limits. This stability of the population is preserved by killing or exposing a certain proportion of infants, or by the castration or hypospadic mutilation of a percentage of the boys before puberty. 
Papuan Spears. In some tribes every father of a family voluntarily submits to one of these radical operations after the birth of his second or third child. Personal sacrifice for the public good could surely not go further than this.
A fatal consequence of the smallness and isolation of the horde would be the constantly increasing necessity of marriages between persons closely related by ties of blood, and the effect of such unions would soon be perceptible in the physical and mental degeneracy of the race. The Dieri of southern Australia have a tradition that in the beginning fathers, mothers, brothers, sisters, and other next of kin were wont to intermarry indiscriminately, until the injurious results of these connections became apparent and led to their prohibition. First, marriages between parents and children, uncles and nieces, aunts and nephews, were forbidden, and the interdict was then extended to brothers and sisters, and finally to cousins. The result was that after a time all marriages between members of the same horde were prevented by the ban of consanguinity, so that they were obliged to enter into negotiations with other hordes for an interchange of marriageable maidens. The Kurnai, in Gipsland, forbid a man to take a wife who is more nearly related to him than in the fifth degree; but for a people who can neither read nor write or hardly count, and have therefore no genealogical records, it would be difficult to determine precisely the proximity of blood. A simpler and more effective system is that adopted by the Narinyeri, who inhabit the region of southern Australia at the mouth of Murray River. The tribe consists of eighteen independent hordes, and it is strictly forbidden for any man to marry into the horde of his father or his mother. By this regulation marriages between brothers and sisters and between cousins (unless they happen to be the children of two sisters who have not married into the same horde) are prevented. The children belong to the horde of the father, but the totem as the symbol of the family is inherited from the mother, and descends to the maternal line. Some tribes forbid matrimonial unions between persons having the same totem. This prohibition renders it impossible for a man to marry the descendants of his mother's sister, but permits him to marry the descendants of her brother, inasmuch as the
