h e Darwinian hypothesis has the merit of being eminently simple and comprehensible in principle, and its essential positions may be stated in a very few words: all species have been produced by the development of varieties from common stocks; by the conversion of these, first into permanent races and then into new species, by the process of natural selection , which process is essentially identical with that artificial selection by which man has originated the races of domestic animals—the struggle (...) for existence taking the place of man, and exerting, in the case of natural selection, that selective action which he performs in artificial selection. (shrink)