The Project Gutenberg ebook of Darwinism (1889), by Alfred Russel Wallace

movements of the stamens and pistil at various times, especially at the

period of, and just after, fertilisation, have been proved to be

strictly adaptive in so many cases that botanists now believe that all

the external characters of flowers either are or have been of use to the

species.
It has also been shown, by Kerner and other botanists, that another set

of characteristics have relation to the prevention of ants, slugs, and

other animals from reaching the flowers, because these creatures would

devour or injure them without effecting fertilisation. The spines,

hairs, or sticky glands on the stem or flower-stalk, the curious hairs

or processes shutting up the flower, or sometimes even the extreme

smoothness and polish of the outside of the petals so that few insects

can hang to the part, have been shown to be related to the possible

intrusion of these "unbidden guests."[42] And, still more recently,

attempts have been made by Grant Allen and Sir John Lubbock to account

for the innumerable forms, textures, and groupings of leaves, by their

relation to the needs of the plants themselves; and there can be little

doubt that these attempts will be ultimately successful. Again, just as

flowers have been adapted to secure fertilisation or

cross-fertilisation, fruits have been developed to assist in the

dispersal of seeds; and their forms, sizes, juices, and colours can be

shown to be specially adapted to secure such dispersal by the agency of

birds and mammals; while the same end is secured in other cases by

downy seeds to be wafted through the air, or by hooked or sticky

seed-vessels to be carried away, attached to skin, wool, or feathers.

the vegetable kingdom, and one, moreover, which includes almost all the

specific characters of plants. For the species of plants are usually

characterised either by differences in the form, size, and colour of the

flowers, or of the fruits; or, by peculiarities in the shape, size,

dentation, or arrangement of the leaves; or by peculiarities in the

spines, hairs, or down with which various parts of the plant are

clothed. In the case of plants it must certainly be admitted that

"specific" characters are pre-eminently adaptive; and though there may

be some which are not so, yet all those referred to by Darwin as having

been adduced by various botanists as useless, either pertain to genera

or higher groups, or are found in some plants of a species only--that

is, are individual variations not specific characters.
In the case of animals, the most recent wide extension of the sphere of

utility has been in the matter of their colours and markings. It was of

course always known that certain creatures gained protection by their

resemblance to their normal surroundings, as in the case of white arctic

animals, the yellow or brown tints of those living in deserts, and the

green hues of many birds and insects surrounded by tropical vegetation.

But of late years these cases have been greatly increased both in number

and variety, especially in regard to those which closely imitate special

objects among which they live; and there are other kinds of coloration

which long appeared to have no use. Large numbers of animals, more

especially insects, are gaudily coloured, either with vivid hues or with

striking patterns, so as to be very easily seen. Now it has been found,

that in almost all these cases the creatures possess some special

quality which prevents their being attacked by the enemies of their kind

whenever the peculiarity is known; and the brilliant or conspicuous

colours or markings serve as a warning or signal flag against attack.

Large numbers of insects thus coloured are nauseous and inedible;

others, like wasps and bees, have stings; others are too hard to be

eaten by small birds; while snakes with poisonous fangs often have some

characteristic either of rattle, hood, or unusual colour, which

indicates that they had better be left alone.
But there is yet another form of coloration, which consists in special

markings--bands, spots, or patches of white, or of bright colour, which

vary in every species, and are often concealed when the creature is at

rest but displayed when in motion,--as in the case of the bands and

spots so frequent on the wings and tails of birds. Now these specific

markings are believed, with good reason, to serve the purpose of

enabling each species to be quickly recognised, even at a distance, by

its fellows, especially the parents by their young and the two sexes by

each other; and this recognition must often be an important factor in

securing the safety of individuals, and therefore the wellbeing and

continuance of the species. These interesting peculiarities will be more

fully described in a future chapter, but they are briefly referred to

here in order to show that the most common of all the characters by

which species are distinguished from each other--their colours and

markings--can be shown to be adaptive or utilitarian in their nature.
But besides colour there are almost always some structural characters

which distinguish species from species, and, as regards many of these

also, an adaptive character can be often discerned. In birds, for

instance, we have differences in the size or shape of the bill or the

feet, in the length of the wing or the tail, and in the proportions of

the several feathers of which these organs are composed. All these

differences in the organs on which the very existence of birds depends,

which determine the character of flight, facility for running or

climbing, for inhabiting chiefly the ground or trees, and the kind of

food that can be most easily obtained for themselves and their

offspring, must surely be in the highest degree utilitarian; although in

each individual case we, in our ignorance of the minutiae of their

life-history, may be quite unable to see the use. In mammalia specific

differences other than colour usually consist in the length or shape of

the ears and tail, in the proportions of the limbs, or in the length and

quality of the hair on different parts of the body. As regards the ears

and tail, one of the objections by Professor Bronn relates to this very

point. He states that the length of these organs differ in the various

species of hares and of mice, and he considers that this difference can

be of no service whatever to their possessors. But to this objection

Darwin replies, that it has been shown by Dr. Schöbl that the ears of

mice "are supplied in an extraordinary manner with nerves, so that they

no doubt serve as tactile organs." Hence, when we consider the life of

mice, either nocturnal or seeking their food in dark and confined

places, the length of the ears may be in each case adapted to the

particular habits and surroundings of the species. Again, the tail, in

the larger mammals, often serves the purpose of driving off flies and

other insects from the body; and when we consider in how many parts of

the world flies are injurious or even fatal to large mammals, we see

that the peculiar characteristics of this organ may in each case have

been adapted to its requirements in the particular area where the

species was developed. The tail is also believed to have some use as a

balancing organ, which assists an animal to turn easily and rapidly,

much as our arms are used when running; while in whole groups it is a

prehensile organ, and has become modified in accordance with the habits

and needs of each species. In the case of mice it is thus used by the

young. Darwin informs us that the late Professor Henslow kept some

harvest-mice in confinement, and observed that they frequently curled

their tails round the branches of a bush placed in the cage, and thus

aided themselves in climbing; while Dr. Günther has actually seen a

mouse suspend itself by the tail (_Origin_, p. 189).
Again, Mr. Lawson Tait has called attention to the use of the tail in

the cat, squirrel, yak, and many other animals as a means of preserving

the heat of the body during the nocturnal and the winter sleep. He says,

that in cold weather animals with long or bushy tails will be found

lying curled up, with their tails carefully laid over their feet like a

rug, and with their noses buried in the fur of the tail, which is thus

used exactly in the same way and for the same purpose as we use

respirators.[43]

when very large, have been supposed to be a danger to the animal in

passing rapidly through dense thickets. But Sir James Hector states,

that the wapiti, in North America, throws back its head, thus placing

the horns along the sides of the back, and is then enabled to rush

through the thickest forest with great rapidity. The brow-antlers

protect the face and eyes, while the widely spreading horns prevent

injury to the neck or flanks. Thus an organ which was certainly

developed as a sexual weapon, has been so guided and modified during its

increase in size as to be of use in other ways. A similar use of the

antlers of deer has been observed in India.[44]
The various classes of facts now referred to serve to show us that, in

the case of the two higher groups--mammalia and birds--almost all the

characters by which species are distinguished from each other are, or

may be, adaptive. It is these two classes of animals which have been

most studied and whose life-histories are supposed to be most fully

known, yet even here the assertion of inutility, by an eminent

naturalist, in the case of two important organs, has been sufficiently

met by minute details either in the anatomy or in the habits of the

groups referred to. Such a fact as this, together with the extensive

series of characters already enumerated which have been of late years

transferred from the "useless" to the "useful" class, should convince

us, that the assertion of "inutility" in the case of any organ or

peculiarity which is not a rudiment or a correlation, is not, and can

never be, the statement of a fact, but merely an expression of our

ignorance of its purpose or origin.[45]

_Instability of Non-adaptive Characters._

ever be wholly useless (or wholly unconnected with useful organs by

correlation of growth) appears to have been overlooked by those who have

maintained the frequency of such characters, and that is, their almost

necessary instability. Darwin has remarked on the extreme variability of

secondary sexual characters--such as the horns, crests, plumes, etc.,

which are found in males only,--the reason being, that, although of some

use, they are not of such direct and vital importance as those adaptive

characters on which the wellbeing and very existence of the animals

depend. But in the case of wholly useless structures, which are not

rudiments of once useful organs, we cannot see what there is to ensure

any amount of constancy or stability. One of the cases on which Mr.

Romanes lays great stress in his paper on "Physiological Selection"

(_Journ. Linn. Soc._, vol. xix. p. 384) is that of the fleshy appendages

on the corners of the jaw of Normandy pigs and of some other breeds. But

it is expressly stated that they are not constant; they appear

"frequently," or "occasionally," they are "not strictly inherited, for

they occur or fail in animals of the same litter;" and they are not

always symmetrical, sometimes appearing on one side of the face alone.

Now whatever may be the cause or explanation of these anomalous

appendages they cannot be classed with "specific characters," the most

essential features of which are, that they _are_ symmetrical, that they

_are_ inherited, and that they _are_ constant. Admitting that this

peculiar appendage is (as Mr. Romanes says rather confidently, "we

happen to know it to be") wholly useless and meaningless, the fact would

be rather an argument against specific characters being also

meaningless, because the latter never have the characteristics which

this particular variation possesses.

nature as the "sports" that arise in our domestic productions, but

which, as Mr. Darwin says, without the aid of selection would soon

disappear; while some of them may be correlations with other characters

which are or have been useful. Some of these correlations are very

curious. Mr. Tegetmeier informed Mr. Darwin that the young of white,

yellow, or dun-coloured pigeons are born almost naked, whereas other

coloured pigeons are born well clothed with down. Now, if this

difference occurred between wild species of different colours, it might

be said that the nakedness of the young could not be of any use. But the

colour with which it is correlated might, as has been shown, be useful

in many ways. The skin and its various appendages, as horns, hoofs,

hair, feathers, and teeth, are homologous parts, and are subject to very

strange correlations of growth. In Paraguay, horses with curled hair

occur, and these always have hoofs exactly like those of a mule, while

the hair of the mane and tail is much shorter than usual. Now, if any

one of these characters were useful, the others correlated with it might

be themselves useless, but would still be tolerably constant because

dependent on a useful organ. So the tusks and the bristles of the boar

are correlated and vary in development together, and the former only may

be useful, or both may be useful in unequal degrees.
The difficulty as to how individual differences or sports can become

fixed and perpetuated, if altogether useless, is evaded by those who

hold that such characters are exceedingly common. Mr. Romanes says that,

upon his theory of physiological selection, "it is quite intelligible

that when a varietal form is differentiated from its parent form by the

bar of sterility, any little meaningless peculiarities of structure or

of instinct _should at first be allowed to arise_, and that they should

then _be allowed to perpetuate themselves_ by heredity," until they are

finally eliminated by disuse. But this is entirely begging the

question. Do meaningless peculiarities, which we admit often arise as

spontaneous variations, ever perpetuate themselves in all the

individuals constituting a variety or race, without selection either

human or natural? Such characters present themselves as unstable

variations, and as such they remain, unless preserved and accumulated by

selection; and they can therefore never become "specific" characters

unless they are strictly correlated with some useful and important

peculiarities.
As bearing upon this question we may refer to what is termed Delboeuf's

law, which has been thus briefly stated by Mr. Murphy in his work on

_Habit and Intelligence_, p. 241.

"If, in any species, a number of individuals, bearing a ratio

not infinitely small to the entire number of births, are in

every generation born with a particular variation which is

neither beneficial nor injurious, and if it is not counteracted

by reversion, then the proportion of the new variety to the

original form will increase till it approaches indefinitely near

to equality."

It is not impossible that some definite varieties, such as the melanic

form of the jaguar and the bridled variety of the guillemot are due to

this cause; but from their very nature such varieties are unstable, and

are continually reproduced in varying proportions from the parent forms.

They can, therefore, never constitute species unless the variation in

question becomes beneficial, when it will be fixed by natural selection.

Darwin, it is true, says--"There can 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."[46] But no proof whatever is offered of

this statement, and it is so entirely opposed to all we know of the

facts of variation as given by Darwin himself, that the important word

"all" is probably an oversight.
On the whole, then, I submit, not only has it not been proved that an

"enormous number of specific peculiarities" are useless, and that, as a

logical result, natural selection is "not a theory of the origin of

species," but only of the origin of adaptations which are usually

common to many species, or, more commonly, to genera and families; but,

I urge further, it has not even been proved that any truly "specific"

characters--those which either singly or in combination distinguish each

species from its nearest allies--are entirely unadaptive, useless, and

meaningless; while a great body of facts on the one hand, and some

weighty arguments on the other, alike prove that specific characters

have been, and could only have been, developed and fixed by natural

selection because of their utility. We may admit, that among the great

number of variations and sports which continually arise many are

altogether useless without being hurtful; but no cause or influence has

been adduced adequate to render such characters fixed and constant

throughout the vast number of individuals which constitute any of the

more dominant species.[47]

_The Swamping Effects of Intercrossing._

the _North British Review_ in 1867, and much attention has been

attracted to it by the acknowledgment of Mr. Darwin that it proved to

him that "single variations," or what are usually termed "sports," could

very rarely, if ever, be perpetuated in a state of nature, as he had at

first thought might occasionally be the case. But he had always

considered that the chief part, and latterly the whole, of the materials

with which natural selection works, was afforded by individual

variations, or that amount of ever fluctuating variability which exists

in all organisms and in all their parts. Other writers have urged the

same objection, even as against individual variability, apparently in

total ignorance of its amount and range; and quite recently Professor

G.J. Romanes has adduced it as one of the difficulties which can alone

be overcome by his theory of physiological selection. He urges, that the

same variation does not occur simultaneously in a number of individuals

inhabiting the same area, and that it is mere assumption to say it does;

while he admits that "if the assumption were granted there would be an

end of the present difficulty; for if a sufficient number of individuals

were thus simultaneously and similarly modified, there need be no longer

any danger of the variety becoming swamped by intercrossing." I must

again refer my readers to my third chapter for the proof that such

simultaneous variability is not an assumption but a fact; but, even

admitting this to be proved, the problem is not altogether solved, and

there is so much misconception regarding variation, and the actual

process of the origin of new species is so obscure, that some further

discussion and elucidation of the subject are desirable.

_Charadriidae_, he discusses the differentiation of species; and he

expresses a rather widespread view among naturalists when, speaking of

the swamping effects of intercrossing, he adds: "This is unquestionably

a very grave difficulty, to my mind an absolutely fatal one, to the

theory of accidental variation." And in another passage he says: "The

simultaneous appearance, and its repetition in successive generations,

of a beneficial variation, in a large number of individuals in the same

locality, cannot possibly be ascribed to chance." These remarks appear

to me to exhibit an entire misconception of the facts of variation as

they actually occur, and as they have been utilised by natural selection

in the modification of species. I have already shown that every part of

the organism, in common species, does vary to a very considerable

amount, in a large number of individuals, and in the same locality; the

only point that remains to be discussed is, whether any or most of these

variations are "beneficial." But every one of these variations consists

either in increase or diminution of size or power of the organ or

faculty that varies; they can all be divided into a more effective and a

less effective group--that is, into one that is more beneficial or less

beneficial. If less size of body would be beneficial, then, as half the

variations in size are above and half below the mean or existing

standard of the species, there would be ample beneficial variations; if

a darker colour or a longer beak or wing were required, there are always

a considerable number of individuals darker and lighter in colour than

the average, with longer or with shorter beaks and wings, and thus the

beneficial variation must always be present. And so with every other

part, organ, function, or habit; because, as variation, so far as we

know, is and always must be in the two directions of excess and defect

in relation to the mean amount, whichever kind of variation is wanted is

always present in some degree, and thus the difficulty as to

"beneficial" variations occurring, as if they were a special and rare

class, falls to the ground. No doubt some organs may vary in three or

perhaps more directions, as in the length, breadth, thickness, or

curvature of the bill. But these may be taken as separate variations,

each of which again occurs as "more" or "less"; and thus the "right" or

"beneficial" or "useful" variation must always be present so long as any

variation at all occurs; and it has not yet been proved that in any

large or dominant species, or in any part, organ, or faculty of such

species, there is no variation. And even were such a case found it would

prove nothing, so long as in numerous other species variation was shown

to exist; because we know that great numbers of species and groups

throughout all geological time have died out, leaving no descendants;