This system has attained its chief development among the Semitic races and those African peoples who are allied to them by blood. The most widely-spread forms of marriage now existing are polygamy and monogamy, and while the former may be traced to the polygamous phase of punalua or group marriage, it is not improbable that the latter is traceable to the polyandrous phase. At all events, monogamy has been established chiefly among those races who are supposed, formerly, to have been polyandrous. The Australians, among whom group marriage has reached so full a development, are said to show a tendency to the introduction of individual marriage. Descent through the female line, which was, at one time, universal among them, is giving place to descent through males, where residence has become fixed and property accumulated. The change is accompanied by a weakening of the group right, and the gradual introduction of marriage “by gifts, by exchange, by capture, and by elopement, one or other of these predominating.” The rights of the individual are thus substituted for those of the group, and individual marriage is recognised. Strange as are the various marriage systems we have referred to, they are based on the very simple principle that every individual has a sexual right. The conditions under which this right may be exercised vary among different peoples, their operation giving rise to the peculiar married arrangements in question. Among the Australians, almost the only restriction on sexual unions appears to be that arising from consanguinity. Their marriage regulations have evidently been formed with the intention of absolutely prohibiting unions between persons near of kin. Although marriage with a sister of the half-blood is often permitted, and for special reasons marriage with a full sister may be allowed, the objection to consanguineous unions may be declared to be universal among peoples of a low degree of culture. Their marriage regulations, however, are generally intended to have certain positive results. The chief result aimed at would seem to be the prevention of over-population. This fact, combined with the recognition of the sexual rights of man, accounts for the polyandry of the Tibetans and the Hindus, and the attainment of it is in many cases aided by the practice of infanticide. Polygamy, on the other hand, has no apparent relation to the question of population. It is connected rather with the rights of the gens or family to which the women belong, the man having, in many cases, certain duties to perform before he can obtain his wife or wives. The development of polygamy is, moreover, attended with an invasion of the sexual rights of individuals; as the appropriation of the women by the rich or powerful often renders the obtaining of wives by the poor or weak difficult, if not impossible.