It does not appear that Lamarck would by any means have sufficed to convince Darwin, judging from his references to him in his Journal and the "Origin." Here is the passage in which in the second edition of his Journal he refers to the blindness of the Brazilian Tucutuco, or Ctenomys, a rodent or gnawing mammal with the habits of a mole: "Considering the strictly subterranean habits of the Tucutuco, the blindness, though so common, cannot be a very serious evil; yet it appears strange that any animal should possess an organ frequently subject to be injured. Lamarck would have been delighted with this fact had he known it when speculating (probably with more truth than usual with him) on the gradually _acquired_ blindness of the Aspalax, a gnawer living underground, and of the Proteus, a reptile living in dark caverns filled with water, in both of which animals the eye is in an almost rudimentary state, and is covered with a tendinous membrane and skin.... In the Tucutuco, which, I believe, never comes to the surface of the ground, the eye is rather larger (than in the mole), but often rendered blind and useless, though without apparently causing any inconvenience to the animal: no doubt Lamarck would have said that the Tucutuco is now passing into the state of the Aspalax and Proteus." Many years afterwards in the "Origin of Species" Darwin referred to the "erroneous views and grounds of opinion of Lamarck." No doubt some impulse to Darwin's views in this direction would be due to his intercourse with Dr. Grant at Edinburgh, whose celebrated paper on the fresh-water sponge concludes with a declaration of his belief that species are descended from other species, and that they become improved in the course of modification. But previous to the occurrences of his voyage, we can find no stronger influence tending to make Darwin an evolutionist, than Lyell's "Principles of Geology," which, by showing constant and gradual change as the law of the world's history now as in past periods, gave emphasis and point to all observations of change and succession in the living world. Indeed, in June, 1836, before Darwin's voyage was over, Lyell writes to Sir John Herschel: "In regard to the origination of new species, I am very glad to find that you think it probable that it may be carried on through the intervention of intermediate causes. I left this rather to be inferred, not thinking it worth while to offend a certain class of persons by embodying in words what would only be a speculation. But the German critics have attacked me vigorously, saying, that by the impugning of the doctrine of spontaneous generation, and substituting nothing in its place, I have left them nothing but the direct and miraculous intervention of the First Cause, as often as a new species is introduced, and hence I have overthrown my own doctrine of revolutions carried on by a regular system of secondary causes.... When I first came to the notion, which I never