This evidence of the general consensus of opinion among Socialist scholars as to the value of Darwin’s work and its special importance for Socialism could easily be enlarged indefinitely. But enough has been cited to show that a comprehensive grasp of the Socialist philosophy implies a knowledge of Darwinian theories. The greatness of Darwin’s work has two aspects; the immense impetus he gave to the general theory of evolution, and, his discovery of its main process, “natural selection.” In the popular mind this distinction is lost in confusion and a great army of popular but ill-informed expounders have added to the muddle. The two things although closely related--cause and effect--are yet quite distinct, and a clearer understanding of Darwin’s work is made possible by the distinction being kept in mind. The honor of having discovered “natural selection” Darwin shares with Wallace only; as a contributor to the theory of evolution, he is one of a long and illustrious line. But even here he is the greatest of them all precisely because of his specific discovery which, by explaining how evolution works--at least among living things, (biology)--has made the general theory impregnable. Before proceeding to that specific theory let us clearly understand that evolution has ceased to be a theory merely, it is also a well established fact. Anyone who denies this has no part or lot in the intellectual life of the last half century. Such a one, as Professor Giddings recently said, “inhabits a world of intellectual shades. He cannot grasp the earthly interests of the twentieth century.” Every science in the biological hierarchy has contributed its quota to the establishment of the theory of evolution, and that theory in return has, in one department after another, produced order and system where before nothing existed but a conglomerate mass of apparently unrelated facts. So thoroughly has the theory impregnated every branch of science that an intelligent dentist must be an evolutionist. The chief honors fall to the two sciences Ontogeny and Phylogeny. Ontogeny deals with the history of the germ from its beginning as an egg to its full fruition as a fully developed individual or as Haeckel defines it, “the history of the evolution of individual human organisms.” Phylogeny is defined by the same authority as, “the history of the evolution of the descent of man, that is, of the evolution of the various animal forms through which, in the course of countless ages, mankind has gradually passed to its present form.”