for long ages have -struggled together in their former homes, and have become mutually adapted to -each other; and when settled in their new homes, each kind will have been kept -by the others to their proper places and habits, and will consequently have -been little liable to modification. Madeira, again, is inhabited by a wonderful -number of peculiar land-shells, whereas not one species of sea-shell is -confined to its shores: now, though we do not know how seashells are dispersed, -yet we can see that their eggs or larvæ, perhaps attached to seaweed or -floating timber, or to the feet of wading-birds, might be transported far more -easily than land-shells, across three or four hundred miles of open sea. The -different orders of insects in Madeira apparently present analogous facts. - -Oceanic islands are sometimes deficient in certain classes, and their places -are apparently occupied by the other inhabitants; in the Galapagos Islands -reptiles, and in New Zealand gigantic wingless birds, take the place of -mammals. In the plants of the Galapagos Islands, Dr. Hooker has shown that the -proportional numbers of the different orders are very different from what they -are elsewhere. Such cases are generally accounted for by the physical -conditions of the islands; but this explanation seems to me not a little -doubtful. Facility of immigration, I believe, has been at least as important as -the nature of the conditions. - -Many remarkable little facts could be given with respect to the inhabitants of -remote islands. For instance, in certain islands not tenanted by mammals, some -of the endemic plants have beautifully hooked seeds; yet few relations are more -striking than the adaptation of hooked seeds for transportal by the wool and -fur of quadrupeds. This case presents no difficulty on my view, for a hooked -seed might be transported to an island by some other means; and the plant then -becoming slightly modified, but still retaining its hooked seeds, would form an -endemic species, having as useless an appendage as any rudimentary organ,—for -instance, as the shrivelled wings under the soldered elytra of many insular -beetles. Again, islands often possess trees or bushes belonging to orders which -elsewhere include only herbaceous species; now trees, as Alph. de Candolle has -shown, generally have, whatever the cause may be, confined ranges. Hence trees -would be little likely to reach distant oceanic islands; and an herbaceous -plant, though it would have no chance of successfully competing in stature with -a fully developed tree, when established on an island and having to compete -with herbaceous plants alone, might readily gain an advantage by growing taller -and taller and overtopping the other plants. If so, natural selection would -often tend to add to the stature of herbaceous plants when growing on an -island, to whatever order they belonged, and thus convert them first into -bushes and ultimately into trees. +compared with those on equal continental areas: Alph. de Candolle admits +this for plants, and Wollaston for insects. If we look to the large size +and varied stations of New Zealand, extending over 780 miles of +latitude, and compare its flowering plants, only 750 in number, with +those on an equal area at the Cape of Good Hope or in Australia, we +must, I think, admit that something quite independently of any +difference in physical conditions has caused so great a difference in +number. Even the uniform county of Cambridge has 847 plants, and the +little island of Anglesea 764, but a few ferns and a few introduced +plants are included in these numbers, and the comparison in some other +respects is not quite fair. We have evidence that the barren island of +Ascension aboriginally possessed under half-a-dozen flowering plants; +yet many have become naturalised on it, as they have on New Zealand and +on every other oceanic island which can be named. In St. Helena there is +reason to believe that the naturalised plants and animals have nearly or +quite exterminated many native productions. He who admits the doctrine +of the creation of each separate species, will have to admit, that a +sufficient number of the best adapted plants and animals have not been +created on oceanic islands; for man has unintentionally stocked them +from various sources far more fully and perfectly than has nature. + +Although in oceanic islands the number of kinds of inhabitants is +scanty, the proportion of endemic species (i.e. those found nowhere else +in the world) is often extremely large. If we compare, for instance, the +number of the endemic land-shells in Madeira, or of the endemic birds in +the Galapagos Archipelago, with the number found on any continent, and +then compare the area of the islands with that of the continent, we +shall see that this is true. This fact might have been expected on my +theory, for, as already explained, species occasionally arriving after +long intervals in a new and isolated district, and having to compete +with new associates, will be eminently liable to modification, and will +often produce groups of modified descendants. But it by no means +follows, that, because in an island nearly all the species of one class +are peculiar, those of another class, or of another section of the same +class, are peculiar; and this difference seems to depend on the species +which do not become modified having immigrated with facility and in a +body, so that their mutual relations have not been much disturbed. Thus +in the Galapagos Islands nearly every land-bird, but only two out of the +eleven marine birds, are peculiar; and it is obvious that marine birds +could arrive at these islands more easily than land-birds. Bermuda, on +the other hand, which lies at about the same distance from North America +as the Galapagos Islands do from South America, and which has a very +peculiar soil, does not possess one endemic land bird; and we know from +Mr. J. M. Jones’s admirable account of Bermuda, that very many North +American birds, during their great annual migrations, visit either +periodically or occasionally this island. Madeira does not possess one +peculiar bird, and many European and African birds are almost every year +blown there, as I am informed by Mr. E. V. Harcourt. So that these two +islands of Bermuda and Madeira have been stocked by birds, which for +long ages have struggled together in their former homes, and have become +mutually adapted to each other; and when settled in their new homes, +each kind will have been kept by the others to their proper places and +habits, and will consequently have been little liable to modification. +Madeira, again, is inhabited by a wonderful number of peculiar +land-shells, whereas not one species of sea-shell is confined to its +shores: now, though we do not know how seashells are dispersed, yet we +can see that their eggs or larvæ, perhaps attached to seaweed or +floating timber, or to the feet of wading-birds, might be transported +far more easily than land-shells, across three or four hundred miles of +open sea. The different orders of insects in Madeira apparently present +analogous facts. + +Oceanic islands are sometimes deficient in certain classes, and their +places are apparently occupied by the other inhabitants; in the +Galapagos Islands reptiles, and in New Zealand gigantic wingless birds, +take the place of mammals. In the plants of the Galapagos Islands, Dr. +Hooker has shown that the proportional numbers of the different orders +are very different from what they are elsewhere. Such cases are +generally accounted for by the physical conditions of the islands; but +this explanation seems to me not a little doubtful. Facility of +immigration, I believe, has been at least as important as the nature of +the conditions. + +Many remarkable little facts could be given with respect to the +inhabitants of remote islands. For instance, in certain islands not +tenanted by mammals, some of the endemic plants have beautifully hooked +seeds; yet few relations are more striking than the adaptation of hooked +seeds for transportal by the wool and fur of quadrupeds. This case +presents no difficulty on my view, for a hooked seed might be +transported to an island by some other means; and the plant then +becoming slightly modified, but still retaining its hooked seeds, would +form an endemic species, having as useless an appendage as any +rudimentary organ,—for instance, as the shrivelled wings under the +soldered elytra of many insular beetles. Again, islands often possess +trees or bushes belonging to orders which elsewhere include only +herbaceous species; now trees, as Alph. de Candolle has shown, generally +have, whatever the cause may be, confined ranges. Hence trees would be +little likely to reach distant oceanic islands; and an herbaceous plant, +though it would have no chance of successfully competing in stature with +a fully developed tree, when established on an island and having to +compete with herbaceous plants alone, might readily gain an advantage by +growing taller and taller and overtopping the other plants. If so, +natural selection would often tend to add to the stature of herbaceous +plants when growing on an island, to whatever order they belonged, and +thus convert them first into bushes and ultimately into trees. With respect to the absence of whole orders on oceanic islands, Bory St. -Vincent long ago remarked that Batrachians (frogs, toads, newts) have never -been found on any of the many islands with which the great oceans are studded. -I have taken pains to verify this assertion, and I have found it strictly true. -I have, however, been assured that a frog exists on the mountains of the great -island of New Zealand; but I suspect that this exception (if the information be -correct) may be explained through glacial agency. This general absence of -frogs, toads, and newts on so many oceanic islands cannot be accounted for by -their physical conditions; indeed it seems that islands are peculiarly well -fitted for these animals; for frogs have been introduced into Madeira, the -Azores, and Mauritius, and have multiplied so as to become a nuisance. But as -these animals and their spawn are known to be immediately killed by sea-water, -on my view we can see that there would be great difficulty in their transportal -across the sea, and therefore why they do not exist on any oceanic island. But -why, on the theory of creation, they should not have been created there, it -would be very difficult to explain. - -Mammals offer another and similar case. I have carefully searched the oldest -voyages, but have not finished my search; as yet I have not found a single -instance, free from doubt, of a terrestrial mammal (excluding domesticated -animals kept by the natives) inhabiting an island situated above 300 miles from -a continent or great continental island; and many islands situated at a much -less distance are equally barren. The Falkland Islands, which are inhabited by -a wolf-like fox, come nearest to an exception; but this group cannot be -considered as oceanic, as it lies on a bank connected with the mainland; -moreover, icebergs formerly brought boulders to its western shores, and they -may have formerly transported foxes, as so frequently now happens in the arctic -regions. Yet it cannot be said that small islands will not support small -mammals, for they occur in many parts of the world on very small islands, if -close to a continent; and hardly an island can be named on which our smaller -quadrupeds have not become naturalised and greatly multiplied. It cannot be -said, on the ordinary view of creation, that there has not been time for the -creation of mammals; many volcanic islands are sufficiently ancient, as shown -by the stupendous degradation which they have suffered and by their tertiary -strata: there has also been time for the production of endemic species -belonging to other classes; and on continents it is thought that mammals appear -and disappear at a quicker rate than other and lower animals. Though -terrestrial mammals do not occur on oceanic islands, ærial mammals do occur on -almost every island. New Zealand possesses two bats found nowhere else in the -world: Norfolk Island, the Viti Archipelago, the Bonin Islands, the Caroline -and Marianne Archipelagoes, and Mauritius, all possess their peculiar bats. -Why, it may be asked, has the supposed creative force produced bats and no -other mammals on remote islands? On my view this question can easily be -answered; for no terrestrial mammal can be transported across a wide space of -sea, but bats can fly across. Bats have been seen wandering by day far over the -Atlantic Ocean; and two North American species either regularly or occasionally -visit Bermuda, at the distance of 600 miles from the mainland. I hear from Mr. -Tomes, who has specially studied this family, that many of the same species -have enormous ranges, and are found on continents and on far distant islands. -Hence we have only to suppose that such wandering species have been modified -through natural selection in their new homes in relation to their new position, -and we can understand the presence of endemic bats on islands, with the absence +Vincent long ago remarked that Batrachians (frogs, toads, newts) have +never been found on any of the many islands with which the great oceans +are studded. I have taken pains to verify this assertion, and I have +found it strictly true. I have, however, been assured that a frog +exists on the mountains of the great island of New Zealand; but I +suspect that this exception (if the information be correct) may be +explained through glacial agency. This general absence of frogs, toads, +and newts on so many oceanic islands cannot be accounted for by their +physical conditions; indeed it seems that islands are peculiarly well +fitted for these animals; for frogs have been introduced into Madeira, +the Azores, and Mauritius, and have multiplied so as to become a +nuisance. But as these animals and their spawn are known to be +immediately killed by sea-water, on my view we can see that there would +be great difficulty in their transportal across the sea, and therefore +why they do not exist on any oceanic island. But why, on the theory of +creation, they should not have been created there, it would be very +difficult to explain. + +Mammals offer another and similar case. I have carefully searched the +oldest voyages, but have not finished my search; as yet I have not found +a single instance, free from doubt, of a terrestrial mammal (excluding +domesticated animals kept by the natives) inhabiting an island situated +above 300 miles from a continent or great continental island; and many +islands situated at a much less distance are equally barren. The +Falkland Islands, which are inhabited by a wolf-like fox, come nearest +to an exception; but this group cannot be considered as oceanic, as it +lies on a bank connected with the mainland; moreover, icebergs formerly +brought boulders to its western shores, and they may have formerly +transported foxes, as so frequently now happens in the arctic regions. +Yet it cannot be said that small islands will not support small mammals, +for they occur in many parts of the world on very small islands, if +close to a continent; and hardly an island can be named on which our +smaller quadrupeds have not become naturalised and greatly multiplied. +It cannot be said, on the ordinary view of creation, that there has not +been time for the creation of mammals; many volcanic islands are +sufficiently ancient, as shown by the stupendous degradation which they +have suffered and by their tertiary strata: there has also been time for +the production of endemic species belonging to other classes; and on +continents it is thought that mammals appear and disappear at a quicker +rate than other and lower animals. Though terrestrial mammals do not +occur on oceanic islands, ærial mammals do occur on almost every island. +New Zealand possesses two bats found nowhere else in the world: Norfolk +Island, the Viti Archipelago, the Bonin Islands, the Caroline and +Marianne Archipelagoes, and Mauritius, all possess their peculiar bats. +Why, it may be asked, has the supposed creative force produced bats and +no other mammals on remote islands? On my view this question can easily +be answered; for no terrestrial mammal can be transported across a wide +space of sea, but bats can fly across. Bats have been seen wandering by +day far over the Atlantic Ocean; and two North American species either +regularly or occasionally visit Bermuda, at the distance of 600 miles +from the mainland. I hear from Mr. Tomes, who has specially studied +this family, that many of the same species have enormous ranges, and are +found on continents and on far distant islands. Hence we have only to +suppose that such wandering species have been modified through natural +selection in their new homes in relation to their new position, and we +can understand the presence of endemic bats on islands, with the absence of all terrestrial mammals. -Besides the absence of terrestrial mammals in relation to the remoteness of -islands from continents, there is also a relation, to a certain extent -independent of distance, between the depth of the sea separating an island from -the neighbouring mainland, and the presence in both of the same mammiferous -species or of allied species in a more or less modified condition. Mr. Windsor -Earl has made some striking observations on this head in regard to the great -Malay Archipelago, which is traversed near Celebes by a space of deep ocean; -and this space separates two widely distinct mammalian faunas. On either side -the islands are situated on moderately deep submarine banks, and they are +Besides the absence of terrestrial mammals in relation to the remoteness +of islands from continents, there is also a relation, to a certain +extent independent of distance, between the depth of the sea separating +an island from the neighbouring mainland, and the presence in both of +the same mammiferous species or of allied species in a more or less +modified condition. Mr. Windsor Earl has made some striking observations +on this head in regard to the great Malay Archipelago, which is +traversed near Celebes by a space of deep ocean; and this space +separates two widely distinct mammalian faunas. On either side the +islands are situated on moderately deep submarine banks, and they are inhabited by closely allied or identical quadrupeds. No doubt some few -anomalies occur in this great archipelago, and there is much difficulty in -forming a judgment in some cases owing to the probable naturalisation of -certain mammals through man’s agency; but we shall soon have much light thrown -on the natural history of this archipelago by the admirable zeal and researches -of Mr. Wallace. I have not as yet had time to follow up this subject in all -other quarters of the world; but as far as I have gone, the relation generally -holds good. We see Britain separated by a shallow channel from Europe, and the -mammals are the same on both sides; we meet with analogous facts on many -islands separated by similar channels from Australia. The West Indian Islands -stand on a deeply submerged bank, nearly 1000 fathoms in depth, and here we -find American forms, but the species and even the genera are distinct. As the -amount of modification in all cases depends to a certain degree on the lapse of -time, and as during changes of level it is obvious that islands separated by -shallow channels are more likely to have been continuously united within a -recent period to the mainland than islands separated by deeper channels, we can -understand the frequent relation between the depth of the sea and the degree of -affinity of the mammalian inhabitants of islands with those of a neighbouring -continent,—an inexplicable relation on the view of independent acts of -creation. - -All the foregoing remarks on the inhabitants of oceanic islands,—namely, the -scarcity of kinds—the richness in endemic forms in particular classes or -sections of classes,—the absence of whole groups, as of batrachians, and of -terrestrial mammals notwithstanding the presence of ærial bats,—the singular -proportions of certain orders of plants,—herbaceous forms having been developed -into trees, etc.,—seem to me to accord better with the view of occasional means -of transport having been largely efficient in the long course of time, than -with the view of all our oceanic islands having been formerly connected by +anomalies occur in this great archipelago, and there is much difficulty +in forming a judgment in some cases owing to the probable naturalisation +of certain mammals through man’s agency; but we shall soon have much +light thrown on the natural history of this archipelago by the admirable +zeal and researches of Mr. Wallace. I have not as yet had time to follow +up this subject in all other quarters of the world; but as far as I have +gone, the relation generally holds good. We see Britain separated by a +shallow channel from Europe, and the mammals are the same on both sides; +we meet with analogous facts on many islands separated by similar +channels from Australia. The West Indian Islands stand on a deeply +submerged bank, nearly 1000 fathoms in depth, and here we find American +forms, but the species and even the genera are distinct. As the amount +of modification in all cases depends to a certain degree on the lapse of +time, and as during changes of level it is obvious that islands +separated by shallow channels are more likely to have been continuously +united within a recent period to the mainland than islands separated by +deeper channels, we can understand the frequent relation between the +depth of the sea and the degree of affinity of the mammalian inhabitants +of islands with those of a neighbouring continent,—an inexplicable +relation on the view of independent acts of creation. + +All the foregoing remarks on the inhabitants of oceanic islands,—namely, +the scarcity of kinds—the richness in endemic forms in particular +classes or sections of classes,—the absence of whole groups, as of +batrachians, and of terrestrial mammals notwithstanding the presence of +ærial bats,—the singular proportions of certain orders of +plants,—herbaceous forms having been developed into trees, etc.,—seem to +me to accord better with the view of occasional means of transport +having been largely efficient in the long course of time, than with the +view of all our oceanic islands having been formerly connected by continuous land with the nearest continent; for on this latter view the migration would probably have been more complete; and if modification be -admitted, all the forms of life would have been more equally modified, in -accordance with the paramount importance of the relation of organism to -organism. - -I do not deny that there are many and grave difficulties in understanding how -several of the inhabitants of the more remote islands, whether still retaining -the same specific form or modified since their arrival, could have reached -their present homes. But the probability of many islands having existed as -halting-places, of which not a wreck now remains, must not be overlooked. I -will here give a single instance of one of the cases of difficulty. Almost all -oceanic islands, even the most isolated and smallest, are inhabited by -land-shells, generally by endemic species, but sometimes by species found -elsewhere. Dr. Aug. A. Gould has given several interesting cases in regard to -the land-shells of the islands of the Pacific. Now it is notorious that -land-shells are very easily killed by salt; their eggs, at least such as I have -tried, sink in sea-water and are killed by it. Yet there must be, on my view, -some unknown, but highly efficient means for their transportal. Would the -just-hatched young occasionally crawl on and adhere to the feet of birds -roosting on the ground, and thus get transported? It occurred to me that -land-shells, when hybernating and having a membranous diaphragm over the mouth -of the shell, might be floated in chinks of drifted timber across moderately -wide arms of the sea. And I found that several species did in this state -withstand uninjured an immersion in sea-water during seven days: one of these -shells was the Helix pomatia, and after it had again hybernated I put it in -sea-water for twenty days, and it perfectly recovered. As this species has a -thick calcareous operculum, I removed it, and when it had formed a new -membranous one, I immersed it for fourteen days in sea-water, and it recovered -and crawled away: but more experiments are wanted on this head. - -The most striking and important fact for us in regard to the inhabitants of -islands, is their affinity to those of the nearest mainland, without being -actually the same species. Numerous instances could be given of this fact. I -will give only one, that of the Galapagos Archipelago, situated under the -equator, between 500 and 600 miles from the shores of South America. Here -almost every product of the land and water bears the unmistakeable stamp of the -American continent. There are twenty-six land birds, and twenty-five of these -are ranked by Mr. Gould as distinct species, supposed to have been created -here; yet the close affinity of most of these birds to American species in -every character, in their habits, gestures, and tones of voice, was manifest. -So it is with the other animals, and with nearly all the plants, as shown by -Dr. Hooker in his admirable memoir on the Flora of this archipelago. The -naturalist, looking at the inhabitants of these volcanic islands in the -Pacific, distant several hundred miles from the continent, yet feels that he is -standing on American land. Why should this be so? why should the species which -are supposed to have been created in the Galapagos Archipelago, and nowhere -else, bear so plain a stamp of affinity to those created in America? There is -nothing in the conditions of life, in the geological nature of the islands, in -their height or climate, or in the proportions in which the several classes are -associated together, which resembles closely the conditions of the South -American coast: in fact there is a considerable dissimilarity in all these -respects. On the other hand, there is a considerable degree of resemblance in -the volcanic nature of the soil, in climate, height, and size of the islands, -between the Galapagos and Cape de Verde Archipelagos: but what an entire and -absolute difference in their inhabitants! The inhabitants of the Cape de Verde -Islands are related to those of Africa, like those of the Galapagos to America. -I believe this grand fact can receive no sort of explanation on the ordinary -view of independent creation; whereas on the view here maintained, it is -obvious that the Galapagos Islands would be likely to receive colonists, -whether by occasional means of transport or by formerly continuous land, from -America; and the Cape de Verde Islands from Africa; and that such colonists -would be liable to modification;—the principle of inheritance still betraying -their original birthplace. - -Many analogous facts could be given: indeed it is an almost universal rule that -the endemic productions of islands are related to those of the nearest -continent, or of other near islands. The exceptions are few, and most of them -can be explained. Thus the plants of Kerguelen Land, though standing nearer to -Africa than to America, are related, and that very closely, as we know from Dr. -Hooker’s account, to those of America: but on the view that this island has -been mainly stocked by seeds brought with earth and stones on icebergs, drifted -by the prevailing currents, this anomaly disappears. New Zealand in its endemic -plants is much more closely related to Australia, the nearest mainland, than to -any other region: and this is what might have been expected; but it is also -plainly related to South America, which, although the next nearest continent, -is so enormously remote, that the fact becomes an anomaly. But this difficulty -almost disappears on the view that both New Zealand, South America, and other -southern lands were long ago partially stocked from a nearly intermediate -though distant point, namely from the antarctic islands, when they were clothed -with vegetation, before the commencement of the Glacial period. The affinity, -which, though feeble, I am assured by Dr. Hooker is real, between the flora of -the south-western corner of Australia and of the Cape of Good Hope, is a far -more remarkable case, and is at present inexplicable: but this affinity is -confined to the plants, and will, I do not doubt, be some day explained. - -The law which causes the inhabitants of an archipelago, though specifically -distinct, to be closely allied to those of the nearest continent, we sometimes -see displayed on a small scale, yet in a most interesting manner, within the -limits of the same archipelago. Thus the several islands of the Galapagos -Archipelago are tenanted, as I have elsewhere shown, in a quite marvellous -manner, by very closely related species; so that the inhabitants of each -separate island, though mostly distinct, are related in an incomparably closer -degree to each other than to the inhabitants of any other part of the world. -And this is just what might have been expected on my view, for the islands are -situated so near each other that they would almost certainly receive immigrants -from the same original source, or from each other. But this dissimilarity -between the endemic inhabitants of the islands may be used as an argument -against my views; for it may be asked, how has it happened in the several -islands situated within sight of each other, having the same geological nature, -the same height, climate, etc., that many of the immigrants should have been -differently modified, though only in a small degree. This long appeared to me a -great difficulty: but it arises in chief part from the deeply-seated error of -considering the physical conditions of a country as the most important for its -inhabitants; whereas it cannot, I think, be disputed that the nature of the -other inhabitants, with which each has to compete, is at least as important, -and generally a far more important element of success. Now if we look to those -inhabitants of the Galapagos Archipelago which are found in other parts of the -world (laying on one side for the moment the endemic species, which cannot be -here fairly included, as we are considering how they have come to be modified -since their arrival), we find a considerable amount of difference in the -several islands. This difference might indeed have been expected on the view of -the islands having been stocked by occasional means of transport—a seed, for -instance, of one plant having been brought to one island, and that of another -plant to another island. Hence when in former times an immigrant settled on any -one or more of the islands, or when it subsequently spread from one island to -another, it would undoubtedly be exposed to different conditions of life in the -different islands, for it would have to compete with different sets of -organisms: a plant, for instance, would find the best-fitted ground more -perfectly occupied by distinct plants in one island than in another, and it -would be exposed to the attacks of somewhat different enemies. If then it -varied, natural selection would probably favour different varieties in the -different islands. Some species, however, might spread and yet retain the same -character throughout the group, just as we see on continents some species -spreading widely and remaining the same. - -The really surprising fact in this case of the Galapagos Archipelago, and in a -lesser degree in some analogous instances, is that the new species formed in -the separate islands have not quickly spread to the other islands. But the -islands, though in sight of each other, are separated by deep arms of the sea, -in most cases wider than the British Channel, and there is no reason to suppose -that they have at any former period been continuously united. The currents of -the sea are rapid and sweep across the archipelago, and gales of wind are -extraordinarily rare; so that the islands are far more effectually separated -from each other than they appear to be on a map. Nevertheless a good many -species, both those found in other parts of the world and those confined to the -archipelago, are common to the several islands, and we may infer from certain -facts that these have probably spread from some one island to the others. But -we often take, I think, an erroneous view of the probability of closely allied -species invading each other’s territory, when put into free intercommunication. -Undoubtedly if one species has any advantage whatever over another, it will in -a very brief time wholly or in part supplant it; but if both are equally well -fitted for their own places in nature, both probably will hold their own places -and keep separate for almost any length of time. Being familiar with the fact +admitted, all the forms of life would have been more equally modified, +in accordance with the paramount importance of the relation of organism +to organism. + +I do not deny that there are many and grave difficulties in +understanding how several of the inhabitants of the more remote islands, +whether still retaining the same specific form or modified since their +arrival, could have reached their present homes. But the probability of +many islands having existed as halting-places, of which not a wreck now +remains, must not be overlooked. I will here give a single instance of +one of the cases of difficulty. Almost all oceanic islands, even the +most isolated and smallest, are inhabited by land-shells, generally by +endemic species, but sometimes by species found elsewhere. Dr. Aug. A. +Gould has given several interesting cases in regard to the land-shells +of the islands of the Pacific. Now it is notorious that land-shells are +very easily killed by salt; their eggs, at least such as I have tried, +sink in sea-water and are killed by it. Yet there must be, on my view, +some unknown, but highly efficient means for their transportal. Would +the just-hatched young occasionally crawl on and adhere to the feet of +birds roosting on the ground, and thus get transported? It occurred to +me that land-shells, when hybernating and having a membranous diaphragm +over the mouth of the shell, might be floated in chinks of drifted +timber across moderately wide arms of the sea. And I found that several +species did in this state withstand uninjured an immersion in sea-water +during seven days: one of these shells was the Helix pomatia, and after +it had again hybernated I put it in sea-water for twenty days, and it +perfectly recovered. As this species has a thick calcareous operculum, I +removed it, and when it had formed a new membranous one, I immersed it +for fourteen days in sea-water, and it recovered and crawled away: but +more experiments are wanted on this head. + +The most striking and important fact for us in regard to the inhabitants +of islands, is their affinity to those of the nearest mainland, without +being actually the same species. Numerous instances could be given of +this fact. I will give only one, that of the Galapagos Archipelago, +situated under the equator, between 500 and 600 miles from the shores of +South America. Here almost every product of the land and water bears the +unmistakeable stamp of the American continent. There are twenty-six land +birds, and twenty-five of these are ranked by Mr. Gould as distinct +species, supposed to have been created here; yet the close affinity of +most of these birds to American species in every character, in their +habits, gestures, and tones of voice, was manifest. So it is with the +other animals, and with nearly all the plants, as shown by Dr. Hooker in +his admirable memoir on the Flora of this archipelago. The naturalist, +looking at the inhabitants of these volcanic islands in the Pacific, +distant several hundred miles from the continent, yet feels that he is +standing on American land. Why should this be so? why should the species +which are supposed to have been created in the Galapagos Archipelago, +and nowhere else, bear so plain a stamp of affinity to those created in +America? There is nothing in the conditions of life, in the geological +nature of the islands, in their height or climate, or in the proportions +in which the several classes are associated together, which resembles +closely the conditions of the South American coast: in fact there is a +considerable dissimilarity in all these respects. On the other hand, +there is a considerable degree of resemblance in the volcanic nature of +the soil, in climate, height, and size of the islands, between the +Galapagos and Cape de Verde Archipelagos: but what an entire and +absolute difference in their inhabitants! The inhabitants of the Cape de +Verde Islands are related to those of Africa, like those of the +Galapagos to America. I believe this grand fact can receive no sort of +explanation on the ordinary view of independent creation; whereas on the +view here maintained, it is obvious that the Galapagos Islands would be +likely to receive colonists, whether by occasional means of transport or +by formerly continuous land, from America; and the Cape de Verde Islands +from Africa; and that such colonists would be liable to +modification;—the principle of inheritance still betraying their +original birthplace. + +Many analogous facts could be given: indeed it is an almost universal +rule that the endemic productions of islands are related to those of the +nearest continent, or of other near islands. The exceptions are few, and +most of them can be explained. Thus the plants of Kerguelen Land, though +standing nearer to Africa than to America, are related, and that very +closely, as we know from Dr. Hooker’s account, to those of America: but +on the view that this island has been mainly stocked by seeds brought +with earth and stones on icebergs, drifted by the prevailing currents, +this anomaly disappears. New Zealand in its endemic plants is much more +closely related to Australia, the nearest mainland, than to any other +region: and this is what might have been expected; but it is also +plainly related to South America, which, although the next nearest +continent, is so enormously remote, that the fact becomes an anomaly. +But this difficulty almost disappears on the view that both New Zealand, +South America, and other southern lands were long ago partially stocked +from a nearly intermediate though distant point, namely from the +antarctic islands, when they were clothed with vegetation, before the +commencement of the Glacial period. The affinity, which, though feeble, +I am assured by Dr. Hooker is real, between the flora of the +south-western corner of Australia and of the Cape of Good Hope, is a far +more remarkable case, and is at present inexplicable: but this affinity +is confined to the plants, and will, I do not doubt, be some day +explained. + +The law which causes the inhabitants of an archipelago, though +specifically distinct, to be closely allied to those of the nearest +continent, we sometimes see displayed on a small scale, yet in a most +interesting manner, within the limits of the same archipelago. Thus the +several islands of the Galapagos Archipelago are tenanted, as I have +elsewhere shown, in a quite marvellous manner, by very closely related +species; so that the inhabitants of each separate island, though mostly +distinct, are related in an incomparably closer degree to each other +than to the inhabitants of any other part of the world. And this is +just what might have been expected on my view, for the islands are +situated so near each other that they would almost certainly receive +immigrants from the same original source, or from each other. But this +dissimilarity between the endemic inhabitants of the islands may be used +as an argument against my views; for it may be asked, how has it +happened in the several islands situated within sight of each other, +having the same geological nature, the same height, climate, etc., that +many of the immigrants should have been differently modified, though +only in a small degree. This long appeared to me a great difficulty: but +it arises in chief part from the deeply-seated error of considering the +physical conditions of a country as the most important for its +inhabitants; whereas it cannot, I think, be disputed that the nature of +the other inhabitants, with which each has to compete, is at least as +important, and generally a far more important element of success. Now if +we look to those inhabitants of the Galapagos Archipelago which are +found in other parts of the world (laying on one side for the moment the +endemic species, which cannot be here fairly included, as we are +considering how they have come to be modified since their arrival), we +find a considerable amount of difference in the several islands. This +difference might indeed have been expected on the view of the islands +having been stocked by occasional means of transport—a seed, for +instance, of one plant having been brought to one island, and that of +another plant to another island. Hence when in former times an immigrant +settled on any one or more of the islands, or when it subsequently +spread from one island to another, it would undoubtedly be exposed to +different conditions of life in the different islands, for it would have +to compete with different sets of organisms: a plant, for instance, +would find the best-fitted ground more perfectly occupied by distinct +plants in one island than in another, and it would be exposed to the +attacks of somewhat different enemies. If then it varied, natural +selection would probably favour different varieties in the different +islands. Some species, however, might spread and yet retain the same +character throughout the group, just as we see on continents some +species spreading widely and remaining the same. + +The really surprising fact in this case of the Galapagos Archipelago, +and in a lesser degree in some analogous instances, is that the new +species formed in the separate islands have not quickly spread to the +other islands. But the islands, though in sight of each other, are +separated by deep arms of the sea, in most cases wider than the British +Channel, and there is no reason to suppose that they have at any former +period been continuously united. The currents of the sea are rapid and +sweep across the archipelago, and gales of wind are extraordinarily +rare; so that the islands are far more effectually separated from each +other than they appear to be on a map. Nevertheless a good many species, +both those found in other parts of the world and those confined to the +archipelago, are common to the several islands, and we may infer from +certain facts that these have probably spread from some one island to +the others. But we often take, I think, an erroneous view of the +probability of closely allied species invading each other’s territory, +when put into free intercommunication. Undoubtedly if one species has +any advantage whatever over another, it will in a very brief time wholly +or in part supplant it; but if both are equally well fitted for their +own places in nature, both probably will hold their own places and keep +separate for almost any length of time. Being familiar with the fact that many species, naturalised through man’s agency, have spread with -astonishing rapidity over new countries, we are apt to infer that most species -would thus spread; but we should remember that the forms which become -naturalised in new countries are not generally closely allied to the aboriginal -inhabitants, but are very distinct species, belonging in a large proportion of -cases, as shown by Alph. de Candolle, to distinct genera. In the Galapagos -Archipelago, many even of the birds, though so well adapted for flying from -island to island, are distinct on each; thus there are three closely-allied -species of mocking-thrush, each confined to its own island. Now let us suppose -the mocking-thrush of Chatham Island to be blown to Charles Island, which has -its own mocking-thrush: why should it succeed in establishing itself there? We -may safely infer that Charles Island is well stocked with its own species, for -annually more eggs are laid there than can possibly be reared; and we may infer -that the mocking-thrush peculiar to Charles Island is at least as well fitted -for its home as is the species peculiar to Chatham Island. Sir C. Lyell and Mr. -Wollaston have communicated to me a remarkable fact bearing on this subject; -namely, that Madeira and the adjoining islet of Porto Santo possess many -distinct but representative land-shells, some of which live in crevices of -stone; and although large quantities of stone are annually transported from -Porto Santo to Madeira, yet this latter island has not become colonised by the -Porto Santo species: nevertheless both islands have been colonised by some -European land-shells, which no doubt had some advantage over the indigenous -species. From these considerations I think we need not greatly marvel at the -endemic and representative species, which inhabit the several islands of the -Galapagos Archipelago, not having universally spread from island to island. In -many other instances, as in the several districts of the same continent, +astonishing rapidity over new countries, we are apt to infer that most +species would thus spread; but we should remember that the forms which +become naturalised in new countries are not generally closely allied to +the aboriginal inhabitants, but are very distinct species, belonging in +a large proportion of cases, as shown by Alph. de Candolle, to distinct +genera. In the Galapagos Archipelago, many even of the birds, though so +well adapted for flying from island to island, are distinct on each; +thus there are three closely-allied species of mocking-thrush, each +confined to its own island. Now let us suppose the mocking-thrush of +Chatham Island to be blown to Charles Island, which has its own +mocking-thrush: why should it succeed in establishing itself there? We +may safely infer that Charles Island is well stocked with its own +species, for annually more eggs are laid there than can possibly be +reared; and we may infer that the mocking-thrush peculiar to Charles +Island is at least as well fitted for its home as is the species +peculiar to Chatham Island. Sir C. Lyell and Mr. Wollaston have +communicated to me a remarkable fact bearing on this subject; namely, +that Madeira and the adjoining islet of Porto Santo possess many +distinct but representative land-shells, some of which live in crevices +of stone; and although large quantities of stone are annually +transported from Porto Santo to Madeira, yet this latter island has not +become colonised by the Porto Santo species: nevertheless both islands +have been colonised by some European land-shells, which no doubt had +some advantage over the indigenous species. From these considerations I +think we need not greatly marvel at the endemic and representative +species, which inhabit the several islands of the Galapagos Archipelago, +not having universally spread from island to island. In many other +instances, as in the several districts of the same continent, pre-occupation has probably played an important part in checking the -commingling of species under the same conditions of life. Thus, the south-east -and south-west corners of Australia have nearly the same physical conditions, -and are united by continuous land, yet they are inhabited by a vast number of -distinct mammals, birds, and plants. - -The principle which determines the general character of the fauna and flora of -oceanic islands, namely, that the inhabitants, when not identically the same, -yet are plainly related to the inhabitants of that region whence colonists -could most readily have been derived,—the colonists having been subsequently -modified and better fitted to their new homes,—is of the widest application -throughout nature. We see this on every mountain, in every lake and marsh. For -Alpine species, excepting in so far as the same forms, chiefly of plants, have -spread widely throughout the world during the recent Glacial epoch, are related -to those of the surrounding lowlands;—thus we have in South America, Alpine -humming-birds, Alpine rodents, Alpine plants, etc., all of strictly American -forms, and it is obvious that a mountain, as it became slowly upheaved, would -naturally be colonised from the surrounding lowlands. So it is with the -inhabitants of lakes and marshes, excepting in so far as great facility of -transport has given the same general forms to the whole world. We see this same -principle in the blind animals inhabiting the caves of America and of Europe. -Other analogous facts could be given. And it will, I believe, be universally -found to be true, that wherever in two regions, let them be ever so distant, -many closely allied or representative species occur, there will likewise be -found some identical species, showing, in accordance with the foregoing view, -that at some former period there has been intercommunication or migration -between the two regions. And wherever many closely-allied species occur, there -will be found many forms which some naturalists rank as distinct species, and -some as varieties; these doubtful forms showing us the steps in the process of -modification. - -This relation between the power and extent of migration of a species, either at -the present time or at some former period under different physical conditions, -and the existence at remote points of the world of other species allied to it, -is shown in another and more general way. Mr. Gould remarked to me long ago, -that in those genera of birds which range over the world, many of the species -have very wide ranges. I can hardly doubt that this rule is generally true, -though it would be difficult to prove it. Amongst mammals, we see it strikingly -displayed in Bats, and in a lesser degree in the Felidæ and Canidæ. We see it, -if we compare the distribution of butterflies and beetles. So it is with most -fresh-water productions, in which so many genera range over the world, and many -individual species have enormous ranges. It is not meant that in world-ranging -genera all the species have a wide range, or even that they have on an average -a wide range; but only that some of the species range very widely; for the -facility with which widely-ranging species vary and give rise to new forms will -largely determine their average range. For instance, two varieties of the same -species inhabit America and Europe, and the species thus has an immense range; -but, if the variation had been a little greater, the two varieties would have -been ranked as distinct species, and the common range would have been greatly -reduced. Still less is it meant, that a species which apparently has the -capacity of crossing barriers and ranging widely, as in the case of certain -powerfully-winged birds, will necessarily range widely; for we should never -forget that to range widely implies not only the power of crossing barriers, -but the more important power of being victorious in distant lands in the -struggle for life with foreign associates. But on the view of all the species -of a genus having descended from a single parent, though now distributed to the -most remote points of the world, we ought to find, and I believe as a general -rule we do find, that some at least of the species range very widely; for it is -necessary that the unmodified parent should range widely, undergoing -modification during its diffusion, and should place itself under diverse -conditions favourable for the conversion of its offspring, firstly into new +commingling of species under the same conditions of life. Thus, the +south-east and south-west corners of Australia have nearly the same +physical conditions, and are united by continuous land, yet they are +inhabited by a vast number of distinct mammals, birds, and plants. + +The principle which determines the general character of the fauna and +flora of oceanic islands, namely, that the inhabitants, when not +identically the same, yet are plainly related to the inhabitants of that +region whence colonists could most readily have been derived,—the +colonists having been subsequently modified and better fitted to their +new homes,—is of the widest application throughout nature. We see this +on every mountain, in every lake and marsh. For Alpine species, +excepting in so far as the same forms, chiefly of plants, have spread +widely throughout the world during the recent Glacial epoch, are related +to those of the surrounding lowlands;—thus we have in South America, +Alpine humming-birds, Alpine rodents, Alpine plants, etc., all of +strictly American forms, and it is obvious that a mountain, as it became +slowly upheaved, would naturally be colonised from the surrounding +lowlands. So it is with the inhabitants of lakes and marshes, excepting +in so far as great facility of transport has given the same general +forms to the whole world. We see this same principle in the blind +animals inhabiting the caves of America and of Europe. Other analogous +facts could be given. And it will, I believe, be universally found to be +true, that wherever in two regions, let them be ever so distant, many +closely allied or representative species occur, there will likewise be +found some identical species, showing, in accordance with the foregoing +view, that at some former period there has been intercommunication or +migration between the two regions. And wherever many closely-allied +species occur, there will be found many forms which some naturalists +rank as distinct species, and some as varieties; these doubtful forms +showing us the steps in the process of modification. + +This relation between the power and extent of migration of a species, +either at the present time or at some former period under different +physical conditions, and the existence at remote points of the world of +other species allied to it, is shown in another and more general way. +Mr. Gould remarked to me long ago, that in those genera of birds which +range over the world, many of the species have very wide ranges. I can +hardly doubt that this rule is generally true, though it would be +difficult to prove it. Amongst mammals, we see it strikingly displayed +in Bats, and in a lesser degree in the Felidæ and Canidæ. We see it, if +we compare the distribution of butterflies and beetles. So it is with +most fresh-water productions, in which so many genera range over the +world, and many individual species have enormous ranges. It is not meant +that in world-ranging genera all the species have a wide range, or even +that they have on an average a wide range; but only that some of the +species range very widely; for the facility with which widely-ranging +species vary and give rise to new forms will largely determine their +average range. For instance, two varieties of the same species inhabit +America and Europe, and the species thus has an immense range; but, if +the variation had been a little greater, the two varieties would have +been ranked as distinct species, and the common range would have been +greatly reduced. Still less is it meant, that a species which apparently +has the capacity of crossing barriers and ranging widely, as in the case +of certain powerfully-winged birds, will necessarily range widely; for +we should never forget that to range widely implies not only the power +of crossing barriers, but the more important power of being victorious +in distant lands in the struggle for life with foreign associates. But +on the view of all the species of a genus having descended from a single +parent, though now distributed to the most remote points of the world, +we ought to find, and I believe as a general rule we do find, that some +at least of the species range very widely; for it is necessary that the +unmodified parent should range widely, undergoing modification during +its diffusion, and should place itself under diverse conditions +favourable for the conversion of its offspring, firstly into new varieties and ultimately into new species. -In considering the wide distribution of certain genera, we should bear in mind -that some are extremely ancient, and must have branched off from a common -parent at a remote epoch; so that in such cases there will have been ample time -for great climatal and geographical changes and for accidents of transport; and -consequently for the migration of some of the species into all quarters of the -world, where they may have become slightly modified in relation to their new -conditions. There is, also, some reason to believe from geological evidence -that organisms low in the scale within each great class, generally change at a -slower rate than the higher forms; and consequently the lower forms will have -had a better chance of ranging widely and of still retaining the same specific -character. This fact, together with the seeds and eggs of many low forms being -very minute and better fitted for distant transportation, probably accounts for -a law which has long been observed, and which has lately been admirably -discussed by Alph. de Candolle in regard to plants, namely, that the lower any -group of organisms is, the more widely it is apt to range. - -The relations just discussed,—namely, low and slowly-changing organisms ranging -more widely than the high,—some of the species of widely-ranging genera -themselves ranging widely,—such facts, as alpine, lacustrine, and marsh -productions being related (with the exceptions before specified) to those on -the surrounding low lands and dry lands, though these stations are so -different—the very close relation of the distinct species which inhabit the -islets of the same archipelago,—and especially the striking relation of the -inhabitants of each whole archipelago or island to those of the nearest -mainland,—are, I think, utterly inexplicable on the ordinary view of the -independent creation of each species, but are explicable on the view of -colonisation from the nearest and readiest source, together with the subsequent -modification and better adaptation of the colonists to their new homes. - -Summary of last and present Chapters.—In these chapters I have endeavoured to -show, that if we make due allowance for our ignorance of the full effects of -all the changes of climate and of the level of the land, which have certainly -occurred within the recent period, and of other similar changes which may have -occurred within the same period; if we remember how profoundly ignorant we are -with respect to the many and curious means of occasional transport,—a subject -which has hardly ever been properly experimentised on; if we bear in mind how -often a species may have ranged continuously over a wide area, and then have -become extinct in the intermediate tracts, I think the difficulties in -believing that all the individuals of the same species, wherever located, have -descended from the same parents, are not insuperable. And we are led to this -conclusion, which has been arrived at by many naturalists under the designation -of single centres of creation, by some general considerations, more especially -from the importance of barriers and from the analogical distribution of -sub-genera, genera, and families. - -With respect to the distinct species of the same genus, which on my theory must -have spread from one parent-source; if we make the same allowances as before -for our ignorance, and remember that some forms of life change most slowly, -enormous periods of time being thus granted for their migration, I do not think -that the difficulties are insuperable; though they often are in this case, and -in that of the individuals of the same species, extremely grave. +In considering the wide distribution of certain genera, we should bear +in mind that some are extremely ancient, and must have branched off from +a common parent at a remote epoch; so that in such cases there will have +been ample time for great climatal and geographical changes and for +accidents of transport; and consequently for the migration of some of +the species into all quarters of the world, where they may have become +slightly modified in relation to their new conditions. There is, also, +some reason to believe from geological evidence that organisms low in +the scale within each great class, generally change at a slower rate +than the higher forms; and consequently the lower forms will have had a +better chance of ranging widely and of still retaining the same specific +character. This fact, together with the seeds and eggs of many low forms +being very minute and better fitted for distant transportation, probably +accounts for a law which has long been observed, and which has lately +been admirably discussed by Alph. de Candolle in regard to plants, +namely, that the lower any group of organisms is, the more widely it is +apt to range. + +The relations just discussed,—namely, low and slowly-changing organisms +ranging more widely than the high,—some of the species of widely-ranging +genera themselves ranging widely,—such facts, as alpine, lacustrine, and +marsh productions being related (with the exceptions before specified) +to those on the surrounding low lands and dry lands, though these +stations are so different—the very close relation of the distinct +species which inhabit the islets of the same archipelago,—and especially +the striking relation of the inhabitants of each whole archipelago or +island to those of the nearest mainland,—are, I think, utterly +inexplicable on the ordinary view of the independent creation of each +species, but are explicable on the view of colonisation from the nearest +and readiest source, together with the subsequent modification and +better adaptation of the colonists to their new homes. + +Summary of last and present Chapters.—In these chapters I have +endeavoured to show, that if we make due allowance for our ignorance of +the full effects of all the changes of climate and of the level of the +land, which have certainly occurred within the recent period, and of +other similar changes which may have occurred within the same period; if +we remember how profoundly ignorant we are with respect to the many and +curious means of occasional transport,—a subject which has hardly ever +been properly experimentised on; if we bear in mind how often a species +may have ranged continuously over a wide area, and then have become +extinct in the intermediate tracts, I think the difficulties in +believing that all the individuals of the same species, wherever +located, have descended from the same parents, are not insuperable. And +we are led to this conclusion, which has been arrived at by many +naturalists under the designation of single centres of creation, by some +general considerations, more especially from the importance of barriers +and from the analogical distribution of sub-genera, genera, and +families. + +With respect to the distinct species of the same genus, which on my +theory must have spread from one parent-source; if we make the same +allowances as before for our ignorance, and remember that some forms of +life change most slowly, enormous periods of time being thus granted for +their migration, I do not think that the difficulties are insuperable; +though they often are in this case, and in that of the individuals of +the same species, extremely grave. As exemplifying the effects of climatal changes on distribution, I have -attempted to show how important has been the influence of the modern Glacial -period, which I am fully convinced simultaneously affected the whole world, or -at least great meridional belts. As showing how diversified are the means of -occasional transport, I have discussed at some little length the means of -dispersal of fresh-water productions. - -If the difficulties be not insuperable in admitting that in the long course of -time the individuals of the same species, and likewise of allied species, have -proceeded from some one source; then I think all the grand leading facts of -geographical distribution are explicable on the theory of migration (generally -of the more dominant forms of life), together with subsequent modification and -the multiplication of new forms. We can thus understand the high importance of -barriers, whether of land or water, which separate our several zoological and -botanical provinces. We can thus understand the localisation of sub-genera, +attempted to show how important has been the influence of the modern +Glacial period, which I am fully convinced simultaneously affected the +whole world, or at least great meridional belts. As showing how +diversified are the means of occasional transport, I have discussed at +some little length the means of dispersal of fresh-water productions. + +If the difficulties be not insuperable in admitting that in the long +course of time the individuals of the same species, and likewise of +allied species, have proceeded from some one source; then I think all +the grand leading facts of geographical distribution are explicable on +the theory of migration (generally of the more dominant forms of life), +together with subsequent modification and the multiplication of new +forms. We can thus understand the high importance of barriers, whether +of land or water, which separate our several zoological and botanical +provinces. We can thus understand the localisation of sub-genera, genera, and families; and how it is that under different latitudes, for -instance in South America, the inhabitants of the plains and mountains, of the -forests, marshes, and deserts, are in so mysterious a manner linked together by -affinity, and are likewise linked to the extinct beings which formerly -inhabited the same continent. Bearing in mind that the mutual relations of -organism to organism are of the highest importance, we can see why two areas -having nearly the same physical conditions should often be inhabited by very -different forms of life; for according to the length of time which has elapsed -since new inhabitants entered one region; according to the nature of the -communication which allowed certain forms and not others to enter, either in -greater or lesser numbers; according or not, as those which entered happened to -come in more or less direct competition with each other and with the -aborigines; and according as the immigrants were capable of varying more or -less rapidly, there would ensue in different regions, independently of their -physical conditions, infinitely diversified conditions of life,—there would be -an almost endless amount of organic action and reaction,—and we should find, as -we do find, some groups of beings greatly, and some only slightly -modified,—some developed in great force, some existing in scanty numbers—in the +instance in South America, the inhabitants of the plains and mountains, +of the forests, marshes, and deserts, are in so mysterious a manner +linked together by affinity, and are likewise linked to the extinct +beings which formerly inhabited the same continent. Bearing in mind that +the mutual relations of organism to organism are of the highest +importance, we can see why two areas having nearly the same physical +conditions should often be inhabited by very different forms of life; +for according to the length of time which has elapsed since new +inhabitants entered one region; according to the nature of the +communication which allowed certain forms and not others to enter, +either in greater or lesser numbers; according or not, as those which +entered happened to come in more or less direct competition with each +other and with the aborigines; and according as the immigrants were +capable of varying more or less rapidly, there would ensue in different +regions, independently of their physical conditions, infinitely +diversified conditions of life,—there would be an almost endless amount +of organic action and reaction,—and we should find, as we do find, some +groups of beings greatly, and some only slightly modified,—some +developed in great force, some existing in scanty numbers—in the different great geographical provinces of the world. -On these same principles, we can understand, as I have endeavoured to show, why -oceanic islands should have few inhabitants, but of these a great number should -be endemic or peculiar; and why, in relation to the means of migration, one -group of beings, even within the same class, should have all its species -endemic, and another group should have all its species common to other quarters -of the world. We can see why whole groups of organisms, as batrachians and -terrestrial mammals, should be absent from oceanic islands, whilst the most -isolated islands possess their own peculiar species of ærial mammals or bats. -We can see why there should be some relation between the presence of mammals, -in a more or less modified condition, and the depth of the sea between an -island and the mainland. We can clearly see why all the inhabitants of an -archipelago, though specifically distinct on the several islets, should be -closely related to each other, and likewise be related, but less closely, to -those of the nearest continent or other source whence immigrants were probably -derived. We can see why in two areas, however distant from each other, there -should be a correlation, in the presence of identical species, of varieties, of -doubtful species, and of distinct but representative species. - -As the late Edward Forbes often insisted, there is a striking parallelism in -the laws of life throughout time and space: the laws governing the succession -of forms in past times being nearly the same with those governing at the -present time the differences in different areas. We see this in many facts. The -endurance of each species and group of species is continuous in time; for the -exceptions to the rule are so few, that they may fairly be attributed to our -not having as yet discovered in an intermediate deposit the forms which are -therein absent, but which occur above and below: so in space, it certainly is -the general rule that the area inhabited by a single species, or by a group of -species, is continuous; and the exceptions, which are not rare, may, as I have -attempted to show, be accounted for by migration at some former period under -different conditions or by occasional means of transport, and by the species -having become extinct in the intermediate tracts. Both in time and space, -species and groups of species have their points of maximum development. Groups -of species, belonging either to a certain period of time, or to a certain area, -are often characterised by trifling characters in common, as of sculpture or -colour. In looking to the long succession of ages, as in now looking to distant -provinces throughout the world, we find that some organisms differ little, -whilst others belonging to a different class, or to a different order, or even -only to a different family of the same order, differ greatly. In both time and -space the lower members of each class generally change less than the higher; -but there are in both cases marked exceptions to the rule. On my theory these -several relations throughout time and space are intelligible; for whether we -look to the forms of life which have changed during successive ages within the -same quarter of the world, or to those which have changed after having migrated -into distant quarters, in both cases the forms within each class have been -connected by the same bond of ordinary generation; and the more nearly any two -forms are related in blood, the nearer they will generally stand to each other -in time and space; in both cases the laws of variation have been the same, and -modifications have been accumulated by the same power of natural selection. - -CHAPTER XIII. -MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY: EMBRYOLOGY: RUDIMENTARY -ORGANS. +On these same principles, we can understand, as I have endeavoured to +show, why oceanic islands should have few inhabitants, but of these a +great number should be endemic or peculiar; and why, in relation to the +means of migration, one group of beings, even within the same class, +should have all its species endemic, and another group should have all +its species common to other quarters of the world. We can see why whole +groups of organisms, as batrachians and terrestrial mammals, should be +absent from oceanic islands, whilst the most isolated islands possess +their own peculiar species of ærial mammals or bats. We can see why +there should be some relation between the presence of mammals, in a more +or less modified condition, and the depth of the sea between an island +and the mainland. We can clearly see why all the inhabitants of an +archipelago, though specifically distinct on the several islets, should +be closely related to each other, and likewise be related, but less +closely, to those of the nearest continent or other source whence +immigrants were probably derived. We can see why in two areas, however +distant from each other, there should be a correlation, in the presence +of identical species, of varieties, of doubtful species, and of distinct +but representative species. + +As the late Edward Forbes often insisted, there is a striking +parallelism in the laws of life throughout time and space: the laws +governing the succession of forms in past times being nearly the same +with those governing at the present time the differences in different +areas. We see this in many facts. The endurance of each species and +group of species is continuous in time; for the exceptions to the rule +are so few, that they may fairly be attributed to our not having as yet +discovered in an intermediate deposit the forms which are therein +absent, but which occur above and below: so in space, it certainly is +the general rule that the area inhabited by a single species, or by a +group of species, is continuous; and the exceptions, which are not rare, +may, as I have attempted to show, be accounted for by migration at some +former period under different conditions or by occasional means of +transport, and by the species having become extinct in the intermediate +tracts. Both in time and space, species and groups of species have their +points of maximum development. Groups of species, belonging either to a +certain period of time, or to a certain area, are often characterised by +trifling characters in common, as of sculpture or colour. In looking to +the long succession of ages, as in now looking to distant provinces +throughout the world, we find that some organisms differ little, whilst +others belonging to a different class, or to a different order, or even +only to a different family of the same order, differ greatly. In both +time and space the lower members of each class generally change less +than the higher; but there are in both cases marked exceptions to the +rule. On my theory these several relations throughout time and space are +intelligible; for whether we look to the forms of life which have +changed during successive ages within the same quarter of the world, or +to those which have changed after having migrated into distant quarters, +in both cases the forms within each class have been connected by the +same bond of ordinary generation; and the more nearly any two forms are +related in blood, the nearer they will generally stand to each other in +time and space; in both cases the laws of variation have been the same, +and modifications have been accumulated by the same power of natural +selection. + +CHAPTER XIII. MUTUAL AFFINITIES OF ORGANIC BEINGS: MORPHOLOGY: +EMBRYOLOGY: RUDIMENTARY ORGANS. CLASSIFICATION, groups subordinate to groups. Natural system. Rules and difficulties in classification, explained on the theory of descent with modification. Classification of varieties. Descent always used in -classification. Analogical or adaptive characters. Affinities, general, complex -and radiating. Extinction separates and defines groups. MORPHOLOGY, between -members of the same class, between parts of the same individual. EMBRYOLOGY, -laws of, explained by variations not supervening at an early age, and being -inherited at a corresponding age. RUDIMENTARY ORGANS; their origin explained. -Summary. - -From the first dawn of life, all organic beings are found to resemble each -other in descending degrees, so that they can be classed in groups under -groups. This classification is evidently not arbitrary like the grouping of the -stars in constellations. The existence of groups would have been of simple -signification, if one group had been exclusively fitted to inhabit the land, -and another the water; one to feed on flesh, another on vegetable matter, and -so on; but the case is widely different in nature; for it is notorious how -commonly members of even the same subgroup have different habits. In our second -and fourth chapters, on Variation and on Natural Selection, I have attempted to -show that it is the widely ranging, the much diffused and common, that is the -dominant species belonging to the larger genera, which vary most. The -varieties, or incipient species, thus produced ultimately become converted, as -I believe, into new and distinct species; and these, on the principle of -inheritance, tend to produce other new and dominant species. Consequently the -groups which are now large, and which generally include many dominant species, -tend to go on increasing indefinitely in size. I further attempted to show that -from the varying descendants of each species trying to occupy as many and as -different places as possible in the economy of nature, there is a constant -tendency in their characters to diverge. This conclusion was supported by -looking at the great diversity of the forms of life which, in any small area, -come into the closest competition, and by looking to certain facts in -naturalisation. - -I attempted also to show that there is a constant tendency in the forms which -are increasing in number and diverging in character, to supplant and -exterminate the less divergent, the less improved, and preceding forms. I -request the reader to turn to the diagram illustrating the action, as formerly -explained, of these several principles; and he will see that the inevitable -result is that the modified descendants proceeding from one progenitor become -broken up into groups subordinate to groups. In the diagram each letter on the -uppermost line may represent a genus including several species; and all the -genera on this line form together one class, for all have descended from one -ancient but unseen parent, and, consequently, have inherited something in -common. But the three genera on the left hand have, on this same principle, -much in common, and form a sub-family, distinct from that including the next -two genera on the right hand, which diverged from a common parent at the fifth -stage of descent. These five genera have also much, though less, in common; and -they form a family distinct from that including the three genera still further -to the right hand, which diverged at a still earlier period. And all these -genera, descended from (A), form an order distinct from the genera descended -from (I). So that we here have many species descended from a single progenitor -grouped into genera; and the genera are included in, or subordinate to, -sub-families, families, and orders, all united into one class. Thus, the grand -fact in natural history of the subordination of group under group, which, from -its familiarity, does not always sufficiently strike us, is in my judgment -fully explained. - -Naturalists try to arrange the species, genera, and families in each class, on -what is called the Natural System. But what is meant by this system? Some -authors look at it merely as a scheme for arranging together those living -objects which are most alike, and for separating those which are most unlike; -or as an artificial means for enunciating, as briefly as possible, general -propositions,—that is, by one sentence to give the characters common, for -instance, to all mammals, by another those common to all carnivora, by another -those common to the dog-genus, and then by adding a single sentence, a full -description is given of each kind of dog. The ingenuity and utility of this -system are indisputable. But many naturalists think that something more is -meant by the Natural System; they believe that it reveals the plan of the -Creator; but unless it be specified whether order in time or space, or what -else is meant by the plan of the Creator, it seems to me that nothing is thus -added to our knowledge. Such expressions as that famous one of Linnæus, and -which we often meet with in a more or less concealed form, that the characters -do not make the genus, but that the genus gives the characters, seem to imply -that something more is included in our classification, than mere resemblance. I -believe that something more is included; and that propinquity of descent,—the -only known cause of the similarity of organic beings,—is the bond, hidden as it -is by various degrees of modification, which is partially revealed to us by our -classifications. - -Let us now consider the rules followed in classification, and the difficulties -which are encountered on the view that classification either gives some unknown -plan of creation, or is simply a scheme for enunciating general propositions -and of placing together the forms most like each other. It might have been -thought (and was in ancient times thought) that those parts of the structure -which determined the habits of life, and the general place of each being in the -economy of nature, would be of very high importance in classification. Nothing -can be more false. No one regards the external similarity of a mouse to a -shrew, of a dugong to a whale, of a whale to a fish, as of any importance. -These resemblances, though so intimately connected with the whole life of the -being, are ranked as merely “adaptive or analogical characters;” but to the -consideration of these resemblances we shall have to recur. It may even be -given as a general rule, that the less any part of the organisation is -concerned with special habits, the more important it becomes for -classification. As an instance: Owen, in speaking of the dugong, says, “The -generative organs being those which are most remotely related to the habits and -food of an animal, I have always regarded as affording very clear indications -of its true affinities. We are least likely in the modifications of these -organs to mistake a merely adaptive for an essential character.” So with -plants, how remarkable it is that the organs of vegetation, on which their -whole life depends, are of little signification, excepting in the first main -divisions; whereas the organs of reproduction, with their product the seed, are -of paramount importance! - -We must not, therefore, in classifying, trust to resemblances in parts of the -organisation, however important they may be for the welfare of the being in -relation to the outer world. Perhaps from this cause it has partly arisen, that -almost all naturalists lay the greatest stress on resemblances in organs of -high vital or physiological importance. No doubt this view of the -classificatory importance of organs which are important is generally, but by no -means always, true. But their importance for classification, I believe, depends -on their greater constancy throughout large groups of species; and this -constancy depends on such organs having generally been subjected to less change -in the adaptation of the species to their conditions of life. That the mere -physiological importance of an organ does not determine its classificatory -value, is almost shown by the one fact, that in allied groups, in which the -same organ, as we have every reason to suppose, has nearly the same -physiological value, its classificatory value is widely different. No -naturalist can have worked at any group without being struck with this fact; -and it has been most fully acknowledged in the writings of almost every author. -It will suffice to quote the highest authority, Robert Brown, who in speaking -of certain organs in the Proteaceæ, says their generic importance, “like that -of all their parts, not only in this but, as I apprehend, in every natural -family, is very unequal, and in some cases seems to be entirely lost.” Again in -another work he says, the genera of the Connaraceæ “differ in having one or -more ovaria, in the existence or absence of albumen, in the imbricate or -valvular æstivation. Any one of these characters singly is frequently of more -than generic importance, though here even when all taken together they appear -insufficient to separate Cnestis from Connarus.” To give an example amongst -insects, in one great division of the Hymenoptera, the antennæ, as Westwood has -remarked, are most constant in structure; in another division they differ much, -and the differences are of quite subordinate value in classification; yet no -one probably will say that the antennæ in these two divisions of the same order -are of unequal physiological importance. Any number of instances could be given -of the varying importance for classification of the same important organ within +classification. Analogical or adaptive characters. Affinities, general, +complex and radiating. Extinction separates and defines groups. +MORPHOLOGY, between members of the same class, between parts of the same +individual. EMBRYOLOGY, laws of, explained by variations not supervening +at an early age, and being inherited at a corresponding age. RUDIMENTARY +ORGANS; their origin explained. Summary. + +From the first dawn of life, all organic beings are found to resemble +each other in descending degrees, so that they can be classed in groups +under groups. This classification is evidently not arbitrary like the +grouping of the stars in constellations. The existence of groups would +have been of simple signification, if one group had been exclusively +fitted to inhabit the land, and another the water; one to feed on flesh, +another on vegetable matter, and so on; but the case is widely different +in nature; for it is notorious how commonly members of even the same +subgroup have different habits. In our second and fourth chapters, on +Variation and on Natural Selection, I have attempted to show that it is +the widely ranging, the much diffused and common, that is the dominant +species belonging to the larger genera, which vary most. The varieties, +or incipient species, thus produced ultimately become converted, as I +believe, into new and distinct species; and these, on the principle of +inheritance, tend to produce other new and dominant species. +Consequently the groups which are now large, and which generally include +many dominant species, tend to go on increasing indefinitely in size. I +further attempted to show that from the varying descendants of each +species trying to occupy as many and as different places as possible in +the economy of nature, there is a constant tendency in their characters +to diverge. This conclusion was supported by looking at the great +diversity of the forms of life which, in any small area, come into the +closest competition, and by looking to certain facts in naturalisation. + +I attempted also to show that there is a constant tendency in the forms +which are increasing in number and diverging in character, to supplant +and exterminate the less divergent, the less improved, and preceding +forms. I request the reader to turn to the diagram illustrating the +action, as formerly explained, of these several principles; and he will +see that the inevitable result is that the modified descendants +proceeding from one progenitor become broken up into groups subordinate +to groups. In the diagram each letter on the uppermost line may +represent a genus including several species; and all the genera on this +line form together one class, for all have descended from one ancient +but unseen parent, and, consequently, have inherited something in +common. But the three genera on the left hand have, on this same +principle, much in common, and form a sub-family, distinct from that +including the next two genera on the right hand, which diverged from a +common parent at the fifth stage of descent. These five genera have also +much, though less, in common; and they form a family distinct from that +including the three genera still further to the right hand, which +diverged at a still earlier period. And all these genera, descended from +(A), form an order distinct from the genera descended from (I). So that +we here have many species descended from a single progenitor grouped +into genera; and the genera are included in, or subordinate to, +sub-families, families, and orders, all united into one class. Thus, the +grand fact in natural history of the subordination of group under group, +which, from its familiarity, does not always sufficiently strike us, is +in my judgment fully explained. + +Naturalists try to arrange the species, genera, and families in each +class, on what is called the Natural System. But what is meant by this +system? Some authors look at it merely as a scheme for arranging +together those living objects which are most alike, and for separating +those which are most unlike; or as an artificial means for enunciating, +as briefly as possible, general propositions,—that is, by one sentence +to give the characters common, for instance, to all mammals, by another +those common to all carnivora, by another those common to the dog-genus, +and then by adding a single sentence, a full description is given of +each kind of dog. The ingenuity and utility of this system are +indisputable. But many naturalists think that something more is meant by +the Natural System; they believe that it reveals the plan of the +Creator; but unless it be specified whether order in time or space, or +what else is meant by the plan of the Creator, it seems to me that +nothing is thus added to our knowledge. Such expressions as that famous +one of Linnæus, and which we often meet with in a more or less concealed +form, that the characters do not make the genus, but that the genus +gives the characters, seem to imply that something more is included in +our classification, than mere resemblance. I believe that something more +is included; and that propinquity of descent,—the only known cause of +the similarity of organic beings,—is the bond, hidden as it is by +various degrees of modification, which is partially revealed to us by +our classifications. + +Let us now consider the rules followed in classification, and the +difficulties which are encountered on the view that classification +either gives some unknown plan of creation, or is simply a scheme for +enunciating general propositions and of placing together the forms most +like each other. It might have been thought (and was in ancient times +thought) that those parts of the structure which determined the habits +of life, and the general place of each being in the economy of nature, +would be of very high importance in classification. Nothing can be more +false. No one regards the external similarity of a mouse to a shrew, of +a dugong to a whale, of a whale to a fish, as of any importance. These +resemblances, though so intimately connected with the whole life of the +being, are ranked as merely “adaptive or analogical characters;” but to +the consideration of these resemblances we shall have to recur. It may +even be given as a general rule, that the less any part of the +organisation is concerned with special habits, the more important it +becomes for classification. As an instance: Owen, in speaking of the +dugong, says, “The generative organs being those which are most remotely +related to the habits and food of an animal, I have always regarded as +affording very clear indications of its true affinities. We are least +likely in the modifications of these organs to mistake a merely adaptive +for an essential character.” So with plants, how remarkable it is that +the organs of vegetation, on which their whole life depends, are of +little signification, excepting in the first main divisions; whereas the +organs of reproduction, with their product the seed, are of paramount +importance! + +We must not, therefore, in classifying, trust to resemblances in parts +of the organisation, however important they may be for the welfare of +the being in relation to the outer world. Perhaps from this cause it has +partly arisen, that almost all naturalists lay the greatest stress on +resemblances in organs of high vital or physiological importance. No +doubt this view of the classificatory importance of organs which are +important is generally, but by no means always, true. But their +importance for classification, I believe, depends on their greater +constancy throughout large groups of species; and this constancy depends +on such organs having generally been subjected to less change in the +adaptation of the species to their conditions of life. That the mere +physiological importance of an organ does not determine its +classificatory value, is almost shown by the one fact, that in allied +groups, in which the same organ, as we have every reason to suppose, has +nearly the same physiological value, its classificatory value is widely +different. No naturalist can have worked at any group without being +struck with this fact; and it has been most fully acknowledged in the +writings of almost every author. It will suffice to quote the highest +authority, Robert Brown, who in speaking of certain organs in the +Proteaceæ, says their generic importance, “like that of all their parts, +not only in this but, as I apprehend, in every natural family, is very +unequal, and in some cases seems to be entirely lost.” Again in another +work he says, the genera of the Connaraceæ “differ in having one or more +ovaria, in the existence or absence of albumen, in the imbricate or +valvular æstivation. Any one of these characters singly is frequently of +more than generic importance, though here even when all taken together +they appear insufficient to separate Cnestis from Connarus.” To give an +example amongst insects, in one great division of the Hymenoptera, the +antennæ, as Westwood has remarked, are most constant in structure; in +another division they differ much, and the differences are of quite +subordinate value in classification; yet no one probably will say that +the antennæ in these two divisions of the same order are of unequal +physiological importance. Any number of instances could be given of the +varying importance for classification of the same important organ within the same group of beings. Again, no one will say that rudimentary or atrophied organs are of high -physiological or vital importance; yet, undoubtedly, organs in this condition -are often of high value in classification. No one will dispute that the -rudimentary teeth in the upper jaws of young ruminants, and certain rudimentary -bones of the leg, are highly serviceable in exhibiting the close affinity -between Ruminants and Pachyderms. Robert Brown has strongly insisted on the -fact that the rudimentary florets are of the highest importance in the -classification of the Grasses. - -Numerous instances could be given of characters derived from parts which must -be considered of very trifling physiological importance, but which are -universally admitted as highly serviceable in the definition of whole groups. -For instance, whether or not there is an open passage from the nostrils to the -mouth, the only character, according to Owen, which absolutely distinguishes -fishes and reptiles—the inflection of the angle of the jaws in Marsupials—the -manner in which the wings of insects are folded—mere colour in certain -Algæ—mere pubescence on parts of the flower in grasses—the nature of the dermal -covering, as hair or feathers, in the Vertebrata. If the Ornithorhynchus had -been covered with feathers instead of hair, this external and trifling -character would, I think, have been considered by naturalists as important an -aid in determining the degree of affinity of this strange creature to birds and -reptiles, as an approach in structure in any one internal and important organ. - -The importance, for classification, of trifling characters, mainly depends on -their being correlated with several other characters of more or less -importance. The value indeed of an aggregate of characters is very evident in -natural history. Hence, as has often been remarked, a species may depart from -its allies in several characters, both of high physiological importance and of -almost universal prevalence, and yet leave us in no doubt where it should be -ranked. Hence, also, it has been found, that a classification founded on any -single character, however important that may be, has always failed; for no part -of the organisation is universally constant. The importance of an aggregate of -characters, even when none are important, alone explains, I think, that saying -of Linnæus, that the characters do not give the genus, but the genus gives the -characters; for this saying seems founded on an appreciation of many trifling -points of resemblance, too slight to be defined. Certain plants, belonging to -the Malpighiaceæ, bear perfect and degraded flowers; in the latter, as A. de -Jussieu has remarked, “the greater number of the characters proper to the -species, to the genus, to the family, to the class, disappear, and thus laugh -at our classification.” But when Aspicarpa produced in France, during several -years, only degraded flowers, departing so wonderfully in a number of the most -important points of structure from the proper type of the order, yet M. Richard -sagaciously saw, as Jussieu observes, that this genus should still be retained -amongst the Malpighiaceæ. This case seems to me well to illustrate the spirit -with which our classifications are sometimes necessarily founded. - -Practically when naturalists are at work, they do not trouble themselves about -the physiological value of the characters which they use in defining a group, -or in allocating any particular species. If they find a character nearly -uniform, and common to a great number of forms, and not common to others, they -use it as one of high value; if common to some lesser number, they use it as of -subordinate value. This principle has been broadly confessed by some -naturalists to be the true one; and by none more clearly than by that excellent -botanist, Aug. St. Hilaire. If certain characters are always found correlated -with others, though no apparent bond of connexion can be discovered between -them, especial value is set on them. As in most groups of animals, important -organs, such as those for propelling the blood, or for ærating it, or those for -propagating the race, are found nearly uniform, they are considered as highly -serviceable in classification; but in some groups of animals all these, the -most important vital organs, are found to offer characters of quite subordinate -value. - -We can see why characters derived from the embryo should be of equal importance -with those derived from the adult, for our classifications of course include -all ages of each species. But it is by no means obvious, on the ordinary view, -why the structure of the embryo should be more important for this purpose than -that of the adult, which alone plays its full part in the economy of nature. -Yet it has been strongly urged by those great naturalists, Milne Edwards and -Agassiz, that embryonic characters are the most important of any in the -classification of animals; and this doctrine has very generally been admitted -as true. The same fact holds good with flowering plants, of which the two main -divisions have been founded on characters derived from the embryo,—on the -number and position of the embryonic leaves or cotyledons, and on the mode of -development of the plumule and radicle. In our discussion on embryology, we -shall see why such characters are so valuable, on the view of classification -tacitly including the idea of descent. - -Our classifications are often plainly influenced by chains of affinities. -Nothing can be easier than to define a number of characters common to all -birds; but in the case of crustaceans, such definition has hitherto been found -impossible. There are crustaceans at the opposite ends of the series, which -have hardly a character in common; yet the species at both ends, from being -plainly allied to others, and these to others, and so onwards, can be -recognised as unequivocally belonging to this, and to no other class of the -Articulata. +physiological or vital importance; yet, undoubtedly, organs in this +condition are often of high value in classification. No one will dispute +that the rudimentary teeth in the upper jaws of young ruminants, and +certain rudimentary bones of the leg, are highly serviceable in +exhibiting the close affinity between Ruminants and Pachyderms. Robert +Brown has strongly insisted on the fact that the rudimentary florets are +of the highest importance in the classification of the Grasses. + +Numerous instances could be given of characters derived from parts which +must be considered of very trifling physiological importance, but which +are universally admitted as highly serviceable in the definition of +whole groups. For instance, whether or not there is an open passage +from the nostrils to the mouth, the only character, according to Owen, +which absolutely distinguishes fishes and reptiles—the inflection of the +angle of the jaws in Marsupials—the manner in which the wings of insects +are folded—mere colour in certain Algæ—mere pubescence on parts of the +flower in grasses—the nature of the dermal covering, as hair or +feathers, in the Vertebrata. If the Ornithorhynchus had been covered +with feathers instead of hair, this external and trifling character +would, I think, have been considered by naturalists as important an aid +in determining the degree of affinity of this strange creature to birds +and reptiles, as an approach in structure in any one internal and +important organ. + +The importance, for classification, of trifling characters, mainly +depends on their being correlated with several other characters of more +or less importance. The value indeed of an aggregate of characters is +very evident in natural history. Hence, as has often been remarked, a +species may depart from its allies in several characters, both of high +physiological importance and of almost universal prevalence, and yet +leave us in no doubt where it should be ranked. Hence, also, it has been +found, that a classification founded on any single character, however +important that may be, has always failed; for no part of the +organisation is universally constant. The importance of an aggregate of +characters, even when none are important, alone explains, I think, that +saying of Linnæus, that the characters do not give the genus, but the +genus gives the characters; for this saying seems founded on an +appreciation of many trifling points of resemblance, too slight to be +defined. Certain plants, belonging to the Malpighiaceæ, bear perfect and +degraded flowers; in the latter, as A. de Jussieu has remarked, “the +greater number of the characters proper to the species, to the genus, to +the family, to the class, disappear, and thus laugh at our +classification.” But when Aspicarpa produced in France, during several +years, only degraded flowers, departing so wonderfully in a number of +the most important points of structure from the proper type of the +order, yet M. Richard sagaciously saw, as Jussieu observes, that this +genus should still be retained amongst the Malpighiaceæ. This case seems +to me well to illustrate the spirit with which our classifications are +sometimes necessarily founded. + +Practically when naturalists are at work, they do not trouble themselves +about the physiological value of the characters which they use in +defining a group, or in allocating any particular species. If they find +a character nearly uniform, and common to a great number of forms, and +not common to others, they use it as one of high value; if common to +some lesser number, they use it as of subordinate value. This principle +has been broadly confessed by some naturalists to be the true one; and +by none more clearly than by that excellent botanist, Aug. St. Hilaire. +If certain characters are always found correlated with others, though no +apparent bond of connexion can be discovered between them, especial +value is set on them. As in most groups of animals, important organs, +such as those for propelling the blood, or for ærating it, or those for +propagating the race, are found nearly uniform, they are considered as +highly serviceable in classification; but in some groups of animals all +these, the most important vital organs, are found to offer characters of +quite subordinate value. + +We can see why characters derived from the embryo should be of equal +importance with those derived from the adult, for our classifications of +course include all ages of each species. But it is by no means obvious, +on the ordinary view, why the structure of the embryo should be more +important for this purpose than that of the adult, which alone plays its +full part in the economy of nature. Yet it has been strongly urged by +those great naturalists, Milne Edwards and Agassiz, that embryonic +characters are the most important of any in the classification of +animals; and this doctrine has very generally been admitted as true. The +same fact holds good with flowering plants, of which the two main +divisions have been founded on characters derived from the embryo,—on +the number and position of the embryonic leaves or cotyledons, and on +the mode of development of the plumule and radicle. In our discussion on +embryology, we shall see why such characters are so valuable, on the +view of classification tacitly including the idea of descent. + +Our classifications are often plainly influenced by chains of +affinities. Nothing can be easier than to define a number of characters +common to all birds; but in the case of crustaceans, such definition has +hitherto been found impossible. There are crustaceans at the opposite +ends of the series, which have hardly a character in common; yet the +species at both ends, from being plainly allied to others, and these to +others, and so onwards, can be recognised as unequivocally belonging to +this, and to no other class of the Articulata. Geographical distribution has often been used, though perhaps not quite -logically, in classification, more especially in very large groups of closely -allied forms. Temminck insists on the utility or even necessity of this -practice in certain groups of birds; and it has been followed by several -entomologists and botanists. +logically, in classification, more especially in very large groups of +closely allied forms. Temminck insists on the utility or even necessity +of this practice in certain groups of birds; and it has been followed by +several entomologists and botanists. Finally, with respect to the comparative value of the various groups of -species, such as orders, sub-orders, families, sub-families, and genera, they -seem to be, at least at present, almost arbitrary. Several of the best -botanists, such as Mr. Bentham and others, have strongly insisted on their -arbitrary value. Instances could be given amongst plants and insects, of a -group of forms, first ranked by practised naturalists as only a genus, and then -raised to the rank of a sub-family or family; and this has been done, not -because further research has detected important structural differences, at -first overlooked, but because numerous allied species, with slightly different -grades of difference, have been subsequently discovered. +species, such as orders, sub-orders, families, sub-families, and genera, +they seem to be, at least at present, almost arbitrary. Several of the +best botanists, such as Mr. Bentham and others, have strongly insisted +on their arbitrary value. Instances could be given amongst plants and +insects, of a group of forms, first ranked by practised naturalists as +only a genus, and then raised to the rank of a sub-family or family; and +this has been done, not because further research has detected important +structural differences, at first overlooked, but because numerous allied +species, with slightly different grades of difference, have been +subsequently discovered. All the foregoing rules and aids and difficulties in classification are -explained, if I do not greatly deceive myself, on the view that the natural -system is founded on descent with modification; that the characters which -naturalists consider as showing true affinity between any two or more species, -are those which have been inherited from a common parent, and, in so far, all -true classification is genealogical; that community of descent is the hidden -bond which naturalists have been unconsciously seeking, and not some unknown -plan of creation, or the enunciation of general propositions, and the mere -putting together and separating objects more or less alike. - -But I must explain my meaning more fully. I believe that the arrangement of the -groups within each class, in due subordination and relation to the other -groups, must be strictly genealogical in order to be natural; but that the -amount of difference in the several branches or groups, though allied in the -same degree in blood to their common progenitor, may differ greatly, being due -to the different degrees of modification which they have undergone; and this is -expressed by the forms being ranked under different genera, families, sections, -or orders. The reader will best understand what is meant, if he will take the -trouble of referring to the diagram in the fourth chapter. We will suppose the -letters A to L to represent allied genera, which lived during the Silurian -epoch, and these have descended from a species which existed at an unknown -anterior period. Species of three of these genera (A, F, and I) have -transmitted modified descendants to the present day, represented by the fifteen -genera (a^14 to z^14) on the uppermost horizontal line. Now all these modified -descendants from a single species, are represented as related in blood or -descent to the same degree; they may metaphorically be called cousins to the -same millionth degree; yet they differ widely and in different degrees from -each other. The forms descended from A, now broken up into two or three -families, constitute a distinct order from those descended from I, also broken -up into two families. Nor can the existing species, descended from A, be ranked -in the same genus with the parent A; or those from I, with the parent I. But -the existing genus F^14 may be supposed to have been but slightly modified; and -it will then rank with the parent-genus F; just as some few still living -organic beings belong to Silurian genera. So that the amount or value of the -differences between organic beings all related to each other in the same degree -in blood, has come to be widely different. Nevertheless their genealogical -arrangement remains strictly true, not only at the present time, but at each -successive period of descent. All the modified descendants from A will have -inherited something in common from their common parent, as will all the -descendants from I; so will it be with each subordinate branch of descendants, -at each successive period. If, however, we choose to suppose that any of the -descendants of A or of I have been so much modified as to have more or less -completely lost traces of their parentage, in this case, their places in a -natural classification will have been more or less completely lost,—as -sometimes seems to have occurred with existing organisms. All the descendants -of the genus F, along its whole line of descent, are supposed to have been but -little modified, and they yet form a single genus. But this genus, though much -isolated, will still occupy its proper intermediate position; for F originally -was intermediate in character between A and I, and the several genera descended -from these two genera will have inherited to a certain extent their characters. -This natural arrangement is shown, as far as is possible on paper, in the -diagram, but in much too simple a manner. If a branching diagram had not been -used, and only the names of the groups had been written in a linear series, it -would have been still less possible to have given a natural arrangement; and it -is notoriously not possible to represent in a series, on a flat surface, the -affinities which we discover in nature amongst the beings of the same group. -Thus, on the view which I hold, the natural system is genealogical in its -arrangement, like a pedigree; but the degrees of modification which the -different groups have undergone, have to be expressed by ranking them under -different so-called genera, sub-families, families, sections, orders, and -classes. - -It may be worth while to illustrate this view of classification, by taking the -case of languages. If we possessed a perfect pedigree of mankind, a -genealogical arrangement of the races of man would afford the best -classification of the various languages now spoken throughout the world; and if -all extinct languages, and all intermediate and slowly changing dialects, had -to be included, such an arrangement would, I think, be the only possible one. -Yet it might be that some very ancient language had altered little, and had -given rise to few new languages, whilst others (owing to the spreading and -subsequent isolation and states of civilisation of the several races, descended -from a common race) had altered much, and had given rise to many new languages -and dialects. The various degrees of difference in the languages from the same -stock, would have to be expressed by groups subordinate to groups; but the -proper or even only possible arrangement would still be genealogical; and this -would be strictly natural, as it would connect together all languages, extinct -and modern, by the closest affinities, and would give the filiation and origin -of each tongue. - -In confirmation of this view, let us glance at the classification of varieties, -which are believed or known to have descended from one species. These are -grouped under species, with sub-varieties under varieties; and with our -domestic productions, several other grades of difference are requisite, as we -have seen with pigeons. The origin of the existence of groups subordinate to -groups, is the same with varieties as with species, namely, closeness of -descent with various degrees of modification. Nearly the same rules are -followed in classifying varieties, as with species. Authors have insisted on -the necessity of classing varieties on a natural instead of an artificial -system; we are cautioned, for instance, not to class two varieties of the -pine-apple together, merely because their fruit, though the most important -part, happens to be nearly identical; no one puts the swedish and common -turnips together, though the esculent and thickened stems are so similar. -Whatever part is found to be most constant, is used in classing varieties: thus -the great agriculturist Marshall says the horns are very useful for this -purpose with cattle, because they are less variable than the shape or colour of -the body, etc.; whereas with sheep the horns are much less serviceable, because -less constant. In classing varieties, I apprehend if we had a real pedigree, a -genealogical classification would be universally preferred; and it has been -attempted by some authors. For we might feel sure, whether there had been more -or less modification, the principle of inheritance would keep the forms +explained, if I do not greatly deceive myself, on the view that the +natural system is founded on descent with modification; that the +characters which naturalists consider as showing true affinity between +any two or more species, are those which have been inherited from a +common parent, and, in so far, all true classification is genealogical; +that community of descent is the hidden bond which naturalists have been +unconsciously seeking, and not some unknown plan of creation, or the +enunciation of general propositions, and the mere putting together and +separating objects more or less alike. + +But I must explain my meaning more fully. I believe that the arrangement +of the groups within each class, in due subordination and relation to +the other groups, must be strictly genealogical in order to be natural; +but that the amount of difference in the several branches or groups, +though allied in the same degree in blood to their common progenitor, +may differ greatly, being due to the different degrees of modification +which they have undergone; and this is expressed by the forms being +ranked under different genera, families, sections, or orders. The reader +will best understand what is meant, if he will take the trouble of +referring to the diagram in the fourth chapter. We will suppose the +letters A to L to represent allied genera, which lived during the +Silurian epoch, and these have descended from a species which existed at +an unknown anterior period. Species of three of these genera (A, F, and +I) have transmitted modified descendants to the present day, represented +by the fifteen genera (a^14 to z^14) on the uppermost horizontal line. +Now all these modified descendants from a single species, are +represented as related in blood or descent to the same degree; they may +metaphorically be called cousins to the same millionth degree; yet they +differ widely and in different degrees from each other. The forms +descended from A, now broken up into two or three families, constitute a +distinct order from those descended from I, also broken up into two +families. Nor can the existing species, descended from A, be ranked in +the same genus with the parent A; or those from I, with the parent I. +But the existing genus F^14 may be supposed to have been but slightly +modified; and it will then rank with the parent-genus F; just as some +few still living organic beings belong to Silurian genera. So that the +amount or value of the differences between organic beings all related to +each other in the same degree in blood, has come to be widely different. +Nevertheless their genealogical arrangement remains strictly true, not +only at the present time, but at each successive period of descent. All +the modified descendants from A will have inherited something in common +from their common parent, as will all the descendants from I; so will it +be with each subordinate branch of descendants, at each successive +period. If, however, we choose to suppose that any of the descendants of +A or of I have been so much modified as to have more or less completely +lost traces of their parentage, in this case, their places in a natural +classification will have been more or less completely lost,—as sometimes +seems to have occurred with existing organisms. All the descendants of +the genus F, along its whole line of descent, are supposed to have been +but little modified, and they yet form a single genus. But this genus, +though much isolated, will still occupy its proper intermediate +position; for F originally was intermediate in character between A and +I, and the several genera descended from these two genera will have +inherited to a certain extent their characters. This natural +arrangement is shown, as far as is possible on paper, in the diagram, +but in much too simple a manner. If a branching diagram had not been +used, and only the names of the groups had been written in a linear +series, it would have been still less possible to have given a natural +arrangement; and it is notoriously not possible to represent in a +series, on a flat surface, the affinities which we discover in nature +amongst the beings of the same group. Thus, on the view which I hold, +the natural system is genealogical in its arrangement, like a pedigree; +but the degrees of modification which the different groups have +undergone, have to be expressed by ranking them under different +so-called genera, sub-families, families, sections, orders, and classes. + +It may be worth while to illustrate this view of classification, by +taking the case of languages. If we possessed a perfect pedigree of +mankind, a genealogical arrangement of the races of man would afford the +best classification of the various languages now spoken throughout the +world; and if all extinct languages, and all intermediate and slowly +changing dialects, had to be included, such an arrangement would, I +think, be the only possible one. Yet it might be that some very ancient +language had altered little, and had given rise to few new languages, +whilst others (owing to the spreading and subsequent isolation and +states of civilisation of the several races, descended from a common +race) had altered much, and had given rise to many new languages and +dialects. The various degrees of difference in the languages from the +same stock, would have to be expressed by groups subordinate to groups; +but the proper or even only possible arrangement would still be +genealogical; and this would be strictly natural, as it would connect +together all languages, extinct and modern, by the closest affinities, +and would give the filiation and origin of each tongue. + +In confirmation of this view, let us glance at the classification of +varieties, which are believed or known to have descended from one +species. These are grouped under species, with sub-varieties under +varieties; and with our domestic productions, several other grades of +difference are requisite, as we have seen with pigeons. The origin of +the existence of groups subordinate to groups, is the same with +varieties as with species, namely, closeness of descent with various +degrees of modification. Nearly the same rules are followed in +classifying varieties, as with species. Authors have insisted on the +necessity of classing varieties on a natural instead of an artificial +system; we are cautioned, for instance, not to class two varieties of +the pine-apple together, merely because their fruit, though the most +important part, happens to be nearly identical; no one puts the swedish +and common turnips together, though the esculent and thickened stems are +so similar. Whatever part is found to be most constant, is used in +classing varieties: thus the great agriculturist Marshall says the horns +are very useful for this purpose with cattle, because they are less +variable than the shape or colour of the body, etc.; whereas with sheep +the horns are much less serviceable, because less constant. In classing +varieties, I apprehend if we had a real pedigree, a genealogical +classification would be universally preferred; and it has been attempted +by some authors. For we might feel sure, whether there had been more or +less modification, the principle of inheritance would keep the forms together which were allied in the greatest number of points. In tumbler -pigeons, though some sub-varieties differ from the others in the important -character of having a longer beak, yet all are kept together from having the -common habit of tumbling; but the short-faced breed has nearly or quite lost -this habit; nevertheless, without any reasoning or thinking on the subject, -these tumblers are kept in the same group, because allied in blood and alike in -some other respects. If it could be proved that the Hottentot had descended -from the Negro, I think he would be classed under the Negro group, however much -he might differ in colour and other important characters from negroes. - -With species in a state of nature, every naturalist has in fact brought descent -into his classification; for he includes in his lowest grade, or that of a -species, the two sexes; and how enormously these sometimes differ in the most -important characters, is known to every naturalist: scarcely a single fact can -be predicated in common of the males and hermaphrodites of certain cirripedes, -when adult, and yet no one dreams of separating them. The naturalist includes -as one species the several larval stages of the same individual, however much -they may differ from each other and from the adult; as he likewise includes the -so-called alternate generations of Steenstrup, which can only in a technical -sense be considered as the same individual. He includes monsters; he includes +pigeons, though some sub-varieties differ from the others in the +important character of having a longer beak, yet all are kept together +from having the common habit of tumbling; but the short-faced breed has +nearly or quite lost this habit; nevertheless, without any reasoning or +thinking on the subject, these tumblers are kept in the same group, +because allied in blood and alike in some other respects. If it could be +proved that the Hottentot had descended from the Negro, I think he would +be classed under the Negro group, however much he might differ in colour +and other important characters from negroes. + +With species in a state of nature, every naturalist has in fact brought +descent into his classification; for he includes in his lowest grade, or +that of a species, the two sexes; and how enormously these sometimes +differ in the most important characters, is known to every naturalist: +scarcely a single fact can be predicated in common of the males and +hermaphrodites of certain cirripedes, when adult, and yet no one dreams +of separating them. The naturalist includes as one species the several +larval stages of the same individual, however much they may differ from +each other and from the adult; as he likewise includes the so-called +alternate generations of Steenstrup, which can only in a technical sense +be considered as the same individual. He includes monsters; he includes varieties, not solely because they closely resemble the parent-form, but because they are descended from it. He who believes that the cowslip is -descended from the primrose, or conversely, ranks them together as a single -species, and gives a single definition. As soon as three Orchidean forms -(Monochanthus, Myanthus, and Catasetum), which had previously been ranked as -three distinct genera, were known to be sometimes produced on the same spike, -they were immediately included as a single species. But it may be asked, what -ought we to do, if it could be proved that one species of kangaroo had been -produced, by a long course of modification, from a bear? Ought we to rank this -one species with bears, and what should we do with the other species? The -supposition is of course preposterous; and I might answer by the argumentum ad -hominem, and ask what should be done if a perfect kangaroo were seen to come -out of the womb of a bear? According to all analogy, it would be ranked with -bears; but then assuredly all the other species of the kangaroo family would -have to be classed under the bear genus. The whole case is preposterous; for -where there has been close descent in common, there will certainly be close -resemblance or affinity. - -As descent has universally been used in classing together the individuals of -the same species, though the males and females and larvæ are sometimes -extremely different; and as it has been used in classing varieties which have -undergone a certain, and sometimes a considerable amount of modification, may -not this same element of descent have been unconsciously used in grouping -species under genera, and genera under higher groups, though in these cases the -modification has been greater in degree, and has taken a longer time to -complete? I believe it has thus been unconsciously used; and only thus can I -understand the several rules and guides which have been followed by our best -systematists. We have no written pedigrees; we have to make out community of -descent by resemblances of any kind. Therefore we choose those characters -which, as far as we can judge, are the least likely to have been modified in -relation to the conditions of life to which each species has been recently -exposed. Rudimentary structures on this view are as good as, or even sometimes -better than, other parts of the organisation. We care not how trifling a -character may be—let it be the mere inflection of the angle of the jaw, the -manner in which an insect’s wing is folded, whether the skin be covered by hair -or feathers—if it prevail throughout many and different species, especially -those having very different habits of life, it assumes high value; for we can -account for its presence in so many forms with such different habits, only by -its inheritance from a common parent. We may err in this respect in regard to -single points of structure, but when several characters, let them be ever so -trifling, occur together throughout a large group of beings having different -habits, we may feel almost sure, on the theory of descent, that these -characters have been inherited from a common ancestor. And we know that such -correlated or aggregated characters have especial value in classification. - -We can understand why a species or a group of species may depart, in several of -its most important characteristics, from its allies, and yet be safely classed -with them. This may be safely done, and is often done, as long as a sufficient -number of characters, let them be ever so unimportant, betrays the hidden bond -of community of descent. Let two forms have not a single character in common, -yet if these extreme forms are connected together by a chain of intermediate -groups, we may at once infer their community of descent, and we put them all -into the same class. As we find organs of high physiological importance—those -which serve to preserve life under the most diverse conditions of existence—are -generally the most constant, we attach especial value to them; but if these -same organs, in another group or section of a group, are found to differ much, -we at once value them less in our classification. We shall hereafter, I think, -clearly see why embryological characters are of such high classificatory -importance. Geographical distribution may sometimes be brought usefully into -play in classing large and widely-distributed genera, because all the species -of the same genus, inhabiting any distinct and isolated region, have in all +descended from the primrose, or conversely, ranks them together as a +single species, and gives a single definition. As soon as three +Orchidean forms (Monochanthus, Myanthus, and Catasetum), which had +previously been ranked as three distinct genera, were known to be +sometimes produced on the same spike, they were immediately included as +a single species. But it may be asked, what ought we to do, if it could +be proved that one species of kangaroo had been produced, by a long +course of modification, from a bear? Ought we to rank this one species +with bears, and what should we do with the other species? The +supposition is of course preposterous; and I might answer by the +argumentum ad hominem, and ask what should be done if a perfect kangaroo +were seen to come out of the womb of a bear? According to all analogy, +it would be ranked with bears; but then assuredly all the other species +of the kangaroo family would have to be classed under the bear genus. +The whole case is preposterous; for where there has been close descent +in common, there will certainly be close resemblance or affinity. + +As descent has universally been used in classing together the +individuals of the same species, though the males and females and larvæ +are sometimes extremely different; and as it has been used in classing +varieties which have undergone a certain, and sometimes a considerable +amount of modification, may not this same element of descent have been +unconsciously used in grouping species under genera, and genera under +higher groups, though in these cases the modification has been greater +in degree, and has taken a longer time to complete? I believe it has +thus been unconsciously used; and only thus can I understand the several +rules and guides which have been followed by our best systematists. We +have no written pedigrees; we have to make out community of descent by +resemblances of any kind. Therefore we choose those characters which, as +far as we can judge, are the least likely to have been modified in +relation to the conditions of life to which each species has been +recently exposed. Rudimentary structures on this view are as good as, or +even sometimes better than, other parts of the organisation. We care not +how trifling a character may be—let it be the mere inflection of the +angle of the jaw, the manner in which an insect’s wing is folded, +whether the skin be covered by hair or feathers—if it prevail throughout +many and different species, especially those having very different +habits of life, it assumes high value; for we can account for its +presence in so many forms with such different habits, only by its +inheritance from a common parent. We may err in this respect in regard +to single points of structure, but when several characters, let them be +ever so trifling, occur together throughout a large group of beings +having different habits, we may feel almost sure, on the theory of +descent, that these characters have been inherited from a common +ancestor. And we know that such correlated or aggregated characters have +especial value in classification. + +We can understand why a species or a group of species may depart, in +several of its most important characteristics, from its allies, and yet +be safely classed with them. This may be safely done, and is often done, +as long as a sufficient number of characters, let them be ever so +unimportant, betrays the hidden bond of community of descent. Let two +forms have not a single character in common, yet if these extreme forms +are connected together by a chain of intermediate groups, we may at once +infer their community of descent, and we put them all into the same +class. As we find organs of high physiological importance—those which +serve to preserve life under the most diverse conditions of +existence—are generally the most constant, we attach especial value to +them; but if these same organs, in another group or section of a group, +are found to differ much, we at once value them less in our +classification. We shall hereafter, I think, clearly see why +embryological characters are of such high classificatory importance. +Geographical distribution may sometimes be brought usefully into play in +classing large and widely-distributed genera, because all the species of +the same genus, inhabiting any distinct and isolated region, have in all probability descended from the same parents. -We can understand, on these views, the very important distinction between real -affinities and analogical or adaptive resemblances. Lamarck first called -attention to this distinction, and he has been ably followed by Macleay and -others. The resemblance, in the shape of the body and in the fin-like anterior -limbs, between the dugong, which is a pachydermatous animal, and the whale, and -between both these mammals and fishes, is analogical. Amongst insects there are -innumerable instances: thus Linnæus, misled by external appearances, actually -classed an homopterous insect as a moth. We see something of the same kind even -in our domestic varieties, as in the thickened stems of the common and swedish -turnip. The resemblance of the greyhound and racehorse is hardly more fanciful -than the analogies which have been drawn by some authors between very distinct -animals. On my view of characters being of real importance for classification, -only in so far as they reveal descent, we can clearly understand why analogical -or adaptive character, although of the utmost importance to the welfare of the -being, are almost valueless to the systematist. For animals, belonging to two -most distinct lines of descent, may readily become adapted to similar -conditions, and thus assume a close external resemblance; but such resemblances -will not reveal—will rather tend to conceal their blood-relationship to their -proper lines of descent. We can also understand the apparent paradox, that the -very same characters are analogical when one class or order is compared with -another, but give true affinities when the members of the same class or order -are compared one with another: thus the shape of the body and fin-like limbs -are only analogical when whales are compared with fishes, being adaptations in -both classes for swimming through the water; but the shape of the body and -fin-like limbs serve as characters exhibiting true affinity between the several -members of the whale family; for these cetaceans agree in so many characters, -great and small, that we cannot doubt that they have inherited their general -shape of body and structure of limbs from a common ancestor. So it is with +We can understand, on these views, the very important distinction +between real affinities and analogical or adaptive resemblances. Lamarck +first called attention to this distinction, and he has been ably +followed by Macleay and others. The resemblance, in the shape of the +body and in the fin-like anterior limbs, between the dugong, which is a +pachydermatous animal, and the whale, and between both these mammals and +fishes, is analogical. Amongst insects there are innumerable instances: +thus Linnæus, misled by external appearances, actually classed an +homopterous insect as a moth. We see something of the same kind even in +our domestic varieties, as in the thickened stems of the common and +swedish turnip. The resemblance of the greyhound and racehorse is hardly +more fanciful than the analogies which have been drawn by some authors +between very distinct animals. On my view of characters being of real +importance for classification, only in so far as they reveal descent, we +can clearly understand why analogical or adaptive character, although of +the utmost importance to the welfare of the being, are almost valueless +to the systematist. For animals, belonging to two most distinct lines of +descent, may readily become adapted to similar conditions, and thus +assume a close external resemblance; but such resemblances will not +reveal—will rather tend to conceal their blood-relationship to their +proper lines of descent. We can also understand the apparent paradox, +that the very same characters are analogical when one class or order is +compared with another, but give true affinities when the members of the +same class or order are compared one with another: thus the shape of the +body and fin-like limbs are only analogical when whales are compared +with fishes, being adaptations in both classes for swimming through the +water; but the shape of the body and fin-like limbs serve as characters +exhibiting true affinity between the several members of the whale +family; for these cetaceans agree in so many characters, great and +small, that we cannot doubt that they have inherited their general shape +of body and structure of limbs from a common ancestor. So it is with fishes. -As members of distinct classes have often been adapted by successive slight -modifications to live under nearly similar circumstances,—to inhabit for -instance the three elements of land, air, and water,—we can perhaps understand -how it is that a numerical parallelism has sometimes been observed between the -sub-groups in distinct classes. A naturalist, struck by a parallelism of this -nature in any one class, by arbitrarily raising or sinking the value of the -groups in other classes (and all our experience shows that this valuation has -hitherto been arbitrary), could easily extend the parallelism over a wide -range; and thus the septenary, quinary, quaternary, and ternary classifications -have probably arisen. +As members of distinct classes have often been adapted by successive +slight modifications to live under nearly similar circumstances,—to +inhabit for instance the three elements of land, air, and water,—we can +perhaps understand how it is that a numerical parallelism has sometimes +been observed between the sub-groups in distinct classes. A naturalist, +struck by a parallelism of this nature in any one class, by arbitrarily +raising or sinking the value of the groups in other classes (and all our +experience shows that this valuation has hitherto been arbitrary), could +easily extend the parallelism over a wide range; and thus the septenary, +quinary, quaternary, and ternary classifications have probably arisen. As the modified descendants of dominant species, belonging to the larger -genera, tend to inherit the advantages, which made the groups to which they -belong large and their parents dominant, they are almost sure to spread widely, -and to seize on more and more places in the economy of nature. The larger and -more dominant groups thus tend to go on increasing in size; and they -consequently supplant many smaller and feebler groups. Thus we can account for -the fact that all organisms, recent and extinct, are included under a few great -orders, under still fewer classes, and all in one great natural system. As -showing how few the higher groups are in number, and how widely spread they are -throughout the world, the fact is striking, that the discovery of Australia has -not added a single insect belonging to a new order; and that in the vegetable -kingdom, as I learn from Dr. Hooker, it has added only two or three orders of -small size. - -In the chapter on geological succession I attempted to show, on the principle -of each group having generally diverged much in character during the -long-continued process of modification, how it is that the more ancient forms -of life often present characters in some slight degree intermediate between -existing groups. A few old and intermediate parent-forms having occasionally -transmitted to the present day descendants but little modified, will give to us -our so-called osculant or aberrant groups. The more aberrant any form is, the -greater must be the number of connecting forms which on my theory have been -exterminated and utterly lost. And we have some evidence of aberrant forms -having suffered severely from extinction, for they are generally represented by -extremely few species; and such species as do occur are generally very distinct -from each other, which again implies extinction. The genera Ornithorhynchus and -Lepidosiren, for example, would not have been less aberrant had each been -represented by a dozen species instead of by a single one; but such richness in -species, as I find after some investigation, does not commonly fall to the lot -of aberrant genera. We can, I think, account for this fact only by looking at -aberrant forms as failing groups conquered by more successful competitors, with -a few members preserved by some unusual coincidence of favourable +genera, tend to inherit the advantages, which made the groups to which +they belong large and their parents dominant, they are almost sure to +spread widely, and to seize on more and more places in the economy of +nature. The larger and more dominant groups thus tend to go on +increasing in size; and they consequently supplant many smaller and +feebler groups. Thus we can account for the fact that all organisms, +recent and extinct, are included under a few great orders, under still +fewer classes, and all in one great natural system. As showing how few +the higher groups are in number, and how widely spread they are +throughout the world, the fact is striking, that the discovery of +Australia has not added a single insect belonging to a new order; and +that in the vegetable kingdom, as I learn from Dr. Hooker, it has added +only two or three orders of small size. + +In the chapter on geological succession I attempted to show, on the +principle of each group having generally diverged much in character +during the long-continued process of modification, how it is that the +more ancient forms of life often present characters in some slight +degree intermediate between existing groups. A few old and intermediate +parent-forms having occasionally transmitted to the present day +descendants but little modified, will give to us our so-called osculant +or aberrant groups. The more aberrant any form is, the greater must be +the number of connecting forms which on my theory have been exterminated +and utterly lost. And we have some evidence of aberrant forms having +suffered severely from extinction, for they are generally represented by +extremely few species; and such species as do occur are generally very +distinct from each other, which again implies extinction. The genera +Ornithorhynchus and Lepidosiren, for example, would not have been less +aberrant had each been represented by a dozen species instead of by a +single one; but such richness in species, as I find after some +investigation, does not commonly fall to the lot of aberrant genera. We +can, I think, account for this fact only by looking at aberrant forms as +failing groups conquered by more successful competitors, with a few +members preserved by some unusual coincidence of favourable circumstances. -Mr. Waterhouse has remarked that, when a member belonging to one group of -animals exhibits an affinity to a quite distinct group, this affinity in most -cases is general and not special: thus, according to Mr. Waterhouse, of all -Rodents, the bizcacha is most nearly related to Marsupials; but in the points -in which it approaches this order, its relations are general, and not to any -one marsupial species more than to another. As the points of affinity of the -bizcacha to Marsupials are believed to be real and not merely adaptive, they -are due on my theory to inheritance in common. Therefore we must suppose either -that all Rodents, including the bizcacha, branched off from some very ancient -Marsupial, which will have had a character in some degree intermediate with -respect to all existing Marsupials; or that both Rodents and Marsupials -branched off from a common progenitor, and that both groups have since -undergone much modification in divergent directions. On either view we may -suppose that the bizcacha has retained, by inheritance, more of the character -of its ancient progenitor than have other Rodents; and therefore it will not be -specially related to any one existing Marsupial, but indirectly to all or -nearly all Marsupials, from having partially retained the character of their -common progenitor, or of an early member of the group. On the other hand, of -all Marsupials, as Mr. Waterhouse has remarked, the phascolomys resembles most -nearly, not any one species, but the general order of Rodents. In this case, -however, it may be strongly suspected that the resemblance is only analogical, -owing to the phascolomys having become adapted to habits like those of a -Rodent. The elder De Candolle has made nearly similar observations on the -general nature of the affinities of distinct orders of plants. - -On the principle of the multiplication and gradual divergence in character of -the species descended from a common parent, together with their retention by -inheritance of some characters in common, we can understand the excessively -complex and radiating affinities by which all the members of the same family or -higher group are connected together. For the common parent of a whole family of -species, now broken up by extinction into distinct groups and sub-groups, will -have transmitted some of its characters, modified in various ways and degrees, -to all; and the several species will consequently be related to each other by -circuitous lines of affinity of various lengths (as may be seen in the diagram -so often referred to), mounting up through many predecessors. As it is -difficult to show the blood-relationship between the numerous kindred of any -ancient and noble family, even by the aid of a genealogical tree, and almost -impossible to do this without this aid, we can understand the extraordinary -difficulty which naturalists have experienced in describing, without the aid of -a diagram, the various affinities which they perceive between the many living -and extinct members of the same great natural class. - -Extinction, as we have seen in the fourth chapter, has played an important part -in defining and widening the intervals between the several groups in each -class. We may thus account even for the distinctness of whole classes from each -other—for instance, of birds from all other vertebrate animals—by the belief -that many ancient forms of life have been utterly lost, through which the early -progenitors of birds were formerly connected with the early progenitors of the -other vertebrate classes. There has been less entire extinction of the forms of -life which once connected fishes with batrachians. There has been still less in -some other classes, as in that of the Crustacea, for here the most wonderfully -diverse forms are still tied together by a long, but broken, chain of -affinities. Extinction has only separated groups: it has by no means made them; -for if every form which has ever lived on this earth were suddenly to reappear, -though it would be quite impossible to give definitions by which each group -could be distinguished from other groups, as all would blend together by steps -as fine as those between the finest existing varieties, nevertheless a natural -classification, or at least a natural arrangement, would be possible. We shall -see this by turning to the diagram: the letters, A to L, may represent eleven -Silurian genera, some of which have produced large groups of modified -descendants. Every intermediate link between these eleven genera and their -primordial parent, and every intermediate link in each branch and sub-branch of -their descendants, may be supposed to be still alive; and the links to be as -fine as those between the finest varieties. In this case it would be quite -impossible to give any definition by which the several members of the several -groups could be distinguished from their more immediate parents; or these -parents from their ancient and unknown progenitor. Yet the natural arrangement -in the diagram would still hold good; and, on the principle of inheritance, all -the forms descended from A, or from I, would have something in common. In a -tree we can specify this or that branch, though at the actual fork the two -unite and blend together. We could not, as I have said, define the several -groups; but we could pick out types, or forms, representing most of the -characters of each group, whether large or small, and thus give a general idea -of the value of the differences between them. This is what we should be driven -to, if we were ever to succeed in collecting all the forms in any class which -have lived throughout all time and space. We shall certainly never succeed in -making so perfect a collection: nevertheless, in certain classes, we are -tending in this direction; and Milne Edwards has lately insisted, in an able -paper, on the high importance of looking to types, whether or not we can -separate and define the groups to which such types belong. - -Finally, we have seen that natural selection, which results from the struggle -for existence, and which almost inevitably induces extinction and divergence of -character in the many descendants from one dominant parent-species, explains -that great and universal feature in the affinities of all organic beings, -namely, their subordination in group under group. We use the element of descent -in classing the individuals of both sexes and of all ages, although having few -characters in common, under one species; we use descent in classing -acknowledged varieties, however different they may be from their parent; and I -believe this element of descent is the hidden bond of connexion which -naturalists have sought under the term of the Natural System. On this idea of -the natural system being, in so far as it has been perfected, genealogical in -its arrangement, with the grades of difference between the descendants from a -common parent, expressed by the terms genera, families, orders, etc., we can -understand the rules which we are compelled to follow in our classification. We -can understand why we value certain resemblances far more than others; why we -are permitted to use rudimentary and useless organs, or others of trifling -physiological importance; why, in comparing one group with a distinct group, we -summarily reject analogical or adaptive characters, and yet use these same -characters within the limits of the same group. We can clearly see how it is -that all living and extinct forms can be grouped together in one great system; -and how the several members of each class are connected together by the most -complex and radiating lines of affinities. We shall never, probably, -disentangle the inextricable web of affinities between the members of any one -class; but when we have a distinct object in view, and do not look to some -unknown plan of creation, we may hope to make sure but slow progress. - -Morphology.—We have seen that the members of the same class, independently of -their habits of life, resemble each other in the general plan of their -organisation. This resemblance is often expressed by the term “unity of type;” -or by saying that the several parts and organs in the different species of the -class are homologous. The whole subject is included under the general name of -Morphology. This is the most interesting department of natural history, and may -be said to be its very soul. What can be more curious than that the hand of a -man, formed for grasping, that of a mole for digging, the leg of the horse, the -paddle of the porpoise, and the wing of the bat, should all be constructed on -the same pattern, and should include the same bones, in the same relative -positions? Geoffroy St. Hilaire has insisted strongly on the high importance of -relative connexion in homologous organs: the parts may change to almost any -extent in form and size, and yet they always remain connected together in the -same order. We never find, for instance, the bones of the arm and forearm, or -of the thigh and leg, transposed. Hence the same names can be given to the -homologous bones in widely different animals. We see the same great law in the -construction of the mouths of insects: what can be more different than the -immensely long spiral proboscis of a sphinx-moth, the curious folded one of a -bee or bug, and the great jaws of a beetle?—yet all these organs, serving for -such different purposes, are formed by infinitely numerous modifications of an -upper lip, mandibles, and two pairs of maxillæ. Analogous laws govern the -construction of the mouths and limbs of crustaceans. So it is with the flowers +Mr. Waterhouse has remarked that, when a member belonging to one group +of animals exhibits an affinity to a quite distinct group, this affinity +in most cases is general and not special: thus, according to Mr. +Waterhouse, of all Rodents, the bizcacha is most nearly related to +Marsupials; but in the points in which it approaches this order, its +relations are general, and not to any one marsupial species more than to +another. As the points of affinity of the bizcacha to Marsupials are +believed to be real and not merely adaptive, they are due on my theory +to inheritance in common. Therefore we must suppose either that all +Rodents, including the bizcacha, branched off from some very ancient +Marsupial, which will have had a character in some degree intermediate +with respect to all existing Marsupials; or that both Rodents and +Marsupials branched off from a common progenitor, and that both groups +have since undergone much modification in divergent directions. On +either view we may suppose that the bizcacha has retained, by +inheritance, more of the character of its ancient progenitor than have +other Rodents; and therefore it will not be specially related to any one +existing Marsupial, but indirectly to all or nearly all Marsupials, from +having partially retained the character of their common progenitor, or +of an early member of the group. On the other hand, of all Marsupials, +as Mr. Waterhouse has remarked, the phascolomys resembles most nearly, +not any one species, but the general order of Rodents. In this case, +however, it may be strongly suspected that the resemblance is only +analogical, owing to the phascolomys having become adapted to habits +like those of a Rodent. The elder De Candolle has made nearly similar +observations on the general nature of the affinities of distinct orders of plants. -Nothing can be more hopeless than to attempt to explain this similarity of -pattern in members of the same class, by utility or by the doctrine of final -causes. The hopelessness of the attempt has been expressly admitted by Owen in -his most interesting work on the ‘Nature of Limbs.’ On the ordinary view of the -independent creation of each being, we can only say that so it is;—that it has -so pleased the Creator to construct each animal and plant. +On the principle of the multiplication and gradual divergence in +character of the species descended from a common parent, together with +their retention by inheritance of some characters in common, we can +understand the excessively complex and radiating affinities by which all +the members of the same family or higher group are connected together. +For the common parent of a whole family of species, now broken up by +extinction into distinct groups and sub-groups, will have transmitted +some of its characters, modified in various ways and degrees, to all; +and the several species will consequently be related to each other by +circuitous lines of affinity of various lengths (as may be seen in the +diagram so often referred to), mounting up through many predecessors. As +it is difficult to show the blood-relationship between the numerous +kindred of any ancient and noble family, even by the aid of a +genealogical tree, and almost impossible to do this without this aid, we +can understand the extraordinary difficulty which naturalists have +experienced in describing, without the aid of a diagram, the various +affinities which they perceive between the many living and extinct +members of the same great natural class. + +Extinction, as we have seen in the fourth chapter, has played an +important part in defining and widening the intervals between the +several groups in each class. We may thus account even for the +distinctness of whole classes from each other—for instance, of birds +from all other vertebrate animals—by the belief that many ancient forms +of life have been utterly lost, through which the early progenitors of +birds were formerly connected with the early progenitors of the other +vertebrate classes. There has been less entire extinction of the forms +of life which once connected fishes with batrachians. There has been +still less in some other classes, as in that of the Crustacea, for here +the most wonderfully diverse forms are still tied together by a long, +but broken, chain of affinities. Extinction has only separated groups: +it has by no means made them; for if every form which has ever lived on +this earth were suddenly to reappear, though it would be quite +impossible to give definitions by which each group could be +distinguished from other groups, as all would blend together by steps as +fine as those between the finest existing varieties, nevertheless a +natural classification, or at least a natural arrangement, would be +possible. We shall see this by turning to the diagram: the letters, A to +L, may represent eleven Silurian genera, some of which have produced +large groups of modified descendants. Every intermediate link between +these eleven genera and their primordial parent, and every intermediate +link in each branch and sub-branch of their descendants, may be supposed +to be still alive; and the links to be as fine as those between the +finest varieties. In this case it would be quite impossible to give any +definition by which the several members of the several groups could be +distinguished from their more immediate parents; or these parents from +their ancient and unknown progenitor. Yet the natural arrangement in the +diagram would still hold good; and, on the principle of inheritance, all +the forms descended from A, or from I, would have something in common. +In a tree we can specify this or that branch, though at the actual fork +the two unite and blend together. We could not, as I have said, define +the several groups; but we could pick out types, or forms, representing +most of the characters of each group, whether large or small, and thus +give a general idea of the value of the differences between them. This +is what we should be driven to, if we were ever to succeed in collecting +all the forms in any class which have lived throughout all time and +space. We shall certainly never succeed in making so perfect a +collection: nevertheless, in certain classes, we are tending in this +direction; and Milne Edwards has lately insisted, in an able paper, on +the high importance of looking to types, whether or not we can separate +and define the groups to which such types belong. + +Finally, we have seen that natural selection, which results from the +struggle for existence, and which almost inevitably induces extinction +and divergence of character in the many descendants from one dominant +parent-species, explains that great and universal feature in the +affinities of all organic beings, namely, their subordination in group +under group. We use the element of descent in classing the individuals +of both sexes and of all ages, although having few characters in common, +under one species; we use descent in classing acknowledged varieties, +however different they may be from their parent; and I believe this +element of descent is the hidden bond of connexion which naturalists +have sought under the term of the Natural System. On this idea of the +natural system being, in so far as it has been perfected, genealogical +in its arrangement, with the grades of difference between the +descendants from a common parent, expressed by the terms genera, +families, orders, etc., we can understand the rules which we are +compelled to follow in our classification. We can understand why we +value certain resemblances far more than others; why we are permitted to +use rudimentary and useless organs, or others of trifling physiological +importance; why, in comparing one group with a distinct group, we +summarily reject analogical or adaptive characters, and yet use these +same characters within the limits of the same group. We can clearly see +how it is that all living and extinct forms can be grouped together in +one great system; and how the several members of each class are +connected together by the most complex and radiating lines of +affinities. We shall never, probably, disentangle the inextricable web +of affinities between the members of any one class; but when we have a +distinct object in view, and do not look to some unknown plan of +creation, we may hope to make sure but slow progress. + +Morphology.—We have seen that the members of the same class, +independently of their habits of life, resemble each other in the +general plan of their organisation. This resemblance is often expressed +by the term “unity of type;” or by saying that the several parts and +organs in the different species of the class are homologous. The whole +subject is included under the general name of Morphology. This is the +most interesting department of natural history, and may be said to be +its very soul. What can be more curious than that the hand of a man, +formed for grasping, that of a mole for digging, the leg of the horse, +the paddle of the porpoise, and the wing of the bat, should all be +constructed on the same pattern, and should include the same bones, in +the same relative positions? Geoffroy St. Hilaire has insisted strongly +on the high importance of relative connexion in homologous organs: the +parts may change to almost any extent in form and size, and yet they +always remain connected together in the same order. We never find, for +instance, the bones of the arm and forearm, or of the thigh and leg, +transposed. Hence the same names can be given to the homologous bones in +widely different animals. We see the same great law in the construction +of the mouths of insects: what can be more different than the immensely +long spiral proboscis of a sphinx-moth, the curious folded one of a bee +or bug, and the great jaws of a beetle?—yet all these organs, serving +for such different purposes, are formed by infinitely numerous +modifications of an upper lip, mandibles, and two pairs of maxillæ. +Analogous laws govern the construction of the mouths and limbs of +crustaceans. So it is with the flowers of plants. + +Nothing can be more hopeless than to attempt to explain this similarity +of pattern in members of the same class, by utility or by the doctrine +of final causes. The hopelessness of the attempt has been expressly +admitted by Owen in his most interesting work on the ‘Nature of Limbs.’ +On the ordinary view of the independent creation of each being, we can +only say that so it is;—that it has so pleased the Creator to construct +each animal and plant. The explanation is manifest on the theory of the natural selection of -successive slight modifications,—each modification being profitable in some way -to the modified form, but often affecting by correlation of growth other parts -of the organisation. In changes of this nature, there will be little or no -tendency to modify the original pattern, or to transpose parts. The bones of a -limb might be shortened and widened to any extent, and become gradually -enveloped in thick membrane, so as to serve as a fin; or a webbed foot might -have all its bones, or certain bones, lengthened to any extent, and the -membrane connecting them increased to any extent, so as to serve as a wing: yet -in all this great amount of modification there will be no tendency to alter the -framework of bones or the relative connexion of the several parts. If we -suppose that the ancient progenitor, the archetype as it may be called, of all +successive slight modifications,—each modification being profitable in +some way to the modified form, but often affecting by correlation of +growth other parts of the organisation. In changes of this nature, there +will be little or no tendency to modify the original pattern, or to +transpose parts. The bones of a limb might be shortened and widened to +any extent, and become gradually enveloped in thick membrane, so as to +serve as a fin; or a webbed foot might have all its bones, or certain +bones, lengthened to any extent, and the membrane connecting them +increased to any extent, so as to serve as a wing: yet in all this great +amount of modification there will be no tendency to alter the framework +of bones or the relative connexion of the several parts. If we suppose +that the ancient progenitor, the archetype as it may be called, of all mammals, had its limbs constructed on the existing general pattern, for -whatever purpose they served, we can at once perceive the plain signification -of the homologous construction of the limbs throughout the whole class. So with -the mouths of insects, we have only to suppose that their common progenitor had -an upper lip, mandibles, and two pair of maxillæ, these parts being perhaps -very simple in form; and then natural selection will account for the infinite -diversity in structure and function of the mouths of insects. Nevertheless, it -is conceivable that the general pattern of an organ might become so much -obscured as to be finally lost, by the atrophy and ultimately by the complete -abortion of certain parts, by the soldering together of other parts, and by the -doubling or multiplication of others,—variations which we know to be within the -limits of possibility. In the paddles of the extinct gigantic sea-lizards, and -in the mouths of certain suctorial crustaceans, the general pattern seems to -have been thus to a certain extent obscured. - -There is another and equally curious branch of the present subject; namely, the -comparison not of the same part in different members of a class, but of the -different parts or organs in the same individual. Most physiologists believe -that the bones of the skull are homologous with—that is correspond in number -and in relative connexion with—the elemental parts of a certain number of -vertebræ. The anterior and posterior limbs in each member of the vertebrate and -articulate classes are plainly homologous. We see the same law in comparing the -wonderfully complex jaws and legs in crustaceans. It is familiar to almost -every one, that in a flower the relative position of the sepals, petals, -stamens, and pistils, as well as their intimate structure, are intelligible on -the view that they consist of metamorphosed leaves, arranged in a spire. In -monstrous plants, we often get direct evidence of the possibility of one organ -being transformed into another; and we can actually see in embryonic -crustaceans and in many other animals, and in flowers, that organs, which when -mature become extremely different, are at an early stage of growth exactly -alike. - -How inexplicable are these facts on the ordinary view of creation! Why should -the brain be enclosed in a box composed of such numerous and such +whatever purpose they served, we can at once perceive the plain +signification of the homologous construction of the limbs throughout the +whole class. So with the mouths of insects, we have only to suppose that +their common progenitor had an upper lip, mandibles, and two pair of +maxillæ, these parts being perhaps very simple in form; and then natural +selection will account for the infinite diversity in structure and +function of the mouths of insects. Nevertheless, it is conceivable that +the general pattern of an organ might become so much obscured as to be +finally lost, by the atrophy and ultimately by the complete abortion of +certain parts, by the soldering together of other parts, and by the +doubling or multiplication of others,—variations which we know to be +within the limits of possibility. In the paddles of the extinct gigantic +sea-lizards, and in the mouths of certain suctorial crustaceans, the +general pattern seems to have been thus to a certain extent obscured. + +There is another and equally curious branch of the present subject; +namely, the comparison not of the same part in different members of a +class, but of the different parts or organs in the same individual. Most +physiologists believe that the bones of the skull are homologous +with—that is correspond in number and in relative connexion with—the +elemental parts of a certain number of vertebræ. The anterior and +posterior limbs in each member of the vertebrate and articulate classes +are plainly homologous. We see the same law in comparing the wonderfully +complex jaws and legs in crustaceans. It is familiar to almost every +one, that in a flower the relative position of the sepals, petals, +stamens, and pistils, as well as their intimate structure, are +intelligible on the view that they consist of metamorphosed leaves, +arranged in a spire. In monstrous plants, we often get direct evidence +of the possibility of one organ being transformed into another; and we +can actually see in embryonic crustaceans and in many other animals, and +in flowers, that organs, which when mature become extremely different, +are at an early stage of growth exactly alike. + +How inexplicable are these facts on the ordinary view of creation! Why +should the brain be enclosed in a box composed of such numerous and such extraordinarily shaped pieces of bone? As Owen has remarked, the benefit -derived from the yielding of the separate pieces in the act of parturition of -mammals, will by no means explain the same construction in the skulls of birds. -Why should similar bones have been created in the formation of the wing and leg -of a bat, used as they are for such totally different purposes? Why should one -crustacean, which has an extremely complex mouth formed of many parts, -consequently always have fewer legs; or conversely, those with many legs have -simpler mouths? Why should the sepals, petals, stamens, and pistils in any -individual flower, though fitted for such widely different purposes, be all +derived from the yielding of the separate pieces in the act of +parturition of mammals, will by no means explain the same construction +in the skulls of birds. Why should similar bones have been created in +the formation of the wing and leg of a bat, used as they are for such +totally different purposes? Why should one crustacean, which has an +extremely complex mouth formed of many parts, consequently always have +fewer legs; or conversely, those with many legs have simpler mouths? Why +should the sepals, petals, stamens, and pistils in any individual +flower, though fitted for such widely different purposes, be all constructed on the same pattern? On the theory of natural selection, we can satisfactorily answer these -questions. In the vertebrata, we see a series of internal vertebræ bearing -certain processes and appendages; in the articulata, we see the body divided -into a series of segments, bearing external appendages; and in flowering -plants, we see a series of successive spiral whorls of leaves. An indefinite -repetition of the same part or organ is the common characteristic (as Owen has -observed) of all low or little-modified forms; therefore we may readily believe -that the unknown progenitor of the vertebrata possessed many vertebræ; the -unknown progenitor of the articulata, many segments; and the unknown progenitor -of flowering plants, many spiral whorls of leaves. We have formerly seen that -parts many times repeated are eminently liable to vary in number and structure; -consequently it is quite probable that natural selection, during a -long-continued course of modification, should have seized on a certain number -of the primordially similar elements, many times repeated, and have adapted -them to the most diverse purposes. And as the whole amount of modification will -have been effected by slight successive steps, we need not wonder at -discovering in such parts or organs, a certain degree of fundamental -resemblance, retained by the strong principle of inheritance. - -In the great class of molluscs, though we can homologise the parts of one -species with those of another and distinct species, we can indicate but few -serial homologies; that is, we are seldom enabled to say that one part or organ -is homologous with another in the same individual. And we can understand this -fact; for in molluscs, even in the lowest members of the class, we do not find -nearly so much indefinite repetition of any one part, as we find in the other -great classes of the animal and vegetable kingdoms. - -Naturalists frequently speak of the skull as formed of metamorphosed vertebræ: -the jaws of crabs as metamorphosed legs; the stamens and pistils of flowers as -metamorphosed leaves; but it would in these cases probably be more correct, as -Professor Huxley has remarked, to speak of both skull and vertebræ, both jaws -and legs, etc.,—as having been metamorphosed, not one from the other, but from -some common element. Naturalists, however, use such language only in a -metaphorical sense: they are far from meaning that during a long course of -descent, primordial organs of any kind—vertebræ in the one case and legs in the -other—have actually been modified into skulls or jaws. Yet so strong is the -appearance of a modification of this nature having occurred, that naturalists -can hardly avoid employing language having this plain signification. On my view -these terms may be used literally; and the wonderful fact of the jaws, for -instance, of a crab retaining numerous characters, which they would probably -have retained through inheritance, if they had really been metamorphosed during -a long course of descent from true legs, or from some simple appendage, is -explained. - -Embryology.—It has already been casually remarked that certain organs in the -individual, which when mature become widely different and serve for different -purposes, are in the embryo exactly alike. The embryos, also, of distinct -animals within the same class are often strikingly similar: a better proof of -this cannot be given, than a circumstance mentioned by Agassiz, namely, that -having forgotten to ticket the embryo of some vertebrate animal, he cannot now -tell whether it be that of a mammal, bird, or reptile. The vermiform larvæ of -moths, flies, beetles, etc., resemble each other much more closely than do the -mature insects; but in the case of larvæ, the embryos are active, and have been -adapted for special lines of life. A trace of the law of embryonic resemblance, -sometimes lasts till a rather late age: thus birds of the same genus, and of -closely allied genera, often resemble each other in their first and second -plumage; as we see in the spotted feathers in the thrush group. In the cat -tribe, most of the species are striped or spotted in lines; and stripes can be -plainly distinguished in the whelp of the lion. We occasionally though rarely -see something of this kind in plants: thus the embryonic leaves of the ulex or -furze, and the first leaves of the phyllodineous acaceas, are pinnate or -divided like the ordinary leaves of the leguminosæ. - -The points of structure, in which the embryos of widely different animals of -the same class resemble each other, often have no direct relation to their -conditions of existence. We cannot, for instance, suppose that in the embryos -of the vertebrata the peculiar loop-like course of the arteries near the -branchial slits are related to similar conditions,—in the young mammal which is -nourished in the womb of its mother, in the egg of the bird which is hatched in -a nest, and in the spawn of a frog under water. We have no more reason to -believe in such a relation, than we have to believe that the same bones in the -hand of a man, wing of a bat, and fin of a porpoise, are related to similar -conditions of life. No one will suppose that the stripes on the whelp of a -lion, or the spots on the young blackbird, are of any use to these animals, or -are related to the conditions to which they are exposed. - -The case, however, is different when an animal during any part of its embryonic -career is active, and has to provide for itself. The period of activity may -come on earlier or later in life; but whenever it comes on, the adaptation of -the larva to its conditions of life is just as perfect and as beautiful as in -the adult animal. From such special adaptations, the similarity of the larvæ or -active embryos of allied animals is sometimes much obscured; and cases could be -given of the larvæ of two species, or of two groups of species, differing quite -as much, or even more, from each other than do their adult parents. In most -cases, however, the larvæ, though active, still obey more or less closely the -law of common embryonic resemblance. Cirripedes afford a good instance of this: -even the illustrious Cuvier did not perceive that a barnacle was, as it -certainly is, a crustacean; but a glance at the larva shows this to be the case -in an unmistakeable manner. So again the two main divisions of cirripedes, the -pedunculated and sessile, which differ widely in external appearance, have -larvæ in all their several stages barely distinguishable. - -The embryo in the course of development generally rises in organisation: I use -this expression, though I am aware that it is hardly possible to define clearly -what is meant by the organisation being higher or lower. But no one probably -will dispute that the butterfly is higher than the caterpillar. In some cases, -however, the mature animal is generally considered as lower in the scale than -the larva, as with certain parasitic crustaceans. To refer once again to -cirripedes: the larvæ in the first stage have three pairs of legs, a very -simple single eye, and a probosciformed mouth, with which they feed largely, -for they increase much in size. In the second stage, answering to the chrysalis -stage of butterflies, they have six pairs of beautifully constructed natatory -legs, a pair of magnificent compound eyes, and extremely complex antennæ; but -they have a closed and imperfect mouth, and cannot feed: their function at this -stage is, to search by their well-developed organs of sense, and to reach by -their active powers of swimming, a proper place on which to become attached and -to undergo their final metamorphosis. When this is completed they are fixed for -life: their legs are now converted into prehensile organs; they again obtain a -well-constructed mouth; but they have no antennæ, and their two eyes are now -reconverted into a minute, single, and very simple eye-spot. In this last and -complete state, cirripedes may be considered as either more highly or more -lowly organised than they were in the larval condition. But in some genera the -larvæ become developed either into hermaphrodites having the ordinary -structure, or into what I have called complemental males: and in the latter, -the development has assuredly been retrograde; for the male is a mere sack, -which lives for a short time, and is destitute of mouth, stomach, or other -organ of importance, excepting for reproduction. - -We are so much accustomed to see differences in structure between the embryo -and the adult, and likewise a close similarity in the embryos of widely -different animals within the same class, that we might be led to look at these -facts as necessarily contingent in some manner on growth. But there is no -obvious reason why, for instance, the wing of a bat, or the fin of a porpoise, -should not have been sketched out with all the parts in proper proportion, as -soon as any structure became visible in the embryo. And in some whole groups of -animals and in certain members of other groups, the embryo does not at any -period differ widely from the adult: thus Owen has remarked in regard to -cuttle-fish, “there is no metamorphosis; the cephalopodic character is -manifested long before the parts of the embryo are completed;” and again in -spiders, “there is nothing worthy to be called a metamorphosis.” The larvæ of -insects, whether adapted to the most diverse and active habits, or quite +questions. In the vertebrata, we see a series of internal vertebræ +bearing certain processes and appendages; in the articulata, we see the +body divided into a series of segments, bearing external appendages; and +in flowering plants, we see a series of successive spiral whorls of +leaves. An indefinite repetition of the same part or organ is the common +characteristic (as Owen has observed) of all low or little-modified +forms; therefore we may readily believe that the unknown progenitor of +the vertebrata possessed many vertebræ; the unknown progenitor of the +articulata, many segments; and the unknown progenitor of flowering +plants, many spiral whorls of leaves. We have formerly seen that parts +many times repeated are eminently liable to vary in number and +structure; consequently it is quite probable that natural selection, +during a long-continued course of modification, should have seized on a +certain number of the primordially similar elements, many times +repeated, and have adapted them to the most diverse purposes. And as the +whole amount of modification will have been effected by slight +successive steps, we need not wonder at discovering in such parts or +organs, a certain degree of fundamental resemblance, retained by the +strong principle of inheritance. + +In the great class of molluscs, though we can homologise the parts of +one species with those of another and distinct species, we can indicate +but few serial homologies; that is, we are seldom enabled to say that +one part or organ is homologous with another in the same individual. And +we can understand this fact; for in molluscs, even in the lowest members +of the class, we do not find nearly so much indefinite repetition of any +one part, as we find in the other great classes of the animal and +vegetable kingdoms. + +Naturalists frequently speak of the skull as formed of metamorphosed +vertebræ: the jaws of crabs as metamorphosed legs; the stamens and +pistils of flowers as metamorphosed leaves; but it would in these cases +probably be more correct, as Professor Huxley has remarked, to speak of +both skull and vertebræ, both jaws and legs, etc.,—as having been +metamorphosed, not one from the other, but from some common element. +Naturalists, however, use such language only in a metaphorical sense: +they are far from meaning that during a long course of descent, +primordial organs of any kind—vertebræ in the one case and legs in the +other—have actually been modified into skulls or jaws. Yet so strong is +the appearance of a modification of this nature having occurred, that +naturalists can hardly avoid employing language having this plain +signification. On my view these terms may be used literally; and the +wonderful fact of the jaws, for instance, of a crab retaining numerous +characters, which they would probably have retained through inheritance, +if they had really been metamorphosed during a long course of descent +from true legs, or from some simple appendage, is explained. + +Embryology.—It has already been casually remarked that certain organs in +the individual, which when mature become widely different and serve for +different purposes, are in the embryo exactly alike. The embryos, also, +of distinct animals within the same class are often strikingly similar: +a better proof of this cannot be given, than a circumstance mentioned by +Agassiz, namely, that having forgotten to ticket the embryo of some +vertebrate animal, he cannot now tell whether it be that of a mammal, +bird, or reptile. The vermiform larvæ of moths, flies, beetles, etc., +resemble each other much more closely than do the mature insects; but in +the case of larvæ, the embryos are active, and have been adapted for +special lines of life. A trace of the law of embryonic resemblance, +sometimes lasts till a rather late age: thus birds of the same genus, +and of closely allied genera, often resemble each other in their first +and second plumage; as we see in the spotted feathers in the thrush +group. In the cat tribe, most of the species are striped or spotted in +lines; and stripes can be plainly distinguished in the whelp of the +lion. We occasionally though rarely see something of this kind in +plants: thus the embryonic leaves of the ulex or furze, and the first +leaves of the phyllodineous acaceas, are pinnate or divided like the +ordinary leaves of the leguminosæ. + +The points of structure, in which the embryos of widely different +animals of the same class resemble each other, often have no direct +relation to their conditions of existence. We cannot, for instance, +suppose that in the embryos of the vertebrata the peculiar loop-like +course of the arteries near the branchial slits are related to similar +conditions,—in the young mammal which is nourished in the womb of its +mother, in the egg of the bird which is hatched in a nest, and in the +spawn of a frog under water. We have no more reason to believe in such a +relation, than we have to believe that the same bones in the hand of a +man, wing of a bat, and fin of a porpoise, are related to similar +conditions of life. No one will suppose that the stripes on the whelp of +a lion, or the spots on the young blackbird, are of any use to these +animals, or are related to the conditions to which they are exposed. + +The case, however, is different when an animal during any part of its +embryonic career is active, and has to provide for itself. The period of +activity may come on earlier or later in life; but whenever it comes on, +the adaptation of the larva to its conditions of life is just as perfect +and as beautiful as in the adult animal. From such special adaptations, +the similarity of the larvæ or active embryos of allied animals is +sometimes much obscured; and cases could be given of the larvæ of two +species, or of two groups of species, differing quite as much, or even +more, from each other than do their adult parents. In most cases, +however, the larvæ, though active, still obey more or less closely the +law of common embryonic resemblance. Cirripedes afford a good instance +of this: even the illustrious Cuvier did not perceive that a barnacle +was, as it certainly is, a crustacean; but a glance at the larva shows +this to be the case in an unmistakeable manner. So again the two main +divisions of cirripedes, the pedunculated and sessile, which differ +widely in external appearance, have larvæ in all their several stages +barely distinguishable. + +The embryo in the course of development generally rises in organisation: +I use this expression, though I am aware that it is hardly possible to +define clearly what is meant by the organisation being higher or lower. +But no one probably will dispute that the butterfly is higher than the +caterpillar. In some cases, however, the mature animal is generally +considered as lower in the scale than the larva, as with certain +parasitic crustaceans. To refer once again to cirripedes: the larvæ in +the first stage have three pairs of legs, a very simple single eye, and +a probosciformed mouth, with which they feed largely, for they increase +much in size. In the second stage, answering to the chrysalis stage of +butterflies, they have six pairs of beautifully constructed natatory +legs, a pair of magnificent compound eyes, and extremely complex +antennæ; but they have a closed and imperfect mouth, and cannot feed: +their function at this stage is, to search by their well-developed +organs of sense, and to reach by their active powers of swimming, a +proper place on which to become attached and to undergo their final +metamorphosis. When this is completed they are fixed for life: their +legs are now converted into prehensile organs; they again obtain a +well-constructed mouth; but they have no antennæ, and their two eyes are +now reconverted into a minute, single, and very simple eye-spot. In this +last and complete state, cirripedes may be considered as either more +highly or more lowly organised than they were in the larval condition. +But in some genera the larvæ become developed either into hermaphrodites +having the ordinary structure, or into what I have called complemental +males: and in the latter, the development has assuredly been retrograde; +for the male is a mere sack, which lives for a short time, and is +destitute of mouth, stomach, or other organ of importance, excepting for +reproduction. + +We are so much accustomed to see differences in structure between the +embryo and the adult, and likewise a close similarity in the embryos of +widely different animals within the same class, that we might be led to +look at these facts as necessarily contingent in some manner on growth. +But there is no obvious reason why, for instance, the wing of a bat, or +the fin of a porpoise, should not have been sketched out with all the +parts in proper proportion, as soon as any structure became visible in +the embryo. And in some whole groups of animals and in certain members +of other groups, the embryo does not at any period differ widely from +the adult: thus Owen has remarked in regard to cuttle-fish, “there is no +metamorphosis; the cephalopodic character is manifested long before the +parts of the embryo are completed;” and again in spiders, “there is +nothing worthy to be called a metamorphosis.” The larvæ of insects, +whether adapted to the most diverse and active habits, or quite inactive, being fed by their parents or placed in the midst of proper nutriment, yet nearly all pass through a similar worm-like stage of -development; but in some few cases, as in that of Aphis, if we look to the -admirable drawings by Professor Huxley of the development of this insect, we -see no trace of the vermiform stage. - -How, then, can we explain these several facts in embryology,—namely the very -general, but not universal difference in structure between the embryo and the -adult;—of parts in the same individual embryo, which ultimately become very -unlike and serve for diverse purposes, being at this early period of growth -alike;—of embryos of different species within the same class, generally, but -not universally, resembling each other;—of the structure of the embryo not -being closely related to its conditions of existence, except when the embryo -becomes at any period of life active and has to provide for itself;—of the -embryo apparently having sometimes a higher organisation than the mature -animal, into which it is developed. I believe that all these facts can be -explained, as follows, on the view of descent with modification. - -It is commonly assumed, perhaps from monstrosities often affecting the embryo -at a very early period, that slight variations necessarily appear at an equally -early period. But we have little evidence on this head—indeed the evidence -rather points the other way; for it is notorious that breeders of cattle, -horses, and various fancy animals, cannot positively tell, until some time -after the animal has been born, what its merits or form will ultimately turn -out. We see this plainly in our own children; we cannot always tell whether the -child will be tall or short, or what its precise features will be. The question -is not, at what period of life any variation has been caused, but at what -period it is fully displayed. The cause may have acted, and I believe generally -has acted, even before the embryo is formed; and the variation may be due to -the male and female sexual elements having been affected by the conditions to -which either parent, or their ancestors, have been exposed. Nevertheless an -effect thus caused at a very early period, even before the formation of the -embryo, may appear late in life; as when an hereditary disease, which appears -in old age alone, has been communicated to the offspring from the reproductive -element of one parent. Or again, as when the horns of cross-bred cattle have -been affected by the shape of the horns of either parent. For the welfare of a -very young animal, as long as it remains in its mother’s womb, or in the egg, -or as long as it is nourished and protected by its parent, it must be quite -unimportant whether most of its characters are fully acquired a little earlier -or later in life. It would not signify, for instance, to a bird which obtained -its food best by having a long beak, whether or not it assumed a beak of this -particular length, as long as it was fed by its parents. Hence, I conclude, -that it is quite possible, that each of the many successive modifications, by -which each species has acquired its present structure, may have supervened at a -not very early period of life; and some direct evidence from our domestic -animals supports this view. But in other cases it is quite possible that each -successive modification, or most of them, may have appeared at an extremely -early period. - -I have stated in the first chapter, that there is some evidence to render it -probable, that at whatever age any variation first appears in the parent, it -tends to reappear at a corresponding age in the offspring. Certain variations -can only appear at corresponding ages, for instance, peculiarities in the -caterpillar, cocoon, or imago states of the silk-moth; or, again, in the horns -of almost full-grown cattle. But further than this, variations which, for all -that we can see, might have appeared earlier or later in life, tend to appear -at a corresponding age in the offspring and parent. I am far from meaning that -this is invariably the case; and I could give a good many cases of variations -(taking the word in the largest sense) which have supervened at an earlier age -in the child than in the parent. - -These two principles, if their truth be admitted, will, I believe, explain all -the above specified leading facts in embryology. But first let us look at a few -analogous cases in domestic varieties. Some authors who have written on Dogs, -maintain that the greyhound and bulldog, though appearing so different, are -really varieties most closely allied, and have probably descended from the same -wild stock; hence I was curious to see how far their puppies differed from each -other: I was told by breeders that they differed just as much as their parents, -and this, judging by the eye, seemed almost to be the case; but on actually -measuring the old dogs and their six-days old puppies, I found that the puppies -had not nearly acquired their full amount of proportional difference. So, -again, I was told that the foals of cart and race-horses differed as much as -the full-grown animals; and this surprised me greatly, as I think it probable -that the difference between these two breeds has been wholly caused by -selection under domestication; but having had careful measurements made of the -dam and of a three-days old colt of a race and heavy cart-horse, I find that -the colts have by no means acquired their full amount of proportional -difference. - -As the evidence appears to me conclusive, that the several domestic breeds of -Pigeon have descended from one wild species, I compared young pigeons of -various breeds, within twelve hours after being hatched; I carefully measured -the proportions (but will not here give details) of the beak, width of mouth, -length of nostril and of eyelid, size of feet and length of leg, in the wild -stock, in pouters, fantails, runts, barbs, dragons, carriers, and tumblers. Now -some of these birds, when mature, differ so extraordinarily in length and form -of beak, that they would, I cannot doubt, be ranked in distinct genera, had -they been natural productions. But when the nestling birds of these several -breeds were placed in a row, though most of them could be distinguished from -each other, yet their proportional differences in the above specified several -points were incomparably less than in the full-grown birds. Some characteristic -points of difference—for instance, that of the width of mouth—could hardly be -detected in the young. But there was one remarkable exception to this rule, for -the young of the short-faced tumbler differed from the young of the wild -rock-pigeon and of the other breeds, in all its proportions, almost exactly as -much as in the adult state. - -The two principles above given seem to me to explain these facts in regard to -the later embryonic stages of our domestic varieties. Fanciers select their -horses, dogs, and pigeons, for breeding, when they are nearly grown up: they -are indifferent whether the desired qualities and structures have been acquired -earlier or later in life, if the full-grown animal possesses them. And the -cases just given, more especially that of pigeons, seem to show that the -characteristic differences which give value to each breed, and which have been -accumulated by man’s selection, have not generally first appeared at an early -period of life, and have been inherited by the offspring at a corresponding not -early period. But the case of the short-faced tumbler, which when twelve hours -old had acquired its proper proportions, proves that this is not the universal -rule; for here the characteristic differences must either have appeared at an -earlier period than usual, or, if not so, the differences must have been -inherited, not at the corresponding, but at an earlier age. - -Now let us apply these facts and the above two principles—which latter, though -not proved true, can be shown to be in some degree probable—to species in a -state of nature. Let us take a genus of birds, descended on my theory from some -one parent-species, and of which the several new species have become modified -through natural selection in accordance with their diverse habits. Then, from -the many slight successive steps of variation having supervened at a rather -late age, and having been inherited at a corresponding age, the young of the -new species of our supposed genus will manifestly tend to resemble each other -much more closely than do the adults, just as we have seen in the case of -pigeons. We may extend this view to whole families or even classes. The -fore-limbs, for instance, which served as legs in the parent-species, may -become, by a long course of modification, adapted in one descendant to act as -hands, in another as paddles, in another as wings; and on the above two -principles—namely of each successive modification supervening at a rather late -age, and being inherited at a corresponding late age—the fore-limbs in the -embryos of the several descendants of the parent-species will still resemble -each other closely, for they will not have been modified. But in each -individual new species, the embryonic fore-limbs will differ greatly from the -fore-limbs in the mature animal; the limbs in the latter having undergone much -modification at a rather late period of life, and having thus been converted -into hands, or paddles, or wings. Whatever influence long-continued exercise or -use on the one hand, and disuse on the other, may have in modifying an organ, -such influence will mainly affect the mature animal, which has come to its full -powers of activity and has to gain its own living; and the effects thus -produced will be inherited at a corresponding mature age. Whereas the young -will remain unmodified, or be modified in a lesser degree, by the effects of -use and disuse. - -In certain cases the successive steps of variation might supervene, from causes -of which we are wholly ignorant, at a very early period of life, or each step -might be inherited at an earlier period than that at which it first appeared. -In either case (as with the short-faced tumbler) the young or embryo would -closely resemble the mature parent-form. We have seen that this is the rule of -development in certain whole groups of animals, as with cuttle-fish and -spiders, and with a few members of the great class of insects, as with Aphis. -With respect to the final cause of the young in these cases not undergoing any -metamorphosis, or closely resembling their parents from their earliest age, we -can see that this would result from the two following contingencies; firstly, -from the young, during a course of modification carried on for many -generations, having to provide for their own wants at a very early stage of -development, and secondly, from their following exactly the same habits of life -with their parents; for in this case, it would be indispensable for the -existence of the species, that the child should be modified at a very early age -in the same manner with its parents, in accordance with their similar habits. -Some further explanation, however, of the embryo not undergoing any -metamorphosis is perhaps requisite. If, on the other hand, it profited the -young to follow habits of life in any degree different from those of their -parent, and consequently to be constructed in a slightly different manner, -then, on the principle of inheritance at corresponding ages, the active young -or larvæ might easily be rendered by natural selection different to any -conceivable extent from their parents. Such differences might, also, become -correlated with successive stages of development; so that the larvæ, in the -first stage, might differ greatly from the larvæ in the second stage, as we -have seen to be the case with cirripedes. The adult might become fitted for -sites or habits, in which organs of locomotion or of the senses, etc., would be +development; but in some few cases, as in that of Aphis, if we look to +the admirable drawings by Professor Huxley of the development of this +insect, we see no trace of the vermiform stage. + +How, then, can we explain these several facts in embryology,—namely the +very general, but not universal difference in structure between the +embryo and the adult;—of parts in the same individual embryo, which +ultimately become very unlike and serve for diverse purposes, being at +this early period of growth alike;—of embryos of different species +within the same class, generally, but not universally, resembling each +other;—of the structure of the embryo not being closely related to its +conditions of existence, except when the embryo becomes at any period of +life active and has to provide for itself;—of the embryo apparently +having sometimes a higher organisation than the mature animal, into +which it is developed. I believe that all these facts can be explained, +as follows, on the view of descent with modification. + +It is commonly assumed, perhaps from monstrosities often affecting the +embryo at a very early period, that slight variations necessarily appear +at an equally early period. But we have little evidence on this +head—indeed the evidence rather points the other way; for it is +notorious that breeders of cattle, horses, and various fancy animals, +cannot positively tell, until some time after the animal has been born, +what its merits or form will ultimately turn out. We see this plainly in +our own children; we cannot always tell whether the child will be tall +or short, or what its precise features will be. The question is not, at +what period of life any variation has been caused, but at what period it +is fully displayed. The cause may have acted, and I believe generally +has acted, even before the embryo is formed; and the variation may be +due to the male and female sexual elements having been affected by the +conditions to which either parent, or their ancestors, have been +exposed. Nevertheless an effect thus caused at a very early period, even +before the formation of the embryo, may appear late in life; as when an +hereditary disease, which appears in old age alone, has been +communicated to the offspring from the reproductive element of one +parent. Or again, as when the horns of cross-bred cattle have been +affected by the shape of the horns of either parent. For the welfare of +a very young animal, as long as it remains in its mother’s womb, or in +the egg, or as long as it is nourished and protected by its parent, it +must be quite unimportant whether most of its characters are fully +acquired a little earlier or later in life. It would not signify, for +instance, to a bird which obtained its food best by having a long beak, +whether or not it assumed a beak of this particular length, as long as +it was fed by its parents. Hence, I conclude, that it is quite possible, +that each of the many successive modifications, by which each species +has acquired its present structure, may have supervened at a not very +early period of life; and some direct evidence from our domestic animals +supports this view. But in other cases it is quite possible that each +successive modification, or most of them, may have appeared at an +extremely early period. + +I have stated in the first chapter, that there is some evidence to +render it probable, that at whatever age any variation first appears in +the parent, it tends to reappear at a corresponding age in the +offspring. Certain variations can only appear at corresponding ages, for +instance, peculiarities in the caterpillar, cocoon, or imago states of +the silk-moth; or, again, in the horns of almost full-grown cattle. But +further than this, variations which, for all that we can see, might have +appeared earlier or later in life, tend to appear at a corresponding age +in the offspring and parent. I am far from meaning that this is +invariably the case; and I could give a good many cases of variations +(taking the word in the largest sense) which have supervened at an +earlier age in the child than in the parent. + +These two principles, if their truth be admitted, will, I believe, +explain all the above specified leading facts in embryology. But first +let us look at a few analogous cases in domestic varieties. Some authors +who have written on Dogs, maintain that the greyhound and bulldog, +though appearing so different, are really varieties most closely allied, +and have probably descended from the same wild stock; hence I was +curious to see how far their puppies differed from each other: I was +told by breeders that they differed just as much as their parents, and +this, judging by the eye, seemed almost to be the case; but on actually +measuring the old dogs and their six-days old puppies, I found that the +puppies had not nearly acquired their full amount of proportional +difference. So, again, I was told that the foals of cart and race-horses +differed as much as the full-grown animals; and this surprised me +greatly, as I think it probable that the difference between these two +breeds has been wholly caused by selection under domestication; but +having had careful measurements made of the dam and of a three-days old +colt of a race and heavy cart-horse, I find that the colts have by no +means acquired their full amount of proportional difference. + +As the evidence appears to me conclusive, that the several domestic +breeds of Pigeon have descended from one wild species, I compared young +pigeons of various breeds, within twelve hours after being hatched; I +carefully measured the proportions (but will not here give details) of +the beak, width of mouth, length of nostril and of eyelid, size of feet +and length of leg, in the wild stock, in pouters, fantails, runts, +barbs, dragons, carriers, and tumblers. Now some of these birds, when +mature, differ so extraordinarily in length and form of beak, that they +would, I cannot doubt, be ranked in distinct genera, had they been +natural productions. But when the nestling birds of these several breeds +were placed in a row, though most of them could be distinguished from +each other, yet their proportional differences in the above specified +several points were incomparably less than in the full-grown birds. Some +characteristic points of difference—for instance, that of the width of +mouth—could hardly be detected in the young. But there was one +remarkable exception to this rule, for the young of the short-faced +tumbler differed from the young of the wild rock-pigeon and of the other +breeds, in all its proportions, almost exactly as much as in the adult +state. + +The two principles above given seem to me to explain these facts in +regard to the later embryonic stages of our domestic varieties. Fanciers +select their horses, dogs, and pigeons, for breeding, when they are +nearly grown up: they are indifferent whether the desired qualities and +structures have been acquired earlier or later in life, if the +full-grown animal possesses them. And the cases just given, more +especially that of pigeons, seem to show that the characteristic +differences which give value to each breed, and which have been +accumulated by man’s selection, have not generally first appeared at an +early period of life, and have been inherited by the offspring at a +corresponding not early period. But the case of the short-faced tumbler, +which when twelve hours old had acquired its proper proportions, proves +that this is not the universal rule; for here the characteristic +differences must either have appeared at an earlier period than usual, +or, if not so, the differences must have been inherited, not at the +corresponding, but at an earlier age. + +Now let us apply these facts and the above two principles—which latter, +though not proved true, can be shown to be in some degree probable—to +species in a state of nature. Let us take a genus of birds, descended on +my theory from some one parent-species, and of which the several new +species have become modified through natural selection in accordance +with their diverse habits. Then, from the many slight successive steps +of variation having supervened at a rather late age, and having been +inherited at a corresponding age, the young of the new species of our +supposed genus will manifestly tend to resemble each other much more +closely than do the adults, just as we have seen in the case of pigeons. +We may extend this view to whole families or even classes. The +fore-limbs, for instance, which served as legs in the parent-species, +may become, by a long course of modification, adapted in one descendant +to act as hands, in another as paddles, in another as wings; and on the +above two principles—namely of each successive modification supervening +at a rather late age, and being inherited at a corresponding late +age—the fore-limbs in the embryos of the several descendants of the +parent-species will still resemble each other closely, for they will not +have been modified. But in each individual new species, the embryonic +fore-limbs will differ greatly from the fore-limbs in the mature animal; +the limbs in the latter having undergone much modification at a rather +late period of life, and having thus been converted into hands, or +paddles, or wings. Whatever influence long-continued exercise or use on +the one hand, and disuse on the other, may have in modifying an organ, +such influence will mainly affect the mature animal, which has come to +its full powers of activity and has to gain its own living; and the +effects thus produced will be inherited at a corresponding mature age. +Whereas the young will remain unmodified, or be modified in a lesser +degree, by the effects of use and disuse. + +In certain cases the successive steps of variation might supervene, from +causes of which we are wholly ignorant, at a very early period of life, +or each step might be inherited at an earlier period than that at which +it first appeared. In either case (as with the short-faced tumbler) the +young or embryo would closely resemble the mature parent-form. We have +seen that this is the rule of development in certain whole groups of +animals, as with cuttle-fish and spiders, and with a few members of the +great class of insects, as with Aphis. With respect to the final cause +of the young in these cases not undergoing any metamorphosis, or closely +resembling their parents from their earliest age, we can see that this +would result from the two following contingencies; firstly, from the +young, during a course of modification carried on for many generations, +having to provide for their own wants at a very early stage of +development, and secondly, from their following exactly the same habits +of life with their parents; for in this case, it would be indispensable +for the existence of the species, that the child should be modified at a +very early age in the same manner with its parents, in accordance with +their similar habits. Some further explanation, however, of the embryo +not undergoing any metamorphosis is perhaps requisite. If, on the other +hand, it profited the young to follow habits of life in any degree +different from those of their parent, and consequently to be constructed +in a slightly different manner, then, on the principle of inheritance at +corresponding ages, the active young or larvæ might easily be rendered +by natural selection different to any conceivable extent from their +parents. Such differences might, also, become correlated with successive +stages of development; so that the larvæ, in the first stage, might +differ greatly from the larvæ in the second stage, as we have seen to be +the case with cirripedes. The adult might become fitted for sites or +habits, in which organs of locomotion or of the senses, etc., would be useless; and in this case the final metamorphosis would be said to be retrograde. -As all the organic beings, extinct and recent, which have ever lived on this -earth have to be classed together, and as all have been connected by the finest -gradations, the best, or indeed, if our collections were nearly perfect, the -only possible arrangement, would be genealogical. Descent being on my view the -hidden bond of connexion which naturalists have been seeking under the term of -the natural system. On this view we can understand how it is that, in the eyes -of most naturalists, the structure of the embryo is even more important for -classification than that of the adult. For the embryo is the animal in its less -modified state; and in so far it reveals the structure of its progenitor. In -two groups of animal, however much they may at present differ from each other -in structure and habits, if they pass through the same or similar embryonic -stages, we may feel assured that they have both descended from the same or -nearly similar parents, and are therefore in that degree closely related. Thus, -community in embryonic structure reveals community of descent. It will reveal -this community of descent, however much the structure of the adult may have -been modified and obscured; we have seen, for instance, that cirripedes can at -once be recognised by their larvæ as belonging to the great class of -crustaceans. As the embryonic state of each species and group of species -partially shows us the structure of their less modified ancient progenitors, we -can clearly see why ancient and extinct forms of life should resemble the -embryos of their descendants,—our existing species. Agassiz believes this to be -a law of nature; but I am bound to confess that I only hope to see the law -hereafter proved true. It can be proved true in those cases alone in which the -ancient state, now supposed to be represented in many embryos, has not been -obliterated, either by the successive variations in a long course of -modification having supervened at a very early age, or by the variations having -been inherited at an earlier period than that at which they first appeared. It -should also be borne in mind, that the supposed law of resemblance of ancient -forms of life to the embryonic stages of recent forms, may be true, but yet, -owing to the geological record not extending far enough back in time, may -remain for a long period, or for ever, incapable of demonstration. - -Thus, as it seems to me, the leading facts in embryology, which are second in -importance to none in natural history, are explained on the principle of slight -modifications not appearing, in the many descendants from some one ancient -progenitor, at a very early period in the life of each, though perhaps caused -at the earliest, and being inherited at a corresponding not early period. -Embryology rises greatly in interest, when we thus look at the embryo as a -picture, more or less obscured, of the common parent-form of each great class -of animals. - -Rudimentary, atrophied, or aborted organs.—Organs or parts in this strange -condition, bearing the stamp of inutility, are extremely common throughout -nature. For instance, rudimentary mammæ are very general in the males of -mammals: I presume that the “bastard-wing” in birds may be safely considered as -a digit in a rudimentary state: in very many snakes one lobe of the lungs is -rudimentary; in other snakes there are rudiments of the pelvis and hind limbs. -Some of the cases of rudimentary organs are extremely curious; for instance, -the presence of teeth in foetal whales, which when grown up have not a tooth in -their heads; and the presence of teeth, which never cut through the gums, in -the upper jaws of our unborn calves. It has even been stated on good authority -that rudiments of teeth can be detected in the beaks of certain embryonic -birds. Nothing can be plainer than that wings are formed for flight, yet in how -many insects do we see wings so reduced in size as to be utterly incapable of -flight, and not rarely lying under wing-cases, firmly soldered together! - -The meaning of rudimentary organs is often quite unmistakeable: for instance -there are beetles of the same genus (and even of the same species) resembling -each other most closely in all respects, one of which will have full-sized -wings, and another mere rudiments of membrane; and here it is impossible to -doubt, that the rudiments represent wings. Rudimentary organs sometimes retain -their potentiality, and are merely not developed: this seems to be the case -with the mammæ of male mammals, for many instances are on record of these -organs having become well developed in full-grown males, and having secreted -milk. So again there are normally four developed and two rudimentary teats in -the udders of the genus Bos, but in our domestic cows the two sometimes become -developed and give milk. In individual plants of the same species the petals -sometimes occur as mere rudiments, and sometimes in a well-developed state. In -plants with separated sexes, the male flowers often have a rudiment of a -pistil; and Kölreuter found that by crossing such male plants with an -hermaphrodite species, the rudiment of the pistil in the hybrid offspring was -much increased in size; and this shows that the rudiment and the perfect pistil -are essentially alike in nature. - -An organ serving for two purposes, may become rudimentary or utterly aborted -for one, even the more important purpose; and remain perfectly efficient for -the other. Thus in plants, the office of the pistil is to allow the -pollen-tubes to reach the ovules protected in the ovarium at its base. The -pistil consists of a stigma supported on the style; but in some Compositæ, the -male florets, which of course cannot be fecundated, have a pistil, which is in -a rudimentary state, for it is not crowned with a stigma; but the style remains -well developed, and is clothed with hairs as in other compositæ, for the -purpose of brushing the pollen out of the surrounding anthers. Again, an organ -may become rudimentary for its proper purpose, and be used for a distinct -object: in certain fish the swim-bladder seems to be rudimentary for its proper -function of giving buoyancy, but has become converted into a nascent breathing -organ or lung. Other similar instances could be given. - -Rudimentary organs in the individuals of the same species are very liable to -vary in degree of development and in other respects. Moreover, in closely -allied species, the degree to which the same organ has been rendered -rudimentary occasionally differs much. This latter fact is well exemplified in -the state of the wings of the female moths in certain groups. Rudimentary -organs may be utterly aborted; and this implies, that we find in an animal or -plant no trace of an organ, which analogy would lead us to expect to find, and -which is occasionally found in monstrous individuals of the species. Thus in -the snapdragon (antirrhinum) we generally do not find a rudiment of a fifth -stamen; but this may sometimes be seen. In tracing the homologies of the same -part in different members of a class, nothing is more common, or more -necessary, than the use and discovery of rudiments. This is well shown in the -drawings given by Owen of the bones of the leg of the horse, ox, and -rhinoceros. - -It is an important fact that rudimentary organs, such as teeth in the upper -jaws of whales and ruminants, can often be detected in the embryo, but -afterwards wholly disappear. It is also, I believe, a universal rule, that a -rudimentary part or organ is of greater size relatively to the adjoining parts -in the embryo, than in the adult; so that the organ at this early age is less -rudimentary, or even cannot be said to be in any degree rudimentary. Hence, -also, a rudimentary organ in the adult, is often said to have retained its -embryonic condition. - -I have now given the leading facts with respect to rudimentary organs. In -reflecting on them, every one must be struck with astonishment: for the same -reasoning power which tells us plainly that most parts and organs are -exquisitely adapted for certain purposes, tells us with equal plainness that -these rudimentary or atrophied organs, are imperfect and useless. In works on -natural history rudimentary organs are generally said to have been created “for -the sake of symmetry,” or in order “to complete the scheme of nature;” but this -seems to me no explanation, merely a restatement of the fact. Would it be -thought sufficient to say that because planets revolve in elliptic courses -round the sun, satellites follow the same course round the planets, for the -sake of symmetry, and to complete the scheme of nature? An eminent physiologist -accounts for the presence of rudimentary organs, by supposing that they serve -to excrete matter in excess, or injurious to the system; but can we suppose -that the minute papilla, which often represents the pistil in male flowers, and -which is formed merely of cellular tissue, can thus act? Can we suppose that -the formation of rudimentary teeth which are subsequently absorbed, can be of -any service to the rapidly growing embryonic calf by the excretion of precious -phosphate of lime? When a man’s fingers have been amputated, imperfect nails -sometimes appear on the stumps: I could as soon believe that these vestiges of -nails have appeared, not from unknown laws of growth, but in order to excrete -horny matter, as that the rudimentary nails on the fin of the manatee were +As all the organic beings, extinct and recent, which have ever lived on +this earth have to be classed together, and as all have been connected +by the finest gradations, the best, or indeed, if our collections were +nearly perfect, the only possible arrangement, would be genealogical. +Descent being on my view the hidden bond of connexion which naturalists +have been seeking under the term of the natural system. On this view we +can understand how it is that, in the eyes of most naturalists, the +structure of the embryo is even more important for classification than +that of the adult. For the embryo is the animal in its less modified +state; and in so far it reveals the structure of its progenitor. In two +groups of animal, however much they may at present differ from each +other in structure and habits, if they pass through the same or similar +embryonic stages, we may feel assured that they have both descended from +the same or nearly similar parents, and are therefore in that degree +closely related. Thus, community in embryonic structure reveals +community of descent. It will reveal this community of descent, however +much the structure of the adult may have been modified and obscured; we +have seen, for instance, that cirripedes can at once be recognised by +their larvæ as belonging to the great class of crustaceans. As the +embryonic state of each species and group of species partially shows us +the structure of their less modified ancient progenitors, we can clearly +see why ancient and extinct forms of life should resemble the embryos of +their descendants,—our existing species. Agassiz believes this to be a +law of nature; but I am bound to confess that I only hope to see the law +hereafter proved true. It can be proved true in those cases alone in +which the ancient state, now supposed to be represented in many embryos, +has not been obliterated, either by the successive variations in a long +course of modification having supervened at a very early age, or by the +variations having been inherited at an earlier period than that at which +they first appeared. It should also be borne in mind, that the supposed +law of resemblance of ancient forms of life to the embryonic stages of +recent forms, may be true, but yet, owing to the geological record not +extending far enough back in time, may remain for a long period, or for +ever, incapable of demonstration. + +Thus, as it seems to me, the leading facts in embryology, which are +second in importance to none in natural history, are explained on the +principle of slight modifications not appearing, in the many descendants +from some one ancient progenitor, at a very early period in the life of +each, though perhaps caused at the earliest, and being inherited at a +corresponding not early period. Embryology rises greatly in interest, +when we thus look at the embryo as a picture, more or less obscured, of +the common parent-form of each great class of animals. + +Rudimentary, atrophied, or aborted organs.—Organs or parts in this +strange condition, bearing the stamp of inutility, are extremely common +throughout nature. For instance, rudimentary mammæ are very general in +the males of mammals: I presume that the “bastard-wing” in birds may be +safely considered as a digit in a rudimentary state: in very many snakes +one lobe of the lungs is rudimentary; in other snakes there are +rudiments of the pelvis and hind limbs. Some of the cases of +rudimentary organs are extremely curious; for instance, the presence of +teeth in foetal whales, which when grown up have not a tooth in their +heads; and the presence of teeth, which never cut through the gums, in +the upper jaws of our unborn calves. It has even been stated on good +authority that rudiments of teeth can be detected in the beaks of +certain embryonic birds. Nothing can be plainer than that wings are +formed for flight, yet in how many insects do we see wings so reduced in +size as to be utterly incapable of flight, and not rarely lying under +wing-cases, firmly soldered together! + +The meaning of rudimentary organs is often quite unmistakeable: for +instance there are beetles of the same genus (and even of the same +species) resembling each other most closely in all respects, one of +which will have full-sized wings, and another mere rudiments of +membrane; and here it is impossible to doubt, that the rudiments +represent wings. Rudimentary organs sometimes retain their potentiality, +and are merely not developed: this seems to be the case with the mammæ +of male mammals, for many instances are on record of these organs having +become well developed in full-grown males, and having secreted milk. So +again there are normally four developed and two rudimentary teats in the +udders of the genus Bos, but in our domestic cows the two sometimes +become developed and give milk. In individual plants of the same species +the petals sometimes occur as mere rudiments, and sometimes in a +well-developed state. In plants with separated sexes, the male flowers +often have a rudiment of a pistil; and Kölreuter found that by crossing +such male plants with an hermaphrodite species, the rudiment of the +pistil in the hybrid offspring was much increased in size; and this +shows that the rudiment and the perfect pistil are essentially alike in +nature. + +An organ serving for two purposes, may become rudimentary or utterly +aborted for one, even the more important purpose; and remain perfectly +efficient for the other. Thus in plants, the office of the pistil is to +allow the pollen-tubes to reach the ovules protected in the ovarium at +its base. The pistil consists of a stigma supported on the style; but in +some Compositæ, the male florets, which of course cannot be fecundated, +have a pistil, which is in a rudimentary state, for it is not crowned +with a stigma; but the style remains well developed, and is clothed with +hairs as in other compositæ, for the purpose of brushing the pollen out +of the surrounding anthers. Again, an organ may become rudimentary for +its proper purpose, and be used for a distinct object: in certain fish +the swim-bladder seems to be rudimentary for its proper function of +giving buoyancy, but has become converted into a nascent breathing organ +or lung. Other similar instances could be given. + +Rudimentary organs in the individuals of the same species are very +liable to vary in degree of development and in other respects. Moreover, +in closely allied species, the degree to which the same organ has been +rendered rudimentary occasionally differs much. This latter fact is well +exemplified in the state of the wings of the female moths in certain +groups. Rudimentary organs may be utterly aborted; and this implies, +that we find in an animal or plant no trace of an organ, which analogy +would lead us to expect to find, and which is occasionally found in +monstrous individuals of the species. Thus in the snapdragon +(antirrhinum) we generally do not find a rudiment of a fifth stamen; but +this may sometimes be seen. In tracing the homologies of the same part +in different members of a class, nothing is more common, or more +necessary, than the use and discovery of rudiments. This is well shown +in the drawings given by Owen of the bones of the leg of the horse, ox, +and rhinoceros. + +It is an important fact that rudimentary organs, such as teeth in the +upper jaws of whales and ruminants, can often be detected in the embryo, +but afterwards wholly disappear. It is also, I believe, a universal +rule, that a rudimentary part or organ is of greater size relatively to +the adjoining parts in the embryo, than in the adult; so that the organ +at this early age is less rudimentary, or even cannot be said to be in +any degree rudimentary. Hence, also, a rudimentary organ in the adult, +is often said to have retained its embryonic condition. + +I have now given the leading facts with respect to rudimentary organs. +In reflecting on them, every one must be struck with astonishment: for +the same reasoning power which tells us plainly that most parts and +organs are exquisitely adapted for certain purposes, tells us with equal +plainness that these rudimentary or atrophied organs, are imperfect and +useless. In works on natural history rudimentary organs are generally +said to have been created “for the sake of symmetry,” or in order “to +complete the scheme of nature;” but this seems to me no explanation, +merely a restatement of the fact. Would it be thought sufficient to say +that because planets revolve in elliptic courses round the sun, +satellites follow the same course round the planets, for the sake of +symmetry, and to complete the scheme of nature? An eminent physiologist +accounts for the presence of rudimentary organs, by supposing that they +serve to excrete matter in excess, or injurious to the system; but can +we suppose that the minute papilla, which often represents the pistil in +male flowers, and which is formed merely of cellular tissue, can thus +act? Can we suppose that the formation of rudimentary teeth which are +subsequently absorbed, can be of any service to the rapidly growing +embryonic calf by the excretion of precious phosphate of lime? When a +man’s fingers have been amputated, imperfect nails sometimes appear on +the stumps: I could as soon believe that these vestiges of nails have +appeared, not from unknown laws of growth, but in order to excrete horny +matter, as that the rudimentary nails on the fin of the manatee were formed for this purpose. -On my view of descent with modification, the origin of rudimentary organs is -simple. We have plenty of cases of rudimentary organs in our domestic -productions,—as the stump of a tail in tailless breeds,—the vestige of an ear -in earless breeds,—the reappearance of minute dangling horns in hornless breeds -of cattle, more especially, according to Youatt, in young animals,—and the -state of the whole flower in the cauliflower. We often see rudiments of various -parts in monsters. But I doubt whether any of these cases throw light on the -origin of rudimentary organs in a state of nature, further than by showing that +On my view of descent with modification, the origin of rudimentary +organs is simple. We have plenty of cases of rudimentary organs in our +domestic productions,—as the stump of a tail in tailless breeds,—the +vestige of an ear in earless breeds,—the reappearance of minute dangling +horns in hornless breeds of cattle, more especially, according to +Youatt, in young animals,—and the state of the whole flower in the +cauliflower. We often see rudiments of various parts in monsters. But I +doubt whether any of these cases throw light on the origin of +rudimentary organs in a state of nature, further than by showing that rudiments can be produced; for I doubt whether species under nature ever -undergo abrupt changes. I believe that disuse has been the main agency; that it -has led in successive generations to the gradual reduction of various organs, -until they have become rudimentary,—as in the case of the eyes of animals -inhabiting dark caverns, and of the wings of birds inhabiting oceanic islands, -which have seldom been forced to take flight, and have ultimately lost the -power of flying. Again, an organ useful under certain conditions, might become -injurious under others, as with the wings of beetles living on small and -exposed islands; and in this case natural selection would continue slowly to -reduce the organ, until it was rendered harmless and rudimentary. - -Any change in function, which can be effected by insensibly small steps, is -within the power of natural selection; so that an organ rendered, during -changed habits of life, useless or injurious for one purpose, might easily be -modified and used for another purpose. Or an organ might be retained for one -alone of its former functions. An organ, when rendered useless, may well be -variable, for its variations cannot be checked by natural selection. At -whatever period of life disuse or selection reduces an organ, and this will -generally be when the being has come to maturity and to its full powers of -action, the principle of inheritance at corresponding ages will reproduce the -organ in its reduced state at the same age, and consequently will seldom affect -or reduce it in the embryo. Thus we can understand the greater relative size of -rudimentary organs in the embryo, and their lesser relative size in the adult. -But if each step of the process of reduction were to be inherited, not at the -corresponding age, but at an extremely early period of life (as we have good -reason to believe to be possible) the rudimentary part would tend to be wholly -lost, and we should have a case of complete abortion. The principle, also, of -economy, explained in a former chapter, by which the materials forming any part -or structure, if not useful to the possessor, will be saved as far as is -possible, will probably often come into play; and this will tend to cause the -entire obliteration of a rudimentary organ. - -As the presence of rudimentary organs is thus due to the tendency in every part -of the organisation, which has long existed, to be inherited—we can understand, -on the genealogical view of classification, how it is that systematists have -found rudimentary parts as useful as, or even sometimes more useful than, parts -of high physiological importance. Rudimentary organs may be compared with the -letters in a word, still retained in the spelling, but become useless in the -pronunciation, but which serve as a clue in seeking for its derivation. On the -view of descent with modification, we may conclude that the existence of organs -in a rudimentary, imperfect, and useless condition, or quite aborted, far from -presenting a strange difficulty, as they assuredly do on the ordinary doctrine -of creation, might even have been anticipated, and can be accounted for by the -laws of inheritance. - -Summary.—In this chapter I have attempted to show, that the subordination of -group to group in all organisms throughout all time; that the nature of the -relationship, by which all living and extinct beings are united by complex, -radiating, and circuitous lines of affinities into one grand system; the rules -followed and the difficulties encountered by naturalists in their -classifications; the value set upon characters, if constant and prevalent, -whether of high vital importance, or of the most trifling importance, or, as in -rudimentary organs, of no importance; the wide opposition in value between -analogical or adaptive characters, and characters of true affinity; and other -such rules;—all naturally follow on the view of the common parentage of those -forms which are considered by naturalists as allied, together with their -modification through natural selection, with its contingencies of extinction -and divergence of character. In considering this view of classification, it -should be borne in mind that the element of descent has been universally used -in ranking together the sexes, ages, and acknowledged varieties of the same -species, however different they may be in structure. If we extend the use of -this element of descent,—the only certainly known cause of similarity in -organic beings,—we shall understand what is meant by the natural system: it is +undergo abrupt changes. I believe that disuse has been the main agency; +that it has led in successive generations to the gradual reduction of +various organs, until they have become rudimentary,—as in the case of +the eyes of animals inhabiting dark caverns, and of the wings of birds +inhabiting oceanic islands, which have seldom been forced to take +flight, and have ultimately lost the power of flying. Again, an organ +useful under certain conditions, might become injurious under others, as +with the wings of beetles living on small and exposed islands; and in +this case natural selection would continue slowly to reduce the organ, +until it was rendered harmless and rudimentary. + +Any change in function, which can be effected by insensibly small steps, +is within the power of natural selection; so that an organ rendered, +during changed habits of life, useless or injurious for one purpose, +might easily be modified and used for another purpose. Or an organ might +be retained for one alone of its former functions. An organ, when +rendered useless, may well be variable, for its variations cannot be +checked by natural selection. At whatever period of life disuse or +selection reduces an organ, and this will generally be when the being +has come to maturity and to its full powers of action, the principle of +inheritance at corresponding ages will reproduce the organ in its +reduced state at the same age, and consequently will seldom affect or +reduce it in the embryo. Thus we can understand the greater relative +size of rudimentary organs in the embryo, and their lesser relative size +in the adult. But if each step of the process of reduction were to be +inherited, not at the corresponding age, but at an extremely early +period of life (as we have good reason to believe to be possible) the +rudimentary part would tend to be wholly lost, and we should have a case +of complete abortion. The principle, also, of economy, explained in a +former chapter, by which the materials forming any part or structure, if +not useful to the possessor, will be saved as far as is possible, will +probably often come into play; and this will tend to cause the entire +obliteration of a rudimentary organ. + +As the presence of rudimentary organs is thus due to the tendency in +every part of the organisation, which has long existed, to be +inherited—we can understand, on the genealogical view of classification, +how it is that systematists have found rudimentary parts as useful as, +or even sometimes more useful than, parts of high physiological +importance. Rudimentary organs may be compared with the letters in a +word, still retained in the spelling, but become useless in the +pronunciation, but which serve as a clue in seeking for its derivation. +On the view of descent with modification, we may conclude that the +existence of organs in a rudimentary, imperfect, and useless condition, +or quite aborted, far from presenting a strange difficulty, as they +assuredly do on the ordinary doctrine of creation, might even have been +anticipated, and can be accounted for by the laws of inheritance. + +Summary.—In this chapter I have attempted to show, that the +subordination of group to group in all organisms throughout all time; +that the nature of the relationship, by which all living and extinct +beings are united by complex, radiating, and circuitous lines of +affinities into one grand system; the rules followed and the +difficulties encountered by naturalists in their classifications; the +value set upon characters, if constant and prevalent, whether of high +vital importance, or of the most trifling importance, or, as in +rudimentary organs, of no importance; the wide opposition in value +between analogical or adaptive characters, and characters of true +affinity; and other such rules;—all naturally follow on the view of the +common parentage of those forms which are considered by naturalists as +allied, together with their modification through natural selection, with +its contingencies of extinction and divergence of character. In +considering this view of classification, it should be borne in mind that +the element of descent has been universally used in ranking together the +sexes, ages, and acknowledged varieties of the same species, however +different they may be in structure. If we extend the use of this element +of descent,—the only certainly known cause of similarity in organic +beings,—we shall understand what is meant by the natural system: it is genealogical in its attempted arrangement, with the grades of acquired -difference marked by the terms varieties, species, genera, families, orders, -and classes. +difference marked by the terms varieties, species, genera, families, +orders, and classes. On this same view of descent with modification, all the great facts in -Morphology become intelligible,—whether we look to the same pattern displayed -in the homologous organs, to whatever purpose applied, of the different species -of a class; or to the homologous parts constructed on the same pattern in each -individual animal and plant. - -On the principle of successive slight variations, not necessarily or generally -supervening at a very early period of life, and being inherited at a -corresponding period, we can understand the great leading facts in Embryology; -namely, the resemblance in an individual embryo of the homologous parts, which -when matured will become widely different from each other in structure and -function; and the resemblance in different species of a class of the homologous -parts or organs, though fitted in the adult members for purposes as different -as possible. Larvæ are active embryos, which have become specially modified in -relation to their habits of life, through the principle of modifications being -inherited at corresponding ages. On this same principle—and bearing in mind, -that when organs are reduced in size, either from disuse or selection, it will -generally be at that period of life when the being has to provide for its own -wants, and bearing in mind how strong is the principle of inheritance—the -occurrence of rudimentary organs and their final abortion, present to us no -inexplicable difficulties; on the contrary, their presence might have been even -anticipated. The importance of embryological characters and of rudimentary -organs in classification is intelligible, on the view that an arrangement is -only so far natural as it is genealogical. +Morphology become intelligible,—whether we look to the same pattern +displayed in the homologous organs, to whatever purpose applied, of the +different species of a class; or to the homologous parts constructed on +the same pattern in each individual animal and plant. + +On the principle of successive slight variations, not necessarily or +generally supervening at a very early period of life, and being +inherited at a corresponding period, we can understand the great leading +facts in Embryology; namely, the resemblance in an individual embryo of +the homologous parts, which when matured will become widely different +from each other in structure and function; and the resemblance in +different species of a class of the homologous parts or organs, though +fitted in the adult members for purposes as different as possible. Larvæ +are active embryos, which have become specially modified in relation to +their habits of life, through the principle of modifications being +inherited at corresponding ages. On this same principle—and bearing in +mind, that when organs are reduced in size, either from disuse or +selection, it will generally be at that period of life when the being +has to provide for its own wants, and bearing in mind how strong is the +principle of inheritance—the occurrence of rudimentary organs and their +final abortion, present to us no inexplicable difficulties; on the +contrary, their presence might have been even anticipated. The +importance of embryological characters and of rudimentary organs in +classification is intelligible, on the view that an arrangement is only +so far natural as it is genealogical. Finally, the several classes of facts which have been considered in this -chapter, seem to me to proclaim so plainly, that the innumerable species, -genera, and families of organic beings, with which this world is peopled, have -all descended, each within its own class or group, from common parents, and -have all been modified in the course of descent, that I should without -hesitation adopt this view, even if it were unsupported by other facts or -arguments. +chapter, seem to me to proclaim so plainly, that the innumerable +species, genera, and families of organic beings, with which this world +is peopled, have all descended, each within its own class or group, from +common parents, and have all been modified in the course of descent, +that I should without hesitation adopt this view, even if it were +unsupported by other facts or arguments. -CHAPTER XIV. -RECAPITULATION AND CONCLUSION. +CHAPTER XIV. RECAPITULATION AND CONCLUSION. Recapitulation of the difficulties on the theory of Natural Selection. -Recapitulation of the general and special circumstances in its favour. Causes -of the general belief in the immutability of species. How far the theory of -natural selection may be extended. Effects of its adoption on the study of -Natural history. Concluding remarks. - -As this whole volume is one long argument, it may be convenient to the reader -to have the leading facts and inferences briefly recapitulated. - -That many and grave objections may be advanced against the theory of descent -with modification through natural selection, I do not deny. I have endeavoured -to give to them their full force. Nothing at first can appear more difficult to -believe than that the more complex organs and instincts should have been -perfected, not by means superior to, though analogous with, human reason, but -by the accumulation of innumerable slight variations, each good for the -individual possessor. Nevertheless, this difficulty, though appearing to our -imagination insuperably great, cannot be considered real if we admit the -following propositions, namely,—that gradations in the perfection of any organ -or instinct, which we may consider, either do now exist or could have existed, -each good of its kind,—that all organs and instincts are, in ever so slight a -degree, variable,—and, lastly, that there is a struggle for existence leading -to the preservation of each profitable deviation of structure or instinct. The -truth of these propositions cannot, I think, be disputed. - -It is, no doubt, extremely difficult even to conjecture by what gradations many -structures have been perfected, more especially amongst broken and failing -groups of organic beings; but we see so many strange gradations in nature, as -is proclaimed by the canon, “Natura non facit saltum,” that we ought to be -extremely cautious in saying that any organ or instinct, or any whole being, -could not have arrived at its present state by many graduated steps. There are, -it must be admitted, cases of special difficulty on the theory of natural -selection; and one of the most curious of these is the existence of two or -three defined castes of workers or sterile females in the same community of -ants; but I have attempted to show how this difficulty can be mastered. - -With respect to the almost universal sterility of species when first crossed, -which forms so remarkable a contrast with the almost universal fertility of -varieties when crossed, I must refer the reader to the recapitulation of the -facts given at the end of the eighth chapter, which seem to me conclusively to -show that this sterility is no more a special endowment than is the incapacity -of two trees to be grafted together, but that it is incidental on -constitutional differences in the reproductive systems of the intercrossed -species. We see the truth of this conclusion in the vast difference in the -result, when the same two species are crossed reciprocally; that is, when one -species is first used as the father and then as the mother. - -The fertility of varieties when intercrossed and of their mongrel offspring -cannot be considered as universal; nor is their very general fertility -surprising when we remember that it is not likely that either their -constitutions or their reproductive systems should have been profoundly -modified. Moreover, most of the varieties which have been experimentised on -have been produced under domestication; and as domestication apparently tends -to eliminate sterility, we ought not to expect it also to produce sterility. - -The sterility of hybrids is a very different case from that of first crosses, -for their reproductive organs are more or less functionally impotent; whereas -in first crosses the organs on both sides are in a perfect condition. As we -continually see that organisms of all kinds are rendered in some degree sterile -from their constitutions having been disturbed by slightly different and new -conditions of life, we need not feel surprise at hybrids being in some degree -sterile, for their constitutions can hardly fail to have been disturbed from -being compounded of two distinct organisations. This parallelism is supported -by another parallel, but directly opposite, class of facts; namely, that the -vigour and fertility of all organic beings are increased by slight changes in -their conditions of life, and that the offspring of slightly modified forms or -varieties acquire from being crossed increased vigour and fertility. So that, -on the one hand, considerable changes in the conditions of life and crosses -between greatly modified forms, lessen fertility; and on the other hand, lesser -changes in the conditions of life and crosses between less modified forms, -increase fertility. - -Turning to geographical distribution, the difficulties encountered on the -theory of descent with modification are grave enough. All the individuals of -the same species, and all the species of the same genus, or even higher group, -must have descended from common parents; and therefore, in however distant and -isolated parts of the world they are now found, they must in the course of -successive generations have passed from some one part to the others. We are -often wholly unable even to conjecture how this could have been effected. Yet, -as we have reason to believe that some species have retained the same specific -form for very long periods, enormously long as measured by years, too much -stress ought not to be laid on the occasional wide diffusion of the same -species; for during very long periods of time there will always be a good -chance for wide migration by many means. A broken or interrupted range may -often be accounted for by the extinction of the species in the intermediate -regions. It cannot be denied that we are as yet very ignorant of the full -extent of the various climatal and geographical changes which have affected the -earth during modern periods; and such changes will obviously have greatly -facilitated migration. As an example, I have attempted to show how potent has -been the influence of the Glacial period on the distribution both of the same -and of representative species throughout the world. We are as yet profoundly -ignorant of the many occasional means of transport. With respect to distinct -species of the same genus inhabiting very distant and isolated regions, as the -process of modification has necessarily been slow, all the means of migration -will have been possible during a very long period; and consequently the -difficulty of the wide diffusion of species of the same genus is in some degree -lessened. - -As on the theory of natural selection an interminable number of intermediate -forms must have existed, linking together all the species in each group by -gradations as fine as our present varieties, it may be asked, Why do we not see -these linking forms all around us? Why are not all organic beings blended -together in an inextricable chaos? With respect to existing forms, we should -remember that we have no right to expect (excepting in rare cases) to discover -directly connecting links between them, but only between each and some extinct -and supplanted form. Even on a wide area, which has during a long period -remained continuous, and of which the climate and other conditions of life -change insensibly in going from a district occupied by one species into another -district occupied by a closely allied species, we have no just right to expect -often to find intermediate varieties in the intermediate zone. For we have -reason to believe that only a few species are undergoing change at any one -period; and all changes are slowly effected. I have also shown that the -intermediate varieties which will at first probably exist in the intermediate -zones, will be liable to be supplanted by the allied forms on either hand; and -the latter, from existing in greater numbers, will generally be modified and -improved at a quicker rate than the intermediate varieties, which exist in -lesser numbers; so that the intermediate varieties will, in the long run, be -supplanted and exterminated. - -On this doctrine of the extermination of an infinitude of connecting links, -between the living and extinct inhabitants of the world, and at each successive -period between the extinct and still older species, why is not every geological -formation charged with such links? Why does not every collection of fossil -remains afford plain evidence of the gradation and mutation of the forms of -life? We meet with no such evidence, and this is the most obvious and forcible -of the many objections which may be urged against my theory. Why, again, do -whole groups of allied species appear, though certainly they often falsely -appear, to have come in suddenly on the several geological stages? Why do we -not find great piles of strata beneath the Silurian system, stored with the -remains of the progenitors of the Silurian groups of fossils? For certainly on -my theory such strata must somewhere have been deposited at these ancient and -utterly unknown epochs in the world’s history. - -I can answer these questions and grave objections only on the supposition that -the geological record is far more imperfect than most geologists believe. It -cannot be objected that there has not been time sufficient for any amount of -organic change; for the lapse of time has been so great as to be utterly -inappreciable by the human intellect. The number of specimens in all our -museums is absolutely as nothing compared with the countless generations of -countless species which certainly have existed. We should not be able to -recognise a species as the parent of any one or more species if we were to -examine them ever so closely, unless we likewise possessed many of the -intermediate links between their past or parent and present states; and these -many links we could hardly ever expect to discover, owing to the imperfection -of the geological record. Numerous existing doubtful forms could be named which -are probably varieties; but who will pretend that in future ages so many fossil -links will be discovered, that naturalists will be able to decide, on the -common view, whether or not these doubtful forms are varieties? As long as most -of the links between any two species are unknown, if any one link or -intermediate variety be discovered, it will simply be classed as another and -distinct species. Only a small portion of the world has been geologically -explored. Only organic beings of certain classes can be preserved in a fossil -condition, at least in any great number. Widely ranging species vary most, and -varieties are often at first local,—both causes rendering the discovery of -intermediate links less likely. Local varieties will not spread into other and -distant regions until they are considerably modified and improved; and when -they do spread, if discovered in a geological formation, they will appear as if -suddenly created there, and will be simply classed as new species. Most -formations have been intermittent in their accumulation; and their duration, I -am inclined to believe, has been shorter than the average duration of specific -forms. Successive formations are separated from each other by enormous blank -intervals of time; for fossiliferous formations, thick enough to resist future -degradation, can be accumulated only where much sediment is deposited on the -subsiding bed of the sea. During the alternate periods of elevation and of -stationary level the record will be blank. During these latter periods there -will probably be more variability in the forms of life; during periods of +Recapitulation of the general and special circumstances in its favour. +Causes of the general belief in the immutability of species. How far the +theory of natural selection may be extended. Effects of its adoption on +the study of Natural history. Concluding remarks. + +As this whole volume is one long argument, it may be convenient to the +reader to have the leading facts and inferences briefly recapitulated. + +That many and grave objections may be advanced against the theory of +descent with modification through natural selection, I do not deny. I +have endeavoured to give to them their full force. Nothing at first can +appear more difficult to believe than that the more complex organs and +instincts should have been perfected, not by means superior to, though +analogous with, human reason, but by the accumulation of innumerable +slight variations, each good for the individual possessor. Nevertheless, +this difficulty, though appearing to our imagination insuperably great, +cannot be considered real if we admit the following propositions, +namely,—that gradations in the perfection of any organ or instinct, +which we may consider, either do now exist or could have existed, each +good of its kind,—that all organs and instincts are, in ever so slight a +degree, variable,—and, lastly, that there is a struggle for existence +leading to the preservation of each profitable deviation of structure or +instinct. The truth of these propositions cannot, I think, be disputed. + +It is, no doubt, extremely difficult even to conjecture by what +gradations many structures have been perfected, more especially amongst +broken and failing groups of organic beings; but we see so many strange +gradations in nature, as is proclaimed by the canon, “Natura non facit +saltum,” that we ought to be extremely cautious in saying that any organ +or instinct, or any whole being, could not have arrived at its present +state by many graduated steps. There are, it must be admitted, cases of +special difficulty on the theory of natural selection; and one of the +most curious of these is the existence of two or three defined castes of +workers or sterile females in the same community of ants; but I have +attempted to show how this difficulty can be mastered. + +With respect to the almost universal sterility of species when first +crossed, which forms so remarkable a contrast with the almost universal +fertility of varieties when crossed, I must refer the reader to the +recapitulation of the facts given at the end of the eighth chapter, +which seem to me conclusively to show that this sterility is no more a +special endowment than is the incapacity of two trees to be grafted +together, but that it is incidental on constitutional differences in the +reproductive systems of the intercrossed species. We see the truth of +this conclusion in the vast difference in the result, when the same two +species are crossed reciprocally; that is, when one species is first +used as the father and then as the mother. + +The fertility of varieties when intercrossed and of their mongrel +offspring cannot be considered as universal; nor is their very general +fertility surprising when we remember that it is not likely that either +their constitutions or their reproductive systems should have been +profoundly modified. Moreover, most of the varieties which have been +experimentised on have been produced under domestication; and as +domestication apparently tends to eliminate sterility, we ought not to +expect it also to produce sterility. + +The sterility of hybrids is a very different case from that of first +crosses, for their reproductive organs are more or less functionally +impotent; whereas in first crosses the organs on both sides are in a +perfect condition. As we continually see that organisms of all kinds are +rendered in some degree sterile from their constitutions having been +disturbed by slightly different and new conditions of life, we need not +feel surprise at hybrids being in some degree sterile, for their +constitutions can hardly fail to have been disturbed from being +compounded of two distinct organisations. This parallelism is supported +by another parallel, but directly opposite, class of facts; namely, that +the vigour and fertility of all organic beings are increased by slight +changes in their conditions of life, and that the offspring of slightly +modified forms or varieties acquire from being crossed increased vigour +and fertility. So that, on the one hand, considerable changes in the +conditions of life and crosses between greatly modified forms, lessen +fertility; and on the other hand, lesser changes in the conditions of +life and crosses between less modified forms, increase fertility. + +Turning to geographical distribution, the difficulties encountered on +the theory of descent with modification are grave enough. All the +individuals of the same species, and all the species of the same genus, +or even higher group, must have descended from common parents; and +therefore, in however distant and isolated parts of the world they are +now found, they must in the course of successive generations have passed +from some one part to the others. We are often wholly unable even to +conjecture how this could have been effected. Yet, as we have reason to +believe that some species have retained the same specific form for very +long periods, enormously long as measured by years, too much stress +ought not to be laid on the occasional wide diffusion of the same +species; for during very long periods of time there will always be a +good chance for wide migration by many means. A broken or interrupted +range may often be accounted for by the extinction of the species in the +intermediate regions. It cannot be denied that we are as yet very +ignorant of the full extent of the various climatal and geographical +changes which have affected the earth during modern periods; and such +changes will obviously have greatly facilitated migration. As an +example, I have attempted to show how potent has been the influence of +the Glacial period on the distribution both of the same and of +representative species throughout the world. We are as yet profoundly +ignorant of the many occasional means of transport. With respect to +distinct species of the same genus inhabiting very distant and isolated +regions, as the process of modification has necessarily been slow, all +the means of migration will have been possible during a very long +period; and consequently the difficulty of the wide diffusion of species +of the same genus is in some degree lessened. + +As on the theory of natural selection an interminable number of +intermediate forms must have existed, linking together all the species +in each group by gradations as fine as our present varieties, it may be +asked, Why do we not see these linking forms all around us? Why are not +all organic beings blended together in an inextricable chaos? With +respect to existing forms, we should remember that we have no right to +expect (excepting in rare cases) to discover directly connecting links +between them, but only between each and some extinct and supplanted +form. Even on a wide area, which has during a long period remained +continuous, and of which the climate and other conditions of life change +insensibly in going from a district occupied by one species into another +district occupied by a closely allied species, we have no just right to +expect often to find intermediate varieties in the intermediate zone. +For we have reason to believe that only a few species are undergoing +change at any one period; and all changes are slowly effected. I have +also shown that the intermediate varieties which will at first probably +exist in the intermediate zones, will be liable to be supplanted by the +allied forms on either hand; and the latter, from existing in greater +numbers, will generally be modified and improved at a quicker rate than +the intermediate varieties, which exist in lesser numbers; so that the +intermediate varieties will, in the long run, be supplanted and +exterminated. + +On this doctrine of the extermination of an infinitude of connecting +links, between the living and extinct inhabitants of the world, and at +each successive period between the extinct and still older species, why +is not every geological formation charged with such links? Why does not +every collection of fossil remains afford plain evidence of the +gradation and mutation of the forms of life? We meet with no such +evidence, and this is the most obvious and forcible of the many +objections which may be urged against my theory. Why, again, do whole +groups of allied species appear, though certainly they often falsely +appear, to have come in suddenly on the several geological stages? Why +do we not find great piles of strata beneath the Silurian system, stored +with the remains of the progenitors of the Silurian groups of fossils? +For certainly on my theory such strata must somewhere have been +deposited at these ancient and utterly unknown epochs in the world’s +history. + +I can answer these questions and grave objections only on the +supposition that the geological record is far more imperfect than most +geologists believe. It cannot be objected that there has not been time +sufficient for any amount of organic change; for the lapse of time has +been so great as to be utterly inappreciable by the human intellect. The +number of specimens in all our museums is absolutely as nothing compared +with the countless generations of countless species which certainly have +existed. We should not be able to recognise a species as the parent of +any one or more species if we were to examine them ever so closely, +unless we likewise possessed many of the intermediate links between +their past or parent and present states; and these many links we could +hardly ever expect to discover, owing to the imperfection of the +geological record. Numerous existing doubtful forms could be named which +are probably varieties; but who will pretend that in future ages so many +fossil links will be discovered, that naturalists will be able to +decide, on the common view, whether or not these doubtful forms are +varieties? As long as most of the links between any two species are +unknown, if any one link or intermediate variety be discovered, it will +simply be classed as another and distinct species. Only a small portion +of the world has been geologically explored. Only organic beings of +certain classes can be preserved in a fossil condition, at least in any +great number. Widely ranging species vary most, and varieties are often +at first local,—both causes rendering the discovery of intermediate +links less likely. Local varieties will not spread into other and +distant regions until they are considerably modified and improved; and +when they do spread, if discovered in a geological formation, they will +appear as if suddenly created there, and will be simply classed as new +species. Most formations have been intermittent in their accumulation; +and their duration, I am inclined to believe, has been shorter than the +average duration of specific forms. Successive formations are separated +from each other by enormous blank intervals of time; for fossiliferous +formations, thick enough to resist future degradation, can be +accumulated only where much sediment is deposited on the subsiding bed +of the sea. During the alternate periods of elevation and of stationary +level the record will be blank. During these latter periods there will +probably be more variability in the forms of life; during periods of subsidence, more extinction. -With respect to the absence of fossiliferous formations beneath the lowest -Silurian strata, I can only recur to the hypothesis given in the ninth chapter. -That the geological record is imperfect all will admit; but that it is -imperfect to the degree which I require, few will be inclined to admit. If we -look to long enough intervals of time, geology plainly declares that all -species have changed; and they have changed in the manner which my theory -requires, for they have changed slowly and in a graduated manner. We clearly -see this in the fossil remains from consecutive formations invariably being -much more closely related to each other, than are the fossils from formations -distant from each other in time. - -Such is the sum of the several chief objections and difficulties which may -justly be urged against my theory; and I have now briefly recapitulated the -answers and explanations which can be given to them. I have felt these -difficulties far too heavily during many years to doubt their weight. But it -deserves especial notice that the more important objections relate to questions -on which we are confessedly ignorant; nor do we know how ignorant we are. We do -not know all the possible transitional gradations between the simplest and the -most perfect organs; it cannot be pretended that we know all the varied means -of Distribution during the long lapse of years, or that we know how imperfect -the Geological Record is. Grave as these several difficulties are, in my -judgment they do not overthrow the theory of descent with modification. - -Now let us turn to the other side of the argument. Under domestication we see -much variability. This seems to be mainly due to the reproductive system being -eminently susceptible to changes in the conditions of life; so that this -system, when not rendered impotent, fails to reproduce offspring exactly like -the parent-form. Variability is governed by many complex laws,—by correlation -of growth, by use and disuse, and by the direct action of the physical -conditions of life. There is much difficulty in ascertaining how much -modification our domestic productions have undergone; but we may safely infer -that the amount has been large, and that modifications can be inherited for -long periods. As long as the conditions of life remain the same, we have reason -to believe that a modification, which has already been inherited for many -generations, may continue to be inherited for an almost infinite number of -generations. On the other hand we have evidence that variability, when it has -once come into play, does not wholly cease; for new varieties are still -occasionally produced by our most anciently domesticated productions. - -Man does not actually produce variability; he only unintentionally exposes -organic beings to new conditions of life, and then nature acts on the -organisation, and causes variability. But man can and does select the -variations given to him by nature, and thus accumulate them in any desired -manner. He thus adapts animals and plants for his own benefit or pleasure. He -may do this methodically, or he may do it unconsciously by preserving the -individuals most useful to him at the time, without any thought of altering the -breed. It is certain that he can largely influence the character of a breed by -selecting, in each successive generation, individual differences so slight as -to be quite inappreciable by an uneducated eye. This process of selection has -been the great agency in the production of the most distinct and useful -domestic breeds. That many of the breeds produced by man have to a large extent -the character of natural species, is shown by the inextricable doubts whether -very many of them are varieties or aboriginal species. - -There is no obvious reason why the principles which have acted so efficiently -under domestication should not have acted under nature. In the preservation of -favoured individuals and races, during the constantly-recurrent Struggle for -Existence, we see the most powerful and ever-acting means of selection. The -struggle for existence inevitably follows from the high geometrical ratio of -increase which is common to all organic beings. This high rate of increase is -proved by calculation, by the effects of a succession of peculiar seasons, and -by the results of naturalisation, as explained in the third chapter. More -individuals are born than can possibly survive. A grain in the balance will -determine which individual shall live and which shall die,—which variety or -species shall increase in number, and which shall decrease, or finally become -extinct. As the individuals of the same species come in all respects into the -closest competition with each other, the struggle will generally be most severe -between them; it will be almost equally severe between the varieties of the -same species, and next in severity between the species of the same genus. But -the struggle will often be very severe between beings most remote in the scale -of nature. The slightest advantage in one being, at any age or during any -season, over those with which it comes into competition, or better adaptation -in however slight a degree to the surrounding physical conditions, will turn -the balance. - -With animals having separated sexes there will in most cases be a struggle -between the males for possession of the females. The most vigorous individuals, -or those which have most successfully struggled with their conditions of life, -will generally leave most progeny. But success will often depend on having -special weapons or means of defence, or on the charms of the males; and the -slightest advantage will lead to victory. +With respect to the absence of fossiliferous formations beneath the +lowest Silurian strata, I can only recur to the hypothesis given in the +ninth chapter. That the geological record is imperfect all will admit; +but that it is imperfect to the degree which I require, few will be +inclined to admit. If we look to long enough intervals of time, geology +plainly declares that all species have changed; and they have changed in +the manner which my theory requires, for they have changed slowly and in +a graduated manner. We clearly see this in the fossil remains from +consecutive formations invariably being much more closely related to +each other, than are the fossils from formations distant from each other +in time. + +Such is the sum of the several chief objections and difficulties which +may justly be urged against my theory; and I have now briefly +recapitulated the answers and explanations which can be given to them. I +have felt these difficulties far too heavily during many years to doubt +their weight. But it deserves especial notice that the more important +objections relate to questions on which we are confessedly ignorant; nor +do we know how ignorant we are. We do not know all the possible +transitional gradations between the simplest and the most perfect +organs; it cannot be pretended that we know all the varied means of +Distribution during the long lapse of years, or that we know how +imperfect the Geological Record is. Grave as these several difficulties +are, in my judgment they do not overthrow the theory of descent with +modification. -As geology plainly proclaims that each land has undergone great physical -changes, we might have expected that organic beings would have varied under -nature, in the same way as they generally have varied under the changed -conditions of domestication. And if there be any variability under nature, it -would be an unaccountable fact if natural selection had not come into play. It -has often been asserted, but the assertion is quite incapable of proof, that -the amount of variation under nature is a strictly limited quantity. Man, -though acting on external characters alone and often capriciously, can produce -within a short period a great result by adding up mere individual differences -in his domestic productions; and every one admits that there are at least -individual differences in species under nature. But, besides such differences, -all naturalists have admitted the existence of varieties, which they think -sufficiently distinct to be worthy of record in systematic works. No one can -draw any clear distinction between individual differences and slight varieties; -or between more plainly marked varieties and sub-species, and species. Let it -be observed how naturalists differ in the rank which they assign to the many -representative forms in Europe and North America. - -If then we have under nature variability and a powerful agent always ready to -act and select, why should we doubt that variations in any way useful to -beings, under their excessively complex relations of life, would be preserved, -accumulated, and inherited? Why, if man can by patience select variations most -useful to himself, should nature fail in selecting variations useful, under -changing conditions of life, to her living products? What limit can be put to -this power, acting during long ages and rigidly scrutinising the whole -constitution, structure, and habits of each creature,—favouring the good and -rejecting the bad? I can see no limit to this power, in slowly and beautifully -adapting each form to the most complex relations of life. The theory of natural -selection, even if we looked no further than this, seems to me to be in itself -probable. I have already recapitulated, as fairly as I could, the opposed -difficulties and objections: now let us turn to the special facts and arguments -in favour of the theory. - -On the view that species are only strongly marked and permanent varieties, and -that each species first existed as a variety, we can see why it is that no line -of demarcation can be drawn between species, commonly supposed to have been -produced by special acts of creation, and varieties which are acknowledged to -have been produced by secondary laws. On this same view we can understand how -it is that in each region where many species of a genus have been produced, and -where they now flourish, these same species should present many varieties; for -where the manufactory of species has been active, we might expect, as a general -rule, to find it still in action; and this is the case if varieties be -incipient species. Moreover, the species of the larger genera, which afford the -greater number of varieties or incipient species, retain to a certain degree -the character of varieties; for they differ from each other by a less amount of -difference than do the species of smaller genera. The closely allied species -also of the larger genera apparently have restricted ranges, and they are -clustered in little groups round other species—in which respects they resemble -varieties. These are strange relations on the view of each species having been -independently created, but are intelligible if all species first existed as -varieties. +Now let us turn to the other side of the argument. Under domestication +we see much variability. This seems to be mainly due to the reproductive +system being eminently susceptible to changes in the conditions of life; +so that this system, when not rendered impotent, fails to reproduce +offspring exactly like the parent-form. Variability is governed by many +complex laws,—by correlation of growth, by use and disuse, and by the +direct action of the physical conditions of life. There is much +difficulty in ascertaining how much modification our domestic +productions have undergone; but we may safely infer that the amount has +been large, and that modifications can be inherited for long periods. As +long as the conditions of life remain the same, we have reason to +believe that a modification, which has already been inherited for many +generations, may continue to be inherited for an almost infinite number +of generations. On the other hand we have evidence that variability, +when it has once come into play, does not wholly cease; for new +varieties are still occasionally produced by our most anciently +domesticated productions. + +Man does not actually produce variability; he only unintentionally +exposes organic beings to new conditions of life, and then nature acts +on the organisation, and causes variability. But man can and does select +the variations given to him by nature, and thus accumulate them in any +desired manner. He thus adapts animals and plants for his own benefit or +pleasure. He may do this methodically, or he may do it unconsciously by +preserving the individuals most useful to him at the time, without any +thought of altering the breed. It is certain that he can largely +influence the character of a breed by selecting, in each successive +generation, individual differences so slight as to be quite +inappreciable by an uneducated eye. This process of selection has been +the great agency in the production of the most distinct and useful +domestic breeds. That many of the breeds produced by man have to a large +extent the character of natural species, is shown by the inextricable +doubts whether very many of them are varieties or aboriginal species. + +There is no obvious reason why the principles which have acted so +efficiently under domestication should not have acted under nature. In +the preservation of favoured individuals and races, during the +constantly-recurrent Struggle for Existence, we see the most powerful +and ever-acting means of selection. The struggle for existence +inevitably follows from the high geometrical ratio of increase which is +common to all organic beings. This high rate of increase is proved by +calculation, by the effects of a succession of peculiar seasons, and by +the results of naturalisation, as explained in the third chapter. More +individuals are born than can possibly survive. A grain in the balance +will determine which individual shall live and which shall die,—which +variety or species shall increase in number, and which shall decrease, +or finally become extinct. As the individuals of the same species come +in all respects into the closest competition with each other, the +struggle will generally be most severe between them; it will be almost +equally severe between the varieties of the same species, and next in +severity between the species of the same genus. But the struggle will +often be very severe between beings most remote in the scale of nature. +The slightest advantage in one being, at any age or during any season, +over those with which it comes into competition, or better adaptation in +however slight a degree to the surrounding physical conditions, will +turn the balance. + +With animals having separated sexes there will in most cases be a +struggle between the males for possession of the females. The most +vigorous individuals, or those which have most successfully struggled +with their conditions of life, will generally leave most progeny. But +success will often depend on having special weapons or means of defence, +or on the charms of the males; and the slightest advantage will lead to +victory. -As each species tends by its geometrical ratio of reproduction to increase -inordinately in number; and as the modified descendants of each species will be -enabled to increase by so much the more as they become more diversified in -habits and structure, so as to be enabled to seize on many and widely different -places in the economy of nature, there will be a constant tendency in natural -selection to preserve the most divergent offspring of any one species. Hence -during a long-continued course of modification, the slight differences, -characteristic of varieties of the same species, tend to be augmented into the -greater differences characteristic of species of the same genus. New and -improved varieties will inevitably supplant and exterminate the older, less -improved and intermediate varieties; and thus species are rendered to a large -extent defined and distinct objects. Dominant species belonging to the larger -groups tend to give birth to new and dominant forms; so that each large group -tends to become still larger, and at the same time more divergent in character. -But as all groups cannot thus succeed in increasing in size, for the world -would not hold them, the more dominant groups beat the less dominant. This -tendency in the large groups to go on increasing in size and diverging in -character, together with the almost inevitable contingency of much extinction, -explains the arrangement of all the forms of life, in groups subordinate to -groups, all within a few great classes, which we now see everywhere around us, -and which has prevailed throughout all time. This grand fact of the grouping of -all organic beings seems to me utterly inexplicable on the theory of creation. - -As natural selection acts solely by accumulating slight, successive, favourable -variations, it can produce no great or sudden modification; it can act only by -very short and slow steps. Hence the canon of “Natura non facit saltum,” which -every fresh addition to our knowledge tends to make more strictly correct, is -on this theory simply intelligible. We can plainly see why nature is prodigal -in variety, though niggard in innovation. But why this should be a law of -nature if each species has been independently created, no man can explain. - -Many other facts are, as it seems to me, explicable on this theory. How strange -it is that a bird, under the form of woodpecker, should have been created to -prey on insects on the ground; that upland geese, which never or rarely swim, -should have been created with webbed feet; that a thrush should have been -created to dive and feed on sub-aquatic insects; and that a petrel should have -been created with habits and structure fitting it for the life of an auk or -grebe! and so on in endless other cases. But on the view of each species -constantly trying to increase in number, with natural selection always ready to -adapt the slowly varying descendants of each to any unoccupied or ill-occupied -place in nature, these facts cease to be strange, or perhaps might even have -been anticipated. - -As natural selection acts by competition, it adapts the inhabitants of each -country only in relation to the degree of perfection of their associates; so -that we need feel no surprise at the inhabitants of any one country, although -on the ordinary view supposed to have been specially created and adapted for -that country, being beaten and supplanted by the naturalised productions from -another land. Nor ought we to marvel if all the contrivances in nature be not, -as far as we can judge, absolutely perfect; and if some of them be abhorrent to -our ideas of fitness. We need not marvel at the sting of the bee causing the -bee’s own death; at drones being produced in such vast numbers for one single -act, and being then slaughtered by their sterile sisters; at the astonishing -waste of pollen by our fir-trees; at the instinctive hatred of the queen bee -for her own fertile daughters; at ichneumonidæ feeding within the live bodies -of caterpillars; and at other such cases. The wonder indeed is, on the theory -of natural selection, that more cases of the want of absolute perfection have -not been observed. - -The complex and little known laws governing variation are the same, as far as -we can see, with the laws which have governed the production of so-called -specific forms. In both cases physical conditions seem to have produced but -little direct effect; yet when varieties enter any zone, they occasionally -assume some of the characters of the species proper to that zone. In both -varieties and species, use and disuse seem to have produced some effect; for it -is difficult to resist this conclusion when we look, for instance, at the -logger-headed duck, which has wings incapable of flight, in nearly the same -condition as in the domestic duck; or when we look at the burrowing tucutucu, -which is occasionally blind, and then at certain moles, which are habitually -blind and have their eyes covered with skin; or when we look at the blind -animals inhabiting the dark caves of America and Europe. In both varieties and -species correlation of growth seems to have played a most important part, so -that when one part has been modified other parts are necessarily modified. In -both varieties and species reversions to long-lost characters occur. How -inexplicable on the theory of creation is the occasional appearance of stripes -on the shoulder and legs of the several species of the horse-genus and in their -hybrids! How simply is this fact explained if we believe that these species -have descended from a striped progenitor, in the same manner as the several -domestic breeds of pigeon have descended from the blue and barred rock-pigeon! - -On the ordinary view of each species having been independently created, why -should the specific characters, or those by which the species of the same genus -differ from each other, be more variable than the generic characters in which -they all agree? Why, for instance, should the colour of a flower be more likely -to vary in any one species of a genus, if the other species, supposed to have -been created independently, have differently coloured flowers, than if all the -species of the genus have the same coloured flowers? If species are only -well-marked varieties, of which the characters have become in a high degree -permanent, we can understand this fact; for they have already varied since they -branched off from a common progenitor in certain characters, by which they have -come to be specifically distinct from each other; and therefore these same -characters would be more likely still to be variable than the generic -characters which have been inherited without change for an enormous period. It -is inexplicable on the theory of creation why a part developed in a very -unusual manner in any one species of a genus, and therefore, as we may -naturally infer, of great importance to the species, should be eminently liable -to variation; but, on my view, this part has undergone, since the several -species branched off from a common progenitor, an unusual amount of variability -and modification, and therefore we might expect this part generally to be still -variable. But a part may be developed in the most unusual manner, like the wing -of a bat, and yet not be more variable than any other structure, if the part be -common to many subordinate forms, that is, if it has been inherited for a very -long period; for in this case it will have been rendered constant by -long-continued natural selection. - -Glancing at instincts, marvellous as some are, they offer no greater difficulty -than does corporeal structure on the theory of the natural selection of -successive, slight, but profitable modifications. We can thus understand why -nature moves by graduated steps in endowing different animals of the same class -with their several instincts. I have attempted to show how much light the -principle of gradation throws on the admirable architectural powers of the -hive-bee. Habit no doubt sometimes comes into play in modifying instincts; but -it certainly is not indispensable, as we see, in the case of neuter insects, -which leave no progeny to inherit the effects of long-continued habit. On the -view of all the species of the same genus having descended from a common -parent, and having inherited much in common, we can understand how it is that -allied species, when placed under considerably different conditions of life, -yet should follow nearly the same instincts; why the thrush of South America, -for instance, lines her nest with mud like our British species. On the view of -instincts having been slowly acquired through natural selection we need not -marvel at some instincts being apparently not perfect and liable to mistakes, -and at many instincts causing other animals to suffer. - -If species be only well-marked and permanent varieties, we can at once see why -their crossed offspring should follow the same complex laws in their degrees -and kinds of resemblance to their parents,—in being absorbed into each other by -successive crosses, and in other such points,—as do the crossed offspring of -acknowledged varieties. On the other hand, these would be strange facts if -species have been independently created, and varieties have been produced by -secondary laws. - -If we admit that the geological record is imperfect in an extreme degree, then -such facts as the record gives, support the theory of descent with -modification. New species have come on the stage slowly and at successive -intervals; and the amount of change, after equal intervals of time, is widely -different in different groups. The extinction of species and of whole groups of -species, which has played so conspicuous a part in the history of the organic -world, almost inevitably follows on the principle of natural selection; for old -forms will be supplanted by new and improved forms. Neither single species nor -groups of species reappear when the chain of ordinary generation has once been -broken. The gradual diffusion of dominant forms, with the slow modification of -their descendants, causes the forms of life, after long intervals of time, to -appear as if they had changed simultaneously throughout the world. The fact of -the fossil remains of each formation being in some degree intermediate in -character between the fossils in the formations above and below, is simply -explained by their intermediate position in the chain of descent. The grand -fact that all extinct organic beings belong to the same system with recent -beings, falling either into the same or into intermediate groups, follows from -the living and the extinct being the offspring of common parents. As the groups -which have descended from an ancient progenitor have generally diverged in -character, the progenitor with its early descendants will often be intermediate -in character in comparison with its later descendants; and thus we can see why -the more ancient a fossil is, the oftener it stands in some degree intermediate -between existing and allied groups. Recent forms are generally looked at as -being, in some vague sense, higher than ancient and extinct forms; and they are -in so far higher as the later and more improved forms have conquered the older -and less improved organic beings in the struggle for life. Lastly, the law of -the long endurance of allied forms on the same continent,—of marsupials in -Australia, of edentata in America, and other such cases,—is intelligible, for -within a confined country, the recent and the extinct will naturally be allied -by descent. - -Looking to geographical distribution, if we admit that there has been during -the long course of ages much migration from one part of the world to another, -owing to former climatal and geographical changes and to the many occasional -and unknown means of dispersal, then we can understand, on the theory of -descent with modification, most of the great leading facts in Distribution. We -can see why there should be so striking a parallelism in the distribution of -organic beings throughout space, and in their geological succession throughout -time; for in both cases the beings have been connected by the bond of ordinary -generation, and the means of modification have been the same. We see the full -meaning of the wonderful fact, which must have struck every traveller, namely, -that on the same continent, under the most diverse conditions, under heat and -cold, on mountain and lowland, on deserts and marshes, most of the inhabitants -within each great class are plainly related; for they will generally be -descendants of the same progenitors and early colonists. On this same principle -of former migration, combined in most cases with modification, we can -understand, by the aid of the Glacial period, the identity of some few plants, -and the close alliance of many others, on the most distant mountains, under the -most different climates; and likewise the close alliance of some of the -inhabitants of the sea in the northern and southern temperate zones, though -separated by the whole intertropical ocean. Although two areas may present the -same physical conditions of life, we need feel no surprise at their inhabitants -being widely different, if they have been for a long period completely -separated from each other; for as the relation of organism to organism is the -most important of all relations, and as the two areas will have received -colonists from some third source or from each other, at various periods and in -different proportions, the course of modification in the two areas will -inevitably be different. - -On this view of migration, with subsequent modification, we can see why oceanic -islands should be inhabited by few species, but of these, that many should be -peculiar. We can clearly see why those animals which cannot cross wide spaces -of ocean, as frogs and terrestrial mammals, should not inhabit oceanic islands; -and why, on the other hand, new and peculiar species of bats, which can -traverse the ocean, should so often be found on islands far distant from any -continent. Such facts as the presence of peculiar species of bats, and the -absence of all other mammals, on oceanic islands, are utterly inexplicable on -the theory of independent acts of creation. - -The existence of closely allied or representative species in any two areas, -implies, on the theory of descent with modification, that the same parents -formerly inhabited both areas; and we almost invariably find that wherever many -closely allied species inhabit two areas, some identical species common to both -still exist. Wherever many closely allied yet distinct species occur, many -doubtful forms and varieties of the same species likewise occur. It is a rule -of high generality that the inhabitants of each area are related to the -inhabitants of the nearest source whence immigrants might have been derived. We -see this in nearly all the plants and animals of the Galapagos archipelago, of -Juan Fernandez, and of the other American islands being related in the most +As geology plainly proclaims that each land has undergone great physical +changes, we might have expected that organic beings would have varied +under nature, in the same way as they generally have varied under the +changed conditions of domestication. And if there be any variability +under nature, it would be an unaccountable fact if natural selection had +not come into play. It has often been asserted, but the assertion is +quite incapable of proof, that the amount of variation under nature is a +strictly limited quantity. Man, though acting on external characters +alone and often capriciously, can produce within a short period a great +result by adding up mere individual differences in his domestic +productions; and every one admits that there are at least individual +differences in species under nature. But, besides such differences, all +naturalists have admitted the existence of varieties, which they think +sufficiently distinct to be worthy of record in systematic works. No one +can draw any clear distinction between individual differences and slight +varieties; or between more plainly marked varieties and sub-species, and +species. Let it be observed how naturalists differ in the rank which +they assign to the many representative forms in Europe and North +America. + +If then we have under nature variability and a powerful agent always +ready to act and select, why should we doubt that variations in any way +useful to beings, under their excessively complex relations of life, +would be preserved, accumulated, and inherited? Why, if man can by +patience select variations most useful to himself, should nature fail in +selecting variations useful, under changing conditions of life, to her +living products? What limit can be put to this power, acting during long +ages and rigidly scrutinising the whole constitution, structure, and +habits of each creature,—favouring the good and rejecting the bad? I can +see no limit to this power, in slowly and beautifully adapting each form +to the most complex relations of life. The theory of natural selection, +even if we looked no further than this, seems to me to be in itself +probable. I have already recapitulated, as fairly as I could, the +opposed difficulties and objections: now let us turn to the special +facts and arguments in favour of the theory. + +On the view that species are only strongly marked and permanent +varieties, and that each species first existed as a variety, we can see +why it is that no line of demarcation can be drawn between species, +commonly supposed to have been produced by special acts of creation, and +varieties which are acknowledged to have been produced by secondary +laws. On this same view we can understand how it is that in each region +where many species of a genus have been produced, and where they now +flourish, these same species should present many varieties; for where +the manufactory of species has been active, we might expect, as a +general rule, to find it still in action; and this is the case if +varieties be incipient species. Moreover, the species of the larger +genera, which afford the greater number of varieties or incipient +species, retain to a certain degree the character of varieties; for they +differ from each other by a less amount of difference than do the +species of smaller genera. The closely allied species also of the larger +genera apparently have restricted ranges, and they are clustered in +little groups round other species—in which respects they resemble +varieties. These are strange relations on the view of each species +having been independently created, but are intelligible if all species +first existed as varieties. + +As each species tends by its geometrical ratio of reproduction to +increase inordinately in number; and as the modified descendants of each +species will be enabled to increase by so much the more as they become +more diversified in habits and structure, so as to be enabled to seize +on many and widely different places in the economy of nature, there will +be a constant tendency in natural selection to preserve the most +divergent offspring of any one species. Hence during a long-continued +course of modification, the slight differences, characteristic of +varieties of the same species, tend to be augmented into the greater +differences characteristic of species of the same genus. New and +improved varieties will inevitably supplant and exterminate the older, +less improved and intermediate varieties; and thus species are rendered +to a large extent defined and distinct objects. Dominant species +belonging to the larger groups tend to give birth to new and dominant +forms; so that each large group tends to become still larger, and at the +same time more divergent in character. But as all groups cannot thus +succeed in increasing in size, for the world would not hold them, the +more dominant groups beat the less dominant. This tendency in the large +groups to go on increasing in size and diverging in character, together +with the almost inevitable contingency of much extinction, explains the +arrangement of all the forms of life, in groups subordinate to groups, +all within a few great classes, which we now see everywhere around us, +and which has prevailed throughout all time. This grand fact of the +grouping of all organic beings seems to me utterly inexplicable on the +theory of creation. + +As natural selection acts solely by accumulating slight, successive, +favourable variations, it can produce no great or sudden modification; +it can act only by very short and slow steps. Hence the canon of “Natura +non facit saltum,” which every fresh addition to our knowledge tends to +make more strictly correct, is on this theory simply intelligible. We +can plainly see why nature is prodigal in variety, though niggard in +innovation. But why this should be a law of nature if each species has +been independently created, no man can explain. + +Many other facts are, as it seems to me, explicable on this theory. How +strange it is that a bird, under the form of woodpecker, should have +been created to prey on insects on the ground; that upland geese, which +never or rarely swim, should have been created with webbed feet; that a +thrush should have been created to dive and feed on sub-aquatic insects; +and that a petrel should have been created with habits and structure +fitting it for the life of an auk or grebe! and so on in endless other +cases. But on the view of each species constantly trying to increase in +number, with natural selection always ready to adapt the slowly varying +descendants of each to any unoccupied or ill-occupied place in nature, +these facts cease to be strange, or perhaps might even have been +anticipated. + +As natural selection acts by competition, it adapts the inhabitants of +each country only in relation to the degree of perfection of their +associates; so that we need feel no surprise at the inhabitants of any +one country, although on the ordinary view supposed to have been +specially created and adapted for that country, being beaten and +supplanted by the naturalised productions from another land. Nor ought +we to marvel if all the contrivances in nature be not, as far as we can +judge, absolutely perfect; and if some of them be abhorrent to our ideas +of fitness. We need not marvel at the sting of the bee causing the bee’s +own death; at drones being produced in such vast numbers for one single +act, and being then slaughtered by their sterile sisters; at the +astonishing waste of pollen by our fir-trees; at the instinctive hatred +of the queen bee for her own fertile daughters; at ichneumonidæ feeding +within the live bodies of caterpillars; and at other such cases. The +wonder indeed is, on the theory of natural selection, that more cases of +the want of absolute perfection have not been observed. + +The complex and little known laws governing variation are the same, as +far as we can see, with the laws which have governed the production of +so-called specific forms. In both cases physical conditions seem to have +produced but little direct effect; yet when varieties enter any zone, +they occasionally assume some of the characters of the species proper to +that zone. In both varieties and species, use and disuse seem to have +produced some effect; for it is difficult to resist this conclusion when +we look, for instance, at the logger-headed duck, which has wings +incapable of flight, in nearly the same condition as in the domestic +duck; or when we look at the burrowing tucutucu, which is occasionally +blind, and then at certain moles, which are habitually blind and have +their eyes covered with skin; or when we look at the blind animals +inhabiting the dark caves of America and Europe. In both varieties and +species correlation of growth seems to have played a most important +part, so that when one part has been modified other parts are +necessarily modified. In both varieties and species reversions to +long-lost characters occur. How inexplicable on the theory of creation +is the occasional appearance of stripes on the shoulder and legs of the +several species of the horse-genus and in their hybrids! How simply is +this fact explained if we believe that these species have descended from +a striped progenitor, in the same manner as the several domestic breeds +of pigeon have descended from the blue and barred rock-pigeon! + +On the ordinary view of each species having been independently created, +why should the specific characters, or those by which the species of the +same genus differ from each other, be more variable than the generic +characters in which they all agree? Why, for instance, should the colour +of a flower be more likely to vary in any one species of a genus, if the +other species, supposed to have been created independently, have +differently coloured flowers, than if all the species of the genus have +the same coloured flowers? If species are only well-marked varieties, of +which the characters have become in a high degree permanent, we can +understand this fact; for they have already varied since they branched +off from a common progenitor in certain characters, by which they have +come to be specifically distinct from each other; and therefore these +same characters would be more likely still to be variable than the +generic characters which have been inherited without change for an +enormous period. It is inexplicable on the theory of creation why a part +developed in a very unusual manner in any one species of a genus, and +therefore, as we may naturally infer, of great importance to the +species, should be eminently liable to variation; but, on my view, this +part has undergone, since the several species branched off from a common +progenitor, an unusual amount of variability and modification, and +therefore we might expect this part generally to be still variable. But +a part may be developed in the most unusual manner, like the wing of a +bat, and yet not be more variable than any other structure, if the part +be common to many subordinate forms, that is, if it has been inherited +for a very long period; for in this case it will have been rendered +constant by long-continued natural selection. + +Glancing at instincts, marvellous as some are, they offer no greater +difficulty than does corporeal structure on the theory of the natural +selection of successive, slight, but profitable modifications. We can +thus understand why nature moves by graduated steps in endowing +different animals of the same class with their several instincts. I have +attempted to show how much light the principle of gradation throws on +the admirable architectural powers of the hive-bee. Habit no doubt +sometimes comes into play in modifying instincts; but it certainly is +not indispensable, as we see, in the case of neuter insects, which leave +no progeny to inherit the effects of long-continued habit. On the view +of all the species of the same genus having descended from a common +parent, and having inherited much in common, we can understand how it is +that allied species, when placed under considerably different conditions +of life, yet should follow nearly the same instincts; why the thrush of +South America, for instance, lines her nest with mud like our British +species. On the view of instincts having been slowly acquired through +natural selection we need not marvel at some instincts being apparently +not perfect and liable to mistakes, and at many instincts causing other +animals to suffer. + +If species be only well-marked and permanent varieties, we can at once +see why their crossed offspring should follow the same complex laws in +their degrees and kinds of resemblance to their parents,—in being +absorbed into each other by successive crosses, and in other such +points,—as do the crossed offspring of acknowledged varieties. On the +other hand, these would be strange facts if species have been +independently created, and varieties have been produced by secondary +laws. + +If we admit that the geological record is imperfect in an extreme +degree, then such facts as the record gives, support the theory of +descent with modification. New species have come on the stage slowly and +at successive intervals; and the amount of change, after equal intervals +of time, is widely different in different groups. The extinction of +species and of whole groups of species, which has played so conspicuous +a part in the history of the organic world, almost inevitably follows on +the principle of natural selection; for old forms will be supplanted by +new and improved forms. Neither single species nor groups of species +reappear when the chain of ordinary generation has once been broken. The +gradual diffusion of dominant forms, with the slow modification of their +descendants, causes the forms of life, after long intervals of time, to +appear as if they had changed simultaneously throughout the world. The +fact of the fossil remains of each formation being in some degree +intermediate in character between the fossils in the formations above +and below, is simply explained by their intermediate position in the +chain of descent. The grand fact that all extinct organic beings belong +to the same system with recent beings, falling either into the same or +into intermediate groups, follows from the living and the extinct being +the offspring of common parents. As the groups which have descended from +an ancient progenitor have generally diverged in character, the +progenitor with its early descendants will often be intermediate in +character in comparison with its later descendants; and thus we can see +why the more ancient a fossil is, the oftener it stands in some degree +intermediate between existing and allied groups. Recent forms are +generally looked at as being, in some vague sense, higher than ancient +and extinct forms; and they are in so far higher as the later and more +improved forms have conquered the older and less improved organic beings +in the struggle for life. Lastly, the law of the long endurance of +allied forms on the same continent,—of marsupials in Australia, of +edentata in America, and other such cases,—is intelligible, for within a +confined country, the recent and the extinct will naturally be allied by +descent. + +Looking to geographical distribution, if we admit that there has been +during the long course of ages much migration from one part of the world +to another, owing to former climatal and geographical changes and to the +many occasional and unknown means of dispersal, then we can understand, +on the theory of descent with modification, most of the great leading +facts in Distribution. We can see why there should be so striking a +parallelism in the distribution of organic beings throughout space, and +in their geological succession throughout time; for in both cases the +beings have been connected by the bond of ordinary generation, and the +means of modification have been the same. We see the full meaning of the +wonderful fact, which must have struck every traveller, namely, that on +the same continent, under the most diverse conditions, under heat and +cold, on mountain and lowland, on deserts and marshes, most of the +inhabitants within each great class are plainly related; for they will +generally be descendants of the same progenitors and early colonists. On +this same principle of former migration, combined in most cases with +modification, we can understand, by the aid of the Glacial period, the +identity of some few plants, and the close alliance of many others, on +the most distant mountains, under the most different climates; and +likewise the close alliance of some of the inhabitants of the sea in the +northern and southern temperate zones, though separated by the whole +intertropical ocean. Although two areas may present the same physical +conditions of life, we need feel no surprise at their inhabitants being +widely different, if they have been for a long period completely +separated from each other; for as the relation of organism to organism +is the most important of all relations, and as the two areas will have +received colonists from some third source or from each other, at various +periods and in different proportions, the course of modification in the +two areas will inevitably be different. + +On this view of migration, with subsequent modification, we can see why +oceanic islands should be inhabited by few species, but of these, that +many should be peculiar. We can clearly see why those animals which +cannot cross wide spaces of ocean, as frogs and terrestrial mammals, +should not inhabit oceanic islands; and why, on the other hand, new and +peculiar species of bats, which can traverse the ocean, should so often +be found on islands far distant from any continent. Such facts as the +presence of peculiar species of bats, and the absence of all other +mammals, on oceanic islands, are utterly inexplicable on the theory of +independent acts of creation. + +The existence of closely allied or representative species in any two +areas, implies, on the theory of descent with modification, that the +same parents formerly inhabited both areas; and we almost invariably +find that wherever many closely allied species inhabit two areas, some +identical species common to both still exist. Wherever many closely +allied yet distinct species occur, many doubtful forms and varieties of +the same species likewise occur. It is a rule of high generality that +the inhabitants of each area are related to the inhabitants of the +nearest source whence immigrants might have been derived. We see this in +nearly all the plants and animals of the Galapagos archipelago, of Juan +Fernandez, and of the other American islands being related in the most striking manner to the plants and animals of the neighbouring American -mainland; and those of the Cape de Verde archipelago and other African islands -to the African mainland. It must be admitted that these facts receive no -explanation on the theory of creation. - -The fact, as we have seen, that all past and present organic beings constitute -one grand natural system, with group subordinate to group, and with extinct -groups often falling in between recent groups, is intelligible on the theory of -natural selection with its contingencies of extinction and divergence of -character. On these same principles we see how it is, that the mutual -affinities of the species and genera within each class are so complex and -circuitous. We see why certain characters are far more serviceable than others -for classification;—why adaptive characters, though of paramount importance to -the being, are of hardly any importance in classification; why characters -derived from rudimentary parts, though of no service to the being, are often of -high classificatory value; and why embryological characters are the most +mainland; and those of the Cape de Verde archipelago and other African +islands to the African mainland. It must be admitted that these facts +receive no explanation on the theory of creation. + +The fact, as we have seen, that all past and present organic beings +constitute one grand natural system, with group subordinate to group, +and with extinct groups often falling in between recent groups, is +intelligible on the theory of natural selection with its contingencies +of extinction and divergence of character. On these same principles we +see how it is, that the mutual affinities of the species and genera +within each class are so complex and circuitous. We see why certain +characters are far more serviceable than others for classification;—why +adaptive characters, though of paramount importance to the being, are of +hardly any importance in classification; why characters derived from +rudimentary parts, though of no service to the being, are often of high +classificatory value; and why embryological characters are the most valuable of all. The real affinities of all organic beings are due to -inheritance or community of descent. The natural system is a genealogical -arrangement, in which we have to discover the lines of descent by the most -permanent characters, however slight their vital importance may be. - -The framework of bones being the same in the hand of a man, wing of a bat, fin -of the porpoise, and leg of the horse,—the same number of vertebræ forming the -neck of the giraffe and of the elephant,—and innumerable other such facts, at -once explain themselves on the theory of descent with slow and slight -successive modifications. The similarity of pattern in the wing and leg of a -bat, though used for such different purpose,—in the jaws and legs of a crab,—in -the petals, stamens, and pistils of a flower, is likewise intelligible on the -view of the gradual modification of parts or organs, which were alike in the -early progenitor of each class. On the principle of successive variations not -always supervening at an early age, and being inherited at a corresponding not -early period of life, we can clearly see why the embryos of mammals, birds, -reptiles, and fishes should be so closely alike, and should be so unlike the -adult forms. We may cease marvelling at the embryo of an air-breathing mammal -or bird having branchial slits and arteries running in loops, like those in a -fish which has to breathe the air dissolved in water, by the aid of -well-developed branchiæ. - -Disuse, aided sometimes by natural selection, will often tend to reduce an -organ, when it has become useless by changed habits or under changed conditions -of life; and we can clearly understand on this view the meaning of rudimentary -organs. But disuse and selection will generally act on each creature, when it -has come to maturity and has to play its full part in the struggle for -existence, and will thus have little power of acting on an organ during early -life; hence the organ will not be much reduced or rendered rudimentary at this -early age. The calf, for instance, has inherited teeth, which never cut through -the gums of the upper jaw, from an early progenitor having well-developed -teeth; and we may believe, that the teeth in the mature animal were reduced, -during successive generations, by disuse or by the tongue and palate having -been fitted by natural selection to browse without their aid; whereas in the -calf, the teeth have been left untouched by selection or disuse, and on the -principle of inheritance at corresponding ages have been inherited from a -remote period to the present day. On the view of each organic being and each -separate organ having been specially created, how utterly inexplicable it is -that parts, like the teeth in the embryonic calf or like the shrivelled wings -under the soldered wing-covers of some beetles, should thus so frequently bear -the plain stamp of inutility! Nature may be said to have taken pains to reveal, -by rudimentary organs and by homologous structures, her scheme of modification, -which it seems that we wilfully will not understand. +inheritance or community of descent. The natural system is a +genealogical arrangement, in which we have to discover the lines of +descent by the most permanent characters, however slight their vital +importance may be. + +The framework of bones being the same in the hand of a man, wing of a +bat, fin of the porpoise, and leg of the horse,—the same number of +vertebræ forming the neck of the giraffe and of the elephant,—and +innumerable other such facts, at once explain themselves on the theory +of descent with slow and slight successive modifications. The similarity +of pattern in the wing and leg of a bat, though used for such different +purpose,—in the jaws and legs of a crab,—in the petals, stamens, and +pistils of a flower, is likewise intelligible on the view of the gradual +modification of parts or organs, which were alike in the early +progenitor of each class. On the principle of successive variations not +always supervening at an early age, and being inherited at a +corresponding not early period of life, we can clearly see why the +embryos of mammals, birds, reptiles, and fishes should be so closely +alike, and should be so unlike the adult forms. We may cease marvelling +at the embryo of an air-breathing mammal or bird having branchial slits +and arteries running in loops, like those in a fish which has to breathe +the air dissolved in water, by the aid of well-developed branchiæ. + +Disuse, aided sometimes by natural selection, will often tend to reduce +an organ, when it has become useless by changed habits or under changed +conditions of life; and we can clearly understand on this view the +meaning of rudimentary organs. But disuse and selection will generally +act on each creature, when it has come to maturity and has to play its +full part in the struggle for existence, and will thus have little power +of acting on an organ during early life; hence the organ will not be +much reduced or rendered rudimentary at this early age. The calf, for +instance, has inherited teeth, which never cut through the gums of the +upper jaw, from an early progenitor having well-developed teeth; and we +may believe, that the teeth in the mature animal were reduced, during +successive generations, by disuse or by the tongue and palate having +been fitted by natural selection to browse without their aid; whereas in +the calf, the teeth have been left untouched by selection or disuse, and +on the principle of inheritance at corresponding ages have been +inherited from a remote period to the present day. On the view of each +organic being and each separate organ having been specially created, how +utterly inexplicable it is that parts, like the teeth in the embryonic +calf or like the shrivelled wings under the soldered wing-covers of some +beetles, should thus so frequently bear the plain stamp of inutility! +Nature may be said to have taken pains to reveal, by rudimentary organs +and by homologous structures, her scheme of modification, which it seems +that we wilfully will not understand. I have now recapitulated the chief facts and considerations which have thoroughly convinced me that species have changed, and are still slowly -changing by the preservation and accumulation of successive slight favourable -variations. Why, it may be asked, have all the most eminent living naturalists -and geologists rejected this view of the mutability of species? It cannot be -asserted that organic beings in a state of nature are subject to no variation; -it cannot be proved that the amount of variation in the course of long ages is -a limited quantity; no clear distinction has been, or can be, drawn between -species and well-marked varieties. It cannot be maintained that species when -intercrossed are invariably sterile, and varieties invariably fertile; or that -sterility is a special endowment and sign of creation. The belief that species -were immutable productions was almost unavoidable as long as the history of the -world was thought to be of short duration; and now that we have acquired some -idea of the lapse of time, we are too apt to assume, without proof, that the -geological record is so perfect that it would have afforded us plain evidence -of the mutation of species, if they had undergone mutation. - -But the chief cause of our natural unwillingness to admit that one species has -given birth to other and distinct species, is that we are always slow in -admitting any great change of which we do not see the intermediate steps. The -difficulty is the same as that felt by so many geologists, when Lyell first -insisted that long lines of inland cliffs had been formed, and great valleys -excavated, by the slow action of the coast-waves. The mind cannot possibly -grasp the full meaning of the term of a hundred million years; it cannot add up -and perceive the full effects of many slight variations, accumulated during an -almost infinite number of generations. - -Although I am fully convinced of the truth of the views given in this volume -under the form of an abstract, I by no means expect to convince experienced -naturalists whose minds are stocked with a multitude of facts all viewed, -during a long course of years, from a point of view directly opposite to mine. -It is so easy to hide our ignorance under such expressions as the “plan of -creation,” “unity of design,” etc., and to think that we give an explanation -when we only restate a fact. Any one whose disposition leads him to attach more -weight to unexplained difficulties than to the explanation of a certain number -of facts will certainly reject my theory. A few naturalists, endowed with much -flexibility of mind, and who have already begun to doubt on the immutability of -species, may be influenced by this volume; but I look with confidence to the -future, to young and rising naturalists, who will be able to view both sides of -the question with impartiality. Whoever is led to believe that species are -mutable will do good service by conscientiously expressing his conviction; for -only thus can the load of prejudice by which this subject is overwhelmed be -removed. +changing by the preservation and accumulation of successive slight +favourable variations. Why, it may be asked, have all the most eminent +living naturalists and geologists rejected this view of the mutability +of species? It cannot be asserted that organic beings in a state of +nature are subject to no variation; it cannot be proved that the amount +of variation in the course of long ages is a limited quantity; no clear +distinction has been, or can be, drawn between species and well-marked +varieties. It cannot be maintained that species when intercrossed are +invariably sterile, and varieties invariably fertile; or that sterility +is a special endowment and sign of creation. The belief that species +were immutable productions was almost unavoidable as long as the history +of the world was thought to be of short duration; and now that we have +acquired some idea of the lapse of time, we are too apt to assume, +without proof, that the geological record is so perfect that it would +have afforded us plain evidence of the mutation of species, if they had +undergone mutation. + +But the chief cause of our natural unwillingness to admit that one +species has given birth to other and distinct species, is that we are +always slow in admitting any great change of which we do not see the +intermediate steps. The difficulty is the same as that felt by so many +geologists, when Lyell first insisted that long lines of inland cliffs +had been formed, and great valleys excavated, by the slow action of the +coast-waves. The mind cannot possibly grasp the full meaning of the term +of a hundred million years; it cannot add up and perceive the full +effects of many slight variations, accumulated during an almost infinite +number of generations. + +Although I am fully convinced of the truth of the views given in this +volume under the form of an abstract, I by no means expect to convince +experienced naturalists whose minds are stocked with a multitude of +facts all viewed, during a long course of years, from a point of view +directly opposite to mine. It is so easy to hide our ignorance under +such expressions as the “plan of creation,” “unity of design,” etc., and +to think that we give an explanation when we only restate a fact. Any +one whose disposition leads him to attach more weight to unexplained +difficulties than to the explanation of a certain number of facts will +certainly reject my theory. A few naturalists, endowed with much +flexibility of mind, and who have already begun to doubt on the +immutability of species, may be influenced by this volume; but I look +with confidence to the future, to young and rising naturalists, who will +be able to view both sides of the question with impartiality. Whoever is +led to believe that species are mutable will do good service by +conscientiously expressing his conviction; for only thus can the load of +prejudice by which this subject is overwhelmed be removed. Several eminent naturalists have of late published their belief that a -multitude of reputed species in each genus are not real species; but that other -species are real, that is, have been independently created. This seems to me a -strange conclusion to arrive at. They admit that a multitude of forms, which -till lately they themselves thought were special creations, and which are still -thus looked at by the majority of naturalists, and which consequently have -every external characteristic feature of true species,—they admit that these -have been produced by variation, but they refuse to extend the same view to -other and very slightly different forms. Nevertheless they do not pretend that -they can define, or even conjecture, which are the created forms of life, and -which are those produced by secondary laws. They admit variation as a vera -causa in one case, they arbitrarily reject it in another, without assigning any -distinction in the two cases. The day will come when this will be given as a -curious illustration of the blindness of preconceived opinion. These authors -seem no more startled at a miraculous act of creation than at an ordinary -birth. But do they really believe that at innumerable periods in the earth’s -history certain elemental atoms have been commanded suddenly to flash into -living tissues? Do they believe that at each supposed act of creation one -individual or many were produced? Were all the infinitely numerous kinds of -animals and plants created as eggs or seed, or as full grown? and in the case -of mammals, were they created bearing the false marks of nourishment from the -mother’s womb? Although naturalists very properly demand a full explanation of -every difficulty from those who believe in the mutability of species, on their -own side they ignore the whole subject of the first appearance of species in -what they consider reverent silence. - -It may be asked how far I extend the doctrine of the modification of species. -The question is difficult to answer, because the more distinct the forms are -which we may consider, by so much the arguments fall away in force. But some -arguments of the greatest weight extend very far. All the members of whole -classes can be connected together by chains of affinities, and all can be -classified on the same principle, in groups subordinate to groups. Fossil -remains sometimes tend to fill up very wide intervals between existing orders. -Organs in a rudimentary condition plainly show that an early progenitor had the -organ in a fully developed state; and this in some instances necessarily -implies an enormous amount of modification in the descendants. Throughout whole -classes various structures are formed on the same pattern, and at an embryonic -age the species closely resemble each other. Therefore I cannot doubt that the -theory of descent with modification embraces all the members of the same class. -I believe that animals have descended from at most only four or five -progenitors, and plants from an equal or lesser number. - -Analogy would lead me one step further, namely, to the belief that all animals -and plants have descended from some one prototype. But analogy may be a -deceitful guide. Nevertheless all living things have much in common, in their -chemical composition, their germinal vesicles, their cellular structure, and -their laws of growth and reproduction. We see this even in so trifling a -circumstance as that the same poison often similarly affects plants and -animals; or that the poison secreted by the gall-fly produces monstrous growths -on the wild rose or oak-tree. Therefore I should infer from analogy that -probably all the organic beings which have ever lived on this earth have -descended from some one primordial form, into which life was first breathed. - -When the views entertained in this volume on the origin of species, or when -analogous views are generally admitted, we can dimly foresee that there will be -a considerable revolution in natural history. Systematists will be able to -pursue their labours as at present; but they will not be incessantly haunted by -the shadowy doubt whether this or that form be in essence a species. This I -feel sure, and I speak after experience, will be no slight relief. The endless -disputes whether or not some fifty species of British brambles are true species -will cease. Systematists will have only to decide (not that this will be easy) -whether any form be sufficiently constant and distinct from other forms, to be -capable of definition; and if definable, whether the differences be -sufficiently important to deserve a specific name. This latter point will -become a far more essential consideration than it is at present; for -differences, however slight, between any two forms, if not blended by -intermediate gradations, are looked at by most naturalists as sufficient to -raise both forms to the rank of species. Hereafter we shall be compelled to -acknowledge that the only distinction between species and well-marked varieties -is, that the latter are known, or believed, to be connected at the present day -by intermediate gradations, whereas species were formerly thus connected. -Hence, without quite rejecting the consideration of the present existence of -intermediate gradations between any two forms, we shall be led to weigh more -carefully and to value higher the actual amount of difference between them. It -is quite possible that forms now generally acknowledged to be merely varieties -may hereafter be thought worthy of specific names, as with the primrose and -cowslip; and in this case scientific and common language will come into -accordance. In short, we shall have to treat species in the same manner as -those naturalists treat genera, who admit that genera are merely artificial -combinations made for convenience. This may not be a cheering prospect; but we -shall at least be freed from the vain search for the undiscovered and -undiscoverable essence of the term species. - -The other and more general departments of natural history will rise greatly in -interest. The terms used by naturalists of affinity, relationship, community of -type, paternity, morphology, adaptive characters, rudimentary and aborted -organs, etc., will cease to be metaphorical, and will have a plain -signification. When we no longer look at an organic being as a savage looks at -a ship, as at something wholly beyond his comprehension; when we regard every -production of nature as one which has had a history; when we contemplate every -complex structure and instinct as the summing up of many contrivances, each -useful to the possessor, nearly in the same way as when we look at any great -mechanical invention as the summing up of the labour, the experience, the -reason, and even the blunders of numerous workmen; when we thus view each -organic being, how far more interesting, I speak from experience, will the -study of natural history become! - -A grand and almost untrodden field of inquiry will be opened, on the causes and -laws of variation, on correlation of growth, on the effects of use and disuse, -on the direct action of external conditions, and so forth. The study of -domestic productions will rise immensely in value. A new variety raised by man -will be a far more important and interesting subject for study than one more -species added to the infinitude of already recorded species. Our -classifications will come to be, as far as they can be so made, genealogies; -and will then truly give what may be called the plan of creation. The rules for -classifying will no doubt become simpler when we have a definite object in -view. We possess no pedigrees or armorial bearings; and we have to discover and -trace the many diverging lines of descent in our natural genealogies, by -characters of any kind which have long been inherited. Rudimentary organs will -speak infallibly with respect to the nature of long-lost structures. Species -and groups of species, which are called aberrant, and which may fancifully be -called living fossils, will aid us in forming a picture of the ancient forms of -life. Embryology will reveal to us the structure, in some degree obscured, of -the prototypes of each great class. - -When we can feel assured that all the individuals of the same species, and all -the closely allied species of most genera, have within a not very remote period -descended from one parent, and have migrated from some one birthplace; and when -we better know the many means of migration, then, by the light which geology -now throws, and will continue to throw, on former changes of climate and of the -level of the land, we shall surely be enabled to trace in an admirable manner -the former migrations of the inhabitants of the whole world. Even at present, -by comparing the differences of the inhabitants of the sea on the opposite -sides of a continent, and the nature of the various inhabitants of that -continent in relation to their apparent means of immigration, some light can be -thrown on ancient geography. - -The noble science of Geology loses glory from the extreme imperfection of the -record. The crust of the earth with its embedded remains must not be looked at -as a well-filled museum, but as a poor collection made at hazard and at rare -intervals. The accumulation of each great fossiliferous formation will be -recognised as having depended on an unusual concurrence of circumstances, and -the blank intervals between the successive stages as having been of vast -duration. But we shall be able to gauge with some security the duration of -these intervals by a comparison of the preceding and succeeding organic forms. -We must be cautious in attempting to correlate as strictly contemporaneous two -formations, which include few identical species, by the general succession of -their forms of life. As species are produced and exterminated by slowly acting -and still existing causes, and not by miraculous acts of creation and by -catastrophes; and as the most important of all causes of organic change is one -which is almost independent of altered and perhaps suddenly altered physical -conditions, namely, the mutual relation of organism to organism,—the -improvement of one being entailing the improvement or the extermination of -others; it follows, that the amount of organic change in the fossils of -consecutive formations probably serves as a fair measure of the lapse of actual -time. A number of species, however, keeping in a body might remain for a long -period unchanged, whilst within this same period, several of these species, by -migrating into new countries and coming into competition with foreign -associates, might become modified; so that we must not overrate the accuracy of -organic change as a measure of time. During early periods of the earth’s -history, when the forms of life were probably fewer and simpler, the rate of -change was probably slower; and at the first dawn of life, when very few forms -of the simplest structure existed, the rate of change may have been slow in an -extreme degree. The whole history of the world, as at present known, although -of a length quite incomprehensible by us, will hereafter be recognised as a -mere fragment of time, compared with the ages which have elapsed since the -first creature, the progenitor of innumerable extinct and living descendants, -was created. - -In the distant future I see open fields for far more important researches. -Psychology will be based on a new foundation, that of the necessary acquirement -of each mental power and capacity by gradation. Light will be thrown on the -origin of man and his history. - -Authors of the highest eminence seem to be fully satisfied with the view that -each species has been independently created. To my mind it accords better with -what we know of the laws impressed on matter by the Creator, that the -production and extinction of the past and present inhabitants of the world -should have been due to secondary causes, like those determining the birth and -death of the individual. When I view all beings not as special creations, but -as the lineal descendants of some few beings which lived long before the first -bed of the Silurian system was deposited, they seem to me to become ennobled. -Judging from the past, we may safely infer that not one living species will -transmit its unaltered likeness to a distant futurity. And of the species now -living very few will transmit progeny of any kind to a far distant futurity; -for the manner in which all organic beings are grouped, shows that the greater -number of species of each genus, and all the species of many genera, have left -no descendants, but have become utterly extinct. We can so far take a prophetic -glance into futurity as to foretel that it will be the common and widely-spread -species, belonging to the larger and dominant groups, which will ultimately -prevail and procreate new and dominant species. As all the living forms of life -are the lineal descendants of those which lived long before the Silurian epoch, -we may feel certain that the ordinary succession by generation has never once -been broken, and that no cataclysm has desolated the whole world. Hence we may -look with some confidence to a secure future of equally inappreciable length. -And as natural selection works solely by and for the good of each being, all -corporeal and mental endowments will tend to progress towards perfection. - -It is interesting to contemplate an entangled bank, clothed with many plants of -many kinds, with birds singing on the bushes, with various insects flitting -about, and with worms crawling through the damp earth, and to reflect that -these elaborately constructed forms, so different from each other, and -dependent on each other in so complex a manner, have all been produced by laws -acting around us. These laws, taken in the largest sense, being Growth with -Reproduction; Inheritance which is almost implied by reproduction; Variability -from the indirect and direct action of the external conditions of life, and -from use and disuse; a Ratio of Increase so high as to lead to a Struggle for -Life, and as a consequence to Natural Selection, entailing Divergence of -Character and the Extinction of less-improved forms. Thus, from the war of -nature, from famine and death, the most exalted object which we are capable of -conceiving, namely, the production of the higher animals, directly follows. -There is grandeur in this view of life, with its several powers, having been -originally breathed into a few forms or into one; and that, whilst this planet -has gone cycling on according to the fixed law of gravity, from so simple a -beginning endless forms most beautiful and most wonderful have been, and are -being, evolved. +multitude of reputed species in each genus are not real species; but +that other species are real, that is, have been independently created. +This seems to me a strange conclusion to arrive at. They admit that a +multitude of forms, which till lately they themselves thought were +special creations, and which are still thus looked at by the majority of +naturalists, and which consequently have every external characteristic +feature of true species,—they admit that these have been produced by +variation, but they refuse to extend the same view to other and very +slightly different forms. Nevertheless they do not pretend that they can +define, or even conjecture, which are the created forms of life, and +which are those produced by secondary laws. They admit variation as a +vera causa in one case, they arbitrarily reject it in another, without +assigning any distinction in the two cases. The day will come when this +will be given as a curious illustration of the blindness of preconceived +opinion. These authors seem no more startled at a miraculous act of +creation than at an ordinary birth. But do they really believe that at +innumerable periods in the earth’s history certain elemental atoms have +been commanded suddenly to flash into living tissues? Do they believe +that at each supposed act of creation one individual or many were +produced? Were all the infinitely numerous kinds of animals and plants +created as eggs or seed, or as full grown? and in the case of mammals, +were they created bearing the false marks of nourishment from the +mother’s womb? Although naturalists very properly demand a full +explanation of every difficulty from those who believe in the mutability +of species, on their own side they ignore the whole subject of the first +appearance of species in what they consider reverent silence. + +It may be asked how far I extend the doctrine of the modification of +species. The question is difficult to answer, because the more distinct +the forms are which we may consider, by so much the arguments fall away +in force. But some arguments of the greatest weight extend very far. All +the members of whole classes can be connected together by chains of +affinities, and all can be classified on the same principle, in groups +subordinate to groups. Fossil remains sometimes tend to fill up very +wide intervals between existing orders. Organs in a rudimentary +condition plainly show that an early progenitor had the organ in a fully +developed state; and this in some instances necessarily implies an +enormous amount of modification in the descendants. Throughout whole +classes various structures are formed on the same pattern, and at an +embryonic age the species closely resemble each other. Therefore I +cannot doubt that the theory of descent with modification embraces all +the members of the same class. I believe that animals have descended +from at most only four or five progenitors, and plants from an equal or +lesser number. + +Analogy would lead me one step further, namely, to the belief that all +animals and plants have descended from some one prototype. But analogy +may be a deceitful guide. Nevertheless all living things have much in +common, in their chemical composition, their germinal vesicles, their +cellular structure, and their laws of growth and reproduction. We see +this even in so trifling a circumstance as that the same poison often +similarly affects plants and animals; or that the poison secreted by the +gall-fly produces monstrous growths on the wild rose or oak-tree. +Therefore I should infer from analogy that probably all the organic +beings which have ever lived on this earth have descended from some one +primordial form, into which life was first breathed. + +When the views entertained in this volume on the origin of species, or +when analogous views are generally admitted, we can dimly foresee that +there will be a considerable revolution in natural history. Systematists +will be able to pursue their labours as at present; but they will not be +incessantly haunted by the shadowy doubt whether this or that form be in +essence a species. This I feel sure, and I speak after experience, will +be no slight relief. The endless disputes whether or not some fifty +species of British brambles are true species will cease. Systematists +will have only to decide (not that this will be easy) whether any form +be sufficiently constant and distinct from other forms, to be capable of +definition; and if definable, whether the differences be sufficiently +important to deserve a specific name. This latter point will become a +far more essential consideration than it is at present; for differences, +however slight, between any two forms, if not blended by intermediate +gradations, are looked at by most naturalists as sufficient to raise +both forms to the rank of species. Hereafter we shall be compelled to +acknowledge that the only distinction between species and well-marked +varieties is, that the latter are known, or believed, to be connected at +the present day by intermediate gradations, whereas species were +formerly thus connected. Hence, without quite rejecting the +consideration of the present existence of intermediate gradations +between any two forms, we shall be led to weigh more carefully and to +value higher the actual amount of difference between them. It is quite +possible that forms now generally acknowledged to be merely varieties +may hereafter be thought worthy of specific names, as with the primrose +and cowslip; and in this case scientific and common language will come +into accordance. In short, we shall have to treat species in the same +manner as those naturalists treat genera, who admit that genera are +merely artificial combinations made for convenience. This may not be a +cheering prospect; but we shall at least be freed from the vain search +for the undiscovered and undiscoverable essence of the term species. + +The other and more general departments of natural history will rise +greatly in interest. The terms used by naturalists of affinity, +relationship, community of type, paternity, morphology, adaptive +characters, rudimentary and aborted organs, etc., will cease to be +metaphorical, and will have a plain signification. When we no longer +look at an organic being as a savage looks at a ship, as at something +wholly beyond his comprehension; when we regard every production of +nature as one which has had a history; when we contemplate every complex +structure and instinct as the summing up of many contrivances, each +useful to the possessor, nearly in the same way as when we look at any +great mechanical invention as the summing up of the labour, the +experience, the reason, and even the blunders of numerous workmen; when +we thus view each organic being, how far more interesting, I speak from +experience, will the study of natural history become! + +A grand and almost untrodden field of inquiry will be opened, on the +causes and laws of variation, on correlation of growth, on the effects +of use and disuse, on the direct action of external conditions, and so +forth. The study of domestic productions will rise immensely in value. A +new variety raised by man will be a far more important and interesting +subject for study than one more species added to the infinitude of +already recorded species. Our classifications will come to be, as far as +they can be so made, genealogies; and will then truly give what may be +called the plan of creation. The rules for classifying will no doubt +become simpler when we have a definite object in view. We possess no +pedigrees or armorial bearings; and we have to discover and trace the +many diverging lines of descent in our natural genealogies, by +characters of any kind which have long been inherited. Rudimentary +organs will speak infallibly with respect to the nature of long-lost +structures. Species and groups of species, which are called aberrant, +and which may fancifully be called living fossils, will aid us in +forming a picture of the ancient forms of life. Embryology will reveal +to us the structure, in some degree obscured, of the prototypes of each +great class. + +When we can feel assured that all the individuals of the same species, +and all the closely allied species of most genera, have within a not +very remote period descended from one parent, and have migrated from +some one birthplace; and when we better know the many means of +migration, then, by the light which geology now throws, and will +continue to throw, on former changes of climate and of the level of the +land, we shall surely be enabled to trace in an admirable manner the +former migrations of the inhabitants of the whole world. Even at +present, by comparing the differences of the inhabitants of the sea on +the opposite sides of a continent, and the nature of the various +inhabitants of that continent in relation to their apparent means of +immigration, some light can be thrown on ancient geography. + +The noble science of Geology loses glory from the extreme imperfection +of the record. The crust of the earth with its embedded remains must not +be looked at as a well-filled museum, but as a poor collection made at +hazard and at rare intervals. The accumulation of each great +fossiliferous formation will be recognised as having depended on an +unusual concurrence of circumstances, and the blank intervals between +the successive stages as having been of vast duration. But we shall be +able to gauge with some security the duration of these intervals by a +comparison of the preceding and succeeding organic forms. We must be +cautious in attempting to correlate as strictly contemporaneous two +formations, which include few identical species, by the general +succession of their forms of life. As species are produced and +exterminated by slowly acting and still existing causes, and not by +miraculous acts of creation and by catastrophes; and as the most +important of all causes of organic change is one which is almost +independent of altered and perhaps suddenly altered physical conditions, +namely, the mutual relation of organism to organism,—the improvement of +one being entailing the improvement or the extermination of others; it +follows, that the amount of organic change in the fossils of consecutive +formations probably serves as a fair measure of the lapse of actual +time. A number of species, however, keeping in a body might remain for a +long period unchanged, whilst within this same period, several of these +species, by migrating into new countries and coming into competition +with foreign associates, might become modified; so that we must not +overrate the accuracy of organic change as a measure of time. During +early periods of the earth’s history, when the forms of life were +probably fewer and simpler, the rate of change was probably slower; and +at the first dawn of life, when very few forms of the simplest structure +existed, the rate of change may have been slow in an extreme degree. The +whole history of the world, as at present known, although of a length +quite incomprehensible by us, will hereafter be recognised as a mere +fragment of time, compared with the ages which have elapsed since the +first creature, the progenitor of innumerable extinct and living +descendants, was created. + +In the distant future I see open fields for far more important +researches. Psychology will be based on a new foundation, that of the +necessary acquirement of each mental power and capacity by gradation. +Light will be thrown on the origin of man and his history. + +Authors of the highest eminence seem to be fully satisfied with the view +that each species has been independently created. To my mind it accords +better with what we know of the laws impressed on matter by the Creator, +that the production and extinction of the past and present inhabitants +of the world should have been due to secondary causes, like those +determining the birth and death of the individual. When I view all +beings not as special creations, but as the lineal descendants of some +few beings which lived long before the first bed of the Silurian system +was deposited, they seem to me to become ennobled. Judging from the +past, we may safely infer that not one living species will transmit its +unaltered likeness to a distant futurity. And of the species now living +very few will transmit progeny of any kind to a far distant futurity; +for the manner in which all organic beings are grouped, shows that the +greater number of species of each genus, and all the species of many +genera, have left no descendants, but have become utterly extinct. We +can so far take a prophetic glance into futurity as to foretel that it +will be the common and widely-spread species, belonging to the larger +and dominant groups, which will ultimately prevail and procreate new and +dominant species. As all the living forms of life are the lineal +descendants of those which lived long before the Silurian epoch, we may +feel certain that the ordinary succession by generation has never once +been broken, and that no cataclysm has desolated the whole world. Hence +we may look with some confidence to a secure future of equally +inappreciable length. And as natural selection works solely by and for +the good of each being, all corporeal and mental endowments will tend to +progress towards perfection. + +It is interesting to contemplate an entangled bank, clothed with many +plants of many kinds, with birds singing on the bushes, with various +insects flitting about, and with worms crawling through the damp earth, +and to reflect that these elaborately constructed forms, so different +from each other, and dependent on each other in so complex a manner, +have all been produced by laws acting around us. These laws, taken in +the largest sense, being Growth with Reproduction; Inheritance which is +almost implied by reproduction; Variability from the indirect and direct +action of the external conditions of life, and from use and disuse; a +Ratio of Increase so high as to lead to a Struggle for Life, and as a +consequence to Natural Selection, entailing Divergence of Character and +the Extinction of less-improved forms. Thus, from the war of nature, +from famine and death, the most exalted object which we are capable of +conceiving, namely, the production of the higher animals, directly +follows. There is grandeur in this view of life, with its several +powers, having been originally breathed into a few forms or into one; +and that, whilst this planet has gone cycling on according to the fixed +law of gravity, from so simple a beginning endless forms most beautiful +and most wonderful have been, and are being, evolved. INDEX. @@ -12966,18 +14058,13 @@ Abyssinia, plants of, 375. Acclimatisation, 139. -Affinities: -of extinct species, 329. -of organic beings, 411. +Affinities: of extinct species, 329. of organic beings, 411. -Agassiz: -on Amblyopsis, 139. -on groups of species suddenly appearing, 302, 305. -on embryological succession, 338. -on the glacial period, 366. -on embryological characters, 418. -on the embryos of vertebrata, 439. -on parallelism of embryological development and geological succession, 449. +Agassiz: on Amblyopsis, 139. on groups of species suddenly appearing, +302, 305. on embryological succession, 338. on the glacial period, +366. on embryological characters, 418. on the embryos of vertebrata, +439. on parallelism of embryological development and geological +succession, 449. Algæ of New Zealand, 376. @@ -12985,10 +14072,8 @@ Alligators, males, fighting, 88. Amblyopsis, blind fish, 139. -America, North: -productions allied to those of Europe, 371. -boulders and glaciers of, 373. -South, no modern formations on west coast, 290. +America, North: productions allied to those of Europe, 371. boulders +and glaciers of, 373. South, no modern formations on west coast, 290. Ammonites, sudden extinction of, 321. @@ -12998,14 +14083,10 @@ Analogy of variations, 159. Ancylus, 386. -Animals: -not domesticated from being variable, 17. -domestic, descended from several stocks, 19. -acclimatisation of, 141. -of Australia, 116. -with thicker fur in cold climates, 133. -blind, in caves, 137. -extinct, of Australia, 339. +Animals: not domesticated from being variable, 17. domestic, descended +from several stocks, 19. acclimatisation of, 141. of Australia, 116. +with thicker fur in cold climates, 133. blind, in caves, 137. extinct, +of Australia, 339. Anomma, 240. @@ -13013,9 +14094,7 @@ Antarctic islands, ancient flora of, 399. Antirrhinum, 161. -Ants: -attending aphides, 211. -slave-making instinct, 219. +Ants: attending aphides, 211. slave-making instinct, 219. Ants, neuter, structure of, 236. @@ -13045,15 +14124,10 @@ Asses, striped, 163. Ateuchus, 135. -Audubon: -on habits of frigate-bird, 185. -on variation in birds’-nests, 212. -on heron eating seeds, 387. +Audubon: on habits of frigate-bird, 185. on variation in birds’-nests, +212. on heron eating seeds, 387. -Australia: -animals of, 116. -dogs of, 215. -extinct animals of, 339. +Australia: animals of, 116. dogs of, 215. extinct animals of, 339. European plants in, 375. Azara on flies destroying cattle, 72. @@ -13068,69 +14142,47 @@ Bamboo with hooks, 197. Barberry, flowers of, 98. -Barrande, M.: -on Silurian colonies, 313. -on the succession of species, 325. -on parallelism of palæozoic formations, 328. -on affinities of ancient species, 330. +Barrande, M.: on Silurian colonies, 313. on the succession of species, +325. on parallelism of palæozoic formations, 328. on affinities of +ancient species, 330. Barriers, importance of, 347. Batrachians on islands, 393. -Bats: -how structure acquired, 180. -distribution of, 394. +Bats: how structure acquired, 180. distribution of, 394. Bear, catching water-insects, 184. -Bee: -sting of, 202. -queen, killing rivals, 202. +Bee: sting of, 202. queen, killing rivals, 202. Bees fertilising flowers, 73. -Bees: -hive, not sucking the red clover, 95. -cell-making instinct, 224. -humble, cells of, 225. -parasitic, 218. +Bees: hive, not sucking the red clover, 95. cell-making instinct, 224. +humble, cells of, 225. parasitic, 218. -Beetles: -wingless, in Madeira, 135. -with deficient tarsi, 135. +Beetles: wingless, in Madeira, 135. with deficient tarsi, 135. -Bentham, Mr.: -on British plants, 48. -on classification, 419. +Bentham, Mr.: on British plants, 48. on classification, 419. Berkeley, Mr., on seeds in salt-water, 358. Bermuda, birds of, 391. -Birds: -acquiring fear, 212. -annually cross the Atlantic, 364. -colour of, on continents, 132. -fossil, in caves of Brazil, 339. -of Madeira, Bermuda, and Galapagos, 390. -song of males, 89. -transporting seeds, 361. -waders, 386. -wingless, 134, 182. -with traces of embryonic teeth, 451. - -Bizcacha, 349. -affinities of, 429. +Birds: acquiring fear, 212. annually cross the Atlantic, 364. colour +of, on continents, 132. fossil, in caves of Brazil, 339. of Madeira, +Bermuda, and Galapagos, 390. song of males, 89. transporting seeds, +361. waders, 386. wingless, 134, 182. with traces of embryonic teeth, +451. + +Bizcacha, 349. affinities of, 429. Bladder for swimming in fish, 190. Blindness of cave animals, 137, -Blyth, Mr.: -on distinctness of Indian cattle, 18. -on striped Hemionus, 163. -on crossed geese, 253. +Blyth, Mr.: on distinctness of Indian cattle, 18. on striped Hemionus, +163. on crossed geese, 253. Boar, shoulder-pad of, 88. @@ -13144,9 +14196,7 @@ Boulders, erratic, on the Azores, 363. Branchiæ, 190. -Brent, Mr.: -on house-tumblers, 214. -on hawks killing pigeons, 362. +Brent, Mr.: on house-tumblers, 214. on hawks killing pigeons, 362. Brewer, Dr., on American cuckoo, 217. @@ -13176,16 +14226,12 @@ Cassini on flowers of compositæ, 145. Catasetum, 424. -Cats: -with blue eyes, deaf, 12. -variation in habits of, 91. -curling tail when going to spring, 201. +Cats: with blue eyes, deaf, 12. variation in habits of, 91. curling +tail when going to spring, 201. -Cattle: -destroying fir-trees, 71. -destroyed by flies in La Plata, 72. -breeds of, locally extinct, 111. -fertility of Indian and European breeds, 254. +Cattle: destroying fir-trees, 71. destroyed by flies in La Plata, 72. +breeds of, locally extinct, 111. fertility of Indian and European +breeds, 254. Cave, inhabitants of, blind, 137. @@ -13201,16 +14247,12 @@ Ceylon, plants of, 375. Chalk formation, 322. -Characters: -divergence of, 111. -sexual, variable, 156. -adaptive or analogical, 427. +Characters: divergence of, 111. sexual, variable, 156. adaptive or +analogical, 427. Charlock, 76. -Checks: -to increase, 67. -mutual, 71. +Checks: to increase, 67. mutual, 71. Chickens, instinctive tameness of, 216. @@ -13218,24 +14260,18 @@ Chthamalinæ, 288. Chthamalus, cretacean species of, 304. -Circumstances favourable: -to selection of domestic products, 40. -to natural selection, 101. +Circumstances favourable: to selection of domestic products, 40. to +natural selection, 101. -Cirripedes: -capable of crossing, 101. -carapace aborted, 148. -their ovigerous frena, 192. -fossil, 304. -larvæ of, 440. +Cirripedes: capable of crossing, 101. carapace aborted, 148. their +ovigerous frena, 192. fossil, 304. larvæ of, 440. Classification, 413. Clift, Mr., on the succession of types, 339. -Climate: -effects of, in checking increase of beings, 68. -adaptation of, to organisms, 139. +Climate: effects of, in checking increase of beings, 68. adaptation of, +to organisms, 139. Cobites, intestine of, 190. @@ -13243,9 +14279,8 @@ Cockroach, 76. Collections, palæontological, poor, 287. -Colour: -influenced by climate, 132. -in relation to attacks by flies, 198. +Colour: influenced by climate, 132. in relation to attacks by flies, +198. Columba livia, parent of domestic pigeons, 23. @@ -13253,9 +14288,7 @@ Colymbetes, 386. Compensation of growth, 147. -Compositæ: -outer and inner florets of, 144. -male flowers of, 451. +Compositæ: outer and inner florets of, 144. male flowers of, 451. Conclusion, general, 480. @@ -13263,15 +14296,13 @@ Conditions, slight changes in, favourable to fertility, 267. Coot, 185. -Coral: -islands, seeds drifted to, 360. -reefs, indicating movements of earth, 309. +Coral: islands, seeds drifted to, 360. reefs, indicating movements of +earth, 309. Corn-crake, 185. -Correlation: -of growth in domestic productions, 11. -of growth, 143, 198. +Correlation: of growth in domestic productions, 11. of growth, 143, +198. Cowslip, 49. @@ -13281,10 +14312,8 @@ Crinum, 250. Crosses, reciprocal, 258. -Crossing: -of domestic animals, importance in altering breeds, 20. -advantages of, 96. -unfavourable to selection, 102. +Crossing: of domestic animals, importance in altering breeds, 20. +advantages of, 96. unfavourable to selection, 102. Crustacea of New Zealand, 376. @@ -13300,38 +14329,25 @@ Currants, grafts of, 262. Currents of sea, rate of, 359. -Cuvier: -on conditions of existence, 206. -on fossil monkeys, 303. +Cuvier: on conditions of existence, 206. on fossil monkeys, 303. Cuvier, Fred., on instinct, 208. -Dana, Professor: -on blind cave-animals, 139. -on relations of crustaceans of Japan, 372. -on crustaceans of New Zealand, 376. - -De Candolle: -on struggle for existence, 62. -on umbelliferæ, 146. -on general affinities, 430. - -De Candolle, Alph.: -on low plants, widely dispersed, 406. -on widely-ranging plants being variable, 53. -on naturalisation, 115. -on winged seeds, 146. -on Alpine species suddenly becoming rare, 175. -on distribution of plants with large seeds, 360. -on vegetation of Australia, 379. -on fresh-water plants, 386. -on insular plants, 389. +Dana, Professor: on blind cave-animals, 139. on relations of +crustaceans of Japan, 372. on crustaceans of New Zealand, 376. + +De Candolle: on struggle for existence, 62. on umbelliferæ, 146. on +general affinities, 430. + +De Candolle, Alph.: on low plants, widely dispersed, 406. on +widely-ranging plants being variable, 53. on naturalisation, 115. on +winged seeds, 146. on Alpine species suddenly becoming rare, 175. on +distribution of plants with large seeds, 360. on vegetation of +Australia, 379. on fresh-water plants, 386. on insular plants, 389. Degradation of coast-rocks, 282. -Denudation: -rate of, 285. -of oldest rocks, 308. +Denudation: rate of, 285. of oldest rocks, 308. Development of ancient forms, 336. @@ -13341,13 +14357,9 @@ Dianthus, fertility of crosses, 256. Dirt on feet of birds, 362. -Dispersal: -means of, 356. -during glacial period, 365. +Dispersal: means of, 356. during glacial period, 365. -Distribution: -geographical, 346. -means of, 356. +Distribution: geographical, 346. means of, 356. Disuse, effects of, under nature, 134. @@ -13355,14 +14367,10 @@ Divergence of character, 111. Division, physiological, of labour, 115. -Dogs: -hairless, with imperfect teeth, 12. -descended from several wild stocks, 18. -domestic instincts of, 213. -inherited civilisation of, 215. -fertility of breeds together, 254. -of crosses, 268. -proportions of, when young, 444. +Dogs: hairless, with imperfect teeth, 12. descended from several wild +stocks, 18. domestic instincts of, 213. inherited civilisation of, +215. fertility of breeds together, 254. of crosses, 268. proportions +of, when young, 444. Domestication, variation under, 7. @@ -13378,9 +14386,7 @@ Driver-ant, 240. Drones killed by other bees, 202. -Duck: -domestic, wings of, reduced, 11. -logger-headed, 182. +Duck: domestic, wings of, reduced, 11. logger-headed, 182. Duckweed, 385. @@ -13392,9 +14398,7 @@ Dyticus, 386. Earl, Mr. W., on the Malay Archipelago, 395. -Ears: -drooping, in domestic animals, 11. -rudimentary, 454. +Ears: drooping, in domestic animals, 11. rudimentary, 454. Earth, seeds in roots of trees, 361. @@ -13402,47 +14406,33 @@ Eciton, 238. Economy of organisation, 147. -Edentata: -teeth and hair, 144. -fossil species of, 339. +Edentata: teeth and hair, 144. fossil species of, 339. -Edwards, Milne: -on physiological divisions of labour, 115. -on gradations of structure, 194. -on embryological characters, 418. +Edwards, Milne: on physiological divisions of labour, 115. on +gradations of structure, 194. on embryological characters, 418. Eggs, young birds escaping from, 87. Electric organs, 192. -Elephant: -rate of increase, 64. -of glacial period, 141. +Elephant: rate of increase, 64. of glacial period, 141. Embryology, 439. -Existence: -struggle for, 60. -conditions of, 206. +Existence: struggle for, 60. conditions of, 206. -Extinction: -as bearing on natural selection, 109. -of domestic varieties, 111. -317. +Extinction: as bearing on natural selection, 109. of domestic +varieties, 111. 317. -Eye: -structure of, 187. -correction for aberration, 202. +Eye: structure of, 187. correction for aberration, 202. Eyes reduced in moles, 137. Fabre, M., on parasitic sphex, 218. -Falconer, Dr.: -on naturalization of plants in India, 65. -on fossil crocodile, 313. -on elephants and mastodons, 334. -and Cautley on mammals of sub-Himalayan beds, 340. +Falconer, Dr.: on naturalization of plants in India, 65. on fossil +crocodile, 313. on elephants and mastodons, 334. and Cautley on +mammals of sub-Himalayan beds, 340. Falkland Island, wolf of, 393. @@ -13454,49 +14444,33 @@ Fear, instinctive, in birds, 212. Feet of birds, young molluscs adhering to, 385. -Fertility: -of hybrids, 249. -from slight changes in conditions, 267. -of crossed varieties, 267. +Fertility: of hybrids, 249. from slight changes in conditions, 267. of +crossed varieties, 267. -Fir-trees: -destroyed by cattle, 71. -pollen of, 203. +Fir-trees: destroyed by cattle, 71. pollen of, 203. -Fish: -flying, 182. -teleostean, sudden appearance of, 305. -eating seeds, 362, 387. -fresh-water, distribution of, 384. +Fish: flying, 182. teleostean, sudden appearance of, 305. eating +seeds, 362, 387. fresh-water, distribution of, 384. -Fishes: -ganoid, now confined to fresh water, 107. -electric organs of, 192. -ganoid, living in fresh water, 321. -of southern hemisphere, 376. +Fishes: ganoid, now confined to fresh water, 107. electric organs of, +192. ganoid, living in fresh water, 321. of southern hemisphere, 376. Flight, powers of, how acquired, 182. -Flowers: -structure of, in relation to crossing, 97. -of compositæ and umbelliferæ, 144. +Flowers: structure of, in relation to crossing, 97. of compositæ and +umbelliferæ, 144. -Forbes, E.: -on colours of shells, 132. -on abrupt range of shells in depth, 175. -on poorness of palæontological collections, 287. -on continuous succession of genera, 316. -on continental extensions, 357. -on distribution during glacial period, 366 -on parallelism in time and space, 409. +Forbes, E.: on colours of shells, 132. on abrupt range of shells in +depth, 175. on poorness of palæontological collections, 287. on +continuous succession of genera, 316. on continental extensions, 357. +on distribution during glacial period, 366 on parallelism in time and +space, 409. Forests, changes in, in America, 74. Formation, Devonian, 334. -Formations: -thickness of, in Britain, 284. -intermittent, 290. +Formations: thickness of, in Britain, 284. intermittent, 290. Formica rufescens, 219. @@ -13508,15 +14482,14 @@ Frena, ovigerous, of cirripedes, 192. Fresh-water productions, dispersal of, 383. -Fries on species in large genera being closely allied to other species, 57. +Fries on species in large genera being closely allied to other species, +57. Frigate-bird, 185. Frogs on islands, 393. -Fruit-trees: -gradual improvement of, 37. -in United States, 85. +Fruit-trees: gradual improvement of, 37. in United States, 85. varieties of, acclimatised in United States, 142. Fuci, crossed, 258. @@ -13525,43 +14498,31 @@ Fur, thicker in cold climates, 133. Furze, 439. -Galapagos Archipelago: -birds of, 390. -productions of, 398, 400. +Galapagos Archipelago: birds of, 390. productions of, 398, 400. Galeopithecus, 181. Game, increase of, checked by vermin, 68. -Gärtner: -on sterility of hybrids, 247, 255. -on reciprocal crosses, 258. -on crossed maize and verbascum, 270. -on comparison of hybrids and mongrels, 272. +Gärtner: on sterility of hybrids, 247, 255. on reciprocal crosses, 258. +on crossed maize and verbascum, 270. on comparison of hybrids and +mongrels, 272. -Geese: -fertility when crossed, 253. -upland, 185. +Geese: fertility when crossed, 253. upland, 185. Genealogy important in classification, 425. -Geoffrey St. Hilaire: -on balancement, 147. -on homologous organs, 434. +Geoffrey St. Hilaire: on balancement, 147. on homologous organs, 434. -Geoffrey St. Hilaire, Isidore: -on variability of repeated parts, 149. -on correlation in monstrosities, 11. -on correlation, 144. -on variable parts being often monstrous, 155. +Geoffrey St. Hilaire, Isidore: on variability of repeated parts, 149. +on correlation in monstrosities, 11. on correlation, 144. on variable +parts being often monstrous, 155. Geographical distribution, 346. Geography, ancient, 487. -Geology: -future progress of, 487. -imperfection of the record, 279. +Geology: future progress of, 487. imperfection of the record, 279. Giraffe, tail of, 195. @@ -13579,9 +14540,7 @@ Gooseberry, grafts of, 262. Gould, Dr. A., on land-shells, 397. -Gould, Mr.: -on colours of birds, 132. -on birds of the Galapagos, 398. +Gould, Mr.: on colours of birds, 132. on birds of the Galapagos, 398. on distribution of genera of birds, 404. Gourds, crossed, 270. @@ -13590,11 +14549,9 @@ Grafts, capacity of, 261. Grasses, varieties of, 113. -Gray, Dr. Asa: -on trees of United States, 100. -on naturalised plants in the United States, 115. -on rarity of intermediate varieties, 176. -on Alpine plants, 365. +Gray, Dr. Asa: on trees of United States, 100. on naturalised plants in +the United States, 115. on rarity of intermediate varieties, 176. on +Alpine plants, 365. Gray, Dr. J. E., on striped mule, 165. @@ -13602,19 +14559,13 @@ Grebe, 185. Groups, aberrant, 429. -Grouse: -colours of, 84. -red, a doubtful species, 49. +Grouse: colours of, 84. red, a doubtful species, 49. -Growth: -compensation of, 147. -correlation of, in domestic products, 11. +Growth: compensation of, 147. correlation of, in domestic products, 11. correlation of, 143. -Habit: -effect of, under domestication, 11. -effect of, under nature, 134. -diversified, of same species, 183. +Habit: effect of, under domestication, 11. effect of, under nature, +134. diversified, of same species, 183. Hair and teeth, correlated, 144. @@ -13636,9 +14587,8 @@ Helosciadium, 359. Hemionus, striped, 163. -Herbert, W.: -on struggle for existence, 62. -on sterility of hybrids, 249. +Herbert, W.: on struggle for existence, 62. on sterility of hybrids, +249. Hermaphrodites crossing, 96. @@ -13650,9 +14600,7 @@ Heusinger on white animals not poisoned by certain plants, 12. Hewitt, Mr., on sterility of first crosses, 264. -Himalaya: -glaciers of, 373. -plants of, 375. +Himalaya: glaciers of, 373. plants of, 375. Hippeastrum, 250. @@ -13662,21 +14610,14 @@ Hollyhock, varieties of, crossed, 271. Hooker, Dr., on trees of New Zealand, 100. -Hooker, Dr.: -on acclimatisation of Himalayan trees, 140. -on flowers of umbelliferæ, 145. -on glaciers of Himalaya, 373. -on algæ of New Zealand, 376. -on vegetation at the base of the Himalaya, 378. -on plants of Tierra del Fuego, 374, 378. -on Australian plants, 375, 399. -on relations of flora of South America, 379. -on flora of the Antarctic lands, 381, 399. -on the plants of the Galapagos, 391, 398. - -Hooks: -on bamboos, 197. -to seeds on islands, 392. +Hooker, Dr.: on acclimatisation of Himalayan trees, 140. on flowers of +umbelliferæ, 145. on glaciers of Himalaya, 373. on algæ of New +Zealand, 376. on vegetation at the base of the Himalaya, 378. on +plants of Tierra del Fuego, 374, 378. on Australian plants, 375, 399. +on relations of flora of South America, 379. on flora of the Antarctic +lands, 381, 399. on the plants of the Galapagos, 391, 398. + +Hooks: on bamboos, 197. to seeds on islands, 392. Horner, Mr., on the antiquity of Egyptians, 18. @@ -13684,20 +14625,15 @@ Horns, rudimentary, 454. Horse, fossil, in La Plata, 318. -Horses: -destroyed by flies in La Plata, 72. -striped, 163. -proportions of, when young, 445. +Horses: destroyed by flies in La Plata, 72. striped, 163. proportions +of, when young, 445. Horticulturists, selection applied by, 32. Huber on cells of bees, 230. -Huber, P.: -on reason blended with instinct, 208. -on habitual nature of instincts, 208. -on slave making ants, 219. -on Melipona domestica, 225. +Huber, P.: on reason blended with instinct, 208. on habitual nature of +instincts, 208. on slave making ants, 219. on Melipona domestica, 225. Humble-bees, cells of, 225. @@ -13705,11 +14641,9 @@ Hunter, J., on secondary sexual characters, 150. Hutton, Captain, on crossed geese, 253. -Huxley, Professor: -on structure of hermaphrodites, 101. -on embryological succession, 338. -on homologous organs, 438. -on the development of aphis, 442. +Huxley, Professor: on structure of hermaphrodites, 101. on +embryological succession, 338. on homologous organs, 438. on the +development of aphis, 442. Hybrids and mongrels compared, 272. @@ -13723,20 +14657,13 @@ Icebergs transporting seeds, 363. Increase, rate of, 63. -Individuals: -numbers favourable to selection, 102. -many, whether simultaneously created, 356. +Individuals: numbers favourable to selection, 102. many, whether +simultaneously created, 356. -Inheritance: -laws of, 12. -at corresponding ages, 14, 86. +Inheritance: laws of, 12. at corresponding ages, 14, 86. -Insects: -colour of, fitted for habitations, 84. -sea-side, colours of, 132. -blind, in caves, 138. -luminous, 193. -neuter, 236. +Insects: colour of, fitted for habitations, 84. sea-side, colours of, +132. blind, in caves, 138. luminous, 193. neuter, 236. Instinct, 207. @@ -13768,18 +14695,13 @@ Kirby on tarsi deficient in beetles, 135. Knight, Andrew, on cause of variation, 7. -Kölreuter: -on the barberry, 98. -on sterility of hybrids, 247. -on reciprocal crosses, 258. -on crossed varieties of nicotiana, 271. -on crossing male and hermaphrodite flowers, 451. +Kölreuter: on the barberry, 98. on sterility of hybrids, 247. on +reciprocal crosses, 258. on crossed varieties of nicotiana, 271. on +crossing male and hermaphrodite flowers, 451. Lamarck on adaptive characters, 427. -Land-shells: -distribution of, 397. -of Madeira, naturalised, 402. +Land-shells: distribution of, 397. of Madeira, naturalised, 402. Languages, classification of, 422. @@ -13803,9 +14725,7 @@ Lingula, Silurian, 306. Linnæus, aphorism of, 413. -Lion: -mane of, 88. -young of, striped, 439. +Lion: mane of, 88. young of, striped, 439. Lobelia fulgens, 73, 98. @@ -13819,62 +14739,45 @@ Lowness, related to wide distribution, 406. Lubbock, Mr., on the nerves of coccus, 46. -Lucas, Dr. P.: -on inheritance, 12. -on resemblance of child to parent, 275. +Lucas, Dr. P.: on inheritance, 12. on resemblance of child to parent, +275. Lund and Clausen on fossils of Brazil, 339. -Lyell, Sir C.: -on the struggle for existence, 62. -on modern changes of the earth, 95. -on measure of denudation, 283. -on a carboniferous land-shell, 289. -on fossil whales, 303. -on strata beneath Silurian system, 307. -on the imperfection of the geological record, 310. -on the appearance of species, 312. -on Barrande’s colonies, 313. -on tertiary formations of Europe and North America, 323. -on parallelism of tertiary formations, 328. -on transport of seeds by icebergs, 363. -on great alternations of climate, 382. -on the distribution of fresh-water shells, 385. -on land-shells of Madeira, 402. +Lyell, Sir C.: on the struggle for existence, 62. on modern changes of +the earth, 95. on measure of denudation, 283. on a carboniferous +land-shell, 289. on fossil whales, 303. on strata beneath Silurian +system, 307. on the imperfection of the geological record, 310. on the +appearance of species, 312. on Barrande’s colonies, 313. on tertiary +formations of Europe and North America, 323. on parallelism of tertiary +formations, 328. on transport of seeds by icebergs, 363. on great +alternations of climate, 382. on the distribution of fresh-water +shells, 385. on land-shells of Madeira, 402. Lyell and Dawson on fossilized trees in Nova Scotia, 296. Macleay on analogical characters, 427. -Madeira: -plants of, 107. -beetles of, wingless, 135. -fossil land-shells of, 339. -birds of, 390. +Madeira: plants of, 107. beetles of, wingless, 135. fossil land-shells +of, 339. birds of, 390. Magpie tame in Norway, 212. Maize, crossed, 270. -Malay Archipelago: -compared with Europe, 299. -mammals of, 395. +Malay Archipelago: compared with Europe, 299. mammals of, 395. Malpighiaceæ, 417. Mammæ, rudimentary, 451. -Mammals: -fossil, in secondary formation, 303. -insular, 393. +Mammals: fossil, in secondary formation, 303. insular, 393. Man, origin of races of, 199. Manatee, rudimentary nails of, 454. -Marsupials: -of Australia, 116. -fossil species of, 339. +Marsupials: of Australia, 116. fossil species of, 339. Martens, M., experiment on seeds, 360. @@ -13890,9 +14793,7 @@ Melipona domestica, 225. Metamorphism of oldest rocks, 308. -Mice: -destroying bees, 74. -acclimatisation of, 141. +Mice: destroying bees, 74. acclimatisation of, 141. Migration, bears on first appearance of fossils, 296. @@ -13912,9 +14813,7 @@ Modification of species, how far applicable, 483. Moles, blind, 137. -Mongrels: -fertility and sterility of, 267. -and hybrids compared, 272. +Mongrels: fertility and sterility of, 267. and hybrids compared, 272. Monkeys, fossil, 303, @@ -13934,10 +14833,8 @@ Mules, striped, 165. Müller, Dr. F., on Alpine Australian plants, 375. -Murchison, Sir R.: -on the formations of Russia, 289. -on azoic formations, 307. -on extinction, 317. +Murchison, Sir R.: on the formations of Russia, 289. on azoic +formations, 307. on extinction, 317. Mustela vison, 179. @@ -13949,14 +14846,10 @@ Myrmica, eyes of, 240. Nails, rudimentary, 453. -Natural history: -future progress of, 484. -selection, 80. -system, 413. +Natural history: future progress of, 484. selection, 80. system, 413. -Naturalisation: -of forms distinct from the indigenous species, 115. -in New Zealand, 201. +Naturalisation: of forms distinct from the indigenous species, 115. in +New Zealand, 201. Nautilus, Silurian, 306. @@ -13972,19 +14865,12 @@ Neuter insects, 236. Newman, Mr., on humble-bees, 74. -New Zealand: -productions of, not perfect, 201. -naturalised products of, 337. -fossil birds of, 339. -glacial action in, 373. -crustaceans of, 376. -algæ of, 376. -number of plants of, 389. -flora of, 399. +New Zealand: productions of, not perfect, 201. naturalised products of, +337. fossil birds of, 339. glacial action in, 373. crustaceans of, +376. algæ of, 376. number of plants of, 389. flora of, 399. -Nicotiana: -crossed varieties of, 271. -certain species very sterile, 257. +Nicotiana: crossed varieties of, 271. certain species very sterile, +257. Noble, Mr., on fertility of Rhododendron, 251. @@ -13996,37 +14882,25 @@ Onites apelles, 135. Orchis, pollen of, 193. -Organs: -of extreme perfection, 186. -electric, of fishes, 192. -of little importance, 194. -homologous, 434. -rudiments of, 450. +Organs: of extreme perfection, 186. electric, of fishes, 192. of +little importance, 194. homologous, 434. rudiments of, 450. Ornithorhynchus, 107, 416. -Ostrich: -not capable of flight, 134. -habit of laying eggs together, 218. -American, two species of, 349. +Ostrich: not capable of flight, 134. habit of laying eggs together, +218. American, two species of, 349. Otter, habits of, how acquired, 179. Ouzel, water, 185. -Owen, Professor: -on birds not flying, 134. -on vegetative repetition, 149. -on variable length of arms in ourang-outang, 150. -on the swim-bladder of fishes, 191. -on electric organs, 192. -on fossil horse of La Plata, 319. -on relations of ruminants and pachyderms, 329. -on fossil birds of New Zealand, 339. -on succession of types, 339. -on affinities of the dugong, 414. -on homologous organs, 435. -on the metamorphosis of cephalopods and spiders, 442. +Owen, Professor: on birds not flying, 134. on vegetative repetition, +149. on variable length of arms in ourang-outang, 150. on the +swim-bladder of fishes, 191. on electric organs, 192. on fossil horse +of La Plata, 319. on relations of ruminants and pachyderms, 329. on +fossil birds of New Zealand, 339. on succession of types, 339. on +affinities of the dugong, 414. on homologous organs, 435. on the +metamorphosis of cephalopods and spiders, 442. Pacific Ocean, faunas of, 348. @@ -14040,9 +14914,7 @@ Parasites, 217. Partridge, dirt on feet, 362. -Parts: -greatly developed, variable, 150. -degrees of utility of, 201. +Parts: greatly developed, variable, 150. degrees of utility of, 201. Parus major, 183. @@ -14052,9 +14924,7 @@ Peaches in United States, 85. Pear, grafts of, 261. -Pelargonium: -flowers of, 145. -sterility of, 251. +Pelargonium: flowers of, 145. sterility of, 251. Pelvis of women, 144. @@ -14070,46 +14940,33 @@ Pheasant, young, wild, 216. Philippi on tertiary species in Sicily, 312. -Pictet, Professor: -on groups of species suddenly appearing, 302, 305. -on rate of organic change, 313. -on continuous succession of genera, 316. -on close alliance of fossils in consecutive formations, 335. -on embryological succession, 338. +Pictet, Professor: on groups of species suddenly appearing, 302, 305. +on rate of organic change, 313. on continuous succession of genera, +316. on close alliance of fossils in consecutive formations, 335. on +embryological succession, 338. Pierce, Mr., on varieties of wolves, 91. -Pigeons: -with feathered feet and skin between toes, 12. -breeds described, and origin of, 20. -breeds of, how produced, 39, 42. -tumbler, not being able to get out of egg, 87. -reverting to blue colour, 160. -instinct of tumbling, 214. -carriers, killed by hawks, 362. -young of, 445. +Pigeons: with feathered feet and skin between toes, 12. breeds +described, and origin of, 20. breeds of, how produced, 39, 42. +tumbler, not being able to get out of egg, 87. reverting to blue +colour, 160. instinct of tumbling, 214. carriers, killed by hawks, +362. young of, 445. Pistil, rudimentary, 451. -Plants: -poisonous, not affecting certain coloured animals, 12. -selection applied to, 32. -gradual improvement of, 37. -not improved in barbarous countries, 38. -destroyed by insects, 67. -in midst of range, have to struggle with other plants, 77. -nectar of, 92. -fleshy, on sea-shores, 132. -fresh-water, distribution of, 386. -low in scale, widely distributed, 406. +Plants: poisonous, not affecting certain coloured animals, 12. +selection applied to, 32. gradual improvement of, 37. not improved in +barbarous countries, 38. destroyed by insects, 67. in midst of range, +have to struggle with other plants, 77. nectar of, 92. fleshy, on +sea-shores, 132. fresh-water, distribution of, 386. low in scale, +widely distributed, 406. Plumage, laws of change in sexes of birds, 89. Plums in the United States, 85. -Pointer dog: -origin of, 35. -habits of, 213. +Pointer dog: origin of, 35. habits of, 213. Poison not affecting certain coloured animals, 12. @@ -14123,8 +14980,7 @@ Potamogeton, 387. Prestwich, Mr., on English and French eocene formations, 328. -Primrose, 49. -sterility of, 247. +Primrose, 49. sterility of, 247. Primula, varieties of, 49. @@ -14142,22 +14998,17 @@ Rabbit, disposition of young, 215. Races, domestic, characters of, 16. -Race-horses: -Arab, 35. -English, 356. +Race-horses: Arab, 35. English, 356. Ramond on plants of Pyrenees, 368. -Ramsay, Professor: -on thickness of the British formations, 284. -on faults, 285. +Ramsay, Professor: on thickness of the British formations, 284. on +faults, 285. Ratio of increase, 63. -Rats: -supplanting each other, 76. -acclimatisation of, 141. -blind in cave, 137. +Rats: supplanting each other, 76. acclimatisation of, 141. blind in +cave, 137. Rattle-snake, 201. @@ -14175,17 +15026,14 @@ Reproduction, rate of, 63. Resemblance to parents in mongrels and hybrids, 273. -Reversion: -law of inheritance, 14. -in pigeons to blue colour, 160. +Reversion: law of inheritance, 14. in pigeons to blue colour, 160. Rhododendron, sterility of, 251. Richard, Professor, on Aspicarpa, 417. -Richardson, Sir J.: -on structure of squirrels, 180. -on fishes of the southern hemisphere, 376. +Richardson, Sir J.: on structure of squirrels, 180. on fishes of the +southern hemisphere, 376. Robinia, grafts of, 262. @@ -14209,48 +15057,29 @@ Schlegel on snakes, 144. Sea-water, how far injurious to seeds, 358. -Sebright, Sir J.: -on crossed animals, 20. -on selection of pigeons, 31. +Sebright, Sir J.: on crossed animals, 20. on selection of pigeons, 31. Sedgwick, Professor, on groups of species suddenly appearing, 302. Seedlings destroyed by insects, 67. -Seeds: -nutriment in, 77. -winged, 146. -power of resisting salt-water, 358. -in crops and intestines of birds, 361. -eaten by fish, 362, 387. -in mud, 386. -hooked, on islands, 392. - -Selection: -of domestic products, 29. -principle not of recent origin, 33. -unconscious, 34. -natural, 80. -sexual, 87. -natural, circumstances favourable to, 101. +Seeds: nutriment in, 77. winged, 146. power of resisting salt-water, +358. in crops and intestines of birds, 361. eaten by fish, 362, 387. +in mud, 386. hooked, on islands, 392. + +Selection: of domestic products, 29. principle not of recent origin, +33. unconscious, 34. natural, 80. sexual, 87. natural, circumstances +favourable to, 101. Sexes, relations of, 87. -Sexual: -characters variable, 156. -selection, 87. +Sexual: characters variable, 156. selection, 87. -Sheep: -Merino, their selection, 31. -two sub-breeds unintentionally produced, 36. -mountain, varieties of, 76. +Sheep: Merino, their selection, 31. two sub-breeds unintentionally +produced, 36. mountain, varieties of, 76. -Shells: -colours of, 132. -littoral, seldom embedded, 288. -fresh-water, dispersal of, 385. -of Madeira, 391. -land, distribution of, 397. +Shells: colours of, 132. littoral, seldom embedded, 288. fresh-water, +dispersal of, 385. of Madeira, 391. land, distribution of, 397. Silene, fertility of crosses, 257. @@ -14262,9 +15091,7 @@ Slave-making instinct, 219. Smith, Col. Hamilton, on striped horses, 164. -Smith, Mr. Fred.: -on slave-making ants, 219. -on neuter ants, 239. +Smith, Mr. Fred.: on slave-making ants, 219. on neuter ants, 239. Smith, Mr., of Jordan Hill, on the degradation of coast-rocks, 283. @@ -14276,14 +15103,10 @@ Sorbus, grafts of, 262. Spaniel, King Charles’s breed, 35. -Species: -polymorphic, 46. -common, variable, 53. -in large genera variable, 54. -groups of, suddenly appearing, 302, 306. -beneath Silurian formations, 306. -successively appearing, 312. -changing simultaneously throughout the world, 322. +Species: polymorphic, 46. common, variable, 53. in large genera +variable, 54. groups of, suddenly appearing, 302, 306. beneath +Silurian formations, 306. successively appearing, 312. changing +simultaneously throughout the world, 322. Spencer, Lord, on increase in size of cattle, 35. @@ -14295,9 +15118,7 @@ Spitz-dog crossed with fox, 268. Sports in plants, 9. -Sprengel, C. C.: -on crossing, 98. -on ray-florets, 145. +Sprengel, C. C.: on crossing, 98. on ray-florets, 145. Squirrels, gradations in structure, 180. @@ -14305,13 +15126,9 @@ Staffordshire, heath, changes in, 72. Stag-beetles, fighting, 88. -Sterility: -from changed conditions of life, 9. -of hybrids, 246. -laws of, 254. -causes of, 263. -from unfavourable conditions, 265. -of certain varieties, 269. +Sterility: from changed conditions of life, 9. of hybrids, 246. laws +of, 254. causes of, 263. from unfavourable conditions, 265. of +certain varieties, 269. St. Helena, productions of, 389. @@ -14341,18 +15158,13 @@ Swim-bladder, 190. System, natural, 413. -Tail: -of giraffe, 195. -of aquatic animals, 196. -rudimentary, 454. +Tail: of giraffe, 195. of aquatic animals, 196. rudimentary, 454. Tarsi deficient, 135. Tausch on umbelliferous flowers, 146. -Teeth and hair: -correlated, 144. -embryonic, traces of, in birds, 451. +Teeth and hair: correlated, 144. embryonic, traces of, in birds, 451. rudimentary, in embryonic calf, 450, 480. Tegetmeier, Mr., on cells of bees, 228, 233. @@ -14361,19 +15173,14 @@ Temminck on distribution aiding classification, 419. Thouin on grafts, 262. -Thrush: -aquatic species of, 185. -mocking, of the Galapagos, 402. -young of, spotted, 439. -nest of, 243. +Thrush: aquatic species of, 185. mocking, of the Galapagos, 402. young +of, spotted, 439. nest of, 243. Thuret, >M., on crossed fuci, 258. Thwaites, Mr., on acclimatisation, 140. -Tierra del Fuego: -dogs of, 215. -plants of, 374, 378. +Tierra del Fuego: dogs of, 215. plants of, 374, 378. Timber-drift, 360. @@ -14389,9 +15196,8 @@ Tomes, Mr., on the distribution of bats, 394. Transitions in varieties rare, 172. -Trees: -on islands belong to peculiar orders, 392. -with separated sexes, 99. +Trees: on islands belong to peculiar orders, 392. with separated sexes, +99. Trifolium pratense, 73, 94. @@ -14399,22 +15205,17 @@ Trifolium incarnatum, 94. Trigonia, 321. -Trilobites, 306. -sudden extinction of, 321. +Trilobites, 306. sudden extinction of, 321. Troglodytes, 243. Tucutucu, blind, 137. -Tumbler pigeons: -habits of, hereditary, 214. -young of, 446. +Tumbler pigeons: habits of, hereditary, 214. young of, 446. Turkey-cock, brush of hair on breast, 90. -Turkey: -naked skin on head, 197. -young, wild, 216. +Turkey: naked skin on head, 197. young, wild, 216. Turnip and cabbage, analogous variations of, 159. @@ -14422,9 +15223,7 @@ Type, unity of, 206. Types, succession of, in same areas, 338. -Udders: -enlarged by use, 11. -rudimentary, 451. +Udders: enlarged by use, 11. rudimentary, 451. Ulex, young leaves of, 439. @@ -14432,9 +15231,8 @@ Umbelliferæ, outer and inner florets of, 144. Unity of type, 206. -Use: -effects of, under domestication, 11. -effects of, in a state of nature, 134. +Use: effects of, under domestication, 11. effects of, in a state of +nature, 134. Utility, how far important in the construction of each part, 199. @@ -14442,28 +15240,17 @@ Valenciennes on fresh-water fish, 384. Variability of mongrels and hybrids, 274. -Variation: -under domestication, 7. -caused by reproductive system being affected by conditions of life, 8. -under nature, 44. -laws of, 131. - -Variations: -appear at corresponding ages, 14, 86. -analogous in distinct species, 159. - -Varieties: -natural, 44. -struggle between, 75. -domestic, extinction of, 111. -transitional, rarity of, 172. -when crossed, fertile, 267. -when crossed, sterile, 269. -classification of, 423. - -Verbascum: -sterility of, 251. -varieties of, crossed, 270. +Variation: under domestication, 7. caused by reproductive system being +affected by conditions of life, 8. under nature, 44. laws of, 131. + +Variations: appear at corresponding ages, 14, 86. analogous in distinct +species, 159. + +Varieties: natural, 44. struggle between, 75. domestic, extinction of, +111. transitional, rarity of, 172. when crossed, fertile, 267. when +crossed, sterile, 269. classification of, 423. + +Verbascum: sterility of, 251. varieties of, crossed, 270. Verneuil, M. de, on the succession of species, 325. @@ -14475,10 +15262,8 @@ Vulture, naked skin on head, 197. Wading-birds, 386. -Wallace, Mr.: -on origin of species, 2. -on law of geographical distribution, 355. -on the Malay Archipelago, 395. +Wallace, Mr.: on origin of species, 2. on law of geographical +distribution, 355. on the Malay Archipelago, 395. Wasp, sting of, 202. @@ -14486,20 +15271,15 @@ Water, fresh, productions of, 383. Water-hen, 185. -Waterhouse, Mr.: -on Australian marsupials, 116. -on greatly developed parts being variable, 150. -on the cells of bees, 225. -on general affinities, 429. +Waterhouse, Mr.: on Australian marsupials, 116. on greatly developed +parts being variable, 150. on the cells of bees, 225. on general +affinities, 429. Water-ouzel, 185. -Watson, Mr. H. C.: -on range of varieties of British plants, 58. -on acclimatisation, 140. -on flora of Azores, 363. -on Alpine plants, 367, 376. -on rarity of intermediate varieties, 176. +Watson, Mr. H. C.: on range of varieties of British plants, 58. on +acclimatisation, 140. on flora of Azores, 363. on Alpine plants, 367, +376. on rarity of intermediate varieties, 176. Weald, denudation of, 285. @@ -14507,10 +15287,9 @@ Web of feet in water-birds, 185. West Indian islands, mammals of, 395. -Westwood: -on species in large genera being closely allied to others, 57. -on the tarsi of Engidæ, 157. -on the antennæ of hymenopterous insects, 416. +Westwood: on species in large genera being closely allied to others, 57. +on the tarsi of Engidæ, 157. on the antennæ of hymenopterous insects, +416. Whales, fossil, 303. @@ -14520,42 +15299,29 @@ White Mountains, flora of, 365. Wings, reduction of size, 134. -Wings: -of insects homologous with branchiæ, 191. -rudimentary, in insects, 451. +Wings: of insects homologous with branchiæ, 191. rudimentary, in +insects, 451. -Wolf: -crossed with dog, 214. -of Falkland Isles, 393. +Wolf: crossed with dog, 214. of Falkland Isles, 393. -Wollaston, Mr.: -on varieties of insects, 48. -on fossil varieties of land-shells in Madeira, 52. -on colours of insects on sea-shore, 132. -on wingless beetles, 135. -on rarity of intermediate varieties, 176. -on insular insects, 389. -on land-shells of Madeira, naturalised, 402. +Wollaston, Mr.: on varieties of insects, 48. on fossil varieties of +land-shells in Madeira, 52. on colours of insects on sea-shore, 132. +on wingless beetles, 135. on rarity of intermediate varieties, 176. on +insular insects, 389. on land-shells of Madeira, naturalised, 402. Wolves, varieties of, 90. -Woodpecker: -habits of, 184. -green colour of, 197. +Woodpecker: habits of, 184. green colour of, 197. -Woodward, Mr.: -on the duration of specific forms, 293. -on the continuous succession of genera, 316. -on the succession of types, 339. +Woodward, Mr.: on the duration of specific forms, 293. on the +continuous succession of genera, 316. on the succession of types, 339. World, species changing simultaneously throughout, 322. Wrens, nest of, 243. -Youatt, Mr.: -on selection, 31. -on sub-breeds of sheep, 36. -on rudimentary horns in young cattle, 454. +Youatt, Mr.: on selection, 31. on sub-breeds of sheep, 36. on +rudimentary horns in young cattle, 454. Zebra, stripes on, 163. diff --git a/darwin/corpus/OS.txt_note.txt b/darwin/corpus/OS.txt_note.txt @@ -0,0 +1,8 @@ +of the structure, owing to the mysterious laws of the correlation of +growth. +aboriginal stocks. Hence it has been argued that no deductions can be +drawn from domestic races to species in a state of nature. I have in +descendants. I am surprised that no one has advanced this demonstrative +case of neuter insects, against the well-known doctrine of Lamarck. +As this whole volume is one long argument, it may be convenient to the +instinct. The truth of these propositions cannot, I think, be disputed. diff --git a/darwin/introbiblio b/darwin/introbiblio @@ -0,0 +1,15 @@ +## Bibliographie + +- Reed, Baron, "Certainty", The Stanford Encyclopedia of Philosophy (Spring 2022 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/spr2022/entries/certainty/>. +- Farley, John et Geison, Gerald, 1974. « Science, politics and spontaneous generation in nineteenth-century France : the Pasteur-Pouchet debate », Bulletin of History of Medicine, vol. 48, n° 2 : 161- 198. +- Moritz Hunsmann (11 décembre 2010). L’écriture scientifique existe-t-elle ? Les aspects concrets de la thèse. Consulté le 13 juin 2025 à l’adresse https://doi.org/10.58079/al4h +- Soler. L. (2000) Introduction à l'épistémologie. Ellipses +- Quine. W. V. (1951). «Les deux dogmes de l'empirisme». De Vienne à Cambridge, l'héritage du positivisme de 1950 à nos jours, P.Jacob. Gallimard +- Duhem. P. (1981). La théorie physique, son objet, sa structure. Vrin +- Cariou. J. (2019). Histoire des démarches scientifiques : De l’Antiquité au monde contemporain. Éditions Matériologiques +- Pence. C. H. (2018). «Sir John F. W. Herschel and Charles Darwin: Nineteenth-Century Science and its Methodology». HOPOS: The Journal of the International Society for the History of Philosophy of Science, vol. 8 (Spring 2018) + + + +## Sources primaire +- William Paley, Natural theology or evidences of the Existence and attributes of the Deity (1802) diff --git a/darwin/w_intro.md b/darwin/w_intro.md @@ -15,8 +15,59 @@ Par quel endroit on veut rentrer ? On est sur du darwin, et par simplicité on v bon on y va -Le 9 janvier 1860, Charles Darwin adresse à Thomas Huxley cette Lettre qu'il commence par cette proposition : «The History of Error is quite unimportant». L'erreur en question est celle des théories Jean-Baptiste Lamarck et dans cette lettre est attaquée la loi d'usage et non-usage (tk); l'auteur de *The Origin of Species* (1860) publié quarante-deux jours plus tôt le 28 novembre 1859, qualifie de sans intérêt le travail de son collègue français. +Le 9 janvier 1860, Charles Darwin adresse à Thomas Huxley cette lettre qu'il commence par cette proposition : «The History of Error is quite unimportant»[^?1]. L'erreur sus-mentionnée est celle des théories de Jean-Baptiste Lamarck. Précisément est attaquée la loi d'usage et non-usage (tk); l'auteur de *The Origin of Species* (1860) publié quarante-deux jours plus tôt le 28 novembre 1859, qualifie de sans intérêt le travail de son collègue français. Si Charles Darwin mésestime les travaux de Lamarck et généralement toutes les théories discrédités et substituée à une nouvelle plus convenable (?), c'est à contre-pied que l'histoire des sciences travaille désormais - se développa . *History of Error matters*, l'histoire des erreurs compte. Notamment je pense à la controverse Pasteur-Pouchet autour de la génération spontanée de la vie qui occure à la même période entre 1859 et 1864. Sans le premier travail de Farley et Geison en 1974 élargit la perspective de la nature du travail scientifique par-delà des critère intrascientifique (~) en contextualisant le débat dans ses intrications politiques et rhétorique. C'est précisément par l'intention de travailler à étayer la façon dont les scientifiques travaillent que déconsidérer l'erreur au profit du vrai occulte une partie des enjeux à la construction des connaissances scientifiques. +Cependant cette phrase synthétise-t-elle l'attitude dédaigneuse de Darwin aux erreurs? Dans son autobiographie de 1887, il écrit sa règle d'or pour laquelle il consigne systématiquement tout éléments au potentiel d'objection à ses propositions théoriques: + “I had, also, during many years followed a golden rule, namely, that whenever a published fact, a new observation or thought came across me, which was opposed to my general results, to make a memorandum of it without fail and at once; for **I had found by experience that such facts and thoughts were far more apt to escape from the memory than favourable ones**. Owing to this habit, very few objections were raised against my views which I had not at least noticed and attempted to answer.” +Alors, en conjugant ces deux extraits j'entrevois le rejet de l'erreur en tant que théorie disqualifiée par ce dont Darwin souligne l'importance des faits, observations, ou pensées au caractère crucial de réfutation. Son attention porte alors plutôt sur l'élement créateur de l'erreur. Quant à l'erreur, ou l'hypothèse réfutée, elles perdent en intérêt. +Dans cette méthode réalisé et éprouvé par Darwin, le lecteur contemporain retrouve une ressemblance avec des notions familières. Les premières sont du domaine psychologique. On retrouve la mémoire sélective qui agit pour son intérêt et engendre des biais de confirmations. La seconde a à voir avec le concept de Popper: le falsificationnisme. En effet cette attention vers la négation semble correspondre étroitement avec la méthodologie falsficationniste de Popper. Il tire d'ailleurs sa conception du progrès scientifique à travers une métaphore de la théorie de l'évolution et de la théorie de la sélection naturelle: +> «nous choisissons la théorie qui se défend le mieux dans la compétition avec d'autres théories, celle qui par la sélection naturelle, prouve qu'elle est la plus apte à vivre» (Popper 1934) + +Toutefois dans la pratique, la réfutabilité, c'est à dire la capacité d'une hypothèse à être réfuter, reste parfois une opération ambigue. Un critère crucial est envisageable mais complexe à établir, surtout dans sa vertu à écarter tout un ensemble hypothétique. En dehors des critiques holistes (Duhem 1906; Quine 1951), il est simplement à relever que nombreuses sont les marges d'indéterminations dans les occurences où la réfutabilité s'avère ambigue. C'est l'approche consciencieuse de Charles Darwin pour ses angles morts qui se révèle particulière. +Aux premiers mots de *L'Origine des espèces*, Darwin avoue et admet la possibilité d'erreurs immiscées dans son argumentaire: +>«No doubt errors will have crept in, though I hope I have always been cautious in trusting to good authorities alone.» *OS*, p.10 +La prudence dans la confiance attribuée seulement aux bonnes autorités +Cette attitude de prudence dans l'écriture apparait centrale dans la démarche darwinienne. Si bien que je me demande si elle fait part d'une singularité parmi le corpus scientifique du XIXe siècle ou si elle concourt à une manière globale. +De fait, l'attention aux biais de confirmation n'est pas unique à Darwin. William Whewell avertit dans son ouvrage *The Philosophy of the Inductive Sciences Founded Upon Their History* publié en 1840 sur la façon dont l'esprit peut s'égarer par la confirmation car «Seule l'hypothèse qui a réussi garde sa place dans la mémoire» (Whewell 1840 cité et traduit par Cariou 2019). L'entreprise de Whewell garde en outre la finalité où dans l'aboutissement de la confrontation de l'hypothèse aux fait observés qu'on puisse parvenir à ce que «tout doute est supprimé et oublié» (Whewell 1840) et donc comme le précise Cariou «Whewell pense donc que l'on peut parvenir à la suppression de tout doute, à la certitude» (Cariou 2019). Alors peut-être Darwin s'inscrit dans cette croyance quand il renvoie l'histoire des erreurs dans une relative inimportance. Si le doute peut-être entièrement écarté une fois parvenu à la certitude, dès lors s'encombrer des faits avérés comme faux apparait logiquement superflu. Cependant nous venons de le voir, écarter le doute n'est pas l'affaire d'une éradication totale mais partielle. Le doute susbsiste. De plus, dans le processus de réfutation d'une hypothèse, le doute exprime l'interrogation en cours. Il est une étape du procédé dont l'aboutissement permet de conclure du vrai et du faux. Toutefois même à l'écriture de l'Origine des espèces Darwin ne cesse d'exprimer les zones d'ombres de sa théorie de la sélection naturelle. Le doute apparait comme ayant une place prépondérante au sein de la réfléxion darwinienne malgré un dédain pour l'erreur. Poursuivons donc avec une courte étude de cas. +Le principe d'hérédité bien qu'un facteur essentiel de la sélection naturelle reste mystérieux dans son mécanisme (Gayon 2019) : "The laws governing inheritance are quite unknown;" (Darwin 1859). Pourtant Darwin navigue le fuligineux de l'hérédité et mobilise le principe de la descendance avec modification [*inheritance with modification*] dans l'explication de la théorie de la sélection naturelle dans le chapitre 11. Malgré l'épaisse couche d'incompréhension, il en retire un mécanisme probant et donc mobilisable : +> If strange and rare deviations of structure are truly inherited, less strange and commoner deviations may be freely admitted to be inheritable. Perhaps the correct way of viewing the whole subject, would be, to look at the inheritance of every character whatever as the rule, and non-inheritance as the anomaly. (OS, p.13) +Dans cet extrait est convoqué un ensemble de marqueur linguistique témoignant d'une prudence argumentative dans l'inférence de la transmission de caractères par l'hérédité. "If", "may be freely admitted", "Perhaps" "would be" forment une syntaxe remarquable dans sa structure d'énonciation. Particulièrement, la pause effectuée par l'usage de la ponctuation autour de "would be" dans l'usage du conditionnel marque cette intention dubitative. Nous sommes dans le domaine de la vraisemblance, car vraisemblablement, il serait de la sorte qu'un individu hériterait des caractères de ses parents. Ce langage du doute semble courrir tout au long de l'*Origine des espèces*. Quelques lignes plus loin ce schéma se répète : +> A much more important rule, which I think may be trusted, is that, at whatever period of life a peculiarity first appears, it tends to appear in the offspring at a corresponding age, though sometimes earlier. + +Un style dubitatif apparait, qui exprime, considère le doute. Darwin avait en effet à travailler ses propres incertitudes vis-à-vis de sa théorie, mais celle-ci devait aussi convaincre et faire face au doute de toute une communauté savante. + +Cependant prévenons-nous de penser que cette attitude d'esprit retranscrit dans son écriture est une façon d'éviter l'affirmation. Plutôt cela semble se rapporter à une façon de prendre parti tout en préservant une honnêté intellectuelle transparente à tout doute subsistant. C'est du moins ce que je retrouve dans la phrase qui conclue le paragraphe: +> I believe this rule to be of the highest importance in explaining the laws of embryology. + +En outre, Charles Darwin appuie ses arguments dans une logique robuste empruntée à John Herschel. Trois critères sont nécessaires dans l'administration de la preuve d'une loi cause doit être réelle, on doit pouvoir l'observer (1), la cause doit être compétente pour produire le phénomène (2) et responsable du phénomène en tant qu'elle est à l'origine du phénomène(3). Cet ensemble forme les conditions pour former la *vera causa*, une cause vraie. Cette méthode représente pour Darwin une référence méthodologique majeure de la sélection naturelle (Pence 2018). (place de la vera causa dans OS *?*). Tout est là pour à la fois assurer la rigueur scientifique des propos afin de construire la preuve et établir les zones d'incertitudes déminées au mieux de toutes erreurs. +Cependant cette dernière phrase omet totalement la place du doute chez Darwin. Et c'est l'étude de celui +/ + +En revanche caractériser la méthodologie de l'OS +faire l'histoire du doute plutot que des erreurs + +Etablir un passage du doute à la réfutation où à la confirmation + + + + + +elon Darwin, la loi d’usage et de non-usage de Lamarck est une cause réelle de variat°, mais ce n’est pas une cause compétente pour expliquer l’évolut° dans toute sa diversité. +→ Reconnaît une part de réalité aux explicat° de Lamarck . Mais il objecte que cette causalité n’a pas la compétence requise. (Darwin ne nie pas l’hérédité des caractères acquis, il admet que ça peut exister dans une certaine mesure). ⇒ L’object° : ok ça existe mais c’est pas assez compétent pour expliquer l’évolut°. + + +doute méthodique + +pb : Comment se caractérise la littérarité scientifique dans le style dubitatif de Darwin et de ses contemporains ? + + +car Charles Darwin se repose sur une épistémologie robuste de la vera causa emprunté à John Herschel qui la tire de Newton. + + +histoire des sciences qui s'intéresse aux controverses +puis histoire des sciences qui s'intéresse à la matière? + +[^?1]: qu'entend-il exactement par Histoire? sens baconnien, de collection? Ou bien au sens plus contemporain (mais Seignobos et Langlois, c'est fin 19e). Problématiser autour ? erreur série de fait erronée à collectioner/sélectionner semble évidemment délestable. Mais Histoire au sens contemporain et critique fait sens histoire des sciences controverses, erreurs @@ -24,6 +75,19 @@ histoire des sciences controverses, erreurs ## énonciation problématisation +écriture ? article + ## méthode +scientific mind, +→ Darwin was painfully aware that his judgements could be wrong, and +this is why he peppered the ‘Recollections’ with phrases such as ‘as far as I can judge’, +‘as far as I can see’, and ‘as far as I remember’. + +épistémologie régionale +complimentary science fin + +## débarras + +Darwin dans son affirmation proscrit-il entièrement les erreurs y compris les siennes ou bien seulement celle de son opposant ? Car la formule suggère une dimension universelle or dans son autobiographie publiée en 1887, nous y apprenons l'importance primordiale de Darwin pour la consigne systématique des faits disqualifiants sa théorie :