either in sterility or variation—how much of the work of originating species is left for natural selection?—which, as Mr. Darwin admits (“Natural Selection,” p. 63, ed. 1876), does not _induce variability_, but “implies only the preservation of _such variations as arise_, and are beneficial to the being under its conditions of life?” An important part assuredly, and one which we can never sufficiently thank Mr. Darwin for having put so forcibly before us, but an indirect part only, like the part played by time and space, and not, I think, the one which Mr. Darwin would assign to it. Mr. Darwin himself has admitted that in the earlier editions of his “Origin of Species” he “underrated, as it now seems probable, the frequency and importance of modifications due to spontaneous variability.” And this involves the having over-rated the action of “natural selection” as an agent in the evolution of species. But one gathers that he still believes the accumulation of small and fortuitous variations through the agency of “natural selection” to be the main cause of the present divergencies of structure and instinct. I do not, however, think that Mr. Darwin is clear about his own meaning. I think the prominence given to “natural selection” in connection with the “origin of species” has led him, in spite of himself, and in spite of his being on his guard (as is clearly shown by the paragraph on page 63 “Natural Selection,” above referred to), to regard “natural selection” as in some way accounting for variation, just as the use of the dangerous word “spontaneous,”—though he is so often on his guard against it, and so frequently prefaces it with the words “so-called,”—would seem to have led him into very serious confusion of thought in the passage quoted at the beginning of this paragraph. For after saying that he had underrated “the frequency and importance of modifications due to spontaneous variability,” he continues, “but it is impossible to attribute to this cause the innumerable structures which are so well adapted to the habits of life of each species.” That is to say, it is impossible to attribute these innumerable structures to spontaneous variability. What _is_ spontaneous variability? Clearly, from his preceding paragraph, Mr. Darwin means only “so-called spontaneous variations,” such as “the appearance of a moss-rose on a common rose, or of a nectarine on a peach-tree,” which he gives as good examples of so-called spontaneous variation.