II.

DARWINISM.1

THOSE who have read the "Life and Letters of Charles Darwin" will turn with keen interest to the present volume. The relations between Wallace and Darwin, as shown in these letters, did honour to both. Either might have fairly claimed to be the real discoverer of natural selection, yet there was an entire absence of anything like rivalry between them, an ungrudging appreciation of each other's work, and, above all, a willingness to treat their individual claims as subordinate to the truth which both were helping to bring out. Writing to Wallace in 1860, the year of the publication of the Origin of Species," Darwin says—

"I admire the generous manner in which you speak of my book. Most persons would in your position have felt some envy or jealousy. How nobly free you seem to be of this common failing of mankind! You would, if you had my leisure, have done the work just as well, perhaps better, than I have done it."

In the present volume Mr. Wallace writes more 1 Darwinism. By Alfred R. Wallace, LL.D., F.L.S., etc. Macmillan & Co.

as if he were Darwin's disciple, than as, what he really is, the independent discoverer of the theory. "I claim for my book," he says, "the position of being the advocate of pure Darwinism." And by

pure Darwinism" we are to understand the preeminently Darwinian doctrine, that natural selection is the predominant though not the only factor in the variation of species.

Mr. Wallace, thus, at once puts himself on the side of Darwin and Weismann, as against Lamarck and Herbert Spencer, though this does not imply either the unqualified acceptance of Weismann's theory, or the abandonment of the old opposition to Darwin on the subject of man. The greater part of the book is devoted to the verification and defence of Darwin's main position, not merely that descent with modification is the order of nature throughout the organic world-for this is universally admitted—but that, among the factors in evolution, natural selection is overwhelmingly important.

Those who wish for a clear statement of the evidence for natural selection, and the way in which it acts, as well as of the fundamental fact on which natural selection depends, the struggle for existence, will find what they want in Mr. Wallace's book, together with a statement in Chaps. VIII.-XI. of some of the most recent results of the investigation in the colouration of plants and animals, and the various forms of protective or predatory mimicry.

We wish, however, to call special attention to the proof in Chap. VI. that all specific characters are either useful or correlated with useful characters. The bearing of this upon the question of teleology is obvious. At a certain phase in the development of the evolution doctrine, we heard a good deal of the uncouth word "dysteleology," which meant that so far from everything in nature being designed for good, there were many things like rudimentary organs, which were not only useless but positively hurtful to the organism. At this point, however, Professor Huxley had to step in and check the enthusiasm of the anti-teleologists. It was well to have a crushing argument against theologians and those who believed in design, but the appeal to dysteleology was fatal to evolution itself:

"For either these rudiments," Professor Huxley said, "are of no use to the animals, in which case . . . they ought to have disappeared; or they are of some use to the animal, in which case they are no use as arguments against teleology."

Quite lately Mr. Romanes has argued, from the large number of useless specific characters, that natural selection can have had nothing to do with them. But Mr. Wallace points out the distinction between "useless characters" and "useless specific characters," and maintains that at least with regard to the latter-it is only our ignorance which justifies us in calling them "useless." Much that

in Darwin's time was supposed to be useless is now accounted for and shown to have a meaning, to be either directly useful or correlated with that which is useful:

"Almost every detail," says Mr. Wallace, speaking specially of plants, "is found to have a purpose and a use. The shape, the size, and the colour of the petals, even the streaks and spots with which they are adorned, the position in which they stand, the movements of the stamens and pistils at various times, especially at the period of and just after fertilization, have been proved to be strictly adaptive in so many cases that botanists now believe that all the external characters of flowers are, or have been, of use to the species."

The main interest, however, of Mr. Wallace's volume gathers round the last two chapters, the former of which contains an elaborate criticism of some modern theories of evolution opposed to Darwinism, and a clear statement of the recent speculations of Professor Weismann, while the last chapter deals with the question at issue between himself and Darwin,

Of views opposed to Darwinism four typical theories are discussed, all of them tending, in different ways, to minimize the action of natural selection, while three out of the four stand or fall with the possibility of inheriting acquired characters. The first and most important of these is the view of Herbert Spencer, which, though it runs through his works, has lately received special attention, because an article written by him for a popular review on the "Factors of Organic Evolution" was

D

triumphantly claimed by the Duke of Argyll as "a great confession" of the failure of Darwinism.

But Mr. Wallace points out—(i.) that the inherited effect of use and disuse of parts is admitted by Darwin in the "Origin of Species;" and (ii.) that, in the present state of knowledge, it is more than doubtful whether both Darwin and Spencer were not wrong in recognizing it at all. The instances adduced can all be explained on the counterassumption of there being no inheriting of acquired qualities, if we take into account the effects of the withdrawal of the action of natural selection. Where the struggle is going on every useful organ is kept up to its highest limit of size and efficiency; but when the plant or animal is artificially protected from the struggle for existence there is a natural "regression to mediocrity," as Mr. Galton has called it, which would explain, for instance, the reduced size of the wings of many birds in oceanic islands, as well as the diminished size of the muscles used in closing the jaws in the case of pet dogs fed for generations on soft food. According to Herbert Spencer, this is due to the effect of disuse independently of natural selection; according to Wallace and Darwin, and à fortiori Weismann, it is due to the fact that an organ, abnormally increased under certain circumstances by natural selection, tends to revert to mediocrity when those circumstances are changed.