variation is not essential. All animals in a state of nature are kept, by the constant struggle for existence and the survival of the fittest, in such a state of perfect health and usually superabundant vigour, that in all ordinary circumstances they possess a surplus power in every important organ-a surplus only drawn upon in cases of the direst necessity when their very existence is at stake. It follows, therefore, that any additional power given to one of the component parts of an organ must be useful—an increase, for example, either in the wing muscles or in the form or length of the wing might give some increased powers of flight; and thus alternate variations— in one generation in the muscles, in another generation in the wing itself-might be as effective in permanently improving the powers of flight as coincident variations at longer intervals. On either supposition, however, this objection appears to have little weight if we take into consideration the large amount of coincident variability that has been shown to exist.

The Beginnings of Important Organs.

We now come to an objection which has perhaps been more frequently urged than any other, and which Darwin himself felt to have much weight-the first beginnings of important organs, such, for example, as wings, eyes, mammary glands, and numerous other structures. It is urged, that it is almost impossible to conceive how the first rudiments of these could have been of any use, and, if not of use they could not have been preserved and further developed by natural selection.

Now, the first remark to be made on objections of this nature is, that they are really outside the question of the origin of all existing species from allied species not very far removed from them, which is all that Darwin undertook to prove by means of his theory. Organs and structures such as those above mentioned all date back to a very remote past, when the world and its inhabitants were both very different from what they are now. To ask of a new theory that it shall reveal to us exactly what took place in remote geological epochs, and how it took place, is unreasonable. The most that should be asked is, that some probable or possible mode of origination should be pointed out in some at least of these

One or two of

difficult cases, and this Mr. Darwin has done. these may be briefly given here, but the whole series should be carefully read by any one who wishes to see how many curious facts and observations have been required in order to elucidate them; whence we may conclude that further knowledge will probably throw light on any difficulties that still remain.1

In the case of the mammary glands Mr. Darwin remarks that it is admitted that the ancestral mammals were allied to the marsupials. Now in the very earliest mammals, almost before they really deserved that name, the young may have been nourished by a fluid secreted by the interior surface of the marsupial sack, as is believed to be the case with the fish (Hippocampus) whose eggs are hatched within a somewhat similar sack. This being the case, those individuals which secreted a more nutritious fluid, and those whose young were able to obtain and swallow a more constant supply by suction, would be more likely to live and come to a healthy maturity, and would therefore be preserved by natural selection.

In another case which has been adduced as one of special difficulty, a more complete explanation is given. Soles, turbots, and other flatfish are, as is well known, unsymmetrical. They live and move on their sides, the under side being usually differently coloured from that which is kept uppermost. Now the eyes of these fish are curiously distorted in order that both eyes may be on the upper side, where alone they would be of any use. It was objected by Mr. Mivart that a sudden transformation of the eye from one side to the other was inconceivable, while, if the transit were gradual the first step could be of no use, since this would not remove the eye from the lower side. But, as Mr. Darwin shows by reference to the researches of Malm and others, the young of these fish are quite symmetrical, and during their growth exhibit to us the whole process of change. This begins by the fish (owing to the increasing depth of the body) being unable to maintain the vertical position, so that it falls on one side. It then twists the lower eye as much as possible towards the upper side; and, the whole bony structure of the head being at 1 See Origin of Species, pp. 176-198.

this time soft and flexible, the constant repetition of this effort causes the eye gradually to move round the head till it comes to the upper side. Now if we suppose this process, which in the young is completed in a few days or weeks, to have been spread over thousands of generations during the development of these fish, those usually surviving whose eyes retained more and more of the position into which the young fish tried to twist them, the change becomes intelligible; though it still remains one of the most extraordinary cases of degeneration, by which symmetry which is so universal a characteristic of the higher animals-is lost, in order that the creature may be adapted to a new mode of life, whereby it is enabled the better to escape danger and continue its existence.

The most difficult case of all, that of the eye-the thought of which even to the last, Mr. Darwin says, gave him a cold shiver "is nevertheless shown to be not unintelligible; granting of course the sensitiveness to light of some forms of nervous tissue. For he shows that there are, in several of the lower animals, rudiments of eyes, consisting merely of pigment cells covered with a translucent skin, which may possibly serve to distinguish light from darkness, but nothing more. Then we have an optic nerve and pigment cells; then we find a hollow filled with gelatinous substance of a convex form the first rudiment of a lens. Many of the succeeding steps are lost, as would necessarily be the case, owing to the great advantage of each modification which gave increased distinctness of vision, the creatures possessing it inevitably surviving, while those below them became extinct. But we can well understand how, after the first step was taken, every variation tending to more complete vision would be preserved till we reached the perfect eye of birds and mammals. Even this, as we know, is not absolutely, but only relatively, perfect. Neither the chromatic nor the spherical aberration is absolutely corrected; while long- and short- sightedness, and the various diseases and imperfections to which the eye is liable, may be looked upon as relics of the imperfect condition from which the eye has been raised by variation and natural selection.

These few examples of difficulties as to the origin of remarkable or complex organs must suffice here; but the reader who wishes further information on the matter may study carefully

the whole of the sixth and seventh chapters of the last edition of The Origin of Species, in which these and many other cases are discussed in considerable detail.

Useless or non-adaptive Characters.

Many naturalists seem to be of opinion that a considerable number of the characters which distinguish species are of no service whatever to their possessors, and therefore cannot have been produced or increased by natural selection. Professors Bronn and Broca have urged this objection on the continent. In America, Dr. Cope, the well-known palæontologist, has long since put forth the same objection, declaring that non-adaptive characters are as numerous as those which are adaptive; but he differs completely from most who hold the same general opinion in considering that they occur chiefly "in the characters of the classes, orders, families, and other higher groups;" and the objection, therefore, is quite distinct from that in which it is urged that "specific characters" are mostly useless. More recently, Professor G. J. Romanes has urged this difficulty in his paper on "Physiological Selection" (Journ. Linn. Soc., vol. xix. pp. 338, 344). He says that the characters "which serve to distinguish allied species are frequently, if not usually, of a kind with which natural selection can have had nothing to do," being without any utilitarian significance. Again he speaks of "the enormous number," and further on of "the innumerable multitude" of specific peculiarities which are useless; and he finally declares that the question needs no further arguing, "because in the later editions of his works Mr. Darwin freely acknowledges that a large proportion of specific distinctions must be conceded to be useless to the species presenting them."

I have looked in vain in Mr. Darwin's works to find any such acknowledgment, and I think Mr. Romanes has not sufficiently distinguished between "useless characters" and "useless specific distinctions." On referring to all the passages indicated by him I find that, in regard to specific characters, Mr. Darwin is very cautious in admitting inutility. His most pronounced "admissions" on this question are the following: "But when, from the nature of the organism and of the conditions, modifications have been induced which are

unimportant for the welfare of the species, they may be, and apparently often have been, transmitted in nearly the same state to numerous, otherwise modified, descendants" (Origin, p. 175). The words I have here italicised clearly show that such characters are usually not "specific," in the sense that they are such as distinguish species from each other, but are found in numerous allied species. Again: "Thus a large yet undefined extension may safely be given to the direct and indirect results of natural selection; but I now admit, after reading the essay of Nägeli on plants, and the remarks by various authors with respect to animals, more especially those recently made by Professor Broca, that in the earlier editions of my Origin of Species I perhaps attributed too much to the action of natural selection or the survival of the fittest. I have altered the fifth edition of the Origin so as to confine my remarks to adaptive changes of structure, but I am convinced, from the light gained during even the last few years, that very many structures which now appear to us useless, will hereafter be proved to be useful, and will therefore come within the range of natural selection. Nevertheless I did not formerly consider sufficiently the existence of structures which, as far as we can at present judge, are neither beneficial nor injurious; and this I believe to be one of the greatest oversights as yet detected in my work." Now it is to be remarked that neither in these passages nor in any of the other less distinct expressions of opinion on this question, does Darwin ever admit that "specific characters "—that is, the particular characters which serve to distinguish one species from another- are ever useless, much less that "a large proportion of them" are so, as Mr. Romanes makes him "freely acknowledge." On the other hand, in the passage which I have italicised he strongly expresses his view that much of what we suppose to be useless is due to our ignorance; and as I hold myself that, as regards many of the supposed useless characters, this is the true explanation, it may be well to give a brief sketch of the progress of knowledge in transferring characters from the one category to the other.

We have only to go back a single generation, and not even the most acute botanist could have suggested a reasonable use, for each species of plant, of the infinitely varied forms, sizes,