The more Mr. Darwin’s work is studied, and more especially the more his different editions are compared, the more impossible is it to avoid a suspicion of arriere pensee as pervading it whenever the “distinctive feature” is on the tapis.  It is right to say, however, that no such suspicion attaches to Mr. A. R. Wallace, Mr. Darwin’s fellow discoverer of natural selection.  It is impossible to doubt that Mr. Wallace believed he had made a real and important improvement upon the Lamarckian system, and, as a natural consequence, unlike Mr. Darwin, he began by telling us what Lamarck had said.  He did not, I admit, say quite all that I should have been glad to have seen him say, nor use exactly the words I should myself have chosen, but he said enough to make it impossible to doubt his good faith, and his desire that we should understand that with him, as with Mr. Darwin, variations are mainly accidental, not functional.  Thus, in his memorable paper communicated to the Linnean Society in 1858 he said, in a passage which I have quoted in “Unconscious Memory”: 

“The hypothesis of Lamarck—­that progressive changes in species have been produced by the attempts of the animals to increase the development of their own organs, and thus modify their structures and habits—­has been repeatedly and easily refuted by all writers on the subject of varieties and species; . . . but the view here developed renders such an hypothesis quite unnecessary. . . .  The powerful retractile talons of the falcon and cat tribes have not been produced or increased by the volition of those animals; . . . neither did the giraffe acquire its long neck by desiring to reach the foliage of the more lofty shrubs, and constantly stretching its neck for this purpose, but because any varieties which occurred among its antitypes with a longer neck than usual at once secured A fresh range of pasture over the same ground as their shorter-necked companions, and on the first scarcity of food were thus enabled to outlive them” (italics in original). {96a}

“Which occurred” is obviously “which happened to occur, by some chance or accident entirely unconnected with use and disuse;” and though the word “accidental” is never used, there can be no doubt about Mr. Wallace’s desire to make the reader catch the fact that with him accident, and not, as with Erasmus Darwin and Lamarck, sustained effort, is the main purveyor of the variations whose accumulation amounts ultimately to specific difference.  It is a pity, however, that instead of contenting himself like a theologian with saying that his opponent had been refuted over and over again, he did not refer to any particular and tolerably successful attempt to refute the theory that modifications in organic structure are mainly functional.  I am fairly well acquainted with the literature of evolution, and have never met with any such attempt.  But let this pass; as with Mr. Darwin, so with Mr. Wallace, and so indeed with all who accept Mr. Charles Darwin’s natural selection as the main means of modification, the central idea is luck, while the central idea of the Erasmus-Darwinian system is cunning.