The marriage of brother and sister means, as we have seen, in most cases, marriage between a half-brother and a half-sister, having the same father but different mothers. Such marriages are not necessarily contrary to the principle here laid down. Polygyny breaks up the one family into as many sub-families as there are wives who have children, and it is not possible for the father of these sub-families to be a member of each of them in the same sense as the father is a member of the monogamous family. Nor are the children of the different mothers brought into such close contact as the children of one mother, every wife with her own family forming a little separate group, and generally living in a separate hut.[1969] On the contrary, hatred and rivalry are of no rare occurrence among the members of the various sub-families. In the Pelew Islands, according to Herr Kubary, it very seldom happens that the several wives of the same man even see each other.[1970] After speaking of the marriage of half-brother and half-sister allowed among the ancient Arabs, Professor Robertson Smith remarks, “Whatever is the origin of bars to marriage, they certainly are early associated with the feeling that it is indecent for housemates to intermarry.”[1971] Most of the recorded instances of intermarriage of brother and sister refer to royal families, to the exclusion of others; and there is no difficulty in accounting for incestuous unions of this sort. Among lower races, as well as in Europe, it is considered improper for royal persons to contract marriage with persons of less exalted birth. But whilst European princes may go to some friendly Court for their consorts, a similar course is not open to African or Asiatic potentates. Incestuous unions may also take place on account of necessity, as among the Wa-taïta, or on account of extreme isolation, as among the Karens of the Tenasserim Provinces,[1972] several of the small tribes of Brazil, and especially the Veddahs of Ceylon. Among the wild Veddahs, the different families are separated from each other by great distances, and it is only accidentally or occasionally that any others besides the members of one family are brought together.[1973] The reason for the practice of marrying a sister, says Professor Virchow, “was probably the same everywhere, in the royal families as with the naked Veddahs, the lack of suitable women or of women altogether.”[1974] Certain instances of incestuous connection are evidently the results of vitiated instincts, the origin of which we are not able to trace. It is a remarkable fact that several of the peoples among whom incestuous intercourse is said to be practised are, at the same time, expressly stated to indulge in bestiality or other unnatural vices.[1975] This shows that their sexual feelings are altogether in a perverted state.