The second postulate, which may be regarded as a corollary of the first, is that the primary conjugal condition was one of promiscuity, out of which different forms ot marriage were successively segregated. Now the wide range in institutional development exemplified by the American Indians affords unprecedented opportunities for testing this postulate also. The simplest demotic unit found among the aborigines is the clan or mother-descent group, in which the normal conjugal relation is essentially monogamous,(57) in which marriage is more or less strictly regulated by a system of prohibitions, and in which the chief conjugal regulation is commonly that of exogamy with respect to the clan; in higher groups, more deeply affected by contact with neighboring peoples, the simple clan organization is sometimes found to be modified, (1) by the adoption and subsequent conjugation of captive men and boys, and, doubtless more profoundly, (2) by the adoption and polygamous marriage of female captives; and in still more highly organized groups the mother-descent is lost and polygamy is regular and limited only by the capacity of the husband as a provider. The second and third stages are commonly characterized, like the first, by established prohibitions and by clan exogamy; though with the advance in organization amicable relations with certain other groups are usually established, whereby the germ of tribal organization is implanted and a system of interclan marriage, or tribal endogamy, is developed. With further advance the mother-descent group is transformed into a father-descent group, when the clan is replaced by the gens; and polygamy is a common feature of the gentile organization. In all of these stages the conjugal and consanguineal regulations are affected by the militant habits characteristic of primitive groups; more warriors than women are slain in battle, and there are more female captives than male; and thus the polygamy is mainly or wholly polygyny. In many cases civil conditions combine with or partially replace the militant conditions, yet the tendency of conjugal development is not changed. Among the Seri Indians, probably the most primitive tribe in North America, in which the demotic unit is the clan, there is a rigorous marriage custom under which the would-be groom is required to enter the family of the girl and demonstrate (1) his capacity as a provider and (2) his strength of character as a man, by a year’s probation, before he is finally accepted—the conjugal theory ofr the tribe being monogamy, though the practice, at least during recent years, has, by reason of conditions, passed into polygyny. Among several other tribes of more provident and less exclusive habit, the first of the two conditions recognized by the Seri is met by rich presents (representing accumulated property) from the groom to the girl’s family, the second condition being usually ignored, the clan organization remaining in force; among still other tribes the