It was in the attempt to ascertain the interrelationships between species that experiments n genetics were first made. The words "evolution" and "origin of species" are now so intimately associated with the name of Darwin that we are apt to forger that the idea of common descent had been prominent in the mnds of naturalists before he wrote, and that, for more than half a century, zealous investigators had been devoting themselves to the experimental study of that possibility. Prominent among this group of experimenters may be mentioned Koelreauter, John Hunter, Herbert Knight, Gartner, Jordan. Naudin, Godron, Lecoq, Wichura--men whose names are familiar to every reader of Animals and Plants unders Domestication.