that, in proportion as organisms are complex, they evolve slowly, he infers that the prolongation of infancy which accompanied development of the less intelligent primates into the more intelligent ones, implied greater duration of parental care. Children, not so soon capable of providing for themselves, had to be longer nurtured by female parents, to some extent indeed by male parents, individually or jointly; and hence resulted a bond holding together parents and offspring for longer periods, and tending to initiate the family. That this has been a co-operating factor in social evolution is very probable.” The bond thus formed shows its influence even among the lowest savages, in the natural affection which subsists between a mother and her children, when these escape the not unusual fate of infanticide. Natural affection is less operative with male parents, but there are other feelings which have relation chiefly to male children which tend to form an equally binding tie. Mr. Spencer remarks that “to the yearnings of natural affection are added, in early stages of progress, certain motives, partly personal, partly social, which help to secure the lives of children, but which, at the same time, initiate differences of status between children of different sexes. There is the desire to strengthen the tribe in war; there is the wish to have a future avenger on individual enemies; there is the anxiety to leave behind one who shall perform the funeral rites and continue oblations at the grave.”[300] These motives must have been influential from the earliest period at which mankind consisted of more than a few small and isolated groups, and, therefore, we must assume that in these groups the male element was equally as strong as the female element, if, indeed, they had not a male head. Mr. Spencer remarks further that those motives, “strengthening as societies passed through the earlier stages, gradually gave a certain authority to the claims of male children, though not to those of females.”[301] These ideas are quite inconsistent with the notion that the family group ever consisted only of a female ancestor and her children, or that the woman was originally the head of, and supreme in, the family. The custom of tracing descent by the female line shows, however, that for certain purposes the woman occupied an important position, although it may, when the practice of wives going to reside among their husband’s relations become established, have tended to confirm that of female infanticide, as the children would be lost to the mother’s family group. One of the motives referred to by Mr. Spencer would, after the idea of special kinship through females had become established, affect more especially the persons bound together by a maternal tie. Where the gentile organisation is established the duty of revenging private injuries is confined to the other members of the common gens. The duty of defence against the external enemy belongs, however, to the