In any case, a mutation which suppresses a character is not, as we have seen, a specific change, but merely one of the varietal order, which does not result in the production of a genuine new species. The factorial mutant with a vestigial wing or eye belongs to the same species as its wild or normal parent stock. Moreover, neither disuse nor natural selection has the slightest power to induce mutations of this kind. If mutation be the cause of the blindness of cave animals, then their presence in such caves must be accounted for by supposing that they migrated thither because they found in the cave a most suitable environment for safety, foraging, etc. Darkness alone, however, could never induce germinal, but, at most, merely somatic blindness. The Lamarckian factor of disuse and the Darwinian factor of selection have been definitely discredited as agents which could bring about hereditarily-transmissible modifications. § 4. Fossil Links All efforts, then, to establish, by means of anatomical and embryological homologies, the lineal descent of man from any known type of monkey or ape have ended in ignominious failure. Comparative anatomy and embryology can, at most, only furnish grounds for extremely vague and indefinite speculations regarding the descent of man, but they can never become a basis for specific conclusions with respect to the phylogeny of _Homo sapiens_. Every known form of ape, whether extant or extinct, is, as we have seen, far too specialized in its adaptation to arboreal life to pass muster as a feasible ancestor. The only conceivable manner in which the human body could be related to simian stock is by way of collateral descent, and the only means of proving such descent is to adduce a series of intermediate fossil types connecting modern men and modern apes with this alleged common ancestor of both. “The ascent (_sic_) of man as one of the Primates,” says Henry Fairfield Osborn, “was parallel with that of the families of apes. Man has a long line of ancestry of his own, perhaps two million or more years in length. He is not descended from any known form of ape either living or fossil.” (_The Ill. London News_, Jan. 8, 1921, p. 40.)