173. The result of all these speculations is to render it probable that there may be in nature, give it time enough, a process which leads to the transmutation of species.
The accumulation of successive differences, each representing some element of success in the struggle for life, may easily be imagined to be capable of producing, in the course of ages, a very great change.
Reasoning out this hypothesis, the more advanced followers of Mr. Darwin do not hesitate to describe all the varieties of living things, including man, as the results of development from some primordial germ taking place throughout the course of immeasurable ages. And Mr. Darwin himself, in his work on the Descent of Man, lays great stress on the occurrence of homologous structures in man and the lower animals, as well as on the development in man of rudimentary structures, which are either absolutely useless to their possessor, or of very slight service indeed, but which appear to serve as an index of the various stages through which the human species has passed in its progress upwards from lower forms of life.
174. Mr. Wallace, however, sees in the production of man the intervention of an external will.
He remarks that the lowest types of savages are in possession of a brain, and of capacities far beyond any use to which they could apply them in their present condition, and that therefore they could not have been evolved from the mere necessities of their environments.
175. Finally, Professor Huxley imagines the possibility of the Darwinian hypothesis requiring modification. Alluding to the assumed circularity of the planetary orbits which followed the establishment of the Copernican hypothesis ([Art. 69]), he remarks:—
‘But the planetary orbits turned out to be not quite circular after all, and, grand as was the service Copernicus rendered to science, Kepler and Newton had to come after him. What if the orbit of Darwinism should be a little too circular? What if species should offer residual phenomena, here and there, not explicable by natural selection? Twenty years hence naturalists may be in a position to say whether this is, or is not, the case; but in either event they will owe the author of “The Origin of Species” an immense debt of gratitude.’
176. We will defer to our last chapter some further remarks on Mr. Darwin’s hypothesis. Meanwhile, before concluding, let us briefly allude to the original production of living things on our globe. It may, perhaps, eventually be possible by means of a hypothesis of evolution, to account for the great variety of living forms on the supposition of a single primordial germ to begin with; but the difficulty still remains how to account for this germ.
It is against all true scientific experience that life can appear without the intervention of a living antecedent. How then are we to explain the production of the primordial germ?
The difficulty of doing so from our point of view would appear to be unusually great, for we have come to the conclusion that, as a matter of scientific principle, we cannot admit any such breach of continuity as a pure act of creation in time would imply.