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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. 



Turnbull ^ Spears^ Printers^ Edinburgh 


OCT -1. 1971 



POST-DARWINIAN books on evolution 
fall naturally into four classes. I. Those 
which preach Wallaceism, as, for ex- 
ample, Wallace's Darwinism, Poul ton'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 

The Making of Species 

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 La- 
marckism, nor De Vriesism ; books which shall 
set forth facts of all kinds, concealing none, 
not even those which do not admit of explana- 
tion in the present state of our knowledge. — 



It has been our aim to produce a book of this 

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 specu- 
lation. 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 

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 biologi- 
cal 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 un- 
willingness 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 
b vii 

The Making of Species 

Russell Wallace. To-day it is not among 
Englishmen, but among Americans and Con- 
tinentals, 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 dis- 
secting-room, that nature can best be studied. 
Far be it from us to deprecate the study of mor- 
phology. 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 con- 
ditions, 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 them- 
selves 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 recon- 
sidered 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 

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 

Darwin, himself, protested in vain against the 
length to which some of his followers were push- 
ing his theory. On p. 657 of the new edition 

The Making of Species 

of the Origin of Species he wrote : *' As my con- 
clusions 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 Wallacelans 
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 

We have In this book set forth certain 
of these facts and Indicated the directions in 


which the Darwinian theory seems to require 

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 train- 
ing, 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 con- 
dition, 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 com- 
plement to the philosophical studies of the other. 

We have endeavoured, so far as possible, to 


The Making of Species 

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 en- 
deavoured to act without bias. We shall, there- 
fore, welcome any new facts, be they consistent 
with, or opposed to, our inferences. 

D. D. 
F. F. 





Rise of the Theory of Natural Selection and 

ITS Subsequent Development . . . i 

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. 


Some of the more Important Objections to the 

Theory of Natural Selection . . 30 

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. 



The Making of Species 

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 "discon- 
tinuous 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. 

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 

Inheritance . . . . . - ^33 

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 
Cu^not on mice and Castle on guinea pigs — Suggested modifica- 
tion of the generally-accepted Mendelian formulas — Unit 
characters — Biological isomerism — Biological molecules — Inter- 
pretation of the phenomena of variation and heredity on the 
conception of biological molecules — Correlation — Summary of 
the conception of biological molecules. 


The Colouration of Organisms . . .170 

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 
Miillerian 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— Objec- 
tions 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 recogni- 
tion 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 poecilomeres — Summary of conclusions arrived at. 

Sexual Dimorphism . . . . .297 

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 


The Making of Species 


— 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. 

The Factors of Evolution . . . 345 

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 — Indis- 
criminate 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 com- 
pared 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 

Index ...... 389 



Heck's Curassow feeding Young Bird, which has 
THE Plumage of the Hens of the Globose 
Curassow, its Father's Species . Frontispiece 

By perfuission of the Avicultural Society. 


A Turbit belonging to Mr H. P. Scatliff . 92 

Frovt " The Modern Turbit" published by " The Feathered World," 


Yellow-Rumped and Chestnut-Breasted Finches, 

with Specimens in Transitional State . 98 

On the left, the yellow-rum ped finch ; on the right, the chest- 
nut-breasted ; birds in state of change in the middle. 

By pertnission of the Aviciiltural Society. 

Male Amherst Pheasant . . . .122 

The chief colours of this species [Chrysolophi/s amherstice) are 
white and metallic green, so that it is very different in appear- 
ance from its near ally the gold pheasant. 

Harlequin Quail {Cofumix delegorguei) . . 124 

By permission of the Avicultural Society. 

Rain Qxjmi. {Coturnix coromandelica) . . 124 

The markings on the throats of these quails are of the type 
usually put down as " recognition marks," but as the Harlequin 
Quail is African and the Rain Quail Indian, the two species 
cannot possibly interbreed. The pattern, then, can have no 
" recognition " significance. 

By pertnission of the Avicultural Society 


The Making of Species 


BouRU Friar-Bird . . . . .222 

Like most of the group to which it belongs, this honey-eater 
{Tropidorky nchus bouruensis) is a soberly coloured bird, but is 
noisy, active, and aggressive. 

By permission of Messrs Hutchinson &fi Co. 

BouRu Oriole . . . . . 222 

This " mimicking" oriole {Oriohis boiLruensis) is of the same 
tone of colour as its supposed model the Friar-bird of the same 

By permission of Messrs Hutchinson &" Co. 

King-Crow or Drongo . . . .232 

This very conspicuous black bird {Dicritrus ater), ranging 
from Africa to China, is a striking feature of the landscape 
wherever it occui's. 

By permission of Messrs Hutchinson &!^ Co. 

Drongo-Cuckoo . . . . .232 

The fork of the tail in this bird is unique among cuckoos, but 
is nevertheless much less developed than in the supposed model, 
and may be an adaptation for evolutions in flight, as such tails 
usually appear to be. 

By permission of Messrs Hutchinson ^^ Co. 

Shikra Hawk . . . . 236 

The upper surface of the tail, not shown in this drawing, 
exactly corresponds with that of the cuckoo "mimic." 

By permission of Messrs Hutchinson &^ Co. 

Hawk-Cuckoo . . . . .236 

This species {Hierococcyx varius) is commonly known in India 
as the " Brain-fever bird." 

By permission of Messrs Hutchinson &^ Co 


List of Illustrations 


Brazilian Troupial . . . .284 

This species {Icterus vulgaris) is that most frequently seen in 
captivity ; the pattern of colour is found in several other allied 

By permission of Messrs HutcJiinson dr' Co. 

Indian Black-Headed Oriole . . . 284 

Several other orioles besides this {O. melanocephahis) have 
the black head. 

By permission of Messrs Hutchinson dr* Co. 

Queen Whydah . . . . .298 

This species [Tetraemira regia) is a typical example of 
seasonal sexual dimorphism, the male being long-tailed and 
conspicuously coloured only during the breeding season, and at 
other limes resembling the sparrow-like female. 

By permission of the Foreign Bird Club. 

Courtship of Skylark . . . .314 

Illustrating display by a species with no decorative colouring 
or sex difference. 





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. 

DARWINISM and evolution are not 
interchangeable terms. On this fact 
it is impossible to lay too much 
emphasis. Charles Darwin was not 
the originator of the theory of evolution, nor 
even the first to advocate it in modern times. 
The idea that all existing things have been 
produced by natural causes from some primordial 
material is as old as Aristotle. It was lost 

The Making of Species 

sight of in the mental stagnation of the Middle 
Ages. In that dark period zoological science 
was completely submerged. It was not until 
men shook off the mental lethargy that had 
held them for many generations that serious 
attention was paid to biology. From the 
moment when men began to apply scientific 
methods to that branch of knowledge the idea 
of evolution found supporters. 
*» Buffon suggested that species are not fixed, 

; but may be gradually changed by natural causes 

I into different species. 

\ Goethe was a thorough-going evolutionist ; he 
asserted that all animals were probably descended 
from a common original type. 

Lamarck was the first evolutionist who sought 
to show the means whereby evolution has been 
effected. He tried to prove that the efforts of 
animals are the causes of variation ; that these 
efforts originate changes in form during the life 
of the individual which are transmitted to its 

* offspring. 

St Hilaire was another evolutionist who en- 
deavoured to explain how evolution had occurred. 
He believed that the transformations of animals 
are effected by changes in their environment. 
These hypotheses were considered, and rightly 
considered, insufficient to explain anything like 
general evolution, so that the idea failed for a 
time to make headway. 

Strength of Darwin's Position 

As knowledge grew, as facts accumulated, the 

belief in evolution became more widespread. 

Hutton, Lyell, Spencer, and Huxley were all 

^convinced that evolution had occurred, but they 

could not explain how it had occurred. 

Thus, by the middle of last century, all that 
was needed to make evolution an article of 
scientific belief was the discovery of a method 
whereby it could be effected. This Darwin and 
Wallace were able to furnish in the shape of 
the theory of natural selection. The discovery 
was made independently, but Darwin being the 
older man, the more influential, and the one who 
had gone the more deeply and carefully into the 
matter, gained the lion's share of the credit of 
the discovery. The theory of natural selection 
is universally known as the Darwinian theory, 
notwithstanding the fact that Darwin, unlike 
Wallace, always recognised that natural selection 
is not the sole determining factor in organic 

From the moment of the enunciation of his 
great hypothesis, Darwin's position was an 
exceedingly strong one. Everything was in 
his favour. 

As we have seen, the theory was enunciated 
at the psychological moment, at the time when 
zoological science was ripe for it. Most of the 
leading zoologists were evolutionists at heart, 
and were only too ready to accept any theory 


The Making of Species 

which afforded a plausible explanation of what 
they believed to have occurred. 

Hence the rapturous welcome accorded to the 
theory of natural selection by the more pro- 
gressive biologists. 

Another point in Darwin's favour was the 
delightful simplicity of his hypothesis. Nothing 
could be more enticingly probable. It is based 
on the unassailable facts of variation, heredity, 
and the tendency of animals to multiply in 
numbers. Everybody knows that the breeder 
can fix varieties by careful breeding. Darwin 
had simply to show that there is in nature some- 
thing to take the part played among domesticated 
animals by the human breeder. This he was 
able to do. As the numbers of species remain 
stationary, it is evident that only a small portion 
of the animals that are born can reach maturity. 
A child can see that the individuals most likely 
to survive are those best adapted to the circum- 
stances of their life. Even as the breeder weeds 
out of his stock the creatures not suited to his 
purpose, so in nature do the unfit perish in the 
everlasting struggle for existence. 

In nature there is a selection corresponding to 
that of the breeder. 

It is useless to deny the existence of this selec- 
tion in nature, this natural selection. The only 
disputable point is whether such selection can 
do all that Darwin demanded of it. 


Strength of Darwin's Position 

The man in the street, then, was able to com- 
prehend the theory of natural selection. This 
was greatly in its favour. Men are usually well 
disposed towards doctrines which they can readily 

The nineteenth century was a superficial age. 
It liked simplicity in all things. If Darwin could 
show that natural selection was capable of pro- 
ducing one species, men were not only ready but 
eager to believe that it could explain the whole 
of organic evolution. 

The simplicity of the Darwinian theory has its 
evil side. It has undoubtedly tended to make 
modern biologists superficial in their methods. 
It has, indeed, stimulated the imagination of 
men of science ; but the stimulation has not in 
all cases been a healthy one. 

So far from adhering to the sound rule laid 
down by Pasteur, "never advance anything 
that cannot be proved in a simple and decisive 
manner," many modern naturalists allow their 
imagination to run riot, and so formulate ill- 
considered theories, and build up hypotheses on 
the most insecure foundations. " A tiny islet of 
truth," writes Archdale Reid, '' is discovered, on 
which are built tremendous and totally illegitimate 

Another source of Darwin's strength was the 
vast store of knowledge he had accumulated. 
For twenty years he had been steadily amassing 


The Making of Species 

facts in support of his hypothesis. He enunciated 
no crude theory, he indulged in no wild specula- 
tions. He was content to marshal a great array 
of facts, and to draw logical conclusions there- 
from. He was as cautious in his deductions as 
he was careful of his facts. He thus stood head 
and shoulders above the biologists of his day. 
He was a giant among pigmies. So well 
equipped was he that those who attempted to 
oppose him found themselves in the position of 
men, armed with bows and arrows, who seek 
to storm a fortress defended by maxim guns. 

Nor was this all. The majority of the best 
biologists of his time did not attempt to oppose 
him. They were, as we have seen, ready to 
receive with open arms any hypothesis which 
seemed to explain how evolution had occurred. 
Some of them perceived that there were weak 
points in the Darwinian theory, but they pre- 
ferred not to expose these ; they were rather 
disposed to make the best of the hypothesis. It 
had so many merits that it seemed to them but 
reasonable to suppose that subsequent investiga- 
tion would prove that the defects were apparent 
rather than real. 

We hear much of the *' magnitude of the 
prejudices " which Darwin had to overcome, and 
of the mighty battle which Darwin and his 
lieutenant Huxley had to fight before the theory 
of the origin of species by natural selection 


opponents of Darwin 

obtained acceptance. We venture to say that 
statements such as these are misleading. We 
think we may safely assert that scarcely ever has 
a theory which fundamentally changed the pre- 
vailing scientific beliefs met with less opposition. 
It would have been a good thing for zoology had 
Darwin not obtained so easy a victory. 

Sir Richard Owen, a distinguished anatomist, 
certainly attacked the doctrine in no unmeasured 
terms, but his attack was anonymous and so 
cannot be considered very formidable. Far more 
important was the opposition of Dr St George 
Mivart, whose worth as a biologist has never 
been properly appreciated. His most important 
work, entitled the Genesis of Species^ might be 
read with profit even now by many of our modern 

For some time after the publication of the 
Origin of Species Mivart appears to be almost 
the only man of science fully alive to the weak 
points of the Darwinian theory. The great 
majority seem to have been dazzled by its 

The main attack on Darwinism was conducted 
by the theologians and their allies, who considered 
it to be subversive of the Mosaic account of the 
Creation. Now, when one whose scientific know- 
ledge is, to say the best of it, not extensive, attacks 
a man who has studied his subject dispassionately 
for years, and invariably expresses himself with 


The Making of Species 

extreme caution, the onslaught can have but one 
result — the attacker will be repulsed with heavy 
loss, and the onlookers will have a higher opinion 
of his valour than of his common sense. 

The theologians were in the unfortunate posi- 
tion of warriors who do not know what it is 
against which they are fighting ; they confounded 
natural selection with evolution, and directed the 
main force of their attack against the latter, 
under the impression that they were fighting 
the Darwinian theory. 

It was the misfortune of those theologians that 
it is possible to prove that evolution, or, at aay 
rate, some evolution has occurred ; they thus 
kicked against the pricks with disastrous results 
to themselves. When this attack had been 
repulsed men believed that the theory of natural 
selection had been demonstrated, that it was 
as much a law of nature as that of gravitation. 
What had really happened was that the fact of 
evolution had been proved, and the theory of 
natural selection obtained the credit. Men 
thought that Darwinism was evolution. Had 
the theologians admitted evolution but denied 
the ability of natural selection to explain it, the 
Darwinian theory, in all probability, would not 
have gained the ascendency which it now enjoys. 

To us who are able to look back dispassionately 
upon the biological warfare of the last century, 
Darwin's opponents — or the majority of them — 


Evolution and Natural Selection 

appear very foolish. We must, however, bear in 
mind that at the time of the publication of the 
Origin of Species both natural selection and evolu- 
tion were comparatively unknown ideas. Darwin 
had to fight for both. He had to prove evolution 
as well as natural selection. Many of the facts 
adduced by him supported both. It is, there- 
fore, not altogether surprising that many of 
his opponents failed to distinguish between 

A glance at the Origin of Species will suffice to 
show how considerable is the portion of the book 
that deals with the evidence in favour of evolution 
rather than of natural selection. 

Of the fourteen chapters which make up the 
book no fewer than nine are devoted to proving 
that evolution has occurred. It has been truly 
said, that for every one fact biologists have found 
in support of the special theory of natural selec- 
tion they have found ten facts supporting the 
doctrine of evolution. Darwin, then, was in the 
position of a skilled barrister who has a plausible 
case and who knows the ins and outs of his brief, 
while his opponents stood in the shoes of inex- 
perienced counsel who had but recently received 
their brief, and who had not had the time to 
master the details thereof. In such circum- 
stances it is not difficult to predict which way the 
verdict of the jury will go. 

Darwin, moreover, had a charming personality. 


The Making of Species 

Never was a man with a theory less dogmatic. 
Never was the holder of a theory more careful of 
the expressions he used. Never was a scientific 
man more ready to give ear to his opponents, to 
meet them half way, and, where necessary, to 
compromise. Darwin was not afraid of facts, 
and was always ready to alter his views when 
they appeared to be opposed to facts. The 
average scientific man of to-day makes facts 
fit his theory ; if they refuse to fit it he ignores 
or denies them. 

Darwin continually modified his views ; when 
he found himself in a tight place he did not 
hesitate to resort to Lamarckian factors, such as 
the inheritance of the effects of use and disuse 
and of the effects of environment. He conceded 
that natural selection was insufficient to account 
for all the phenomena of organic evolution, and 
advanced the theory of sexual selection in order 
to account for facts which the major hypothesis 
seemed to him incapable of explaining. 

Darwin, moreover, having ample private means, 
was not obliged to work for a living, and was 
therefore able to devote the whole of his time to 
research. The advantages of such a position 
cannot be over-estimated, and, perhaps, have not 
been sufficiently taken into account in apportion- 
ing the praise between Darwin and Wallace for 
their great discovery. 

To all these factors in Darwin's favour we 



must add his good fortune in possessing so able 
a lieutenant as Huxley. 

Huxley was an ardent evolutionist, an able 
writer, and a brilliant debater. A man of his 
mental calibre was able, like a clever barrister, 
to make out a plausible case for any theory which 
he chose to take up. While nominally a strong 
supporter of the Darwinian theory, he was in 
reality fighting for the doctrine of descent. Had 
any plausible theory of evolution been enunciated, 
Huxley would undoubtedly have fought for it 
equally earnestly. 

A firm believer in evolution, Huxley was, 
as Professor Poulton says, confronted by two 
difficulties, — first, the insufficiency of the evi- 
dence of evolution, and, secondly, the absence of 
any explanation of how the phenomenon had 
occurred. The Origin of Species solved both 
these difficulties. It adduced much weighty evi- 
dence in favour of evolution, and suggested a 
modus operandi. Small wonder, then, that 
Huxley became a champion of Darwinism. But, 
as Poulton writes, on page 202 of Essays on 
Evolution, "while natural selection thus enabled 
Huxley freely to accept evolution, he was by no 
means fully satisfied with it." '* He never com- 
mitted himself to a full belief in natural selection, 
and even contemplated the possibility of its 
ultimate disappearance." To use Huxley's own 
words : ** Whether the particular shape which the 


The Making of Species 

doctrine of evolution, as applied to the organic 
world, took in Darwin's hands, would prove to be 
final or not, was, to me, a matter of indifference." 

The result of the fortuitous combination of the 
circumstances which we have set forth was that 
in a surprisingly short time the theory of natural 
selection came to be regarded as a law of nature 
on a par with the laws of gravitation. Thus, 
paradoxical though it seems, practical certainty 
was given to a hitherto uncertain doctrine by the 
addition of a still more uncertain theory. 

"At once," writes Waggett, ''the theory of 
development leapt from the position of an obscure 
guess to that of a fully-equipped theory and 
almost a certainty." 

Darwin thus became a dictator whose authority 
none durst question. A crowd of slavish adher- 
ents gathered round him, a herd of men to whom 
he seemed an absolutely unquestionable authority. 
Darwinism became a creed to which all must 
subscribe. It still retains this position in the 
popular mind. 

The ease with which the theory of natural 
selection gained supremacy was, as we have 
already said, a misfortune to biological science. 
It produced for a time a considerable mental 
stagnation among zoologists. Since Darwin's 
day the science has not made the progress that 
might reasonably have been expected, because 
the theory has so captivated the minds of the 


Growing Opposition to Darwinism 

majority of biologists that they see everything 
through Darwinian spectacles. The wish has 
been in many cases the father to the observation. 
Zoologists are ever on the lookout for the action 
of natural selection, and in consequence frequently 
imagine they see it where it does not exist. 
Many naturalists, consciously or unconsciously, 
stretch facts to make them fit the Darwinian theory. 
Those facts which refuse to be so distorted are, if 
not actively ignored or suppressed, overlooked as 
throwing no light upon the doctrine. This is no 
exaggeration. A perusal of almost any popular 
book dealing with zoological theory leaves the 
impression that there is nothing left to be ex- 
plained in the living world, that there is no door 
leading to the secret chambers of nature to which 
natural selection is not an " open sesame." 

But the triumph of natural selection has not 
been so complete as its more enthusiastic sup- 
porters would have us believe. Some there are 
who have never admitted the all-sufficiency of 
natural selection. In the British Isles these have 
never been numerous. In the United States of 
America and on the Continent they are more 
abundant. The tendency seems to be for them 
to increase in numbers. Hence the recent 
lamentations of Dr Wallace and Sir E. Ray 
Lankester. Modern biologists are commonly 
supposed to fall into two schools of thought — 
the Neo- Darwinian and the Neo-Lamarckian. 


The Making of Species 

The former are the larger body, and pin their 
faith absolutely to natural selection. They deny 
the inheritance of acquired characters, and preach 
the all-sufficiency of natural selection to explain 
the varied phenomena of nature. The Neo- 
Lamarckians do not admit the omnipotency of 
natural selection. Some of them allow it no 
virtue. Others regard it as a force which keeps 
variation within fixed limits, which says to each 
organism, *'thus far shalt thou vary and no 
farther." This school lays great stress on the 
inheritance of acquired characters, especially 
on the inheritance of the effects of use and 

The above statement of the recent develop- 
ments of Darwinism is incomplete, for it fails to 
include those who occupy a middle position. If 
it be possible to classify a large number of men 
of which scarcely any two hold identical views, 
it is into three, rather than two, classes that they 
must be divided. 

Speaking broadly, evolutionists of to-day may 
be said to represent three distinct lines of thought. 
For the sake of classification we may speak of 
them as falling into three schools, which we may 
term the Neo-Lamarckian, the Wallaceian, and 
the Neo-Darwinian, according as their views in- 
cline towards those held by Lamarck, Wallace, 
or Darwin. 

As adherents of the Neo-Lamarckian school, 

The Neo-Lamarckian School 

we cite Cope, Spencer, Orr, Eimer, Naegeli, 
Henslow, Cunningham, Haeckel, Korchinsky, 
and a number of others. It may almost be said 
of these Neo-Lamarckians that each holds a 
totally distinct theory of evolution. So hetero- 
geneous are their views that it is difficult to find 
a single article common to the evolutionary belief 
of all. It is commonly asserted that all Neo- 
Lamarckians are agreed, firstly, that acquired 
characters are transmissible ; and, secondly, that 
such transmission is an important factor in the 
production of new species. This assertion is 
certainly true of the great bulk of Neo- 
Lamarckians, but it does not appear to hold in 
the case of those who believe that evolution is 
the result of some unknown inner force. So far 
as we can see, a belief in the inheritance of 
acquired characters is not necessary to the 
theories of orthogenesis held by Naegeli and 
Korchinsky. For that reason it would possibly 
be more correct to place those who hold such 
views in a fourth school. Since, however, a 
number of undoubted Neo-Lamarckians, as, for 
example. Cope, believe in an inner growth-force, 
it is convenient to regard Naegeli as a Neo- 
Lamarckian. His views need not detain us long. 
Those who wish to study them in detail will find 
them in his Mechanisch-physiologische Theorie 
der Abstammungslehre. 

Naegeli believes that there is inherent in 


The Making of Species 

protoplasm a growth-force, which makes each 
organism in itself a force making towards pro- 
gressive evolution. He holds that animals and 
plants would have become much as they are now 
even if no struggle for existence had taken place. 
**To the believers in this kind of . . . ortho- 
genesis," writes Kellog {^Darwinism To-day, p. 
278), ** organic evolution has been, and is now, 
ruled by unknown inner forces inherent in organ- 
isms, and has been independent of the influence 
of the outer world. The lines of evolution are 
immanent, unchangeable, and ever slowly stretch 
toward some ideal goal." It is easy to enunciate 
such a theory, impossible to prove it, and difficult 
to disprove it. 

It seems to us that the fact that, so soon as 
organisms are removed from the struggle for 
existence, they tend to degenerate, is a sufficient 
reason for refusing to accept theories of the 
description put forth by Naegeli. More truly 
Lamarckian is Elmer's theory of orthogenesis, 
according to which it is the environment which 
determines the direction which variation takes ; 
and the variations which are induced by the 
environment are transmitted to the offspring. 

Spencer and Orr preach nearly pure Lamarck- 
ism. The former, while fully recognising the 
importance of natural selection, considered that 
sufficient weight has not been given to the 
effects of use and disuse, or to the direct action 


Orr's Views 

of the environment in determining or modifying 

The similarity of the views of Orr and 
Lamarck is best seen by comparing their re- 
spective explanations of the long neck of the 
giraffe. Lamarck thought that this was the 
direct result of continual stretching. The animal 
continually strains its neck in the search for food, 
hence it grows longer as the individual grows 
older, and this elongated neck has been trans- 
mitted to the offspring. Orr writes, on page 164 
of his Development and Heredity : " The giraffe 
seems to present the most remarkable illustration 
of the lengthening of the bones as the result of 
the frequent repetition of such shocks. As is 
well known, this animal feeds on the foliage of 
trees. From the earliest youth of the species, 
and the earliest youth of each individual, it must 
have been stretching upwards for food, and, as is 
the custom of such quadrupeds, it must have 
constantly raised itself off its forefeet, and, as it 
dropped, must have received a shock that made 
itself felt from the hoofs through the legs and 
vertical neck to the head. In the hind legs the 
shock would not be felt. It is impossible to 
imagine that an animal which, during the greater 
part of every day of its life (both its individual 
and racial life), performed motions so uniform 
and constant, would not be peculiarly specialised 
as a result. The forces acting upon such an 

B 17 

The Making of Species 

animal are widely different from the forces acting 
upon an animal which eats the grass at its feet 
like an ox, or one which must run and climb like 
a goat or a deer, and the resultant modifications 
of growth in the several cases must also be 
different. The principle of increased growth in 
the direction of the shock, resulting from super- 
abundant repair of the momentary compression, 
explains how the giraffe acquired the phenomenal 
length of the bones of its forelegs and neck ; 
and the absence of the shock in the hind-quarters 
shows why they remained undeveloped and 
absurdly disproportionate to the rest of the 

It seems to us that a fatal objection to all 
these Neo-Lamarckian theories of evolution is 
that they are based on the assumption that 
acquired characters are inherited, whereas all 
the evidence goes to show that such characters 
are not inherited. In these days, when scientific 
knowledge is so widely diffused, it is scarcely 
necessary to say that all the characteristics which 
an organism displays are either congenital or 
inborn, or acquired by the organism during its 
lifetime. Thus a man may have naturally a 
large biceps muscle, and this is a congenital 
character ; or he may by constant exercise 
develop or greatly increase the size of the 
biceps. The large biceps, in so far as it has 
been increased by exercise, is said to be an 


Inheritance of Acquired Characters 

acquired character, for it was not inherited by- 
its possessor, but acquired by him in his lifetime. 
We must bear in mind that the period in the Hfe 
history of an organism at which a character 
appears, is not necessarily a test as to whether 
it is congenital or acquired, for a great many 
congenital characters, such as a man's beard, do 
not appear until some years after birth. As we 
have seen, the Neo-Lamarckians believe that it 
is possible for an organism to transmit to its 
offspring characters which it has acquired during 
the course of its existence. But, as we have 
already said, the evidence goes to show that 
such characters are not inherited. For example, 
the tail of the young fox-terrier is not shorter 
than that of other breeds of dogs, notwith- 
standing the fact that its ancestors have for 
generations had the greater portion of their 
caudal appendage removed shortly after birth. 

We do not propose to discuss at any great 
length the vexed question of the inheritance 
of acquired characters, for the simple reason that 
the Neo-Lamarckians have not brought forward 
a single instance which indubitably proves that 
such characters are inherited. 

Mr J. T. Cunningham, in a paper of great 
value and interest, entitled *' The Heredity of 
Secondary Sexual Characters in relation to 
Hormones : a Theory of the Heredity of 
Somatogenic Characters," which appeared in 


The Making of Species 

vol. xxvi., No. 3, of the Archiv fur Ent- 
wicklungsmechanik des Organismen^ states : 
*' The dogma that acquired characters cannot 
be inherited ... is founded not so much on 
evidence, or the absence of evidence, as on a 
priori reasoning, on the supposed difficulty or 
impossibility of conceiving a means by which 
such inheritance could be effected." Such 
appears certainly to be true of some zoologists, 
but we trust that Mr Cunningham will do us the 
justice to believe that our opinion that the in- 
heritance of acquired characters does not play 
an important part in the evolution of, at any 
rate, the higher animals, is based, not on the 
ground of a priori reasoning, but on facts. 
All the evidence seems to show that such 
characteristics are not inherited. If, as Mr 
Cunningham thinks, all secondary sexual 
characters are due to the inheritance of the 
effects of use, etc., how is it that no Neo- 
Lamarckian is able to bring forward a clear 
case of the inheritance of a well-defined acquired 
character ? If such characteristics are habitually 
inherited, countless examples should be forth- 
coming. Fanciers in their endeavours are con- 
stantly "doctoring" the animals they keep for 
show purposes ; and it seems to us certain that 
if acquired characters are inherited, breeders 
would long ago have discovered this and acted 
upon the discovery. If Neo-Darwinians are 


Inheritance of Acquired Characters 

charged with refusing to believe that acquired 
characters are inherited because they ''cannot 
conceive the means by which it could be effected/ 
may it not be said with equal justice that many 
Neo-Lamarckians believe that acquired char- 
acters are inherited, not on evidence thereof, 
but because if such characters are not inherited 
it is very difficult to account for many of the 
phenomena presented by the organic world ? 

In many of the lower animals, as, for example, 
the hydra, the germinal material is diffused through 
the organism, so that a complete individual can 
be developed from a small portion of the creature. 
In such circumstances it seems not improbable 
that the external environment may act directly 
on the germinal substance, and induce changes 
in it which may perhaps be transmitted to the 
offspring. If this be so, it would seem that 
some acquired characters may be inherited in 
such organisms. Very many plants can be 
propagated from cuttings, buds, etc., so that we 
might reasonably expect some acquired characters 
to be hereditary in them. The majority of 
botanists appear to hold Lamarckian views ; but 
on the evidence at present available, it is doubtful 
whether such views are the correct ones. 

Plants are so plastic, so protean, so sensitive 
to their environment that their external structure 
appears to be determined by the external con- 
ditions in which they find themselves quite as 


The Making of Species 

much as by their inherited tendencies. In this 
respect they differ very considerably from the 
higher animals. The peacock, for example, 
presents the same outward appearance^ whether 
bred and reared in Asia or Europe, in a hot or 
cold, a damp or a dry climate. The same plant, 
on the other hand, differs greatly in outward 
appearance according as it is grown in a dry or a 
damp soil, a hot or a cold country. In his recent 
book The Heredity of Acquired Characters in 
Plants, the Rev. G. Henslow cites several 
examples of the celerity with which plants react to 
their environment. On page 32 he writes : *' The 
following is an experiment I made with the 
common rest-harrow (Ononis spinosa, L.) growing 
wild in a very dry situation by a roadside. I 
collected some seeds, and also took cuttings. 
These I planted in a garden border, keeping this 
well moist with a hand-light over it, and a saucer 
of water, so that the air should be thoroughly 
moist as well. Its natural conditions were thus 
completely reversed. They all grew vigorously. 
The new branches of the first year's growth bore 
spines, proving their hereditary character, but 
instead of their being long and stout, they were 
not an inch long, and like needles. This proved 
the spines to be a hereditary feature. In the second 
year there were none at all ; moreover, the plants 

^ The white, pied, and " Japan " individuals are not more dififerent 
from the type than some variations occurring in wild birds. 


Inheritance of Acquired Characters 

blossomed, and, taken altogether, there was no 
appreciable difference from O. repens, LT 

From this experiment Professor Henslow draws 
the inference that acquired characters tend to be 
inherited in plants. In our opinion the ex- 
periment affords strong evidence against the 
Lamarckian doctrine. Here we have a plant 
which has, perhaps, for thousands of generations 
developed spines owing to its dry environment. 
If acquired characters are inherited we should 
have expected this spiny character to have 
become fixed and persisted under changed 
conditions, for some generations at any rate. 
But what do we find ? By the second year the 
thorns have entirely disappeared. All the years 
during which the plant was exposed to a dry en- 
vironment have left no stamp upon it. The fact 
that the new branches of the first year's growth 
bore small spines is not, as Professor Henslow 
asserts, proof of their hereditary character. It 
merely shows that the initial stimulus to their 
development occurred while the plant was still in 
its dry surroundings. 

In the same way all other so-called proofs of the 
heredity of acquired characters break down when 
critically examined. 

In our opinion '* not proven " is the proper 
verdict on the question of the possibility of the 
inheritance of acquired characters in the higher 
animals. One thing is certain, and that is that 


The Making of Species 

acquired characters are not commonly Inherited 
in those organisms in which there is a sharp 
distinction between the germinal and the somatic 

It is nothing short of a misfortune that 
Haeckel's History of Creation^ which seems to 
be so widely read in England, should be built 
on a fallacious foundation. It seems to us that 
this work is calculated to mislead rather than to 

Our attitude is not quite that of the Wallaceian 
school, which denies the possibility of the in- 
heritance of acquired characters. In practice, 
however, the attitude we adopt is as fatal to 
Lamarckism in all its forms as the dogmatic 
assertions of the Wallaceians. It matters not 
whether acquired characters are very rarely or 
never inherited. In either case their inherit- 
ance cannot have played an important part in 
evolution. All those theories which rely on use- 
inheritance as a factor in evolution are therefore 
in our opinion worthless, being opposed to facts. 
Our attitude, then, is that the inheritance of 
acquired characteristics, if it does occur, is so 
rare as to be a negligible quantity in organic 

We may add that the position which we occupy 
will not be affected even if the Lamarckians do 
succeed eventually in proving that some acquired 
gharacters are really inherited. Such proof would 


The Wallaceian School 

merely help to elucidate some of the problems 
which confront the biologist. Thus the question 
of the inheritance of acquired characters, while 
full of interest, has no very important bearing 
on the question of the making of species. 

The Wallaceians hold the doctrines which 
have been set forth above as those of the Neo- 
Darwinian school. It is incorrect to call those 
who pin their faith to the all-sufficiency of natural 
selection Neo-Darwinians, because Darwin at no 
time believed that natural selection explained 
everything. Darwin moreover was a Lamarckian 
to the extent that he was inclined to think that 
acquired characteristics could be inherited. His 
theory of inheritance by gemmules involved the 
assumption that such characters are inherited. 
It is Wallace who out- Dar wins Darwin, who 
preaches the all-sufficiency of natural selection. 
For this reason we dub the school which holds 
this article of belief, and to which Weismann, 
Poulton, and apparently Ray Lankester belong, 
the Wallaceian school. Weismann has put forth 
a theory of inheritance, that of the continuity 
of the germ plasm, which makes this inheritance 
a physical impossibility. We believe that the 
Wallaceians have erred as far from the truth as 
the Lamarckians have, because, as we shall show 
hereafter, a great many of the organs and struc- 
tures displayed by organisms cannot be explained 
on the natural selection hypothesis. Those who 


The Making of Species 

pin their faith to this, needlessly increase the 
difficulty of the problem which they have to 

There remains the third school, to which we 
belong, and of which Bateson, De Vries, Kellog 
and T. H. Morgan appear to be adherents. This 
school steers a course between the Scylla of use- 
inheritance and the Charybdis of the all-sufficiency 
of natural selection. It may seem surprising to 
some that we should class De Vries as a Neo- 
Darwinian, seeing that he is the originator of the 
theory of evolution by means of mutations, which 
we shall discuss in Chapter III. of this work. 
As a matter of fact the theory of mutations should 
be regarded, not as opposed to the theory of 
Darwin, but as a theory engrafted upon it. De 
Vries himself writes : — " My work claims to be in 
full accord with the principles laid down by 
Darwin." Similarly Hubrecht writes in the 
Contemporary Review for November 1908 : 
*' Paradoxical as it may sound, I am willing to 
show that my colleague, Hugo de Vries, of 
Amsterdam, who a few years ago grafted his 
Mutations Theorie on the thriving and very 
healthy plant of Darwinism, is a much more 
staunch Darwinian than either Dr Wallace him- 
self, or the two great authorities in biological 
science whom he mentions. Sir William 
Thistleton Dyer and Professor Poulton." 

Having classified ourselves, it remains for us 


Complexity of the Problem 

(the authors of the present work) to define our 
position more precisely. Like Darwin we wel- 
come all factors which appear to be capable of 
effecting evolution. We have no axe to grind in 
the shape of a pet hypothesis, and consequently 
our passions are not roused when men come 
forward with new ideas seemingly opposed to 
some which already occupy the field. We re- 
cognise the extreme complexity of the problems 
that confront us. We look facts in the face 
and decline to ignore any, no matter how ill 
they fit in with existing theories. We recognise 
the strength and the weakness of the Darwinian 
theory. We see plainly that it has the defect of 
the period in which it was enunciated. The 
eighteenth century was the age of cocksureness, 
the age in which all phenomena were thought to 
be capable of simple explanation. 

This is well exemplified by the doctrines of 
the Manchester school as regards political and 
economic science. The whole art of legislation 
was thought to be summed up in the words 
laissez faire. The whole sphere of legitimate 
government was asserted to be the keeping of 
order and the enforcing of contracts. Experience 
has demonstrated that a State guided solely by 
these principles is wretchedly governed. A large 
proportion of recent Acts of Parliament limits the 
freedom of contract. Such limitations are neces- 
sary in the case of contracts between the weak and 


The Making of Species 

the strong. Similarly the earlier economists con- 
sidered political economy a very simple affair. 
They asserted that men are actuated by but 
one motive — the love of money. All their men 
were economic men, men devoid of all attri- 
butes save an intense love of gold. Experience 
has shown that these premises are not correct. 
Love of family, pride of race, caste prejudices 
are more or less deeply implanted in men, so 
that they are rarely actuated solely by the love 
of money. 

Thus it is that the political economy of to-day 
as set forth by Marshall is far more complex and 
less dogmatic than that of Ricardo or Adam 
Smith. Similarly the political philosophy of 
Sidgwick is very different to that of Herbert 
Spencer. So is it with the theory of organic 
evolution. The theory of natural selection is no 
more able to explain all the varied phenomena 
of nature than is Ricardo's assumption that all 
men are actuated solely by the love of money 
capable of accounting for the multifarious existing 
economic phenomena. Even as the love of wealth 
is an important motive of human actions, so is 
natural selection an important factor in evolution. 
But even as the majority of human actions are 
the resultant of a variety of motives, so are the 
majority of existing organisms the resultant of 
a complex system of forces. Even as it is the 
duty of the economist to discover the various 


The Aim of the Biologist 

motives which lead to human actions, so is it 
the duty of the biologist to bring to light the 
factors which are operative in the making of 




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 — Objec- 
tions which strike at root of Theory are based on mis- 
conception — 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. 

THE burden of proof is on him who 
asserts " is a rule of evidence 
which the man of science should 
apply as rigidly as does the lawyer. 
It is therefore incumbent upon us to prove our 
assertion that the theory of natural selection 
does not afford an adequate explanation of all 
the varied phenomena observed in the organic 


Theory of Natural Selection 

The theory of natural selection is so generally 
understood, that to set it forth in detail in this 
place would be quite superfluous. 

Darwin, it will be remembered, based his 
great hypothesis on the following observed 
facts : — 

1. No two individuals of a species are exactly 
alike. This is sometimes called the law of 

2. All creatures tend in a general way to 
resemble their parents in appearance more 
closely than they resemble individuals not re- 
lated to them. This may be termed the law of 

3. Each pair of organisms produces in the 
course of a lifetime, on an average, many more 
than two young ones. 

4. On an average the total number of each 
species remains stationary. 

From (3) and (4) follows the doctrine of 
Malthus, namely, that many more individuals 
are born than can reach maturity. 

Darwin applied this doctrine to the whole of 
the animal and the vegetable kingdoms. 

In his introduction to The Origin of Species 
he writes : — " 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 pro- 


The Making of Species 

fitable to itself, under the complex and some- 
times varying conditions of life, will have a 
better chance of surviving, and thus be naturally 
selected. From the strong principle of inherit- 
ance, any selected variety will tend to propagate 
its new and modified form." 

In other words, the struggle for existence 
amongst all organic beings throughout the world, 
which inevitably follows from the high geometri- 
cal ratio of their increase, results in the survival 
of the fittest, that is to say, of those best adapted 
to cope with their enemies and to secure their 
food. Since organisms are thus naturally selected 
in nature, we may speak of a natural selection 
which acts in much the same way as the human 
breeder does. Darwin's theory, then, is that all 
the variety of organisms which now exist have 
been evolved from one or more forms by this 
process of natural selection. 

The objections which have been urged against 
the theory of natural selection fall into two 

I. Those which strike at its root, which either 
deny that there is any natural selection, or 
declare that it is not capable of producing a 
new species. 

II. Those which are directed against the all- 
sufficiency of natural selection to account for 
organic evolution. 

Those of the first class need not detain us 


Various Anti-Darwinian Views 

long, although among those who formulate 
them are to be found some eminent men of 

Delage alleges that selection is powerless to form 
species, its function is, according to him, limited 
to the suppression of variations radically bad, 
and to the maintaining of a species in its normal 
character. It is thus an inimical factor in evolu- 
tion, a retarder rather than an accelerator of 
species-change. It merely acts by preserving 
the type at the expense of the variants, and so 
acts as a brake on evolution. 

Korschinsky, while possibly not denying that 
selection occurs in nature, declares that its 
influence on evolution is nil, or, if it has any 
influence, that it is a hindering one. 

Eimer similarly denies any capacity on the 
part of natural selection to create species. 

Pfeffer urges a very different objection. He 
says that if such a force as natural selection 
existed it would transform species much more 
rapidly than it does ! 

Now, in order that the above objections can 
carry any weight, one of two sets of conditions 
must be fulfilled. 

Either all organisms must be perfectly adapted 
to their environment, and this environment must 
never change, or there must be inherent in each 
species a kind of growth-force which impels 
the species to develop in certain fixed directions, 
c 33 

The Making of Species 

In either of these circumstances natural selection 
will be an inhibitory force, for if the normal 
organism is perfectly adapted to its environment, 
all variations from the type must be unfavour- 
able, and natural selection will weed out the 
individuals that display them. No careful 
student of nature can maintain, either that all 
animals are perfectly adapted to their environ- 
ment, or that this never changes. Hence those 
who deny that natural selection is a factor in the 
making of species, assume the second set of con- 
ditions, that species develop in certain fixed 
directions, being impelled either by internal or 
external forces. How far these ideas are founded 
on fact we shall endeavour to determine when 
speaking of variation. It must suffice at present 
to say that even if any of these views of ortho- 
genesis be established, natural selection will have, 
so to speak, a casting vote, it will decide which 
series of species developing along preordained 
lines shall survive and which shall not survive. 

Thus we reach by a different line of argument 
the conclusion we arrived at in the last chapter : 
V namely, there is no room for doubt that natural 
5 selection is a factor in the making of species. 

We must now pass on to the second class of 
objections, those which are urged against the all- 
sufficiency of natural selection. So numerous 
are these that it is not feasible to consider them 
all. A brief notice of the more important ones 


Darwinism does not explain Variation 

should suffice to satisfy any unbiassed person ; 
firstly, that natural selection is an important 
factor in evolution ; secondly, that the position 
taken up by Wallace and his followers, that 
natural selection, acting on minute variations, 
is the one and only factor in organic evolution, 
is untenable. 

1. It has been urged that the Darwinian 
theory makes no attempt to explain variation, 
and that, until we know what it is that causes 
variations, we are not in a position to explain 
evolution. This of course is quite true, but the 
objection is scarcely a fair one, since, as we have 
seen, Darwin freely admitted that his theory 
made no attempt to explain the origin of varia- 
tions. It is not reasonable to object to a theory 
because it fails to explain phenomena with which 
it expressly states that it is not concerned. On 
the other hand, the objection is one that must be 
reckoned with, for, as we shall see, it makes a 
great difference to the importance of natural 
selection as a factor in evolution if variations 
appear indiscriminately in all directions, as 
Darwin tacitly assumed they do, or whether, 
as some biologists believe, they are determinate 
in direction, being the result of a growth-force 
inherent in all organisms. 

2. Very similar to the above-mentioned objec- 
tion is that which points out that it is a long 
journey from Amoeba to man. It is difficult to 


The Making of Species 

believe that this long course of development from 
the simple to the complex is due to the action 
of a blind force, to the survival of those whose 
fortuitous variations happen to be best adapted 
to the environment. The result seems out of 
all proportion to the cause. There must be some 
potent force inherent in protoplasm, or behind 
organisms, impelling them upwards. This objec- 
tion is as difficult to refute as it is to establish. 
It is purely speculative. 

3. A very serious objection to the Darwinian 
theory is that the beginnings of new organs 
cannot be explained by the action of natural 
selection on fortuitous minute variations, and 
natural selection can act on an organ only when 
that organ has attained sufficient size to be of 
practical utility to its possessor. When once 
an organ has come into being it is not difficult 
to understand how it can be improved, modified 
and developed by natural selection. But how 
can we explain the origin of an organ such as 
a limb by the action of natural selection on 
minute variations ? 

The theory of the change of function goes 
some way towards meeting the difficulty, for by 
means of it we are able to understand how certain 
organs, as, for example, the lung of air-breathing 
animals, might have come into existence. This 
is said to have been developed from the 
swimming-bladder of fishes. This bladder is, 


Theory of Change of Function 

to use the words of Milnes Marshall, '* a closed 
sac lying just underneath the vertebral column. 
In many fish it acquires a connection by a duct 
with some part of the alimentary canal. It then 
becomes an accessory breathing organ, especially 
in those fish which are capable of living out of 
water for a time, e.g, the Protopterus of America. 
An interesting series of modifications exists con- 
necting the air-bladder with the lung of the 
higher vertebrates, which is undoubtedly the 
same organ." 

This theory, however, does not seem adequate 
to explain the origin of all organs. It does 
not explain, for example, how limbs developed 
in a limbless organism. Wallace tried to 
avoid the difficulty by asserting that it is un- 
reasonable to ask a new theory that it shall 
reveal to us exactly what took place in remote 
geological ages and how it took place. To this 
the obvious reply is, firstly, that we ought not 
to ^wf^ unqualified acceptance to any theory of 
evolution until it does afford us such explana- 
tions, and, secondly, that the theory of the origin 
of species by means of natural selection is no 
longer a new one. 

Latterly, however, Wallace appears to have 
given up all hope of being able to account for 
the origin of new organs by means of natural 
selection, for he states on page 431 of the issue 
of the Fortnightly Review for March 1909 : 


The Making of Species 

*' It follows — not as a theory but as a fact — that 
whenever an advantageous variation is needed, 
it can only consist in an increase or decrease of 
some power or faculty already existing." Now, 
in order for an increase or decrease to occur, 
there must be something in existence to be 
increased or diminished. Wallace, it is true, 
speaks here only of powers and faculties ; but 
it can scarcely be supposed that he believes that 
variations as to structure are intrinsically different 
from those relating to powers and faculties. 

4. Herbert Spencer urges, as an objection to 
the theory of natural selection, that favourable 
variations in one organ are likely to be counter- 
balanced by unfavourable variations in some 
other organ. He maintains that the chances are 
enormous against the occurrence of the '* many 
coincident and co-ordinated variations " that are 
necessary to create a life or death determining 

This objection was urged by a writer in the 
Edinburgh Revieysr in January 1909, and even 
by Wallace himself in the Fortnightly Review 
last March against the mutation theory. This 
objection, strong though it appears on paper, 
exists only in the imagination of the objector. 

Those who urge it display a misunderstanding 
of the manner in which natural selection acts, and 
ignorance of the phenomenon of the correlation 
of organs. 



Natural selection deals with an organism as a 
whole. Its effect is to permit those creatures to 
survive which, taken as a whole, are best adapted 
to their environment. 

Physiologists insist with ever-increasing em- 
phasis that there is more or less correlation and 
inter-connection between the various parts of an 

The several organs of an animal are not so 
many isolated units. It is impossible to act on 
one organ without affecting some or all of the 

Variations in a given direction of one organ 
are usually accompanied by correlated variations 
in some of the other organs. If strength be of 
paramount importance to an animal, natural 
selection will tend to preserve those individuals 
which exhibit strength to a marked degree, and 
this exhibition of strength may be accompanied 
by other peculiarities, such as short legs or a 
certain colour, so that natural selection will 
indirectly tend to produce individuals with short 
legs and having the colour in question, and it 
may happen that this particular colour is one 
that renders the animal more conspicuous than 
the normal colour does. Nevertheless, on account 
of the all-needful strength which accompanies it, 
those animals so coloured may survive while 
those of a more protective hue perish. Thus, 
paradoxical though it seems, natural selection 


The Making of Species 

may indirectly be responsible for characteristics 
which in themselves are injurious to the in- 
dividual. This is probably the case as regards 
the decorative plumage of some male birds. 
The phenomenon of correlation was recognised 
by Darwin, and has, we believe, played an 
important part in the making of species. We 
shall deal more fully with the subject in a later 

5. An oft-urged objection to the theory of natural 
selection, and one which weighed very strongly 
with Huxley, is that breeders have hitherto not 
succeeded in breeding a variety which is infertile 
with the parent species. If, Huxley asked, 
breeders cannot produce such a thing, how 
can we say we consider it proved that natural 
selection produces new species in nature? This 
objection, however, loses much of its force in 
view of the fact that many perfectly distinct 
species are quite fertile when bred together. We 
shall recur to this in Chapter IV. 

6. The fact that palaeontology has hitherto failed 
to yield links connecting many existing species is 
a classical objection to the theory of the origin 
of species by gradual evolution. 

Wallace states this objection as follows, on 
page 376 of his Darwinism : '' Many of the 
gaps that still remain are so vast that it seems 
incredible to these writers that they could ever 
have been filled up by a close succession of 


Missing Links 

species, since these must have been spread over 
so many ages, and have existed in such numbers, 
that it seems impossible to account for their total 
absence from deposits in which great numbers of 
species belonging to other groups are preserved 
and have been discovered." 

Wallace's reply is to the effect that in the case 
of many species palaeontology affords abundant 
evidence of the gradual change of one species into 
another, the foot of the horse being a well-known 
case. The genealogy of this noble quadruped 
can be traced from the Eocene four-toed Orohip- 
pus, through the Mesokippus, the Miokippus, the 
Protohippus, and the Pliohippiis, until we reach 
the one-toed Equus. 

Wallace further points out that in order that 
the fossil of any organism may be preserved, the 
'^ concurrence of a number of favourable condi- 
tions " is required, and against this the chances 
are enormous. Lastly, he urges the imperfection 
of our knowledge of the things that lie embedded 
in the earth's crust. 

The objection based on the lack of ^'missing 
links " loses some of its force if we accept the 
theory that species sometimes arise as sports. 
Thus, suppose a species with well-developed 
horns produces as a mutation a hornless variety, 
which eventually replaces the horned form, we 
should look in vain for any forms intermediate 
between the parent and the daughter species. 


The Making of Species 

On the other hand, it is significant that just 
where the links are most needed they are missing. 
For example, the splint bones of the horse, taken 
in conjunction with the feet of existing tapirs, 
which have four toes in front and three behind, 
would have led us to infer, without the help of 
the geological record, that the horse was a 
descendant of a polydactyle ancestor. When, 
however, we come to the origin of birds, bats, 
and whales, palaeontology fails to give us any 
assistance, so that we are in the dark as to the 
origin of such really important modifications. 

7. The swamping effects of inter-crossing is 
an objection which has been repeatedly urged 
against the Darwinian theory. 

This objection is not so serious as it appears 
at first sight. Darwin and Wallace maintain, 
firstly, that natural selection acts by eliminating all 
individuals except those which present favourable 
variations. The favoured few alone survive and 
mate with one another, so that there is here no 
question of the swamping effects of inter-crossing, 
none but well-adapted individuals being left 
to mate with one another. 

The objection gains greater force when directed 
against the theory that evolution proceeds by 
sudden jumps. But in this connection we must 
bear in mind that the experiments of Mendel 
and his followers have demonstrated that some 
of the offspring of crosses may resemble their 


Recurrent Mutations 

pure ancestors and breed true inter se. Nor is 
this all. 

Experience shows that where a mutation, or 
sport, or discontinuous variation occurs, it fre- 
quently repeats itself; for example, the black- 
winged sport of the peafowl has occurred several 
times over and in different flocks of birds. The 
sport or mutation must have a definite cause. 
There must be something within the organism, 
something in the generative cells, which causes 
the mutation to arise ; and hence, on a priori 
grounds, we should expect the same mutation to 
arise about the same time in many individuals. 
It seems legitimate to infer that things have 
been quietly working up to a climax. When 
this is reached there results a mutation. There- 
fore we should expect sudden mutations to appear 
simultaneously in a number of individuals. To 
this important subject we shall return. 

8. An almost insuperable objection to the 
theory that species have originated by the action 
of natural selection on minute variations, is that 
such small differences cannot be of a life-or-death 
value, or, as it is usually called, a survival value 
to their possessor. But if evolution is the result 
of the preservation by natural selection of such 
slight variations, it is absolutely necessary that 
each of these should possess a survival value. 

As D. Dewar has pointed out, on page 704 of 
vol. ii. of The Albany Review, it is only when the 


r .'•. 


The Making of Species 

beast of prey and its victim are evenly matched 
as regards fleetness and power of endurance that 
small variations in these qualities can have a 
survival value. But in the rough and tumble 
of the struggle for existence the victim and its 
foe are but rarely well-matched. Take as an 
example the case of a flycatcher. " This bird," 
writes D. Dewar, *'will sometimes take three 
or four insects in the course of one flight ; all 
are captured with the same ease, although the 
length of wing in each victim varies. So great 
is the superiority of the bird that it does not 
notice the difference in the flying powers of its 
puny quarry." It is unnecessary to labour this 

9. Species or varieties differing considerably 
in colour may exist side by side, as the hooded 
and carrion crows, the white and dark breasted 
forms of the Arctic skua, the pale and dark forms 
of the fulmar petrel, the grey and rufous forms of 
the American scops owl [Megascops asid). 

It is true that preponderance of one form or 
another in certain districts points to some advan- 
tage possessed by one over the other, but, for 
all we know, it may be due to heredity, and in 
any case the co-existence of the two types in part 
of their range, or at certain seasons, shows that 
selection is not at all rigorous. 

The same argument applies to the co-existence 
of very differently-coloured species with generally 



similar habits, such as that of the jaguar and 
puma in South America, and the five very 
differently-coloured flycatchers in the Nilgiri 

In short, there is abundant evidence to show 

that considerable differences in colour do not 

appear to have any effect on the chances of 

survival in the struggle for existence of those 

that display them. Yet this is precisely what the 

supporters of the Darwinian hypothesis cannot 

afford to admit, for they then find it impossible 

to account for the origin of such a form as 

Kallima, the leaf-butterfly, by the action of 

natural selection. As most people are aware, 

this creature displays a remarkable resemblance 

to a decaying leaf *' These butterflies " (there 

are several species which show the marvellous 

imitation), writes Kellog, on page 53 oi Darwinism 

To-day, "have the under sides of both fore and 

hind wings so coloured and streaked that when 

apposed over the back in the manner common 

to butterflies at rest, the four wings combine to 

resemble with absurd fidelity a dead leaf still 

attached by a short petiole to the twig or branch. 

I say absurd, for it seems to me the resemblance 

is over-refined. Here for safety's sake it is no 

question of mimicking some one particular kind 

of other organism or inanimate thing in nature 

which birds do not molest. It is simply to 

produce the effect of a dead leaf on a branch. 


The Making of Species 

Leaf-shape and general dead-leaf colour-scheme 
are necessary for this illusion. But are these 
following things necessary ? namely, an extra- 
ordinarily faithful representation of mid-rib and 
lateral veins, even to faint microscopically-tapering 
vein tips ; a perfect short petiole produced by the 
apposed * tails ' of the hind-wings ; a conceal- 
ment of the head of the butterfly so that it shall 
not mar the outlines of the lateral margin of the 
leaf ; and finally, delicate little flakes of purplish 
or yellowish brown to mimic spots of decay and 
fungus-attacked spots in the leaf ! And, as culmin- 
ation, a tiny circular clear spot in the fore-wings 
(terminal part of the leaf) which shall represent 
a worm-eaten hole, or a piercing of the dry leaf 
by flying splinter, or the complete decay of a 
little spot due to fungus growth ! A general 
and sufficient seeming of a dead leaf, object of no 
bird's active interest, yes, but not a dead leaf 
modelled with the fidelity of the waxworkers in 
the modern natural history museums. When 
natural selection has got Kallima along to that 
highly desirable stage when it was so like a dead 
leaf in general seeming that every bird sweeping 
by saw it only as a brown leaf clinging pre- 
cariously to a half-stripped branch, it was natural 
selection's bounden duty, in conformance to its 
obligations to its makers, to stop the further 
modelling of Kallima and just hold it up to its 
hardly won advantage. But what happens ? 


A Dilemma 

Kallima continues its way, specifically and ab- 
surdly dead-leafwards, until to-day it is a much 
too fragile thing to be otherwise than very 
gingerly handled by its rather anxious foster- 
parents, the Neo- Darwinian selectionists." It 
is obvious that if natural selection has produced 
so highly specialised an organism as the dead- 
leaf butterfly, every minute variation must be of 
value and have been seized upon by natural 

Thus the Wallaceians are on the horns of a 
dilemma. If they assert, as they appear to do, 
that every infinitesimal variation has a survival 
value, they find it difficult to explain the exist- 
ence, side by side of such forms as the hooded and 
carrion crows, to say why in some species of bird 
both sexes assume a conspicuous nuptial plumage 
at the very time when they stand most in need 
of protective coloration, why the cock paradise 
flycatcher is chestnut for the first two years of 
his life and then turns as white as snow. If, on 
the other hand, the Wallaceians assert that small 
variations are unimportant and have no survival 
they are, as Kellog points out, in trouble over 
the close and detailed resemblance which the 
Kallima butterflies bear to dead leaves. 

lo. An objection to the Darwinian theory which 
has been advanced by Conn, Henslow, D. Dewar, 
and others, is that the selection theory fails to 
take into account the effects of chance. *' If," 


The Making of Species 

writes D. Dewar on page 707 of The Albany 
Review^ vol. ii., ''the struggle for existence were 
of the nature of a race at a well-regulated athletic 
meeting, where the competitors are given a fair 
start, where there is no difference in the condi- 
tions to which the various runners are subjected, 
then indeed would every variation tell. I would 
rather liken the struggle for existence to the rush 
to get out of a crowded theatre, poorly provided 
with exits, when an alarm of fire is given. The 
people to escape are not necessarily the strongest 
of those present. Propinquity to a door may be 
a more valuable asset than strength." 

Or again, we may take the imaginary case of 
some antelopes being pursued by wolves. The 
chase, being prolonged, brings the antelopes to a 
locality with which they are not familiar. The 
foremost of the herd, the most swift, and there- 
fore the individual which should stand the best 
chance of survival, suddenly finds himself on soft 
boggy ground, which, owing to the depth to 
which his feet sink into the soil, seriously 
impedes his progress. His fellow antelopes, 
now outdistanced, seeing his predicament, take 
another course and soon leave him behind, to 
fall an easy prey to his foes. Here we have a 
case of the perishing of the most fit as regards 
the important point of speed. 

Writing of plants, Professor Henslow says, on 
page 16 of The Heredity of Acquired Characters 


The Effects of Chance 

in Plants : *' As the whole of the animal kingdom 
ultimately lives upon the vegetable, plants must 
supply the entire quantity of food supplied, not 
to add innumerable vegetable parasites as well, 
for both young and old. Myriads of germinating 
seeds perish accordingly, being destroyed by slugs 
and other mollusca, and 'mildews,' etc. But far 
more seeds and spores — about 50,000,000 of 
these it is calculated can be borne in a single 
male-fern — never germinate at all. They fall 
where the conditions of life are unfavourable 
and perish. This misfortune is not due to 
any inadaptiveness in themselves, but to the 
surrounding conditions which will not let them 
germinate. Thus thousands of acorns and other 
fruits, as of elder, drop upon the ground in and 
by our hedges, road-sides, copses, and elsewhere ; 
but scarcely any or even no seedlings are to be 
seen round the trees." 

Every year thousands of birds perish in the 
great migratory flight, others succumb in a 
cyclone, a fierce tropical storm, a prolonged 
drought, a severe frost. Here death overtakes 
multitudes, all that dwell in a locality, the weak 
and the strong, the swift and the slow alike. 

This objection may be met by saying that in 
the long run it is the fittest that will survive. 
This is true. The objection is nevertheless of 
importance in showing how exceedingly uncertain 
must be the action of natural selection if it have but 
D 49 

The Making of Species 

small variations upon which to work. In such 
circumstances the mills of natural selection may 
grind surely, but they must grind very slowly. 

1 1 . We must bear in mind that the struggle for 
existence is most severe among young animals, 
among creatures that are not fully developed. 
Nature pays no attention to potentialities. The 
weak go to the wall in the conflict, even though, 
if allowed time, they might develop into prodigies 
of strength. 

Moreover, and this is an important point, death 
in the case of young creatures overtakes broods 
and families rather than individuals. 

The above-cited objections to the theory that 
species have originated by the action of natural 
selection on minute variations, are mostly of a 
general nature ; let us now notice briefly a few 
more concrete objections. We shall not devote 
much space to these in the present chapter, since 
we shall be continually confronted with them 
when dealing with the subject of animal colouring. 

12. Natural selection, as we shall see, fails to 
account for the origin of what is known as pro- 
tective mimicry. Some insects look like inanimate 
objects, others resemble other insects which are 
believed or known to be unpalatable. Those 
creatures displaying this resemblance to other 
objects or creatures, and deriving profit therefrom, 
are said to '' mimic " the objects or creatures 
they copy. They are also called " Mimics." 



The Origin of Mimicry ^ 

It is easy to understand the profit that these f^cy 

mimics derive from their mimicry. When once ^x/ 

the disguise has been assumed we can compre- x-X \k ^^ 

hend how natural selection will tend to improve ."'^ \> 

it by eliminating those that mimic badly ; but it \/.<- o ^ 
seems to us that the theory fails utterly to V ''vV u 
account for the origin of the likeness. J Ijr 

13. Similarly, the Neo- Darwinian theory fails to 
explain the colours of the eggs of birds laid in 
open nests, why, for example, the eggs of the 
accentor or hedge-sparrow are blue and those 
of the doves are white. 

14. The theory fails to give a satisfactory ex- 
planation of the phenomena of sexual dimorphism. 
Why, for example, in some species of doves and 
ducks, thesexes are alike, while in other species 
with similar habits they differ in appearance. 

15. It fails to explain why the rook is black and 
why the jackdaw has a grey neck. 

These and many other objections we shall 
deal with more fully in the chapter on animal 
colouration. It must suffice here to mention 
them, and to say that our experience teaches us 
that scarcely a single species of bird or beast 
exists which does not display some characteristic 
which is inexplicable on the theory that natural 
selection, acting on small variations, is the one 
and only cause of organic evolution. 




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 discon- 
tinuous 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 varia- 
tion " — Views held by De Vries — Distinction between con- 
tinuous 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. 

AS we have already seen, the Darwinian 
theory, unlike that of Lamarck, does 
not attempt to explain the origin of 
variations. It is content with the 
fact that variations do occur. 

Although Darwin did not try to explain how 
it is that variation occurs, and was very guarded 


Nature of Variation 

in the expressions he used concerning it, he 
assumed that variations are indefinite in variety 
and occur indiscriminately in all directions, as 
the following quotations from the Origin of 
Species will show : " But the number and diver- 
sity of inheritable deviations of structure . . . 
are endless" (page 14, ed. 1902). ''The varia- 
tions are supposed to be extremely slight, but of 
the most diversified nature." " I have hitherto 
sometimes spoken as if the variations so common 
and multiform with organic beings under domes- 
tication, and in a lesser degree to those under 
nature, were 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 " (page 1 64). 

Wallace is far less guarded in his expressions. 
On page 82 of his Da7'winis')n he speaks of " the 
constant and large amount of variation of every 
part in all directions . . . which must afford an 
ample supply of favourable variations whenever 

The double assumption that variations are for 
all practical purposes haphazard in origin and 
indefinite in direction is necessary if natural 
selection is to be the main factor in evolution, jj -K 
For if variations be not haphazard, if they are 
definite, if there be a directive force behind them, 
like fate behind the classical gods, then selection 
is not the fundamental cause of evolution. It 


The Making of Species 

can at most effect, not the origin of species, but 
the survival of certain species which have arisen 
as the result of some other force. Its position 
is changed ; it is no longer a cause of the origin 
of new organisms, but a sieve determining 
which of certain ready-made forms shall survive. 
Evidently, then, we shall not be able to fully 
understand the evolutionary process until we 
have discovered how it is that variations are 
caused. In other words, we must go considerably 
farther than Darwin attempted to do. 

Before proceeding to inquire into the true 
nature of variations, it behoves us to set forth 
briefly the ideas of Darwin on the subject. We 
shall then be in a position to see how much 
progress has been made since the days of that 
great biologist. 

It is not at all easy to discover exactly what 
were Darwin's views on the subject of variation. 
A perusal of his works reveals contradictions, 
and gives one the impression that he himself 
scarcely knew his own mind upon the subject. 
This should not be a matter for surprise. 

We must remember that Darwin had to do 
pioneer work, that he had to deal with alto- 
gether new conceptions. Such being the case, 
his ideas were of necessity somewhat hazy ; they 
underwent considerable modification as fresh 
facts came to his knowledge. 

Towards the end of his life Darwin recognised 


Definite and Indefinite Variability 


i M 

that variability is of two kinds — definite and 
indefinite. Indefinite variation is indiscriminate 
variation in all directions around a mean, varia- 
tion which obeys what we may perhaps call the 
law of chance. Definite variation is variation in 
a determinate direction — variation chiefly on one 
side of the mean. Darwin believed that these 
determinate variations were caused by external 
forces, and that they are inherited. He thus 
accepted Lamarckian factors. *' Each of the 
endless variations," he writes, " which we see in 
the plumage of our fowls, must have had some 
efficient cause, and if the same causes were to 
act uniformly during a long series of generations 
on many individuals, all probably would be 
modified in the same direction." 

But Darwin was always of opinion that this 
definite variability, this variability in one direc- 
tion as the result of some fixed cause, is far less 
important, from an evolutionary point of view, 
than indefinite variability, that it is the exception 
rather than the rule, that the usual result of 
changed conditions is to let loose a flood of 
indefinite variability, that it is almost exclusively 
upon this that natural selection acts. 

Darwin also recognised that variations differ 
in degree, even as they do in kind. He per- 
ceived that some variations are much more 
pronounced than others. He recognised the 
distinction between what are now known as 





The Making of Species 

continuous and discontinuous variations. The 
former are slight departures from the normal ; 
the latter are considerable deviations from the 
mean or mode ; great jumps, as it were, taken by 
nature, as, for example, the pea and the rose 
combs of fowls, which were derived from the 
normal single comb. 

" At long intervals of time," wrote Darwin, 
**out of millions of individuals reared in the 
same country and fed on nearly the same food, 
deviations of structure so strongly pronounced as 
to deserve to be called monstrosities arise, but 
monstrosities cannot be separated by any distinct 
line from slighter variations." Therefore it is 
evident that he regarded the difference between 
continuous and discontinuous variations as not 
one of kind, but merely of degree. To the 
discontinuous variations Darwin attached very 
little importance from an evolutionary point of 
view. He looked upon them as something 

"It may be doubted," he wrote, "whether 
such sudden and considerable deviations of 
structure such as we occasionally see in our 
domestic productions, more especially with plants, 
are ever permanently propagated in a state of 
nature. Almost every part of every organic 
being is so beautifully related to its complex 
conditions of life that it seems as improbable 
that any part should have been suddenly pro- 



duced perfect, as that a complex machine 
should have been invented by a man in a 
perfect state. Under domestication monstrosities 
sometimes occur which resemble normal struc- 
tures in widely different animals. Thus pigs 
have occasionally been born with a sort of 
proboscis, and if any wild species of the same 
genus had naturally possessed a proboscis, it 
might have been argued that this had appeared 
as a monstrosity; but I have as yet failed to 
find, after diligent search, cases of monstrosities 
resembling normal structures in nearly allied 
forms, and these alone bear on the question. If 
monstrous forms of this kind ever do appear in a 
state of nature and are capable of reproduction 
(which is not always the case), as they occur 
rarely and singly, their preservation would de- 
pend on unusually favourable circumstances. 
They would, also, during the first and succeeding 
generations cross with the ordinary form, and 
thus their abnormal character would almost 
inevitably be lost." But, in a later edition of the 
Origin of Species, Darwin seems to contradict 
the above assertion : " It should not, however, 
be overlooked that certain rather strongly marked 
variations, which no one would rank as mere 
individual differences, frequently recur owing to 
a similar organisation being similarly acted on — 
of which fact numerous instances could be given 
with our domestic productions. In such cases, 


The Making of Species 

if the varying individual did not actually trans- 
mit to its offspring its newly acquired char- 
acter, it would undoubtedly transmit to them, as 
long as the existing conditions remained the 
same, a still stronger tendency to vary in the 
same manner. There can also be little doubt 
that the tendency to vary in the same manner 
has often been so strong that all the individuals 
of the same species have been similarly modified 
without the aid of any form of selection. Or 
only a third, fifth, or tenth part of the indi- 
viduals may have been thus affected, of which 
fact several instances could be given. Thus 
Graba estimates that about one-fifth of the 
STuillemots in the Faroe islands consist of a 
variety so well marked, that it was formerly 
ranked as a distinct species under the name 
Uria lacryina7ts. In cases of this kind, if the 
variation were of a beneficial nature, the original 
form would soon be supplanted by the modified 
form, through the survival of the fittest." Here 
we seem to have a plain statement of the origin 
of new forms by mutation. 

Again, we read (page 34) : " Some variations 
useful to him [i.e. man) have probably arisen 
suddenly, or by one step ; many botanists, for 
instance, believe that the fuller's teasel, 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 


Minute Variations n^ 4 

arisen in a seedling. This is known to be the 
case with the turnspit dog."^ But, as we have 
already said, Darwin at no time attached much \ 

importance to these jumps made by nature as a 
factor in evolution. He pinned his faith to the 
minute, indefinite variations which he believed 
could be piled up, one upon another, so that, . 
if allowed sufficient time, either nature or the 
human breeder could, by a continued selection 
of these minute variations, call into being any 
kind of organism. The importance of selection, '' 
he writes, "consists in the great effect produced 
by the accumulation in one direction, during 
successive generations, of differences absolutely 
inappreciable by an uneducated eye " (page 36). 
On page 132 he writes: ** I can see no limit to 
the amount of change, to the beauty and com- 
plexity of the coadaptations between all organic 
beings . . , which may have been effected ^ in 
the long course of time by nature's power of 
selection." He expressly states, on page 149, 
that he sees no reason to limit the process to 
the formation of genera alone. 

Athough the theory of natural selection does 
not attempt to explain the causes of variation, 

^ This short-legged type of dog is sometimes seen among the 
ownerless and unselected pariah dogs of Indian towns ; and a short- 
legged variety of the fowl may occur sporadically in Zanzibar, 
where the long-legged Malay is the prevalent breed. 

2 " Effected " appears in the earlier editions, but in the later 
editions has given place to " affected," probably a printer's error. 


The Making of Species 

Darwin paid some attention to the subject. He 
believed that both internal and external causes 
contribute to variation, that variations tend to 
be inherited whether the result of causes within 
the organism or outside it. He believed that 
the inherited effect of use and disuse was a cause 
of variation, and cited, as examples, the lighter 
wing-bones and heavier leg-bones of the domestic 
duck and the drooping ears of some domestic 
animals. He supposed that animals showed a 
greater tendency to vary when under domestica- 
tion than when in their natural state, attributing 
the supposed greater variability to the excess 
of food received, and the changed conditions of 
the life of domestic animals. Nevertheless, he 
was fully alive to the fact that "nearly similar 
variations sometimes arise under, as far as we 
can judge, dissimilar conditions ; and, on the 
other hand, dissimilar variations arise under 
conditions which appear to be nearly uniform." 
In other words, the nature of organisms appeared 
to Darwin to be a more important factor in the 
origin of variations than external conditions. 
Evidence of this is afforded by the fact that 
some animals are more variable than others. 
Finally, he frankly admitted how great was his 
ignorance of the causes of variability. Varia- 
bility is, he stated, governed by unknown laws 
which are infinitely complex. 

It will be convenient to deal with each of 


Lines of Variation 

Darwin's main ideas on variation separately, 
and to consider to what extent they seem to 
require modification in the light of later research. 
Firstly, Darwin believed that variations arise 
in what appears to be a haphazard manner, that 
they occur in all directions, and seem to be 
governed by the same laws as chance. It is 
our belief that we are now in a position to make 
more definite statements regarding variation than 
Darwin was able to. 

Biologists can now assert definitely that varia- 
tions do not always occur equally in all directions. 
The results of many years of the efforts of practi- 
cal breeders demonstrate this. These men have 
not been able to produce a green horse, a pigeon 
with alternate black and white feathers in the tail, 
or a cat with a trunk, for the simple reason that 
the organisms upon which they operated do not 
happen to have varied in the required direction. 
It may perhaps be objected that breeders have 
no desire to produce such forms ; had they wished 
to do so, they would probably have succeeded. 
To this objection we may reply that they have 
not managed to produce many organisms, which 
would be highly desirable from a breeder's point 
of view, as, for example, a blue rose, hens that lay 
brown eggs but do not become broody at certain 
seasons of the year, or a cat that cannot scratch. 

As Mivart well says, on page 1 18 of his Genesis 
of Species y ** Not only does it appear that there are 


The Making of Species 

barriers which oppose change in certain directions, 
but that there are positive tendencies to develop- 
ment along certain special lines. In a bird which 
has been kept and studied like the pigeon, it is 
difficult to believe that any remarkable spontane- 
ous variations would pass unnoticed by breeders, 
or that they would not have been attended to and 
developed by some fancier or other. On the 
hypothesis of indefinite variability, it is then hard 
to say why pigeons with bills like toucans, or with 
certain feathers lengthened like those of trogons, 
or those of birds of paradise, have never been 

There are certain lines along which variation 
seems never to occur. Take the case of the tail 
of a bird. Variable though this organ be, there 
are certain kinds of tail that are seen neither in 
wild species nor domesticated races. A caudal 
appendage, of which the feathers are alternately 
coloured, occurs neither in wild species nor in arti- 
ficial breeds. For some reason or other, variations 
in this direction do not occur. Similarly, with the 
exception of one or two of the ''Noddy" terns, 
whenever a bird has any of its tail feathers con- 
siderably longer than the others, it is always the 
outer pair or the middle pair that are so elongated. 
It would thus appear that variations in which the 
other feathers are especially lengthened do not 
usually occur. The fact that they are elongated 
in two or three wild species is the more signifi- 


Breeders' Boasts 

cant, because it shows that there is apparently 
nothing inimical to the welfare of a species in 
having, say, the third pair of tail feathers from 
the middle exceptionally prolonged. 

This is a most important point, and one 
which seems to be ignored by the majority of 
scientific men, who appear to be misled by the 
boastful talk of certain successful breeders. 
Thus, on page 29 of the Origin of Species, 
Darwin quotes, with approval, Youatt's descrip- 
tion of selection as *'the magician's wand, by 
means of which he may summon into life what- 
ever form and mould he pleases." Darwin 
further cites Sir John Sebright as saying, with 
regard to pigeons, that he would '' produce any 
given feather in three years, but it would take 
him six years to obtain head and beak." 

If it were possible absolutely to originate any- 
thing by selection, horticulturists would almost 
certainly ere this have produced a pure black 
flower. The fact that not a single mammal 
exists, either in nature or under domestication, 
with scarlet, blue, or green in its hair, appears to 
show that, for some reason or other, mammals 
never vary in any of these directions. 

The fact that so few animals have developed 
prehensile tails seems to indicate that variation 
does not often occur in that direction, for 
obviously a prehensile tail is of the very greatest 
utility to its possessor ; so that there can be 


The Making of Species 

little room for doubt that it would be seized upon 
and preserved by natural selection, whenever it 

As E. H. Aitken very truly says, "so early 
and useful an invention should, one would think, 
have been spread widely in after time ; but 
there appears to be some difficulty in developing 
muscles at the thin end of a long tail, for the 
animals that have turned it into a grasping organ 
are few and are widely scattered. Examples 
are the chameleon among lizards, our own little 
harvest mouse, and, pre-eminent among all, the 
American monkeys" (Strand Magazine, Nov. 

Even as there are many variations which seem 
never to occur in nature, so are there others 
which occur so frequently that they may be 
looked for in any species. Albinistic forms 
appear now and again in almost every species 
of mammal or bird ; while melanistic sports, 
although not so common, are not by any means 

Every complete manual on poultry gives for 
each breed a note of the faults which constantly 
appear, and which the fancier has to watch care- 
fully for and guard against. The fact that these 
"faults" occur so frequently in each breed shows 
how strong is the tendency to vary in certain 
definite directions. It is true that some of these 
faults are in the nature of reversions, as, for 


Albinistic Variations 

example, the appearance of red hackles in the 
cocks of black breeds of poultry. On the other 
hand, some certainly are not reversions, such as 
the appearance of a white ring in the neck of the 
female of the Rouen duck, which should resemble 
the Mallard as regards the plumage of the neck. 
Again, the tendency of Buff Orpingtons to 
assume white in the wings and tail must be 
regarded as a variation which is not in the nature 
of a reversion. In short, the efforts of all 
breeders are largely directed to fighting against 
the tendencies which animals display towards 
variation in certain directions. 

This tendency to vary in the direction of 
whiteness may account for many of the white 
markings which occur in nature, as, for example, 
the white tails of the Sea Eagle {Haliaetus 
albicilla) the Nicobar Pigeon (Caloenas nico- 
barica), and many hornbills. Provided that such 
variations are not too great a handicap to their 
possessors in the struggle for existence, natural 
selection will allow them to persist. 

It was the belief of Linnaeus, based on experi- 
ence, that every blue or red-coloured flower is 
likely to produce a white variety, hence he held 
that it is not safe to trust to colour for the identi- 
fication of a botanical species. 

On the other hand, white flowers are not likely 
to produce red varieties, and we believe we may 
positively assert that they never produce a blue 
E 65 

The Making of Species 

sport. Similarly, white animals appear not to 
give rise to colour varieties. 

We are never surprised to find that an ordi- 
nary upright plant produces as a sport or muta- 
tion a pendulous, or fastigiate form. These 
aberrant varieties, be it noted, occur in species 
which belong to quite different orders. 

De Vries points out that laciniated leaves 
appear in such widely separated trees and shrubs 
as the walnut, the beech, the hazel-nut, and the 

Another example of the definiteness of varia- 
tion is furnished by what Grant Allen calls the 
" Law of Progressive Colouration " of flowers. 

On pp. 20, 21 of The Colours of Flowers, 
he writes, " All flowers, as we know, easily sport 
a little in colour. But the question is, do their 
changes tend to follow any regular and definite 
order? Is there any reason to believe that the 
modification runs from any one colour toward 
any other ? Apparently there is. . . . All 
flowers, it would seem, were in their earliest 
form yellow ; then some of them became white ; 
after that a few of them grew to be red or 
purple ; and finally a comparatively small number 
acquired the various shades of lilac, mauve, violet, 
or blue." 

So among animals there are many colour 
patterns and structures that appear in widely 
different genera, as, for example, the magpie 



colouring in birds. With this phenomenon we 
shall deal more fully when speaking of animal 
colouration. There is certainly no small amount 
of evidence which seems to indicate that, from 
some cause or other, an impetus has been given 
to certain organs to develop along definite lines, 
The reduction of the number of digits in several 
mammalian families which are not nearly related 
is a case in point. This phenomenon is, as 
Cope points out, observed in Marsupials, Rodents, 
Insectivores, Carnivores, and Ungulates. He, 
being a Lamarckian, ascribes this to the in- 
herited effects of use. Wallaceians attribute it 
solely to the action of natural selection. The 
assumption of a growth-force or tendency for the 
development of one digit at the expense of the 
others, would explain the phenomenon equally 
well. And it is significant that many palaeonto- 
logists are believers in some kind of a growth- 
force. In the case of certain extinct animals we 
seem to have examples of the over-development 
of organs. " Palaeontology," writes Kellog on 
p. 275 of his Darwinism To-day^ *' reveals to us 
the one-time existence of animals, of groups of 
animals, and of lines of descent, which have had 
characteristics which led to extinction. The un- 
wieldiness of the giant Cretaceous reptiles, the 
fixed habit of life of the crinoids, the coiling of 
the ammonities and the nautili, the gigantic 
antlers of the Irish stag — all these are examples 


The Making of Species 

of development along disadvantageous lines, or 
to disadvantageous degrees. The statistical 
studies of variation have made known numerous 
cases where the slight, as yet non-significant (in 
a life-and-death struggle) variation in pattern of 
insects, in dimensions of parts, in relative pro- 
portions of superficial non-active areas, are not 
fortuitous, that is, do not occur scattered evenly 
about a mean or mode according to the law of 
error, but show an obvious and consistent tendency 
to occur along certain lines, to accumulate in 
certain directions." 

It seems to us that the only proper attitude to 
adopt in the present state of our knowledge is, 
not to call in to our aid an unknown growth- 
force, but simply to say that there is evidence 
to show that variations frequently occur along 
certain definite lines only. 

Darwin's second assumption was that there is 
no limit to which variations may be accumulated 
in any direction ; that by adding one minute 
variation to another through countless generations 
new species, new genera, new families may arise. 
This assumption, if applied to continuous or 
fluctuating variations, seems opposed to facts. 
All the evidence available goes to show that 
there is a definite limit to which minute variations 
can be accumulated in any given direction. No 
one has succeeded in breeding a dog as large as 
a horse, or a pigeon with a beak as long as that 


speed of Racehorses 

of a snipe. In the case of racehorses, which 
have been selected so carefully through a long 
period of time, we seem to have reached the 
limit of speed which can be attained by the mul- 
tiplication of insignificant variations. We do not 
wish to dogmatise, but we believe that of late 
years there has not been any material increase 
in the speed of our racehorses. 

Mr S. Sidney says, on page 174 of CasselUs 
Book of the Horse : "" As far as form went ^pace 
Admiral Rous), the British racehorse had reached 
perfection in 1770, when * Eclipse' was six years 
old." He quotes the measurements of the 
skeleton of "Eclipse" in the Museum of the 
Royal College of Surgeons as evidence of this. 
All the efforts of breeders, then, have failed 
appreciably to improve the form of the British 
racehorse in the course of over a century and 
a quarter. 

De Vries has made some important experi- 
ments with a view to determining whether or 
not there is a limit to the amount of change 
which can be induced by the selection of 
fluctuating or continuous variations as opposed 
to mutations. *' I accidentally found," he writes, 
on page 345 of Species and Varieties : their 
Origin by Mutation, " two individuals of the 
* five-leaved ' race (of clover) ; by transplanting 
them into my garden I have isolated them and 
kept them free from cross-fertilisation with the 


The Making of Species 

ordinary type. Moreover, I brought them under 
such conditions as are necessary for the full 
development of their character ; and last, but 
not least, I have tried to improve their char- 
acter as far as possible by a very rigid and 
careful selection. . . . By this method I 
brought my strain within two years up to an 
average of nearly 90 per cent, of the seedlings 
with a divided primary leaf (such seedlings 
averaging five leaves in the adult). . . . This 
condition was reached by the sixth generation 
in the year 1894, ^^^ has since proved to be the 
limit, the figures remaining practically the same 
through all the succeeding generations. ... I 
have cultivated a new generation of this race 
nearly every year since 1894, using always the 
strictest selection. This has led to a uniform 
type, but has not been adequate to produce 
further improvement." Similarly, De Vries 
found in the bulbous buttercup {^Ranunculus 
bulbosus) 2l strain varying largely in the 
number of petals ; therefore he tried by 
means of continuous selection of those flowers 
having the largest number of petals to pro- 
duce a double flower, but was not able to do so. 
He succeeded in evolving a strain with an 
average number of nine petals, some individuals 
having as many as twenty or thirty ; but even 
by breeding only from these last he could not 

increase the average number of petals in any 


Experiments of De Vries 

generation beyond nine. This was the limit 
to be obtained by the most rigorous selection 
of fluctuating variations. 

Selection, based on fluctuating variation, does 
not, asserts De Vries, conduce to the production 
of improved races. *' Only temporary ameliora- 
tions are obtained, and the selection must be 
made in the same manner every year. More- 
over, the improvement is very limited, and does 
not give any promise of further increase." Not- 
withstanding prolonged efforts, horticulturists 
have not yet succeeded in breeding a biennial 
race of either beetroots or carrots that does not 
continually give rise to useless annual forms. 
Writing of the beet, De Vries says useless 
annual varieties '* are sure to return each year. 
They are ineradicable. Every individual is in 
the possession of this latent quality, and liable to 
convert it into activity as soon as the circum- 
stances provoke its appearance, as is proved by 
the increase of annuals in the early sowings" — 
that is to say, in circumstances favourable to 
the annual variety. 

It will be urged perhaps that these experi- 
ments, which seem to show that there is a limit 
to which a species can be modified by the 
accumulation of fluctuating variations, cannot 
have been properly carried out, because all the 
various breeds of pigeons and other domestic 
animals clearly show that extraordinary differ- 


The Making of Species 

ences not only can, but have actually been pro- 
duced by the selection of such variations. This 
objection is based upon the assumption that 
breeders have in the past dealt only with fluc- 
tuating variations. This assumption does not 
appear to be justified. It is exceedingly prob- 
able that most, if not all, the varieties of 
domesticated animals have originated in muta- 
tions. Take, for instance, the modern turbit 
pigeon ; this has been derived from the old 
Court-bee, described and figured over two 
centuries ago by Aldrovandus. 

De Vries goes so far as to assert that the 
various races of pears are all mutations ; that 
each distinct flavour is a mutation, and that it is 
impossible to produce a new flavour by selecting 
fluctuating variations. Thus it would appear 
that in every case of the production of a new 
breed a mutation has occurred which has 
attracted the fancy of some breeder, and he 
has seized upon this and perpetuated it. 

All the evidence available tends to show that 
there is a limit — and one which is quickly 
reached — to the amount of change that can 
be produced by the selection of fluctuating or 
continuous variations. We, therefore, seem 
driven to the belief that evolution is based on 
the kind of variation which Professor Bateson 
terms ''discontinuous variation" and Professor 
De Vries calls '* mutation." 


Bateson on Variation 

As long ago as 1894 Bateson published his 
Materials for the Study of Variation, in which 
he set forth a large number of cases of discon- 
tinuous variation which he had collected. He 
pointed out that species are discontinuous, that 
they are sharply separated one from another, 
whereas ''environments often shade into one 
another and form a continuous series." How, 
then, he asked, if variations are minute and con- 
tinuous, have these discontinuous species arisen ? 
May not variation prove to be discontinuous, and 
thus make it clear why species are discontinuous? 

On page 1 5 of the above-cited work we find : 
*'The preliminary question, then, of the degree 
of continuity with which the process of evolution 
occurs has never been decided. In the absence 
of such a decision, there has nevertheless been a 
common assumption, either tacit or expressed, 
that the process is a continuous one. The 
immense consequence of a knowledge of the 
truth as to this will appear from a consideration 
of the gratuitous difficulties which have been 
introduced by this assumption. Chief among 
these is the difficulty which has been raised in 
connection with the building up of new organs 
in their initial and imperfect stages, the mode of 
transformation of organs, and, generally, the 
selection and perpetuation of minute variations. 
Assuming, then, that variations are minute, we 
are met by this familiar difficulty. We know 



The Making of Species 

that certain devices and mechanisms are useful 
to their possessors ; but from our knowledge of 
natural history we are led to think that their 
usefulness is consequent on the degree of per- 
fection in which they exist, and that if they 
were at all imperfect, they would not be useful. 
Now it is clear that in any continuous process 
of evolution such stages of imperfection must 
occur, and the objection has been raised that 
natural selection cannot protect such imperfect 
mechanisms so as to lift them into perfection. 
Of the objections which have been brought 
against the theory of natural selection this is by 
far the most serious." 

Bateson further pointed out that chemical 
compounds are not continuous, that they do not 
merge gradually each into the next, and suggested 
that we might expect a similar phenomenon in 
the organic world. 

Elsewhere he says : ** Let the believer in the 
efficacy of selection operating on continuous 
fluctuations try to breed a white or a black rat 
from a pure strain of black-and-white rats, by 
choosing for breeding the whitest or the blackest; 
or to raise a dwarf sweet pea from a tall race 
by choosing the shortest. It will not work. 
Variation leads and selection follows." 

But Bateson's views fell upon stony ground, 
because zoologists are mostly men of theory and 
not practical breeders. They laboured under the 


Work of Bateson and De Vries 

delusion that mutations or "sports" are rare in 
nature, and that when these do happen to occur 
they must of necessity be swamped by inter- 

However, the discovery of the Abbe Mendel's 
account of his experiments on breeding mongrel 
sweet peas has opened the eyes of many 
zoologists, so that they have at last learned 
what practical breeders have known for untold 
years — namely, that sports have a way of per- 
petuating themselves. Moreover, Mendel was 
able to give a theoretical explanation of his 
discoveries, with the result that the believers 
in discontinuous variation have largely increased 
in number of late. 

While we are unable to see eye to eye with 
Professor Bateson in all things, we gladly recog- 
nise the immense value of his work. Had his 
statements in 1894 received the attention they 
merited, zoological theory would to-day be con- 
siderably more advanced than it actually is. 

Professor De Vries has gone farther than 
Bateson, having engrafted upon the Darwinian 
hypothesis the theory of mutations. He has 
done no small amount of experimental work, and 
has undoubtedly thrown much new light on the 
ways in which species arise. He is purely a 
botanist, so that he argues only from plants. 
Nevertheless, we believe that some of his con- 
clusions are applicable to animals. We are far 


The Making of Species 

from accepting his theory of mutations in toto. 
We are, however, convinced that he, like Bate- 
son, is on the right track. There can be no 
doubt that a great many new forms have 
originated suddenly, by jumps, and not by 
imperceptibly slow degrees. Before giving a 
list of the names of some of the races, both 
plant and animal, which appear to have come 
into existence suddenly, it will be of advantage 
to consider for a little some of the more 
important conceptions of De Vries. 

That eminent botanist, as we have already 
seen, insists on the distinction between fluc- 
tuating variations and mutations. The former 
correspond, for all practical purposes, to the 
continuous variations of Bateson, and the latter 
seem to be equivalent to his discontinuous 

According to De Vries, all plants display 
fluctuating variation, but only a small percentage 
exhibit the phenomenon of mutation. The 
most daring of his conceptions is, that the history 
of every species is made up of alternating 
periods of inactivity, when only fluctuating 
variations occur, and of activity when " swarms 
of species" are produced by mutation, and of 
these only a few at the most survive ; natural 
selection, which De Vries likens to a sieve, 
determining which shall live and which shall 


Varieties and Elementary Species 

As we have seen, De Vries does not believe 
that new species can arise by the accumulation 
of fluctuating variations. By means of these 
the race may be greatly improved, but nothing 
more can be accomplished. These variations 
follow Quetelet's law, which says that, for 
biological phenomena, deviations from the aver- 
age comply with the same laws as the devia- 
tions from the average in any other case, if ruled 
by chance alone. 

Very different in character are mutations. By 
means of these, new forms, quite unlike the 
parent species, suddenly spring into being. 
Mutations are said by De Vries to be of two 
kinds — those that produce varieties and those 
which result in new elementary species. 

According to De Vries, those species of plants 
which are in a state of mutation (he refers to the 
species of the systematic botanists) are of a com- 
posite nature, being made up of a collection of 
varieties and elementary species. His concep- 
tion of a variety is a plant that differs from the 
parent plant in the loss or suppression of one or 
more characters, while an elementary species 
differs from the parent form in the possession of 
some new and additional character. But we will 
allow him to speak for himself: "We can con- 
sider (page 141 Species and Varieties) the follow- 
ing as the principal difference between elementary 
species and varieties : that the first arise by the 


The Making of Species 

acquisition of entirely new characters, and the 
latter by the loss of existing qualities, or by the 
gain of such peculiarities as may already be seen 
in other allied species. If we suppose elementary 
species and varieties originated by sudden leaps 
and bounds, or mutations, then the elementary 
species have mutated in the line of progression, 
some varieties have mutated in the line of retro- 
gression, while others have diverged from the 
parental types in a line of digression or in the 
way of repetition. . . . The system (of the vege- 
table kingdom) is built up of species ; varieties 
are only local and lateral, never of real import- 
ance for the whole structure." 

De Vries asserts that these elementary species, 
when once they arise, breed true, and show little 
or no tendency to revert to the ancestral form. 
We can, says De Vries, ascertain only by experi- 
ment which plants are in the mutating state and 
which are not. The great majority, however, are 
not at present in the mutating state. 

The distinction between fluctuating variation 
and mutation has been roughly illustrated by the 
case of a solid block of wood having a number of 
facets, on one of which it stands. If the block 
be tilted slightly it will, when the force that has 
tilted it is removed, return to its old position. 
Such a gentle tilt may be compared to a fluctu- 
ating variation in an organism. If, however, the 
block be tilted to such an angle that when left to 



itself the block does not return to its old position, 
but tips over and comes to rest on another facet, 
we have a representation of the kind of change 
indicated by a mutation. 

The analogy is far from perfect, for it makes 
it appear that the smallest mutation must of 
necessity involve a departure from the normal 
type more considerable than that of the largest 
fluctuating variation. Now, although mutations 
ordinarily consist in considerable deviations from 
the mean or mode of the type, while continuous 
variations are usually minute deviations, it some- 
times happens that the extreme fluctuations are 
more considerable than some mutations. Hence 
** fluctuating " describes this latter kind of 
variation more accurately than " continuous " 

The test, then, of a mutation is not so much 
the amount of deviation as the degree in which 
it is inherited. Mutations show no tendency to 
a gradual return to the mean of the parent 
species ; fluctuating variations do display such a 
tendency. A mutation consists, as M. E. East 
says, in the production of a new mode or centre 
for linear fluctuation ; it is, as it were, a shifting 
of the centre of gravity ; the centre about which 
those fluctuations which we call continuous varia- 
tions occur. 

As it is of considerable importance thoroughly 
to grasp the true nature of mutations or discon- 


The Making of Species 

tinuous variations, and as some writers do not 
appear to realise wherein lies the essential 
difference between the two kinds of variation, 
we will, at the risk of appearing tedious, give 
a further Illustration. Let A be a species of bird 
of which the average length of the wing is 
20 inches, and let us suppose that Individuals 
belonging to that species occur in which the 
length of the wing varies as much as 3 inches 
each side of the mean ; thus it Is possible to find 
individuals of this species with a wing as sh6rt as 
17 inches, or as long as 23 inches. Let B be 
another species of which the average length of 
the wing Is 17 inches, and let us suppose that a 
3-Inch variation on each side of the mean be 
found to occur. Individuals belonging to species 
B will occur which have a wing as short as 
14 inches, or as long as 20 inches. Thus some 
individuals of the short-winged species will have 
longer wings than certain Individuals of the long- 
winged species. Similarly, certain individuals 
of a species which display a mutation may show 
less deviation from the mean than some indi- 
viduals showing a very pronounced fluctuating 
variation. In other words, even as by measuring 
the length of wing in the above example it was 
not always possible to say whether a given indi- 
vidual belonged to species A or B, so is It not 
always possible to say by looking at an individual 
that shows a considerable departure from the 


Law of Regression 

mean whether that departure is due to a mutation 
or a fluctuating variation. 

It is only by watching the effect of the 
peculiarity on the offspring of its possessor that 
we are able to determine the nature of the varia- 
tion. Where the peculiarity is due to a fluctuating 
variation the offspring will display the peculiarity 
in a diminished degree ; but if the peculiarity be 
due to a mutation, the offspring are Hkely to 
display it in as marked a degree as the parent. 

Fritz Mliller and Galton conducted inde- 
pendently enquiries into the amount of the 
regression shown by the progeny of parents 
which have deviated from the average by 
fluctuating variation. 

Muller experimented with Indian corn; Galton 
with the sweet pea. 

Each found that where the deviation of the 
parents is represented by the figure 5, that of 
their offspring is usually 2, that is to say, the 
deviation they display is, on the average, less 
than half that of their parents. 

Applying this rule to the hypothetical case 
given above, if two individuals of species A 
having a length of wing of 20 inches be bred 
together, their offspring will, on an average, have 
a length of wing of 20 inches, since neither 
parents showed any deviation from the mean. 
On the other hand, the offspring of 20-inch-wing 
individuals of species B would show, on an 
F 81 

The Making of Species 

average, a length of wing of only about i8J 
inches. They tend to return to that mode from 
which their parents had departed. 

But suppose that the deviation of the parents 
in this case had been due, not to fluctuating 
variation, but to a mutation ; this would mean 
that, owing to some internal change in the egg 
that produced each parent, 20 inches became the 
normal length of wing ; that the normal length of 
wing had suddenly shifted from 17 inches to 
20 inches. 

The result of this would be that their offspring 
would have on an average a wing-length of 
20 inches instead of 18 J inches, that the centre 
of variation as regards length of wing had 
suddenly shifted from 17 to 20, that, in future, 
all fluctuating variations would occur on either 
side of 20 inches, instead of on either side of 
17 inches as heretofore. 

Thus a variation is a fluctuating one or a 
mutation according as it does or does not obey 
Galton's Law of Regression. 

De Vries says that it is of the essence of 
mutations that they are completely inherited. 
This statement, although substantially true, fails 
to take into consideration the factor of fluctuating 
variation. For example, in the above instance 
if the two individuals of species B had mutated 
into forms with a 20- inch wing, their offspring 
will nevertheless vary znUr se, some of them 


De Vries's Dictum 

will have wings shorter than 20 inches and 
others wings more than 20 inches in length. 
But the average wing-length of the offspring of 
the two mutating individuals will be 20 inches. 

So much, then, for the practical difference 
between a mutation and a fluctuating variation. 
In Chapter V. we shall discuss the possible 
causes of the difference. By way of anticipation 
we may say that the suggestion we shall make is 
that a mutation is due to some rearrangement 
in the particles which represent that part of the 
organism in the fertilised egg, whereas a fluctu- 
ating variation is caused by variations in the 
particles themselves. 

De Vries, it should be noted, bases his theory 
largely on experimental evidence. His dictum 
is ''the origin of species is an object of experi- 
mental observation." He has, we consider, 
proved conclusively that among plants mutations 
sometimes occur, and, further, that in a mutating 
plant the same mutation tends to occur again and 
again. This latter is a most important fact, 
because it goes, somjp ^ay towards overcoming 
the difficulty urged by Darwin that isolated 
sports must be swamped by continual crossing 
with the normal type. If mutations arise in 
swarms, as De Vries asserts they do, then any 
particular mutation is likely, sooner or later, to 
cross with a similar mutation and so be able to 
perpetuate itself. 


The Making of Species 

The classical example of a mutating plant is 
the evening primrose of the species Oenothera 
lamarckiana. This is described by De Vries as 
a stately plant, with a stout stem, attaining often 
a height of 1.6 metres or more. The flowers 
are large and of a bright yellow colour, attracting 
immediate attention, even from a distance. 
"This striking species," he writes, in Species and 
Varieties (p. 525), "was found in a locality near 
Hilversum, in the vicinity of Amsterdam, where 
it grew in some thousands of individuals. Or- 
dinarily biennial, it produces rosettes in the first, 
and stems in the second year. Both the stems 
and the rosettes were seen to be highly variable, 
and soon distinct varieties could be distinguished 
among them. 

The first discovery of this locality was made 
in 1886. Afterwards I visited it many times, 
often weekly or even daily, and always at least 
once a year up to the present time. This stately 
plant showed the long-sought peculiarity of pro- 
ducing a number of new species every year. 
Some of them were observed directly in the 
field, either as stems or rosettes. The latter 
could be transplanted into my garden for further 
observation, and the stems yielded seeds to be 
sown under like control. Others were too weak 
to live a sufficiently long time in the field. They 
were discovered by sowing seed from indifferent 
plants of the wild locality in the garden. A third 


Mutating Plants 

and last method of getting still more new species 
from the original strain was the repetition of the 
sowing process, by saving and sowing the seed 
which ripened on the introduced plants. These 
various methods have led to the discovery of 
over a dozen new types, never previously ob- 
served or described." Some of these De Vries 
regards as varieties, in the sense in which he 
uses the words ; others, he maintains, are real 
progressive species, some of which are strong 
and healthy, others weaker and apparently not 
destined to be successful. All these types proved 
absolutely constant from seed. '' Hundreds of 
thousands of seedlings may have arisen, but they 
always come true and never revert to the original 
O. lamarckiana type. But some of them, how- 
ever, are, like their parent form, liable to muta- 
tions." The case of the evening primrose is by 
no means an isolated one. De Vries cites several 
other instances of plants in a mutating state. 
*' The common poppy," he says (p. 189), " varies 
in height, in colour of foliage and flowers ; the 
last are often double or laciniated. It may have 
white or bluish seeds, the capsules may open 
themselves or remain closed, and so on. But 
every single variety is absolutely constant, and 
never runs into another when the flowers are 
artificially pollinated and the visits of insects 
excluded." Similarly the garden carnation some- 
times gives rise to the wheat-ear form. "In this 


The Making of Species 

variety," writes De Vries (p. 228), '' the flower is 
suppressed, and the loss is attended by a corres- 
ponding increase in the number of pairs of bracts. 
This malformation results in square spikes, or 
somewhat elongated heads, consisting only of the 
greenish bracts. As there are no flowers, the 
variety is quite sterile, and, as it is not regarded 
by horticulturists as an improvement on the 
ordinary bright carnations, it is seldom multiplied 
by layering. Notwithstanding this it appears 
from time to time, and has been seen in different 
countries and at different periods, and what is of 
great importance for us, in different strains of 
carnations. Though sterile, and obviously dying 
out as often as it springs into existence, it is 
nearly two centuries old. It was described in the 
beginning of the eighteenth century by Volckamer, 
and afterwards by Jaeger, De Candolle, Weber, 
Masters, Magnus, and many other botanists. I 
have had it twice at different times and from 
different growers." Similarly, the long-headed 
green dahlia arose twice over some years ago in 
the nursery of Messrs Zocher & Co. 

Further, the peloric Toad-flax i^Linaria vul- 
garis pelor id) is, De Vries informs us, ''known to 
have originated from the ordinary type at 
different times and in different countries under 
more or less divergent conditions." And, as this 
variety is wholly barren, it must in each instance 
have had an independent origin. Lastly, the 


Mutation Theory Criticised \/ 

purple beech seems to be a mutation which has /' 
originated at least three times over. * ;^ 

Every one interested in biological theory- 
should read both Species and Varieties and Plant 
Breeding by De Vries, works which are of 
incalculable value to the horticulturist and agri- 
culturist as well as to the biologist. 

While not wishing to detract in any way from 
the truly splendid work done by De Vries, we 
feel constrained to bring several charges against 

Firstly, he suffers from the complaint that 
seizes nine out of ten originators of new theories. 
He pushes his theory to extreme lengths ; he 
allows his imagination to run away with him. 
We do not think that on the evidence available 
he is justified in asserting that every species 
passes through alternating periods of comparative 
quiescence and periods in which it throws off, 
as mutations, swarms of elementary species. He 
is justified in asserting that discontinuous varia- 
tion is by no means an uncommon phenomenon, 
but further than this it does not seem safe to go 
at present. 

Secondly, he ought to lay more stress on the 
fact that Oenothera lamarckiana is a plant which 
does not appear to be known in the wild state, 
and that it is therefore possibly a hybrid plant, 
and the so-called elementary species which it 
gives off may be merely the varieties out of 




The Making of Species 

which it has been built up. Boulenger and 
Bailey have both studied this plant, and they 
have not been able to witness all the mutations 
of which De Vries speaks, so that the former 
says, '' The fact that Oenothera lamarckiana was 
originally described from a garden flower, grown 
in the Paris Jar din des Plantes, and that, in spite 
of diligent search, it has not been discovered 
wild anywhere in America, favours the prob- 
ability that it was produced by crossing various 
forms of the polymorphic Oenothera biennis^ which 
had been previously introduced in Europe." 

It has further been objected that, even if 
these various forms which Lamarck's evening 
primrose throws off are true mutations, they 
ought not to be called new species, for they do 
not differ sufficiently from the parent species 
to deserve the name of new species. The reply 
to this criticism is that De Vries asserts that 
mutations produce new elementary species, which 
are not the same things as new species in the 
ordinary sense of the term. Most Linnsean 
species differ from one another to a far greater 
extent than do elementary species. It seems 
to us quite plain that new species arise, not by 
a single mutation, but by two or three successive 
mutations which occur in various parts of an 

First arises a well-marked variety, by a single 
mutation. Subsequent mutations follow, so that 


Definition of a Species 

a distinct race is produced. And, finally, fresh 
mutations occur, so that a new species is eventu- 
ally produced. 

What De Vries calls an elementary species 
the majority of systematlsts would call a well- 
marked variety. 

We may take this opportunity of remarking 
that the definition of a species is one on which 
naturalists seem unable to agree. 

So vast is the field of biology, that now-a-days 
biologists are compelled to specialise to some 
extent. Thus we have botanists, ornithologists, 
those who devote themselves to the study of 
mammals, those who confine themselves to 
reptiles, or insects, or fishes, or crustaceans, or 
bacteria, etc. 

Now each class of systematists has its own 
particular criterion of what constitutes a species. 
Ornithologists do not seem very exacting. Most 
of them appear to consider a constant difference 
of colour sufficient for the formation into a species 
of the birds that display such a variation. Those 
who study reptiles, on the other hand, do not 
allow that a mere difference in colour is sufficient 
to promote its possessor to specific rank. Into 
these nice questions we cannot enter. For our 
purpose a species is a group of individuals that 
differ from all other individuals in displaying 
certain well-marked and tolerably constant charac- 
ters, which they transmit to their offspring. 


The Making of Species 

Our contention, then, is that new species, in 
the ordinarily-accepted use of the term, do not 
arise as a rule by one sudden bound (although 
they may sometimes do so), but are the result of 
the accumulation of several mutations or dis- 
continuous variations. Some of these mutations 
are exceedingly well marked, while others are so 
small as to be indistinguishable from the more 
extreme fluctuating variations. Before passing 
on to consider some cases of well-marked muta- 
tions which have occurred among animals and 
plants, we should like to take this opportunity of 
pointing out that as regards experiments in 
evolution the botanist is far more favourably 
situated than the zoologist. 

The botanist is able to reproduce many species 
vegetatively, e,g, by cuttings, and is thus easily 
able to multiply examples of mutation. He can 
also reproduce the great majority of plants by 
self-fertilisation, and so experiences no difficulty 
in ''fixing" a new form. Again, plants are far 
easier to control than animals ; as a rule they can 
be transplanted without any impairment of their 
capacity for breeding. Moreover, they produce 
a greater number of offspring than the most 
prolific of the higher animals. The animal 
breeder is thus at an obvious disadvantage as 
compared with the horticulturist. It is only 
with great difficulty that he can fix the mutations 
which appear in his stock. 


" Scatliff Strain " of Turbit 

The history of the production of the ** Scatliff 
strain " of turbit affords a good example of the 
kind of difficulties that confront the breeder. 

Pigeon fanciers require that the ideal turbit 
shall have, among other things, an unbroken 
** sweep," that is to say the line of the profile 
from the tip of the beak to the back of the head 
should be the arc of a circle. As a rule this line 
is broken by the overgrowth of the wattle at the 
base of the beak. Mr Scatliff, however, has 
succeeded in breeding a strain which possesses 
the required description of profile. 

"In the year 1895," writes Mr H. P. Scatliff 
on page 25 of The Modern Turbit, " I visited 
Mr Houghton's lofts and purchased three or four 
extra stout and short-beaked stock birds. . . . 
The following year I mated one of these to one 
of my own black hens, and reared one of the 
most successful show birds ever bred, viz. 
* Champion Ladybird,' a black hen. . . . Most of 
the leading judges and many turbit breeders 
remarked upon this hen's wonderful profile, which 
seemed to improve as she got older instead of 
getting worse, as is usual in rather coarse-wattled 
birds. I, too, had remarked this, and it opened 
my eyes to a point in turbit breeding which I 
had never heard mentioned by any turbit judges 
or breeders, and which I believe I am now 
pointing out for the first time in print, viz. that 
the feathers over her beak wattle which formed 


The Making of Species 

her iront grew from the top and right to the front 
of her wattle, and not from slightly behind, as in 
almost every other turbit of her day ; thus, as 
the wattle developed and grew coarser, the front 
became more developed, and made her head 
larger without in any way spoiling the sweep of 
the profile. 

"■ The same year ' Ladybird ' was bred I bred 
eight others from the same pair, and with one 
exception all turned out to be hens. There was 
only one other hen, however (a dun), that had 
this same point, but in a lesser degree than 
' Ladybird,' and from these two hens nearly all 
my blacks, and several of my blues are de- 

Mr Scatliff, having " spotted " this point, 
looked about him for another bird having the 
peculiarity, with the object, if possible, of fixing 
the same in his strain. He discovered this point 
in a pigeon belonging to Mr Johnston of Hull, 
and purchased the bird for ^20. But it died in 
the following spring without producing for Mr 
Scatliff a single young one. The next year 
Scatliff found that a bird belonging to a Mr 
Brannam had the required peculiarity and so 
purchased him for ;^20. But that cock, too, died 
before anything was bred from him. Nothing 
daunted, Scatliff found that another of Brannam's 
cocks displayed the same peculiarity, so purchased 
him in 1899 for ^15, but he also died before the 



From " The Modern TurbU," published by " The Feathered World ^' London. 

" ScatlifF Strain " of Turbit 

year was out. Meanwhile Scatliff had, by mating 
up *' Ladybird " with the most Hkely of his own 
cocks, succeeded in producing one or two young 
cocks with the desired point. By breeding these 
with their mother '' Ladybird " and their off- 
spring again with '* Ladybird," ScatHff eventually 
succeeded in breeding some turbits, both blacks 
and duns, with the required peculiarity fully 
developed, but not before he had spent a further 
sum of ;^55 on two other cocks, both of which 
died before they could be mated with the famous 
" Ladybird." However, amid all his misfortunes, 
Scatliff informs us that he bought one bird, by 
name '' Amazement," which did assist him in 
fixing his strain. Thus Scatliff spent consider- 
ably over ^loo in purchases, and took eight years 
fixing the peculiarity in question. Had " Lady- 
bird " been a flower, the peculiarity could probably 
have been fixed in one generation by self- 

This furnishes an excellent example of the 
trouble which breeders will take, and the expense 
to which they will go in order to produce a 
desired result. Nevertheless, it appears to be 
the fashion for scientific men to decry the work 
of the breeder. 

Let us now pass on to consider the cases of 
mutations which are known to have occurred 
among animals. 


The Making of Species 

Mutations among Animals 

Some instances of great and sudden variation 
in domesticated animals have become classical, 
and been detailed in almost every work on 
evolution. These are, firstly, the celebrated 
hornless Paraguay cattle. This hornless breed, 
or rather the ancestor of the breed, arose quite 

Many domestic horned breeds of animals, 
especially sheep and goats, throw off hornless 
sports. Were a hornless breed of buffalo found 
in nature, it would undoubtedly be ranked a 
new species, and the Wallaceians would doubt- 
less exercise much ingenuity in explaining how 
natural selection had brought about the gradual 
disappearance of the horns ; and palaeontologists, 
being baffled in their search for intermediaries 
between the hornless species and their horned 
ancestors, would complain of the imperfection of 
the geological record. 

It may, perhaps, be argued that this hornless 
mutation was a direct result of the unnatural 
conditions to which the Paraguay cattle were 
subjected, it may be asserted that since there 
are no species of hornless cattle in nature, such 
mutations have never occurred under natural 
conditions, and hence the Paraguay cattle prove 
nothing. As a matter of fact, we know that in 
nature a great many mutations occur which are 


Mutations among Mammals 

not perpetuated because not beneficial to the 
species. A hornless individual in the wild 
state would stand but little chance in fighting for 
females against his horned brethren. We must 
keep clearly in mind that the theory of mutation 
does not seek to abolish natural selection ; it 
merely affords that force something substantial 
to work upon. 

The second classical example of a leap taken 
by nature is furnished by the Franqueiro breed 
of long-horned cattle in Brazil. These furnish 
us with an example of a mutation in the other 
direction. Then there is the Niata or bull-dog 
breed of cattle, which are also South American. 
These instances would seem to indicate that 
cattle are what De Vries would call " in a mutat- 
ing state " in that part of the world. 

The other classical examples of great and 
sudden variations are the Ancon sheep of Massa- 
chusetts, the Mauchamp breed of Merino sheep, 
the tufted turkeys, and the long-haired race of 

The '' wonder horses," whose manes and tails 
grow to an extraordinary length, so as to trail 
on the ground, may perhaps be cited as a race 
which originated in a sudden mutation. They 
are all descendants of a single individual, 
Linus I., whose mane and tail were respectively 
eighteen and twenty-one feet long. But in this 
case it is important to note that the parents and 


The Making of Species 

grandparents of Linus I. had exceptionally long 

Coming now to birds we find several undoubted 
examples of mutations, or new forms which have 
come suddenly into being. 

The black- winged peafowl, whose peculiarities 
were commented on by Darwin, afford a striking 
example of this phenomenon. These birds breed 
true when mated together, and are known to 
have arisen from common peafowl in no less 
than nine instances. The cocks have the wings 
(except the primary quills), black glossed with 
blue and green, and have the thighs black, 
whereas, in the ordinary peacock, the same part 
of the wing is nearly all mottled black and pale 
buff, and the thighs are drab. The black-winged 
hen, on the other hand, is nearly white, but has 
a black tail and black speckling on the upper 
surface of the body, while her primary quills are 
cinnamon coloured as in male peafowl, not 
drab as in the normal hens. The young are 
white when hatched, the young cock gradually 
assuming the dark colour as he matures. 

This mutation, which, in one case quoted by 

Darwin, increased among a flock of peafowl 

until the black-winged supplanted the ordinary 

kind, is so distinct in appearance in all stages 

that it was formerly supposed to be a true species 

{Pavo nigripennis), of which the wild habitat was 



Mutations among Birds 

The Golden Pheasant (Chrysolophus pictus) 
produces, in domestication, the dark-throated 
form (C. obscurus), in which the cock has the 
throat sooty-black instead of buff, and the 
scapulars or shoulder feathers black instead of 
red. Moreover, the two middle-tail-feathers are 
barred with black and brown like the lateral 
ones, while in the ordinary form they are spotted 
with brown on a black ground. The hens have 
a chocolate-brown ground-colour instead of 
yellow-ochre as in the normal type. The 
chicks are likewise darker. 

The common duck, in domestication, when 
coloured like the wild mallard, sometimes pro- 
duces a form in which the chocolate breast and 
white collar of the drake are absent, the pencilled 
grey of the abdomen reaching up to the green 
neck. In this mutation the duck has the head 
uniformly speckled black and brown, and lacks 
the light eye-brow and cheek-stripes found in 
the normal duck. Both sexes have the bar on 
the wing dull black instead of metallic blue. 

The ducklings which ultimately bear this 
plumage are sooty-black throughout, not black 
and yellow like normal ones. 

The phenomenon of mutation is not confined 
to animals in a state of domestication. The 
common Little Owl of Europe {Athene noctua) 
has produced the mutation A, chiaradicB in the 
wild state. In this the irides are dark, instead of 
G 97 

The Making of Species 

yellow as in the normal type, and the plumage of 
the back of the wings is longitudinally streaked 
with white instead of barred. Several examples 
of this form were found, along with normal young, 
in the nest of one particular pair of little owls in 
Italy, but the whole family were foolishly ex- 
terminated by local ornithologists. 

The reed bunting {Emberiza schoeniclus) exists 
in two distinct forms — one having a much stouter 
bill than the other {E. pyrrhuloides). This prob- 
ably is an example of a mutation. 

The rare yellow-rumped Finch i^Munia flavi- 
prymna), of Australia, has displayed a tendency 
to change into the allied and far commoner 
chestnut - breasted Finch [M. castaneithorax) 
during the lifetime of the individual {Avicultural 
Magazine, 1907). Conversely, the male of the 
common Red-billed Weaver [Quelea que lea) of 
Africa has been found in its old age to assume 
the characters of the comparatively rare Q. russi, 
its black throat becoming pale buff as in that 
. form. 

Everyone is familiar with the chequered 
variety of the common blue - rock pigeon, in 
which the wings are regularly mottled with 
black instead of being barred. This form some- 
times occurs among wild birds, so that it has 
been described as a distinct species. It is 
important to note that there are red, dun, and 
silver chequers as well as blue ones. 


■ft >" 

Mutations among Birds 

A well-marked mutation which appears regu- 
larly in nature is the red-headed variety of the 
beautiful Gouldian Finch [Poepkila niirabilis ) 
of North Australia. Normally the head of the 
cock is black, but in about ten per cent, of the 
individuals the cock has a crimson head, while 
that of the hen is dull crimson and black. 

Mutations which occur with such regularity 
are certainly rare. On the other hand, there are 
certain mutations which we may expect to see 
appear in any species of plant or animal. 

Albinistic forms are a case in point, and less 
frequently we see white varieties which are not 
pure albinos, because the eye retains some at 
least of the normal pigment. As examples, we 
may cite white dogs, cats, fowls, horses, ducks, 
geese, and Java sparrows among domesticated 
animals, and the white forms of the Amazonian 
dolphin and of the giant Petrel of the South 
seas {Ossifraga gigantea) among wild creatures. 

In a white mutation the eye may lose all its 
pigment, and then we have a true albino. Such 
forms on account of their imperfect vision cannot 
survive in a state of nature, hence no wild pink- 
eyed species are known. 

Or the eye may display a partial loss of pig- 
ment, as, for example, in the white domestic 
forms of the common goose, the Chinese goose, 
and the Muscovy duck. Finn saw a case in 
which the eyes of a pink-eyed rabbit changed 


The Making of Species 

after death into this type of eye — that is, with 
the pupil black and the iris blue. It is to be 
observed that this kind of eye sometimes occurs 
in coloured horses, rabbits, and dogs. Finally, 
we have white mutations in which the eye loses 
none of the pigment. These are abundant in 
nature, and probably most of the white species 
of birds — as, for example, some egrets, swans, 
etc. — arose in this way.^ Pure white species are 
comparatively uncommon in nature, because, 
except in snow-clad regions, white creatures are 
easily seen by their adversaries. Most white 
birds are of considerable size, and well able to 
look after themselves. 

Similarly black mutations occur frequently 
among animals, both under domestication and 
in a state of nature. All are familiar with black 
dogs, cats, horses, fowls, ducks, pigeons. Black 
mutations, however, do not occur nearly so 
frequently as white ones. So far as we are 
aware no black mutation has been recorded 
among canaries, geese, guinea-fowl, ferrets, 
Java sparrows or doves, all of which produce 
white mutations. 

On the other hand, in the wild state black 
species occur more frequently than normal-eyed 
white forms. This is probably because such 

^ Some egrets, such as the rock-egrets {Demiegrefta) of eastern 
tropical coasts, are normally grey, but may be white, and this 
whiteness may be confined in individuals to the youn^ or adult 


Colour Mutations 

creatures are less conspicuous than white ones. 
As examples of black mutations which occur in 
nature, we may cite black leopards, water 
rats, squirrels, foxes, barking deer {Cervulus 
muntjac), hawk-eagles, harriers, peppered moth 
{Ampkidasys betularia), etc. 

That many black species have arisen as sudden 
mutations from lighter-coloured animals seems 
tolerably certain from the facts that in Malacca 
the black leopard forms a local race ; that some 
of the Gibbon apes are as often black as light 
coloured ; that the American black bear is some- 
times brown, while the other bears, when not 
brown, are almost invariably black. 

Not uncommon, although rarer than black or 
melanistic forms, are reddish or chestnut varieties. 
These occur both among tame and wild animals. 
Among domesticated creatures, sandy cats, '' red " 
pigeons, buff fowls, chestnut horses, red guinea 
pigs afford examples of this mutation. Among 
wild animals many of the species of squirrel, not 
naturally red, produce red mutations ; and some of 
the grey owls — as, for example, the Indian race 
of the Scops {Scops giu) — throw off a red or 
chestnut form. As everyone knows, some species 
are normally red. 

Green or olive species not unfrequently throw 
off yellow mutations. As examples of these we 
may cite yellow canaries, yellow budgerigars 
[Melopsittacus undulatus)^ goldfish, golden tench, 


The Making of Species 

and the golden form of the common carp among 
captive animals ; and among animals in a state 
of nature, yellow forms have been recorded of the 
rose-ringed Paroquet {Palceornis torquatus), the 
green woodpecker, the pike, and the eel. These 
lutinistic forms usually have normally coloured 
eyes. Sometimes, but only very rarely, these 
yellow forms throw off white sports — as, for 
example, the "silver" form of the goldfish. 
Finn has seen a white variety of the common 
carp. White canaries are excessively rare, while 
white budgerigars are unknown. 

It is worthy of note that entirely yellow species 
of birds and fish are unknown. We would suggest 
that the explanation of this is that yellowness is 
correlated with some physical characteristic un- 
favourable to an organism exposed to the 
struggle for existence ; hence individuals which 
are yellow are not permitted to survive. In some 
species of moths individuals occur in which the 
parts normally red are yellow. According to 
Bateson, a chalk pit at Madingly, near Cam- 
bridge, has long been known to collectors as a 
habitat of a yellow-marked form of the six-spot 
Burnet Moth (Zygcena filipendulce). These 
lutinistic forms are not confined to one genus 
of Butterflies. Moreover, in the Pin-tailed Non- 
pareil Finch [Eytkrura prasina) of the Eastern 
Archipelago the red tail and other red parts of 
the plumage are not infrequently replaced by 


Mutations among Invertebrates 

yellow in wild individuals of either sex and of 
any age. In the blue-fronted Amazon parrot 
{Chrysotis cestiva) — a most variable bird — the 
normally red edge of the pinion is sometimes 
yellow. Bateson, in his Materials for the Study 
of Variation, gives other examples of this kind 
of variation. 

As further instances of mutations among 
animals which have been observed in nature, we 
may mention the valezina form of the female of 
the Silver-washed Fritillary Butterfly [Argynnis 
paphia) and the helice form of the female Clouded- 
yellow Butterfly (Co lias edusa). 

The common jelly-fish is an organism which 
frequently throws off sports, and some zoologists 
are of opinion that the medusoid Pseudoclytia 
pentata arose by a discontinuous variation from 
Epenthesis folleata or a closely allied form. 
Thomson discusses this particular case at some 
length on pages 87-89 of his Heredity, and gives 
it as his opinion that the evidence in favour 
of this latter having arisen as a mutation is 
"exceedingly strong." 

It is our belief that many species of birds 
which occur in nature have been derived from 
other species which still exist, but as no one has 
ever seen the mutation take place, we cannot 
furnish any proof thereof We merely rely on 
the fact that the species in question differ so 
slightly from one another that there seems every 


The Making of Species 

likelihood that they have suddenly arisen and 
managed to establish themselves alongside of the 
parent species. 

The Curassows, Crax grayz, C. hecki, each 
of which is only known by a very few specimens, 
appear to be mutations of the female of the 
globose Curassow, Crax globicera. The fact 
that when a female hecki bred in the London 
Zoological Gardens with a male globicera, the 
solitary young one which lived to grow up was a 
pure globzcera, renders the assumption almost 

The Chamba Monaul (JLophophorus chambanus) 

seems to be a mutation of the male of the 

common Monaul or Impeyan Pheasant {Lopho- 

phorus impeyanus), the common species of the 


The Three-coloured Mannikin {Muniamalacca) 
of South India is probably simply a white-bellied 
form of the widely-ranging Black-headed Man- 
nikin {M. atricapilla), which has the abdomen 
chestnut like the back. Intermediate wild- 
caught forms have been recorded. 

The African Cordon-bleu i^Estrelda phcenicotis) 
and Blue-bellied Waxbill {E. cyanogastrd) would 
also seem to be mutations, as almost the only 
difference between them lies in the fact that 
the male of the former has a crimson cheek- 
patch, which is wanting in the latter. 

The Ringed Finch {Stictoptera annulosd) of 


Mutating Species 

Java, and Bicheno's Finch (S. bichenovii) of 
Australia, only differ in the former having the 
rump black, while in the latter it is white, and 
this difference appears to be of the nature of a 

So, it might be urged, is the pure white breast 
of the male Upland Goose (Chloephaga magel- 
lanicd), which part, in the very similar C. dispar, 
is barred as in the females, the latter form being 
probably the ancestor. 

The differences between the silver-grey-necked 
Crowned Crane of the Cape {Balearica chryso- 
pelargus) and the dark-necked species of West 
Africa {B. regulorum) seem also to be not more 
than could be accounted for by mutation. 

Peculiar forms, such as a rabbit with a con- 
voluted brain or a mouse with a peculiar pattern 
of molar teeth, have been come upon by 

The above-cited mutations are all very con- 
siderable ones, and we do not profess to have 
mentioned a tenth part of those which have 
actually been recorded. 

We trust that we have collected and set forth 
sufficient evidence to show that the phenomenon 
of discontinuous variation is a very general one, 
and this would seem to tell against the hypo- 
thesis of De Vries that species pass through 
alternate periods of comparative stability and 
periods when swarms of mutations appear. We 


The Making of Species 

think it more probable that all species throw ofif 
at greater or less intervals discontinuous varia- 
tions, and that it is upon these that natural selec- 
tion acts. 

We further hope that we have succeeded in 
making clear what we believe to be the very- 
sharp distinction between continuous and dis- 
continuous variations, even when the latter are 
inconsiderable, as frequently happens. 

Before leaving the subject of variation it is 
necessary to notice the distinction, which Weis- 
mann was the first to emphasise, between somatic 
and germinal variations. 

Every adult organism must be regarded as the 
result of two sets of forces ; inherited tendencies 
or internal forces, and the action of environment 
or external forces. The differences which the 
various members of a family show are due in 
part to the initial differences in the germinal 
material of which they are composed, and in part 
to the differences of their environment. The 
former differences are the result of what we may- 
call germinal variations, and the latter the result 
of somatic variations. It is scarcely ever possible 
to say of any particular variation that it is a 
germinal or a somatic one, because even before 
birth a developing organism has been subjected 
to environmental influences. One of a litter may 
have received more nourishment than the others. 
Nevertheless, any marked variation which appears 


Somatic and Germinal Variations 

at birth is probably largely germinal. According 
to Weismann and the majority of zoologists, 
there is a fundamental difference between these 
germinal and somatic variations, in that the 
former tend to be inherited, while the latter are 
never inherited. Weismann believes that very 
early in the formation of the embryo the cells 
which will form the generative organs of the 
developing organism are separated off from those 
cells which will go to build up the body, and 
become as much isolated from them as if they 
were contained in a hermetically-sealed flask, so 
that they remain totally unaffected by any 
changes which the environment effects in the 
somatic cells. Therefore, says Weismann, 
acquired characters cannot be inherited. 

While the majority of zoologists believe that 
acquired characters are not inherited, probably 
not many will go so far as Weismann and 
declare that the environment cannot exercise 
any effect whatever on the germ cells. 

Even though acquired characters or variations 
are not inherited, it does not follow that they do 
not play an important part in evolution. Acquired 
variations are the result of the way in which an 
organism reacts to its environment. If an organ- 
ism is unable to react to its environment it must 
inevitably perish. If it is able to react, it matters 
not, so far as the chances of survival of the 
organism are concerned, whether the adaptation 


The Making of Species 

is the result of a congenital variation or a somatic 
one. This will be rendered clear by a hypotheti- 
cal example. Let us suppose that a certain 
mammal is forced, owing to the intensity of the 
struggle for existence, to migrate into the Arctic 
regions. Let us further suppose that this organ- 
ism is preyed upon by some creature that hunts 
by sight rather than by scent. Let us yet 
further imagine that this predacious species is 
swifter than our animal, on which it preys. It 
is obvious that, other things being equal, the 
more closely the creature preyed upon assimilates 
to its surroundings the more likely is it to escape 
the observation of its foes, and so to survive and 
give birth to offspring. Now suppose that the 
glare from the snow-covered ground bleaches its 
coat. This whitening of the fur is a somatic 
variation, one which is induced by the environ- 
ment. Such an animal will be as difficult to see, 
if the bleaching is such as to render it snow- 
white, as if its whiteness were due to a germinal 
variation. Thus, as regards its chances of sur- 
vival, it matters not whether its whiteness be the 
result of germinal or somatic variation. But if 
the whiteness is due to a somatic variation, its 
offspring will show no tendency to inherit the 
variation ; they will have in turn to undergo the 
bleaching process. If, on the other hand, the 
whiteness is due to a germinal variation, the 
offspring will tend to inherit this peculiarity and 


Somatic Variations 

to be born white. In such a case, it is unlikely 
that the fur of an organism which is naturally- 
coloured will be completely bleached by the 
snow, and, even if it be, the bleaching process 
will take time, meanwhile the creature will be 
comparatively conspicuous. So that those which 
are naturally whiter than the average, that is to 
say, those in which the tendency to whiteness 
appears as a germinal variation, will be less con- 
spicuous than those which tend to be the ordinary 
colour. Thus the former will enjoy a better 
chance of survival, and will be likely to transmit 
their whiteness to their offspring in so far as it 
is due to a germinal or congenital variation. 

Thus, although none of the whiteness due to 
somatic variations is transmitted to the offspring, 
such variations are of considerable importance 
to the species, as they enable it to survive and 
allow time for the germinal variations in the 
required direction to appear. 

That this case need not be purely hypothetical 
is shown by the fact that dun domestic pigeons, 
which are of an earthy-brown colour when fresh 
moulted, soon fade in the sun to a dull creamy 
hue. Thus a coloration adapted to an ordinary 
soil could soon be suited to a desert environ- 
ment. The ruddy sheldrake also, normally a 
bright chestnut- coloured bird, and one that haunts 
exposed sunny places, in many cases fades very 
much, becoming almost straw-coloured. 


The Making of Species 

Many variations which organisms display are 
of a mixed kind, being in part the result of inner 
forces and in part due to the action of the en- 
vironment. In so far as they are due to this 
latter they do not appear to be inherited. 

Thus, although we cannot say of many varia- 
tions whether they are germinal, or somatic, or 
of a mixed kind, it is of great importance to keep 
continually in mind the fundamental differences 
between the two kinds. 

Some somatic variations are due to the direct 
action of the environment ; they are merely the 
expression of the manner in which an organism 
responds to external stimuli. 

What is the cause of germinal variations? 
This is a question to which we are not yet in a 
position to give a satisfactory answer. 

The attempt to explain their origin plunges us 
into the realm of theory. This doubtless is a 
realm full of fascination, but it is an unexplored 
region of extreme darkness, in which, we believe, 
it is scarcely possible to take the right road until 
more of the light of fact has been shed upon it. 

In the chapter dealing with inheritance we 
shall indicate the lines along which it is likely 
that future progress will be made. 




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. 

TH E alleged sterility of the hybrids pro- 
duced by crossing different species 
has long proved a great stumbling- 
block to evolutionists. Huxley, in 
particular, felt the force of this objection to the 
Darwinian theory. If the hybrids between 
natural species are sterile, while those of all 
the varieties which the breeder has produced 
are perfectly fertile, it is obviously quite use- 
less for evolutionists to point with pride to the 
results obtained by the breeder, and to declare 
that his products differ from one another to a 
greater extent than do many well-recognised 


The Making of Species 

*' After much consideration, and with no bias 
against Mr Darwin's views," wrote Huxley to 
the Westminster Review in i860, "it is our clear 
conviction that, as the evidence now stands, it is 
not absolutely proven that a group of animals 
having all the characters exhibited by species in 
nature, has ever been originated by selection, 
whether natural or artificial. Groups having the 
morphological nature of species, distinct and per- 
manent races, in fact, have been so produced 
over and over again ; but there is no positive 
evidence at present that any group of animals 
has, by variation and selective breeding, given 
rise to another group which was in the least 
degree infertile with the first Mr Darwin is 
perfectly aware of this weak point, and brings 
forward a multitude of ingenious and important 
arguments to diminish the force of the objection. 
We admit the value of these arguments to the 
fullest extent ; nay, we will go so far as to express 
our belief that experiments, conducted by a skil- 
ful physiologist, would very probably obtain the 
desired production of mutually more or less in- 
fertile breeds from a common stock in a com- 
paratively few years; but still, as the case stands 
at present, this little 'rift within the lute' is not 
to be disguised or overlooked." 

Similarly Wallace writes, at the beginning of 
chapter vii. of his Darwinism : " One of the 
greatest, or perhaps we may say the greatest, of 


Alleged Sterility of Hybrids 

all the difficulties in the way of accepting the 
theory of natural selection as a complete expla- 
nation of the origin of species, has been the 
remarkable difference between varieties and 
species in respect of fertility when crossed. 
Generally speaking, it may be said that the 
varieties of any one species, however different 
they may be in external appearance, are per- 
fectly fertile when crossed, and their mongrel 
offspring are equally fertile when bred among 
themselves ; while distinct species, on the other 
hand, however closely they may resemble one 
another externally, are usually infertile when 
crossed, and their hybrid offspring absolutely 
sterile. This used to be considered a fixed 
law of nature, constituting the absolute test and 
criterion of a species as distinct from a variety; 
and so long as it was believed that species were 
separate creations, or at all events had an origin 
quite distinct from that of varieties, this law could 
have no exceptions, because if any two species 
had been found to be fertile when crossed and 
their hybrid offspring to be also fertile, this fact 
would have been held to prove them to be not 
species but varieties. On the other hand, if two 
varieties had been found to be infertile, or their 
mongrel offspring to be sterile, then it would 
have been said — These are not varieties, but 
true species. Thus the old theory led inevitably 
to reasoning in a circle, and what might be 
H 113 

The Making of Species 

only a rather common fact was elevated into a 
law which had no exceptions." 

Thus the sterility of hybrids was a zoological 
bogey which had to be demolished. The plan 
of campaign adopted by Darwin and Wallace 
was, firstly, to try to disprove the assertion that 
the hybrids between different species are always 
sterile, and secondly, to find a reason for the 
alleged sterility of these hybrids. 

Darwin succeeded in obtaining some examples 
of crosses between botanical species which 
were said to be fertile. These he quotes in 
chapter viii. of The Origin of Species, As 
regards animals, he met with less success. 
** Although," he writes, '* 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 reevesiiy and from Phasianus colchicus and 
P. torquatiis and with P. versicolor are perfectly 
fertile. There is no doubt that these three 
pheasants, namely, the common, the true ring- 
necked, and the Japan, intercross, and are 
becoming blended together in the woods of 
several parts of England. The hybrids from 
the common and Chinese geese i^A. cygnoides), 
species which are so different that they are 
generally ranked in distinct genera, have often 
been bred in this country with either pure 

parent, and in one single instance they have 


Fertile Hybrids 

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 (grand- 
children 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 
Captain 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.^ ... So again there 
is reason to believe that our European and the 
humped Indian cattle are quite fertile together ; 
and from facts communicated to me by Mr 
Blyth, I think they must be considered as 
distinct species." 

Darwin does not seem to have been very 
satisfied with the evidence he had collected, for 
he said : " Finally, looking to all the ascertained 
facts on the intercrossing of plants and animals, 
it may be concluded that some degree of sterility, 

^ After years of observation of these Indian geese, Finn is 
convinced they are now, at all events, pure Chinese ; it is possible 
that they really were hybrids in Blyth's time, but that fresh im- 
portations of geese from China, such as still occur, may have 
ultimately swamped the blood of the common goose. The fertility 
of the hybrid geese was, however, known to such early writers as 
Pallas and Linnaeus. Darwin himself, at a later date, bred 
five young from a pair of such hybrids {Nature^ Jan. i, 1880, 
p. 207). 


The Making of Species 

both in first crosses and in hybrids, is an ex- 
tremely general result ; but that it cannot, under 
our present state of knowledge, be considered as 
absolutely universal." 

Similarly Wallace writes : '* Nevertheless, the 
fact remains that most species which have 
hitherto been crossed produce sterile hybrids, 
as in the well-known case of the mule ; while 
almost all domestic varieties, when crossed, 
produce offspring which are perfectly fertile 
among themselves." 

Darwin resorted to much ingenious argument 
in his attempt to explain what he believed to 
be the almost universal sterility of hybrids, as 
opposed to mongrels or crosses between varieties. 
He pointed out that changed conditions tend to 
produce sterility, as is evidenced by the fact that 
many creatures refuse to breed in confinement, 
and believed that the crossing of distinct wild 
species produced a similar effect on the sexual 
organs. He expressed his belief that the early 
death of the embryos is a very frequent cause of 
sterility in first crosses. 

Wallace thus summarises Darwin's conclusions 
as to the cause of the sterility of hybrids : " The 
sterility or infertility of species with each other, 
whether manifested in the difficulty of obtaining 
first crosses between them or in the sterility of 
the hybrids thus obtained, is not a constant or 
necessary result of species difference, but is in- 


A Biological Bogey 

cidental on unknown peculiarities of the repro- 
ductive system. These pecuHarities constantly 
tend to arise under changed conditions owing 
to the extreme susceptibility of that system, and 
they are usually correlated with variations of 
form or of colour. Hence, as fixed differences 
of form and colour, slowly gained by natural 
selection in adaptation to changed conditions, 
are what essentially characterise distinct species, 
some amount of infertility between species is 
the usual result." 

But Wallace has not been content to let the 
matter remain where Darwin left it. He has 
boldly tried to make an ally of this bogey of the 
infertility of hybrids. On page 179 oi Darwinism 
he argues, most ingeniously, that the sterility of 
hybrids has been actually produced by natural 
selection to prevent the evils of the intercrossing 
of allied species. We will not reproduce his 
argument for the simple reason that it is now 
well-known, or should be well-known, that hybrids 
between allied species are by no means always 
sterile. The doctrine of the infertility of hybrids 
seems to have been founded on the fact that the 
hybrids best known to breeders, namely the 
cross between the ass and the horse, and those 
between the canary and other finches, are sterile. 


The Making of Species 

Fertile Crosses between Species of Plants 

In the case of plants the number of fertile 
hybrids between species is so large that we 
cannot attempt to enumerate them. De Vries 
cites several instances in Lecture IX of his 
Species and Varieties : Their Origin by Mutation, 

One of these — the hybrid between the purple 
and the yellow species of Lucerne which is 
known to botanists as Medicago media is, writes 
De Vries, *' cultivated in some parts of Germany 
on a large scale, as it is more productive than 
the ordinary lucerne." Other examples of per- 
fectly fertile plant hybrids cited by De Vries 
are the crosses between Anemone magellanica 
and A. sylvestriSy between Salix alba and Salix 
pentandra, between Rhododendron hirsutum and 
R. ferrugineum. 

He gives an instance of a hybrid — ^gilops 
speltcsformis, which, though fertile, is not so 
fertile as a normal species would be. It is worthy 
of note that Burbank of California has obtained 
\ a hybrid between the blackberry and the rasp- 
berry, which is not only fertile, but quite popular 
I as producing a novel fruit. 

Sterile Plant Hybrids 

De Vries does not cite nearly so many examples 
of sterile hybrids, presumably because they are 
not so easy to find. He mentions the sterile 


bi^t cuiy3^ ill t . J, J : ^jU^4nA*f ^n^-tST-^ 

Fertile Mammalian Hybrids 

** Gordon's currant," which is considered to be a 
hybrid between the CaHfornian and the Missouri 
species. He also gives Cytisus adami as an 
absolutely sterile hybrid, this being a cross 
between two species of Labernum — the common 
and the purple. 

In the case of animals the known hybrids are 
so much less numerous that we are able to furnish 
a list which may be taken as fairly exhaustive. 

Fertile Mammalian Hybrids 

Taking the mammals first, we find that, in 
addition to those cited by Darwin, there are 
several recorded cases of crosses between well- 
defined species which are fertile. 

There is the hybrid between the brown bear 
and the polar bear, which is perfectly fertile. In 
the London Zoological Gardens there is a speci- 
men of this hybrid, also one of this individual's 
offspring by a pure polar bear. 

The stoat has been crossed with the domestic 
ferret, a descendant of the polecat, a very distinct 
species ; the resulting hybrids have nevertheless 
proved fertile. 

The bull American bison produces with the 
domestic cow hybrids known as ** cataloes," 
which are fertile. The reverse cross of the 
domestic bull with the bison cow does not, how- 
ever, succeed at all, which reminds us of what 
happens in the case of finch-hybrids. 


The Making of Species 

Bird fanciers when crossing the canary with 
wild species of finch, almost invariably use a hen 
canary as the female parent, because domesticated 
female animals breed more readily than do captive 
wild ones. 

The domestic yak breeds frequently in the 
Himalayas with the perfectly distinct zebu or 
humped cow of India, and the hybrids are fertile. 
Yet the zebu and the Indian buffalo, living con- 
stantly side by side in the plains of India, never 
interbreed at all. 

Among wild ruminants of this hollow-horned 
family, the Himalayan Argali (Ovis ammon) ram, 
a giant sheep of the size of a donkey, has been 
known to appropriate a herd of ewes of the Urial 
[O. vignei), a very distinct species of the size of 
a domestic sheep. Many hybrids were born, and 
these, in turn, bred with the pure urials of the 
herd, i^cc l^. i i ■-■ 

In our parks the little Sika deer of Japan 
(Cervus sika), a species about the size of the 
fallow-deer, with an even more marked seasonal 
change of colouration and antlers having only 
three tines, breeds with the red deer, and the 
hybrids are fertile. 

In certain parts of Asia Minor the natives 
cross the female one-humped camel with the male 
of the bactrian or two-humped species. The 
hybrids (which are one-humped) will breed with 
the pure species ; but, although the hybrids are 

1 20 

Fertile Bird Hybrids 

strong and useful, the three-quarter bred beasts 
are apparently of little value. 

Fertile Bird Hybrids 

Coming to birds, we are confronted by a 
longer list of fertile hybrids. This is the natural 
outcome of the fact that a greater number of 
bird species have been kept in captivity. 

The oldest known fertile hybrid is that 
between the common and Chinese geese above 
cited, but many others have since been re- 
corded. Even among birds so seldom bred, 
comparatively, as the parrot family, a fertile 
hybrid has been produced, that between the Aus- 
tralian Rosella Parrakeet {Platycercus eximius) 
and Pennant's Parrakeet i^P. elegans). The 
hybrid was first described as a distinct species, 
the Red- mantled Parrakeet {P. erythropeplus). 
These two parrakeets, though nearly allied, are 
very distinct ; Pennant's being coloured red, blue, 
and black, with a distinct young plumage of 
uniform dull green ; the rosella in addition to the 
above colours displays much yellow and some 
white and green. It is, moreover, considerably 
smaller and has no distinct youthful dress. 

The Amherst Pheasant (Chrysolophus amher- 
stice) and the Gold Pheasant (C pictus) have 
long been known as producing hybrids which 
are fertile either inter se or with the parents. 
Here the species are still more distinct ; not only 


The Making of Species 

are the leading colours of the Amherst white and 
green, instead of red and gold, but it is a bigger 
bird with a larger tail and smaller crest, and a 
bare patch round the eyes. 

The Pintail Duck i^Dafila acuta) and the 
Mallard or Wild Duck and its domestic descen- 
dants [Anas boscas), when bred together, produce 
hybrids which have been proved fertile between 
themselves and with the pure pintail. Any 
sportsman or frequenter of our parks can see for 
himself the distinctness of the species concerned. 

The Pied Wagtail [Motacilla lugubris) and the 
Grey Wagtail [M. melanope) have produced 
hybrids in aviaries, which have proved fertile. 
The two species are distinct in every way, as 
all British ornithologists know. 

The Cut-throat Finch [Amadina fasciata) and 
Red-headed Finch [A. erythrocephald) of Africa 
have hybridised in aviaries, and the produce has 
proved fertile. The red-headed finch, among 
other differences, is far larger than the cut-throat, 
and the males have the head all red, not merely 
a throat-band of that colour. 

The Japanese Greenfinch [Ligurinus sinicus) 
which is not green, but brown and grey, with 
bolder yellow wing- and tail-markings than our 
larger European greenfinch, has produced fertile 
hybrids with this latter bird. 

The Red Dove of India [Oenopopilia tranque- 
barica) has produced hybrids with the tame 


The chief colours of this species {CJuysolopJms ainherstice), are white 
and metallic green, so that it is very different in appearance from its 
near ally the gold pheasant. 

Fertile Bird Hybrids 

Collared Dove ( T. risorius) and these have bred 
again when paired with the red species. O, 
tranquebarica, although presenting a general 
similarity to the collared dove, is truly distinct, 
being much smaller, with a shorter tail, and dis- 
playing a marked sex-difference (the male only 
being red, and the female drab). Its voice is 
also utterly unlike the well-known penetrating 
and musical coo of the Collared Dove. 

There is a large class of fertile wild hybrids 
produced between forms differing only in colour, 
such as those between the Hooded Crow (Corvus 
comix) and Carrion Crow (Corvus corone), the 
various species of Molpastes bulbuls, and the 
Indian Roller {Coracias indica) and Burmese 
Roller (C. affints). Indeed, it may be said that 
wherever two such colour-species meet they 
hybridize and become more or less fused. 

In this connection sportsmen, as mentioned 
by Darwin, performed unconsciously a most in- 
teresting experiment when, more than a century 
ago, they introduced largely into their coverts 
the Chinese Ring-necked Pheasant {Phasianus 
torquatus) and the J apanese P. versicolor. So freely 
has the former bred with the common species 
already present there (Phasianus colckicus) that 
nowadays nearly all our English pheasants show 
traces of the cross in the shape of white feathers 
on the neck, or the green tinge of the plumage of 
the lower back. The influence of the Japanese 


The Making of Species 

Green Pheasant (P. versicolor) has been very 
K It is, of course, open to anyone to assert that 

.^^ such crosses are not true hybrids, as the species 
mVA are not fully distinct, but mere colour-mutations. 
f> J^ T\iQ fact of the intermingling, however, is a fatal 
f 0- ^ blow to the theory of recognition marks, since it 
\jS. *\^ demonstrates that merely distinctive colouring is 
f^ Aj,^ not a preventative of cross-breeding. To this 

"^ matter we shall return later. 


Fertile Hybrids among Amphibia 

Our Crested Newt {Afolge cristatd) and the 
Continental Marbled Newt i^M. marmoratd) 
interbreed in France, in the wild state, and the 
resulting hybrid was at first described as a 
distinct species, under the name of Molge blasii. 
These two newts differ greatly in appearance. 
In the Marbled Newt the colouration is brilliant 
green and black above, and shows no orange 
below, thus differing much from that of the 
Crested Newt, which is black above and mottled 
with orange beneath, while the crest of the 
breeding-male of this species lacks the notches 
which are so conspicuous in that of the Crested 


Among insects, M. de Quatrefages states that 
the hybrid progeny of the silk-moths Bombyx 


By periiiissioH of the Avi( iiltici al Society 


(CotuTJiix delegorguei) {Coturnix coroinandelica) 

The markings on the throats of these quails are of the tj'pe usually put down 

as "recognition marks," but as the Harlequin Quail is African and the 

Rain Quail Indian, the two species cannot possibly interbreed. The pattern, 

then, can have no " recognition" significance. 

Limits of Hybridisation 

cynthia and B, arrindia are fertile for eight 
generations when bred inter se. 

Limits to the Possibilities of Hybridisation 

Hybrids can apparently only be produced 
between species of the same natural family. 
The stories of cat-rabbits, deer-ponies, fowl- 
ducks, and similar distant crosses invariably 
break down on close examination. A belief in 
such remote crosses characterized the ancient 
''bestiaries," and still lingers, as witness the 
falsely-reputed crosses alluded to above. 

This belief has no doubt arisen from the fact 
that the domestic breeds of dogs, fowls, etc., 
are popularly confounded with truly distinct 
species. Mongrels are well known to be readily 
produced, and hence the notion arises that 
hybrids between the most widely - separated 
species are possible. 

In practice, the most remote cross of which 
authenticated specimens exist is that between 
the red grouse and the domestic fowl (bantam 
cock). It is true that the grouse are commonly 
ranked by ornithologists as a family distinct 
(Tetraonidae) from that of the pheasants and 
partridges {Phasianidae), to which the fowl 
belongs ; but the relationship is admittedly very 
close, and we doubt if general zoologists would 
countenance the maintenance of the families as 
distinct. Ornithologists are notoriously apt to 


The Making of Species 

over-rate small differences when drawing up a 
classification. It would be therefore safe to say, 
in the present state of our knowledge, that species 
belonging to different natural families cannot 

In some cases multiple hybrids have been 
produced. Thus, at the London Zoological 
Gardens, many years ago, a hybrid between the 
Gayal of India {Bos frontalis) and the Indian 
humped cow mentioned above was put to an 
American bison, and produced a double hybrid 

M. G. Rogeron of Angers bred many hybrids 
from a male pochard and a duck bred from a 
Mallard and a Gadwall. 

More recently, Mr J. L. Bonhote has suc- 
ceeded in combining the blood of five wild species 
of ducks in one individual. 

Mr J. T. Newman has also bred turtle-doves 
containing the blood of three distinct species. 

A cross, which usually results in sterile 
offspring, may in very rare cases produce a fertile 
individual ; thus, Mr A. Suchetet once succeeded 
in obtaining a three-quarter-bred bird from the 
not uncommon hybrid of the tame pigeon and 
tame collared dove [Turtur risorius\ which is 
usually barren, by pairing it with a dove ; but the 
bird thus produced, when again paired with a 
dove, was itself sterile. 

Some of the cases here given seem to encourage 


Characters of Hybrids 

Darwin's view that domestication tends to elimi- 
nate sterility ; but it is doubtful if this can be 
upheld. The hybrid between the Muscovy duck 
{Cairina moschata) and common duck is usually, 
at all events, sterile, like that between the pigeon 
and dove ; yet all these birds have been long 
domesticated. The hybrid between the fowl and 
the guinea-fowl is likewise barren, nor has the 
long domestication of the horse and ass lessened 
the sterility of the mule. 

Some facts may be noted respecting the 
characters of hybrids. In the first place, it is 
important to notice that the characters of the 
hybrid vary according to the sexes of the species 
concerned ; thus, the *' hinny," which is bred 
from a horse and a she-ass, is a different animal 
from the true ''mule," which is bred from the 
jackass and mare, and is inferior to it. 

Similarly, Mr G. E. Weston, a great authority 
on British cage-birds and their hybrids, informs 
us that when hybrids are bred from a male canary 
and a hen goldfinch or siskin — contrary to the 
almost universal practice of using the hen canary 
for crossing — the progeny are inferior in size and 
colour to the hybrids obtained in the ordinary 

Hybrids, in animals at all events, differ from 
crosses between mutations or colour-variations 
in not exhibiting the phenomenon of alternative 
inheritance ; they do not follow one parent or 


The Making of Species 

the other exclusively, but always exhibit some 
blending of the characters of both, which is, 
after all, what might have been expected, since 
well-defined species usually differ in more than 
one character. 

Thus, the cross between the Amherst and gold 
pheasants chiefly resembles the latter, but has 
the ruff white as in the Amherst, while the crest, 
though in form it resembles that of the gold 
species, is not yellow as in that species, nor red 
as in the Amherst, but of an intermediate tint, 
brilliant orange. 

The mule between the horse and ass, as all 
know, combines the shapes of the two parents, 
though in colour it follows the horse rather than 
the ass. 

When two remote species, one or each of 
which possesses some distinctive structural 
peculiarity, are crossed, the hybrid does not 
inherit such points. The guinea-fowl has a 
helmet, and a pair of wattles on the upper 
jaw ; the common fowl a comb, and a pair of 
wattles on the lower jaw ; but in the hybrid no 
comb, helmet, or wattles are present. 

The Muscovy drake has a bare red eye-patch, 
and the male of the common duck curled middle- 
tail feathers ; in the hybrid neither of these 
peculiarities is reproduced. 

In a cross between nearly- related forms, the 
peculiarity of one species may be reproduced in 


Characters of Hybrids 

a modified form in the hybrid ; for instance, in 
that between the blackcock {Tetrao tetrix) and 
the capercailzie (T. urogallus), the forked tail of 
the former reappears to a small extent in the 

Very interesting are those cases in which the 
hybrid resembles neither parent, but tends to be 
like an altogether distinct species, or to have a 
character of its own. Thus the hybrids between 
the pied European and chestnut African shel- 
drakes (Tadorna cornuta and Casarca cana), now 
in the British Museum, bear a distinct resem- 
blance to the grey Australian sheldrake (C tador- 
noides). In pheasants, also, the crosses between 
the common and gold, common and Amherst, 
gold and Japanese, and gold and Reeves' 
pheasants, widely different as all these birds 
are in colouration, are remarkably alike, being 
all chestnut-coloured birds with buff median tail- 
feathers. These may be seen in the British 
Museum. This phenomenon, together with the 
above-noted disappearance of specialised features 
in hybrids, is possibly comparable to the 
"reversion" observed when widely - distinct 
domestic breeds are crossed, and so may give 
us an idea of the appearance of the ancestors of 
the groups of species concerned. 

In the few cases wherein several generations 
of hybrids have been bred inter se, there seems 
to have been no reversion to the original pure 
I 129 

The Making of Species 

types, such as happens when colour-forms are 

M. Suchetet bred hybrid gold = Amherst 
pheasants for four generations, and they retained 
the hybrid character. The young bred by 
Darwin from a pair of common = Chinese geese 
hybrids *' resembled," he says, ''in every detail 
their hybrid parents." 

When hybrids have been — as has far more 
usually been the case — bred back to one 
of the pure stocks, the hybrid characters have 
shown, as might be expected, a tendency quickly 
to disappear. The three-quarter-bred polar bear 
now in the London Zoological Gardens is a 
pure polar save for a brown tinge on the back. 
A three-quarter Amherst = gold pheasant in the 
British Museum is a pure Amherst save for the 
larger crest, and a patch of red on the abdomen. 
When three-quarter-bred pintail = common duck 
hybrids were bred back to the pintail, the off- 
spring " lost all resemblance to the common 
, duck." In the case of the Argali-urial herd of 
wild sheep above-mentioned, after the usurping 
I Argali ram had been killed by wolves, the hybrids 
1 bred with the urials, with the result that the herd 
renewed the appearance of pure urial. 

Thus, except in the very improbable case of a 
family of hybrids going off and starting a colony 
by themselves, the effect of hybridism on the 
evolution of species seems likely to have been 


Wild Hybrids 

nil. It is, however, curious that three-quarter- 
bred animals have rarely, if ever, been recorded 
in a state of nature, though a good many wild- 
bred hybrids are on record. 

This points to some unfitness for the struggle 
for existence even in a fertile hybrid. It is 
necessary to emphasise the fact that wild hybrids 
are always exceedingly rare as individuals, in 
spite of what has been said as to the number of 
recorded crosses. 

More hybrid unions have been noted among 
the duck family than anywhere else in the animal 
kingdom. Nevertheless Finn never once saw a 
hybrid duck for sale in the Calcutta market, 
although for seven years he was constantly on 
the look-out for such forms ; nor does Hume 
record any such specimen in his Game Birds and 
Wild Fowl of India. 

The hybrid which occurs most commonly as 
an individual is that between the blackcock and 
capercailzie, which is recorded yearly on the 
Continent; but it appears to be sterile, and so 
has no influence on the species. 

Wild hybrids between mammals are far rarer 
even than bird hybrids, the only ones which 
seem to be on record being those between the 
Argali and Urial above alluded to ; those between 
the brown and blue hares and the common and 
Arctic foxes. 

A consideration of the phenomena of hybridism 


The Making of Species 

thus leads us to the conclusion that, although 
many hybrids are fertile, the crossing of distinct 
species has exercised little or no effect on the 
origin of species. Even where allied species, like 
the pintail and the mallard ducks, whose hybrid 
offspring is known to be fertile, inhabit the 
same breeding area and occasionally interbreed 
in nature, such crossing does not, for some reason 
or other, appear to affect the purity of the 

Very different, of course, is the effect of cross- 
ing a mutation within a species with the parent 
form ; the offspring are, as we shall see, likely 
to resemble one or other of the parents ; so that, 
if the mutation occur frequently enough and be 
favourable to the species, the new form may in 
course of time replace the old one. 




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 — Domi- 
nance sometimes imperfect — Behaviour of the nucleus of the 
sexual cell — Chromosomes — Experiments of Delage and Loeb 
— Those of Cudnot on mice and Castle on guinea pigs — Sug- 
gested modification of the generally-accepted Mendelian 
formulae — Unit characters — Biological isomerism — Biologi- 
cal molecules — Interpretation of the phenomena of variation 
and heredity on the conception of biological molecules — 
Correlation — Summary of the conception of biological 

WE have seen that variations may be, 
firstly, either acquired or con- 
genital, and, secondly, fluctuating 
or discontinuous. We have further 
seen that acquired variations — at all events in 
the higher animals — do not appear to be in- 
herited, and therefore have not played a very 
important part in the evolution of the animal 
world. Discontinuous congenital variations or 
mutations are the usual starting points of new 
species. It is not unlikely that fluctuating con- 
genital variations, although they do not appear 
to give rise directly to new species, may play a 


The Making of Species 

considerable part in the making of new species, 
inasmuch as they may, so to speak, pave the way 
for mutations. 

We are now in a position to consider the 
exceedingly difficult question of inheritance. We 
know that offspring tend to resemble their 
parents, but that they are always a little different 
both from either parent and from one another. 
How are we to account for these phenomena ? 
What are the laws of inheritance, whereby a 
child tends to inherit the peculiarities of its 
parents, and what are the causes of variation 
which make children differ inter se and from 
their parents ? 

Scores of theories of inheritance have been 
advanced. It is scarcely exaggerating to assert 
that almost every biologist who has paid much 
attention to the subject has a theory of inherit- 
ance which differs more or less greatly from the 
theory held by any other biologist. 

As regards the phenomena of heredity we may 
say Tot homines tot sententice. 

For this state of affairs there is a good and 
sufficient reason. We are not yet in possession 
of a sufficient number of facts to be in a position 
to formulate a satisfactory theory of inheritance. 
A complete theory of heredity must explain, 
among other things, the following phenomena : — 

I. Why creatures show a general resemblance 
to their parents. 


Phenomena of Inheritance 

2. Why they differ from their parents. 

3. Why the members of a family display indi- 
vidual differences. 

4. Why the members of a family tend to 
resemble one another more closely than they 
resemble individuals belonging to other families. 

5. Why *' sports " sometimes occur. 

6. Why some species are more variable than 

7. Why certain variations tend to occur very 

8. Why variations in some directions seem 
never to occur. 

9. Why a female may produce offspring when 
paired with one male of her species and not when 
paired with another male of the species. 

10. Why organisms that arise by partheno- 
genesis appear to be as variable as those which 
are sexually produced. 

11. Why certain animals possess the power of 
regenerating lost parts, while others have not 
this power. 

12. Why most plants and some of the lower 
animals can be produced asexually from cuttings. 

13. Why mutilations are not inherited. 

14. Why acquired characters are rarely, if 
ever, inherited. 

1 5. Why the ovum puts forth the polar bodies. 

16. Why the mother-cell of the spermatozoa 
produces four spermatozoa. 


The Making of Species 

17. Why differences In the nature of the food 
administered to the larvae of ants determines 
whether these shall develop into sexual or neuter 

18. Why the application of heat, cold, etc., to 
certain larvae affects the nature of the imago, or 
perfect insect, to which they will give rise. 

19. Why the females in some species lay eggs 
which can produce young without being fertilised. 

20. Why some species exhibit the phenomena 
of sexual dimorphism, while others do not. 

21. In addition to all the above, a satisfactory 
theory of inheritance must account for all the 
varied phenomena which are associated with the 
name of Mendel. It must explain the various 
facts with which we have dealt in the chapter on 
hybridism, why some species produce sterile 
hybrids when intercrossed, while others give rise 
to fertile hybrids, and yet others form no offspring 
when crossed ; why the hinny differs In appear- 
ance from the mule, etc. 

22. It must explain all the facts which consti- 
tute what is known as atavism. 

23. It must account for the phenomenon of 

24. It must explain the why and the wherefore 
of correlation. 

25. It must tell us the meaning of the 

results of the experiments of Driesch, Roux, 

and others. 


Existing Theories Unsatisfactory 

26. It must render intelligible the effects of 
castration on animals. 

Now, no existing theory of heredity can give 
anything approaching a satisfactory explanation 
of all these phenomena. 

It is for this reason that we refrain from criti- 
cally examining, or even naming, any of them. 

We are convinced that in the present state of 
our knowledge it is not possible to formulate 
anything more than a provisional hypothesis. 

It must not be thought that we consider the 
various theories that have been enunciated to be 
of no value. Erroneous hypotheses are often of 
the greatest utility to science, for they set men 
thinking and suggest experiments by means of 
which important additions to knowledge are 

We now propose to set forth certain facts of 
inheritance, and from these to make a few 
deductions — deductions which seem to be forced 
upon us. 

We would ask our readers to distinguish care- 
fully between the facts we set forth, and the 
conclusions we draw therefrom. The former, 
being facts, must be accepted. 

The interpretations we suggest should be 
rigidly examined, we would say regarded with 
suspicion, and all possible objections raised. It 
is only by so doing that any advance in know- 
ledge can be made. 


The Making of Species 

By inheritance we mean that which an organ- 
ism receives from its parents and other ancestors 
— all the characteristics, whether apparent or 
dormant, it inherits or receives from its parents. 
Professor Thomson's definition — ''all the qualities 
or characters which have their initial seat, their 
physical basis, in the fertilised Qgg cell " — seems 
to cover all cases except those where eggs are 
parthenogenetically developed. 

The first fact of heredity which we must notice 
is that inheritance may take several forms. This 
is apparent from what was set forth in the 
chapter dealing with hybrids. 

In considering the phenomena of inheritance 
it is convenient to deal with crosses in which the 
parents do not closely resemble one another, 
because by so doing we are able readily to 
follow the various characters displayed by each 
parent. It may, perhaps, be urged that such 
crosses occur but rarely in nature. This is true. 
But we should bear in mind that any theory 
of inheritance must explain the various facts of 
cross-breeding, so that, from the point of view of 
a theory of inheritance, crosses are as important 
as what we may term normal offspring. As 
inheritance is so much easier to observe in the 
former, it is but natural that we should begin 
with them. Our deductions must, if they be 
valid ones, fit all cases of ordinary inheritance, 
z,e. all cases where the offspring results from the 


Types of Crosses 

union of parents which closely resemble one 
another. Now, when two unlike forms inter- 
breed, their offspring will fall into one of six 

I. They may exactly resemble one parent, or 
rather the type of one parent, for, of course, 
they will never be exactly like either parent ; 
they must of necessity display fluctuating varia- 
tions. The cases in which the offspring exactly 
resemble one parent type in all respects are com- 
paratively few. They occur only when the 
parents differ from one another in one, two, or 
at the most three characters. Thus when an 
ordinary grey mouse is crossed with a white 
mouse the offspring are all grey, that is to say, 
they resemble the grey parent type. Although 
they are mongrels or hybrids, they have all the 
appearance of pure grey mice. This is what is 
known as unilateral inheritance. 

II. The offspring may resemble one parent 
in some characters and the other in other 
characters. They may have, for example, the 
colour of one parent, the shape of the other, and 
so on. Thus if a pure, albino, long-haired, and 
rough-coated male guinea-pig be crossed with a 
coloured, short-haired and smooth-coated female, 
all the offspring are coloured, short-haired, and 
rough-coated. That is to say, they take after 


The Making of Species 

the father in being rough-coated, but after the 
mother in being pigmented and short - haired. 
This form of inheritance is usually seen only in 
crosses between two types which differ in but 
few of their characters. 

III. The offspring may display a blend of the 
characters of the two parents. They may be 
intermediate in type. They are not of necessity 
midway between the two parents ; one of the 
parents may be prepotent. The crosses between 
the horse and the ass show this well. Both the 
mule, where the ass is the sire, and the hinny, 
where the horse is the sire, are more like the ass 
than like the horse ; but the hinny is less ass- 
like than the mule. The offspring between a 
European and a native of India furnishes a 
good case of blended inheritance ; Eurasians are 
neither so dark as the Asiatic nor so fair as the 

IV. The offspring may show a peculiarity of 
one parent in some parts of the body and the 
peculiarity of the other parent in other parts of 
the body. This is known as particulate inherit- 
ance. The piebald foal, which is the result of a 
cross between a black sire and a white mare, is a 
good example of such inheritance. This does 
not appear to be a common form of inheritance. 

V. The usual kind of inheritance is perhaps 
a combination between the forms II. and III. 


Mendel's Experiments 

In such cases the offspring display some paternal 
characters and some maternal ones, and some 
characters in which the maternal and paternal 
peculiarities are blended. An example of in- 
heritance of this description is furnished by a 
cross between the golden and the amherst 

VI. The offspring may be quite unlike either 
parent. For example, Cuenot found that some- 
times a grey mouse when crossed with an albino 
produces black offspring. 

The first two kinds of inheritance were care- 
fully investigated by Gregor Johann Mendel, 
Abbot of Brunn. The results of his experiments 
were published in the Proceedings of the Natural 
History Society of Brunn, in 1854, but attracted 
very little notice at the time. 

Mendel experimented with peas, of which many 
varieties exist. He took a number of varieties, 
or sub-species, which differed from one another 
in well-defined characters, such as the colour of 
the seed coat, the length of the stem, etc. He 
made crosses between the various varieties, being 
careful to investigate one character only at a 
time. He found that the offspring of such 
crosses resembled, in that particular character, 
one only of the parents, the other parent ap- 
parently exerting no influence on it. Mendel 


The Making of Species 

called the character that appeared in the off- 
spring dominant, and the character which was 
suppressed, recessive. Thus when tall and short 
varieties were crossed the offspring were all tall. 
Hence Mendel said that tallness is a dominant 
character, and shortness a recessive character. 
Mendel then bred these crosses among them- 
selves, and found that some of the offspring 
resembled one grandparent as regards the char- 
acter in question while some resembled the 
other, and he found that those that showed the 
dominant character were three times as numerous 
as those that displayed the recessive character. 
He further found that all those of the second 
generation of crosses which displayed the re- 
cessive character bred true ; that is to say, when 
they were bred together all their descendants 
exhibited this characteristic. The dominant 
forms, however, did not all breed true ; some 
of them produced descendants that showed 
only this dominant character, others, when 
crossed, gave rise to some forms having the 
dominant character and some having the 
recessive character. 

It is thus evident that organisms of totally 
different ancestry may resemble one another in 
external appearance. In other words, part of the 
material from which an organism is developed 
may lie dormant. 

From the above results Mendel inferred, in 



the case of what he called alternating characters, 
that only one or other of the pair can appear in 
the offspring, that they will not blend. If both 
parents display one of the opposing characters, 
the offspring will of course show it. But if one 
parent display one character and the other the 
opposing character, the hybrid offspring will dis- 
play one only, and that which is dominant. The 
other character is suppressed for the time being. 
When, however, these hybrids are bred inter se, 
their gametes or sexual cells split up into their 
component parts, and then the recessives are free 
to unite with other recessives and thus produce 
offspring which show the recessive character. 

His results can be set forth in symbols. 

Let T stand for the tall form and D for the 
dwarf form. Since the offspring are composed 
of both the paternal and maternal gamete, we 
may represent them as TD. But dwarfness is, 
as we have seen, recessive, so that the offspring 
all look as though they were pure T's. When, 
however, we come to breed these TD's inter se, 
the gamete or sex-cell of each individual crossed 
breaks up into its component parts T and D, 
which unite with other free T or D units 
to form TD's or TT's or DD's. What are 
the possible combinations ? A D of one parent 
may meet and unite with a D of the other 
parent, so that the resulting cells will be pure 
D, i.e. DD, and will give rise to pure dwarf 


The Making of Species 

offspring. Or the D gamete from one parent 
may unite with a T gamete from the other 
parent, and the result will be a TD cross, but 
this, as we have seen, will grow up to look like 
a pure T, i.e. will become a tall organism. 
Similarly, a T gamete from one parent may 
unite with a T gamete of the other, and produce 
a pure tall form, or it may unite with a D and 
produce a hybrid TD, which gives rise to a 
tall form. Thus the possible combinations of 
offspring are DD, DT, TD, TT, but all these 
three last contain the dominant T gamete, and 
so develop into tall offspring ; therefore, ex 
hypothesi, we shall have three tall forms pro- 
duced to one dwarf form, but of these three 
tall forms two are not pure, and do not breed 
true. Mendel's experimental results accorded 
with what we should expect to obtain if the 
above explanation were correct. Hence the 
inference that there is such a splitting of the 
gametes in the sexual act seems a legitimate one. 
Mendel's experiments are of great import- 
ance, for they give us some insight into the 
nature of the sexual act. But, as is usual 
in such cases, Mendel's disciples have greatly 
exaggerated the value and importance of his 
work. It is necessary to bear in mind that 
Mendel's results apply only to a limited 
number of cases — to what we may call balanced 
characters. In the case of characters which 


Maturation of the Germ-cells 

do not balance one another, which are, so to 
speak, not diametrically opposed to one another, 
Mendel's law does not hold. A second im- 
portant point is, that the dominance is in many- 
cases not nearly so complete as it should be if 
the Mendelian formula correctly represented 
what actually occurs in nature. Further, the 
segregation of the gametes does not appear to 
be so complete as the above hypothesis requires 
it to be. The phenomena of inheritance seem 
to be far more complex than the thorough-going 
Mendelian would have us believe. 

Let it be noted that it is not to the facts of 
Mendelism, but to some portions of what we 
may call the Mendelian theory, that we take 

Before passing on to consider some of the 
later developments of Mendelism, it is necessary 
for us to set forth briefly certain of the more 
important facts regarding the sexual act which 
the microscope has brought to light. We 
propose to state these only in the merest outline. 
Those who are desirous of pursuing the subject 
farther are referred to Professor Thomson's 

The germ cells, like all other cells, consist of 
a nucleus lying in a mass of cytoplasm. The 
nucleus is composed of a number of rod-like 
bodies, which are called chromosomes, because 
they are readily stainable. 

The Making of Species 

These chromosomes appear, under ordinary 
circumstances, to be joined together end to end, 
and then look Hke a rope in a tangle. 

When a cell is about to divide into two, these 
chromosomes become disjoined and can then be 
counted, and it is found that each cell of each 
species of animal or plant has a fixed number of 
these chromosomes. Thus the mouse and the 
lily have twenty-four chromosomes in each cell, 
while the ox is said to have sixteen of them per 

When a cell divides into two, each of these 
chromosomes splits by a longitudinal fissure into 
two halves, which appear to be exactly alike. 
One-half of every chromosome passes into each 
of the daughter cells, so that each of these is 
furnished with exactly half of each one of the 
rod-like chromosomes. In the cell division, 
which takes place immediately before the male 
gamete or generative cell meets the female 
gamete, the chromosomes do not divide into 
equal halves, as is usually the case. In this 
division half of them pass into one daughter cell 
and half into the other daughter cell, so that, 
prior to fertilisation both the male and the female 
gametes contain only half the normal number of 
chromosomes. In the sexual act the male and 
the female chromosomes join forces and then the 
normal number is again made up, each parent 
contributing exactly one half. 


Experiments of Delage and Loeb 

Biologists, with a few exceptions, seem to be 
agreed that these chromosomes are the carriers 
of all that which one generation inherits from 
another. Thus the cardinal facts of the sexual 
act are, firstly, prior to fertilisation the male and 
the female gamete each part with half their 
chromosomes ; and, secondly, the fertilised cell is 
composed of the normal number of chromosomes, 
of which one-half have been furnished by each 
parent. Thus the microscope shows that the 
nucleus of the fertilised egg is made up of equal 
contributions from each parent. This is quite 
in accordance with the observed phenomena of 

But Delage has shown that a non-nucleated 
fragment of the ovum in some of the lower animals, 
as, for example, the sea-urchin, can give rise to 
a daughter organism with the normal number of 
chromosomes when fertilised by a spermatozoon. 
Conversely, Loeb showed that the nucleus of the 
spermatozoon can be dispensed with. Thus it 
seems that either the egg or the spermatozoon of 
the sea-urchin contains all the essential elements 
for the production of the perfect larva of a 
daughter organism. We are, therefore, driven 
to the conclusion that the fertilised ovum contains 
two sets of fully-equipped units. Only one of 
these seems to contribute to the developing 
organism. If this set happens to be composed 
of material derived from one only of the parents, 


The Making of Species 

we can see how it is that we get unilateral in- 
heritance in the case of a cross. Where, however, 
the units from the two parents intermingle, 
although only one set is active in development, 
the result will be blended inheritance. Thus, we 
may regard the fertilised egg as made up of two 
sets of characters — a dominant set, which is active 
in the production of the resulting organism, and 
a recessive set, which appears to take little or no 
part in the production of the organism. 

This is quite in accordance with Mendelian 

Let X be an organism having the unit char- 
acters A ^ C D ^ F 6^, and let Y be another 
organism having the unit characters ah c de/g. 
Now suppose that these behave as opposed 
Mendelian units, and that the unit characters 
in italics are dominant ones. Then the resulting 
individual will resemble each parent in certain 
unit characters. It may be represented by the 
formula a B c d E f G, but it will contain the 
characters AbCDeFg in a recessive form, 
so that its complete formula may be written 

a Be dEf G\ 

When these hybrids are paired together it will 

u ^ 'u . ^ x. f ABCDEFG 

be possible to get such lorms as AT^pp)T7pp 

and 1 , r^ which exactly resemble the 
a b c d e I g ^ 


Experiments of Cuenot and Castle 

respective grandparents, and these should breed 
absolutely true, if the segregation of the 
gametes is as pure as the Mendel's law seems 
to require. 

There are, however, certain facts, which recent 
experimenters have brought to light, that seem 
to show that the segregation is not so com- 
plete as the law requires. For example, 
the so-called pure extracted forms may be 
found, when bred with other varieties, to have 
some latent characters. Thus Cuenot observed 
that extracted pure albino mice, that is to say, 
those derived from hybrid forms, did not all 
behave alike when paired with other mice. 
Those which had been bred from grey x white 
hybrids behaved, on being crossed, differently to 
those that had been bred from black x white 
hybrids ; and further, those derived from yellow 
X white hybrids yielded yet other results on 
being intercrossed. Castle records similar pheno- 
mena in the case of guinea-pigs, and accordingly 
draws a distinction between recessive and latent 
characters. Recessive characters are those which 
disappear when they come into contact with a 
dominant character, but reappear whenever they 
are separated from the opposing dominant char- 
acter. Latency is defined by Castle as **a con- 
dition of activity in which a normally dominant 
character may exist in a recessive individual or 


The Making of Species 

The ordinary Mendelian pictures a unit 
character in a cross that obeys Mendel's law, 

as follows : — -p the dominant character only 

showing. It seems to us that each unit character 
should be represented as a double entity, thus 
D(D), the portion within the bracket being 
latent. The cross would appear to be repre- 
sented by the formula td/t-^\ since the union 

appears to take the form of the transfer of 
the dormant latent characters. Now an ex- 
tracted pure recessive will, on this hypothesis, 

bear the formula Ty/T\\ When such recessives 


are crossed the two dormant portions will 
ordinarily change places, and never appear, so 
that these extracted recessives will, under 
ordinary circumstances, appear to be as pure 
as the true pure recessives, which are represented 

by the formula r^z-nl 

Now, suppose that, from some cause or other, 
it is possible for the latent D to change places 
with the visible R, it is obvious that the impure 
nature of the extracted and hitherto apparently 
pure recessives will become manifest. This 
seems to be what happens under certain circum- 
stances to the extracted albino mice. They 


Unit Characters 

possess latent the character of their dominant 

MendeHan phenomena force upon us the con- 
clusion that organisms display a number of unit 
characters, each of which behaves in much the 
same way as a radicle does in chemistry, inas- 
much as for one or more of these characters 
others can be substituted without interferino- with 
the remaining unit characters. For example, it 
is possible to replace the chemical radicle NHg 
by the radicle Nag; e.g, (N 113)2804 (ammonium 
sulphate) may be transformed into Na2S04 
(sodium sulphate). 

The conclusion that each organism is com- 
posed of a number of unit characters, which 
sometimes behave more or less independently of 
one another, is one which most biologists who 
have studied the phenomena of inheritance 
appear to have arrived at. Zoologists are mostly 
of opinion that these characters, or rather their 
precursors, exist as units in the fertilised ^^'g. 
Very varied have been the conceptions of the 
nature of these biological units. Almost every 
biologist has given a name to his particular con- 
ception of them. Thus we have the gemmules 
of Darwin, the unit characters of Spencer, the 
biophors of Weismann, the micellae of Naegeli, 
the plastidules of Haeckel, the plasomes of 
Wiesner, the idioblasts of Hertwig, the pangens 
of De Vries, and so on. It is unnecessary to 


The Making of Species 

extend this list. It must suffice that almost 
every investigator of the phenomena of inherit- 
ance beHeves in these units, and calls them 
by a different name. Moreover, each clothes 
them with characteristics according to his taste 
or the fertility of his imagination. 

These units behave in such a way as to sug- 
gest to us an analogy between them and the 
chemical molecules. The sexual act would appear 
to resemble a chemical synthesis in some respects. 
One of the most remarkable phenomena of 
chemistry is that of isomerism. It not in- 
frequently happens that two very dissimilar 
substances are found, upon analysis, to have the 
same chemical composition, that is to say, their 
molecules are found to be composed of the same 
kind of atoms and the same number of these. 
Thus chemists are compelled to believe that the 
properties of a molecule are dependent, not only 
on the nature of the atoms which compose it, but 
also on the arrangement of these within the 
molecule. To take a concrete example : Analysis 
shows that both alcohol and ether are represented 
by the chemical formula CgHgO. In other words, 
the molecule of each of these compounds is made 
up of two atoms of the element Carbon, six of 
the element Hydrogen, and one of the element 
Oxygen. Now, every chemical atom possesses the 
property which chemists term valency, in other 
words, the number of other atoms with which 


Chemical Molecules 

it can directly unite is strictly limited. All atoms 
of the same element have the same valency. 
Monovalent atoms are those which can, under no 
circumstances, unite with more than one other 
atom. The Hydrogen atom is an example of 
such an atom. Divalent atoms, as, for example, 
that of Oxygen, can unite with one other atom of 
similar valency or with two monovalent atoms. 
Similarly, a trivalent atom, such as that of 
Nitrogen, can unite with three monovalent 
atoms. A tetravalent atom, such as that of 
Carbon, can combine with four monovalent 
atoms. There are also pentavalent and hexa- 
valent atoms. Now, by indicating the valency 
of any given atom by a stroke for each mono- 
valent atom with which it is able to combine, 
chemists have been able to represent the mole- 
cule of every compound, or, at any rate, of every 
inorganic compound, by what is known as a 
graphic or structural formula. Thus, ethylic 
alcohol is represented by the formula : — 
H H 

H— C— C— O— H = QHeO, 

H H 

and methylic ether by the structural formula 
H H 

H—C— O— C— H = QH,0. 

H H 


The Making of Species 

The formulae indicate a very different arrange- 
ment of the nine atoms which compose the 
molecule in each case. And to this different 
arrangement the differing properties of the two 
compounds are supposed to be due. A rough 
illustration of the phenomenon of isomerism is 
furnished by written language. Thus, three 
different words can be made from the letters t, 
a, and r, e.g, tar, art, and rat. They also form 
tra, which does not happen to be an English 
word, although it might have been one. 

Among organisms we sometimes observe a 
phenomenon which looks very like isomerism. 
The classical example of this is furnished by 
the butterflies Vanessa prorsa and Vanessa 

At one time these were supposed to belong to 
different species, since they differ so greatly in 
appearance. Vanessa levana is red, with black 
and blue spots. Vanessa prorsa is deep black, 
with a broad yellowish-white band across both 
wings. It is now known that the levana is the 
spring form and the prorsa the summer and 
autumn form of the same species. The pupae of 
levana produce the prorsa form, but Weismann 
found that after being placed in a refrigerator 
they emerged, not 2.^ prorsa, but partly as levana 
and partly as another form intermediate in many 
respects between levana and prorsa, Weismann 
also succeeded, by exposing the winter pupa to a 


Experiments of Grafin von Linden 

high temperature, in making it give rise to the 
prorsa form, and not to the levana form, as it 
would ordinarily do. 

Similar results have been obtained with the 
seasonally dimorphic Pieris napi. Standfuss, 
the Grafin von Linden, and others have obtained 
like results in the case of other seasonally di- 
morphic butterflies. In some instances it has 
been proved that the change in the pigment is a 
purely chemical one ; a similar transformation 
can be effected in the extracted pigment. But, 
we must bear in mind that the changes which 
are induced in this way are not confined to 
colour ; they occur in the marking and shape of 
the wing. 

Even more remarkable is the fact that in some 
sexually dimorphic species a change of tempera- 
ture alters the female, so as to cause her to have 
the outward appearance of the male. For 
example, it has been found that warmth changes 
the colours of the female Rhodocera rhamni and 
Parnassius apollo into the colours of the male. 

By applying rays of strong light, electric 
shock, or centrifuge, the Grafin von Linden was 
able to change the colours of the butterflies to 
which the caterpillars gave rise. Pictet experi- 
mented on twenty-one species of butterflies, or 
rather on their caterpillars, and found that in 
nearly all cases when the caterpillars ate unusual 
food, they developed into butterflies with ab- 


The Making of Species 

normal colouring. Schmankewitsch made the 
discovery that, in the case of the crustacean 
Artemia^ he could produce either of two species 
according to the amount of salt in the water in 
which these creatures were placed. He declared 
that the anatomical differences between the 
species Artemia salina and Artemia milhausenii 
depended solely on the percentage of the salt in 
the surrounding water. He further stated that 
by adding still more salt he could change the 
Artemia into a new genus — Branchipus. More 
recent observers have cast doubt upon these 
results of Schmankewitsch. They, however, 
admit that the degree of salinity of the water has 
some effect on the form of the Artemia, although 
they suggest that factors other than concentration 
affect the result. In any case, it is now well- 
known that changes in the environment effect 
changes in the colouring of many Crustacea. 
Pictet has shown that the alternating wet and 
dry seasons in some tropical countries are the 
cause of, or stimulus that induces, seasonal 
dimorphism in some butterflies. He was able to 
effect changes in the colouring of certain species 
by means of humidity. 

The most important cases, from our point of 
view, are those in which the application of 
heat or cold to a pupa has affected the colour, 
shape, etc., of the emerging butterfly. Here we 
have but one factor, that of temperature. All 


Biological Isomerism 

the material for the formation of the butterfly is 
already stored up in the pupa. The unit char- 
acters, or their precursors, are all there, and they 
take one form or another according to the stimulus 

Phenomena of this kind can, we think, be 
accounted for only on the assumption that the 
unit characters affected are each developed from 
a definite portion of the fertilised egg, that each 
of these portions, these precursors of the unit 
characters, is, like a chemical molecule, made up 
of a number of particles, and that upon the 
arrangement of these particles in its precursor 
in the egg depends the form that the unit char- 
acter derived from it will take. One arrange- 
ment of these particles gives rise to one form of 
unit character, while another arrangement will 
give rise to a totally different form of unit 

Thus, some organisms seem to display a bio- 
logical isomerism akin to chemical isomerism, 
save that the particles which in organisms 
take the place of chemical atoms are infinitely 
more complex. 

In other words, the precursors in the fertilised 
Qgg of each of these unit characters behave in 
some respects like chemical molecules. 

In order to avoid the manufacture of fresh 
terms we may speak figuratively of the germ 
cells as being composed of biological molecules, 


The Making of Species 

which in their turn are built up of biological 
radicles and atoms. These behave in some ways 
like chemical molecules, radicles, and atoms, as 
the case may be. 

It seems legitimate to regard each unit char- 
acter in the adult as the result of the develop- 
ment of one or more of the biological molecules 
which compose the nucleus of the fertilised egg. 
These biological molecules are, of course, a 
million-fold more complex than chemical mole- 
cules. Each biological atom must contain within 
itself a number of the very complex protoplasmic 
molecules. This view of the structure of the 
germ cell seems to force itself upon the observer. 
Notwithstanding this, the conception will have no 
value unless it seems to throw light on the various 
phenomena of heredity, variation, etc. 

Let us then try to interpret some of these. 

Each chemical element is made up of atoms 
which are all of the same kind, but no two 
elements are made up of the same kind of atoms, 
although chemists are now inclined to conceive of 
all the various kinds of atoms as made up of 
varying amounts of some primordial substance. 
In any case, the molecules of chemical compounds 
are made up of various kinds of atoms. With 
biological atoms the case would seem to be 
different. All would appear to be made up of 
the same kind of substance, and the differences 
shown by the various unit characters that go to 


Biological Molecules 

make up an organism would seem to be due to 
the different numbers and the varying arrange- 
ment of the biological atoms which compose the 
molecules from which unit characters are derived. 
This would be quite in accordance with the 
chemical notion of allotropy. Thus, the graphite 
and the diamond molecules are both made up of 
the same kind of atoms. 

But the biological atoms are living, that is to 
say, they are continually undergoing anabolism 
and katabolism, growth and decay. They 
exhibit all the phenomena of life, they must 
grow and divide, and they must absorb nourish- 
ment ; hence it is not surprising that they should 
differ slightly among themselves, that they should 
exhibit the phenomenon of variation. Although 
probably all are composed of the same living 
material, no two are exactly alike, hence the 
molecules formed by them will also differ from 
one another. Thus we can see why it is that all 
organisms exhibit fluctuating variations. 

Very different are the discontinuous variations 
or mutations. These would seem to be due to 
either a rearrangement of the biological atoms in 
the biological molecule or the splitting up of 
the latter into two or more molecules. This, of 
course, is pure hypothesis. Let us take an 
imaginary example. Suppose that a biological 
molecule contains eighteen biological atoms, and 
that these are arranged in the form of an equi- 


The Making of Species 

lateral triangle, six of them going to each side. 
Suppose now, that from some cause or other they 
rearrange themselves to form an isosceles triangle, 
so that only four form the base and seven go to 
each of the remaining sides. Such an arrange- 
ment would give rise to a mutation. Suppose now 
that, from some cause or other, this triangular bio- 
logical molecule were to split up into two triangles, 
each having three atoms to each side, we should 
obtain a still more marked mutation. We are 
far from saying that the atoms in the organic 
molecule ever take such forms. We have merely 
attempted to give rough but simple illustrations 
of the kind of processes which on this hypothesis 
might be expected to take place in the germ cells 
or the fertilised eggs. 

Let us now consider the sexual act from this 
aspect. The various molecules (we speak, of 
course, of biological molecules) of the male 
parent meet those of the female parent, and a 
synthesis occurs, which results in the formation 
of a new organism. When these two sets of 
gametes meet one another, one of several events 
may happen. The gametes may refuse to com- 
bine. This will occur whenever they are of 
very different constitution ; thus it is that widely 
differing species will not interbreed. But it may 
even happen that gametes of individuals of the 
same species may refuse to coalesce on account 
of some peculiarity in the composition of one or 

1 60 

Biological Molecules 

other of them. Secondly, they may be able to 
form some sort of a union, but, owing to their 
diverse nature, the resulting molecules may be 
so complex that they cannot be broken up into 
equal halves, and as this seems to be necessary 
for the sexual act, the resulting organism will be 
sterile. Thirdly, the two sets of gametes may 
enter into a proper union, that is to say, form 
new molecules, but these may be of such different 
structure to the molecules of the gametes, that 
the resulting offspring will be quite unlike their 
parents in appearance. Fourthly, some or all 
the groups of radicles in each gamete may be 
united so closely that in the sexual act they do 
not break up, but enter bodily into the new 
resulting organism. In these circumstances the 
inheritance of the offspring will follow Mendel's 
law\ Fifthly, there may be some slight disturb- 
ance of the molecule, perhaps one or only a few 
atoms will be replaced by those of the other 
gamete. This would give us impure dominance. 

Thus this hypothesis appears to be compatible 
with the various modes of inheritance. 

The curious phenomenon known as prepotency 
would seem also to be quite in accordance with 
the conception. 

In chemical reactions the tendency is for the 
most stable combinations to be formed, so in 

We may probably go farther and say, not 

L i6i 

The Making of Species 

only will the most stable biological molecules be 
formed, but the most stable radicles will dominate 
the molecule. Hence, if any two animals are 
crossed and the offspring show alternate inherit- 
ance, the resulting organism will, in the case of 
each unit character, display the most stable of 
the pair ; in other words, it will take after the 
parent which happens to have the greater 
stability as regards that particular character. 
The difference between the mule and the hinny 
would seem to be explicable on this supposition. 
If the union were like a simple chemical syn- 
thesis it should not make any difference which 
way the cross were made. But if the species 
crossed are of varying stability, and if their 
respective degrees of stability vary with the sex, 
it is easy to see that it will make a difference 
how the animals are crossed. 

In the cases of creatures that obey Mendel's 
law, the most stable form of a unit character will 
presumably be the dominant one. 

One of the most curious of the phenomena of 
inheritance is that of correlation. We shall deal 
with this more fully in Chapter VIII. It will 
suffice here to say that certain characters appear 
to be linked together in organisms. Such seem 
to be transmitted in pairs. The offspring never 
exhibits one of such a correlated couple without 
exhibiting the other also. 

It would thus seem that certain combinations 


Biological Molecules 

of biological atoms, certain molecules, can only 
exist in conjunction with certain other combina- 
tions. This is quite in accordance with the 
teaching of physiologists regarding the inter- 
dependence of the various organs of the body. 
We have now reached the stao^e of the fertilised 
ovum. According to our conception it is a series 
or conglomeration of the precursors of the unit 
characters of the adult. These precursors we 
call biological molecules. Each is of a very com- 
plex nature. Each seems to be composed of 
several portions, only one of which will take 
part in the building up of the body of the off- 
spring, the other portions remaining latent. We 
further conceive that it is possible for the various 
radicles which compose these molecules to ar- 
range themselves in various manners, and with 
each new arrangement a different form of unit 
character will be developed. These molecules, 
then, are built up from radicles derived from 
both parents, the most stable combinations being 
formed and one portion of the molecule domin- 
ating the whole. Under normal circumstances 
this dominant portion of the molecule will give 
rise to a character of a definite type. But it 
seems that other factors may come into play and 
cause a rearrangement of the radicles which 
compose it, and this will result in the formation 
of a unit character different from that to which it 
would ordinarily give rise. 


The Making of Species 

But, it may be objected, if the colour of an 
organism be derived from one of these so-called 
biological molecules, how is it that it affects the 
whole organism, or, at any rate, several of the 
other unit characters? The objection may be 
met in several ways. In the first place, the 
colour-forming molecules may split up into as 
many portions as there are units which it affects, 
and each portion may attach itself to a unit. Or 
the property which we call colouration may not 
be derived from a molecule, it may be an ex- 
pression in the relative positions of the various 
molecules in the fertilised egg. Or the colour- 
determining molecule may secrete a ferment or 
a hormone, and this may be the cause of the 
particular colouring of the resulting organism. 
We do not pretend to say which (if any) 
of these alternative suppositions is the correct 
one. But it seems to us that some such con- 
ception as that which we have set forth is forced 
upon us by observed facts. This conception 
should be regarded not as a theory, but rather as 
an indication of the lines along which we believe 
the study of inheritance could best be made. 

The fertilised ovum has nothing of the shape 
of the creature to which it will give rise. It is 
merely a potential organism, a something which 
under favourable conditions will develop into an 

In the higher animals each individual is either 


Phenomenon of Sex 

of the male or the female sex. A vast amount 
of ingenuity has been expended by zoologists in 
the attempt to ascertain what it is that deter- 
mines sex. Many theories have been advanced, 
but no one of them has obtained anything like 
general acceptance, because its opponents are 
able to adduce facts which appear to be incom- 
patible with it. 

It is tempting to try to interpret the pheno- 
menon of sex on the assumption that the female- 
producing biological molecule or unit is an 
isomeride of the male-producing cell. Certain 
facts, however, seem to negative the idea, as, for 
example, the occasional appearance in an indi- 
vidual of one sex of characteristics of the other 

Possibly the attempts to explain the pheno- 
mena of sex-production on a Mendelian basis 
may prove to be more successful. It seems not 
impossible that each fertilised Qgg contains 
material which is capable of developing into 
male generative organs and material which is 
capable of developing into female generative 
organs, but that only one kind of material, that 
which dominates, succeeds in developing. The 
number of what are known as " X-elements " 
that happen to be present in the fertilised Ggg 
appear to decide which kind of material is to be 

But the problem of the determination of sex, 


The Making of Species 

fascinating though it be, is not one that can be 
discussed adequately in a general work on 
evolution. Those interested in the subject are 
referred to Professor Thomson's Heredity, and 
to the address given by Professor E. B. Wilson, 
of Columbia University, before the American 
Association for the Advancement of Science, 
which was fully reported in the issue of Science, 
dated January 8, 1909. 

Stated briefly, then, our conception is, that 
the fertilised ^^^ is composed of a number of 
entities, to which we have given the name 
" biological molecules," because in certain 
respects their behaviour is not unlike that of 
chemical molecules. 

The units which compose these molecules, 
being made up of protoplasm, are endowed with 
all the properties of life, including the inherent 
instability which characterises all living matter. 

We suggest that the continuous or fluctuating 
variations that appear in the adult organism may 
be the result of individual differences in the 
biological "atoms" that compose the molecule. 

Discontinuous variations, or mutations, on the 
other hand, may be the result of a rearrangement 
of the atoms within the biological molecule. 
Upon what causes this rearrangement it would 
not be very profitable to speculate in the present 
state of our knowledge. To do this would be to 
inquire into the cause of a re-grouping of entities 


Struggle for Nourishment 

of the existence of which we are not certain ! 
For aught we know there may be an intracellular 
struggle for nourishment among the various 
molecules and among the atoms which compose 
the molecules. If one molecule enjoys any 
special advantage over the others the result may 
be an unusual degree of development of the 
resulting unit character ; in other words, the 
result will be a variation in the organism. This 
variation may prove favourable or unfavourable 
to its possessor. 

Certain phenomena seem to point to a struggle 
for nourishment between the oferminal and the 
somatic portions of the egg, between the parts from 
which the sexual cells of the resulting organism 
are produced and those which give rise to the body 
of the organism. Each molecule may strive, so 
to speak, to increase at the expense of the others. 
Thus, great size in an organism is likely to be 
produced at the expense of the germinal cell- 
forming molecules. In other words, great size in 
an organism would be incompatible with exces- 
sive fecundity. This is what we observe in 
nature. On the other hand, poor development 
of bodily tissue, as in the case of intestinal para- 
sites, would be correlated with great fecundity. 
Some organisms are mere sacs full of eggs. 

Success in the struggle for nourishment of one 
molecule might be shared by the other molecules 
near to it, hence the phenomena of correlation. 


The Making of Species 

It is thus conceivable that, in a brood consist- 
ing of several individuals, a particular molecule 
or set of molecules in one of the individuals may 
receive more than its share of nourishment, and 
this will result in the organs of that individual 
which spring from the well-nourished molecules 
being exceptionally well developed. Thus arises 
the phenomenon of differences between the 
members of a litter or brood. 

Natural selection will tend to eliminate those 
individuals in which the resulting variation is an 
unfavourable one. If the environment is such, 
as in the case of an internal parasite, that the 
production of germ cells is the most necessary 
function of the organism, then those individuals 
in which the germ-forming molecules increase at 
the expense of the body-forming ones will tend 
to be preserved. This would cause the pheno- 
menon which biologists term degeneration. 
The nourishment of the various biological 
molecules may possibly depend on their relative 
positions in the egg. Those in a favourable 
position will then tend to develop at the expense 
of the others. This will result in variation along 
definite lines. Each succeeding generation will 
tend to an increased development of that par- 
ticular organ to which the favourably-situated 
molecule gives rise. This process may continue, 
as in the case of the horns of the Irish elk, until 
the development of that particular organ becomes 


Origin of Mutations 

so excessive as to be positively injurious ; then 
natural selection will step in and eliminate the 
species. But before this happens, something 
may cause a rearrangement of the biological 
molecules in the fertilised egg, and thus a muta- 
tion may arise, which, so to speak, strikes out a 
new line. 

Finally, on this conception there may be some 
sort of connection between fluctuating variations 
and mutations. We can picture the fluctuating 
variations being piled up, one upon the other, 
until there results a rearrangement of the atoms 
in one or more of the biological molecules which, 
in turn, causes a mutation. 

Occasionally this remodelling, as it were, of 
one biological molecule may affect certain of the 
other molecules, and thus lead to correlated 




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 
Miillerian 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 ex- 
aggerated — 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 regard- 
ing the colouration of animals — Through the diversity of 
colouring of organisms something like order runs — The con- 
. nection between biological molecules and colour — Tylor on 
colour patterns in animals — Bonhote's theory of pcecilo- 
meres — Summary of conclusions arrived at. 

SINCE the publication of The Origin of 
Species, naturalists have paid much 
attention to the colouration of animals 
and plants, with the result that a large 
majority of scientific men to-day hold the belief 
that all, or nearly all, the colours displayed 


Robinson on Protective Colouring 

by animals are of direct utility to them, 
and are therefore the direct result of natural 
selection ; a few would add, ** and of sexual 

*' Among the numerous applications of the 
Darwinian theory," writes Wallace, *' in the 
interpretation of the complex phenomena, none 
have been more successful than those which 
deal with the colours of animals and plants." 

We readily admit that the Darwinian theory 
has thrown a great deal of light on the pheno- 
menon of animal colouration ; it has reduced to 
something like order what was before Darwin's 
time chaos. While admitting this we feel con- 
strained to say that many naturalists, especially 
Dr Wallace and Professor Poulton, have pushed 
the various theories of animal colouration to 
absurd lengths. As Dr H. Robinson truly says 
{Knowledge, January 1909), ''It seems to have 
been taken for granted, and some even of 
Dr Wallace's writings may be interpreted in 
this sense, that protective colouring is necessary 
to the continued existence of every species, and 
that, sexual colouration apart, it is incumbent on 
naturalists to offer ingenious speculations in this 
sense to account for the appearance even of the 
most bizarre and conspicuous beasts. Thence it 
has been but a short step to the announcement 
of those speculations as further evidence in favour 
of natural selection, and of various assumptions 


The Making of Species 

made in the speculative process as indisputable 

The result of this is that men have ceased to 
regard the Neo- Darwinian ^ theories of protective 
colouration, mimicry, and recognition markings 
as mere hypotheses which seem to throw light on 
certain phenomena in the organic world. These 
theories have assumed the rank of laws of nature. 
To dispute them would seem to be as futile as 
to assert that the earth is fiat. To take exception 
to them would appear to be as ridiculous as to 
object to Mont Blanc. To dare to criticise them 
is heresy of the worst type. 

Be this as it may, scientific dogma or no 
scientific dogma, scientific opinion or no scientific 
opinion, we have dared to weigh these theories 
in the balance of observation and reason, and have 
found them wanting. We have examined these 
mighty images of gold, and silver, and brass, and 
iron, and found that there is much clay in the 

We shall devote this chapter to lifting the 
hem of the garment of sanctity that envelopes 
each of these images, and so expose to view the 
clay that lies concealed. 

We propose, first, to set forth in outline what 

1 In this chapter we use the word Neo-Darwinism in its usually- 
accepted sense, i.e. as a name for that which should be called 
Wallaceism, for the doctrine of the all-sufficiency of natural 


Cryptic Colouring 

we trust will be considered a fair statement of 
the various theories of animal colouration which 
are generally accepted to - day, then to show 
up the various weak points in these, and lastly, 
to endeavour to ascertain whether there are not 
some alternative explanations in certain cases to 
which the generally - accepted theory does not 


Neo- Darwinians divide the various forms of 
colouration into three great classes : — ( i ) Cryptic 
colouring, or protective and aggressive resem- 
blances ; (2) sematic colours, or warning and 
recognition colours ; and (3) pseudo-sematic 
colours, or mimicry. A tabular statement of 
this scheme of colouring will be found on pp. 
293-7 of Professor Poulton's Essays on 

As regards class (i), Neo-Darwinians point 
out that the great majority of animals are so 
coloured as to make them very difficult to see in 
their natural environment, hence the whiteness 
of the creatures which inhabit the snow-bound 
Arctic regions, the sandy colour of desert animals, 
the spotted coats of creatures which live among 
trees, the striped markings of animals which 
spend their lives amid long grass, and the trans- 
parent blueness of pelagic animals. The theory 
is that all kinds of animals, whether those that 
hunt or those that are hunted, derive much ad- 
vantage from being coloured like their environ- 


The Making of Species 

ment. The hunted creatures are thereby the 
better able to elude the vigilance of their foes, 
while those that hunt are in a position to take 
their quarry by surprise ; so that natural selection 
has caused them all to assimilate to the hues 
of their surroundings. Neo-Darwinians point 
to the fact that some Arctic animals are brown 
in the summer to match the ground from 
which the snow has melted, and turn white in 
winter to assimilate with their snowy background. 
Naturalists further cite, as evidence in favour of 
this theory, the case of those creatures which 
imitate inanimate objects, such as leaves and 
twigs, and thereby escape the observation of 
their foes. 

Thus, the great majority of animals are sup- 
posed to be cryptically coloured, that is to say, 
coloured so as to be, if not quite invisible, 
at least very inconspicuous in their natural 

It is, however, generally admitted that many 
creatures are not cryptically coloured. Some, 
indeed, seem to be coloured in such a way as to 
render them as conspicuous as possible. The 
Neo-Darwinians declare that there is a reason 
for this. '' If," writes Professor Milnes Marshall 
(page 133 of his Lectures on the Darwinian 
Theory), '' an animal, belonging to a group liable 
to be eaten by others, is possessed of a nauseous 
taste, or if an animal, such as a wasp, is specially 


Warning Colouration 

armed and venomous, it is to its advantage that 
it should be recognised quickly, and so avoided 
by animals that might be disposed to take it as 

'* Hence arises warning colouration, the ex- 
planation of which is due to Wallace. Darwin, 
who was unable to explain the reason for the 
gaudy colouration of some caterpillars, stated 
his difficulty to Wallace, and asked for sug- 
gestions. Wallace thought the matter over, 
considered all known cases, and then ventured to 
predict that birds and other enemies would be 
found to refuse such caterpillars if offered to 
them. This explanation, first applied to cater- 
pillars, soon extended to adult forms, not only of 
insects, but of other groups as well. . . . Insects 
afford many admirable examples of warning 
colours, and many well-known instances occur 
among butterflies. The best examples of these 
are found in three great families of butterflies — 
the HeliconidcB, found in South America, the 
DanaidcE, found in Asia and tropical regions 
generally, and the Acrceidce of Africa. These 
have large but rather weak wings, and fly slowly. 
They are always very abundant, all have con- 
spicuous colours or markings, and often a peculiar 
form of flight, characters by which they can be 
recognised at a glance. The colours are nearly 
always the same on both upper and under sur- 
faces of the wings ; they never try to conceal 


The Making of Species 

themselves, but rest on the upper surfaces of 
leaves and flowers. Moreover, they all have 
juices which exhale a powerful scent ; so that, if 
they are killed by pinching the body, a liquid 
exudes which stains the fingers yellow, and leaves 
an odour which can only be removed by re- 
peated washing. This odour is not very offen- 
sive to man, but has been shown by experi- 
ment to be so to birds and other insect-eating 

" Warning colours are advertisements, often 
highly coloured advertisements, of unsuitability 
as food. Insects are of two kinds — those which 
are extremely difficult to find, and those which 
are rendered prominent through startling colours 
and conspicuous attitudes. Warning colours 
may usually be distinguished by being con- 
spicuously exposed when the animal is at rest. 
Crude patterns and startling contrasts in colour 
are characteristically warning, and these colours 
and patterns often resemble each other ; black 
combined with white, yellow, or red, are the 
commonest combinations, and the patterns usually 
consist of rings, stripes, or spots." 

We trust that we shall be forgiven for this 
lengthy quotation. Our object in reproducing so 
large an extract is to allow the Neo- Darwinians 
to speak for themselves. Were we to state their 
theory in our own words, we might perhaps be 
charged with stating it inaccurately. We should 


Batesian Mimicry 

add that, even as natural selection is supposed to 
have been the cause of conspicuous colouring in 
some organisms, so has it caused others to assume 
intimidating attitudes or emit warning sounds, 
such as a hiss, when attacked. 

We now come to the third great class of 
animal colours — mimetic colours. Mimicry is 
of two kinds, known respectively as Batesian 
and Mullerian mimicry, after their respective 

It has been found that some apparently 

warningly coloured butterflies and other creatures 

are palatable to insectivorous animals. The 

explanation given of this is that these showy but 

edible butterfles '* mimic," that is to say, have the 

appearance of, show a general resemblance to, 

species which are unpalatable. This is known as 

Batesian mimicry. " Protective mimicry," writes 

Professor Poulton [Essays on Evolution, p. 361), 

"is here defined as an advantageous superficial 

resemblance of a palatable defenceless form to 

another that is specially defended so as to be 

disliked or feared by the majority of enemies 

of the groups to which both mimic and 

model belong — a resemblance which appeals 

to the senses of animal enemies . . . but 

does not extend to deep-seated characters, 

except when the superficial likeness is affected 


As Wallace has pointed out, five conditions 
M 177 

The Making of Species 

must be satisfied before such protective mimicry 
can occur : — 

'* I. That the imitative species occur in the 
same area and occupy the same station as the 
imitated. 2. That the imitators are always the 
more defenceless. 3. That the imitators are 
always less numerous in individuals. 4. That 
the imitators differ from the bulk of their allies. 
5. That the imitation, however minute, is ex- 
ternal and visible only, never extending to 
internal characters or to such as does not 
affect the external characters." {^Darwinism, 
Chap. ix.). 

Thus the mimic is supposed to deceive his 
enemies by deluding them into the belief that he 
is the inedible species which they once tried to 
eat and vowed never again to touch, so nasty 
was it. The mimic, then, may be compared to 
the ass in the lion's skin. Needless to say, this 
mimicry is quite unconscious. It is supposed 
to have been developed by natural selection. 
Every popular book on Evolution cites many 
examples of such mimicry. We may there- 
fore content ourselves with mentioning but a 

Our common wasps are copied by a beetle 
{Clytus arietis), active in movement and banded 
black and yellow, and by several yellow-barred 
hover-flies [Syrpktdae) ; and the bumble-bee 
by a clear-winged moth (Sesia fuci/ormis). 


Examples of Mimicry 

There is, indeed, a whole group of these clear- 
winged moths, resembling bees, wasps, and other 
stinging hymenoptera. The common Indian 
Danaid butterfly, Danais chrysippus, is marvel- 
lously reproduced by the female of Hypolimnas 
misippus, a form allied to our Purple Emperor. 
The male of this is black, with white blue- 
bordered patches, the female chestnut, edged 
with black and with white spots at the tips of 
the wings, as in the Danais. Finn has shown 
experimentally that this species is liked by 

Another common Indian Danaid {D. limniace), 
black, spotted with pale green, is imitated, though 
not very closely, by the female of one of the 
** white " group, Nepheronia hippia. Finn found 
that this insect was eaten freely by birds, and 
that the common jungle-babbler (Crater opus 
canorus) was deceived by the mimicry of the 
female. The very nauseous Indian swallow-tail 
i^Papilio arts to lo chics:) is closely imitated by another 
swallow-tail [P. polites\ both having black wings 
marked with red and white ; P. aristolochicF, 
however, has a red abdomen. This difference 
was not noticed by two species of Drongo-shrikes 
(Dicrurus ater and Dissemurus paradiseus\ to 
which the butterflies were offered ; but the Pekin 
robin [Liothrix luteus) — a very intelligent little 
bird — did not fail to pick out and eat the mimic, 
though it was deceived by the marvellously 


The Making of Species 

perfect imitation of Danais chrysippus, by the 
female of the Hypolimnas. 

Such resemblances can therefore be effective. 

The cases of mimicry usually quoted include 
very few among mammals, probably, as Beddard 
suggests, because the species of that class are 
relatively few. 

The insectivorous genus Tupaia is supposed to 
mimic the squirrels, which it much resembles as 
regards form in all respects save the long muzzle ; 
the idea being that squirrels are so active that 
carnivorous animals find it hopeless to pursue 

On the other hand, there is a squirrel [Rkino- 
sciurus tupaioides) which is supposed to mimic 
the tupaias ! It has a similar long muzzle, 
and the light shoulder-stripe which is a common 
marking in tupaias. But why the squirrel, 
one of the group imitated, should in turn become 
an imitator is not explained. 

The true interpretation of the resemblance is 
probably that both squirrels and tupaias are 
adapted to a life in trees. Like profession begets 
like appearance : the ground-living shrews much 
resemble mice, and the moles find representatives 
in mole-like rodents. 

Another case, however, wherein true mimicry 
may have come into play is that of the South 
American deer (Cervus paludosus) which singu- 
larly resembles in colouration the long-legged 

1 80 

Miillerian Mimicry 

wolf or Aguara-guaztt (Canis jubatus). Both 
these species are chestnut in colour, with the 
front of the legs black, and the ears lined 
with white hair ; both inhabit the same regions 
in South America. 

The second kind of mimicry — Miillerian mimi- 
cry — is where one unpalatable creature resembles 
another. This form of mimicry is named after 
Fritz M tiller, who suggested the explanation now 
usually accepted, namely, that " Life is saved by a 
resemblance between the warning colours in any 
area, inasmuch as the education of young inex- 
perienced enemies is facilitated, and insect life 
saved in the process." ''It is obvious," writes 
Poulton (p. 328 of Essays on EvolMtion), ''that 
the amount of learning and remembering, and 
consequently of injury and loss of life involved in 
these processes, are reduced when many species 
in one place possess the same aposematic colour- 
ing, instead of each exhibiting a different danger 
signal. . . . The precise statement of advantage 
was made by Mr Blakiston and Mr Alexander, 
of Tokio. ' Let there be two species of insects 
equally distasteful to young birds, and let it be 
supposed that the birds would destroy the same 
number of individuals of each before they were 
educated to avoid them. Then if these insects 
are thoroughly mixed and become undistinguish- 
able to the birds, a proportionate advantage 
accrues to each over its former state of existence. 


The Making of Species 

These proportionate advantages are inversely in 
the dupHcate ratio of the respective percentages 
that would have survived without the mimicry.' " 

This is rather a cumbrous method of saying 
that if there are in a locality a number of young 
birds, and each of these has to learn by ex- 
perience which insects are edible and which are 
not, each will, if it learns by one example, devour 
one insect of any given pattern. Now, if two 
species of inedible insects have this pattern, they 
will between them lose only one member in the 
educating process of each bird, whereas if each 
species of insect had a colouration peculiar to 
itself, each species would lose a whole individual 
instead of half a one. There can be no doubt 
that such a livery of unpalatability is of some 
advantage to its possessors. 

It has been shown experimentally that hand- 
reared young birds have to acquire their know- 
ledge of flavours and colours by experiment. 

It is well known that in many species the 
male and the female are not coloured alike. 
Such species are said to exhibit sexual 
dimorphism. In these cases it is usually 
the male that is more conspicuously coloured. 
Darwin felt that the theory of natural selection 
could not satisfactorily account for this phe- 
nomenon, so put forward the supplementary 
theory of sexual selection. On this hypothesis 
the females are supposed to be able to pick and 


Danger Signals 

choose their mates, and to select the most beauti- 
ful and ornamental ones, hence the greater 
showiness of these in most sexually dimorphic 
species'. Wallace does not accept this theory. 
He thinks it unnecessary. He looks upon the 
brilliant colouring of the males as due to their 
superior vigour ; moreover, he says that it is the 
hen that sits upon the eggs, and so requires a 
greater degree of protection than the male, and 
therefore natural selection has not permitted her 
to develop all the ornaments displayed by the 
cock. With the phenomenon of sexual dimor- 
phism we shall deal at length in the next 

Dr Wallace recognizes yet another exception 
to the rule that animals are cryptically coloured. 
Many creatures possess on the body markings 
which tend to render them conspicuous rather 
than difficult to see. Where such markings 
occur on gregarious animals, Wallace believes 
that they have been evolved by natural selection, 
either to enable their possessors to recognize one 
another, or to act as a danger signal to their 
fellows. The white tail of the rabbit is believed 
by Wallace to serve as a danger signal. The 
first member of the company to espy the approach- 
ing foe takes to his heels, and, as he moves, his 
white tail catches the eye of his neighbour, who 
at once follows him, so that, in less time than it 
takes to tell, the whole company of rabbits is 


The Making of Species 

scampering towards the burrow, thanks to the 
white under-surface of the tail. 

Even as Wallace out- Darwin's Darwin, so does 
Mr Abbott Thayer, an American naturalist and 
artist, out- Wallace Wallace. That gentleman 
seems to be of opinion that all animals are 
cryptically or, as he calls it, concealingly or obliter- 
atively coloured. Even those schemes of colour 
which have hitherto been called conspicuous are, 
he asserts, " purely and potently concealing " 
when looked at properly, that is to say, with the 
eye of the artist. 

Lest it be thought unnecessary to criticize a 
hypothesis which appears to be based upon the 
assumption that animals see with the eye of the 
artist, we may say that Professor Poulton writes 
approvingly of Thayer's theory. He frequently 
alludes to it in his Essays on Evolution^ and he 
published an account of it in the issue of Nature, 
dated April 24, 1902. Moreover the hypothesis 
has been enunciated in such scientific journals 
as The Atik (1896) and The Year-Book of the 
Smithsonian Institution (1897). 

Thayer asserts that all animals, or at any rate 
the great majority, including many that are 
usually supposed to be conspicuously coloured, 
are in reality obliteratively coloured — that is to 
say, coloured in such a way that the effects of 
light and shade are completely counteracted, with 
the result that they are invisible. 


Obliterative Colouring 

It Is possible, says Mr Thayer, to almost 
obliterate a statue in a diffused light, by putting 
white paint on the surfaces in darkest shadow 
and dark paint on the most brightly lighted 
parts, all in due proportion. Now this is pre- 
cisely what nature is supposed by Mr Thayer to 
have done for all her creatures. 

It is well known that a great many animals, as 
for example the Indian black-buck and the hare, 
are coloured on the upper side and white below. 
This is called by Mr Thayer the principle of the 
gradation of colour. It runs, he declares, all 
through the animal world, and is "the main 
essential step toward making animals incon- 
spicuous under the descending light of the sky." 

Animals, he contends, are not protectively 
coloured to look like clods or stumps or like 
surrounding objects, they are simply oblitera- 
tively coloured — coated, as it were, with invisible 

To quote from The Century Magazine (1908) : 
" Whales, lions, wolves, deer, hares, mice ; 
partridges, quails, sandpipers, larks, sparrows ; 
frogs, snakes, fishes, lizards, crabs ; grasshoppers, 
slugs, caterpillars— all these animals, and many 
thousands more, crawl, crouch, and swim about 
their business, hunting and eluding, under cover 
of this strange obliterative mask, the smooth and 
perfect balance between shades of colour and 
degrees of illumination." 


The Making of Species 

Nature having thus visually unsubstantial ized 
the bodies of animals, so that, if seen at all, they 
look flat and ghostly, does not stop there. From 
solid-shaded bodies they have been converted, 
as it were, into flat cards or canvases, and, to 
complete the illusion of obliteration, pictures 
of the background — veritable pictures of the 
more or less distant landscape — have been 
painted on their canvases ! Such in effect are 
the elaborate "markings of field and forest 

Again he writes : " Brilliantly changeable or 
metallic colours are usually supposed to make 
the birds that wear them conspicuous, but nothing 
could be further from the truth. Iridescence is, 
indeed, one of the strongest factors of conceal- 
ment. The quicksilver-like intershifting of many 
lights and colours, which the slightest motion 
generates on an iridescent surface, like the back 
of a bird or the wing of a butterfly, destroys the 
visibility of that wing or back as such and causes 
it to blend inextricably with the gleaming and 
scintillating labyrinthine-shadowed world of wind- 
swayed leaves and flowers.'^ 

According to Thayer, the skunk, which for 
years has been an important item of the stock-in- 
trade of the advocates of the theory of warning 
colouration, is an excellent example of obliterative 
colouring, since its enemies are supposed to mis- 
take for the sky-line the line of junction between 


Obliterative Colouring 

the white fur of the back and the dark fur of the 
sides. Similarly the crocodiles are supposed to 
mistake a flamingo for the sky at sunrise or at 
sunset ! 

There is doubtless something in this theory of 
obliterative colouration. 

Any one can see, by paying a visit to the South 
Kensington Museum, that an animal which is of 
a lighter colour below than above, is less con- 
spicuous in a poor light than it would be were 
it uniformly coloured. There is then no doubt 
that this scheme of colour, which is so common 
in nature, has some protective value. 

To this extent has Mr Thayer made a valuable 
contribution to zoological science. But when 
he informs us that obliterative colouring is a 
** universal attribute of animal life," we feel 
sorely tempted to poke fun at him. 

We would ask all those who believe in the 
universality of obliterative colouring to observe 
a flock of rooks wending their way to their 
dormitories at sunset. 

Let us now pass on to the examination of the 
more orthodox theories of animal colouration. 

Objections to the Theory of Cryptic 

Before criticising the theory of cryptic colour- 
ing, we desire to state distinctly that we admit 


The Making of Species 

that, where other things are equal, it is of 
advantage to all creatures which hunt or which 
are preyed upon to be inconspicuous. If difficult 
to distinguish amid their natural surroundings, 
the former are likely to secure their prey readily, 
and the latter have a chance of escaping from 
their enemies. Our quarrel is with the theory of 
cryptic colouring as it is enunciated by many 
Neo- Darwinians, with the theory that every hue, 
every marking, every device displayed by an 
organism is of utility to the organism and has 
been directly developed by natural selection. 

The extreme advocates of the theory of cryptic 
colouring have greatly exaggerated the degree 
in which animals are assimilated to their natural 

We grant that a great many creatures, which 
when seen in a menagerie appear very con- 
spicuous, are the reverse of conspicuous when 
standinor motionless amid their natural surround- 
ings. As Beddard has pointed out, it is often 
not easy to find a sixpenny piece which has been 
dropped on the carpet, but the reason for this is, 
not that the coin is protectively coloured, but 
that any small object, no matter how coloured, 
is difficult to distinguish amid a variegated 
environment. The assumption of a white 
winter coat by many organisms that live in 
northern latitudes has been cited, again and 
again, as showing how important it is for an 


Fauna of Polar Regions 

animal to be protectively coloured. If, it is 
urged, those creatures that live in lands which 
are covered in snow for half of the year have 
become white in winter by the action of natural 
selection in order to escape their foes, it is 
obviously of paramount importance to all 
creatures that they should be cryptically 
coloured. Popular books on natural history 
convey the impression that during winter the 
snow-clad, ice-bound Arctic regions are peopled 
by a fauna whose fur or hair rivals in whiteness 
the snowy mantle of the earth. The impression 
thus conveyed is misleading. It is true that an 
unusually large percentage of the animals that 
inhabit the polar regions are white in winter, but 
the majority of the creatures which dwell there 
do not assume the white garb of winter. 

As the fauna of the polar regions is a small 
one, we are able to give lists of all the birds and 
mammals which dwell in the Arctic and the 
Antarctic regions. We have arranged these in 
in three columns. In the first are placed those 
creatures which are white throughout the year, in 
the third those that retain their colour through 
the winter, while the middle column contains 
those forms which change their colouring with 
the season. 


The Making of Species 




Changing with the 


Polar Bear. 

Arctic Fox (most 

Arctic Fox (some- 

Arctic Fox (some 




Arctic Lemming. 


White Whale or 






Blue Hare. 






Greenland Whale. 


Ivory Gull. 

Black Guillemot. 

Sea Eagle. 

Snowy Owl. 


Greenland Red- 


Snow Bunting 

poll (very pale). 

Snow Goose. 

(whitest in 

All Arctic Geese 

summer !). 

and Ducks other 


than S n ow 

Little Auk (throat 


only becomes 



Brunnich's Guille- 
Fulmar Petrel. 

Ross's Gull. 
Glaucous Gull 

(very pale). 


Antarctic Fauna 




Changing with the 


Antarctic White 
Seal {Lob don 
in some cases. 


Other Seals than 



Snowy Petrel. 
Giant Petrel (some 

Chick of Emperor 



Skua Gull. 
Giant Petrel 

Other Petrels. 

It will be observed that the third column con- 
tains the largest number of forms. It is thus 
evident that the whiteness of the Arctic and 
Antarctic faunas in winter has been greatly- 

The Arctic fox appears in all three columns, as 
the creature seems to fall into three races — a 
permanently white race, a permanently coloured 
race, and a seasonally dimorphic race. 

Of the creatures set forth in the middle column 
of the above tables all are whiter in winter than 
in summer with the exception of the snow bunt- 


The Making of Species 

ing, who sets at naught the theory of cryptic 
colouring by turning darker in winter ! The 
same may be said of the Alpine chamois. 

The advocates of the theory of protective 
colouring assert that the creatures which do not 
turn white in winter are strong and active animals 
which have no enemies to fear. 

This contention is met by F. C. Selous as fol- 
lows {African Nature Notes and Reminiscences ^ 
p. 9) : " According to the experience of Arctic 
travellers, large numbers of young musk oxen 
are annually killed by wolves. . . . Nothing, I 
think, is more certain than that a far smaller per- 
centage of so-called protectively coloured giraffes 
are killed annually by lions in Africa than of 
musk oxen by wolves in Arctic America." 

Another difficulty which confronts the Neo- 
Wallaceian school is that, ex hypothesi, the 
assumption of the white coat was gradual. 
Hence the change in the direction of white- 
ness cannot, in its first beginning, have been 
of perceptible utility to an organism. How 
then can natural selection have operated on it .'* 

The transparency of pelagic organisms is fre- 
quently cited as exemplifying cryptic colouring. 
We all know that the common jelly-fish is as 
transparent as glass. Floating on the surface of 
the ocean are millions of tiny organisms, so 
transparent as to be invisible to the human eye. 
At first sight this certainly appears to be a 


Pelagic Organisms 

remarkable case of protective colouring. Un- 
fortunately, nearly all the more highly developed 
forms display conspicuous pigment (as in most 
jelly-fish) in some part of the body. 

'* An animal floating about in the sea," writes 
Beddard, " perfectly transparent, but decked with 
dense black patches, of the size of saucers, would 
betray its whereabouts even to the least observant ; 
if the observer were stimulated by hunger or fear, 
the conspicuousness would not be lessened. . . . 
Besides the internecine warfare which is con- 
tinually going on amongst the smaller surface 
organisms, they are devoured wholesale by the 
larger pelagic fish, and by whales and other 
Cetacea. A whale, rushing through the water 
with open mouth and gulping down all before 
him, is not the least inconvenienced by the 
invisibility of the organisms devoured in such 
enormous quantities ; nor do a solid phalanx of 
herring or mackerel stop to look carefully for 
their food : they take what comes in their way, 
and get plenty in spite of * protective absence of 

*' If the transparency of the pelagic organisms be 
due entirely to natural selection, it is remarkable 
that there is so little modification in this direction 
among the species inhabiting the bottom at such 
depths as are accessible to the sun's rays ; the 
advantage gained by this transparency and con- 
sequent invisibility would be equally great. And 
N 193 

The Making of Species 

yet this is not the case ; the bulk of the bottom 
fauna of the coasts are brilHantly coloured animals, 
and those that show any protective colouring at 
all appear to be coloured so as to resemble stones 
or sea- weeds." ^ 

Before leaving the subject of marine animals, 
we may point out that the majority of the 
creatures that live in the everlasting blackness of 
the depths of the ocean display exceedingly con- 
spicuous colouring, and this colouring seems to be 
constant. In such cases the colouring cannot be 
useful as such to its possessors. The same may 
be said of the colour of blood, or of the colouring 
of the internal tissues of all organisms. We 
must not lose sight of the fact that every 
organism, and every component part thereof, 
must of necessity be either of some colour or 
perfectly transparent. It seems to us that since 
the appearance of The Origin of Species zoologists 
have tended to exaggerate the importance of 
colouring to organisms ; they frequently speak 
of it as though it were the one and only factor in 
the struggle for existence. It is on this account 
that they feel it incumbent upon them to find 
ingenious explanations for every piece of colour- 
ing displayed by every plant or animal. 

The tendency to exaggerate the importance to 
an animal of its colouring is doubtless in large 

^ Animal Colouration, p. 125, A book full of valuable facts 
and ideas on this most interesting subject. 


Unimportance of Colour 

part due to the fact that many zoologists are 
content to study nature in museums rather 
than in the open. Some of those who observe 
organisms in their natural surroundings, especially 
in such favourable localities as the tropics, 
seem to be of opinion that natural selection 
has but little influence on the colouration of 

Thus D. Dewar writes {Albany Review, 1907) : 
*' Eight years of bird- watching in India have 
convinced me that, so far as the struggle for 
existence is concerned, it matters not to a bird 
whether it be conspicuously or inconspicuously 
coloured, that it is not the necessity for pro- 
tection against raptorial foes which determines 
the colouring of a species ; in short, that the 
theory of protective colouration has but little 
application to the fowls of the air." 

Similarly, F. C. Selous writes, on page 13 
of African Nature Notes and Reminiscences : 
*' Having spent many years of my life in the 
constant pursuit of African game, I have cer- 
tainly been afforded opportunities such as have 
been enjoyed by but few civilised men of 
becoming intimately acquainted with the habits 
and life-history of many species of animals living 
in that continent, and all that I have learned 
during my long experience as a hunter compels 
me to doubt the correctness of the now very 
generally accepted theories that all the wonder- 


The Making of Species 

fully diversified colours of animals — the stripes 
of the zebra, the blotched coat of the giraffe, the 
spots of the bushbuck, the white face and the 
rump of the bontebok, to mention only a few — 
have been coloured either as means of pro- 
tection from enemies or for the purpose of 
mutual recognition by animals of the same 
species in times of sudden alarm." 

So also G. A. B. Dewar — a very close 
observer of nature in England — writes, in The 
Faery Year\ ** Few theories in natural history 
have received more attention of late years than 
protective or aggressive colour, 'mimicry,' and 
harmony with environment. . . . To doubt this 
use of colour to animals seems like inviting back 
chaos in place of cosmos — for abandon the theory, 
and a world of colour is straightway void of pur- 
pose, a muddle of chance. So we all like the 
theory. Some, however, perceive plans to aid 
the wearer in every colour, tint, shade, and 
pattern. We may be sceptical of a good many 
of the cases they cite in support of colour aid, 
though attracted by the main idea." 

Writing of the commoner British butterflies, 
he says : ** After a little practice, any man 
furnished with good eyesight can easily dis- 
tinguish these butterflies — blues, coppers, small 
heaths, and meadow browns — from their perches ; 
and so we may be sure that the small beast, bird, 
or insect of prey, with sense of colour or form, 


Gadow on Coral Snakes < 

could also distinguish them. . . . Quite often, 
without even searching for them, I can see 
cabbage whites and other butterflies asleep on 
perches to which they by no means assimilate." - .-^s; h 
Mr G. A. B. Dewar suggests that the safety of ^ ^ " - 
the resting butterfly lies in '' the position, the 
couch on high, . . . not the mask of colour or 

Two short visits to Southern Mexico sufficed 
to show Dr Hans Gadow that some of the com- 
monly accepted explanations of colour phenomena 
are not the correct ones. 

Thus writing of coral snakes, he says, on 
page 95 of Through Southern Mexico: "They 
are usually paraded as glaring instances of 
warning colouration, but I am not at all sure 
whether this is justifiable. Certainly these Elaps 
are most conspicuous and beautiful objects. 
Black and carmine or coral red, in alternate 
rings, are the favourite pattern ; sometimes with 
narrow golden-yellow rings between them, as 
if to enhance the beautiful combination. But 
these snakes are inclined to be nocturnal in their 
habits, and, except when basking, spend most 
of their time under rotten stumps, in mouldy 
ground, or in ants' nests in search of their prey, 
which must be very small, to judge from the 
size of the mouth." 

Dr Gadow goes on to show that although 
black and red are very strong contrasts in the 


The Making of Species 

day-time, the combination ceases to be effective 
in the dark. He suggests that red and black is 
a self-effacing rather than a warning pattern. 
He further points out that several kinds of harm- 
less snakes have the same colouring and pattern. 
"There seems," he says, "to be no reason why 
we should not call these cases of mimicry ; and 
yet this is most likely a wrong interpretation, 
since such harmless snakes are also found in 
districts where the Elaps does not occur, not only 
in Mexico, but likewise in far-distant parts of 
the world, where neither elapines nor any other 
similarly coloured poisonous snakes exist. To 
interpret this as an instance of ' warning 
colours ' in a perfectly harmless snake, which 
has no chance of mimicry, amounts in such 
cases to nonsense, and we have to look for a 
different explanation upon physiological and 
other grounds." 

It is, to say the least of it, significant that all 
the opposition to the theory of protective coloura- 
tion comes from those who observe nature first 
hand, while the warmest supporters of the theory 
are cabinet naturalists and museum zoologists. 

In the case of nocturnal creatures, as Dr H. 
Robinson very sagely points out {Knowledgey 
January 1909), the value for protective purposes 
of any given colouration must depend very 
largely on the state of the moon. "It was," he 
writes, ** a common experience in the South 


F. C. Selous Quoted 

African War that on overcast or moonless nights 
the nearly black army great-coat made a picquet 
sentry invisible at a distance of a few feet. In 
strong moonlight this garb could be seen at a 
great distance, whereas a khaki pea jacket, use- 
less on a dark night, answered the requirements 
of invisibility very well." It is thus evident ; 
that the dark colour of the buffalo and sable 
antelope cannot be protective on both dark and 
moonlight nights. 

The theory of protective colouration is based 
on the tacit assumption that beasts of prey rely 
on eyesight for finding their quarry. Raptorial 
birds certainly do use their eyes as the means of 
discovering their victims ; but the great majority 
of predaceous mammals trust almost entirely to 
their power of smell as a means for tracking 
down their prey. 

'* Nothing," writes F. C. Selous, on page 14 of 
African Nature Notes and Reminiscences^ *' is 
more certain than that all carnivorous animals 
hunt almost entirely by scent until they have 
closely approached their quarry, and usually 
by night, when all the animals on which they 
prey must look very much alike as far as colour 
is concerned." 

The herbivora — the quarry for the beast of 
prey — too, have a keen sense of smell, so that 
they trust their noses rather than their eyes for 


The Making of Species 

No observer of nature can have failed to 
remark how the least movement on the part 
of an animal will betray its whereabouts, even 
though in colouring it assimilates very closely 
to the environment. So long as the hare squats 
motionless in the furrow, it may remain un- 
observed, even though the sportsman be search- 
ing for it ; but the least movement on its part at 
once attracts his eye. Thus, in order that pro- 
tective colouration can be of use to its possessor, 
the latter must remain perfectly motionless. But, 
in tropical countries, where flies, gnats, etc., are 
a perfect scourge, no large animal is, when 
awake, motionless for ten seconds at a time. 
The tail is in constant motion, flicking off the 
flies that attempt to settle on the quadruped. 
The ears are used in a similar manner. Thus 
the so-called protective colouring of herbivora 
cannot afford them much protection. It is 
further worthy of note that the brush-like tip 
to the tail of many mammals is not of the same 
colour as the skin or fur. It is very frequently 
black. Thus we have the spectacle of a pro- 
tectively coloured creature continually moving, 
as if to attract attention, almost the only part of 
its body that is not protectively coloured ! 

Many species of birds display what is known 
as seasonal dimorphism, still more display sexual 

Seasonally dimorphic birds very often assume 


Sexual Dimorphism 

a bright livery at the breeding season ; this 
nuptial plumage is by no means invariably con- 
fined to the cock, so that we are brought face to 
face with the fact that some hen birds, that are 
normally inconspicuously coloured, become showy 
and easy to see at the nesting time, that is to say, 
precisely at the season when they would seem to 
be most in need of protection. 

In the great majority of cases of sexual dimor- 
phism among birds the cock is the more showily 
coloured. Now, if it be a matter of life-and- 
death importance to a bird to be protectively 
coloured, we should expect the showily coloured 
cock birds to be far less numerous than the 
dull-plumaged hens, since the former are, ex 
hypothesi, exposed to far greater danger than 
the inconspicuous hens. As a matter of fact, 
cock birds in practically all species appear to be 
at least as numerous as the hens. Nor can it be 
said that this is due to their more secretive 
habits. As a general rule, cock birds show 
themselves as readily as the hens ; indeed, in the 
case of the familiar blackbird, the conspicuous 
cock is less retiring in his habits than the more 
sombre hen. It may, perhaps, be thought that 
the greater danger to which the sitting bird is 
exposed accounts for the fact that hens, not- 
withstanding their protective colouration, are not 
more numerous than the cocks. Unfortunately 
for the supposition, in many sexually dimorphic 


The Making of Species 

hens, as, for example, the paradise fly-catcher 
{Terpsiphone paradisi\ the showy cock shares 
the burden of incubation equally with the hen. 

It frequently happens that allied species of 
birds are found in neighbouring countries. The 
Indian robins, for example, fall into two species. 
The brown-backed robin ( Thamnobia cambayensis) 
occurs north of Bombay, while the black-backed 
species (T, fulicata) is found south of Bombay. 
The hens of these two species are almost indis- 
tinguishable, but the cocks differ, in that one has 
a brown back, while the other's back is glossy 
black. The Wallaceian theory of colouration 
seems quite unable to explain this phenomenon — 
the splitting up of a genus into local species — 
which is continually met with in nature. Equally 
inimical to the theory of protective colouration is 
the existence, side by side, of species which 
obtain their living in much the same manner. 
On every Indian lake three different species of 
kingfisher pursue their profession cheek by 
jowl ; one of these — Ceryle rudis — is speckled 
black and white, like a Hamburg fowl ; the 
second is the kingfisher we know in England ; 
and the third is the magnificent white-breasted 
species — Halcyon smyrnensis — a bright-blue bird 
with a reddish head and a white wing bar. It is 
obvious that all three of these diversely plumaged 
species cannot be protectively coloured. It may 
perhaps be objected that the piscatorial methods 


Precis Artexia 

of these kingfishers differ in detail. We admit 
that this is the case, but would maintain, at the 
same time, that these comparatively slight dif- 
ferences in habit do not account for the very 
striking differences in plumage. We may also 
cite the yellow and pied wagtails of our own 
country, which may be seen feeding in the same 
meadows. Most familiar and striking of all is the 
everyday sight of a blackbird and thrush plying 
their respective avocations within a few yards of 
each other on the same lawn, differently coloured 
though they be. 

Another weighty objection to the generally 
accepted theory of protective colouration is that 
some of the creatures which assimilate most 
closely to their environment are those which 
appear to be the least in need of such protection. 

The butterfly Precis artexia^ writes F. C. 
Selous, '* is only found in shady forests, is 
seldom seen flying until disturbed, and always 
sits on the ground amongst dead leaves. Though 
handsomely coloured on the upper side, when its 
wings are closed it closely resembles a dead leaf. 
It has a little tail on the lower wing, which looks 
exactly like the stalk of a leaf, and from this tail 
a dark-brown line runs through both wings (which 
on the under side are light brown) to the apex of 
the upper wing. One would naturally be inclined 
to look upon this wonderful resemblance to a 
dead leaf in a butterfly sitting with closed wings 


The Making of Species 

on the ground amongst real dead leaves as a 

remarkable instance of protective form and 

colouration. And of course it may be that this 

is the correct explanation. But what enemy is 

this butterfly protected against? Upon hundreds 

of different occasions I have ridden and walked 

through forests where Precis artexia was 

numerous, and I have caught and preserved 

many specimens of these butterflies, but never 

once did I see a bird attempting to catch one 

of them. Indeed, birds of all kinds were scarce 

\^ *:' in the forests where these insects were to be 


^v^^'vic Similarly D. Dewar writes [Albany Review, 

1907) : " If a naturalist be asked to cite a perfect 

^ ^^^ example of protective colouring, he will, as likely as 

not, name the sand grouse {Pteroclurus exustus). 

This species dwells in open, dry, sandy country, 

<,y^ and its dull brownish-buff plumage, with its soft 

dark bars, assimilates so closely to the sandy 

environment as to make the bird, when at rest, 

practically invisible, at any rate to the human 

eye. Unfortunately for the theory, this bird 

stands less in need of protective colouration than 

any other, for it has wonderful powers of flight. 

Even a trained falcon is unable to catch it, 

because it can fly upwards in a straight line as 

though it were ascending an inclined plane, with 

the result that the pursuing hawk is never able 

to get above it to strike." 


Striped Caterpillars 

Lord Avebury, who is a typical Wallaceian, 
points out the connection that exists between 
longitudinal stripes on caterpillars and the habit 
of feeding either on grass or low-growing plants 
among grass. The inference, of course, is that 
birds mistake these caterpillars for leaves, or, at 
any rate, fail to observe them when feeding, not 
only because they are green in colour, but 
because their longitudinal stripes look like the 
parallel veins on the blades of grass. But the 
butterflies of the family Satyridce^ as Beddard 
points out, all possess striped larv^, and these 
feed chiefly by night, when neither their colouring 
nor marking is visible, while during the day 
many of them lie up under stones ; other cater- 
pillars of this family feed inside the stems of 
plants. '' Now," writes Beddard (^Animal Coloura- 
tion^ p. loi), "in these cases the colour obviously 
does not matter : if, therefore, the longitudinal 
striping is kept up by constant selection on 
account of its utility, and has no other significa- 
tion, we might expect that in these two species 
[Hipparckia se^nele and CEnis), and in others with 
similar habits, the cessation of natural selection 
would have permitted the high standard required 
in the other cases to be lowered — perhaps, even, 
as has been suggested in the case of cave animals, 
the colours being useless to their possessors, 
might have disappeared altogether — but they 
have not." 


The Making of Species 

Many exceedingly conspicuous birds — as, for 
example all the crow-tribe, the egrets, the 
kingfishers — flourish in spite of their showy 
plumage. Such creatures, while scarcely consti- 
tuting a valid objection to the theory of pro- 
tective colouration, serve to show that protective 
colouring is not a necessity. An animal other- 
wise able to take care of itself can afford to 
dispense with cryptic colouration. '' An ounce 
of good solid pugnacity is a more effective 
weapon in the struggle for existence than many 
pounds of protective colouration." 

There used to live in the gardens of the Zoo- 
logical Society of London a black cat belonging 
to the manager of one of the restaurants. This 
animal used to catch birds on the lawn. We 
believe that not even Mr Thayer will maintain 
that a black cat is cryptically coloured when 
stalking on a well-watered lawn ! Nevertheless 
the nigritude of that cat did not prevent it 
securing a meal. 

The case of birds' eggs furnish an excellent 
example of the lengths to which Wallace and his 
followers have pushed the theory of protective 

D. Dewar maintains that it is possible to 
divide birds' eggs that are coloured, as opposed 
to those that are white, into two classes — those 
which are protectively coloured and those which 
are not The former class includes all those 


Colours of Eggs 

which are laid in shingle or on the bare ground, 
as, for example, the eggs of the ring-plover and 
the lap- wing. ^ He maintains that the variously- 
coloured and speckled eggs that are laid in cup- 
shaped nests are not protectively coloured at all ; 
he declares that they are usually very conspicuous 
when in the nest, and, moreover, it would be futile 
for them to be cryptically coloured, for a bird or 
lizard that habitually sucks eggs will examine 
carefully the interior of each nest it discovers. 

Needless to say, this view does not appeal to 
the so-called Neo- Darwinians. Wallace writes, 
on page 215 of Darwinism-. *'The beautiful 
blue or greenish eggs of the hedge-sparrow, the 
song-thrush, the blackbird, and the lesser redpole 
seem at first sight especially calculated to attract 
attention, but it is very doubtful whether they 
are really so conspicuous when seen at a little 
distance among their usual surroundings. For 
the nests of these birds are either in evergreen, 
or holly, or ivy, or surrounded by the delicate 
green tints of early spring vegetation, and may 
thus harmonise very well with the colours around 
them. The great majority of the eggs of our 
smaller birds are so spotted or streaked with 
brown or black on variously tinted grounds that, 

1 Even these eggs, closely though they resemble in colouring 
the shingle, etc., on which they are laid, are discovered and 
eaten by gulls, as" Mr A. J. R. Roberts points out in The Bird 


The Making of Species 

when lying In the shadow of the nest and sur- 
rounded by the many colours and tints of bark 
and moss, of purple buds and tender green or 
yellow foliage, with all the complex glittering 
lights and mottled shades produced among these 
by the spring sunshine and sparkling rain-drops, 
they must have quite a different aspect from that 
which they possess when we observe them torn 
from their natural surroundings." 

The obvious comment on this is that it Is very 
fine and poetic English, but it is not science. It 
is futile to deny what should be obvious to every 
field naturalist, namely, that the majority of eggs 
laid In open nests are most conspicuous. 

D. Dewar thus summarises the main facts 
which show that eggs in nests (as opposed to 
those laid on the bare ground) are not pro- 
tectively coloured : — 

'' I. Allied species of birds, even though their 
nesting habits are very different, as a rule lay 
similarly coloured eggs. 

** 2. Eggs laid in domed nests certainly do not 
need protective colouring, yet many of these are 

*' 3. The same Is true of many eggs laid In 
holes in trees or In buildings. 

" 4. The protective resemblances of eggs which 
are laid In the open are apparent to everyone, 
which certainly Is not true of those deposited In 


Colours of Eggs 

** 5. Many birds lay eggs which exhibit very 
great variations. 

**6. Some birds lay eggs of different types, 
and these sometimes differ from one another so 
greatly that it is difficult to believe that they 
could have been laid by the same species." ^ 

7. It not infrequently happens that one species 
lays in the disused nest of another, and the eggs 
of the latter are often very different in colouring 
from those of the former. 

We have up to the present considered the theory 
of general cryptic colouration, which declares that 
the majority of creatures are so coloured as to be 
inconspicuous. We have still to deal with the 
hypothesis of special cryptic colouring. 

Certain animals look, when resting, very like 
an inanimate object, such as a dead leaf or a 
twig. This resemblance is said to be the result 
of natural selection, since it enables its possessors 
to escape destruction ; they are seen, but mis- 
taken for something else. 

The classical examples of this kind of protec- 
tive colouring are furnished by the Kallimas or 
leaf-butterflies, which display an extraordinary 
resemblance to dead leaves. 

Other examples are the stick-insects and the 
lappet moth, which looks like a bunch of dry 
leaves. It is needless to multiply instances. 

^ Journal of the Bombay Natural History Society^ VoL xv. 
1903-4), p. 454- 

o 209 

The Making of Species 

In every work on animal colouration numbers of 
such cases are cited. 

We may grant that in some cases, at any rate, 
the resemblance is of value to its possessor, in 
that it deceives predatory creatures. But it does 
not follow from this that the likeness has origi- 
nated through the action of natural selection. In 
order that there can be selection there must be 
varying degrees of a tolerable resemblance to 
select from. How did the initial similarity 
arise ? This is a matter upon which Wallaceians 
are silent. As Poulton truly says, in discussing 
the degree of protection afforded by such re- 
semblances, we tacitly endow animals with senses 
exactly similar to our own. Are we justified in 
so doing ? Most certainly not in the case of the 
invertebrate animals, especially as regards the 
arthropods, of which the eyes are constructed 
very differently from those of human beings. 

D. Dewar has often seen a toad shoot out 
its tongue and touch a lighted cigarette end, 
apparently mistaking it for an insect. Similarly, 
he has again and again induced a gecko lizard to 
chase and try to swallow a piece of black cotton, 
one end of which was rolled up into a ball. It is 
only necessary to take hold of the unrolled end 
of the cotton and place the rolled-up end a few 
inches from the lizard, and gradually draw it 
away in order to induce the lizard to attempt to 
seize it. 


Eyesight of Birds 

It would therefore seem that all these elaborate 
" protective " devices are unnecessary refinements 
if regarded as a protection against invertebrate, 
reptilian, and amphibian foes. Birds, on the other 
hand, appear to have exceedingly sharp eyesight, 
so that in order to deceive them the resemblance 
requires to be very close. Indeed, as regards 
those birds which systematically hunt for their 
prey among leaves and grass, it seems doubtful 
whether the alleged ''protective" resemblances of 
caterpillars to twigs, etc. , are sufficient to be of much 
use to them. Thus Beddard writes (on page 91 
of Animal Colouration) : ''Judging of birds by 
our own standard — which is the way in which 
nearly all the problems relating to colour have 
been approached — does it seem likely that we 
should fail to see a caterpillar, perhaps as long 
or longer than the arm, of an obviously different 
texture from the branches, and displaying in 
many cases through its semi-transparent skin the 
pulsation of the heart, for which we were par- 
ticularly searching?" 

Now, birds certainly feed very largely on 
caterpillars, while they are but rarely seen to eat 
butterflies. If, therefore, the aim and object of 
these special resemblances is the protection of 
the species, we should expect to see them in a 
nearly perfect state in caterpillars on which 
birds feed very largely, and poorly developed in 
butterflies, which do not appear to be greatly 



The Making of Species 

preyed upon by birds, but have to fear chiefly 
the comparatively dull- eyed lizards and mammals, 
of which the latter hunt mainly by scent. As 
a matter of fact, the most striking cases of 
resemblance to inanimate objects are seen among 
butterflies, which seem to stand least in need of 

We have already cited the case of the butterfly 
Precis artexia. Even more marked does the 
unnecessary elaboration of the likeness seem to 
be in the Kallima butterflies. 

The Theory of Warning Colouration 

All biologists admit that there exist some 
organisms which are not coloured so as to be 
inconspicuous. Indeed, the colouring of certain 
species is such as to render them particularly 
conspicuous. Such species are said to be warn- 
ingly coloured. They are supposed to be 
inedible, or to have powerful stings or other 
weapons of defence, or to resemble in appear- 
ance organisms which are thus protected. In 
the first two cases they are said to be warningly 
coloured, and in the last they are cited as 
examples of protective mimicry. With the 
theory of mimicry we shall deal shortly. We 
must first discuss the hypothesis of warning 

When animals are unpalatable, or when they 
possess a sting or poison-fangs, it is, to use the 


Warning Colouration 

words of Wallace, " important that they should 
not be mistaken for defenceless or eatable species 
of the same class or order, since in that case 
they might suffer injury, or even death, before 
their enemies discovered the danger or the use- 
lessness of the attack. They require some 
signal or danger-flag which shall serve as a 
warning to would-be enemies not to attack them, 
and they have usually obtained this in the form 
of conspicuous or brilliant colouration, very dis- 
tinct from the protective tints of the defenceless 
animals allied to them " {^Darwinism, page 

For examples of so-called warningly coloured 
animals, we may refer the reader to Wallace's 
Darwinism, Poulton's Essays on Evolution, or 
Beddard's Animal Colouration. An instance 
familiar to all is our English ladybird. " Lady- 
birds," says Wallace, " are another uneatable 
group, and their conspicuous and singularly 
spotted bodies serve to distinguish them at a 
glance from all other beetles." 

In order to establish the theory of warning 
colouration, it is necessary to prove that all, or 
the great majority of conspicuously-coloured ^ 

organisms, are either unpalatable or mimic \^. 
unpalatable forms. If this be so, we are able hru^i 
to understand that the possession of gaudy '^JL ''' 0^ 
colouring may be of advantage to the individual. ^" ^ 
But even if this be satisfactorily proved, we ' 


The Making of Species 

must bear in mind that it does not necessarily 
follow that these warning colours can be ac- 
counted for on the theory of natural selection. 
For, in order to explain the existence of any 
organ by the action of natural selection, we must 
be able to demonstrate the utility, not only of 
the perfected organ, but of the organ at its very 
beginning, and at each subsequent stage of 
development. This, as we shall show, is pre- 
cisely what the Neo- Darwinians are unable to 
do. We shall have no difficulty in proving that 
it would be more advantageous even to a highly 
nauseous creature to have remained inconspic- 
uously coloured rather than to have gradually 
become more and more conspicuous. 

In the first place, let us briefly examine the 
evidence on which rests the assertion that all 
gaudily-coloured insects, etc., are unpalatable, or 
possess stings, or mimic forms which are thus 

In England wasps, bees, and ladybirds are 
familiar examples of conspicuous insects. 

The banded black and yellow pattern of the 
common wasp and the humble bee are regarded 
as advertisements or danger signals of the power- 
ful sting. 

The red-coat with its black spots is similarly 
believed to be a warning that the ladybird is not 
fit to be eaten. 

Caterpillars are usually coloured grey or brown, 


Examples of Warning Colouration 

so as to be inconspicuous ; but numerous ex- 
ceptions occur which are brightly coloured, and of 
these individuals many have been experimentally 
proved to be objectionable as food to most insect- 
eating animals, being either protected by an 
unpleasant taste, or covered with hairs or 

Familiar cases are those of the abundant and con- 
spicuous black and yellow mottled caterpillars of 
the European Buff-tip Moth {Pygcera bucephala), 
which are much disliked by birds ; and the 
gaily - coloured Vapourer Moth caterpillar 
(Orgyia anttqua), with its conspicuous tufts of 
hair. Readers will remember that a few years 
back these caterpillars were a perfect plague in 
London, in spite of the abundance of sparrows, 
which feed freely on smooth green and brown 

Oft-cited examples of warning colouration, are 
the three great groups of mainly tropical butter- 
flies — the Heliconidce of America, the Acrceidce 
of Africa, and the Danaince found all over the 
world. In all of these the sexes are alike. 
They are, every one, strikingly coloured, dis- 
playing patterns of black and red, chestnut, 
yellow, or white. In most butterflies the lower 
surface of the wings is of a quiet hue, in order 
to render the organism inconspicuous when at 
rest, but in these warningly coloured groups the 
under surface of the wings is as gaudy as the 


The Making of Species 

upper surface. Their flight is slow. They are 
tough, and exhale a characteristic odour. 

Belt showed that, in Nicaragua, birds, dragon- 
flies, and lizards seem to avoid the Heliconine 
butterflies, as the wings of these last are not 
found lying about in places where insectivorous 
creatures feed, whereas wings of the edible forms 
are to be found. Moreover, a Capuchin monkey, 
kept by Belt, always refused to eat Heliconine 

Finn investigated the palatability of a number 
of Indian insects. He found that most of the 
birds with which he experimented objected to 
the Danaine butterflies ; but they disliked still 
more intensely two butterflies belonging to 
groups not universally protected — a swallow- 
tail {Papilio aristolochicB) and a white {Delias 

Finn further experimented with the tree-shrew 
or Tupaia [Tupaia ellioti), which feeds largely 
on insects. He found that this creature refused 
most emphatically all these warningly-coloured 
butterflies. It would under no circumstances 
eat the Danaince, whereas the birds would do so 
if no more palatable insects were offered to them 
at the time. 

Colonel A. Alcock found that a tame Hima- 
layan bear indignantly refused to eat a locust 
[Aularckes militaris) gaily coloured with black, 
red, and yellow, and exhaling an unpleasant- 


Examples of Warning Colouration 

smelling froth ; but this bear readily devoured 
ordinary brown or green species. 

Among cold-blooded vertebrates the common 
European salamander, with its bright black and 
yellow markings, is a striking example of warning 
colouration ; its skin exudes, on pressure, a very 
poisonous secretion. 

Colonel A. Alcock has described a small 
siluroid sea-fish, brightly banded with black and 
yellow, and armed with poison spines. 

A well-known Indian poisonous snake, the 
banded Krait {Bungarus cceruleus), is conspicu- 
ously barred with wide bands of black and yellow ; 
and in South America there occur numerous 
species of coral snakes, in which red is added 
to these conspicuous colours. 

The only known poisonous lizard — the Helo- 
derm of Mexico — is conspicuously blotched with 
black and salmon-colour. 

Among birds, no instances of warning coloura- 
tion have been recorded, though Professor 
Poulton has suggested that possibly the striking 
and contrasted tints of many tropical species may 
be due to this cause. The suggestion is an in- 
genious one, but is at present totally unsupported 
by evidence. 

The skunks are often cited as an excellent 
example of warning colouration among mammals. 
Skunks are most conspicuously arrayed in black 
and white — the latter above, not below, as is 


The Making of Species 

usual — and have bushy tails, which they carry 
erect. Although less powerful and ferocious 
than other members of the weasel family, to 
which they belong, skunks are notoriously pro- 
tected by their abundant secretion of a very fetid 

For further examples of warning colouration 
we would refer the reader to Beddard's illumin- 
ating book, entitled Animal Colotiration. 

It should be noticed that in all the cases which 
we have cited the colouration is not only con- 
spicuous, but is found in both sexes, whereas in 
many undefended animals the male may be just 
as strikingly coloured, but the female is not. 

We may take it as proved that there is a very 
general relation between gaudy colouring and 
inedibility, or rather unpalatability, among insects. 
It may safely be said that any species of insect 
which lives, either as an adult or as a larva, in the 
open will perish in the struggle for existence if, 
being conspicuously coloured, it is neither in- 
edible nor armed with a weapon such as sting, nor 
provided with a thick cuticle, nor resembles in 
appearance some creature which is protected.^* 

But from this it is not legitimate to conclude, 
as Neo-Darwinians do, that these brilliant colours 
have been slowly brought into being by natural 

Why should any creature, having by the 
"luck" of variation and heredity acquired some 


Warning Colouring a Drawback 

quality — be it strength, pugnacity, sting, or un- 
pleasant taste — which renders it comparatively 
immune from persecution, proceed to advertise 
the fact by assuming a gaudy or striking colour ? 
It would surely be better for such an organism to 
remain inconspicuous. By becoming showy it is 
visible to every young bird who, not having yet 
learned that the creature in question is unfit for 
food, seizes and perhaps kills it. It is true that 
the young bird vows that never again will it 
touch another such organism. But of what avail 
to the dying example of warning colouration is 
the resolution of the young bird ? Moreover, the 
organism in question, by being conspicuous, also 
advertises itself to those few enemies which will 
eat it. There are always, as Professor Poulton 
justly remarks, animals which are enterprising 
enough to take advantage of prey which has 
at least the advantage of being easily seen and 

It is possible to cite cases where animals, not- 
withstanding the fact that they possess natural 
defences, become the prey of others in some 
exceptional cases. 

The salamander can be eaten with comparative 
impunity by the toad, a creature very likely to 
meet with it. 

The toad itself may be eaten ; Finn saw the 
Indian toad {Bufo melanostictus) eat another of 
its own kind. He further observed that the 


The Making of Species 

Indian water-snake {Tropidonotus piscator) and 
the **Crow pheasant" cuckoo (Centropus sinensis)^ 
in the free state, and the Indian Roller (Coraczas 
indica) and the Pied Hornbill [Anthracoceros), in 
captivity, eat the warningly-coloured toad. On 
the other hand, a captive Racket-tailed drongo 
rejected toads when offered to it. The common 
cuckoo is well known to feed on hairy and 
" warningly-coloured " caterpillars. 

Finn has also seen the glossy cuckoo in 
Zanzibar devouring black-and-yellow caterpillars. 
Moreover, in America crows are found to 
select deliberately highly polished and strongly 
flavoured beetles. Yet again, wasps are preyed 
upon by bee-eaters, and also eaten by our 
common toad. In India, Finn found, by many 
experiments, that the common garden lizard, 
or ** bloodsucker" (Calotes versicolor), would 
eat, both in captivity and in freedom, all 
"warningly-coloured" butterflies, not only the 
Danaince, but even Delias eucharis and the pre- 
eminently nauseous Papilio aristolochics. That 
^i. this reptile is a great enemy to butterflies is 
C rendered probable by the frequent occurrence of 

"■> \j^''/</ specimens of these insects with its semicircular 
J^ bites in their wings. 

Further, Finn found that bulbuls, the com- 
monest garden birds in India, ate the DanaincB 
readily in captivity, even when other butterflies 
could be had, which was not the case with most 



^ V 

Conspicuous Animals Attacked 

other birds. Bulbuls did, however, usually 
refuse the Delias and Papilio mentioned above. 

The Skunk is preyed upon in America by the 
Eagle-owl {Bubo virginianus) and the Puma. 

Thus, animals provided with natural defences 
are not immune from attack. 

Hence natural selection cannot have en- 
couraged the survival of individuals which dis- 
played a conspicuous colour, for the sake of 
the *' warning." 

We must not forget that many creatures armed 
with powerful weapons possess the unobtrusive 
drab, brown, or green colouration which is 
associated with concealment from foes. 

There can be little doubt that, but for the fact t^^ ft 

that the hive- bee can inflict a sting more severe ;; a y' -/ 
than that of the wasp, this useful insect would ' if ^ 

have been cited as a case of a protectively ^^ ' 

coloured creature. Notwithstanding its sober 
brown colouring, the hive-bee is recognised and ^ 

avoided.^^ v^^^*^ 

Professor Poulton records that the dull in- 
conspicuous caterpillar of the moth {Mcenia 
typica) is rejected by reptiles. It must be 
admitted, however, that these cases among 
insects are very rare. 

The smooth newt {Molge vulgaris)^ a relation 
of the salamander, is protected by a poisonous (F 

skin ; nevertheless the creature has a dark brown ^ ^ 
back and spends most of its ti me on land. Its \ 


-., ' . . . .o 

The Making of Species 

black-spotted, yellow under-surface may have 
some protective value in the water. Neither 
the pike nor the common European water-tortoise 
will eat this newt. 

Toads are nearly all very inconspicuous ; 
nevertheless they are well protected by the acrid 
secretion from the skin glands ; moreover, they 
are both recognised and avoided by those pre- 
dacious creatures to whom they are distasteful. 
Hawks, although as a rule plainly coloured, are 
certainly recognised by all other birds. It would 
seem, therefore, that " warning colours," like the 
similar striking hues of many domestic animals, 
.are incidental attributes. It has been possible 
(for their owners to develop them, because for the 
most part let alone. 

Eisig, long ago, pointed out that the brightly 

coloured pigment in the skin of these warningly 

coloured insects is in certain cases of an excretory 

nature. Therefore the inference which should be 

drawn is, as Beddard points out on page 173 of 

his Animal Colouration, " that the brilliant 

colours (i.e. the abundant secretion of pigment^ 

have caused the inedibility of the species, rather 

than that the inedibility has necessitated the 

\ production of bright colours as an advertisement ^ 

y In other words, Neo-Darwinians put the cart 

• before the horse ! 

In some cases these brilliantly coloured insects 
may be survivals of an age in which there were 


By pertJiission of Messrs. Htitchimoii &• Co. 
Like most of the group to which it belongs, this honey-eater 
{Tro^idorhyncJnis bot(riiensis)\% a soberly coloured bird, but 
is noisy, active, and aggressive. 

By permission of Messrs. Hutchinson &• Co. 


This " mimicking" oriole (firiohis l'07iri(ensis) is of the same tone of colour 
as its supposed model the Friar-bird of the same island. 

Aposematic Sounds 

no birds. When these came into being and 
began to prey upon insects, the conspicuously- 
coloured species which were not inedible or 
very unpalatable would soon become extinct, 
while those that were inedible would survive as 
warningly-coloured insects. In other cases it is 
not improbable that these warningly-coloured 
creatures have arisen by mutations from more 
soberly - hued insects. It is conceivable that 
every now and again a mutation occurs which 
renders its possessor conspicuous. This will 
result in the early destruction of these aberrant 
individuals unless their newly-acquired gaudi- 
ness is either correlated with, or the result of, 

In the case of warning colouration, the Neo- 
Darwinians have, as usual, pursued their theory 
to absurd lengths. Professor Poulton, for 
example, extends it to sounds and attitudes. 
"Sound," he writes, on page 324 of Essays on 
Evolution, " may be employed as an Aposematic 
character, as in the hiss of some snakes and some 
lizards. Certain poisonous snakes when dis- 
turbed produce by an entirely different method 
a far-reaching sound not unlike the hiss. 
Thus the rattle-snake (Crotalus) of America 
rapidly vibrates the series of dry, horny, cuticular 
cells, movably articulated to each other and to 
the end of the tail. The stage through which 
the character probably arose is witnessed in 


The Making of Species 

another genus which vibrates its tail among dry 
leaves, and thus produces a warning sound. 
The deadly little Indian snake {Echis carinatd) 
('the Kuppa') makes a penetrating swishing sound 
by writhing the coils of its body one over the 
other. Special rows of the lateral scales are 
provided with serrated keels which cause the 
sound when they are rubbed against each other. 
Large birds, when attacked, often adopt a 
threatening attitude, accompanied by an intimi- 
dating sound which usually suggests more or less 
closely the hiss of a serpent, and thus includes an 
element of mimicry. . . . The cobra warns an 
intruder chiefly by attitude and by the broadening 
of its flattened neck, the effect being heightened 
in some species by the 'spectacles.' In such 
cases we often witness a combination of cryptic 
and Aposematic methods, the animal being con- 
cealed until disturbed, when it instantly assumes 
a warning attitude. 

'* The benefit of such intimidating attitudes is 
clear : a venomous snake gains far more advan- 
tage by terrifying than by killing an animal it 
cannot eat. By striking, the serpent temporarily 
loses its poison, and with this a reserve of defence. 
Furthermore, the poison does not cause imme- 
diate death, and the enemy would have time to 
injure or destroy the snake." 

At first sight this reasoning may seem very 
convincing. But consider for a moment the 


Intimidating Attitudes 

process by which the hiss originated and gradu- 
ally increased by natural selection. We must 
suppose that the rattle-snake was formerly 
incapable of making any sound. One day a 
variety appeared in which the skin was slightly 
hardened, so that when the creature moved its 
body rapidly there issued a slight sound. This 
must have caused an enemy to refrain from 
attack ; it thus lived to transmit this peculiarity 
to its offspring, and those which made more noise 
than their ancestors escaped, while those that 
made less succumbed to their enemies. For our- 
selves, we find it quite impossible to believe that 
the rattle was thus gradually evolved by means 
of natural selection. Indeed, we are inclined to 
think that neither the hiss of the cobra nor its 
"intimidating attitude" has any terrifying effect 
on its adversary. In the case of the cobra we 
are able to cite positive evidence that dogs and 
cattle show no alarm at the attitude. 

" Dogs," writes D. Dewar of this display, 
''regard it as a huge joke. Of this I have 
satisfied myself again and again, for when out 
coursing at Muttra we frequently came across 
cobras, which the dogs used invariably to chase, 
and we sometimes had great difficulty in keeping 
the dogs off, since they seemed to be unaware 
that the creature was venomous." 

Colonel Cunningham writes, on page 347 of 
SoTne Indian Friends and Acquaintances : *' Sport- 
p 225 

The Making of Species 

ing dogs are very apt to come to grief where 
cobras abound, as there is something very alluring 
to them in the sight of a large snake when it sits 
up nodding and snarling ; and it is often difficult 
to come up in time to prevent the occurrence of 
irreparable mischief." 

Colonel Cunningham also states that many 
ruminants have a great animosity to snakes, and 
are prone to attack any that they may come 

We may therefore well be sceptical as to the 
value of intimidating attitudes to those creatures 
which are in the habit of striking them. 


In a work of this kind it is neither possible 
nor necessary to consider in great detail the 
mass of evidence which has been advanced in 
favour of the theory of mimetic resemblance. 

Chapters vii. and viii. of Professor Poulton's 
Essays on Evolution contain an up-to-date state- 
ment of the facts in favour of the theory. Pro- 
fessor Poulton believes that in all cases mimetic 
resemblance is the result of the action of natural 

He admits that there is no direct evidence in 

its favour, but asserts that "the facts of the 

cosmos, so far as we know them, are consistent 

with the theory, and none of them inconsistent 

with it" (page 271). 


Theory of Protective Mimicry 

We are not at all sure that no facts are against 
the theory of protective mimicry. We shall 
presently set forth some which to us seem, if not 
actually inconsistent with the theory, at least to 
point to the conclusion that the phenomenon 
may be explained otherwise than as a product of 
natural selection. 

Let us first briefly state the case for the theory 
of protective mimicry. 

1. It is asserted that the mimicking species 
and that which is mimicked are often not nearly 
related. For example, the unpalatable larva of 
the Cinnabar Moth {Euchelia jacobaecB) is said to 
mimic a wasp, because it has black and yellow 
rings round its body. 

** The conclusion which emerges most clearly," 
writes Poulton (p. 232), "is the entire indepen- 
dence of zoological affinity exhibited by these 
resemblances." This is supposed to be proof 
that Darwin was wrong when he asserted that 
the original likeness was due to affinity. Says 
Poulton : '' The preservation of an original like- 
ness due to affinity undoubtedly explains certain 
cases of mimicry, but we cannot appeal to this 
principle in the most remarkable instances." 

2. It is asserted that species which are 
mimicked are invariably either armed with a 
sting, well defended, or unpalatable, so that it 
is against the interest of insectivorous creatures 

to attack them. It is further asserted that the 


The Making of Species 

species imitated are '* even more unpalatable than 
the generality of their order." 

3. It is pointed out that the most distasteful 
groups of butterflies — the DanaidcE, the Acrcsince, 
the Ithomiince^ and the Heliconince — consist of 
large numbers of species which closely resemble 
one another. This is said to be due to Mullerian 
mimicry. Mayer states that in South America 
there are 450 species of inedible IthoTniinc^ which 
display only 15 distinct colours, while the 200 
species of Papilio, which are edible, exhibit 36 
distinct colours. Nevertheless, he says, there is 
no lack of individual variability among the former 
hence their conservatism as regards colour cannot 
be attributed to their having but little tendency 
to vary. 

4. It is asserted that although in many cases 
the mimetic resemblances extend to the minutest 
detail, nevertheless they are not accompanied by 
any changes in the mimetic species except such 
as assist in the production or strengthening of a 
superficial likeness. 

Pictures illustrating such cases of mimicry are 
figured on pp. 241, 247, and 251 of Wallace's 
Darwinism (1890 edition). 

5. It is stated that mimetic resemblance is not 
confined to colour, but extends to pattern, form, 
attitude, and movement ; that deep-seated organs 
are affected when the superficial resemblance is 
intensified, but not otherwise. Poulton cites 


Evidence for the Theory 

Clytus arietis, the *' wasp-beetle," as an example 
of this. 

6. It is asserted that mimetic resemblances are 
produced in the most diverse ways ; that the 
modes whereby the similarity in appearance is 
brought about are varied, but the result is 

" A lepidopterous insect," writes Poulton 
(p. 251), ''requires above all to gain transparent 
wings, and this, in the most striking cases that 
have been studied, is produced by the loose 
attachment of the scales, so that they easily and 
rapidly fall off and leave the wing bare except 
for a marginal line and along the veins {Hemaris^ 

7. It is alleged that the imitator and imitated 
are always found in the same locality. If they 
did not do so no advantage would be derived 
from the resemblance. It is further alleged that 
where the mimicking species is edible it is in- 
variably less abundant where it occurs than the 
species it imitates. 

8. It is pointed out that it sometimes happens 
that where in the mimic the sexes differ in 
appearance, the male copies one species, the 
female quite a different one. This is said to be 
because the deception would be liable to be de- 
tected if the mimicking species became common 
relatively to that which is imitated. " We there- 
fore find that two or more models are mimicked 


The Making of Species 

by the same species " [Essays on Evolution, 

P- 372). 

Occasionally the female mimics two other 
species, i.e. she occurs in two forms, each like 
a different species. 

It sometimes happens that the female alone 
mimics. This is said by Wallace to be due to 
her greater need of protection. When she is 
laden with eggs her flight, is slow, and therefore 
she requires a special degree of protection. 

9. It is said that in some species we find a 
non-mimetic ancestor preserved on islands where 
the struggle for existence is less severe, while 
on the adjacent continent mimicry has been 

10. It is alleged that in the cases where moths 
resemble butterflies the former are either as 
diurnal as the butterflies or are species which 
" readily fly by day when disturbed." 

11. It is asserted that some seasonally di- 
morphic forms are examples of mimicry only in 
one state, in the form that comes into being at 
the time when the struggle for existence is most 
severe ; that is to say, in the dry season, in 
Africa, when insect life is far less abundant than 
in the rainy season. 

In other cases the mimicry of the dry- weather 
form is said to be far more perfect. 

Instances of this phenomenon are set forth in 
Professor Poulton's Essays on Evolution, 


Alternative Theories 

It will be observed that we have quoted very 
largely from Professor Poulton's work. Our 
reason for so doing is that he appears to be the 
most prominent advocate of the theory of protec- 
tive mimicry, and his work, which was published 
in 1908, may be taken as the latest Neo- Dar- 
winian pronouncement on the subject. 

Hence if we can show, as we believe we can, 
that his arguments are not sound, we may take 
it that we have demonstrated that the theory in 
its present form is untenable. 

It is worthy of notice that Professor Poulton 
sets forth three other suggestions which have 
been proposed as substitutes for natural selec- 
tion as an explanation of the phenomena of 

The first is the theory of External Causes, 
namely, that the resemblance is due to some 
external cause, such as food or climate. 

The second is the theory of Internal Causes, 
which states that mimetic resemblance is due to 
internal developmental causes. 

The third is the suggestion that sexual 
selection has caused the origin of these re- 

He then proceeds to demolish these to his 
own satisfaction, and adds triumphantly, *' The 
conclusion appears inevitable that under no 
theory, except natural selection, do the various 
resemblances of animals to their organic and 


The Making of Species 

inorganic environments fall together into a 
natural arrangement and receive a common 
explanation " (p. 228). 

To reasoning of this description there is an 
obvious reply. Even if it be granted that the 
alternatives to the theory of natural selection 
as set forth by Professor Poulton are untenable, 
it does not follow that natural selection affords 
an adequate explanation. If A, B, C and D are 
charged with theft and the prosecutor proves 
that neither A nor B nor C committed the theft, 
this will not suffice to secure the conviction of 
D. It is quite possible that a fifth person, E, may 
be the culprit. 

Much of the popularity of the theory of natural 
selection is due to the fact that biologists have 
not yet been able to discover a substitute for it. 

It seems to us that the proper method of 
making progress in science is not to bolster up 
natural selection by ingenious speculations, but to 
look around for other hitherto undiscovered 

Objections to the Theory that the so- 
called Cases of Mimicry owe their 
Origin to Natural Selection 1 

It is obvious that for one creature to resemble 
another can be of little or no benefit to either 
until the resemblance is tolerably close. It is, 


By permissioti of Messrs. Hutchinson &• Co. 


This very conspicuous black bird {^D icria'us ate7-), ranging from Africa 

to China, is a striking feature of the landscape wherever it occurs. 

By per7nissi07i of Messrs. Hutchinson &• Co. 


The fork of the tail in this bird is unique among cuckoos, but is nevertheless 

much less developed than in the supposed model, and may be an adaptation 

for evolution in flight, as such tails usually appear to be. 

Objections to the Theory 

therefore, insufficient to prove the utility of the 
perfected resemblance. We may readily grant 
this and yet maintain that the origin of the 
resemblance cannot be due to the action of 
natural selection. 

The Drongo-cuckoo {Surniculus lugubris) dis- 
plays so great a likeness to the King Crow 
{Dicrurus ater) that it is frequently held up by 
Neo-Darwinians as an excellent example of 
mimicry among birds. But D. Dewar writes, 
on page 204 of Birds of the Plains : ** I do not 
pretend to know the colour of the last common 
ancestor of all the cuckoos, but I do not believe 
that the colour was black. What then caused 
Surniculus lugubris to become black and assume 
a king-crow-like tail? 

*' A black feather or two, even if coupled with 
some lengthening of the tail, would in no way 
assist the cuckoo in placing its ^g^ in the 
drongo's nest. Suppose an ass were to borrow 
the caudal appendage of the king of the forest, 
pin it on behind him, and then advance among 
his fellows with loud brays, would any donkey of 
average intelligence be misled by the feeble 
attempt at disguise? I think not. Much less 
would a king-crow be deceived by a few black 
feathers in the plumage of a cuckoo. I do not 
believe that natural selection has any direct con- 
nection with the nigritude of the drongo-cuckoo." 

Darwin was fully alive to this difficulty when 


The Making of Species 

he wrote : "As some writers have felt much 
difficulty in understanding how the first step 
in the process of mimicry could have been 
effected through natural selection, it may be 
well to remark that the process probably com- 
menced long ago between forms not widely 
dissimilar in colour" {Descent of Man, loth Ed., 
J^ » p. 324). Such a statement is of course quite 

^inconsistent with the Neo-Darwinian position. 

'* The conclusion which emerges most clearly," 

writes Poulton (Essays on Evolution, p. 232), ''is 

the entire independence of zoological affinity 

exhibited by these resemblances ; and one of the 

rare cases in which Darwin's insight into a bio- 

/v logical problem did not lead him right was when 

\f ^; he suggested that a former closer relationship 

may help us to a general understanding of the 

^ ^^ fv, origin of mimicry. The preservation of an 

^ ^ original likeness due to affinity undoubtedly 

^ \^ explains certain cases of mimicry, but we cannot 

A %!^ appeal to this principle in the most remarkable 


It is unnecessary to labour this point. It is 
surely evident to everyone with average intelli- 
gence that, until the resemblance between two 
forms has advanced a considerable way, the like- 
ness cannot be of utility to either, or at any rate 
of sufficient utility to give its possessor a survival 
advantage in the struggle for existence. Until 
it reaches this stage, natural selection cannot 




The Brain-fever Bird 

operate on it. It is therefore absurd to look upon 
natural selection as the direct cause of the origin 
of the likeness. When once a certain degree of 
resemblance has risen, it is quite likely that in 
some cases natural selection has strengthened! 
the likeness. 

The second great objection to the Neo- 
Darwinian explanation of the phenomenon 
known as mimicry is that in many cases the 
resemblance is unnecessarily exact. Even as 
we saw how the Kallimas, or dead-leaf butter- 
flies, carried their resemblance to dead leaves 
to such an extent as to make it appear probable 
that factors other than natural selection have had 
a share in its production, so do we see in certain 
cases of mimetic resemblance an unnecessarily 
faithful likeness. 

The common Hawk Cuckoo of India (Hiero- 
coccyx varius) furnishes an example of this : 
" The brain-fever bird," writes Finn, on page 58 
of Ornithological and Other Oddities, " is the 
most wonderful feather copy of the Indian 
Sparrow-hawk or Shikra {Astur badius). All the 
markings in the hawk are reproduced in the 
cuckoo, which is also of about the same size, and 
of similar proportions in the matter of tail and 
wing ; and both hawk and cuckoo having a first 
plumage quite different from the one they assume 
when adult, the resemblance extends to that too. 
Moreover, their flight is so much the same that 


The Making of Species 

unless one is near enough to see the beak, or can 
watch the bird settle and note the difference 
between the horizontal pose of the cuckoo and 
the erect bearing of the hawk, it is impossible to 
tell them apart on a casual view." Moreover, 
the tail of the cuckoo sometimes hangs down 
vertically, thus intensifying the likeness to the 

It is quite possible that the brain-fever bird 
derives some benefit from the resemblance ; 
indeed, it has been seen to alarm small birds, 
even as the hawk-like common cuckoo frightens 
its dupes, but, as D. Dewar pointed out, on page 
105 of vol. 57 of the Journal of the Society of 
Arts, '' this is not sufficient to explain a likeness 
which is so faithful as to extend to the marking 
of each individual feather. When a babbler 
espies a hawk-like bird, it does not wait to inspect 
each feather before fleeing in terror ; hence all 
that is necessary to the cuckoo is that it should 
bear a general resemblance to the shikra. The 
fact that the likeness extends to minute details in 
feather marking, points to the fact that in each 
case identical causes have operated to produce 
this type of plumage." This conclusion is still 
further strengthened by the fact that the likeness 
extends to the immature plumage, that is to say, 
exists at a time when it cannot assist the cuckoo 
in its parasitical work. 

Poulton meets this objection as follows : 


By pet mission f Messis. UiUc/nnsou &■ Lo. 


The upper surface of the tail, not shown in this drawing, exactlj- correspond? 

with that of the cuckoo " mimic." 

By ferinisszoii of Messrs. Hutchinson &• Co. 


This species {Hie?-ococcyx va7-ius) is commonly known in India as the 

" Brain-fever bird." 


" All such criticism is founded on our imperfect 
knowledge of the struggle for existence. The 
impressions and judgments of man are immensely- 
influenced by the ' corroborative detail,' giving 
* artistic verisimilitude to a bold and unconvincing 
narrative.' Indeed, the laughter which is in- 
variably raised by this passage from T/ie Mikado 
is, I have always thought, not only or chiefly 
due to the humour of the application, but to the 
way in which a great and familiar truth breaks 
in upon the listener with all the pleasing surprise 
which belongs to epigram. Birds, the chief 
enemies of insects, are known to have powers 
of sight far superior to those of man, and, from 
our experience of them in captivity, it may be 
safely asserted that their attention is attracted by 
excessively minute detail. Until our knowledge 
of the struggle for life is far more extensive than 
at present, the argument founded on Hypertely 
may be left to contend with another argument 
often employed against the explanation of cryptic 
and mimetic resemblance by natural selection. 
Hypertely assumes that there are unnecessary 
details in the resemblance, that the resemblance 
is perfect beyond the requirements of the insect ; 
the second argument maintains that birds are so 
supremely sharp-sighted that no resemblance, 
however perfect, is of any avail against them. 
In the meantime the majority of naturalists will 
probably reject both extremes, and believe that 


The Making of Species 

the enemies are certainly sharp-sighted and 
successful in pursuit, but that perfection in detail 
makes their task a harder one, and gives to the 
individuals possessing it in a higher degree than 
others, increased chances of escape, and of be- 
coming the parents of future generations." 
{Essays on Evolution, p. 302.) 

This long quotation requires careful considera- 
tion, since to us it appears to be typical of the 
kind of reasoning resorted to by Neo-Darwinians. 

Note the reference to our *' imperfect know- 
ledge of the struggle for existence." This is 
almost invariably the last refuge of the Neo- 
Darwinian when worsted in argument. We 
fully admit that there is still much to be learned 
of the nature of the struggle for existence, but 
such a statement sounds very curious when 
uttered to those who pin their faith to the theory 
which sees in the principle of natural selection 
an explanation of all the phenomena of the or- 
ganic world. Natural selection, be it remembered, 
is but a name for the struggle for existence. 

*' Birds," says Professor Poulton, " are the 
chief enemies of insects." This may be so. 
But we greatly doubt whether they are the 
chief enemies of butterflies and moths, among 
which the most perfect examples of mimicry are 
supposed to occur. 

We have watched birds closely for some years, 
but believe that we could almost count on our 


y\^ c if> i i'K-f 

4t A4 t^ ! ., J -^-T.^^j/u' 

Birds capturing Butterflies 

fingers the cases in which we have seen a bird 
chase a butterfly. 

Professor Poulton, being aware of this ob- 
jection, sets forth, on pp. 283-292 of Essays on 
Evolution, the evidence he has gathered in favour 
of the view that birds are the chief enemies of 
butterflies and other lepidoptera. 

As the resuh of five years' observation in S. 
Africa, Mr G. A. K. Marshall was able to record 
some eight cases of birds capturing butterflies. 
In three cases the butterfly seized was warningly 
coloured, or, at any rate, conspicuous ! In two 
of these eight cases the bird failed to capture 
its quarry ! 

Says Mr Marshall, **the fact that birds refrain 
from pursuing butterflies may be due rather to 
the difficulty in catching them than to any wide- 
spread distastefulness on the part of these 

During six years' observation in India and 
Ceylon, Colonel Yerbury records some half 
dozen cases of birds capturing, or attempting to 
capture, insects. He writes : ''In my opinion 
an all-sufficient reason for the rarity of the 
occurrence exists in the fact that in butterflies 
the edible matter is a minimum, while the inedible 
wings, etc., are a maximum." 

Colonel C. T. Bingham in Burma states that 
between 1878 and 1891 he on two occasions 
witnessed the systematic hawking of butterflies 


The Making of Species 

by birds, although he observed on other occasions 
some isolated cases. 

This appears to be the sum total of the 
evidence adduced by Professor Poulton as 
regards the capture of butterflies by birds. 
This seems to us an altogether insufficient 
foundation upon which to build the theory that 
the cases of resemblance between unrelated 
species have been effected by natural selection. 

It is, however, to be noted that probably 
among birds the most dangerous enemies of 
butterflies are not those that habitually catch 
insect prey on the wing. Such are experts in 
the art of fly-catching, and would despise the 
comparatively meatless butterfly. One often 
comes across butterflies with an identical notch 
in each wing, which leaves little room for doubt 
that those particular butterflies had been snapped 
at, while resting, by a bird. Among birds the 
chief enemies of butterflies and moths are pro- 
bably to be found in those that hunt for their 
food in bushes and trees. 

Thus, what we do know of the nature of the 
struggle for existence offers but poor support to 
the Neo-Darwinian explanations of the cases of 
so-called mimicry in nature. 

Professor Poulton's idea of pitting the argu- 
ment of hypertely against that of the alleged 
supreme sharp-sightedness of birds is ingenious, 
but is not likely to satisfy very many people save 


Observing-powers of Birds 

those content to live in a fools' paradise. If 
birds are supremely sharp-sighted, and pay- 
attention to excessively minute detail, the diffi- 
culty of accounting for the origin of protective 
mimicry on the natural selection hypothesis 
becomes all the greater. 

The question whether or not birds are good 
observers is a most interesting one. Unfor- 
tunately, hitherto, but little attention has been 
paid to the subject. The evidence available 
seems to point to the fact that birds, like savages, 
have sharp eyes only for certain objects — that is 
to say, for the things they are accustomed to 
look out for. All observers of nature must have 
noticed how quick a butcher-bird is to catch sight 
of a tiny insect upon the ground at a distance of 
some yards from his perch. 

On the other hand, it is said that when there 
is snow upon the ground wood pigeons will 
approach quite close to a man wearing white 
clothes and a white hat, provided he keep 
perfectly still. Finn once witnessed in Calcutta a 
sparrow pick up a very young toad, obviously by 
mistake, for it dropped it at once with evident 
distaste. Birds of prey are supposed to have 
remarkably good eyesight ; yet they can readily 
be caught by a net stretched out before their 
quarry. They are not trained to be on the 
watch for such things as nets, and so do not 
appear to notice one when erected. 

Q 241 

The Making of Species 

It is thus our belief that the very perfection 
and detail of some so-called mimetic resemblances 
are a very serious objection to the theory of 
protective mimicry as enunciated by Professor 
Poulton and other Neo- Darwinians. 

There is yet a further objection to this theory, 
one which, in our opinion, is fatal to the hypo- 
thesis in its generally accepted form. 

A number of cases occur where two species, in 
no way related, show close resemblance to one 
another under such circumstances that neither 
can possibly derive any benefit from the likeness. 
The theory of protective mimicry is quite unable 
to explain these cases. This fact leads to a 
suspicion that, in the instances where the theory 
does at first sight appear to offer an explanation, 
the resemblance may also be due to mere 

We may perhaps call the cases which the 
theory of mimicry is unable to account for '* false 
mimicry," but in so doing we must bear in mind 
the possibility that some, at any rate, of the 
examples of so-called mimicry may, on further 
investigation, prove to be nothing of the kind. 

''False" Mimicry among Mammals 

The Cacomistle of Mexico (Bassaris astuta), 

one of the raccoon family, has a grey body and 

long black-and-white ringed tail, just like the 

ring-tailed Lemur of Madagascar [Lemur catta) ; 



False Batesian Mimicry 

both are arboreal and about the same size, and 
this lemur's colouration is exceptional in its 

The banded Duiker-buck of West Africa 
{Cephalophus doriae), has the same very unusual 
colouration as the thylacine or marsupial wolf of 
Tasmania, light brown, with bold black bands 
across the hinder part of the back, and the 
animals are about the same size. 

The dormouse of Europe closely resembles a 
small American Opossum [Didelphys murina), 
and a larger opossum {D. crassicaudata) is very 
like the Siberian Mink [Mustela sibiricd). 

The Flying Squirrel of North America (^a^rd?/- 
terus volucelld) is closely copied by the Flying 
Phalanger (Petaurus breviceps) of Australia. 

It will be readily seen that in no one of these 
cases can the likeness be of utility to either the 
** model " or the ** copy." 

False Batesian Mimicry among Birds 
There are many instances of this phenomenon 
among birds. The New Zealand Cuckoo ( Uro- 
dynamis tritensis) shows a far closer resemblance 
to the American Sparrow-hawk [Acczpiter cooperi) 
than to any New Zealand hawk, and in fact 
closely mimics this quite alien bird. 

The stormy petrel, a purely oceanic bird, 
closely resembles in size, colour, and style of 
flight the Indian Swift (Cypselus affinis), a purely 


The Making of Species 

inland creature ; both are sooty black, with a 
conspicuous white patch on the lower back. 

The Pied Babbling Thrush (Crateropus bicolor) 
of Africa is singularly Hke the Pied Myna((9r^^- 
lipica melanopterd) of Java, both being of about 
the same size, with white body and black wings 
and tail quills. This, we may add, is a very 
unusual colouration among small birds. 

The black -headed Oriole [Oriolus melano- 
cephalus) of India is very similar in appearance 
to the common Troupial {Icterus vulgaris) of 
Brazil ; indeed, the troupials, a purely American 
group, are so like the old world orioles in colour 
that they usurp their name in America. 

The little insectivorous lora {/Egitkina tiphia) 
of India strongly resembles in size and colour 
a Siskin {Chrysomitris colambiana) from South 
America, the males in both being black above 
and yellow below, while in the females the black 
is replaced by olive-green. 

Another Indian babbler [Cepkalopyrus flam- 
miceps)y yellowish-green, with orange forehead, is 
closely copied by, or copies, the well - known 
Brazilian Saffron-finch [Sy calls flaveo let). 

In Fergusson Island, near New Guinea, there 
is a ground pigeon (Otidiphaps insularls) which 
is black with chestnut wings, like several of the 
powerful ground cuckoos of the genus Centropus, 
but no species of these cuckoos so coloured 
appears to inhabit the island. 


False Batesian Mimicry 

In Africa there is a tit {Parus leucopterus) 
which has the same very unusual colouration as 
an East- Indian bulbul [Mzcropus melanoleucus), 
both being black with a white patch on the wing- 
coverts. These two birds are about the same 
size. As showing the purely coincidental char- 
acter of such resemblances, we may mention that 
this same rare pattern occurs again in our Black 
GmW^mot [Uria gry lie) and in the Muscovy Duck 
(Cairina moschata). 

We have already quoted Gadow (p. 198) on 
"false mimicry" among snakes. He also gives, 
on p. 1 10 of Through Southern Mexico^ an example 
of this phenomenon among amphibia. It is, he 
writes, " impossible to distinguish certain green 
tree-frogs of the African genus Rappia from a 
Hyla, unless we cut them open. If they lived 
side by side, which they do not, this close resem- 
blance would be extolled as an example of 

We should be very greatly surprised if abun- 
dant examples of ''false mimicry" are not found 
among insects. We trust that this remark will 
stimulate some entomologist to pay attention to 
the subject. 

It is the essence of Mullerian mimicry that 
both model and copy are immune from attack 
from enemies. Unfortunately for the theory, 
similar resemblances occur among birds of prey, 


The Making of Species 

where neither party can benefit from the associa- 
tion. This gives rise to what we may perhaps 
call false Mullerian mimicry. Thus the goshawk 
and peregrine falcon resemble each other in 
being brown above and streaked below in im- 
mature plumage, and having barred underparts 
and a grey upper plumage when adult. 

Having stated the more important objections 
to the theory of protective mimicry, it now 
remains for us to deal specifically with each head 
of evidence offered in its favour. 

1 . With regard to the assertion that the model 
and its copy are often not nearly related, we have 
shown that among mammals and birds instances 
of resemblance between widely-separated groups 
occur under such circumstances that neither party 
can derive any benefit therefrom. 

2. As regards the assertion that species which 
are mimicked are either well-defended or un- 
palatable, this certainly does not hold good with 
regard to some at any rate of the coincidental 
resemblances among birds which we have 
pointed out ; even if these pairs of similar 
species lived in the same country it would re- 
quire considerable ingenuity to say why one 
should mimic the other. 

3. As regards the argument that the inedible 
species of Tthomiince, etc., display only fifteen 
colours, while the less numerous edible Papilios 


Theory of Mimicry Criticised 

display more than double this number of colours, 
we may draw attention to the fact that those 
birds which are most immune from attack are 
precisely those which display the smallest range 
as regards colour, e,g., hawks, owls, crows, gulls, 
storks, and cranes. As we have already sub- 
mitted, no question of Miillerian association 
comes in here. 

On the other hand, the eminently edible 
families of game-birds and ducks display great 
variety of colour, in the males at all events. 

4. As regards the statement that although 
in many cases the mimetic resemblances extend 
to the minutest detail, they are not accompanied 
by any structural changes except such as assist 
in the production of a superficial likeness, we may 
refer to the case we have already cited of the 
New Zealand cuckoo, which, though it so closely 
copies an American hawk, is typically cuculine in 
structure. Here, of course, there can be no 
question of advantage to the ** mimicking " 
cuckoo in the resemblances. 

5. In answer to the argument that mimetic 
resemblance extends to form, attitude, and move- 
ment, as well as colour, and that deep-seated 
organs are affected only when the superficial 
resemblance is thereby intensified, we may draw 
attention to such cases as the following : — 

(ct) The harmless Indian ^ndk^^i^Lycodon aulicus) 
is closely similar to the well-known Krait {Bun- 


The Making of Species 

garus cceruleus), also Indian ; but the resemblance 
extends to a structural detail which can hardly 
have mimetic value — namely, the harmless snake 
has long, fang-like front teeth, though these are 
unconnected with poison-glands. Animals which 
come into contact with the krait and its mimic 
are hardly likely to inspect their teeth. 

{b) A considerable number of birds of the 
shrike group — known as Cuckoo-Shrikes {Cam- 
pophaga) — closely resemble cuckoos in plum- 
age ; but even if they derive any benefit from 
mimicking birds which are credited with being 
mimics already, they cannot profit by the fact 
that the shafts of the rump-feathers in both groups 
are stiffened ; this being a peculiarity which would 
not be perceptible until the bird was in the grasp 
of an aggressor. 

{c) As a third case of coincidence we may 
refer to the tubercle in the nostril of the Brain- 
fever-bird [Hierococcyx varius), as a minute detail 
of hawk-like appearance, though not present in 
the particular species imitated. 

6. The argument that mimetic resemblances 
are producd in the most diverse ways, but the 
result is uniform, loses much of its force when 
we consider the various methods by which 
short-tailed birds appear to have long caudal 

In the peacock it is the upper tail coverts 
which are elongated ; in the Stanley Crane 


Theory of Mimicry Criticised 

(Tetrapteryx paradised) it is the innermost or 
tertiary quills of wing ; in one of the egrets 
some of the feathers of the upper back grow 
to a ereat length and form a train ; in the Bird 
of Paradise {Paradisea apodd) the long flank 
plumes are commonly mistaken for the tail. 

In these cases there can be no question of 

7. We have shown that the idea that imitator 
and imitated are always found in the same area 
is absolutely fallacious. In birds, for example, 
the most striking resemblances appear to occur 
between species that dwell far apart. 

8. We can cite, as parallel to the case of a 
mimicking species of which the male copies one 
model and the female another, the strange 
similarity between the barred brown plumage 
of the female blackcock and that of the female 
eider-duck. The males of these species, although 
both black and white, differ greatly in appear- 
ance ; but the male blackcock is admittedly very 
like the male of another species of sea-duck — the 

9. Against the supposed ancestral non- 
mimetic forms existing on islands we can pit 
the ** mimetic " orioles in small islands and their 
non-mimetic cousins on the mainland. In 
Australia an oriole of what appears to be an 
ancestral style lives beside, but declines to 
mimic, a friar bird of a very pronounced type. 


The Making of Species 

10. The case of certain diurnal moths mimick- 
ing butterflies appears to be explicable without 
the aid of the theory of protective mimicry. 
When two species adopt the same method of 
obtaining food, it not infrequently happens that 
a professional likeness springs up between them. 
Of this the swifts and swallows afford a striking 

11. As a set-off to the cases where the alleged 
mimicry is confined to certain seasons of the year, 
we may cite the case of the pheasant-tailed 
Jagana [Hydrophasianus chirurgus), which in its 
winter plumage might easily be mistaken, when 
on the wing, for the paddy bird or Pond Heron 
[Ardeola gray it), both being of like size and 
having a brown back, long green legs, and white 
wings. Moreover, they are to be found in 
the same localities in India. At the breeding 
season, however, they are absolutely different 
in plumage. 

Yet another argument commonly adduced in 
favour of the theory of protective mimicry is that 
local variations of the imitated species are some- 
times followed by the imitator ; thus the butterfly 
Danais chrysippus shows a white patch on the 
hind wings in Africa, and this is followed by 
its mimic. 

But the same thing occurs, quite irrationally, 
so to speak, among birds. The peregrine falcon 
and hobby of Europe are only winter migrants 


Recognition Colours 

to India, where they are replaced as residents by 
the Shaheen [Falco peregrinator) and Indian 
Hobby {F. severus). Both these differ from the 
migratory forms by being blacker above and 
chestnut below, instead of cream colour. Thus 
the resemblance occurs in each race. A similar 
distinction, as noted by Blyth, exists between 
the Common Swallow [Hirundo rustica) and the 
Swallow {^H. tytleri) of Eastern Asia, the latter 
having the whole ventral surface rufous instead 
of only the throat. Yet no one will suggest that 
swallows mimic falcons, or that there is mimicry 
between the peregrine and hobby. It is obvious 
that such parallel changes occur independently 
of mimicry. 

The Water-rail {Rallus aquaticus) and Baillon's 
Crake {Porzana bailloni) of Europe are distin- 
guished from their allies of Eastern Asia by 
having the sides of the head plain grey, whereas 
the Eastern Asiatic forms {R, indicus and P, 
pusilla) have a brown streak along each side of 
the face. Here, again, we have an instance of 
birds of the same family varying together with 
geographical distribution. 

'* Recognition " Colours 

One of the prettiest conceits of the Wallaceian 
school of zoologists is the theory of recognition 

" If," writes Wallace, on page 2 1 7 of Darwinism, 


The Making of Species 

** we consider the habits and life-histories of those 
animals which are more or less gregarious, com- 
prising a large proportion of the herbivora, some 
carnivora, and a considerable number of all orders 
of birds, we shall see that a means of ready 
recognition of its own kind, at a distance or 
during rapid motion, in the dusk of twilight 
or in partial cover, must be of the greatest 
advantage and often lead to the preservation of 
life. Animals of this kind will not usually 
receive a stranger in their midst. While they 
keep together they are generally safe from 
attack, but a solitary straggler becomes an easy 
prey to the enemy ; it is therefore of the highest 
importance that, in such a case, the wanderer 
should have every facility for discovering its 
companions with certainty at any distance within 
the range of vision. 

*' Some means of easy recognition must be of 
vital importance to the young and inexperienced 
of each flock, and it also enables the sexes to 
recognise their kind and thus avoid the evils 
of infertile crosses ; and I am inclined to believe 
that its necessity has had a more widespread 
influence in determining the diversities of animal 
colouration than any other cause whatever. To 
it may probably be imputed the singular fact that 
whereas bilateral symmetry of colouration is very 
frequently lost among domesticated animals, it 
almost universally prevails in a state of nature ; 


Recognition Colours 

for if the two sides of an animal were unlike, 
and the diversity of colouration among domestic 
animals occurred in a wild state, easy recognition 
would be impossible among numerous closely 
allied forms." 

As examples of recognition colouration, Wallace 
cites, among others, the white upturned tail of the 
rabbit — a " signal flag of danger," the conspicuous 
white patch displayed by many antelopes, the 
white marks on the wing- and tail-feathers of the 
British species of butcher-birds, the stone-chat, 
the whin-chat, and the wheat-ear. 

Wallace therefore asserts, firstly, that recog- 
nition marks not only help herbivorous animals 
to keep together, but act as a danger signal ; the 
member of a flock which first catches sight of the 
enemy takes to its heels, displaying its white 
flag, which is the signal of danger to the other 
members of the flock. Secondly, that recog- 
nition marks prevent the evils of infertile crosses. 
Thirdly, that the necessity of being able to recog- 
nise one another has rigidly preserved bilateral 
symmetry among animals in a state of nature. 

As regards assertion number one, we would 
point out that where a flock of herbivora is being 
stalked by a beast of prey, the member of the 
flock nearest to the enemy — that is to say, the 
hindmost member — will probably be the first to 
observe him. As that creature will be more 
unfavourably situated for escape than the rest of 


The Making of Species 

the herd, it will not be to their advantage to 
follow the line it has taken. Moreover, being at 
the rear of the flock, it is not in a good position 
to take the lead, and its pursuer is likely to see 
the danger signal before its friends do. It would 
thus seem that "danger signals," while possibly 
sometimes of service to their possessors, are on 
the whole ornaments which might profitably be 
dispensed with. Natural selection can scarcely 
be charged with the production of a character of 
such doubtful utility to the organism. 

Moreover, flourishing species of many 
gregarious animals do not possess any " signal 
flag of danger," while, on the other hand, a great 
many solitary species display markings that 
render them very conspicuous when in motion. 
Take the case of the famous Indian Paddy Bird 
(Ardeola g7^ayii). This, when at rest, is coloured 
so as to be very difficult to distinguish from its 
surroundings, but flight transforms it, for it then 
displays its milk-white pinions, which would 
make a perfect danger signal, if only it were not 
peculiarly solitary in its habits. Its gregarious 
brethren, the Cattle Egrets {Bubulcus coromandus), 
on the other hand, display no danger signal. 

That these recognition marks prevent the 
intercrossing of allied species and the production 
of infertile hybrids appears to be pure fiction. 
As we have already shown, hybrids between 
allied species are by no means always infertile. 


Interbreeding of Allied Species 

Moreover, species which differ only in colour 
seem usually to interbreed in those parts where 
they meet. 

"This interbreeding," writes Finn, on page 14 of 
Ornithological and Other Oddities, '' occurs where 
the carrion crow (Corvus corone) meets the hooded 
crow [Corvus comix), where the European and 
Himalayan goldfinches {Carduelis carduelis and 
C. caniceps) encounter each other, and where the 
blue rollers of India and Burma {Coracias indicus 
and C. affinis) come into contact, to say nothing 
of other cases." 

Of these other cases, the Indian bulbuls of the 
genus Molpastes form a very remarkable one. 
In all places where two of the so-called species 
meet they appear to interbreed, and so freely do 
they interbreed that at the points where the allied 
species run into one another it is not possible to 
refer the bulbuls to either species. Thus William 
Jesse writes of the Madras Red-vented Bulbul 
{Molpastes hcemorrhous) (page 487 of The Ibis 
for July 1902): ''This bird, although I have 
given it the above designation, is not the true 
M. hcemorrhous. I have examined numbers of 
skins and taken nests and eggs time after time, 
and have come to the conclusion that our type is 
very constant, and at the same time differs from 
all the red-vented bulbuls hitherto described. 
The dimensions tally with those given by Oates 
for M. hcemorrhouSy while the black of the crown 


The Making of Species 

terminates rather abruptly on the hind neck, and 
is not extended along the back, as is the case 
with M. interntedius and M. bengalensis. On the 
other hand, as in the two last species, the ear 
coverts are chocolate. Furthermore, I may add 
— although I attach little importance to this — 
that the eggs of the Lucknow bird which I have 
seen are, without exception, far smaller than my 
eggs of genuine M. interntedius from the Punjab. 
My own opinion is that the Lucknow race is the 
result of a hybridisation between the other three 

Further, in Bannu, Mr D. Donald saw M. 
interntedius and M. leucogenys paired at the same 
nest. That gentleman could not possibly be 
mistaken on the point, as the latter species has 
white cheeks and yellow under tail-coverts, while 
the cheeks of the former species are dark-coloured 
and the patch of feathers under the tail is red. 
Similarly, Whitehead and Magrath, writing of 
the birds of the Kurram Valley (Ibis, January 
1909), record that the former shot no fewer than 
twelve bulbuls, which undoubtedly appear to be 
hybrids between these two species. As these 
hybrids differ considerably inter se, there seems 
no room for doubt that they breed with one 
another and with the parent species. 

Wallace's third statement, that if the two sides 
of animals in a state of nature were alike, easy 
recognition would be impossible among numerous 


Symmetry in Nature 

closely allied forms, reminds us forcibly of the 
sad case of the boy whose tailor was his mother. 
Humanum est errare : she made her son one 
pair of trousers that fastened up behind, so that 
the poor boy when wearing them never knew 
whether he was going to or coming home from 
school ! If animals are able to recognise their 
mates, their bilateral symmetry does not seem 
necessary to enable them to distinguish their 
fellows from allied species. 

It is, indeed, true that asymmetrically marked 
animals are very rarely seen in the wild state, 
while they are the rule rather than the exception 
among domesticated species. But this appears 
to be due, not to the necessity of recognition 
markings in nature, but to the fact that those 
animals that display a tendency to massed pig- 
ment perish in the struggle for existence, since 
this massing of pigment appears to be correlated 
with weakness of constitution. In other words, 
this massing of pigment is an unfavourable varia- 
tion, which under natural conditions dooms its 
possessor. In the easier circumstances of domes- 
tication, animals which are irregularly pigmented 
are able to survive, so that, among them, the 
almost universal tendency to the massing of pig- 
ment can be followed without let or hindrance. 

It is unnecessary to say more upon this subject. 
The few facts we have set forth suffice to destroy 
thisparticular excrescence on the Darwinian theory. 

R 257 

The Making of Species 

The Colouring of Flowers and Fruits 

Extremely interesting though the subject be, 
we are unable to consider at length the generally- 
accepted theory that the colour markings and 
perfumes of wild flowers are the result of the 
unconscious selection exercised by insects. 

While not denying that many flowers profit by 
their colouring, that these colours may sometimes 
serve to attract the insects, by means of which 
cross-fertilisation is effected, we are not prepared 
to go to the length of admitting that all the 
colours, etc., displayed by flowers and floral 
structures are due to the unconscious selection 
exercised by insects. It is one thing to admit 
that the colour of its flowers is of direct utility to 
a plant ; it is quite another to assert that the 
colour in question owes its origin and develop- 
ment to natural selection. Our attitude towards 
the generally accepted explanation of the colours 
of flowers is similar to that which we adopt 
towards the theory of protective mimicry among 
animals. In certain cases we are prepared to 
admit that the mimicking organism derives benefit 
from the likeness ; but this, we assert, is no proof 
that natural selection has originated the likeness. 

The theory that flowers have developed their 
colours in order to attract insects to them, and 
thus secure cross-fertilisation, is based on the 


Cross- versus Self-fertilisation 

assumption that cross - fertilisation is advan- 
tageous to plants. It is questionable whether 
this assumption is justified. True it is that 
numbers of experiments have been performed, 
which show that, in many cases, flowers which are 
artificially self-fertilised yield comparatively few 
seeds. But experiments of this kind do not 
prove very much. 

To place on the stigma pollen from the anthers 
of the same flower, in case of a plant which for 
many generations has been cross-fertilised, is to 
subject the plant in question to a novel experi- 
ence — an experience which may be compared to 
transplanting it to another soil. The immediate 
effect may appear to be unfavourable, although, 
if the experiment be persisted in, the ultimate 
results may prove beneficial to the plant. 

That this is the case with some flowers that 
are artificially fertilised is asserted by the Rev. 
G. Henslow. This observer states, that had 
Darwin pursued his investigations further, he 
would probably have modified his views regard- 
ing the benefits of self-fertilisation. Darwins 
statement that '' Nature abhors perpetual self- 
fertilisation " seems to be as far from the 
truth as that which declares " Nature abhors a 

From the mere fact that cross-fertilised flowers 
yield a greater quantity of seed than they do 
when self-fertilised, it does not necessarily follow 


The Making of Species 

that cross - fertilisation is advantageous. The 
amount of seed produced is probably not always 
a criterion as to the advantages of the crossing 
to the plant. Some flowers yield most seed 
when fertilised by the pollen from flowers 
belonging to a different species ! 

It is significant that some plants produce 
cleistogamous flowers, that is to say, flowers 
which invariably fertilise themselves. Such 
flowers never open ; so that the visits of insects 
^v>. . are precluded. 
^^-J^^ Vf[ According to Bentham, the Pansy [Viola tri- 
s^ ^ rf \\color) is the only British species of Viola in 
^ ^"^^^^ c I i which the showy flowers produce seeds. The 
a^"^ :^ . V' i other species are all propagated by their cleisto- 
gamous flowers. The genus Viola is an ad- 
^^ V' vanced species : it would therefore seem that 

the production of cleistogamous flowers is an 
advance on the production of entomophilous 
flowers. Cleistogamous blossoms are obviously 
more economical. 

In the case of the malvas, epilobias and 
geraniums, where we see, side by side, races 
of which the individuals produce insect-fertilised 
flowers and those that are characterised by self- 
fertilised flowers, the latter are quite as thriving 
as the former. 

The common groundsel, which, according to 
Lord Avebury, is ''rarely visited by insects," 

flourishes like the green bay tree, as many 



Insects and Flowers 

gardeners know to their cost. The same may 
said of the pimpernels. In this connection it 
is important to bear in mind that the anemo- 
philous, or wind-fertiHsed, angiosperms, as, for 
example, the grasses, are believed to be de- 
scendants of insect-fertilised or entomophilous 

A weighty objection to the theory that the 
colours of flowers have been developed because 
they attract insects has been urged by Mr E. 
Kay Robinson, namely, that among wild flowers 
the most highly coloured ones are the least 
attractive to insects."^ 

''Show me," writes he, on page 222 of The 
Country-Side for March 20, 1909, **the insect- 
collector who will seek for specimens among the 
brilliant scarlet poppies. Of what use is the 
dog rose, with its large discs of pinky-white, 
to him ? On the other hand, does he not find 
that by far the most attractive flowers are the 
almost invisible spurge laurel blossoms in 
February and March, the fuzzy sallow catkins 
in March and April, the bramble blossom in 
midsummer, and the ivy's small green flowers 
in autumn ? Of these only the bramble has any 
pretensions to colour, and if you try, as I have 
tried, the experiment of picking off every petal 
from sprays of bramble blossoms you will find 
that its attraction to moths does not appear 


^^-^^^.r. Y^t ; d ^.W r^C^ ^M^^ „.^ ^ 

The Making of Species 

The fact that insects do visit many con- 
spicuously coloured flowers does not show that 
the colour attracts them, when the fact is borne 
in mind that they neglect others which are 
equally coloured, while the flowers which they 
particularly haunt are inconspicuous. Con- 
spicuous flowers which have abundance of 
nectar attract insects, of course, but so do 
inconspicuous flowers which have nectar. If 
they have no nectar, neither the conspicuous 
nor the inconspicuous flowers attract insects 
other than pollen or petal eaters, whose visits 
are not good for the plant. This shows that 
the nectar attracts the insects and that the 
colour of the flowers makes no difference." 

In autumn many leaves assume bright and 
beautiful tints. These are not believed to be 
in any way useful to the plant. The autumnal 
hues and shades are regarded, and rightly re- 
garded, as the garb of death and decay. Such 
colours are the result of the oxidation of the 
chlorophyll or green colouring matter of the 
leaves. Why should not the colours of the 
petals of the flowers, which wither and fade 
long before the green leaves do, be due to a 
similar cause? The bright colours of fruits 
are supposed to have been effected by natural 
selection in order to attract fruit-eating animals. 
Surely a hungry animal does not require that its 
food be brightly coloured in order to find it ! We 



must remember that during the greater part of the 
year most animals have no occupation save that 
of finding their food. Inconspicuously coloured 
fruits, like those of the ivy, are frequently eaten 
by birds. The bright colours of some ripening 
fruits are undoubtedly the colours of decay. 
Many fungi and seaweeds have bright colours. 
It is never hinted that these are of any direct 
utility to their possessor. 

Every flower, every plant, every organism 
must be of some colour. 

Many flowering plants produce honey. This 
is said by some botanists to have been directly 
caused by natural selection, because the honey 
attracts insects. Possibly those who take up 
this attitude are putting the cart before the horse. 
It is probable that honey, like oxygen, is an 
ordinary product of the metabolism of the plant, 
and that the visits of bees and other insects to 
such plants are the result rather than the cause 
of the honey being there. Boisier found that 
some plants, for example, Potentilla tormentilla 
and Geum urbanum^ gave honey in Norway, but 
very little near Paris. 

He further discovered that by supplying certain 
plants copiously with water he could induce them 
to produce more than their normal output of 

As is their habit, Neo- Darwinians have 
pushed their pet theory to absurd lengths in its 


The Making of Species 

application to flowers. They assert that the 
visits of insects are responsible for not merely 
the general colour of every flower, but also the 
various lines, spots, and other markings of 
flowers. The lines that frequently occur on the 
petals are supposed to guide the insects to the 
honey ! This particular refinement of Neo- 
Darwinism, to quote Kay Robinson, ** needs 
little discussion. Insects have very poor sight. 
You can see this when a bee or a butterfly flies 
bang against a whitewashed wall ; when a wasp 
pounces upon a black spot on a sunlit floor, mis- 
taking it for a fly ; or when a settled dragon-fly 
will allow you to poke it in the face with the end 
of a walking-stick, although it will be off like a 
flash if you raise your arm. There is, therefore, 
large reason to doubt whether insects can even 
see the fine lines in the throats of flowers which 
are supposed to guide them to the nectar. It is 
rather absurd, too, to suppose that such lines can 
be needed, since insects come in swarms to in- 
conspicuous and apparently scentless flowers or 
to 'sugared' tree-trunks in the dark. Where 
there is nectar, insects which have come to the 
feast from a distance need no pencilled lines to 
guide them over the last quarter of an inch of 
their journey." 

Neo- Darwinians further assert that the scents 
of flowers have been developed by natural selec- 
tion because they serve to attract insect visitors 


Scents of Flowers 

to the flowers. In support of this contention 
it is urged that the most highly scented flowers 
are not usually the most conspicuous ones, since 
it is not necessary for a flower to be both highly 
coloured and strongly scented. Again, those 
flowers which open at night are usually very 
highly scented. 

Plausible though this view seems, there are 
weighty objections to it. These are so admirably 
summarised by Kay Robinson in the issue of 
The Country-Side for March 27, 1909, that we 
feel we cannot do better than reproduce his 
words : — 

"It is true that many flowers which are 
strongly scented are visited by insects, but these 
flowers have abundance of nectar, and the insects 
come in spite of the scent, and not on account of 
it. They visit unscented flowers, provided that 
they have nectar, equally freely ; and they do 
not visit flowers which have scent without nectar. 

** Moreover, fruits are more generally scented 
even than flowers ; but what explanation have 
those, who attribute the scents of flowers to the 
tastes of insects, for the scents of fruits .>* Insects 
which visit fruits are only robbers. Therefore, 
if we say that plants have scents for the purpose 
of attracting insects, we accuse all plants which 
have scented fruits of attempted suicide. 

** There are hosts of plants, again, with scented 
leaves. Here also the insects are only robbers, 


The Making of Species 

and it is quite clear that the scent is not useful 
in attracting insects. If, therefore, you adopt the 
insect theory to explain the scents of flowers, you 
must invent entirely new theories to explain the 
scents of fruits and leaves." 

It is thus evident that the ordinarily accepted 
explanation of the colours, scents, and markings 
of flowers is far from satisfactory. 

Mr E. Kay Robinson has put forth in recent 
issues of The Country-Side (March 20, 27, and 
April 3, 1909) quite a new explanation of the 
phenomena, and one which deserves careful con- 
sideration. He maintains that " the real, primary, 
and original meaning of the colours, markings, 
nectar and scents of flowers is not to attract 
insects, but to deter grazing and browsing 

" I say," he writes, '* that grazing and browsing 
animals avoid eating conspicuous flowers. I have 
watched a flock of five hundred sheep pass across 
a yard-wide strip of close-nibbled turf on the 
Norfolk coast, grazing as they passed, and the 
number of open daisy blossoms after they had 
passed seemed the same as before they came. 
Every one of five hundred sheep had eaten some- 
thing from that yard of grass, and not one had 
eaten any of the hundred and thirty odd daisies. 

" Every summer the farm horses are turned 
into the same old pasture, and as the summer 
wanes the field always presents the same appear- 


Kay Robinson's Theory 

ance — the green grass close-grazed, the tall butter- 
cups left standing high. 

*'Once, leaning over a gate with friends, I 
pointed out that a flock of sheep grazing in a 
sainfoin field were nibbling the greenstuff close, 
but were not eating the flowery stalks, when one 
sheep near us accidentally pulled up a whole 
sainfoin plant by the roots and proceeded to 
munch it upwards. Inch by inch the stem passed 
into its jaws, and I began to be afraid that it was 
going to establish an ' exception ' to my rule. 
But, just when the bright cluster of pink sainfoin 
blossom was within two inches of its teeth, it 
gave an extra nip, and the flower head fell to the 
ground, and the sheep resumed its search for 

" I do not say that this would always happen 
— -I should be sorry for any theory which depended 
upon the intelligence of a sheep — but it was a 
very striking object-lesson to my two companions; 
and any one who looks around during this summer 
with an inquiring mind will find plenty of evidence 
that grazing, browsing, and nibbling animals avoid 
flowers, and stick to greenstuff when they can 
get it. 

** I do not say that all animals avoid the same 
flowers. Horses, for instance, may dislike large 
flowers like roses and conspicuous yellow flowers 
like buttercups, but they will bite off flat clusters 
of minute white or pale yellow flowers, such as 


The Making of Species 

yarrow or wild parsnip. These distinctions made 
by certain kinds of beasts will probably in the 
future be found to afford valuable evidence as to 
the regions of origin of our flowers and animals. 
Such plants as the yarrow and the wild parsnip, 
for instance, probably did not originate in the 
home of the wild horse, because they are not 
protected against it. 

" As a general rule, however, there is abun- 
dance of evidence that plants with conspicuous 
flowers gain a large advantage in the struggle for 
existence, because grazing and browsing animals 
avoid them ; while there is no real evidence at 
all that conspicuous flowers attract insects." 

Kay Robinson extends this explanation to the 
shape, the scent, and the nectar of flowers. He 
admits that many flowers are adapted to the visits 
of insects, but this is, he asserts, but a secondary 
result. The ''real, primary meaning" of the 
shapes of flowers of curious configuration is, he 
insists, '*a deterrent to grazing or browsing 

According to him plants, like the snap-dragon, 
which have *' blossoms in the semblance of a 
mouth," are avoided by grazing animals, because 
they mistake such flowers for mouths, and have 
no wish to be bitten! Orchids, he asserts, ''are 
strongly deterrent to grazing and browsing 
animals, which are looking for greenstuff, and 
regard these gaudy, spidery, winged blossoms as 


Kay Robinson's Theory 

live creatures." ** If this is not the truth," he 
asks, " will any adherent of the theory that we 
owe the shapes of flowers to insects explain why 
some of our common British orchids are so like 
bees, spiders, etc. ? Some which have no parti- 
cular resemblance to any insect still exhibit weird 
shapes, suggestive to the human mind of living 
things, such as lizards, etc. The reason why they 
look like bees, spiders, lizards, and various un- 
classed creatures is quite simple. Grazing 
animals are looking for greenstuff, and do not 
wish to eat living creatures which may bite or 
sting or taste nasty. Thus the orchids have 
acquired the power of looking like creatures. 

** Every one," he continues, " who is familiar 
with the blossom of the wild carrot — a flat head 
of minute, dull-white blossoms — must have 
noticed how very often the centre blossom in 
each head is purplish or reddish-black. This 
makes it very conspicuous in the middle of the 
flat white flower head. Now what conceivable 
use can this barren little blackish blossom — 
scarcely bigger than a pin's head — be to the 
wild carrot plant if we regard the flat head of 
white flowers as an attraction to the sight of 
insects ? If, on the other hand, we rightly regard 
the flat head of white blossoms as an advertise- 
ment to grazing animals that it is not wholesome 
greenstuff, but innutritions blossoms liable to be 
infested with ants and other stinging insects, we 


y .>-■ 

The Making of Species 

see at once the great use of this small blackish 
flower in the middle. It looks like an insect, and 
possibly in the home of the wild carrot there is 
some minute blackish insect with a peculiarly 
villainous smell or taste — or perhaps a potent 
sting — which grazing animals carefully avoid 
whenever they can see it. Thus the wild carrot 
flourishes ; though here in Britain — where the wild 
carrot has established itself now — we may fail at 
first to see the exact meaning of the trick. I 
think, however, that, when we understand it, it 
fits admirably into the theory that the shapes 
and colours of flowers are primarily useful as 
deterrents to grazing and browsing animals and 
not as attractions to insects. 

*' Thus we see," he concludes, '' that the queer 
shapes of these orchids, which are a great stum- 
bling-block in the way of those who preach that 
we owe the shapes of flowers to the tastes of 
insects, become a strong confirmation of my 
theory that we owe the shapes of flowers to graz- 
ing and browsing animals." 

Of the nectar of flowers, Kay Robinson 
writes : ** Since this is eagerly sought for by 
hosts of insects, whose visits are in most cases 
useful to the flowers, it seems only natural to 
suppose that we see cause and effect in this 

'' Here, however, I will outline my theory of 
the origin of nectar and of flowers in general. 


Kay Robinson's Theory 

** I think there is no doubt whatever that all 
the parts of a flower are modified leaves. The 
original type of flowering plant — I think we may 
safely assume — had a single stem and produced 
its seed at the summit, as the crown of its year's 
endeavour. The flower, before it became what 
we would recognise as a flower, was a cluster of 
protecting leaves round the seed-making parts of 
the plant. To the production of the seed the 
whole energies of the plant were devoted, and 
into the cluster of leaves at the top of the stem 
all the essences of the plant were concentrated. 
If during the coming spring you handle and 
examine the leaves at the end of the strong 
shoots of thorns or fruit bushes, you will find that 
the surface of the young leaves is quite sticky If 
you observe browsing animals also, you will dis- 
cover that — contrary to expectation — they do not 
like strong-growing, juicy shoots, evidently pre- 
ferring mature leaves lower down the branch. 
This shows, I think, that plants have the power 
of protecting their new shoots by crowding into 
them the volatile oils and essences which they 
produce as a protection against animals. Now 
nectar appears always to be distasteful to grazing 
and browsing animals ; and they also dislike 
scented flowers. I think, therefore, that it is 
reasonable to suppose that the nectar and scents 
which now distinguish so many flowers were first 
produced as an exudation of concentrated sap 



The Making of Species 

upon the surfaces of the protecting leaves round 
the seed-making parts of the original flowers. 
As these leaves became more efficiently protective 
by assuming colours, shapes, and markings which 
warned animals of their character, ' so their 
apparatus for producing scent and honey became 
specialised ; and at this point the insect appeared 
upon the scene as a factor in the life's success of 
the plant." 

Such, then, is Kay Robinson's bold and original 
theory. In some respects it seems far-fetched. 
The natural inclination is to ask, " Is it possible 
that cattle can be so stupid, so blind, as to really 
believe that a snap-dragon is the mouth of an 
animal, or that an orchid is a spider ? " 

At present we know so little of animal psy- 
chology that we are not yet in a position to give 
an answer to this question. Horses, we know, 
are apt to be frightened by the most harmless 
things, such as a piece of brown paper lying on 
the road. Mr Robinson's theory should give a 
stimulus to the study of the mind of animals — 
a study which, if properly undertaken, will 
probably throw a flood of light upon some of 
the problems of evolution. Mr Robinson's theory 
equally with the ordinarily-accepted hypothesis, 
utterly fails to explain the first origins of colours, 
scents, etc. When once a flower has acquired a 
certain amount of colour, it is easy to understand 
how that flower may attract insects or repel 


Kay Robinson's Theory 

grazing animals. But how can the origin of the 
colour or other characteristic be explained ? 

We asked Mr Kay Robinson how he would 
account for the great success in the struggle for 
existence of some species of grasses on which 
herbivorous animals feed so largely. He replied, 
in the issue of The Country -Side, dated April 3, 
1909 :— 

'' The grass has a manner of growth which 
defies the grazing animal. Its long, thin leaves 
are constantly pushing upwards from the ground, 
and, if they are grazed down one day, they will 
have pushed up again the next. Moreover, when 
the outside blade of grass has exhausted its power 
of growing, there is another blade inside it with 
many inches still to grow, and another inside that 
which has scarcely begun to grow, and yet another 
further in which has not yet seen daylight ; and 
so on. In a state of nature grazing animals are 
nowhere so numerous on any given patch of 
ground from day to day as to keep down the 
grass. If they were, carnivorous animals would 
stay there to eat the grazing animals, and grow 
fat and multiply. Thus the grazing herds are 
scattered and wandering, followed wherever they 
go by the beasts of prey; and in their absence 
the grass pushes ahead, so that when the grazing 
animals return its clump is larger and its roots 
are stronger, and it is better able to survive 
attack than before. 

s 273 

The Making of Species 

" The method of the clovers and trefoils is quite 
different. When circumstances are favourable 
and enemies few, they will form large-leaved 
luxuriant clumps, with fine heads of blossom ; 
but where grazing animals abound they have 
the power of adapting themselves to altered 
circumstances. They creep so closely along the 
ground that the teeth of the grazing animal can- 
not pick them up between the surrounding grass, 
and they produce leaves so small and short- 
stalked that to eat them would be like nibbling 
the pile off velvet. Any clover or trefoil thus 
growing in self-defence is accepted as the 
* shamrock ' of Ireland ; and it is certainly a 
fine emblem for a race which regards itself 
as surviving in spite of incessant oppression. 

'' These are the reasons, however, why the 
grasses and clovers or trefoils continue to enrich 
old pastures when most of the other plants dis- 
appear, with the exception of daisies and butter- 
cups, and the acid sorrels." 

We should be glad to hear how Mr Robinson 
accounts for the conspicuous flowers in the 
species of "prickly pear" {Euphorbia), which is 
so abundant in India, and which is not browsed 
upon by animals. 

We regret that we are not able to devote more 
space to this most interesting theory. We can 
only add that, even if it fail to become widely 
accepted, it is of great value as showing that it 


Accepted Theories Unsatisfactory 

is possible to offer a plausible explanation of a 
large number of phenomena, which nine out of 
ten botanists explain in a very different way. 

So satisfied are the majority of naturalists with 
the ** insect theory," that they seem of late years 
to have paid but little attention to the subject of 
floral colouration. This affords a striking instance 
of the pernicious influence which Neo-Darwinism 
is exercising on the minds of men to-day. It 
tends to stifle research instead of stimulating it. 

We have now dealt with the theory of protective 
colouration, the theory of warning colouration, 
the theory of mimicry, and the theory of recogni- 
tion markings. We have shown that although 
many organisms undoubtedly derive profit from 
the fact that they are difficult to see in their 
natural surroundings or from their resemblance 
to other organisms, the hypothesis that this in- 
conspicuousness or the mimicry of these animals 
has been caused by the natural selection of small 
variations is untenable. 

Warning colours, we have shown, although a 
disadvantage to their possessors, are sometimes 
seen in nature because they are accompanied by 
unpalatability. The theory of recognition mark- 
ings must, we fear, be laid to rest in the burial 
ground of exploded hypotheses. 

The extreme popularity of the existing theories 
regarding animal colouration and their very 


The Making of Species 

general acceptance are to be attributed, firstly, 
to their simplicity ; secondly, to the fact that they 
have thrown light on many phenomena which 
previously had seemed inexplicable ; thirdly, that 
if we assume, as the great majority of biologists 
do, that evolution has been effected by the 
accumulation of numerous variations, small in de- 
gree and indefinite in direction, we seemed forced 
either to accept Neo- Darwinism or admit that the 
whole subject of animal colouration baffles us, in 
other words, to reject what appears like cosmos 
and substitute for it chaos. 

With a few exceptions, books that deal with 
the colours of organisms, while emphasising 
the evidence in favour of the generally-accepted 
theories, seem almost entirely to ignore the host 
of facts that do not appear to fit in with them. 

This is largely due to the almost unavoidable 
bias of the human mind when obsessed by a pet 
theory. There are none so blind as those who 
will not see. It is also, in part, the consequence 
of the prevalent neglect of the scientific method 
of comparison which leads men to theorise on 
insufficient evidence. This, of course, is a natural 
result of specialisation in biology. Naturalists 
are in the habit of confining their study to the 
habits of the animals of one particular country 
and then making far - reaching generalisations 

As an example of the kind of theorising to 


White Down of Nestlings 

which this method leads, we may cite the often- 
quoted theory which ascribes the green colouring 
of some arboreal fruit-eating pigeons to adapta- 
tion to an existence among tropical foliage, and 
ignores the fact that in America tree-haunting 
pigeons are never of this colour, and that it is not 
by any means universal even among the old- 
world pigeons. 

Similarly, a theory has been advanced (W. P. 
Pycraft, Knowledge, 1904, p. 275) that the white 
down of some nestling birds, is an adaptation 
to resisting the heat of the sun in open nests. 
This is at once negatived by the fact that young 
owls, usually hatched in shaded places, are also 
generally white, while young cormorants, living 
in open nests, are black ; yet the allied darters, 
with the same breeding haunts in some cases, 
have white young. Lest it should be thought 
that black has some especial value in a nestling 
living exposed, we may mention that young 
petrels, which are born in holes, have black or 
dark down. 

As we have already pointed out, naturalists 
in too readily accepting the theory that varia- 
tion is minute in degree and indefinite in 
direction, have raised quite unnecessary diffi- 
culties, even for the selection hypothesis. We 
have cited certain facts, which seem to show that 
variations, as a rule, are not indefinite in direc- 
tion ; of these the most striking is furnished by 


The Making of Species 

birds in which the tail feathers are greatly 
elongated. Were variations indeterminate, we 
might reasonably expect to find that the 
elongation occurred in one particular feather or 
pair of feathers in one species, in another pair in 
a second species, in a third pair in a third species, 
and so on. But this is not the case ; no bird has 
one single long feather in its tail, and when two 
are elongated, as is so commonly the case, these 
are almost invariably the middle or the outside 
pair; e.g.^ in the European bee-eater and pheasant 
it is the former, in the swallow and blackcock, 
the latter. 

Exceptions are so rare that they may almost 
be said to prove the rule ; e.g., although most 
terns have the outer-tail feathers elongated, in 
some of the Noddy Terns {Anous, Gygis) the 
third pair, in others the fourth pair, of tail 
feathers are the longest. This must mean one of 
two things, either that the variation, as regards 
length in tail feathers, other than middle or outer, 
does not ordinarily occur, or that it occurs, but is, 
in some way, inimical to the welfare of the 
species. The latter hypothesis does not seem 
probable, as the Noddies are particularly 
abundant birds where they occur, that is to 
say, in the tropical seas ; therefore, we can only 
conclude that that particular variation has not 
occurred in birds as a whole. 

We have adduced abundant evidence to show 



that mutations or discontinuous variations occur 
in nature ; and as these afford much more favour- 
able material on which natural selection can act, 
it is reasonable to suppose that they have played 
a considerable part in evolution. 

When discussing the phenomena of inheritance, 
we attempted to show that, not improbably, these 
discontinuous variations are due to some re- 
arrangement in the constituent parts of the unit 
characters, or biological molecules, as we have 
called them. 

In this connection we may mention the 
apparently singular phenomenon of different 
species in the same natural group, exhibiting 
either a definite excess or deficiency of plumage 
on the head. Among cranes, most species are 
more or less bald ; but the Demoiselle {Antkro- 
poides virgd) has a fully- feathered head with 
long side-plumes, while the head of the Stanley 
Crane {A . paradisea) appears to be swollen, so 
abundantly is it feathered. The crowned cranes, 
although bare - cheeked, have double crests, 
the two parts of which have been respectively 
compared to a pen - wiper and a bunch of 
toothpicks ! 

Among the guinea-fowls, several species are 
crested, while others, as, for example, the 
domestic one, are bare-headed. 'Now, on the 
theory of evolution, by accumulation of minute 
variations, phenomena such as these are difficult 


The Making of Species 

of explanation ; but, on the assumption that a 
slight rearrangement of the biological atoms in 
the molecule may produce very diverse results, as 
we see in the case of chemical molecules, and 
of seasonally dimorphic butterflies, there is 
no particular ground for surprise at such a 

In this connection we may cite the significant 
fact, so well known to canary breeders, that two 
crested birds when mated tend to produce a bald- 
headed one. 

If the colour of any part of an organism be 
due to the internal arrangement of the constituent 
parts of the biological molecule from which it is 
derived, we should expect any rearrangement of 
the component parts to produce quite a different 
colour. In other words, we should expect occa- 
sionally to see colour-mutations. These are pre- 
cisely what we do see. Similarly, if the scheme 
of colouring of an organism be due to a certain 
grouping of biological molecules, we should ex- 
pect the same scheme of colouring to occur in 
organisms which are not nearly related. This, 
too, we observe in nature. 

Many of the phenomena of mimicry, and all 
the cases which we have cited as pseudo-mimicry, 
seem to us to be referable to this. 

Take, for example, the magpie colouration in 
birds — that is to say, a scheme of colouring in 
which the body is white, and head, wings, and 


Magpie Colouring 

tail black. This occurs in the following birds 
belonging to the most diverse groups : — 

The Magpie. 

The Magpie Tanager (Cissopis leveriana). 

The Magpie Robin (Copsychus saularis), cock 
only ; in the hen the black is replaced by brownish 

The Pied Won^y^'dX^x [Entomophila picata). 

The Chaplain Crow (white-bodied form of the 
hoodie crow). 

The New Ireland Swallow Shrike {Artamus 

The Magpie Goose {Anseranas me lano Uncus). 

Combinations of this kind, in which the black 
is replaced by brown or grey, are excessively rare. 

On the other hand, we see in several birds the 
combination in which the white is replaced by 
yellow : — 

The Common Troupial [Icterus vulgaris). 

The Black-headed Oriole (Oriolus me lano 

The Black-and-yellow Grosbeak, male only. 

What we may call imperfect magpie coloura- 
tion, i.e. where the head becomes white, occurs 
in several species of birds. The head of a black 
species sometimes becomes white as a mutation ; 
in the domestic Muscovy duck, for example, an 
individual is sometimes produced having a white 
head, although the black of the remainder of the 
plumage remains unchanged. 


The Making of Species 

As examples of this scheme of colouration we 
may cite — 

Black-and-white Fruit Pigeons (Myristicivorce), 

Several Gannets {Sula cafensis, S, serrator, 

Swallow- tailed Kite {Elanoides furcatus). 

Several Storks (Euxenura maguari, Anastomus 
oscitans, Pseudotantalus cinereus). 

Moreover, a common variety of the barn-door 
fowl has also a white body and black primaries 
and tail, showing that this scheme of colour may 
arise as a mutation. 

A further elimination of black in the tail and 
body leads us to white birds with more or less 
black wings : — 

White Storks (Ciconia alba, C boycianay and 
EuxeuMi^a maguari). 

The White Crane {Grus leucogeranus). 

The Snow Geese (Chen nivalis, C. rossi). 

The Common Gannet (Sula bassana). 

The White Buzzard (Leucopternis). 

The Scavenger Vultures (Neophron), 

A recurring combination in mammals is black, 
with a white marking on the breast. 

Most of the bears, even young brown bears, 
show a tendency to this. It is also found in the 
Tasmanian devil, and in varieties of our domestic 
cats, rats, and dogs ; also in the domestic duck. 

The white-spotted pelage, not uncommon in 
deer, especially fawns, is curiously repeated in 



the Australian carnivorous marsupials, known 
as Native Cats (Dasyurus). 

In domestic animals we frequently find the 
following localisation of white — white socks, 
collar, breast, and muzzle. The arrangement 
occurs in cats, dogs, rabbits, guinea-pigs and 
mice, also in the horse and pig, but without 
the collar. The arrangement is not seen in 
goats, cattle, or sheep, nor in wild animals of 
any kind. This would lead to the conclusion 
that the combination is correlated with some 
character unfavourable to survival under natural 

Many variations which frequently occur among 
both wild and domestic animals do not persist in 

As instances of such variations we may men- 
tion pure albino forms, that is to say those in 
which pigment does not occur in the eyes. 

It is easy to see why this variation is not 
allowed to persist in nature. Its possessors are 
handicapped by bad eyesight, and so have no 
chance of surviving in the struggle for existence. 
It is thus that natural selection acts. On the 
other hand, white species with pigmented eyes are 
fairly numerous. These enjoy normal eyesight, 
but labour under the disadvantage of being easily 
seen by their foes. Hence we find that white 
species generally either occur in a snowy habitat, 
or are powerful and both able and ready to 


The Making of Species 

defend themselves. In this connection it is inter- 
esting to notice that in New Zealand all birds, 
whether introduced or indigenous, are particularly 
liable to albinism. Owing to the fewness of their 
enemies these albinistic forms are able to persist. 

A variation, or rather a mutation, that fre- 
quently occurs among domesticated birds, but 
which is seen in very few wild species, is that 
which takes the form of white primary feathers 
on the wing. This variation must often occur in 
nature, but it rarely establishes itself, apparently 
because white feathers do not resist wear so well 
as coloured ones do. 

Black-and-yellow colouration occurs in several 
widely separated species of birds. The arrange- 
ment of the two colours follows to some extent 
the same rules as the black-and-white combination. 

Several birds have a yellow body with black 
head, wings, and tail, such as — 

The Black -headed Oriole (Oriolus melano- 

The Black-and- Yellow Grosbeaks {Pycnor- 
hamphus icteroides^ P. affinis) (cock). 

The Common Troupial [Icterus vulgaris). 

In others the black on the head is nearly or 
quite suppressed, that on the tail remaining to a 
greater or less extent ; such are — 

The Golden Orioles {Oriolus galbula, O. kundoo, 

Several species of Icterus, 


By perinisszon of Messrs. Hiiichhison Gr Co. 

This species {Icterus vulgaris) is that most frequently seen in captivity ; 
the pattern of colour is found in several uther allied forms 


By perniissioji oi' Messrs. Hjitchiuson &• Co. 

Several other orioles besides this (O. inelanocephalus^ have the black head. 

Biological Molecules and Colour 

Several fly-catchers of the genus Piezorhynchus 
(males only). 

We have said sufficient to show that certain 
combinations of colours recur in nature in species 
which are neither nearly related to one another 
nor subjected to similar environment. For such 
phenomena it is difficult, If not Impossible, to 
account on the theory that natural selection, 
acting on minute variations, is responsible for 
all the varied colouring of the animal kingdom. 
The facts, however, are in accordance with the 
supposition that the organism is the result of the 
growth and development of a number of units or 
biological molecules which exist in the fertilised 

If there be any truth In the supposition, 
the colouration of every animal must be due to 
the development of one or more of these mole- 
cules. Colouration may be expression of the 
arrangement of all the molecules in the fertilised 
^^g, or it may be due to the development of a 
number of molecules whose function is to deter- 
mine the colouring of an organism, or it may be 
the result of the development of one such mole- 
cule, which perhaps splits up in such a way that 
a portion attaches itself to each of the other 

But it is idle to speculate on this point. As 
we have already insisted, the tendency to build 


The Making of Species 

up elaborate theories on very slender foundations 
is a too frequent failing of zoologists. We desire 
merely to emphasise the fact that the phenomena 
of animal colouration almost force us to the con- 
clusion that the colouring of each organism is the 
result of the development of a number of units. 

It may be objected that, if this be the case, the 
number of the units which contribute to the colour 
of any organism must be exceedingly large, since 
we see in nature an almost limitless number of 
different schemes of colouring. If the colour of 
each animal be the result of the development of 
a few units, it might be thought, firstly, that the 
diversity of schemes of colouration which we 
observe in nature could not possibly occur ; 
and secondly, that, under such circumstances, 
the colour pattern of a bird or beast should 
be of the nature of a mosaic, each colour being 
sharply defined and separated from every other 
colour, instead of the colours shading one into 
the other, as is so frequently the case. 

Such objections would be based on a miscon- 
ception as to the nature of the units which com- 
bine to produce the colouration of an organism. 
These units show themselves as centres of develop- 
ment of colouvy as points from which the colour 
or colouring they represent spreads, until it 
meets and mingles with other patches of colour 
which are being developed from other centres. 
The colour produced at one centre may spread 


Mr Tylor Quoted 

more rapidly than that which forms at another ; 
this, of course, will result in a preponderance in 
the organism of the colour which is produced at 
the former centre. 

Further, we must bear in mind that the develop- 
ment of each colour-producing unit is largely 
affected by conditions external to it, as we shall 
see when dealing with Sexual Dimorphism. 

More than one naturalist, who has paid careful 
attention to the subject of animal colouration, has 
perceived that through the apparently endless 
diversity of the colouring of organisms something 
like order runs. 

Over thirty years ago Mr Alfred Tylor called 
attention to this important fact. That observer, 
whose views met with the approval of Wallace, 
was of opinion that colour follows structure, and 
that in a many-hued animal it changes at points 
where the function changes. 

"If," writes Mr Tylor, "we take highly 
decorated species — that is, animals marked by 
alternate dark or light bands or spots, such as 
the zebra, some deer, or the carnivora, we find, 
first, that the region of the spinal column is 
marked by a dark stripe ; secondly, that the 
regions of the appendages, or limbs, are differ- 
ently marked ; thirdly, that the flanks are striped 
or spotted, along or between the regions of the 
lines of the ribs ; fourthly, that the shoulder and 
hip regions are marked by curved lines ; fifthly, 


The Making of Species 

that the pattern changes, and the direction of the 
lines, or spots, at the head, neck, and every joint 
of the limbs ; and, lastly, that the tips of the ears, 
nose, tail, and feet, and the eyes are emphasised 
in colour." 

More recently Mr J. Lewis Bonhote has 
devoted much attention to this important subject. 
The results of his researches are summarised on 
page 185 of vol. xxix. of the Proceedings of the 
Linncean Society^ and on page 258 of the Proceed- 
ings of the Fourth International Ornithological 
Congress, 1905. Mr Bonhote states that the 
presence or absence of colour tends almost in- 
variably to make its appearance, first of all, on 
certain definite tracts, common to mammals and 
birds alike, which he c^[\s pcecilomeres. 

*' Poecilomeres," he writes, "are situated on 
the following parts, viz., chin, malar stripe, max- 
illary stripe, a spot above and slightly in front of 
the eye, a spot below or slightly behind the eye, 
the ear, crown of the head, occiput, fore-end of 
sternum, vent, rump, thighs, wrist, shoulders 
(above and below). 

'' Now, there is hardly any species of bird on 
which one or more of these poecilomeres is not 
' picked out ' (to use a painter's expression) in 
some colour different from that of the surround- 
ing parts, and, in fact, most of the so-called 
recognition or protective markings will be found 

on these patches. 



'* On the other hand, among many species the 
differentiation of colour on the poecilomeres is 
not so conspicuous as to attract the eye or to 
serve in any way for protection or mimicry, ye^ 
we still find them marked by differences of colour 
so slight that, unless especially looked for, they 
would never be noticed. 

** Or, again, some species occasionally, but not 
invariably, show a few white feathers on certain 
parts of their body, and, when such is the case, 
it will be found that these white feathers appear 
on the poecilomeres. . . . There is hardly a 
species in which examples of these poecilomeres 
may not be found. . . . The Kingfisher [Alcedo 
ispidd) shows the various head poecilomeres very 
clearly, and as examples of inconspicuous differ- 
ences on these tracts, the rump of the hen sparrow 
(Passer domesticus) and hen chaffinch {Fringilla 
coelebs^, the malar stripe and dark ear-patch of 
the" hen Yellow Bunting [Emberisa citrinella), 
and the dark ante-orbital patch of the Barn Owl 
(Strix fiammea) are familiar examples. And, 
lastly, as an instance of the class where a few 
white feathers frequently, but not invariably, 
appear, the young of the cuckoo {Cuculus cano- 
rus) forms a good example. 

** These spots may, however, appear in a tran- 
sitory manner, as, for instance, where a change 
of plumage (not necessarily moult) is occcurring." 

As an instance of this, Bonhote cites the case 
T 289 

The Making of Species 

of a young male Shoveler (Spatula clypeata\ " in 
which the metallic colour on the head first showed 
itself on the post-orbital and auricular poecilo- 
meres, gradually meeting and joining up across 
the head with the crown and occipital poecilo- 
meres, and then finally spreading forwards. And 
it may be well to note that the joining up of the 
auricular and post-orbital poecilomeres formed 
a metallic patch similar in size and position to 
that found in the male Teal (Querquedula crecca), 
and, further, in the last stage, when the whole 
head, except the portion round the beak, was 
metallic, the markings are similar to those found 
permanently in the hen Scaup {Fuligula marila). 

Now, these resemblances taking place in the 
normal pure-bred wild shoveler, the question of 
reversion does not come in, and no one would 
suppose these resemblances due to anything 
more than transitional variation, and it is the 
object of this portion of the paper to show that 
variation in colour follows along definite lines." 

Mr Bonhote continues : *' As a further illus- 
tration of how widely spread these lines are 
throughout the mammalian and avian kingdoms, 
we may note the assumption of the brown head 
in the case of the Black-headed Gull [Larus 
ridzbundus), which invariably follows each year 
on lines similar to those related in the case of 
the shoveler, and . . . the method by which, on 
the approach of winter, the stoat assumes his 


Biological Molecules 

white dress, is (although the change is from 
brown to white) again conducted along precisely- 
similar lines." Mr Bonhote argues with great 
force that, as the process occurs in two animals 
so widely separated, the fundamental cause must 
be a deep-seated one. There can be no doubt 
that these poecilomeres of Bonhote are connected 
with our biological molecules. Each of these 
poecilomeres is the result of the development 
of one of these unit characters ; each is to be 
regarded as the centre of activity, the sphere of 
influence of a biological molecule, or the portion 
of one, which controls the colouring of a definite 
region of the organism. In the case of creatures 
which display the same colour throughout, these 
molecules all give rise to the same kind of 
colouring ; in the case of animals which display 
a variety of colours and markings the various 
molecules give origin to various colours. But 
we must bear in mind that the final colour to 
which each colour-producing molecule gives rise 
depends to some extent on circumstances other 
than the constitution of the molecule. Thus it 
is that the young in most organisms differ in 
colour and marking from the adults. On this 
also depends the phenomena of seasonal and 
sexual dimorphism. The same colour-producinp- 
molecule may give rise to one colour under one 
set of conditions and to a totally different colour 
under another set of conditions. 


The Making of Species 

It is a significant fact that under abnormal 
conditions the feathers of birds tend to disappear 
precisely on those spots where the poecilomeres 
of Bonhote occur. 

Thus in a sickly cage bird the feathers 
frequently show a tendency to fall off on the 
following spots : crown of head, lores, jaws, 
head generally, rump, vent and thighs. 

Many wild birds — as, for example, the cranes 
—display patches of naked skin on the head, 
and these are usually situated on poecilomeres. 
Similarly, natural excessive developments of 
plumage tend to occur on the poecilomeres, or, 
rather, the spots characterised by poecilomeres — 
for example, the train of the peacock. Loral 
plumage, it is true, is seldom long, but is often of 
a peculiar nature. 

Colour mutations tend to occur on the poecilo- 
meres. Thus it is that these poecilomeres often 
form the distinctive characters and markings of 
allied species. This is precisely what we should 
expect if the poecilomeres correspond to bio- 
logical molecules and mutations are the result of 
the rearrangement of the constituent parts of 
these molecules. 

Still more significant is the fact that the colour- 
markings in hybrids tend to follow poecilomeres. 

Bonhote has performed a large number of 
experiments in hybridising ducks. Some of his 
hybrids were produced from three pure ancestors, 


Biological Molecules 

as, for example, the pintail, the spotbill, and the 
mallard ; others from two ancestors. Some of 
these hybrids were crossed with other hybrids, 
and others with the parent forms, hence Bonhote 
secured a number of hybrids, each of which had 
a distinctive appearance ; but all the variations 
appearing among the hybrids were found to start 
on one or more of the poecilomeres. 

Certain of the hybrids showed a resemblance 
to one or other of the parent species, others were 
unlike either parent, and resembled either no 
known species or species other than their parents. 

When a hybrid shows a resemblance to a species 
other than that to which either parent belongs, it 
is said to exhibit the phenomenon of atavism or 
reversion, — the individual is supposed to have 
been "thrown back" to an ancestral form. 

The true explanation of the phenomenon would 
seem to be that, as the result of the crossing, 
biological molecules in the fertilised ^<gg have 
been formed which, on development, give rise to 
combinations of colour like those seen in other 

Thus the phenomena of " mimicry " and ** re- 
version " are, we believe, due to the fact that in 
the fertilised ^^^ of both the pattern and its copy 
a similar arrangement of biological molecules 
obtains. If we regard the sexual act as re- ^^ 
sembling in many respects a chemical synthesis, 
the phenomenon need not surprise us. 1/ 

293 1^ 

The Making of Species 

To sum up, the observed facts of animal 
colouration seem to indicate that there are in 
each organism some twelve or thirteen centres of 
colouring, which we suggest may correspond with 
portions of the fertilised egg. From each of 
these centres the colour develops and spreads, 
so that every part of the organism is eventually 
coloured. These centres of colouring are not 
altogether independent of one another. Some- 
times they all give rise to the same hue, in which 
case we have a uniformly-coloured organism, such 
as the raven. More often from some one colour 
develops, and from others another colour ; if 
these two colours happen to be black and white, 
the result is a pied organism, which displays a 
definite pattern due to the correlation of the 
various colour-producing biological molecules. 

Thus it occasionally happens that two widely 
different organisms exhibit very similar mark- 
ings, and therefore resemble one another. When 
this resemblance is believed to be of advan- 
tage to one or other of the similarly-coloured 
species, naturalists call it mimicry, and assert that 
the likeness is due to the action of natural selec- 
tion ; but where neither organism can profit by 
the resemblance, zoologists make no attempt to 
explain it. What we suggest is that the coloura- 
tion of an animal depends upon the structure, or, 
at any rate, the nature, of the parts of the egg 
which produce these centres of colour. But this 


Biological Molecules 

is not by any means the only cause that deter- 
mines the colouration of the organism. If it 
were, young creatures in their first plumage 
would invariably resemble the parents, the two 
sexes would always be alike, and there would be 
no such phenomenon as seasonal dimorphism. 

As a matter of fact, the portions of the egg (we 
call them, for the sake of clearness, colour-produc- 
ing biological molecules) which give rise to the 
pcecilomeres exhibit themselves merely in the 
shape of tendencies ; the ultimate form the 
colouring will take depends to a large extent 
upon other and extraneous circumstances, such 
as the secretion of hormones. 

Thus it is that organisms seem to display an 
almost endless diversity of colouration. But 
beneath all this diversity we see something like 
order. It occasionally happens (w^y, we do not 
know) that one, or more, of the biological mole- 
cules which make up the nucleus of the fertilised 
ovum becomes altered in the sexual act, with 
the result that a discontinuous variation or muta- 
tion appears in the resulting organism. The 
mutation may be a favourable one, or one which 
does not affect in any way the chances of an 
organism in the struggle for existence, or an 
unfavourable one. In the last of the three cases 
the organism will perish early and not leave 
behind any offspring exhibiting its peculiarity. 

It is thus that natural selection acts. Natural 

295 V 

The Making of Species 

selection weeds out relentlessly all organisms 
which display unfavourable variations. It is 
thus obvious that many species may, and we 
believe do, exist which possess characters of no 
direct utility to them, or even slightly harmful 
ones. For this reason Wallace and his fol- 
lowers fail in their attempts to prove that 
every patch of colour in every organism is of 
direct utility. Natural selection has to take an 
animal as it finds it — the good with the bad. If 
an organism as a whole is not wanting — that is to 
say, if it is able to hold its own against other 
organisms, and is fitted to fill any place in nature 
— that organism will probably survive, although it 
may be defective in many respects. As its name 
implies, natural selection is a mere selecting 
agency. It has to choose from what is presented 
to it. It is not, as many seem to think, a manu- 
facturer or inducer of variations. Natural selec- 
tion can no more make an animal vary in any 
given direction than the human breeder can. Its 
power is limited to the destroying of all variations 
which do not pass the test prescribed by it. 




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. 

IN some species the sexes are so similar in 
appearance that it is not possible to tell 
by mere outward inspection to which 
sex a given individual belongs. 
In other species the sexes differ so widely in 
external appearance that it is difficult to believe 
that the male and the female belonof to the same 
species. Between these two extremes are a 
great number of species in which the sexes are 
more or less dissimilar. Those species in which 
the sexes differ in appearance are said to be 
sexually dimorphic. The phenomena of sexual 
dimorphism are fatal to that form of Neo- 
Darwinism which sees in natural selection an 


The Making of Species 

explanation of all the peculiarities of animal 
structure and colouration. 

It is not easy to understand how natural selec- 
tion can have caused marked sexual dimorphism 
in a species where the habits of the sexes are 
the same, in the Paradise Flycatcher ( Terpsiphone 
paradisi), for example, where the cock and the 
hen obtain their food in the same way, and share 
equally the duties of nest-building, incubation, and 
feeding the young. 

Of course, in all species where each individual 
carries only one of the two kinds of sexual organs, 
there must of necessity be some slight difference 
between the individuals that carry the male organ, 
which performs one function, and those that carry 
the female organ, which performs another function. 

But in many species the sexes display differ- 
ences which have no direct connection with the 
generative organs- — for example, the deer, where 
the stag alone has horns. 

Those characters which differ with the sex, 
but are not directly connected with the organs 
of reproduction, are known as secondary sexual 

In nearly all species where the male and 
female differ in beauty, it is the male who 
surpasses the female. Natural selection is, 
in many cases, not able to explain the origin 
of these differences, or why, when they occur, 
the male should be more beautiful than the 


By permisiiojt of the Fo7-ei^n Bird Clicb 

This species {Tetraemcra ?-egia) is a typical example of 
seasonal sexual dimorphism, the male being long-tailed 
and conspicuously coloured only during the breeding 
season, and at other times resembling the sparrow-like 

Theory of Sexual Selection 

female. This Darwin saw. In order to account 
for the phenomena of sexual dimorphism, he 
formulated the theory of sexual selection. This 
hypothesis is based on the assumption that there 
is, in all species of animals, a competition among 
the males to secure females as mates. It is not 
difficult to understand how this competition 
arises in polygamous species. Assuming that 
approximately equal numbers of males and 
females are born (an assumption which appears to 
be justified as regards the majority of species), it 
is clear that for every male who secures more 
than one wife, at least one male will be obliged 
to live in a state of single blessedness. 

But how can there be competition in the case 
of monogamous species ? The sexes being ap- 
proximately equal in number, there are sufficient 
females to allow of a mate for every male. 

Such is the nature of things, said Darwin, that, 
even under these circumstances, there is com- 
petition among the males for females. 

" Let us take any species," he writes, on page 
329 of The Descent of Man (Ed. 1901), **a bird 
for instance, and divide the females inhabiting a 
district into two equal bodies, the one consisting 
of the more vigorous and better-nourished in- 
dividuals, and the other of the less vigorous and 
healthy. The former, there can be little doubt, 
would be ready to breed in the spring before the 
others ; and this is the opinion of Mr Jenner 


The Making of Species 

Weir, who has carefully attended to the habits of 
birds during many years. There can also be no 
doubt that the most vigorous, best nourished, 
and earliest breeders would on an average 
succeed in rearing the largest number of fine 
offspring. The males, as we have seen, are 
generally ready to breed before the females ; the 
strongest, and with some species the best armed 
of the males, drive away the weaker ; and the 
former would then unite with the more vigorous 
and better-nourished females, because they are 
the first to breed. Such vigorous pairs would 
surely rear a larger number of offspring than the 
retarded females, which would be compelled to 
unite with the conquered and less powerful males, 
supposing the sexes to be numerically equal ; and 
this is all that is wanted to add, in the course 
of successive generations, to the size, strength, 
and courage of the males, or to improve their 

From this competition among the males there 
arise, firstly, contests between the males for 
mates ; secondly, the preference of the females 
for favoured males. 

It is a matter of common knowledge that at 
the breeding season the males of nearly all, if 
not all, species are very pugnacious. Two 
males often engage in desperate fights for one 
or more females ; the victor drives away his foe 
and secures the harem. In such contests the 


The Law of Battle 

stronger male wins, and thus emerges that par- 
ticular form of sexual selection which Darwin 
termed '^the law of battle." 

"There are," writes Darwin, on page 324 of 
The Descent of Man, "many other structures and 
instincts which must have developed through 
sexual selection — such as the weapons of offence 
and the means of defence of the males for 
fighting with and driving away their rivals — 
their courage and pugnacity — their various orna- 
ments — their contrivances for producing vocal 
or instrumental music — and their glands for 
emitting odours." The former characters have, 
according to Darwin, been developed by the law 
of battle, and the latter, since they serve only 
to allure or excite the female, by the preference 
of the female. 

" It is clear," continues Darwin, " that these 
characters are the result of sexual and not of 
ordinary selection, since unarmed, unornamented, 
or unattractive males would succeed equally well 
in the battle for life and in leaving a numerous 
progeny, but for the presence of better-endowed 
males. We may infer that this would be the 
case, because the females, which are unarmed and 
unornamented, are able to survive and procreate 
their kind. . . . Just as man can improve the 
breed of his game-cocks by the selection of those 
birds which are victorious in the cockpit, so it 
appears that the strongest and most vigorous 


The Making of Species 

males, or those provided with the best weapons, 
have prevailed under nature, and have led to 
the improvement of the natural breed or 

"With mammals," says Darwin {loc. cit., 
p. 763), *' the male appears to win the female 
much more through the law of battle than 
through the display of his charms." 

In the case of birds, however, feminine prefer- 
ence comes more into play. It is well known 
that cocks display their charms to the hens at 
the breeding season, and Darwin believed that 
the hen selected the most beautiful of her rival 

"Just as man," he writes (p. 326 of The 
Descent of Man, new edition, 1901), '*can give 
beauty, according to his standard of taste, to his 
male poultry, or, more strictly, can modify the 
beauty originally acquired by the parent species, 
can give to the Sebright bantam a new and 
elegant plumage, an erect and peculiar carriage, 
so it appears that female birds in a state of 
nature have, by a long selection of the more 
attractive males, added to their beauty or other 
attractive qualities." 

Thus the theory of sexual selection is based 
on three assumptions. Firstly, that there is in 
all species competition among the males for 
females with which to mate. Secondly, that 
this results in either *' the law of battle " among 


Selection by Females 

the males, or selection by the female of one 
among several admirers. Thirdly, that the 
female selects, as a rule, the most attractive of 
her suitors. 

The evidence upon which Darwin founds this 
theory may be thus summarised : — 

1. In cases where the sexes differ in appear- 
ance, or power of song, it is almost invariably 
the cock who is the more beautiful or the better 
singer, as the case may be. 

2. All male birds that possess accessory plumes 
or other attractions, make a most elaborate dis- 
play of these before the females at the mating 
season, hence "it is obviously probable that 
these appreciate the beauty of their suitors." 

3. Darwin was able to cite specific instances 
in which the hens showed preference. 

In the case of polygamous species there can 
be no doubt that there is considerable competition 
among males for their wives. It cannot be said 
that the contention is so well established in the 
case of monogamous species. D. Dewar suggests 
that circumstances may occur in which the hens 
have to fight for the cock, or in which the male is 
in the happy position of being able to select his 
mate. He states his belief that in many cases 
the selection is mutual, as in the case of human 

"I have seen," he writes, on page 13 of 
Birds of the Plains, " one hen Paradise Fly- 


The Making of Species 

catcher ( Terpsiphone paradisi) drive away another 
and then go and make up to a cock bird. Simi- 
larly, I have seen two hen orioles behave in a 
very unladylike manner to one another all 
because they both had designs on the same cock. 
He sat and looked on from a distance at the 

Darwin quotes, on page 500 of The Descent 
of Man, a case of a male exercising selection : 
"It appears to be rare when the male refuses 
any particular female, but Mr Wright of Gelders- 
ley House, a great breeder of dogs, informs me 
that he has known some instances : he cites the 
case of one of his own deerhounds who would 
not take any notice of a particular female mastiff, 
so that another deerhound had to be employed." 

Similarly, Finn records, in the Country-Side 
for August 29th, 1908, that the male Globose 
Curassow {Crax globicerd) in the London Zoo- 
logical Gardens, which bred with the female 
Heck's Curassow (C hecki), as related on p. 104, 
selected the hen of this very distinctly coloured 
form or species in preference to any of the 
typical hens of his own kind. 

The cases on record of cocks being in a position 
to select their mates are comparatively rare, while 
instances of selection on the part of the hens are far 
more numerous. 

Hence it would seem that the sex, which is in 
a minority, and so has the opportunity of select- 


Male Attractiveness 

ing a mate, does exert a choice and prefer one 
particular individual ; and that, for the reasons 
pointed out by Darwin, it is in most cases the 
female who is in the position of being able to 
pick and choose her mate. It is, as Darwin 
truly said, far more difficult to decide what 
qualities determine the choice of the female. 
He believed that it is **to a large extent the 
external attractions of the male, though no doubt 
his vigour, courage, and other mental qualities 
come into play." 

Darwin argued that it is the love of hen birds 
for ''external attractions" in cock birds that 
has brought into being all the wonderful plumes 
that characterise such birds as the peacock. 
*' Many female progenitors of the peacock," he 
writes, on page 66 1 of The Descent of Man 
(ed. 1 901), *' during a long line of descent, have 
appreciated this superiority, for they have un- 
consciously, by the continued preference of the 
most beautiful males, rendered the peacock the 
most splendid of living birds." 

This conclusion has been vigorously attacked. 
It is argued, with some show of reason, that it 
is absurd to credit birds with aesthetic tastes 
equal, if not superior, to those of the most 
refined and civilised of human beings. 

Is it likely, it is asked, that a bird, which will 
nest in an old shoe cast off by a tramp, can 
appreciate beauty of plumage ? 
u 305 

The Making of Species 

As Geddes and Thomson say (page 29 of 
The Evolution of Sex), '' When we consider the 
complexity of the markings of the male bird or 
insect, and the slow gradations from one step of 
perfection to another, it seems difficult to credit 
birds or butterflies with a degree of aesthetic 
development exhibited by no human being with- 
out special aesthetic acuteness and special train- 
ing. Moreover, the butterfly, which is supposed 
to possess this extraordinary development of 
psychological subtlety, will fly naively to a piece 
of white paper on the ground, and is attracted 
by the primary aesthetic stimulus of an old- 
fashioned wall-paper, not to speak of the gaudy 
and monotonous brightness of some of our garden 
flowers. Thus we have the further difficulty, 
that we must suppose the female butterfly to 
have a double standard of taste, one for the 
flowers which she and her mate both visit, the 
other for the far more complex colourings and 
markings of the males. And even among birds, 
if we take those unmistakable hints of real 
awakening of the aesthetic sense which are 
exhibited by the Australian bower-bird or by 
the common jackdaw in its fondness for bright 
objects, how very rude is his taste compared 
with the critical examination of infinitesimal 
variations of plumage on which Darwin relies. 
Is not, therefore, his essential supposition too 
glaringly anthropomorphic ? 


Male Attractiveness 

" Again, the most beautiful males are often 
extremely combative ; and on the conventional 
view this is a mere coincidence, yet a most 
unfortunate one for Mr Darwin's view. Battle 
thus constantly decides the question of pairing, 
and in cases where, by hypothesis, the female 
should have most choice, she has simply to yield 
to the victor." 

Darwin, with characteristic fairness, quotes 
some instances which appear to be opposed to 
the theory that the hen selects the most beauti- 
ful of her suitors. He informs us that Messrs 
Hewitt, Tegetmeier, and Brent, who have all 
had a long experience of domesticated birds, 
** do not believe that the females prefer certain 
males on account of the beauty of their plumage. 
. . . Mr Tegetmeier is convinced that a game- 
cock, though disfigured by being dubbed and 
with his hackles trimmed, would be accepted as 
readily as a male retaining all his natural orna- 
ments. Mr Brent, however, admits that the 
beauty of the male probably aids in exciting the 
female ; and her acquiescence is necessary. Mr 
Hewitt is convinced that the union is by no 
means left to mere chance, for the female almost 
invariably prefers the most vigorous, defiant, and 
mettlesome male " ; and, in consequence, when 
there is a game-cock in the farmyard, the hens 
will all resort to him in preference to the cock 
of their own breed. Darwin thinks that "some 


The Making of Species 

allowance must be made for the artificial state in 
which these birds have long been kept," and 
cites in his favour the case of Mr Cupples' female 
deerhound that thrice produced puppies, and on 
each occasion showed a marked preference for 
one of the largest and handsomest, but not the 
most eager, of four deerhounds living with her, 
all in the prime of life. 

The question what is it that determines the 
choice of the female is obviously one of con- 
siderable importance, and it was to be expected 
that many zoologists would have conducted 
experiments with a view to deciding it. This 
legitimate expectation has not been realised. 

The matter of sexual selection remains to-day 
practically where Darwin left it. Wallace rejects 
the whole theory, and believes that natural 
selection alone can explain all the phenomena of 
sexual dimorphism. To such an extent does the 
enticing idea of the all-puissance of natural 
selection dominate the minds of scientific men 
that but few of them have paid any attention to 
the question of sexual selection. This neglect 
of the subject affords an example of the baneful 
results of the too-ready acceptance of an enticing 
theory, " Natural selection explains everything, 
why then investigate further ? " seems to be the 
general attitude of our present-day naturalists. 

Edmund Selous and D. Dewar have made 
some observations on birds, and the Peckhams 



Pearson's Investigations 

on spiders, in a state of nature. Such observa- 
tions demonstrate that selective mating occurs 
in nature, but, for the most part, fail to show what 
it is that determines the choice. 

D. Dewar, however, states i^Birds of the Plains, 
p. 42) that the coloured peahens in the Zoo- 
logical Gardens at Lahore show a decided pre- 
ference for the white cocks, which are kept in 
the aviary along with normally coloured cocks. 
He gives it as his opinion that "the hens select 
the white cocks, not because they are white, but 
because of the strength of the sexual instincts of 
these latter. The white cocks continually show 
off before the hens ; the sexual desire is developed 
more highly in them than in the ordinary cocks, ^''"^v? \ 
and it is this that attracts the hens." r^N"^^ J 

The only zoologists who have investigated 
experimentally 'the question of sexual selection 
appear to be Karl Pearson and Frank Finn. 
The former tried to determine, by actual measure- 
ments, whether there is any preferential mating 
among human beings as regards physical char- 
acteristics. '' Our statistics," he writes, on page 
427 of The Grammar of Science, "run to only 
a few hundreds, and were not collected ad hoc. 
Still, as far as they go, they show no evi- 
dence of preferential mating in mankind on 
the basis of stature, or of any character very 
closely correlated with stature. Men do not 
appear, for example, to select tall women for 



The Making of Species 

their wives, nor do they refuse to mate with 
very tall or very short women." As regards 
eye-colour, Pearson seems to have arrived at 
somewhat more definite results. " We con- 
clude," he writes (p. 428), ''that in mankind 
there certainly exists a preferential mating in the 
matter of eye-colour, or of some closely allied 
character in the male ; in the case of the female 
there also appears to be some change of type due 
to preferential mating. . . . The general tendency 
is for lighter-eyed to mate, the darker-eyed being 
relatively less frequently mated." 

But Pearson's experiments seem to show that 
as regards stature and eye-colour there is "a 
quite sensible tendency of like to mate with 
like." '* In fact," writes Pearson, ''husband and 
wife for one of these characters are more alike 
than uncle and niece, and for the other more 
alike than first cousins." He adds, " Such a 
degree of resemblance in two mates, which we 
reasonably assume to be not peculiar to man, 
could not fail to be of weight if all the stages 
between like and unlike were destroyed by 
differential selection." 

Two obvious criticisms of the results obtained 
by Prof. Pearson occur to us. The first is that 
his conclusions do not seem to be in accordance 
with the popular notion that fair-haired men 
prefer dark hair in a woman, while dark-haired 
men prefer fair-haired women, and vice versa. 


Finn's Experiments 

The second is that the human animal is not a 
typical one. Husbands and wives are selected 
for mental and moral qualities rather than 
physical ones. The same may, of course, be to 
some extent true of animals, but in these there 
must of necessity be far less variation as regards 
mental attributes. Moreover, the question of 
income is much bound up with human matrimonial 
alliances ; a rich man or woman has the same 
advantage in selection as is possessed by an 
animal endowed with more than the average 
physical strength of its species. 

Finn adopted the plan of experiment suggested 
by Prof Moseley. His apparatus consisted of a 
cage divided into three compartments by wire 
partitions, so that a bird living in one of them 
could see its neighbour in the next compartment. 
In the middle compartment he placed a hen 
Amadavat (Sporceginthus amandava\ and in each 
of the other compartments he put a cock bird. 
Under such circumstances, the hen in the middle 
compartment will sit and roost beside the cock 
she prefers. The male amadavat, he writes, in 
The Country-Side, vol. i. p. 142, ''is in breeding 
plumage red with white spots, and the hen brown. 
The red varies in intensity even in full-plumaged 
birds, and I submitted to the hen first of all two 
male birds, one of a coppery and the other of a 
rich scarlet tint. In no long time she had made 
her choice of the latter bird ; the other, I am sorry 


The Making of Species 

to say, very soon died ; and, as he had appeared 
perfecdy healthy, I fear grief was accountable 
for his end — a warning to future experimenters 
to remove the rejected suitor as early as 
possible. In the present case I took away the 
favoured bird, and put in the side compartments 
he and his rival had occupied two other cocks, 
which differed in a similar way, though not to 
the same extent. Again the hen kept at the 
side of the rich red specimen, so, deeming I 
knew her views about the correct colour for an 
amadavat, I took her away too, and tried a 
second hen with these two males. This was an 
unusually big bird, and a very independent one, 
for she would not make up her mind at all, and 
ultimately I released all three without having 
gained any result. 

Subsequently I made another experiment with 
linnets. In this case all three were allowed to 
fly in a big aviary-cage together, a method which 
I do not recommend. 

In this case, however, the handsomest cock, 
which showed much richer red on the breast, had 
a crippled foot, and proved, as I had expected, 
to be in fear of the other ; nevertheless, the hen 
mated with him. It must be said, in justice to 
the duller bird, that he did not press the advan- 
tage his soundness gave him, but with a less 
gentle bird than the linnet this would have 


Finn's Experiments 

It is obvious that there is a wide field for 
observation on these lines. In the case of large 
birds the experiment could be made still more 
conclusive by confining the three birds to be 
experimented on in a single enclosure, divided 
into three compartments by fences. The males 
should be placed each in a separate compartment, 
and have a wing clipped so as to prevent them 
leaving their respective compartments, while the 
hen should be allowed the power of flight so that 
she can visit at will any compartment. 

Finn has also recorded {loc. cit.) some other 
observations bearing on the question of sexual 
selection. He writes: — 

'' One cannot observe or read about the habits 
of birds very much without finding out that, 
whatever may be the value of beauty, strength 
counts for a great deal. Male birds constantly 
fight for their mates, and the beaten individual, 
if not killed, is at any rate kept at a distance by 
his successful rival, so that, if he be really more 
beautiful, his beauty is not necessarily of much 
service to him. I was particularly impressed 
by this about a couple of years ago, when I 
frequently watched the semi-domesticated mal- 
lards in Regent's Park in the pairing season. 
These birds varied a good deal in colour ; in 
some the rich claret breast was wanting, and 
others had even a slate-coloured head instead of 
the normal brilliant green. Yet I found these 


The Making of Species 

* off-coloured ' birds could succeed in getting and 
keeping mates when correctly-dressed drakes 
pined in lonely bachelorhood ; one grey-breasted 
bird had even been able to indulge in bigamy. 
That strength ruled here was obvious from the 
way in which the wedded birds drove away their 
unmated rivals, a proceeding in which their wives 
most thoroughly sympathised. 

*' Evidently, beauty does not count for much 
with the park duck, and the same seems to be the 
case with the fowl. As a boy, I often used to 
visit a yard wherein was a very varied assort- 
ment of fowls. Among these was one very 
handsome cock, of the typical black and red 
colouring of the wild bird, and very fully 

* furnished ' in the matter of hackle and sickle 
feathers. Yet the hens held him in no great 
account, while the master of the yard, a big 
black bird, with much Spanish blood, provided 
with a huge pair of spurs, was so admired that 
he was always attended by some little bantam 
hens, although they might have had diminutive 
husbands of their own class. 

*' It must be remembered, however, that these 
ducks and fowls had an unnaturally wide choice. 
In nature, varieties are rare, and the competing 
suitors are likely to be all very much alike ; this 
makes matters very difficult for the observer, 
who may easily pass over small differences which 
are plain enough to the eyes of the hen birds." 


Display of Undecorated Cocks 

Finn observed that a young hen Bird of 
Paradise [Paradisea apodd) in the London Zoo- 
logical Gardens, mated with a fully adult cock in 
the next compartment although a young cock in 
female plumage in her own compartment did his 
best to show off. 

It would thus seem that the very limited 
evidence at present available is not sufficient to 
sustain the theory that the hens select the most 
attractive of their suitors. It is significant that 
plainly-coloured species of birds show off with as 
much care as their gaily-plumaged brethren ; 
and, if they be nearly allied, assume similar 
courting attitudes. Thus the homely-attired 
males of the Spotted-bill [Anas poecilorhynckdj, 
Gadwall, and Black Duck {Anas superciliosd)^ 
show off in precisely the same way as does the 
handsome mallard. 

Howard describes and figures in his excellent 
and beautifully illustrated monograph the elabo- 
rate display at the pairing season of some of our 
plain-coloured little warblers. The skylark has 
also a notable display. 

The common partridge assumes a nuptial atti- 
tude similar to that of the pheasant, and, although 
the cock of the former species has nothing brilliant 
to show off, the hen partridge pays far more atten- 
tion to the display of her suitor than does the hen 

The fact that some cock birds show off after the 


The Making of Species 

act of pairing seems to tell against the theory of 
sexual selection, or at any rate to indicate the 
purely mechanical nature of the performance. 
Finn has witnessed this post-nuptial display 
at the Zoological Gardens (London) in the 
pied wagtail, the peacock, the Andaman Teal 
{Nettium albigulare), the Avocet, the Egyptian 
Goose {Chenatopex cEgyptiaca), and the Maned 
Goose (Chenonetta jubata). 

Another objection to the theory that the bright 
colours of cock birds are due to feminine selection 
is presented by those birds which breed in im- 
mature plumage. Darwin admits that this objec- 
tion would be a valid one ''if the younger and 
less ornamental males were as successful in 
winning females and propagating their kind as 
the older and more beautiful males. But," he 
continues, " we have no reason to suppose that 
this is the case." 

Unfortunately for the theory of sexual selection, 
there is evidence to show that the cock Paradise 
Fly-catcher ( Terpsiphone paradist) in immature 
plumage is quite as successful in obtaining a 
mate as is the cock in his final plumage. The 
cock of this beautiful species has a chestnut 
plumage in his second year, and a white one 
in the third and subsequent years of his life. 
Nevertheless, a considerable proportion of the 
nests found belong to chestnut cocks. 

Darwin was of opinion that any novelty in 



Plumage of Herons 

colouring in the male is admired by the female ; 
and in this manner he sought to overcome some 
difficulties to his theory which certain birds 

Writing of the heron family, he says : — 
*'The young of the Ardea as ha are white, the 
adults being slate-coloured ; and not only the 
young, but the adults of the allied Buphus 
coromandus in their winter plumage are white, 
their colour changing into a rich golden buff 
during the breeding season. It is incredible 
that the young of these two species, as well as 
of some other members of the same family, 
should have been specially rendered pure white, 
and thus made conspicuous to their enemies ; or 
that the adults of one of these two species should 
have been specially rendered white during the 
winter in a country which is never covered with 
snow. On the other hand, we have reason to 
believe that whiteness has been gained by many 
birds as a sexual ornament. We may therefore 
conclude that an early progenitor of the Ardea 
asha and the Buphus acquired a white plumage 
for nuptial purposes, and transmitted this colour 
to their young ; so that the young and the old 
became white like certain existing egrets, the 
whiteness having afterwards been retained by 
the young whilst exchanged by the adults for 
more strongly pronounced tints. But if we 
could look still further backwards in time to 


The Making of Species 

the still earlier progenitors of these two species, 
we should probably see the adults dark-coloured. 
I infer that this would be the case, from the 
analogy of many other birds, which are dark 
whilst young, and when adult are white ; and 
more especially from the adult of the Ardea 
gulariSy the colours of which are the reverse 
of those of A. asha, for the young are dark- 
coloured and the adults white, the young having 
retained a former state of plumage. It appears, 
therefore, that the progenitors in their adult con- 
dition of the A. as ha, the Buphus, and of some 
allies have undergone, during a long line of 
descent, the following changes of colour : firstly 
a dark shade, secondly pure white, and thirdly, 
owing to another change of fashion (if I may so 
express myself), their present slaty, reddish or 
golden-buff tints. These successive changes are 
intelligible only on the principle of novelty 
having been admired by the birds for the sake 
of novelty." 

This reasoning may appear far-fetched and un- 
convincing. It seems, however, quite likely that 
the hen may select as her mate the suitor who 
is conspicuously different from the others, not 
because she admires novelty, but because his 
conspicuousness attracts her attention and en- 
ables her to make up her mind quickly to take 
him and thus rid herself of the other troublesome 
admirers, who are all very much alike. 

Sexual Dissimilarity 

It is perhaps worthy of note that, after the 
most successful of her suitors has succeeded in 
securing the hen, it may happen that a dis- 
appointed rival makes love to her in the absence 
of her lord and master and thereby nullifies the 
effect of her previous selection. 

It is to be observed that, even if we take it as 
proved, as Darwin believed, that the hens alone 
exercise a choice of mates, and that they select 
the most beautiful of their suitors, we are still 
far from arriving at an explanation of the fact 
that the males alone have acquired beauty. 
Admitting that the hens always mate with the 
most beautiful cocks, we should expect the off- 
spring of each union to be all more or less alike 
in beauty — that is to say, more beautiful than the 
mother and less so than the cock. How are we 
to explain the one-sided inheritance of this 
beauty ? Why is it confined to the cocks ? 

In order to meet this objection Darwin had to 
call to his aid unknown laws of inheritance. 
" The laws of inheritance," he writes {^Descent of 
Man, p. 759), " irrespectively of selection, appear 
to have determined whether the characters 
acquired by males for the sake of ornament, for 
producing various sounds, and for fighting 
together, have been transmitted to the males 
alone or to both sexes, either permanently or 
periodically, during certain seasons of the year. 
Why various characters should have been trans- 


The Making of Species 

mitted sometimes in one way and sometimes in 
another is not in most cases known ; but the 
period of variabiHty seems often to have been 
the determining cause. When the two sexes 
have inherited all characters in common, they 
necessarily resemble each other ; but, as the suc- 
cessive variations may be differently transmitted, 
every possible gradation may be found, even 
within the same genus, from the closest simi- 
larity to the widest dissimilarity between the 

This statement, although it does not throw any 
light upon the problem, is somewhat damaging 
to the theory of sexual selection. If it be 
admitted that dissimilarity between the sexes 
is due to the fact that the males have varied in 
one way and the females in another way, there 
seems no necessity for invoking the aid of 
feminine preference. 

Even greater is the difficulty presented by 
those species in which the males alone are pro- 
vided with horns or antlers. ''When," writes 
Darwin {^Descent of Man, p. 767), ''the males 
are provided with weapons which in the females 
are absent, there can hardly be a doubt that 
these serve for fighting with other males ; and 
that they were acquired through sexual selection, 
and were transmitted to the male sex alone. 
It is not probable, at least in most cases, that 
the females have been prevented from acquiring 


Wallace's Theory 

such weapons on account of their being useless, 
superfluous, or in some way injurious. On the 
contrary, as they are often used by the males for 
various purposes, more especially as a defence 
against their enemies, it is a surprising fact that 
they are so poorly developed, or quite absent, 
in the females of so many animals." 

We have, we believe, demonstrated that 
Darwin's theory of sexual selection is unable to 
account satisfactorily for all the phenomena of 
sexual dimorphism. But, as we have seen, it is 
quite possible that sexual selection is a real 
factor of evolution. 

We trust that what we have said will stimu- 
late some leisured naturalist to study the question 
of male and female preference. 

We now pass on to consider briefly some of 
the other attempts that have been made to ex- 
plain the phenomena of sexual dimorphism. 

Wallace's Explanation of Sexual 

Wallace does not accept the theory of sexual 
selection. He admits that the form of male 
rivalry, which Darwin calls '* the law of battle," 
is '*a real power in nature," and believes that 
** to it we must impute the development of the 
exceptional strength, size, and activity of the 
male, together with the possession of special 
offensive and defensive weapons, and of all 
X 321 

The Making of Species 

other characters which arise from the develop- 
ment of these, or are correlated with them " 
[Darwinism J p. 283). But the view that the 
female selects the most beautiful of her suitors 
has always seemed to Wallace ''to be un- 
supported by evidence, while it is also quite 
inadequate to account for the facts." For 
example, the accessory plumes of birds " usually 
appear in a few definite parts of the body. We 
require some cause to initiate the development in 
one part rather than in another." 

Wallace considers that natural selection is 
able to explain all the phenomena of sexual 
dimorphism. He points out that, when the sexes 
are dissimilar among birds, it is almost invariably 
the female which is duller coloured. The reason 
for this is, he believes, that the hen birds, while 
sitting, **are exposed to observation and attack 
by the numerous devourers of eggs and birds, 
and it is of vital importance that they should be 
protectively coloured in all those parts of the 
body which are exposed during incubation. To 
secure this, all the bright colours and showy 
ornaments which decorate the male have not 
been acquired by the female, who often remains 
clothed in the sober hues which were probably 
once common to the whole order to which she 
belongs. The different amounts of colour ac- 
quired by, the females have no doubt depended 
on peculiarities of habits and environment, and on 


Wallace's Theory 

the powers of defence and concealment possessed 
by the species." 

In support of his contention, Wallace asserts 
that all species of birds, of which the hens are as 
conspicuously coloured as the cocks, nest in holes 
or build domed nests. The plumes and other 
ornaments, which the cocks of certain species 
display, Wallace would attribute to a surplus of 
strength, vitality, and growth power, which is 
able to expend itself in this way without injury. 

"If," he writes, ''we have found a vera causa 
for the origin of ornamental appendages of birds 
and other animals in a surplus of vital energy, 
leading to abnormal growths in those parts of 
the integument where muscular and nervous 
action are greatest, the continuous development 
of these appendages will result from the ordinary 
action of natural selection in preserving the most 
healthy and vigorous individuals, and the still 
further selective agency of sexual struggle in 
giving to the very strongest and most energetic 
the parentage of the next generation." {^Dar- 
winism, p. 293.) ''Why," he says, "in allied 
species the development of accessory plumes 
has taken different forms we are unable to say, 
except that it may be due to that individual 
variability which has served as the starting point 
for so much of what seems to us strange in form, 
or fantastic in colour, both in the animal and 
vegetable world." 


The Making of Species 

Wallace's view that the dull plumage of the 
hen bird is due to her greater need of protection 
is based on the assumption that the hen bird alone 
takes part in incubation. 

Is this assumption a correct one ? 
It certainly is not in all cases. As D. Dewar 
has stated in Birds of the Plains, the showy 
white cock Paradise Fly-catcher {Terpsiphone 
paradisi) sits in broad daylight on the open nest 
quite as much as the hen does. And this may 
prove to be true of many other species of 
birds. Again, the cocks of the various species 
of Indian sunbirds are brightly coloured while 
the hens are dull brown. In these species the 
hen alone sits on the eggs, but, as the nest is 
well covered-in, the hen might display all the 
colours of the rainbow without being visible 
to passing birds. Moreover, as D. Dewar 
pointed out in a paper read before the Royal 
Society of Arts [Journal, vol. Ivii., p. 104), 
although, in most species of Indian dove, the 
sexes show little or no dissimilarity, there is one 
species (CEnopopelia tranguebarica) which ex- 
hibits considerable sexual dimorphism. But the 
nesting habits of this peculiar species are in 
all respects similar to those of the other species 
of dove. Why then the marked dissimilarity of 
the sexes ? 

Another objection to the theory of W^allace is 
that urged by J. T. Cunningham {Arckiv fur 


Wallace's Theory Criticised 

EntwicklMugsmechanik der Organismen^ vol. 
xxvi., p. Zl"^)^ namely, that the secondary- 
sexual characters in those species which possess 
them show an entire absence of uniformity in 
nature and position. '' Why," asks Cunningham, 
''should the male constitution of the stag show 
itself in bony excrescences of the skull, in the 
peacock in excessive growth of the other end of 
the body ? Why should the larynx be modified 
in one mammal, the teeth in another, the nose in 
another? Why is the male newt distinguished 
by a dorsal fin, the male frog by a swelling on 
the fore foot ? " 

Another objection to the explanation of sexual 
dimorphism suggested by Wallace, is that in 
many species of bird, as, for example, the house 
sparrow and the green paroquets of India, the 
external differences between the sexes are so 
slight that it is unreasonable to believe that they 
are the result of natural selection. It seems 
impossible to hold that the Rose-ringed Paroquet 
{Palaeornis torquatus) — a species which nests in 
holes — would have become extinct if the hens had 
developed the narrow rose-coloured collar that 
characterises the cocks. 

Darwin pointed out that while Wallaces 
hypothesis might appear plausible if applied to 
colour, it can scarcely be said to explain the 
origin of such structures as the musical apparatus 
of certain male insects, or the larger size of the 


The Making of Species 

larynx in some birds and mammals. We thus see 
that suggestions offered by Wallace, although 
they contain a modicum of truth, fail to explain 
the phenomena of sexual dimorphism. 

The fairest possible criticism of these views is 
that of Darwin : — 

** It will have been seen that I cannot follow 
Mr Wallace in the belief that dull colours, when 
confined to the females, have been in most cases 
specially gained for the sake of protection. 
There can, however, be no doubt, as formerly 
remarked, that both sexes of many birds have 
had their colours modified, so as to escape the 
notice of their enemies ; or in some instances, so 
as to approach their prey unobserved, just as 
owls have had their plumage rendered soft, that 
their flight may not be overheard" {The Descent 
of Man, p. 745). 

The Theory of Thomson and Geddes 

Thomson and Geddes have attempted to 
explain sexual dimorphism on the hypothesis 
that males are essentially dissipators of energy, 
while females tend to conserve energy. They 
point out that the spermatozoon is a small 
intensely active body, which dissipates its energy 
in motion, while the ovum is a large inert body 
— the result of the female tendency to conserve 
energy and to build up material. The various 
ornaments and excrescences which appear in 


Views of Thomson and Geddes 

male organisms are the result of this male ten- 
dency to dissipate energy. In the spermatozoon 
the dissipated energy appears in the form of 
active movement ; in the adult organism it takes 
the shape of plumes and other ornaments, of song 
and contests for the females. 

This theory, however, does not explain what 
we might call the haphazard nature of sexual 
dimorphism. If sexual dissimilarity is due to the 
tendency of the male to dissipate energy, why do 
we see very marked dimorphism in one species, 
and no dimorphism in a very nearly allied 
species .-^ Why are the males larger than the 
females in some species, and smaller in other 
species ? Again, how is it that in certain species 
of birds — the quails of the genus Turnix, the 
Painted Snipe (Rhynchcea), and the Phalaropes — 
it is the female who possesses the more showy 
plumage ? Moreover, this theory, equally with 
that of Wallace, does not explain why the ex- 
crescences which characterise the male appear in 
various parts of the body in different species. 

Stolzmann's Theory 

Stolzmann has made an ingenious attempt to 
explain why in birds the cock is so frequently 
more conspicuously coloured than the hen. He 
asserts that among birds the males are more 
numerous than the females, and that this pre- 
ponderance is not advantageous to the species. 


The Making of Species 

Those males which have not managed to secure 
a mate are apt to persecute the females while 
sitting on the eggs, to the detriment of these 
latter. Natural selection, says Stolzmann, is 
concerned with the well-being of the species 
rather than of the individual. Hence anything 
that would tend to lessen the number of males 
would be a good thing for the species, so that 
a peculiarity, such as bright plumage, which 
renders the males conspicuous, or ornamental 
plumes, which cause their flight to be slow, and 
so leads to their destruction, will be seized upon 
and perpetuated by natural selection. He points 
out that the cock of one species of humming- 
bird — Loddigesia mirabilis — has not only longer 
tail feathers, but a shorter wing than the female, 
and must, in consequence, find it comparatively 
difficult to obtain food, and be more liable to fall 
a victim to birds of prey than the hen. Stolz- 
mann further suggests that the excessive pug- 
nacity of male birds at the breeding season may 
lead to the destruction of some individuals, and 
so prove of advantage to the species. 

Several objections seem to present themselves 
to this most ingenious theory. 

In the first place, there does not appear to 
be any satisfactory evidence to show that more 
cocks than hens are born. 

We may grant that a superfluity of cocks is 
injurious to any species, since the unmated ones 


Stolzmann's Theory 

are likely to persecute the hens ; we may also 
grant that many cocks are handicapped in the 
struggle for existence by the excessive growth 
of certain of their feathers, but we fail to see 
how this excessive development has been caused 
by natural selection in the manner suggested by 
Stolzmann. Although it may be advantageous 
to the species for the cocks to be showy, natural 
selection can perpetuate this only by weeding 
out the least conspicuous of the cocks. But it 
is the more gaudy ones, those, according to 
Stolzmann, whose presence is beneficial to the 
species, which will be eliminated by natural 
selection. So that, in this case, that force will 
act in a manner contrary to the interests of the 
species, if Stolzmann's idea is a correct one. 

The theory in question would therefore seem 
to be untenable. Nevertheless there is doubt- 
less some truth in the notion that too many 
males spoil the species. Thus, excessive showi- 
ness and high mortality among the males may 
be beneficial to the species. But we must not 
forget that the more beneficial it is, the stronger 
must be the tendency of natural selection to 
eliminate the males that possess the desired 

Neo-Lamarckian Explanation 

J. T. Cunningham makes an attempt to ex- 
plain the phenomena of sexual dimorphism on 


The Making of Species 

Neo-Lamarckian principles. His theory is set 
forth in a paper entitled The Heredity of 
Secondary Sexual Characters in relation to 
Hormones, which was read before the Zoological 
Society of London, and published in full in the 
Archiv filr Entwicklungsmechanik der Organ- 
ismen. '* The significant correlation of male 
sexual characters," he writes, " is not with any 
general or essential property of the male sex, 
such as katabolism (or the tendency to dissipate 
energy, as we have called it), but with certain 
habits and functions confined to one sex, but 
differing in different animals. ... In those 
animals which possess such {i.e. secondary 
sexual) characters, the parts of the soma {i.e. the 
body) affected differ as much as they can differ ; 
any part of the soma may show a sexual differ- 
ence : teeth in one mammal, skull in another ; 
feathers of the tail in one bird, those of the neck 
in another, and so on. But in all cases such 
unisexual characters correspond to their functions 
or use in habits and instincts which are asso- 
ciated, but only indirectly, with sexual produc- 
tion. These habits are as diverse and as 
irregular in their distribution as the characters. 
The cocks of common fowls and of the Phasi- 
anidae generally are polygamous, fight with each 
other for the possession of the females, and take 
no part in incubation or care of the young, and 
they differ from the hens in their enlarged 


Cunningham's Theory 

brilliant plumage, spurs on the legs, and combs, 
wattles, or other excrescences on the head. In 
the Columbidse per contra the males are not 
polygamous, but pair for life, the males do not 
fight, and share equally with the females in 
parental duties. 

" Corresponding with this contrast of sexual 
habits is the contrast of sexual dimorphism, 
which is virtually absent in the Columbidse. 

*' I think, then, the only scientific explanation 
is that the difference of habits is the cause of 
the sexual dimorphism, and that the special 
sexual habits which occur in some species but 
not in others are the causes of the sexual char- 
acters. . . . The habits in question always involve 
certain definite stimulations applied to those parts 
of the body whose modification constitutes the 
somatic sexual characters. The stimulations are 
confined, as the characters are confined, to one 
sex, to one period of life, to one season of the 
year, to those animals which have the characters, 
to those parts of the body which are modified." 
Mr Cunningham believes that these stimulations 
cause hypertrophy or excessive growth of the 
part affected, and that this peculiarity is trans- 
mitted to the offspring. And thus he supposes 
all the ornaments and excrescences of the males 
of various species to have arisen. 

As evidence in favour of his view, he points 
out that these excrescences are, in many species, 


The Making of Species 

not only functlonless but absolutely injurious, as 
in the case of the comb and wattles of the jungle 
cock and his domestic descendants, which merely 
serve as a handle for enemies to seize. 

Cunningham asserts that the only objection to 
his theory is the dogma that acquired characters 
cannot be inherited. This assertion is, however, 
not correct. It is, indeed, a very serious objection 
that all the evidence available seems to show that 
acquired characters are not inherited, but this is 
by no means the only difficulty. 

Before mentioning these further objections, let 
us say a word on the subject of the inheritance 
of acquired characters. Mr Cunningham himself 
compares the formation of a splint or spavin 
in a horse as the result of special strain, to 
the acquisition of secondary sexual characters. 
Unfortunately for Cunningham's theory, but 
fortunately for mankind in general, spavined 
horses and mares do not beget spavined off- 
spring. If, then, spavin is not inherited, is it 
not unreasonable to assert that the thickening 
of the bone that develops on the head of a 
butting animal is inherited? 

Another objection to Cunningham's theory is 
that many birds which show off their plumage 
most vigorously possess no ornamental plumes. 
As Howard has recorded, many of our dull- 
coloured British warblers show off in the same 
manner as bright-coloured birds do. If the 


Existing Theories not Satisfactory 

exercise has caused the development and in- 
heritance of plumes in some species, why not 
in the others ? 

Again, Cunningham is not correct in saying 
that sexual dimorphism is " virtually absent " in 
the Columbidse. Few birds display so striking a 
sexual dimorphism as the Orange Dove {Chryscena 
victor) of Fiji, in which the male is bright orange 
and the hen green. We have already cited the 
case of the curious sexually dimorphic red turtle- 
dove. Now, the courting attitudes and actions 
of this species are precisely the same as those of 
other allied turtle-doves ; why, then, have these 
exercises caused only one species to become 
sexually dimorphic ? 

Our survey of the more important attempts 
which have been made to explain the phenomena 
of sexual dimorphism leads to the conclusion that 
these still require elucidation. We have weighed 
each theory in the balance and found it wanting. 

The outstanding feature of sexual dissimilarity 
is the apparently haphazard manner of its occur- 

We have already alluded to the case of the 
doves in India. In that country four species are 
widely distributed — namely, the Spotted Dove 
{Turtur suratensis), the Ring or Collared Dove 
( Turtur risorius), the Little Brown Dove ( Ttirtur 
cambayensis\2sA. the Red Turtle-dove ((E'/^^/i?/^//^ 


The Making of Species 

tranqebarica). The habits of all these four 
species appear to be identical, nevertheless in 
the first three the sexes show little or no dis- 
similarity in outward appearance, while in the 
last the sexual dimorphism is so great that the 
cock and hen were formerly thought to belong to 
different species. 

Another very curious case is that of the South 
American geese of the genus Chloephaga, in 
which some species, as the familiar Upland or 
Magellan Goose of our parks (C. magellanicd), 
have the sexes utterly unlike, while in others, as 
the Ruddy-headed Goose (C rubidiceps), they are 
quite similar to each other. 

The ducks furnish us with another very good 
example of the apparently haphazard nature of 
sexual dimorphism. In the Common Mallard or 
Wild Duck {Anas boscas) the cock is far more 
showily coloured than the hen, but in all the 
species most nearly allied to it the males are as 
inconspicuous as the females, e.g. in the Indian 
Spotted-bill {Anas pceczlorhyncka), the Australian 
Grey Duck {A. superciliosa), the African Yellow 
Bill {Anas undtdata\ and the American Dusky 
Duck {A. obscura). As the dusky duck inhabits 
North America, where the mallard is also found, 
the case is particularly striking. 

Among mammals the lion and the tiger and the 
sable and roan antelopes {Hippotragus niger and 
H. equinus) furnish familiar examples of nearly- 



related species, in one of which the sexes are 
ahke and in the other dissimilar in appearance. 

Another important point to be borne in mind 
is the intimate correlation that exists between the 
reproductive organs and the general appearance 
of the organism, more especially of the secondary- 
sexual characters. These last, in most cases, do 
not show themselves until the maturity of the 
sexual organs. The well-known effects of castra- 
tion illustrate this connection. Again, females in 
which the reproductive organs have ceased to be 
functional often assume male characters. 

It has lately been proved by experiment that, 
in many cases at any rate, the development of 
the ornaments, etc., characteristic of the sexes 
is due to the secretion by the sexual cells of 
what are known as hormones — that is to say, 
secretions which excite development of the 
secondary sexual characters. The tendency to 
produce the external characteristics of the sex 
to which an organism belongs is inherited, but 
the actual development thereof is in many cases 
dependent on the secretion of these hormones. 
Accordingly, if a male individual be completely 
castrated it ceases to develop the external 
characters of its sex. The evidence upon which 
the doctrine of hormones is based is admirably 
summarised in the above - quoted paper by 
Cunningham. Into this evidence we cannot 
go. It must suffice that the doctrine is quite 


The Making of Species 

in accordance with all the observed results of 

It is worthy of notice that the various features 
which characterise the sexes in sexually dimor- 
phic animals are not associated with any par- 
ticular organ or parts of the body, nor do they 
necessarily affect the same part in allied species. 
** We cannot say," writes J. T. Cunningham, 
" that any part of the soma {i.e. the body tissue) is 
specially sexual more than another part, except 
that such differences between the sexes are 
usually external. They usually affect the skin, 
and especially epidermic appendages, and the 
superficial parts of the skeleton, or whole limbs 
and appendages ; or the difference may be one 
of size of the whole soma. In mammals and 
birds the male is often the larger, sometimes very 
much so, but there are cases in which the female 
is larger. There is no general rule." 

Another important point is, that females, 
although they themselves show no trace of the 
male character, are capable of transmitting it to 
their progeny. This can be proved by crossing 
a hen pheasant with a cock barn-door fowl ; the 
male offspring of the union display the plumes so 
characteristic of the cock pheasant. Theise can- 
not have been derived from the barn-door-fowl 
father ; they must have come from the dull- 
coloured hen pheasant. 

In this connection we may mention the curious 


Eye-colour, Comb, and Spurs 

fact recorded by Bonhote, on page 245 of the 
Proceedings of the Fourth International Ornitho- 
logical Congress, that in the case of ducks de- 
scended from crosses between the pintail, the 
mallard, and the spotbill, the drakes in full 
breeding plumage showed a mixture of pintail 
and mallard characteristics, while, in their non- 
breeding plumage, the colouring of the spotbill 
is predominant. 

An important point, and one which does not 
seem to have been pointed out by any zoologist, 
is that eye-colour, comb, and spurs in birds and 
horns in mammals do not stand in the same 
relation to the sexual organs as do the other 
external characteristics. For example, the cas- 
trated Nilgai {Boselaphus tragocamelus) acquires 
horns, but not the characteristic male colour. 
In the common Indian Francolin Partridge 
(Francolinus pondicerianius), the cock differs from 
the hen only in the possession of spurs. The 
same applies to the various species of Snow 
Cock ( Tetraogallus). There is a breed of game- 
cocks which display plumage like that of the 
hen, but such birds have the comb and spurs 
developed as in normally feathered cocks. 

The white eye of the white-eyed Pochard 
Drake {Nyroca africana), and the yellow eye of 
the cock Golden Pheasant (Chrysolophus pictus), 
which are purely male characters, show them- 
selves earlier than the male plumage. Occasion- 
Y 337 

The Making of Species 

ally a hen golden pheasant assumes the plumage 
of the cock, but she never acquires the yellow 

Many birds when kept in captivity lose some 
of the beauty of their plumage, and this is 
usually attributed to the sexual organs becoming 
impaired and reacting on the somatic tissue. 
But this explanation cannot in all cases be the 
correct one, because the linnet, although losing 
the male plumage in captivity, lives long and 
well in a cage and breeds readily with hen 

Another curious fact is that the male plumage 
sometimes appears pathologically in hen birds, 
more especially in those which have become sterile 
from age or disease. This phenomenon occurs 
comparatively frequently in the gold pheasant, 
and more rarely in the common pheasant, the 
fowl, and the duck. 

Phenomena such as these seem to suggest 
that in some cases the bright colours of the male 
may be pathological, that the hormones which 
the male sexual cells secrete may exercise an 
injurious effect on the somatic or body tissues. 
Decay is known to be accompanied by the 
production of brightly coloured pigment in the 
case of leaves. Finn suggests that the white 
plumage which the cock paradise fly -catcher 
assumes in the fourth year of his existence may 
be a livery of decay, a sign of senility. 


The Four Kinds of Mutations 

It is our belief that sexual dimorphism arises 
frequently, if not invariably, as a mutation. 
Mutations may be of four different kinds. 

Those which appear only, or especially, in con- 
junction with the male organs, for example, 
whiteness in domesticated geese allowed to 
breed indiscriminately. 

Those which appear only, or especially, in con- 
junction with the female organs ; mutations of 
this description appear to be very rare, but it 
may be noted that in fowls allowed to breed 
indiscriminately, as in India, completely black 
hens are common, but completely black cocks 
are rarely, if ever, seen. This indicates an 
association between blackness and femininity. 

Those which appear in the same manner in 
both sexes. The great majority of mutations 
appear to be of this kind. 

Lastly, those that appear in both sexes but 
take a different form in the case of the two 
sexes ; thus in cats a mutation has given rise 
to sandy males and tortoise-shell females. The 
mutation which has produced the black-winged 
peacock shows itself in the form of a black wing 
in the cock, while it causes the plumage of the 
hen to be grizzly white. 

We shall deal with the phenomenon of correla- 
tion at some length in the next chapter. It is a 
subject to which sufficient attention has not been 
paid. Even as certain characters are correlated 


The Making of Species 

in certain species, so in some cases are certain 
characters correlated with sex. 

Why this should be so we are not in a position 
to say ; this, however, does not affect the indis- 
putable fact that such correlation does exist. 

Physicians in the course of their practice 
sometimes come across very curious cases of 
correlation in human beings. 

*' It is," writes Thomson {Heredity, p. 290), 
"an interesting fact that an abnormal element in 
the inheritance may find expression in the males 
only or in the females only. If we could under- 
stand this we should be nearer understanding 
what sex really means. 

** Haemophilia, or a tendency to bleeding, is 
a heritable abnormality, partly associated with 
weakness in the blood-vessels, which do not 
contract as they should and are apt to break, 
and partly connected with a lack of coagulating 
power in the blood. It is usually confined to 
males. But as it passes from a father through a 
daughter to a grandson, and so on, it must be a 
latent part of the germinal inheritance of the 
females, though for some obscure physiological 
reason it fails to find expression in them, or has 
its expression quite disguised. Colour-blindness 
or Daltonism has been recorded (Horner) through 
the males only of seven generations. Dejerine 
cites another case {fide Appenzeller) in which all 
the males in a family history had cataract through 


Unilateral Transmission 

four generations. There are other instances of what 
is sometimes awkwardly called the unilateral trans- 
mission of abnormal qualities. Edward Lambert, 
born in 17 17, is said to have been covered with 
' spines.' His children showed the same 
peculiarity, which began to be manifest from 
the sixth to the ninth month after birth. One 
of his children grew up and handed on the 
peculiarity to another generation. Indeed, it is 
said to have persisted for five generations, and 
in the males only — unilateral transmission." 

In our view, these abnormalities are of such a 
kind that they are only possible in connection 
with the male organ ; in other words, they are 
mutations of the first of the four kinds cited 
above — those which appear only in connection 
with the male organ. 

It is a curious fact that the general rule in 
nature seems to be that the male is ahead of the 
female in the course of evolution. The sexes 
may be alike at a given period in the life-history 
of the species. Presently a mutation appears 
which is confined to the male alone ; thus arises 
the phenomenon of sexual dimorphism. The 
next step in the evolution of the species is 
frequently a mutation on the part of the female 
which brings her once again into line with the 
male, and so the sexual dimorphism disappears, 
for a time at any rate. A good example of this 
is furnished by the sparrows ; in the common 


The Making of Species 

sparrow of a large part of Africa (Passer 
swainsonz) both sexes are very plain, like the 
hen of the house-sparrow ; in this species {P. 
domesticus\ as every one knows, the cock, though 
by no means brilliant, is noticeably handsomer 
than his mate ; while in the Tree-sparrow {P. 
montanus) both sexes have a plumage of mascu- 
line type, much like that of the cock house- 

If we consider in conjunction with one another 
the various facts we have cited above, we begin 
to grasp the nature of the phenomena of sexual 

Let us consider an imaginary case of a defence- 
less little bird which builds an open nest. Let 
us suppose that it is inconspicuously plumaged. 
Now suppose that a mutation of the first kind 
shows itself, a mutation which affects the cock 
only and makes him more conspicuous. Let 
us further suppose that the cock does not 
share in the duties of incubation. It is quite 
possible that, in spite of this apparently unfavour- 
able mutation, the species may survive, for, as 
we have seen, it does not affect the hen, and 
she, since she alone incubates, stands the most 
in need of protective colouring. Moreover, as 
Stolzmann has suggested, the species can pos- 
sibly afford to lose a few males. But suppose 
that both cock and hen share in the duties of 
incubation, it is then quite likely that the muta- 


Greater Value of Females 

tion will cause the species to become extinct, 
by the elimination of all the males. Or, let us 
suppose that the mutation in the direction of 
showy plumage affects both sexes, then in such 
a case the species will almost certainly become 
extinct. If, however, the hypothetical species 
nested in holes in trees, it is quite possible that 
it might survive notwithstanding its showy 

Whether, as Wallace suggests, the hen does 
most of the incubating, and is exposed to special 
danger when sitting on her eggs in an open nest, 
or, as Stolzmann urges, it is of advantage to the 
species that there should not be too many males, 
the result is the same, that the species can afford 
to allow the cock to be more gaily attired than 
the hen. In either case the colouration of the 
cock becomes a matter of comparatively little 
importance to the species, and this, coupled with 
the fact that the male tends to mutate more 
readily than the female, will explain why, in 
most species which exhibit sexual dimorphism, 
it is the cocks that are the more conspicuous. 
In certain species the cocks alone incubate, and 
these then become more important than the 
females to the race, so that they have not been 
permitted to become showy, while the hens have 
been allowed more freedom in this respect. 
The extreme variability of the Ruff {Pavon- 
cella pugnax) in breeding plumage points to the 


The Making of Species 

fact that his colour is a matter of comparative 
indifference to the species; in consequence plenty 
of latitude is allowed to his tendency to vary. 

Our view, then, is that evolution proceeds by 
mutations, which may be large or small. 

The mutation is the result of a rearrangement 
in part or parts of the fertilised egg, and this re- 
arrangement shows itself in the adult organism as 
a change in one or more of its characteristics. 
The mutation may be correlated with only one 
of the sexual organs, and when this is the 
case, it gives rise to the phenomenon of sexual 
dimorphism. The appearance in the adult of 
certain, if not of all, characteristics is affected by 
causes other than the nature of the biological 
molecules from which they are derived. The 
tendency to develop in a certain direction is 
there, but something else, such as the secretion 
of hormones from the sexual cells, is frequently 
necessary to enable a given tendency to fully 
develop itself. Thus it is that castration often 
affects the bodily appearance of those animals 
operated on. When a mutation appears, natural 
selection decides whether or not it shall persist. 




Variation along definite lines and Natural Selection are un- 
doubtedly 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 im- 
portant factor — Examples of correlation — Correlation is a 
subject that requires close study — Isolation a factor in evolu- 
tion — 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. 

WE have so far considered three factors 
of evolution. The first of these is 
the tendency of organisms to vary- 
along definite lines. This is a most 
important factor, because, unless variation occurs 
in any given direction, there can be no evolution 
in that direction. Variations are the materials 
upon which the other factors, or causes, of evolu- 
tion work. The second great factor is natural 
selection. Natural selection may be compared 


The Making of Species 

to a builder, and variations to his materials. 
The kind of building that a builder can construct 
depends very largely on the material supplied to 
him. The Forth Bridge could not have been 
built had those who constructed it had no material 
given them but bricks and mortar. Wallaceians 
regard natural selection as a builder who is sup- 
plied with every kind of building material — stone, 
bricks, wood, iron, aluminium, in any quantities 
he may desire. They therefore regard natural 
selection as the one and only cause which deter- 
mines evolution. This, however, is a wrong 
idea. Natural selection should rather be likened 
to a builder who is supplied with a limited variety 
of building materials, so that considerable restric- 
tions are imposed on his building operations. 
The doors, windows, fireplaces, etc., are supplied 
to him ready-made. He merely selects which of 
these he will use for each building. 

The third factor of evolution which we have 
considered is sexual selection. As we have seen, 
sufficient attention has not been paid to this sub- 
ject, so that we are not yet in a position to say 
how much, if any, influence it has exercised on 
the course of evolution. 

In addition to these three factors, there are, 
we believe, some others. Before proceeding to 
a consideration of these, it is important to study 
carefully the modus operafidi of natural selection, 
or, in other words, the nature of the struggle for 


The Struggle for Existence 

existence, as many of the statements contained 
in recent books on evolution seem to us to be 
based upon a mistaken conception of this 
important factor. 

As usual, Darwin's disciples have failed to 
improve upon the account he gave of the nature 
of the struggle for existence. This is set forth in 
Chapter III. of the Origin of Species. 

" The causes," writes Darwin (new edition, 
p. Z'^, '' which check the natural tendency of 
each species to increase in number are most 
obscure. Look at the most vigorous species ; 
by as much as it swarms in numbers, by so much 
will it tend to increase still further. We know 
not exactly what the checks are even in a single 
instance." This is perfectly true. Nevertheless 
elaborate theories of protective and warning 
colouration and mimicry have been built up on 
the tacit assumption that the checks to the multi- 
plication of all, or nearly all, species are the 
creatures which prey upon them. Possibly no 
Wallaceian asserts this in so many words, but it 
is a logical deduction from the excessive pro- 
minence each one gives to the various theories of 
animal colouration ; for, if the chief foes of an 
organism are not the creatures which prey upon 
it, how can the particular shade and pattern of 
its coat be of such paramount importance to it ? 

We shall endeavour to show that there are 
checks on the increase of a species far more 


The Making of Species 

potent than the devastation caused by those 
creatures which feed upon it. Let us, however, 
first briefly set forth some of the checks on 
the multiplication of organisms which Darwin 
mentions in the Origin of Species. 

" Eggs, or very young animals," he says, 
*'seem generally to suffer the most, but this is 
not invariably the case." This is, as we have 
already insisted, a most important point to be 
borne in mind, especially when considering the 
various current theories of animal colouration. 
When once the average animal has become adult 
its chances of survival are enormously increased. 

A second check mentioned by Darwin is the 
limitation of food supply. " The amount of food 
for each species," he writes (p. 84), " 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. . . . On the other 
hand, in some cases, as with the elephant and 
rhinoceros, none are destroyed by beasts of 

We are inclined to think that neither the food 
limit nor the beasts of prey are a very important 
check on the multiplication of organisms. The 


Checks on Increase 

lion, for example, was never so numerous as to 
reach the limit of its food supply. Before the 
white man obtained a foothold in Africa vast 
herds of herbivores were to be seen in those 
districts where lions were most plentiful. This 
is a most important fact, for, if the numbers of 
a species are not determined by those of the 
animals that prey upon it, the particular colour of 
an organism is probably not of any direct im- 
portance to it. This cuts away the foundation 
of some of the generally accepted theories of 
animal colouration. 

** Climate," writes Darwin (p. 84), " plays 
an important part in determining the average 
numbers of a species, and periodical seasons of 
extreme cold or drought seem to be the most 
effective of all checks. I estimated (chiefly from 
the greatly reduced numbers of nests in the 
spring) 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 10 per cent, is an extra- 
ordinarily severe mortality from epidemics with 

In our opinion, Darwin did not lay nearly 
enough stress upon the importance of climate as 
a check on the increase of species. We have 
seen that he stated his belief that it is the most 
effective of all checks. But even this is not a 
sufficiently strong statement of the case. It 


The Making of Species 

seems to us that before this check all other 
checks pale into insignificance. 

Darwin failed to notice the potent effects of 
damp. Damp is more injurious to most species 
than even cold or drought, as every one who has 
tried to keep birds in England knows. All en- 
tomologists are aware how harmful damp is to 
insects. Caterpillars seem to take cover under 
leaves to avoid damp rather than to hide them- 
selves from birds, since these make a point, when 
searching for insects, of invariably looking care- 
fully under leaves. 

It is a well-known fact that a wet winter in 
England causes much mortality among rabbits. 
The increase of the rabbit in Australia is usually 
attributed to the fact that the little rodent has 
not so many predatory creatures to contend with 
there as it has in Europe. This is not so. In 
Australia the rabbit has to fight against eagles, 
other large birds of prey, carnivorous marsupials, 
feral cats, monitor lizards and large snakes, to 
say nothing of the well-organised and persistent 
attacks of man. 

Were predacious creatures the most important 
foes of the rabbit it would never have obtained a 
firm foothold in Australia. Damp appears to be 
its chief enemy. In Australia this does not exist. 
Hence the remarkable increase of the species. 
Stronger evidence it would not be possible to 
advance of the potency of damp as a check on 


Checks on Increase 

the increase of a species and of the comparative 
powerlessness of the attacks of raptorial creatures. 

The failure of the sandgrouse to establish a 
footing in England is, we believe, due to the fact 
that it is constitutionally unfitted to withstand our 
damp climate. 

The camel is an animal that revels in dry 
habitats, hence the difficulty of keeping camels 
in damp Bengal, although they seem to thrive 
well enough in the drier parts of India. 

"When a species," writes Darwin (p. 86), 
** owing to highly favourable circumstances, in- 
creases 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 disproportionately 
favoured : and here comes in a sort of struggle 
between the parasite and its prey." 

Thus inadequately does Darwin deal with that 
bar to the increase of organisms, which is only 
second in importance to the effect of climate. 
The check occasioned by disease and parasites 
is one to which naturalists have as yet paid but 
little attention. The result is a very general 
misunderstanding of the true nature of the 


The Making of Species 

struggle for existence, in other words, of the 
modus operandi of natural selection. 

The tsetse-fly in Africa is a far more important 
check on the increase of some animals than the 
lions and other beasts of prey. There are in 
that continent large tracts of country, known as 
tsetse-fly belts, in which neither horse, nor ox, 
nor dog can exist. If races of these animals 
were to arise which could withstand the bite of 
the tsetse-fly, these species might increase more 
rapidly than the rabbit in Australia has done, 
nor would it matter if the creatures in question 
were bright crimson, or any other conspicuous 

Take the case of the lion in Africa. The chief 
bar to the increase in numbers of this species 
appears to be the teething troubles to which the 
whelps are liable. Now suppose that a mutation 
were to occur in the lion. Suppose that several 
members of a litter were all bright blue, and that 
these suffered from no teething troubles. They 
would probably all grow up, and although at 
some disadvantage as hunters on account of their 
conspicuous colouring, they would nevertheless 
probably increase at the expense of the normally 
coloured lions, because of the immunity of their 
offspring from death from teething troubles. 
Zoologists would then be at a loss to explain 
their bright colouring. We should have all manner 
of ingenious suggestions raised, namely, that in the 


Checks on Increase 

moonlight these creatures were really not at all 
conspicuous, indeed that they were obliteratively 
coloured. In other words, a totally wrong ex- 
planation of their colouring would be given and 
accepted. It is our belief that many of the 
explanations put forward and accepted of the 
colouration of existing species are wide of the mark. 

As all bee-keepers are aware, the disease 
known as foul-brood works more havoc among 
their bees than all the insectivorous creatures 
put together. 

Similarly throat disease among wood-pigeons 
does more towards keeping their numbers down 
than all the efforts of predacious birds. 

A check on multiplication not mentioned by 
Darwin is that which is sometimes imposed by 
the individuals of the species on one another. 
Thus, in some animals, as, for example, the 
hyaena, the male occasionally devours his own 
young ones. 

A check of a similar nature results from the 
habit which the Indian House Crow (Corvus 
splendens) has of interrupting the pairing opera- 
tions of its neighbours. 

We are now in a position to sum up briefly 
the more important requisites for success in the 
struggle for existence. 

These are not so much specialised structure as 
courage, a good constitution, mental capacity and 

2 353 

The Making of Species 

Few animals possess all these characteristics 
in a pre-eminent degree, for, to use the words of 
Mr Thompson Seton, '' Every animal has some 
strong point or it could not live, and some weak 
point or the other animals could not live." 
Courage may be of two kinds — active courage, 
like that of the Englishman, or passive courage, 
like that of the Jew. 

As D. Dewar has said : In the struggle for 
existence, '' An ounce of good solid pug- 
nacity is worth many pounds of protective 

It is of course possible for an animal to possess 
too much courage. An excessive amount of 
courage will often cause a creature to fight 
unnecessary battles, which may lead to its pre- 
mature death. This is perhaps the reason why 
the pugnacious black form of the leopard is not 
more numerous. 

Under a good constitution we must include 
the power of resisting the rigours of climate, 
more especially damp, the ability to resist 
disease, and the enjoyment of a good digestion. 
When from any cause the normal food of a 
species becomes scarce, the members of that 
species will have to starve or supplement the 
normal diet with food of an unusual nature ; and 
those that are endowed with a good digestion 
will be able to digest the new food and thus 
survive, while those which cannot assimilate food 


Attributes of Successful Species 

to which they are unaccustomed will become 
emaciated and perish. We see this in every hard 
winter in England, when the redwing, which, 
unlike other thrushes, cannot thrive on berries, is 
the first to die. Most of the more successful 
birds — the crows and gulls, for example — are 
omnivorous — that is to say, they are able to 
digest all manner of food. 

Under mental capacity, we would include 
cunning and sufficient intelligence to adapt one- 
self to changed conditions. It is largely through 
man's superior mental capacity that he has 
become the dominant species. It is true that 
he displays also courage and a good constitution, 
being able to adapt himself to life under the most 
diverse conditions ; but this is, of course, in part 
due to his mental capacity, which enables him 
to some extent to adapt his environment to 

The advantages of prolificacy are so apparent 
that it is unnecessary to dilate upon them. 
Nearly as important as excessive fertility is the 
ability on the part of the parents to look after their 
young ones. 

Every successful species possesses in a special 
degree at least one of the above attributes. It 
is interesting to take in turn the various species 
which are most widely distributed and consider 
to what extent they possess these several 


The Making of Species 

Let us now consider a factor in evolution 
which is nearly as important as natural selection 
itself — we allude to the phenomenon of correlation. 


We may define correlation as the inter- 
dependence of two or more characters. This 
phenomenon is far more common than the 
majority of naturalists seem to think. It very 
frequently happens that one particular character 
never appears in an organism without being 
accompanied by some other character which we 
should not expect to be in any way related to it. 

Darwin called attention to this phenomenon. 
** In monstrosities," he writes, on page 13 of the 
Origin of Species (new edition), *'the correlations 
between quite different parts are very curious, 
and many interesting 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 which are entirely white and have blue 
eyes are generally deaf; but it has been lately 
stated by Mr Tait that this is confined to the 

" Colour and constitutional peculiarities go 
together, of which many remarkable cases could 
be given among animals and plants. From the 



facts collected by Heusinger, it appears that 
white sheep and pigs are injured by certain 
plants, whilst dark-coloured individuals escape. 
Professor Wyman has recently communicated to 
me a good illustration of this fact : on asking 
some farmers in Virginia how it was that all 
their pigs were black, they informed him that 
the pigs ate the paint-root {Lachnanthes), which 
coloured their bones pink, and which caused 
the hoofs of all but the black varieties to drop 
off ; and one of the * crackers ' [i.e. Virginia 
squatters) added, ' we select the black members 
of a litter for raising, as they alone have a good 
chance of living.' 

" 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 cer- 
tainly modify unintentionally other parts of the 
structure, owing to the mysterious laws of the 
correlation of growth." 

The great importance of the principle of the 
correlation of organs is, that natural selection 
may indirectly cause the survival of unfavourable 
variations, or of variations which are of no 
utility to the organism, because they happen to 


The Making of Species 

he correlated with organs or structures that are 

Physiologists insist more and more upon the 
close interdependence of the various parts of the 
organism. All recent researches tend to show 
that each of the organs has, besides its primary 
function, a number of subordinate duties to per- 
form, and that the removal of one organ reacts 
on all the others. 

In face of these facts we should have expected 
those zoologists who have followed Darwin to 
have paid very close attention to the subject of 
correlation. As a matter of fact, the phenomenon 
seems to have been almost completely neglected. 
This is an example of the manner in which the 
superficial theories which to-day command wide 
acceptance have tended to bar the way to 

There seems to be, in the case of some organ- 
isms, at any rate, a distinct correlation between 
their colouring and their constitution or mental 
characters. For example, the black forms of the 
cobra, the leopard, and the jaguar are notoriously 

*' There is," writes Col. Cunningham, on p. 
344 of Some Indian Friends and Acquaintances, 
'* much variation in the temper of different 
varieties of cobras, and, as is often so noticeable 
among other sorts of animals, there would seem 
to be a distinct correlation between darkness of 



colour and badness of temper. It is probably 
in part owing to a recognition of this that the 
cobras ordinarily seen in the hands of the so- 
called snake charmers are of a very light colour, 
although the choice may also be to some extent of 
aesthetic origin, seeing that the paler varieties are 
specially ornamental, due to the brilliancy of their 
markings and the great development of their 
hoods." It would thus appear that there is also 
a correlation between the colour of the cobra and 
the size of its hood. 

Hesketh Pritchard informs us, in Thj'ough the 
Heart of Patagonia, that the Gauchos assert that 
a '' picaso " colt — that is to say, a black one with 
white points — is the reverse of docile. Similarly, 
black mice are said to be very hard to tame. 

We have already called attention to the im- 
portance of courage and the power of resisting 
the rigours of climate in the struggle for exist- 
ence. It is apparently because black is so fre- 
quently correlated with courage that it is seen 
comparatively often in nature, in spite of the fact 
that it is a very bad colour as regards protection 
from enemies. Those birds and beasts which are ' 
black are usually thriving species. The domi- 
nance of the crow tribe is a case in point. Crows, 
it is true, are not really courageous, but they are 
dangerous owing to their gregarious habits, and 
are dreaded by other creatures on account of 
their power of combination. In Birds of the 


The Making of Species 

Plains, D. Dewar records an instance of a num- 
ber of crows killing in revenge so powerful a 
bird as the kite. 

Since very many species seem to throw off 
melanistic variations, it may perhaps be asked, 
How is it that more black species do not exist ? 

The reply is twofold. In the first place, it is 
quite likely that in some organisms black varia- 
tions are not correlated with courage or extreme 
pugnacity, and when such is the case the melan- 
istic varieties will be more likely to be exter- 
minated by foes, on account of their conspicuous- 
ness. It must be remembered that, other things 
being equal, the inconspicuously coloured organ- 
ism has a better chance of survival than the 
showily coloured one. This is, of course, a very 
different attitude from that which insists on the 
all-importance to animals of protective coloura- 
tion. Secondly, it is not difficult to see how too 
much courage may be fatal to an animal in lead- 
ing it to take risks which a more timid creature 
would refrain from doing. This, as we have 
already suggested, is probably the reason why 
the black panther is so scarce. The black colour 
is readily inherited, so there must be some cause 
which tends to kill off the black varieties of the 

Lest it be thought the idea that excessive 
courage and pugnacity are harmful is mere fancy, 
let us quote from the account of the nesting 



habits of the White-rumped Swallow ( Tacky cineta 
leucorrkoa) given by Mr W. H. Hudson on p. 32 
of Argentine Ornithology. He says that no 
matter how many nesting sites are available, 
there is always much fighting amongst these 
birds for the best places. '' Most vindictively," 
he writes, '' do the little things clutch each other, 
and fall to the earth twenty times an hour, where 
they often remain struggling for a long time, 
heedless of the screams of alarm their fellows set 
up above them ; for often, while they thus lie on 
the ground punishing each other, they fall an 
easy prey to some wily pussy who has made her- 
self acquainted with their habits." 

We have already emphasised the importance 
to many species of possessing the power of resist- 
ing the effects of damp. In the case of some 
organisms favourable variations in this direction 
may possess a greater survival value than those 
in the shape of greater speed or physical strength. 

Now, if there be any correlation between the 
power of resisting damp and the colour an animal 
bears, it is quite probable that animals of this 
colour, whether or no it be conspicuous, are likely 
to survive in preference to those who are more 
protectively coloured. There is some evidence 
that in certain cases, at any rate, resistance to 
climate is correlated with colour peculiarities. 
For example, some fanciers assert that yellow- 
legged poultry resist cold and damp better than 


The Making of Species 

those whose legs are not yellow. Fowls which 
have yellow legs have also yellow skins. In this 
connection the almost universal assumption of 
orange feet by domestic guinea-fowls is sig- 
nificant. Normally the feet of these birds are 
black, and their natural African habitat is a dry 

A grey or white colour appears to be corre- 
lated with resistance to cold. In birds this may 
perhaps be explained by the fact that the feathers 
in some light-coloured varieties are longer than 
in those of normally-coloured ones. Thus mealy- 
coloured canaries have longer feathers than 
brightly-coloured ones. 

The Arctic Skua, having no enemies to fear, 
stands in no need of protective colouration. It 
would therefore seem that the white-breasted 
form of this bird becomes more numerous as it 
nears the north pole, not because of the closer 
assimilation of its plumage to the colour of the 
snowy surroundings, but because the bird has to 
resist the greater degree of cold the farther north 
it finds itself Similarly, in the region of the 
south pole the albino form of the Giant Petrel 
{Ossifraga gigantea) becomes common. Both 
these birds are themselves predatory and not 
liable to be preyed upon. 

The curious china-white legs of some desert 
birds — as, for example, coursers and larks — would 
seem to indicate a power of resisting the hot rays 



radiating from the sand on which these creatures 

White quills do not wear well either in 
domestic birds or in wild albinos. This may- 
explain why it is that when a white wild species 
of bird has any black in its plumage the black is 
almost invariably on the tips of the wings. 

White quill-feathers are one of the commonest 
variations observed in domesticated birds, never- 
theless they are as rare as complete whiteness 
among birds in their natural state. 

A chestnut or bay colour in mammals appears 
to be correlated with a high rate of speed, as in 
the thoroughbred horse. This perhaps explains 
why so many of the swiftest species of antelope, 
such as the hartebeests and sassaby [Damalzscus 
lunatus), are chestnut bay in colour. It is further 
a remarkable fact that in the Black-buck (Antilope 
cervicapra) and the Nilgai [Boselaphus trago- 
camelus) the females, which are faster than the 
males, are not black or grey like their respective 
males, but reddish. 

Wild turkeys are bronze ; tame ones are black 
more often than any other colour. This may be 
due to the fact that in them nigritude is cor- 
related with the power to resist damp. Among 
human beings those races which live in very 
swampy districts are often intensely black. 

It is a significant fact that those domestic 
animals which are bred for speed or for fighting 


The Making of Species 

purposes do not assume all the varied hues that 
characterise those that are allowed to breed in- 
discriminately. Racehorses, greyhounds, and 
homing pigeons furnish examples of this. Even 
more remarkable is the case of the Indian Aseel 
or game-cock. This is bred purely for fighting 
purposes, and is required to display extraordinary 
powers of endurance, since the spurs are cut off 
in order to prolong the fight. Thus it is that 
this Indian race of game-cocks shows little varia- 
tion when compared with the English breed, 
which fights in a more natural manner. The 
hens of the Indian form seem never to show the 
colouration of the wild jungle fowl, although the 
cocks may do so. It would appear that hens 
having the colouration of their wild ancestors 
cannot breed cocks possessed of the requisite 
courage. The Aseel is said to be of the highest 
courage only when the legs, beak and iris are 

There is, we believe, not the least doubt that 
many other connections between colour and 
various characteristics have yet to be discovered. 
It is high time that competent naturalists paid 
attention to this subject. A study of the question 
will almost certainly throw much light upon many 
phenomena of animal colouration which hitherto 
have not been satisfactorily explained. It is 
quite likely that the sandy hue displayed by 
birds and beasts which frequent desert regions 



may be due to a correlation with the power of 
withstanding intense dry heat rather than to its 
rendering them inconspicuous to their foes. 

As other examples of correlation we may cite 
the correlation which seems to obtain between 
short canine teeth and the absence of a hairy 
covering to the body. This phenomenon is 
observed both in men and pigs. Hairless dogs 
almost invariably have their teeth but poorly 

Darwin called attention to the connection 
between a short beak and small feet in pigeons ; 
we see the same phenomenon in the dwarf breed 
of ducks known as call-ducks. 

A curious correlation exists between fowls' 
eggs with brown shells and the incubating habit. 
Fanciers have long tried in vain to produce a 
hen that lays brown eggs without becoming 
** broody " at certain seasons. 

Among fowls, long legs are invariably cor- 
related with a short tail, as is well seen in the 
Malay breed. This correlation may explain the 
short tails of wading birds. Short-legged fowls, 
like Japanese bantams, have long tails, and it is 
significant that the short-legged Weka Rails 
{Ocydromus) of New Zealand have unusually 
long tails for the family. In this connection we 
may say that the tail-like plumes of the cranes 
are not tail-feathers, but the tertiary feathers of 
the wings. As egrets also have long trains of 


The Making of Species 

plumes growing from the back, it cannot be said 
that the short tail of the vast majority of the 
waders is due to the fact that these birds would 
be at a disadvantage were their caudal feathers 


Isolation is a most important factor in the 
making of species. It is a factor to which 
Darwin failed to attach sufficient importance, 
and one which has been to a large extent 
neglected by Wallaceians. 

We have seen how a species can be improved 
or changed by natural selection. All those in- 
dividuals which have varied in a favourable 
direction have been preserved, and allowed to 
leave behind them offspring that inherit their 
peculiarities, while those which have not so 
varied have perished without leaving behind 
any descendants. Thus the nature of the species 
has changed. The old type has given place to 
a new one. Instead of species A, species B 
exists. This is what Romanes has called mono- 
typic evolution — the transformation of one species 
into another species. But any theory of the 
origin of species must be able to answer the 
question, Why have species multiplied.'* How is 
it that species A has given rise to species B, C, 
and D, or, while itself continuing to exist, has 
thrown off sister species B and C ? How is it 


Divergence of Character 

that in the course of evolution, species have 
not been transmuted in linear series instead of 
ramifying into branches ? This ramification of 
a species into branches has been termed by 
Romanes polytypic evolution. It is easy to see 
how natural selection can bring about monotypic 
evolution, but how can it have effected polytypic 
evolution ? To use Darwin's phraseology, how 
is it that divergence of character has come about ? 
Darwin's reply to this question is (Origin of 
Species, p. 1 36), ''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 

*' We can clearly discern 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 power 
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 


The Making of Species 

some perhaps becoming less carnivorous. The 
more diversified in habits and structure the 
descendants of our carnivorous animal become, 
the more places they will 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 effect nothinof." 
Darwin was, therefore, of opinion that natural 
selection is able to bring about polytypic evolu- 
tion. Darwin tacitly assumes, in the illustration 
he gives, that the various races of the carnivorous 
animal are in some way prevented from inter- 
crossing ; for if they interbreed indiscriminately, 
these races will tend to be obliterated. 

*' That perfectly free intercrossing," writes 
Professor Lloyd Morgan (on p. 98 of Animal 
Life and Intelligence)^ " between any or all of the 
individuals of a given group of animals is, so 
long as the characters of the parents are blended 
in the offspring, fatal to divergence of character, 
is undeniable. Through the elimination of less 
favourable variations, the swiftness, strength, 
and cunning of a race may be gradually im- 
proved. But no form of elimination can possibly 
differentiate the group into swift, strong, and 
cunning varieties, distinct from each other, so 
long as all three varieties freely interbreed, and 
the characters of the parents blend with the 
offspring. Elimination may and does give rise 
to progress in any given group, as a group ; it 



does not and cannot give rise to differentia- 
tion and divergence, so long as interbreeding 
with consequent interblending of characters be 
freely permitted. Whence it inevitably follows, 
as a matter of simple logic, that where diver- 
gence has occurred, intercrossing and interbreed- 
ing must in some way have been lessened or 

Thus a new factor is introduced, that of 
isolation or segregation. And there is no ques- 
tioning the fact that it is of great importance. 
Its importance, indeed, can only be denied by 
denying the swamping effects of intercrossing, 
and such denial implies the tacit assumption that 
interbreeding and interblending are held in check 
by some form of segregation. The isolation 
explicitly denied is implicitly assumed." 

This is very sound criticism, and is not very 
materially affected by the fact that the inter- 
crossing of varieties does not necessarily imply 
a blending of their characters in the offspring; 
for, as we have seen, some characters do not 
blend. No matter what form inheritance takes, 
in order that natural selection may cause poly- 
typic evolution it must be assisted by isolation 
in some form or other. 

Thus isolation is an important factor in evolu- 
tion, though probably not so important as its 
more extreme advocates would have us believe. 
Wagner, Romanes, and Gulick have, in insisting 

2 A 369 

The Making of Species 

upon the Importance of the principle of isolation, 
rendered valuable service to biological science, 
but, in common with most men having a new- 
theory, they have pushed their conclusions to 
absurd lengths. 

As Romanes has pointed out, isolation may 
be discriminate or indiscriminate. " If," he 
writes, on p. 5 of vol. iii. of Darwin and after 
Darwin, *'a shepherd divides a flock of sheep 
without regard to their characters, he Is isolating 
one section from the other indiscriminately ; but 
if he places all the white sheep in one field, and 
all the black sheep in another field, he is isolating 
one section from the other discrlminately. Or, if 
geological subsidence divides a species into two 
parts, the Isolation will be indiscriminate ; but if 
the separation be due to one of the sections 
developing, for example, a change of instinct 
determining migration to another area, or occu- 
pation of a different habitat on the same area, 
then the isolation will be discriminate, so far as 
the resemblance of instinct is concerned." 

Other names for indiscriminate isolation are 
separate breeding and apogamy. Discriminate 
isolation is also called segregate breeding and 
homogamy. The human breeder resorts to 
discriminate isolation in that he separates all 
those creatures from which he seeks to breed, 
from those from which he does not wish to 
breed. Natural selection Itself Is, therefore, a 


Discriminate Isolation 

kind of discriminate isolator, since it isolates the 
fit by destroying all the unfit, and, inasmuch as 
it kills off all those creatures which it fails to 
isolate, it differs from other forms of isolation 
in preventing the inter-breeding of the unisolated 
forms and their giving rise to a different race. 
Thus it is clear that natural selection, unless 
aided by some other form of isolation, can give 
effect to only monotypic evolution. This is a 
point on which Romanes rightly insists strongly. 

There are several other forms of discriminate 
isolation. Sexual selection would be one of 
these. Suppose, for example, that in any 
species there are large and small varieties 
formed, and like tends to breed with like, then 
the small individuals will breed with other 
small individuals, while large ones wall mate 
with large ones ; thus two races — a large one 
and a small one — will be evolved side by side, 
provided, of course, natural selection does not 
step in and destroy one of them. 

Another kind of discriminate isolation may be 
due to the fact that one variety is ready to pair 
before the other ; thus two races are likely to 
arise which breed at different seasons. It is un- 
necessary for us to discourse further on the 
subject of discriminate isolation ; those interested 
in the subject should read vol. iii. of Darwin 
and after Darwin, by Romanes. 

It is impossible to deny the importance of 


The Making of Species 

discriminate isolation as a factor in evolution. 
On this there can be no room for disagreement 
among biologists. It is when we come to the 
subject of indiscriminate isolation that we enter 
a region of zoological strife. 

Is indiscriminate isolation per se a factor of 
evolution ? Romanes, Gulick, and Wagner 
assert that it is, Wallace and his adherents 
assert that it is not. 

As the burden of proof is on the former, they 
are entitled to the first hearing. 

"We may well be disposed, at first sight," 
writes Romanes {Darwin and after Darwin, 
p. lo), "to conclude that this kind of isolation 
can count for nothing In the process of evolution. 
For if the fundamental importance of isolation in 
the production of organic forms be due to its 
segregation of like with like, does It not follow 
that any form of isolation which is indiscriminate 
must fail to supply the very condition on which 
all the forms of discriminate isolation depend for 
their efficacy in the causing of organic evolution? 
Or, to return to one's concrete example, is it not 
self-evident that the farmer who separated his 
flock into two or more parts indiscriminately, 
would not effect any more change in his stock 
than if he had left them all to breed together ? 
Well, although at first sight this seems self- 
evident, It Is, in fact, untrue. For, unless the 
individuals which are indiscriminately isolated 


Indiscriminate Isolation 

happen to be a very large number, sooner or 
later their progeny will come to differ from that 
of the parent type, or unisolated portion of the 
parent stock. And, of course, as soon as this 
change of type begins, the isolation ceases to be 
indiscriminate ; the previous apogamy has been 
converted into homogamy, with the usual result 
of causing a divergence of type. The reason 
why progeny of an indiscriminately isolated 
section of an originally uniform stock — e.g. of a 
species — will eventually deviate from the original 
type is, to quote Mr Gulick, as follows : — ' No 
two portions of a species possess exactly the 
same average character, and the initial differ- 
ences are for ever reacting on the environment 
and on each other, in such a way as to ensure 
increasing divergence as long as the individuals 
of the two groups are kept from inter- 
generating.' " 

The words of Mr Gulick require close scrutiny. 
We may admit that *' no two portions of a species 
possess exactly the same average character," but 
why should the two, if prevented from inter- 
breeding yet subjected to similar climatic and 
other conditions, present the phenomenon of 
" increasing divergence ? " The reason assigned 
by Romanes is the " Law " of Delboeuf, which 
runs: — "^ constant cause of va7'iatio?i, however 
insignificant it may be, changes the uniformity of 
type little by little, and diversifies it ad in- 

The Making of Species 

finitumy From this ''Law" it follows, says 
Romanes, on p. 13 of vol. iii. Darwin and after 
Darwin, that '' no matter how infinitesimally 
small the difference may be between the average 
qualities of an isolated section of a species com- 
pared with the average qualities of the rest of 
that species, if the isolation continues sufficiently 
long, differentiation of specific type is necessarily 
bound to ensue." 

This deduction involves two important assump- 
tions. The first is, that in each of the separated 
portions of the given species there is a constant 
cause of variation operating in one direction in 
the case of one portion and in another direction 
in the case of the other. This assumption is, 
unfortunately, not founded on fact. If we were 
to take one hundred race-horses and shut them 
up in one park and one hundred cart-horses and 
shut them up in another park, and prevent the 
interbreeding of the two stocks, we should, if 
Romanes's tacit assumption be true, see the two 
types diverge more and more from one another. 
We know that as a matter of fact they will tend, 
generation after generation, to become more like 
one another. Galton's Law of Regression, of 
which we have already spoken, and which is 
supported by ample evidence, clearly negatives 
this tacit assumption made by Romanes and 
Gulick. The second assumption upon which 
their reasoning is based is that there is no limit 


Mollusca of Sandwich Isles 

to the amount of change which can be effected 
by the accumulation of fluctuating variations ; 
but, as we have already seen (on p. 70), there 
is a very definite limit and this limit is quickly 

Thus the arguments of Romanes and Gulick 
are fundamentally unsound. 

But the fact remains, and has to be accounted 
for, that, as a general rule, when two portions of 
a species are separated, so that they are pre- 
vented from interbreeding, they begin to diverge 
in character, and the longer they remain thus 
separated the greater becomes that divergence. 
This is an observed fact which cannot be 

It was the observance of this fact which led 
Gulick to insist with such emphasis on the im- 
portance of geographical isolation as a factor in 
evolution. He discovered that the land mollusca 
of the Sandwich Islands fall into a great number 
of varieties. 

These islands are very hilly, and Gulick found 
that each of the varieties is confined not merely 
to one island, but to one valley. '' More- 
over," writes Romanes, on p. 16 of Darwin 
and after Darwin, "on tracing this fauna from 
valley to valley, it is apparent that a slight 
variation in the occupants of valley 2, as com- 
pared with those of the adjacent valley i, 
becomes more pronounced in the next, valley 3, 


The Making of Species 

still more so in 4, etc., etc. Thus it was possible, 
as Mr Gulick says, roughly to estimate the 
amount of divergence between the occupants of 
any two given valleys by measuring the number 
of miles between them. . . . The variations 
which affect scores of species, and themselves 
eventually run into fully specific distinctions, are 
all more or less finely graduated as they pass 
from one isolated region to the next ; and they 
have reference to changes of form or colour, 
which in no one case presents any appearance 
of utility." 

Hitherto three different attempts have been 
made to explain this and allied phenomena : — 

1. That it is the result of isolation. 

2. That it is the result of natural selection. 

3. That it is the result of the action of the 

environment on the organism. 

Let us consider these in inverse order. 

In the case of some organisms, more especially 
plants, invertebrates, and fish, the environment 
does exert a direct influence on their colouration. 
But, as we have seen, the changes in colour, etc., 
thus induced appear never to be transmitted to 
the offspring of the organisms so affected. They 
disappear when the offspring are removed to 
other surroundings. 

On the other hand, local races or species — 
as, for example, the white-cheeked variety of 
sparrow found in India — usually retain their 


MoUusca of Sandwich Isles 

external appearance when the environment is 
changed. In the one case the pecuHarity is not 
inherited ; in the other it is inherited. 

The Wallaceian explanation is, of course, that 
the phenomenon is the result of natural selection. 
There must, say Wallace and his followers, be 
some differences in the environment, differences 
which we poor human beings cannot perceive, 
that have caused the divergence between the 
various isolated sections of the species. In the 
case of some local species this explanation is 
probably the correct one, but we have no hesita- 
tion in saying that natural selection is unable 
to offer a satisfactory explanation in a con- 
siderable number of instances. Take, for 
example, the case of the land mollusca of the 
Sandwich Islands. Mr Gulick worked for fifteen 
years at them, and states that so far as he is able 
to ascertain the environment in the fifteen valleys 
is essentially the same. '' To argue," writes 
Romanes, on p. 17 of vol. iii. of Darwin and 
after Darwin, '' that every one of some twenty 
contiguous valleys in the area of the same small 
island must necessarily present such differences 
of environment that all the shells in each are 
differently modified thereby, while in no one 
out of the hundreds of cases of modification in 
minute respects of form and colour can any 
human being suggest an adaptive reason therefor 
— to argue thus is merely to affirm an intrinsic- 


The Making of Species 

ally improbable dogma in the presence of a great 
and consistent array of opposing facts." 

Men of science not infrequently charge the 
clergy with adhering to dogma in face of oppos- 
ing facts ; it seems to us that many of the 
apostles of science are in this respect worse 
offenders than the most orthodox of Churchmen. 

The example of the mollusca of the Sandwich 
Islands is by no means a solitary one. D. 
Dewar cited some interesting cases in a paper 
recently read before the Royal Society of Arts 
(p. 103 of vol. Ivii. of the Society's Journal) : 

" The Indian robins present even greater 
difficulties to those who profess to pin their faith 
to the all-sufficiency of natural selection. Robins 
are found in nearly all parts of India, and fall 
into two species, the brown-backed {Thamnobia 
cambaiensis) and the black-backed Indian Robin 
{Thamnobia fulicata). The former occurs only 
in Northern India, and the latter is confined to 
the southern portion of the peninsula. The hen 
of each species is a sandy brown bird with a 
patch of brick-red feathers under the tail, so that 
we cannot tell by merely looking at a hen to 
which of the two species she belongs. The 
cock of the South Indian form is, in winter, a 
glossy black bird, with a white bar in the wing, 
and the characteristic red patch under the tail. 
The cock of the northern species, as his name 
implies, has a sandy-brown back, which contrasts 


Local Species 

strongly with the glossy black of his head, neck, 
and under parts. In summer the cocks of the 
two species grow more like one another owing to 
the wearing away of the outer edges of their 
feathers ; but it is always possible to distinguish 
between them at a glance. The two species 
meet at about the latitude of Bombay. Oates 
states that in a certain zone, from Ahmednagar 
to the mouth of the Godaveri valley, both 
species occur, and they do not appear to 

It seems impossible to maintain that natural 
selection, acting on minute variations, has 
brought about the divergence between these 
two species. Even if it be asserted that the 
difference in the colour of the feathers of the 
back of the two cocks is in some way correlated 
with adaptability to their particular environment, 
how are we to explain the fact that in a certain 
zone both species flourish ? 

'' A similar phenomenon is furnished by the 
red-vented bulbul. This genus falls into several 
species, each corresponding to a definite locality 
and differing only in details from the allied 
species, as, for example, the distance down the 
neck to which the black of the head extends. 
There is a Punjab Red-vented Bulbul i^Molpastes 
zntermedius), a Bengal {Molpastes bengalensis), a 
Burmese [Molpasles burmanicus), and a Madras 
[Molpastes hcemorrhous) species. 


The Making of Species 

"It does not seem possible to maintain the 
contention that these various species are the 
products of natural selection, for that would 
mean if the black of the head of the Punjab 
species extended further into the neck the bird 
could not live in that country." 

Thus, natural selection clearly is unable to 
explain some cases of divergence of character 
due to geographical isolation. 

There remains the third explanation, that the 
divergence is the result of the simple fact of 

We have already shown how insuperable are 
the objections to the view held by Romanes and 

It seems to us that explanation must lie in the 

fact that mutations occur every now and again in 

some species. If two portions of a species are 

separated and a mutation occurs in one portion 

and not in the other, and if the mutating form 

^^ ^^. succeeds in supplanting the parent form in that 

J' ^ '^ /isolated portion of the species in which it has 

<y /• appeared, we should have the phenomenon of 

■ , <" x/ ^^ two races or species differing in appearance 

^ >)v vP although subjected to what appear to be identical 

j^ ^ environment. 

' X^y This, of course, is pure conjecture. All that 

^ can be said of it at present is that it is not 

opposed to observed facts. That mutations do 

occur must be admitted. At present we are 



totally in the dark as to what causes them. 
They arise at the most unexpected times. 

In favour of the explanation based on ** muta- 
tion " there is the interesting fact that geographi- 
cal isolation does not by any means always cause 
divergence of character. This Romanes, with 
great fairness, freely admits. " There are," he 
writes, on p. 133 of vol. iii. of Darwin and 
after Darwin, '* four species of butterflies, belong- 
ing to three genera {Lyccsna donzelii^ L.pheretes, 
Argynnis pales, Erebia manto\ which are iden- 
tical in the polar regions and the Alps, notwith- 
standing that the sparse Alpine populations have 
been presumably separated from their parent 
stocks since the glacial period." Again, there 
are "certain species of fresh- water crustaceans 
{Apus), the representatives of which are com- 
pelled habitually to form small isolated colonies 
in widely separated ponds, and nevertheless 
exhibit no divergence of character, although 
apogamy has probably lasted for centuries." 

To these examples we may add that of the 
cormorants. These birds have an almost world- 
wide range. One species — our Cormorant 
i^Phalacrocorax carbo) — occurs in every imagin- 
able kind of environment. Isolation has not 
effected any changes in the appearance of this 
species. Yet in New Zealand there exist no 
fewer than fourteen other species of cormorant. 
New Zealand is a country where climatic con- 


The Making of Species 

ditions are comparatively uniform, nevertheless 
it boasts of no fewer than fifteen out of the thirty- 
seven known species of cormorant. A possible 
explanation of this phenomenon may be found 
in the comparatively easy conditions under which 
cormorants live in New Zealand.^ Under such 
circumstances mutants may be permitted by 
natural selection to survive, whereas in other 
parts of the world such mutants have not been 
able to hold their own. 

Prof. Bateson has likened natural selection 
to a competitive examination to which every 
organism must submit. The penalty for failure 
is immediate death. The standard of the ex- 
amination may vary with the locality. 

Isolation, then, is a very important factor in 
the making of species, for without it, in some 
form, the multiplication of species is impossible. 

Let us, in conclusion, briefly summarise what 
we now know of the method in which new species 
are made. We have studied the various factors 
of evolution — variation and correlation, heredity, 
natural selection, sexual selection, and the other 
kinds of isolation. How do these combine to bring 
new species into being, and to establish the same ? 

Let us first consider the factor known as 
natural selection, since this is the one on which 

* Hutton and Drummond record other examples of this in the 
valuable work entitled T^e Animals of New Zealand. 


Natural Selection 

Darwin laid such great stress. Natural selection, 
although a most important factor in evolution, is 
not an indispensable one. Evolution is possible 
without natural selection. 

Let us suppose that there is no such thing as 
natural selection ; that the numbers of existing 
species are kept constant by the elimination of 
all individuals born in excess of the number 
required to maintain the species at the existing 
figure, and that the elimination of the surplus is 
effected, not by natural selection, but by chance, 
by the drawing of lots. Under such circum- 
stances there may be evolution, existing species 
may undergo change, but the evolution will be 
determined solely by the lines along which 
variations occur. 

If mutations take place along certain fixed 
lines, and tend to accumulate in the given 
directions, evolution will proceed along these 
lines quite independently of the utility to the 
organism of the mutations that occur. An un- 
favourable mutation will have precisely the same 
chance of survival as a favourable one. 

If, on the other hand, mutations occur in- 
discriminately on all sides of the mean, then 
those mutations which happen to occur most 
frequently will have the best chance of survival, 
and they will mark the lines of evolution. But 
suppose that no mutation occurs more frequently 
than the others. Under such circumstances there 


The Making of Species 

will be no evolution, unless, by some cause or 
other, portions of the species are isolated, because 
in the long run the mutations will neutralise one 

Let us now suppose that natural selection 
comes into play. The old method of determining 
by lot which forms shall persist is replaced by 
selection on the fixed principle that the fittest 
shall survive. The mutations appear as before, 
and as before, of the large number that occur, 
only a few are permitted to survive. But now 
the survivors, instead of being a motley crowd, 
are a selected band, composed of individuals 
having many characteristics in common — a 
homogeneous company. Thus one result of 
natural selection is to accelerate evolution, by 
weeding out certain classes of individuals and 
preventing them breeding with those it has 
selected. On the other hand, natural selection 
will tend to diminish the number of species which 
have arisen through mutation, inasmuch as it 
weeds out many mutants which would have 
perished had their survival been determined by 

From this the kind of work performed by 
natural selection should be obvious. Natural 
selection does not make new species. These 
make themselves, or, rather, originate in accord- 
ance with the laws of variation. 

**You can," runs an old proverb, ''bring a 


Natural Selection 

horse to the drinking fountain, but you cannot 
make him drink." You may be able to bring a 
child into the world, but you cannot secure its 
survival. Variation brings into being mutants, 
which are incipient species, but variation cannot 
determine their survival. It is at this stage that 
natural selection steps in. 

But because natural selection allows certain 
mutations to persist, it is not correct to say that 
natural selection has caused these mutations or 
made or originated the species to which they give 

The Civil Service Commissioners do not make 
Indian civil servants : they merely determine 
which of a number of ready-made men shall 
become civil servants. Similarly, natural selec- 
tion does not make new species, it simply decides 
which of a number of ready-made organisms shall 
survive and establish themselves as new species. 
Nor does natural selection always do as much as 
this ; for it is not the only determinant of survival. 
Its position is sometimes comparable to that of 
the Medical Board which inspects and rejects 
the physically unfit of the candidates which have 
already been selected by some other authority. 

The examination conducted by natural selec- 
tion may be compared to a competitive one. A 
separate, independent examination is held for 
each particular locality ; consequently the severity 
of the competition will vary with the locality. 
2B 385 

The Making of Species 

In each competition some candidates pass with 
ease : they gain an unnecessarily high total of 
marks. So in nature do certain organisms, as, 
for example, the Leaf-butterflies {Kallimas), 
appear to be over-adapted to their environment. 
Other candidates manage to pass only by a very 
narrow margin : these are paralleled in nature by 
those species which are barely able to maintain 
themselves, which become extinct the moment 
the competition increases in severity. 

The great bulk of the candidates fail to obtain 
sufficient marks to gain a place among the chosen 
few ; these unsuccessful candidates correspond to 
the mutating forms which perish in the struggle 
for existence, to those individuals which happen 
to have mutated in unfavourable directions. 

Even as many candidates have acquired know- 
ledge of subjects in which they are not examined, 
so do many organisms possess characteristics 
which are of no utility to them in the struggle 
for existence. 

Wallaceians expend much time and energy in 
misguided attempts to explain the existence of 
such characters in terms of natural selection. 

Nature's examination, like that held for en- 
trance to the Indian Civil Service, is a liberal 
one, so that the qualifications of the successful 
candidates vary considerably. Provided a can- 
didate is able to gain more marks than the other 
candidates for a vacancy, it matters not in what 


Origin of the Fittest 

subjects the marks are gained. So is it in nature. 
Natural selection takes an organism as a whole. 
One species may have established itself because 
of its fleetness, a second because of its courage, 
a third because it has a strong constitution, a 
fourth because it is protectively coloured, a fifth 
because it has good digestive powers, and so on. 

We thus perceive the part played by natural 
selection and other forms of isolation in the 
making of species. It is obvious that these 
do not make species any more than the Civil 
Service Commissioners manufacture Indian civil 

The real makers of species are the inherent 
properties of protoplasm and the laws of variation 
and heredity. These determine the nature of the 
organism ; natural selection and the like factors 
merely decide for each particular organism whether 
it shall survive and give rise to a species. 

The way in which natural selection does its 
work is comparatively easy to understand. But 
this is only the fringe of the territory which we 
call evolution. 

We seem to be tolerably near a solution of 
the problem of the causes of the survival of 
any particular mutation. This, however, is 
merely a side issue. The real problem is the 
cause of variations and mutations, or, in other 
words, how species originate. At present our 
knowledge of the causes of variation and muta- 


The Making of Species 

tion is practically nil. We do not even know 
along what particular lines mutations occur. 

We have yet to discover whether one mutation 
invariably leads to another along the same lines 
— in other words, whether mutating organisms 
behave as though they had behind them a force 
acting in a definite direction. The solution of 
these problems seems afar off. The hope of 
solving them lies, not in the speculations in 
which biologists of to-day are so fond of in- 
dulging, but in observation and experiment, 
especially the last. 

The future of biology is largely in the hands 
of the practical breeder. 



Accentor, i 

Accipitcr cooperi, 243 

Acorn, 49 

Acquired characters, 10, 14, 15, 18- 
24, 60, 107-10 

Acrceidce^ 175, 215, 228 

ALgilops speltczformis^ \\2> 

^githina tiphia, 244 

-Esthetic sense in birds, 306 

"African Nature Notes and Re- 
miniscences," 192, 195, 199 

Aggressive resemblance, 173 

Aguara-guazu, 181 

Aitken, E. H., 64 

"Albany Review, The," 43, 48, 
195, 204 

Albinism, 64, 65, 99, 283, 284, 362 

Alcedo ispida, 289 

Alcock, Col., 216, 217 

Alcohol, 152, 153 

Alexander, 181 

Allen, Grant, 66 

Allotrophy, 159 

Alternating characters, 143 

Alternative inheritance, 127 

Amadavat, 311 

Aniandina erythrocephala, 122 

A.fasciata, 122 

" Amazement," 93 

Amazon parrot, 103 

Amazonian dolphin, 99 

Ammonites, 67 

Ammonium sulphate, 1 51 

Amoeba, 35 

Amphidasys betularia^ lOl 

Anas boscas^ 123, 334 

A. obscura, 334 

A. pcecilorhyncha, 315, 334 

A. superciliosa, 315, 334 

A. undulata, 334 

Anastomus oscitans, 282 

Ancon sheep, 95 

Ane7?ione Diagellanica, 1 18 

A. sylvestris, 118 

Anemophilous flowers, 261 

"Animal Colouration," 194, 205, 
211, 213, 218, 222 

" Animal Life and Intelligence," 


"Animals of New Zealand," 382 
A nous, 278 
Anser cygnoides, 1 14 
Anseranas melanoleucus , 281 
Antarctic fauna, 191 
Antelope, 48, 199, 334 
Anthracoceros, 220 
Anthropoides paradisea, 279 
A. virgo, 279 
Atitilope cei'vicapra, 363 
Ape, loi 
Apogamy, 370 
Appenzeller, 340 
Apus, 381 
' ' Archiv fur 
mechanik der 

325, 330 
Arctic fauna, 173, 174, 190, 191 
Arctic regions, 173, 189 
Ardea asha, 317, 318 
A. gularis, 318 
Ardeola grayii, 250, 254 
Argali, 120, 130, 131 
" Argentine Ornithology," 361 
Argynnis paies, 381 
A. paphia, 103 
Aristotle, i 

Artei?iia milhausenii, 156 
A. salina, 156 
Aseel, 364 

Asexual reproduction, 135 
Asiatic, 140 
Ass, 117, 127, 128, 140 
As fur badius, 235 
Atavism, 136, 293 
Athene chiaradice, 97 
A. noctua, 97 
Atoms, biological, 158 
"Auk, The," 190 
Aularches militaris, 216 
Avebury, Lord, 205, 260 
" Avicultural Magazine, The," 98 
Avocet, 80 

Babbler, 244 
Bactrian camel, I2I 
Bailey, 88 

Baillon's crake, 251 
Balanced characters, 143 


The Making of Species 

BaUarica chrysopelargus, 105 

B. regulorum, 105 

Bassaris astuta, 242 

Batesian mimicry, 177 

Bateson, 26, 72, T2>, 74, 75> 7^, 

102, 103, 302 
Bats, 42 

Bear, loi, 119, 190, 216, 282 
Beddard, 180, 188, 194, 205, 211 
Bee, 178, 179, 214, 221, 263, 264, 

Beech, purple, 87 
Bee-eater, 220, 278 
Beetroots, 71 
Belt, 216 
Beluga, 190 
Bentham, 260 
Bestiary, 125 
Bicheno's finch, 105 
Bilateral symmetry, 252, 253, 257 
Bingham, Col. C. T., 239 
Biological atoms, 158-69, 280 
Biological molecules, 157-69, 280, 

285, 291, 293, 294, 295, 344 
Biological radicles, 158-69 
Biophors, 153 
"Bird Book, the," 207 
"Birds of the Plains," 233, 303, 

309, 359 
Bison, 119, 126 
Blackcock, 129, 131, 249, 278 
Blackberry, 118 
Blackbird, 201, 203, 207 
Black-buck, 363 
Blakiston, 181 
Bloodsucker, 220 
Blue-bellied waxbill, 104 
Blyth, 115, 251 
Boisier, 263 
Bombyx ar^'india^ 125 
B. cynthia, 124 
Bonhote, 126, 288, 289, 290, 291, 

292, 293, 337 
Bontebock, 196 

Boselaphus tragocamehis, 357, 363 
Bos frontalis, 126 
Boulenger, 88 
Bower-bird, 306 
Brain-fever bird, 235, 236, 248 
Bramble, 261 
Branchipus, 156 
Brannam, 92 
Brent, Mr, 307 

British Museum, 129, 130, 187 

Bubo virginianus, 12. 1 

Bubulcus coroDiandus , 254 

Budgerigars, loi 

Buffalo, 120, 199 

Buflfon, 2 

Buff Orpingtons, 65 

Buff- tip moth, 215 

Bufo melanostidus, 219 

Bulbul, 123, 220, 221, 244, 245, 
255, 256, 279 

Bull, 119 

Bungarus cceruleus, 217, 247 

Bunting, reed, 98, 190, 289 

Buphus coromandus, 317, 318 

Burbank, 118 

Burnet moth, 102 

Bush-buck, 196 

Butcher-bird, 241, 253 

Buttercups, 70, 267, 274 

Butterfly, 45, 47, 102, 103, 196, 197, 
203, 204, 209, 212, 216, 238, 
239, 240, 250, 264, 280, 306, 381 

Buzzard, 262 

Cacomistle, 242 

Cairina moschata, 127, 245 

Californian currant, 119 

Caloeitas nicobarica, 65 

Calotes versicolor-, 220 

Camel, 120, 357 

Campophaga, 248 

Canary, 100, loi, 102, 117, 120, 

127, 280, 338, 362 
Canis jubatus, 181 
Capercailzie, 129, 131 
Capuchin monkey, 216 
Carbon, 153 
Carduelis caniceps, 255 
C. carduelis, 255 
Carnation, 85, 86 
Carnivores, 67 
Carp, 102 
Carrion crow, 123 
Carrot, 71, 269, 270 
Casarca cana, 129 
C. tadornoides, 129 
" Cassell's Book of the Horse," 69 
Castle, 149 

Castration, effects of, 335, 344 
Cat, 61, 98, 99, 100, 206, 282, 283, 

339, 350, 356, 361 
Cat-rabbit, 125 



Cataloe, 119 

Cataract, 340 

Caterpillars, 155, 175, 205, 21 1, 215, 

221, 350 
Cattle, 94, 9S> 115 
Centropus sinensis^ 220, 244 
Cephalophus dorice, 243 
Cephalopyrus Jlammiceps^ 244 
Cervulus muntjac, loi 
C. reeve sii, 114 
C. vaginalis, 114 
Cervus paludosus, 180 
C. sika, 120 
Ceryle rudis, 202 
Chaffinch, 289 
Chamba monaul, 104 
"Champion Ladybird," 91, 92, 93 
Change of function, theory of, 36, 


Chen nivalis^ 282 

C. rossi, 282 

Chenatopex czgyptiaca, 316 

Chenonetta jubata, 316 

Chinese goose, 99, 114, 121, 130 

Chinese pheasant, 123 

Chloephaga dispar, 105 

C. magellanica, 105, 334 

C. rubidiceps, 105, 334 

Chromosomes, 145-7 

Chryscena victor, 333 

Chrysolophus amhersticz, I2I 

C obscurus, 97 

C. /zV/z^j-, 97, 121, 337 

Chrysomih'is colombiana, 244 

Chysotis cestiva, 103 

Ciconia alba, 282 

C boyciaiza, 282 

Cinnabar moth, 227 

Cissopis leveriana, 281 

Civil Service Commissioners, 385, 

Cleistogamous flovi^ers, 260 
Climate as check on multiplication, 

349, 350 
Clouded-yellow butterfly, 103 
Clover, 69, 274 
Clyius arietis, 178, 229 
Cobra, 224, 225, 226, 358, 359 
Colias edusa, 103 
Colour-blindness, 340 
Colouration of Flowers, Law of 

Progressive, 66 
of Organisms, 170-296 

Columbidas, 331, 333 

Concealing colouration, 184-7 

Congenital characters, 18, 19 

Conn, 47 

"Contemporary Review," 26 

Cope, 15, 67 

Copsychus saularis, 281 

Coracias affinis, 123, 255 

C. indica, 123, 220, 255 

Cordon-bleu, 104 

Cormorant, 190, 191, 277, 381, 382 

Corn, Indian, 81 

Correlation, 39, 40, 117, 162, 167, 

223, 339, 340, 344, 356-65 
Corvus corone, 123, 255 
C. comix, 123, 255 
C. splendens, 353 
"Country-Side, The," 261, 265, 

266, 273, 304, 311, 313 
Courser, 362 
Court-bee, 72 
Cow, 119, 120, 126 
Crab, 155 

Crane, 105, 247, 248, 279, 282, 292 
Crateropus bicolor, 242 
C. canortis, 179 
Crax globicera, 104, 304 
C. grayi, 104 
C. hecki, 104, 304 
Crested newt, 124 
Cretaceous reptiles, 67 
Crinoids, 67 
Crocodile, 187 

Cross-fertilisation, 69, 258-60 
Croialus, 223 
Crow, 47, 123, 206, 220, 247, 255, 

281, 353, 355, 359, 361 
" Crow-pheasant," 220 
Cryptic colouring, 173 
Cuckoo. 220, 233, 235, 236, 243, 

244, 247, 248, 289 

shrike, 248 

Cuculus canorus, 289 

Cuenot, 149 

Cunningham, Col., 225, 226, 358 

J. T., 15, 19, 20, 324, 325, 329, 

331, 332, 333, 336 
Cupples, Mr, 308 
Curassow, 104, 304 
Currant, 1 19 
Cut-throat finch, 122 
Cypselus affinis, 243 
Cytisus adami, 1 19 


The Making of Species 

DAFILA acuta, 122 

Dahlia, 86 

Daisy, 266, 274 

Daltonism, 340 

Damaliscus lunatus, 363 

Damp as a check to multiplication 
of species, 350» 351 

Danaida, 175, 179, 215, 216, 226, 

Danais chrysippus, 179, 250 

Danger signal, 183, 214, 253, 254 

Darter, 277 

Darwin, 1-12, 14, 25-27, 31, 35,42, 
52, 54-7, 59, 60-3, 68, 83, 96, 
112, 114-7, 119, 123, 127, 130, 
151, 171, 175, 182, 184,233,259, 
299, 301-8, 316, 319-21, 325, 
326, 347 . „ 

"Darwin and after Darwin, 370- 

5, 377, 381 
Darwinian theory, 3, 5-8, 11, 13, 

Darwinism, i, 7, 8, 11, 14, 26 
"Darwinism," 40, 53, 112, 117, 

178, 207, 213, 228, 322, 323 
"Darwinism To-day," 16, 45, 67 
Dasyurus, 283 
De Candolle, 2>6 
Decorative plumage, 40 
Deer, loi, 120, 180, 298 
Deerhound, 304, 308 
Deer-ponies, 125 
Degeneration, 168 
Dejerine, 340 
Delage, 33, 147 
Delboeuf, Law of, 373 
Delias eucharis, 216, 220, 221 
Demiegretta^ 100 
Demoiselle crane, 277 
" Descent of Man," 234, 299, 301, 

302, 304, 305, 319, 320, 326 
Determination of sex, 165 
"Development and Heredity," 17 
De Vries, 26, 66, 69-72, 75-8, 82-9, 

95, 105, 118, 151 
Dewar, D., 43, 44, 47, 48, 195, 204, 

206, 208, 210, 225, 233, 236, 303, 

308, 309, 354, 360, 378 
Dewar, G. A. B., 196, 197 
Dicrurus ater, lyg, 233 
Didelphys nurina, 243 
Dimorphism, sexual, 5 1, 200, 201 
Dipsacus, 58 

Disease as a check to multiplication 

of species, 351 
Dissemurus paradiseus, 179, 220 
Divergence of character, 367 
Dog, 59, 68, 99, 100, 125, 225, 226, 

282, 283, 304, 308, 352, 357, 364, 

Dog-rose, 261 
Dolphin, 99 

Dominant characters, 142 
Donald, Mr D., 256 
Dragon-fly, 216, 264 
Driesh, 136 
Drongo cuckoo, 233 
Drongo-shrikes, 179, 220 
Drummond, 382 
Duck, 51, 60, 68, 97, 99, 100, 122, 

126-8, 190, 247, 249, 282, 292, 

314, 315, 334, 337, 338, 365 
Duiker-buck, 243 
Dyer, Sir William Thistleton, 26 

Eagle, 65, 190, 350 

Eagle-owl, 221 

East, M. E., 79 

Echis carinata, 224 

" Eclipse," 69 

" Edinburgh Review, The," 38 

Eel, 102 

Eggs, colours of birds', 206-9 

Egret, 100, 206, 254, 365 

Eider-duck, 249 

Eimer, 15, 16, 33 

Eisig, 222 

Elanoides furcaius y 282 

Elaps, 197, 198 

Elder, 49 

Elementary species, 77, 78, 87, 88, 89 

Elk, Irish, 67 

Emberiza citrinella, 289 

E. pyrrkuloides, 98 

E. schceniclus, 98 

Entom oph ila p icata, 281 

Entomophilous flowers, 261 

Epenthesis folleata^ 103 

Epilobias, 260 

Equus, 41 

Erebia manto, 381 

Erythrura prasina, 102 

"Essays on Evolution," 11, 173, 
177, 181, 184, 213, 223, 226, 
227, 229, 230, 231, 234, 237, 
238, 239 



Estrelda cyanogastra, 104 
M. phcenicolis, 104 
Ether, 152, 153 
Etichelia jacobaccB, 227 
Eurasian, 140 
European, 140 
Euxenura maguari, 282 
Evening primrose, 84, 85, %Z 
"Evolution of Sex, The," 306 
Existence, struggle for, 31, 32 
Eye-colour in human beings, 310 
Eyesight of birds, 211, 237-41 

insects, 264 

Eyton, IS 

*' Faery Year, The," 196 

Falcon, 204, 246, 250 

Falco peregrinator, 251 

F. sever us, 251 

False mimicry, 243 

Faults in poultry, 64 

Ferrets, 100, 119 

Finch, 117, 120 

Bicheno's, 105 

chestnut-breasted, 98 

cut-throat, 122 

Gouldian, 98 

Nonpareil, 102 

red-headed, 142 

ringed, 104 

saffron, 244 

yellow-rumped, 98 

Finn, 99, 102, 115, 131, I79, 216, 
219, 220, 235, 241, 255, 304, 
309, 310, 313, 315, 316, 358 

Fittest, survival of the, 32 

Flowers, 65, 66 

Flowers, colours of, 258-75 

Fly-catchers, 44, 45, 47, 285, 338 

Flying squirrel, 243 

"Fortnightly Review, The," 37, 38 

Foul-brood, 353 

Fowl, 56, 58, 61, 64, 65, 99, loi, 
125, 127, 128, 282, 301, 302, 

307* 314, 330, 336, 338* 339, 

361, 362, 364, 365 
Fowl-ducks, 125 
Foxes, loi, 131, 190, 191 
Fox-terrier, 19 
Franqueiro cattle, 95 
Francolinus pondiceriamis ^ 337 
Friar-bird, 249 

Fringella coelebs, 209 
Fritillary butterfly, 103 
Frog, 325 

Fruits, colours of, 258, 275 
Ftiligula marila, 1<^Q) 
Fulmar petrel, 190 
Function, change of, 36, 37 
Fungi, 263 

Gadow, Dr, 197, 245 

Gad wall, 126, 315 

Galton, 81, 82, 374 

"Game Birds and Wild Fowl of 

India," 131 
Gametes, segregation of, 1 43 -5 
Gannet, 282 
Gayal, 126 
Gauchos, 359 
Gecko, 210 
Geddes, 306, 326 
Gemmules, 151 
"Genesis of Species," 7, 61 
Geographical isolation, 375 
Geological record, imperfection of, 

40-2, 94 
Geranium, 260 

Germ-plasm, continuity of the, 25 
Germinal variations, 106-10 
Getim zirbamwi, 263 
Gibbon ape, loi 
Giraffe, 17, 18, 192, 196 
Globicera, 104 
Glutton, 190 
Goat, 283 
Goethe, 2 
Golden pheasant, 97, 129, 149, 

337, 338 
Golden tench, loi 
Goldfinch, 127, 255 
Goldfish, loi, 102 
Goose, 99, 100, 105, 115, 121, 130, 

190, 281, 316, 334, 339 
Gordon's currant, 119 
Goshawk, 247 
Gouldian Finch, 99 
Graba, 58 
Gradation of colour, principle of, 

Graculipica vielanoptera, 244 

" Grammar of Science, The," 309 

Grass, 273 

Grasshopper, 185 

Greenfinch, 122 


The Making of Species 

Greyhound, 364 
Grosbeak, 281, 284 
Groundsel, 260 
Grouse, red, 125 
Growth-force, 15, 16, 68 
Grus leucogeranuSy 282 
Guillemot, 58, 190, 245 
Guinea-fowl, 100, 127, 128, 279, 

Guinea-pig, 95, loi, 129, 283 
Guhck, 369, 372-7, 380 
Gull, 190, 191, 207, 247, 290, 355 
Gygis, 278 
Gyrfalcon, 190 

Haeckel, 15, 24 

Haemophilia, 340 

Halcyon smyrnensis, 202 

Halixtus albicilla, 65 

Hare, 131, 185, 200 

Harrier, loi 

Hartebeeste, 363 

Hawk-cuckoo, 235, 236 

Hawk-eagle, loi 

Hawks, 222, 235, 236, 247, 277 

Hecki, 104 

Helice, 103 

Heliconidce, 175, 215, 216, 228 

Heloderm, 217 

Henslow, 15, 22, 23, 47, 48, 259 

" Heredity," 103, 145, 166, 340 

"Heredity of Acquired Characters 

in Plants," 22, 48 
*' Heredity of Sexual Characters 

in relation to Hormones," 19, 330 
Heron, 250, 317 
Herring, 193 
Hertwig, 151 
Heusinger, 357 
Hewitt, Mr, 307 
Hierococcyx varius^ 235, 248 
Hilversum, 84 
Himalayan argali, 120 
Hinny, 127, 136, 140, 162 
Hipparchia, sevule, 205 
Hippotragus egzunus, 334 
H. niger, 334 
Hirundo rustica, 251 
H. tytleri, 251 
*' History of Creation," 24 
Hobby, 250, 251 
Homogamy, 370 
Honeyeater, 281 

Hormones, 335, 338 

Hornbill, 65, 220 

Horner, 340 

Horse, 61, 68, 69, 95, 96, 100, loi, 
117, 127, 128, 140, 266, 267, 268, 
272, 283, 322, 389, 363, 364, 374 

Horse, genealogy of, 41 

Houghton, 91 

Howard, 315, 332 

Hubrecht, 26 

Hume, 131 

Humming-bird, 328 

Hutton, 3 

Hutton, Captain, 115, 382 

Huxley, 3, 6, 11, 40, 100, iii 

Hyaena, 353 

Hybridism, 1 11-32, 292, 293 

Hydra, 21 

Hydrogen, 152, 153 

Hydrophasianus chh'urgus^ 250 

Hyla, 245 

Hypertely, 237, 240 

Hypolimnas tnisippus^ 179, 180 

''Ibis, The," 255, 256 

Icterus vulgaris^ 244, 28 1, 284 

Impeyan pheasant, 104 

Indian Civil Service, 385, 386, 387 

Indian corn, 81 

Inheritance, 133-69 

alternative, 127 

blended, 140, 148 

definition of, 138 

of acquired characters, 10, 14, 

15, 18-24, 60, 107-10 

particulate, 140 

unilateral, 139, 140, 162 

Insectivores, 67 

Intercrossing, swamping effects of, 

42, 83 
Intimidating attitudes, 224, 225 
lora, 244 
Iridescence, 186 
Irish elk, 6^, 168 
Isolation, 366-82, 387 
Isomerism, biological, 154-8 
chemical, 152-4, 157 

Ithomiincs, 228, 246 
Ivy, 261 

Jacana, 250 
Jackdaw, 51, 306 
Jaeger, 86 



Jaguar, 45, 358 
Japanese greenfinch, 122 

pheasant, 122, 124, 129 

Jardin des plantes, 88 

Java sparrow, 99. 100 

Jelly-fish, 192 

Jesse, W., 255 

Johnston, 92 

"Journal of the Bombay Natural 

History Society," 209 
"Journal of the Royal Society of 

Arts," 236, 324, 378 
Jungle-babbler, 179 
Jungle fowl, 332 

Kallima,^,^, 47, 209, 212, 235, 386 

Kellog, 16, 26, 45, 47, 67 

Kingfisher, 202, 203, 206 

Kite, 282 

" Knowledge," 171, 198, 277 

Korchinsky, 15, 33 

Krait, 216, 247 

Kuppa, 224 

Labernum, 119 
Lachnanthes, 357 
Ladybird, 213, 214 
Lamarck, 2, 14, 17, 52 
Lamarckism, 16, 24, 25 
Lambert, Edward, 341 
Lankester, Sir E. Ray, 13, 25 
Lapwing, 207 
Lark, 185, 362 
Larus ridibundtis ^ 290 
Latent characters, 149 
Law of battle, 301, 302, 321 
Leaf-butterfly, 45, 47, 209, 235, 

Lemming, 190 
Lemur, 242, 243 
Lemur catta, 242 
Leopard, black, loi, 354, 358 
Leucopternis, 282 
Ligurinus sinicus, 122 
Lily, 146 

Linaria vtilgaris peloi'ia, 86 
Linden, Grafin von, 155 
Links, missing, 41, 42 
Linnaeus, 65, 115 
Linnet, 212, 338 
"Linus L," 95, 96 
Lion, 192, 334, 349, 352 
Liothrix htteus, 179 

Lizard, 64, 207, 210, 212, 216, 217, 

220, 223, 269, 350 
Loddigesia mirabilis, 328 
Loeb, 147 

Lophophortis chambanus, 104 
L. impeyanus.) 104 
Lucerne, 118 
Lung, 36, 37 
Lutinism, 102 
Lycczna dome Hi, 381 
L. pheretes, 381 
Lycodon aulicus, 247 
Lyell, 3 

Mackerel, 193 

Madingly, 102 

Mcenia typica, 221 

Magnus, 86 

Magpie, 281 

Magpie colouring, 66, 67, 280, 281 

Magrath, 256 

Male-fern, 49 

Mallard, 65, 97, 122, 126, 132, 

293, 313, 315, 334, 337 

Malthus, 31 

Malva, 260 

Manchester School, 27 

Mannikin, 104 

Marbled newt, 124, 245 

Marshall, 28 

Mr G. A. K., 239 

Milnes, 37, 174 

Marsupials, 67 

Masters, 86 

" Materials for the Study of Varia- 
tion," 73, 103 

Mauchamp sheep, 95 

Mayer, 228 

" Mechanischphysiologische The- 
orie der Abstammungslehre," 15 

Medicago media, 118 

Megascops asio, 44 

Melanism, 64, loi, 360 

Melopsittacus undulatus, lOl 

Mendel, 42, 74, 136, 141, 142, 144, 

Mendel's Law, 145, 149, 150, 161 
Mendelism, 145 
Mesohippus, 41 
Micellae, 151 

Micropus melanoleucuSy 245 
" Mikado, The," 237 
Mildew, 49 


The Making of Species 

Mimicry, conditions of, 178 
Mimicry, protective, 45, 50, 51, 

173, 177-82, 226-51, 275, 293, 

Mink, 243 
Miohippus, 41 
Missing links, 41, 42 
Missouri currant, 119 
Mivart, Dr St George, 7, 61 
Mole, 180 
Molge blasii^ 124 
M. crisiata, 124 
M. marmorata, 124 
M. vulgaris, 221 
Mollusca, 49 
of Sandwich Islands, 375, 

Molpastes, 123, 255 
Molpastes bengalensis, 256, 379 
M. burmanicus, 2>79 
M. hcemorrhous, 255, 379 
M. intermedius, 256, 379 
M. leucogenys, 256 
Monaul, 104 
Monkey, 64, 213 
Monotypic evolution, 366 
Monstrosities, 56, 57, 358 
Morgan, Prof. LI. , 368 

T. H., 26 

Morse, 190 

Moseley, Prof., 311 

Motanlla lugubris^ 122 

M, inelanope, 122 

Moth, loi, 102, 124, 209, 215, 227, 

238, 240 
Mouse, 64, 105, 139, 141, 146, 149, 

150, 180, 185, 282, 359 
Mule, 127, 136, 140, 160, 162 
Miiller, Fritz, 81, 180 
Mlillerian mimicry, 177, 181, 182 
Munia atricapilla, 104 
M. castaneithorax, 98 
M . Jiaviprymna^ 98 
M. malacca, 104 

Muscovy duck, 99, 127, 128, 281 
Musk ox, 190, 192 
Mustela sarmattca^ 243 
Mutations, 41, 43, 66, 69, 72, 75- 

105, 124, 127, 134, 159, 160, 

169, 223, 280, 281, 284, 292, 

295. 339, 341, 342-4, 380-8 
Mutations, theory of, 26, 38, 75, 
76, 95 

Myna, 244 
Myristicivora, 282 

Naegeli, 15, 16, 151 

Nahrwal, 190 

Natural selection, theory of, stated, 

3ij 32 
"Nature," 184 
Nautili, 67 
Nectar of flowers, 262, 264, 265, 

268, 270, 271 
Neo-Darwinians, 13, 14, 25, 173, 

174, 176, 188, 214, 218, 222, 

233, 238, 242, 263, 264 
Neo-Darwinism, 51, 172, 234, 235, 

264, 275, 276, 297 
Neo-Lamarckians, 13, 14, 15 
Neophroji, 282 
Nepheronia hippia, 179 
Nettium albigulare, 179 
New organs, beginnings of, 36, 73 
Newman, 126 
Newt, 124, 221, 222 
Niata cattle, 95 
Nicobar pigeon, 65 
Nilgai, 337 
Nitrogen, 153 
Noddy, 62, 279 
Nonpareil finch, 102 
Nyroca africana, 337 

Gates, 255, 379 

Obliterative colouration, 184-7 

Ocydromzis, 365 

(Enis, 205 

CEnopopelia tranquebarica, 122, 
123, 324, 333 

CEnothera lamarckiana^ 84,85,87, Z% 

Ononis repens, 23 

O. spinosa, 22 

Opossum, 243 

Orchid, 268, 269, 270, 272 

Orgyia antigua, 215 

"Origin of Species, The," 7, 9, 11, 
31, 53, 57, 63, 114, 170, 194, 
347, 348, 356, 367 

Oriole, 244, 249, 284, 304 

Oriolus galbula, 282 

0. kundoo, 282 

O. melanocephalus, 244, 284 

" Ornithological and Other Oddi- 
ties," 255 

Orohtppus, 41 



Orr, 15-7 

Orthogenesis, 15, 16, 34 
Ossifraga gigantea, 99, 362 
Otidiphaps insularis^ 244 
Ovis amnion, 120 
O. vignei, 120 
Owen, Sir Richard, 7 
Owl, 247, 277, 289 

little, 97, 98 

scops, 1 01 

snowy, 190 

Ox, 146, 352 
Oxygen, 152, 153, 263 

Paddy bird, 254 

Paint-root, 357 

PalcEornis torquatus^ 102, 325 

Pallas, 115 

Pansy, 260 

Panther, 360 

Papilio^ 228, 246 

P. aristolochicB, 179, 216, 220, 

P. polites, I'jg 

Paradise, bird of, 62, 249 

Paradise flycatcher, 47, 202, 

303, 316, 324, 338 
Paradisea apoda, 249 
Paraguay cattle, 94 
Parnassius apollo, 155 
Paroquet, 102, 121, 325 
Parrot, 103 

Parthenogenesis, 135, 138 
Partridge, 185, 315, 337 
Parus leucopterus, 245 
Passer domesticus, 289, 342 
P. montamis, 342 
P. swainsoni, 342 
Pasteur, 5 

Pavo nigripennis, 96 
Pavoncella pugnax, 343 
Pea, sweet, 74, 75, 81, 141 
Pear, 72 

Pearson, Karl, 309, 310 
Peckham, 308 
Pekin robin, 179 
Pelagic animals, 173, 192-4 
Penguin, 191 
Pennant's parakeet, 121 
Petaurus breviceps, 243 
Petrel, 44, 190, 191, 277, 337 
Pfefifer, 33 

Phalacrocorax carbo^ 381 
Phalanger, 243 



Phalarope, 327 

Phasianidce, 125, 330 

Phasianus colchicus, 1 14, 123 

P. torguatus, 114, 123 

P. versicolor, 114, 123, 124 

Pheasant, 97, 104, 114, 121, 123, 
128-30, 141, 315, 336, 338 

Pictet, 155, 156 

Pieris napi, 155 

Piezorhynchus , 285 

Pig, 57, 283, 357, 365 

Pigeon, 61, 62, 65, 68, 71, 72, 91, 
92, 93, 98, loi, 109, 126, 127, 
244, 277, 282, 353, 357, 364, 365 

Pigment, massing of, 256 

Pike, 102, 222 

Pimpernel, 261 

Pintail duck, 130, 132, 293, 337 

Pintailed nonpareil finch, 102 

" Plant Breeding," 87 

Plasomes, 151 

Plastidules, 151 

Platycercus elegans, 121 

P. erythropepluSy 121 

P. eximius, 12 1 

Pliohippus, 41 

Plover, 207 

Plumage, decorative, 40 

Pochard, 126, 337 

Poecilomeres, 288-95 

Poephila mirabilis, 99 

Polar bear, 119, 130 

Polar bodies, 135 

Polecat, 119 

Polytypic evolution, 367 

Poppy, 82, 261 

Porzana bailloni, 251 

P. pMsilla, 25 1 

Post-nuptial display, 316 

Potentilla tormentilla, 263 

Poulton, II, 25, 26, 171, 173, 177, 
181, 184, 210, 213, 217, 221, 223- 
5, 229-35, 238-42 

Precis artexia, 203, 204, 212 

Preferential mating among human 
beings, 309, 310 

Prepotency, 136 

Prickly pear, 274 

Primrose, evening, 84, 85, 88 

Pritchard, Hesketh, 359 

"Proceedings of the Fourth In- 
ternational Ornithological Con- 
gress," 288, 337 


The Making of Species 

"Proceedings of the Linnsean So- 
ciety," 288 

*' Proceedings of the Natural His- 
tory Society of Brunn," 141 

Protohippus^ 37 

Pseudoclytia pent at a, 103 

Pseudo-sematic colours, 173 

Pseudotantalus cinereus, 282 

Ptarmigan, 190 

Pterochtrus exustus, 204 

Puffin, 191 

Pugnacity of animals, 206, 360 

Puma, 45 

Purple beech, 87 

Pycraft, W. P., 277 

Pycnorhampus affijiis, 284 

P. icteroides, 284 

Pygcera bucephala, 215 

Quail, 185 
Quatrefages, de, 124 
Quelea quelea, 98 
Q. russi, 98 

Qtierguedula crecca, 290 
Quetelet's Law, 77 

Rabbit, 99, 100, 105, 183, 253, 

283, 350, 352 
Racehorse, 69 
Radicles, biological, 159 
Rallus aqtiaticus, 251 
R. indicus, 251 
Ratzunculus bulbosus, 70 
Rappia, 245 
Raspberry, 118 
Rat, 74, 282 

water, loi 

Raven, 190 
Razorbill, 190 
Recessive characters, 142 
Recognition colours, 251-7, 27S 

marks, 124 

Red-mantled parakeet, 121 
Redpole, 207 
Redwing, 354 
Reed bunting, 98 
Reeves' pheasant, 129 
Regression, Law of, 82, 374 
Reid, Archdale, 5 
Reindeer, 190 
Rest-harrow, 22 
Reversion, 64, 65, 129, 293 
Rhinosciurus tupaioides, 180 

Rhodocera rhamni, 155 
Rhododendron ferrugineum^ 118 
R. hirsutum, 118 
Rhynchcea, 327 
Ricardo, 28 
Ringed finch, 104 
Robin, 281, 378 
Robin, Indian, 202 
Robinson, Dr H., 171, 198 

E. K., 261, 264, 265, 266, 

268, 270, 272-4 
Rodents, 67 
Rogeron, 126 
Roller, 123, 220, 25s 
Romanes, 366-81 
Rook, 51, 187 
Rose, 61, 267 
Rosella parakeet, 12 1 
Rous, Admiral, 69 
Roux, 136 
Ruff, 343 

Sable, 190 
Saffron finch, 244 
Sainfoin, 267 

Salamander, 217, 219, 221 
Salix alba, 118 
S. pentandra, 118 
Sandgrouse, 204, 351 
Sandpipers, 185, 190 
Sassaby, 363 
Satyridce, 205 
Scatliff, H. P., 91-3 
Scatliff strain, 91 
Scaup, 290 
Schmankewitsch, 156 
"Science," 166 
Sciuropterus volucella, 243 
Scops giu, loi 
Scops owl, American, 44 

, Indian, loi 

Scoter, 249 

Seal, 190, 191 

Sea-urchin, 149 

Seaweed, 263 

Sebright, Sir John, 63 

Secondary sexual characters, 298 

Segregation, 369 

of gametes, 143-5 

Selous, Edmund, 308 

F. C, 192, 195, 197, 203 

Sematic colours, 173 
Sesiafuciformis, 178 



Sexual dimorphism, 51, 297-344 

Sexual selection, theory of, 299-321 

Shaheen, 251 

Shamrock, 274 

Sheathbill, 191 

Sheep, 95, 266, 267, 283, 357, 372 

Sheldrake, 109, 129 

Shikra, 235, 236 

Shoveler, 290 

Shrew, 180, 216 

Sidgwick, 28 

Sidney, 5, 49 

Sika deer, 120 

Silver- washed fritillary butterfly, 103 

Siskin, 127, 244 

Skua, Arctic, 44, 362 

Skua-gull, 191 

Skunk, 186, 217, 221 

Skylark, 315 

Slug, 49, 185 

Smith, Adam, 28 

Snake, 185, 197, 198, 217, 220, 223- 
6, 247, 356 

Snap-dragon, 268, 272 

Snipe, 69, 327 

Sodium sulphate, 151 

Somatic variations, 106-10. 

**Some Indian Friends and Ac- 
quaintances," 225, 358 

Sorrel, 274 

Sparrow, 213, 241, 341, 342 

Java, 99, 100 

Sparrow-hawk, 235, 243 

Spatula clypeata, 290 

Spavin, 332 

'* Species and Varieties," 69, 77, 84, 
87, 118 

Species, definition of, 89 

Species, elementary, 77, 78, 87-9 

Spencer, 3, 15, 16, 28, 38, 151 

Spider, 269, 272 

Sporceginthtis amandava, 31 1 

Sports, 41, 43. 66, 75. §5. I35 

Squirrel, loi, 186, 243 

Stag, 325 

Irish, 67 

Standfuss, 155 

Stanley crane, 248, 279 

St Hilaire, T. G., 2, 356 

Stick insect, 209 

Stictoptera annulosa^ 104 

Stoat, 119, 190, 290 

Stolzmann, 327-9, 342, 343 

Stonechat, 353 

Stork, 247, 282 

" Strand Magazine," 64 

Strix flaminea, 289 

Struggle for existence, 31, 32, 48 

for nourishment, 167 

Suchetet, A., 126, 130 

Sula capensis, 282 

■5". serrator, 282 

Sunbird, 324 

Surniciilus hignbj-is, 235, 243 

Survival of the fittest, 32 

Survival value, 33, 34 

Swallow, 250, 251, 279, 361 

Swallow-shrike, 281 

Swallow-tail butterfly, 179 

Swan, 100 

Swift, 243, 250 

Swimming bladder of fishes, 36, 37 

Sy calls fiaveola, 244 

Syrphidce, 178 

Tachycineta leucorrhoa^ 361 

Tadorna cornuta, 129 

T. tadornoides, 129 

Tails, 62, 64 

Tait, Mr, 356 

Tanager, 281 

Tapir, 42 

Tasmanian devil, 282 

Teal, 290, 316 

Teasel, fuller's, 58 

Teeth, molar, 105 

Tegetmeier, Mr, 307 

Tern, 62, 278 

Terpslphone paradisi, 202, 298, 304, 

316, 324 
Tetraogallus, 337 
TetraonldcE, 125 
Tetrapteryx paradlsea^ 249 
Tetrao ietrlx, 129 
T. urogalhis, 129 
Thamnobia ca7?ibayensls, 202, 275 
T. fidlcata, 202, 378 
Thayer, Mr Abbot, 184-7 
Thompson, Seton, 354 
Thomson, 103, 136, 145, 166, 306, 

326, 340 
Throat disease, 353 
" Through Southern Mexico," 197, 

" Through the Heart of Patagonia," 



The Making of Species 

Thrush, 203, 207, 355 

Tiger, 334 

Tit, 245 

Toad, 210, 219, 241 

Toad-flax, 56 

Tortoise, 222 

Trefoil, 274 

Trochilium, 229 

Trogon, 62 

Tropidonotus piscator, 220 

Troupial, 244, 281, 284 

Tsetse-fly, 352 

Ttipaia, 180, 216 

T. ellioti, 216 

Turbit, 72, 91-3 

"Turbit, The Modern," 91 

Turkey, 95, 363 

Turnspit dog, 59 

Turtur cambayensis, 333 

T. suratensis, 333 

T. risorius, 33, 123, 126 

Tylor, Mr Alfred, 287 

Ungulates, 67 
Unilateral transmission, 341 
Unit characters, 148-52 
Uria grylle^ 245 
U. lacrymans, 58 
Urial, 120, 130, 131 
Urodynamis tritensis, 243 

Valezina, 103 
Vanessa levana, 154 
V. p7'07'sa, 154 
Vapourer moth, 215 
Variation, 52-110 

cause of, 59-60 

continuous, 56, 69, 76, 105 

definite, 55 

determinate, 55 

discontinuous, 43, 56, 72, 73, 

76, 78, 79, ^T, 105, 106, 133, 

159, 295 

germinal, 106-10, 133 

indefinite, 55, 59 


Viola, 260 
V. tricolor^ 260 
Volckamer, 86 
Vulture, 282 

Waggett, 12 
Wagner, 369, 372 
Wagtail, 122, 203 

Wallace, 3, 10, 13, 14, 25, 26, 35- 
42, 53, ii2, 114, 116, 117, 171, 
175, 177, 183, 184, 207, 213, 
228, 230, 251, 253, 256, 287, 

296, 308, 321-7. 343, 372, 377 
Wallaceian school of biologists, 14, 

24, 25, 47, 192, 210, 251, 346, 

347, 366, 377 
Wallaceism, 172, 202 
Walrus, 190 

Warblers, British, 315, 332 
Warning colours, 173, 176, 198, 

Wasp, 174, 178, 179, 214, 227 
Wasp-beetle, 229 
Water-rail, 251 
Waxbill, blue-bellied, 104 
Weasel, 190 
Weaver, red-billed, 98 
Weber, %6 

Weir, Mr Jenner, 299 
Weismann, 25, 106, 107, 151, 154 
Weka rail, 365 
"Westminster Review," 112 
Weston, G. E,, 127 
Whale, 42, 185, 190, 193 
Wheatear, 253 
Whinchat, 253 
Wiesner, 151 
Wilson, Prof. E. B., 166 
Winter coat, 188 
Wolf, 48, 130, 185, 192 
Wonder horse, 95, 96 
Woodpecker, 102 
Wright, Mr, 304 
Wyman, Professor, 357 


Yak, 120 

Yarrovi^, 268 

"Year-book of the Smithsonian 

Institution," 184 
Yerbury, Col., 239 
Youatt, 63 

Zebra, 196 

Zebu, 120 

Zocher & Co., 56 

Zoological Gardens, Lahore, 309 

, London, 104, 119, 126, 130, 

206, 304, 316 
Zoological Society of London, 330 
Zygce7ia filipendulcdy 102 




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*** Joan of Arc, by her friends accounted a saint, by her enemies a witch, stands out 
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and Work. By W. H. James Weale. With 41 Photogravure 
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Sir Martin Conway's Note. 
Nearly half a century has passed since Mr. W. H. James Weale, then resident at 
Bruges, began that long series of patient investigations into the history of Netherlandish 
art which was destined to earn so rich a harvest. When he began work Mefnlinc was 
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The van Eycks were little tnore than legendary heroes. Roger Van der Weyden was little 
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THE Lombard School, His Life and Work. By Constance 
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*^* No coTnplete Life of Vincenzo Foppa has ever been written : an omission which 
seefns almost inexplicable in these days of over-production in the Tnatter of bio- 
graphies of painters, and of subjects relating to the art of Italy. The object of the 
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to him have been brought together; all statetnents have been verified; and a great deal of 
new and unpublished material has been added. The authors have unearthed a large 
amount of new Tnaterial relating to Foppa, one of the most interesting facts brought to 
light being that he lived for twenty-three years longer than was formerly supposed. The 
illustrations will include several pictures by Foppa hitherto unknown in the history of art, 
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existing work by the mcLster at present known. 


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