The Making of Species

The Making of Species

Author:
Frank Finn
Author:
Frank Finn
Format:
epub
language:
English

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Author: Dewar, Douglas, 1875-1957
Evolution (Biology)
The Making of Species

HEX CURASSOW FEEDING YOUNG BIRD, WHICH HAS THE PLUMAGE OF THE HENS OF THE GLOBOSE CURASSOW, ITS FATHER’S SPECIES

THE MAKING
OF SPECIES

BY DOUGLAS DEWAR, B.A. (Cantab), I.C.S., F.Z.S.
AND FRANK FINN, B.A. (Oxon), F.Z.S., M.B.O.U.
WITH FIFTEEN ILLUSTRATIONS
LONDON: JOHN LANE THE BODLEY HEAD
NEW YORK: JOHN LANE COMPANY MCMIX

Turnbull & Spears, Printers, Edinburgh

PREFACE

Post-Darwinian books on evolution fall naturally into four classes. I. Those which preach Wallaceism, as, for example, Wallace’s Darwinism, Poulton’s Essays on Evolution, and the voluminous works of Weismann. II. Those advocating Lamarckism. Cope’s Factors of Evolution and the writings of Haeckel belong to this class. III. The writings of De Vries, forming a group by themselves. They advocate the theory that species spring suddenly into being; that new species arise by mutations from pre-existing species. IV. The large number of books of a more judicial nature, books written by men who decline to subscribe to any of the above three creeds. Excellent examples of such works are Kellog’s Darwinism To-Day, Lock’s Recent Progress in the Study of Variation, Heredity, and Evolution, and T. H. Morgan’s Evolution and Adaptation.
All four classes are characterised by defects.
Books of the two first classes exhibit the faults of ardent partisanship. They formulate creeds, and, as Huxley truly remarked, “Science commits suicide when it adopts a creed.” The books which come under the third category have the defects of extreme youth. De Vries has discovered a new principle, and it is but natural that he should exaggerate its importance, and see in it more than it contains. But, as time wears on, these faults will disappear, and the theory of mutations will assume its true form and fall into its proper place, which is somewhere between the dustbin, to which Wallaceians would relegate it, and the exalted pinnacle on to which De Vries would elevate it.
In the present state of our knowledge, books of Class IV. are the most useful to the student, since they are unbiassed, and contain a judicial summing-up of the evidence for and against the various evolutionary theories which now occupy the field. Their chief defect is that they are almost entirely destructive. They shatter the faith of the reader, but offer nothing in place of that which they have destroyed. T. H. Morgan’s Evolution and Adaptation, however, contains much constructive matter, and so is the most valuable work of this class in existence.
Zoological science stands in urgent need of constructive books on evolution—books with leanings towards neither Wallaceism, nor Lamarckism, nor De Vriesism; books which shall set forth facts of all kinds, concealing none, not even those which do not admit of explanation in the present state of our knowledge.—It has been our aim to produce a book of this description.
We have endeavoured to demonstrate that neither pure Lamarckism nor pure Wallaceism affords a satisfactory explanation of the various phenomena of the organic world. We have further, while recognising the very great value of the work of De Vries, tried to show that that eminent botanist has allowed his enthusiasm to carry him a little too far into the realm of speculation. We have followed up the exposure of the weak points of the theories, which at present occupy the field, with certain suggestions, which, we believe, throw new light on many biological problems.
Our aim in writing this book has been twofold. In the first place we have attempted to place before the general public in simple language a true statement of the present position of biological science. In the second place, we have endeavoured to furnish the scientific men of the day with food for reflection.
Even as the British nation seems to be slowly but surely losing, through its conservatism, the commercial supremacy it had the good fortune to gain last century, so is it losing, through the unwillingness of many of our scientific men to keep abreast of the times, that scientific supremacy which we gained in the middle of last century by the labours of Charles Darwin and Alfred Russell Wallace. To-day it is not among Englishmen, but among Americans and Continentals, that we have to look for advanced scientific ideas.
Even as the Ultra-Cobdenites believe that Free Trade is a panacea for all economic ills, so do most English men of science believe that natural selection offers the key to every zoological problem. Both are living in a fool’s paradise. Another reason why Great Britain is losing her scientific supremacy is that too little attention is paid to bionomics, or the study of live animals. Morphology, or the science of dead organisms, receives more than its due share of attention. It is in the open, not in the museum or the dissecting-room, that nature can best be studied. Far be it from us to deprecate the study of morphology. We wish merely to insist upon the fact, that the leaders of biological science must of necessity be those naturalists who go to the tropics and other parts of the earth where nature can be studied under the most favourable conditions, and those who conduct scientific breeding experiments. Natural selection—the idea which has revolutionised modern biological science—came, not to professors, but to a couple of field-naturalists who were pursuing their researches in tropical countries. It is absurd to expect those who stay at home and gain most of their knowledge second-hand to be the pioneers of biological science.
We fear that this book will come as a rude shock to many scientific men. By way of consolation we may remind such that they will find themselves in much the same position as that occupied by theologians immediately after the appearance of the Origin of Species.
At that time theological thought was cramped by dogma. But the clergy have since reconsidered their position, they have modified their views, and thus kept abreast of the times. Meanwhile scientific men have lagged behind. The blight of dogma has seized hold of them. They have adopted a creed to which all must subscribe or be condemned as heretics. Huxley said that the adoption of a creed was tantamount to suicide. We are endeavouring to save biology in England from committing suicide, to save it from the hands of those into which it has fallen.
We would emphasise that it is not Darwinism we are attacking, but that which is erroneously called Neo-Darwinism. Neo-Darwinism is a pathological growth on Darwinism, which, we fear, can be removed only by a surgical operation.
Darwin, himself, protested in vain against the length to which some of his followers were pushing his theory. On p. 657 of the new edition of the Origin of Species he wrote: “As my conclusions have lately been much misrepresented, and as it has been stated that I attribute the modification of species exclusively to natural selection, I may be permitted to remark that in the first edition of this work, and subsequently, I placed in a most conspicuous position—namely, at the close of the Introduction—the following words: ‘I am convinced that natural selection has been the main but not the exclusive means of modification.’ This has been of no avail. Great is the power of steady misrepresentation; but the history of science shows that this power does not long endure.”
Notwithstanding this protest the Wallaceians continue on their course, and give to the world a spurious Darwinism. It is our belief that were Darwin alive to-day his sympathies would be with us, and not with those who call themselves his followers. It was one of Darwin’s strong points that he never avoided facts. If new facts came to light which were incompatible with a theory of his, he promptly modified his theory. Since his death a number of new facts have come to light which, in our opinion, plainly indicate that the theory of natural selection as enunciated by Darwin needs considerable modification.
We have in this book set forth certain of these facts and indicated the directions in which the Darwinian theory seems to require modification.
This volume originated as the result of several conversations we, the joint authors, had last summer. We discovered that we had a great many ideas in common on the subject of evolution. This seemed strange, seeing that our education had not been on the same lines. One of us took a degree in natural science at Cambridge, and subsequently entered His Majesty’s Indian Civil Service, but continued his zoological studies in India as a hobby. The other, a naturalist from childhood, nevertheless took a classical degree at Oxford, then received a technical zoological training, adopted zoology as a profession, and held for some years a position in the Natural History Museum at Calcutta.
Our conversations revealed that we were both of opinion that biology is in an unhealthy condition, especially in England, and that the science sorely needs some fresh impetus. Neither of us had the time to attempt, single-handed, to give the required impetus, but as one of us happened to be home on eighteen months’ leave, we thought we might undertake the task in collaboration.
We felt that we might collaborate the more successfully because the large number of facts collected by the one of us form the necessary complement to the philosophical studies of the other.
We have endeavoured, so far as possible, to avoid technical terms, and have made a special point of quoting, wherever practicable, familiar animals as examples, in order that the work may make its appeal not only to the zoologist but to the general reader.
It may, perhaps, be urged against us that we have quoted too freely from popular writings, including those of which we are the authors. Our reply to this is that the study of bionomics, the science of living animals, occupies so small a place in English scientific literature that we have been compelled to have recourse to popular works for many of our facts; and we would, moreover, point out that a popular work is not necessarily inaccurate in its information.
In conclusion, we would warn the reader against the danger of confounding Inference with Fact. The failure to distinguish between the two has vitiated much of the work of the Wallaceian school of biologists.
Facts are always to be accepted. Inferences should be scrutinised with the utmost care.
In making our deductions, we have endeavoured to act without bias. We shall, therefore, welcome any new facts, be they consistent with, or opposed to, our inferences.
D. D.
F. F.

CONTENTS

PAGE

CHAPTER I 1
Rise of the Theory of Natural Selection and its Subsequent Development
Pre-Darwinian Evolutionists—​Causes which led to the speedy triumph of the theory of Natural Selection—​Nature of the opposition which Darwin had to overcome—​Post-Darwinian biology—​Usually accepted classification of present-day biologists as Neo-Lamarckians and Neo-Darwinians is faulty—​Biologists fall into three classes rather than two—​Neo-Lamarckism: its defects—​Wallaceism: its defects—​Neo-Darwinism distinguished from Neo-Lamarckism and Wallaceism—​Neo-Darwinism realises the strength and weakness of the theory of Natural Selection, recognises the complexity of the problems which biologists are endeavouring to solve.
CHAPTER II 30
Some of the more Important Objections to the Theory of Natural Selection
Brief statement of Theory—​Objections to the Theory fall into two classes—​Those which strike at the root of the Theory—​Those which deny the all-sufficiency of Natural Selection—​Objections which strike at root of Theory are based on misconception—​Objections to Wallaceism—​The Theory fails to explain the origin of Variations—​Natural Selection called on to explain too much—​Unable to explain beginnings of new organs—​The Theory of change of function—​The co-ordination of variations—​The fertility of races of domesticated animals—​Missing links—​Swamping effects of intercrossing—​Small variations cannot have a survival value—​Races inhabiting same area—​Excessive specialisation—​Chance and Natural Selection—​Struggle for existence most severe among young animals—​Natural Selection fails to explain mimicry and other phenomena of colour—​Conclusion, that scarcely an organism exists which does not possess some feature inexplicable on the theory of Natural Selection as held by Wallace and his followers.
CHAPTER III 52
Variation
The assumption of Darwin and Wallace that variations are haphazard in origin and indefinite in direction—​If these assumptions be not correct Natural Selection ceases to be the fundamental factor in evolution—​Darwin’s views regarding variation underwent modification—​He eventually recognised the distinction between definite and indefinite variations, and between continuous and discontinuous variations—​Darwin attached but little importance to either definite or discontinuous variations—​Darwin’s views on the causes of variations—​Criticism of Darwin’s views—​Variations appear to occur along certain definite lines—​There seems to be a limit to the extent to which fluctuating variations can be accumulated—​De Vries’ experiments—​Bateson on “discontinuous variation”—​Views held by De Vries—​Distinction between continuous and discontinuous variations—​The work of De Vries—​Advantages enjoyed by the botanist in experimenting on the making of species—​Difficulties encountered by the animal breeder—​Mutations among animals—​The distinction between germinal and somatic variations—​The latter, though not transmitted to offspring, are often of considerable value to their possessor in the struggle for existence.
CHAPTER IV 111
Hybridism
The alleged sterility of hybrids a stumbling-block to evolutionists—​Huxley’s views—​Wallace on the sterility of hybrids—​Darwin on the same—​Wallace’s theory that the infertility of hybrids has been caused by Natural Selection so as to prevent the evils of intercrossing—​Crosses between distinct species not necessarily infertile—​Fertile crosses between species of plants—​Sterile plant hybrids—​Fertile mammalian hybrids—​Fertile bird hybrids—​Fertile hybrids among amphibia—​Limits of hybridisation—​Multiple hybrids—​Characters of hybrids—​Hybridism does not appear to have exercised much effect on the origin of new species.
CHAPTER V 133
Inheritance
Phenomena which a complete theory of inheritance must explain—​In the present state of our knowledge it is not possible to formulate a complete theory of inheritance—​Different kinds of inheritance—​Mendel’s experiments and theory—​The value and importance of Mendelism has been exaggerated—​Dominance sometimes imperfect—​Behaviour of the nucleus of the sexual cell—​Chromosomes—​Experiments of Delage and Loeb—​Those of Cuénot on mice and Castle on guinea pigs—​Suggested modification of the generally-accepted Mendelian formulæ—​Unit characters—​Biological isomerism—​Biological molecules—​Interpretation of the phenomena of variation and heredity on the conception of biological molecules—​Correlation—​Summary of the conception of biological molecules.
CHAPTER VI 170
The Colouration of Organisms
The theory of protective colouration has been carried to absurd lengths—​It will not bear close scrutiny—​Cryptic colouring—​Sematic colours—​Pseudo-sematic colours—​Batesian and Müllerian mimicry—​Conditions necessary for mimicry—​Examples—​Recognition markings—​The theory of obliterative colouration—​Criticism of the theory—​Objections to the theory of cryptic colouring—​Whiteness of the Arctic fauna is exaggerated—​Illustrative tables—​Pelagic organisms—​Objectors to the Neo-Darwinian theories of colouration are to be found among field naturalists—​G. A. B. Dewar, Gadow, Robinson, F. C. Selous quoted—​Colours of birds’ eggs—​Warning colouration—​Objections to the theory—​Eisig’s theory—​So-called intimidating attitudes of animals—​Mimicry—​The case for the theory—​The case against the theory—​“False mimicry”—​Theory of recognition colours—​The theory refuted—​Colours of flowers and fruits—​Neo-Darwinian explanations—​Objections—​Kay Robinson’s theory—​Conclusion that Neo-Darwinian theories are untenable—​Some suggestions regarding the colouration of animals—​Through the diversity of colouring of organisms something like order runs—​The connection between biological molecules and colour—​Tylor on colour patterns in animals—​Bonhote’s theory of pœcilomeres—​Summary of conclusions arrived at.
CHAPTER VII 297
Sexual Dimorphism
Meaning of the term—​Fatal to Wallaceism—​Sexual Selection—​The law of battle—​Female preference—​Mutual Selection—​Finn’s experiments—​Objections to the theory of Sexual Selection—​Wallace’s explanation of sexual dimorphism stated and shown to be unsatisfactory—​The explanation of Thomson and Geddes shown to be inadequate—​Stolzmann’s theory stated and criticised—​Neo-Lamarckian explanation of sexual dimorphism stated and criticised—​Some features of sexual dimorphism—​Dissimilarity of the sexes probably arises as a sudden mutation—​The four kinds of mutations—​Sexual dimorphism having shown itself, Natural Selection determines whether or not the organisms which display it shall survive.
CHAPTER VIII 345
The Factors of Evolution
Variation along definite lines and Natural Selection are undoubtedly important factors of evolution—​Whether or not sexual selection is a factor we are not yet in a position to decide—​Modus operandi of Natural Selection—​Correlation an important factor—​Examples of correlation—​Correlation is a subject that requires close study—​Isolation a factor in evolution—​Discriminate isolation—​Indiscriminate isolation—​Is the latter a factor?—​Romanes’ views—​Criticism of these—​Indiscriminate isolation shown to be a factor—​Summary of the methods in which new species arise—​Natural Selection does not make species—​It merely decides which of certain ready-made forms shall survive—​Natural Selection compared to a competitive examination and to a medical board—​We are yet in darkness as to the fundamental causes of the Origin of Species—​In experiment and observation rather than speculation lies the hope of discovering the nature of these causes.
Footnotes 389
Index 389

LIST OF ILLUSTRATIONS

FACING PAGE

Heck’s Curassow feeding Young Bird, which has the Plumage of the Hens of the Globose Curassow, its Father’s Species Frontispiece
By permission of the Avicultural Society.
A Turbit belonging to Mr H. P. Scatliff 92
From “The Modern Turbit,” published by “The Feathered World,” London.
Yellow-Rumped and Chestnut-Breasted Finches, with Specimens in Transitional State 98
On the left, the yellow-rumped finch; on the right, the chestnut-breasted; birds in state of change in the middle.
By permission of the Avicultural Society.
Male Amherst Pheasant 122
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