I. A body of kindred constituting a distinct body politic is divided into groups, the males into groups of brothers and the females into groups of sisters, on distinctions of generations, regardless of degrees of consanguinity; and the kinship terms used express relative age. In civilized society kinships are classified on distinctions of sex, distinctions of generations, and distinctions arising from degrees of consanguinity. II. When descent is in the female line, the brother-group consists of natal brothers, together with all the materterate male cousins of whatever degree. Thus mother’s sisters’ sons and mother’s mother’s sisters’ daughters’ sons, etc, are included in a group with natal brothers. In like manner the sister-group is composed of natal sisters, together with all materterate female cousins of whatever degree. III. When descent is in the male line, the brother-group is composed of natal brothers, together with all patruate male cousins of whatever degree, and the sister-group is composed of natal sisters, together with all patruate female cousins of whatever degree. IV. The son of a member of a brother-group calls each one of the group, father; the father of a member of a brother-group calls each one of the group, son. Thus a father-group is coextensive with the brother-group to which the father belongs. A brother-group may also constitute a father-group and grandfather-group, a son-group and a grandson-group. It may also be a patruate-group and an avunculate group. It may also be a patruate cousin-group and an avunculate cousin-group; and in general, every member of a brother-group has the same consanguineal relation to persons outside of the group as that of every other member. Two postulates concerning primitive society, adopted by various ethnologic students of other countries, have been erroneously applied to the American aborigines; at the same time they have been so widely accepted as to demand consideration.