in presenting intelligibly the actual development of modern ideas, it has been shown that science has progressed, with respect to these problems, by abandoning a faith in final causes for a faith in the hypothesis that works, by draining off every stagnant suspicion of ultimateness in explanation, in the light of the conviction—the product of experience—that the ideas that serve us change with our knowledge of objective fact. I shall now attempt to show that this statement applies with equal force to the development of modern conceptions of adaptation in nature.
The problem of adaptation possesses a peculiar fascination for the imaginations of men. It inheres in every mechanism that meets a human end. Watches, beehives, steamships, reciprocating engines, footballs, blackboards, fountain pens and yellow paper—all are obviously fashioned toward ends. Why not that all-inclusive mechanism, the universe itself, and all that in it is?
When Darwin came upon the field in 1859, the widespread opposition which evolution theories had already experienced lay intrenched behind an affirmative answer to this question. These were the works, first of all, that Darwin stormed with his "Origin of Species." The struggle did not center about the problem of species, though one may well gather a contrary impression from the familiar abbreviation of the title of that epoch-making book. It is in the sub-title—"the preservation of favored races in the struggle for life"—that one discovers his real objective—a mechanical theory of adaptation in organic nature. It was just because the supporters of organic evolution had lacked such a theory that they had failed to impress, not only the thinking public; but most of their biological brethren. Darwin was not reviled as an atheist because he believed in evolution; nor for that reason did he revolutionize the whole course of modern thought, it was because his; doctrine of natural selection menaced the traditional Hebraic conception of the creation that he was anathematized by the standpatters of his generation. It was because he raised such a powerful presumption against all doctrines of design in organic nature that he was able effectively to substitute for doctrines of fixity and finality the fruitful conception of change, lie did destroy the doctrine of fixity of species. He did establish the doctrine of evolution in its place. But he did so by eliminating teleological theories from the list of useful hypotheses in science.
The solution of the problem of adaptation is being sought with diminishing faith in teleological formularies. These are going the way of the other final explanations that have failed to fulfill in modern science the one prime requisite—active leadership. Since Darwin's time the attention of biologists has been shifting from those secondary adaptations which provide the material for natural selection, to the direct or primary adaptive responses of the organism to given condi-
