How, then, can it be said that, “far from being a primitive form of organization, the family is a very late product of human evolution”? By using the word “family” in a sense somewhat different--nay, widely different--from that in which it is employed in a biological discussion. In the latter usage sexual communism is not excluded; A., B., and C., D. may have offspring this season; A., D., and C., B. next season. In each season there are family groups with interchange of partners. This does not, however, conform with our conception of the family as realized under civilization. Herein, in fact, lies the essential difference between the human and the animal family. The one is a realized ideal; the other is merely a natural occurrence. Even in the case of monogamous animals, mating for life is probably not conduct in conformity with an ideal, but is due to the fact that instinctive tendencies have taken this line of direction. On the other hand, in monogamous communities of mankind, there is, unfortunately, evidence that in some cases the ideal is not strong enough to prevent presumably ancestral tendencies in the direction of communism. The basis of human social conduct is unquestionably to be traced in the social behaviour of animals, in inherited tendencies to co-operation and mutual help, in the bonds of sympathy arising through the satisfaction of impulses towards such behaviour, and perhaps, to some extent, in the influence of tradition. It is not, however, until this tradition is rendered, through descriptive communication, more continuous and more effective; it is not until an ideal of mutual aid, and social conduct generally, takes form and is rendered common to the tribe; it is not until the more or less realized conceptions of one generation are handed on to become the environment under which the succeeding generations are nurtured; it is not indeed until man consciously and reflectively aims at the bettering of his environment in accordance with standards rationally conceived and deliberately carried into execution; that a new _régime_ of civilized progress, elsewhere unknown in nature, takes definite form. Under this _régime_, the elimination of failures through natural selection, though it may not be entirely superseded, plays a subordinate part; alongside the organic continuity which is due to physical heredity, there runs a continuity of tradition through social inheritance.