cross-cousins in question are as clearly related to me through the father among the Omaha as among the Hidatsa, but in the former case they are not, and in the latter they necessarily are, my father’s clansfolk. Similarly, the mother’s brother’s son and his male offspring are as emphatically related to me through my mother among the Hidatsa as anywhere, but they are not aligned in the same social group with one another and they are not classed together in terminology. For the sake of clearness I will, at the risk of repetition, formulate what I consider the probable course of events. Among certain loosely organized tribes the bifurcation of immediate kin evolved, as we find it among a number of our Far Western tribes. This tendency was amplified and became superseded by a definite clan or gentile scheme. As this scheme developed, possibly as a part of its growth, kinship terminology became not only forked but more inclusive as well. Finally, the fully established organization was able, in certain instances to exert the extreme retro-active influence on nomenclature revealed in the Hidatsa and Omaha variants. In his extremely valuable paper on Miwok organization[51] Mr. Gifford also suggests a rival explanation in place of exogamy. The Miwok of California are organized in approximately exogamous moieties, and their nomenclature bears some resemblance to that of the Omaha. More particularly is the mother’s brother’s son (and his male descendants through males?) classed with the mother’s brother. According to Mr. Gifford, this is due to the custom of a man marrying, either polygamously or after his wife’s decease, the daughter of his wife’s brother. This form of marriage is actually practised among the Miwok in addition to the more generally diffused marriage with the mother’s brother’s daughter. Obviously, the facts of terminology are consistent both with this usage and with the moiety principle. Mr. Gifford objects that among the Miwok “there are no clan or moiety brothers and sisters, all relationship being based on blood and marriage ties.” This, however, is not the essential point. It does not matter whether the unrelated members are _called_ brother or sister provided they are aligned together in the same social group; the very existence of such social groups implies a differential attitude towards fellow-members as compared with the rest of the tribe. That mere affiliation along moiety lines does not solve all the mysteries of Miwok terminology, is quite true since a sharp distinction is drawn between the mother’s brother’s daughter and the father’s sister’s daughter. Since both these relatives are eligible mates from the point of view of exogamy while as a matter of fact marriage with the paternal aunt’s daughter is prohibited, Mr. Gifford’s objection seems to be sustained. That is to say, here the social organization explains the classing together of certain relatives but not the exclusion of certain other relatives, while the specific