When, for example, we endeavor to explain the system of the Hopi, we can start with the fact that their speech constitutes them a member of the Shoshonean family, _i.e._, we can begin by comparing Hopi nomenclature with that of the Paiute, Paviotso, Ute and Shoshone. One fact that strikes us here is the great difference in the actual vocables employed by the Hopi from those of their congeners, an observation which by no means extends to all of their language. Morgan held the view that kinship words were the most persistent elements of speech, but however this rule may work in other stocks, such as the Athabaskan, it certainly does not obtain among the Shoshoneans, nor, I may add, within the Siouan family, where even such closely related languages as Crow and Hidatsa reveal far greater differences in the lexicon of relationships than might be expected from other vocables. It is, however, in the classification of kin that the distinctiveness of the Hopi seems most remarkable. Their system is not characterized by the prominent features of the Plateau Shoshonean terminologies, such as reciprocity and the separation of paternal from maternal grandparents. On the other hand, they employ the Dakota principle with the Hidatsa variation. That variant occurs, so far as we now know, only among peoples historically quite unrelated to the Hopi so that neither genetic connection nor dissemination accounts for the similarity. On the other hand, all the tribes having this feature share exogamous groups with maternal descent. Such clans are characteristic of the Hopi also, but are lacking among the other Shoshoneans. We infer from this that the Hidatsa variant among the Hopi is functionally connected with their clan system. If the neighboring Zuñi do not share this characteristic, a possible explanation may be found in the relative weakness of the Zuñi clan concept, as recently expounded by Professor Kroeber, when contrasted with its dominance in the social life of the Hopi. In other features the intimate cultural contact between the Zuñi and Hopi is emphatically apparent. Probably for no other tribes is there evidence for such exaggerated reliance on teknonymy, while a certain looseness in the use of terms common to both seems to be a general Southwestern trait. The Hopi system thus reflects both the social fabric of the tribe and its historical relations,--the ancient ones reduced to a few lexical resemblances, while the more complex tribal organization and recent cultural affiliations with the Southwest, and particularly with the Zuñi, stand out in bold relief.