It developed, as a matter of fact, that practically all the tribes with exogamous ‘clans’, _i.e._, matrilineal kin groups, or exogamous ‘gentes’, _i.e._, patrilineal kin groups, had a system of the type described, while most of the tribes lacking such groups also lacked the nomenclature in question. Accordingly, it follows that there is certainly a functional relation between these phenomena, although it is conceivable that both are functionally related to still other phenomena, and that the really significant relationship remains to be determined. As a linked illustration, the following phenomena may be presented. Among the Crow of Montana, the Hopi of Arizona, and some Melanesian tribes, the same term is applied to a father’s sister and to a father’s sister’s daughter; indeed, among the Crow and the Hopi the term is extended to all the female descendants through females of the father’s sister _ad infinitum_. Such a usage is at once intelligible from the tendency to call females of the father’s group belonging to his and younger generations by a single term, regardless of generation, _if_ descent is reckoned through the mother, for in that case, and that case only, will the individuals in question belong to the same group. And the fact is that in each of the cases mentioned, group affiliation is traced through the mother, while I know of not a single instance in which paternal descent coexists with the nomenclatorial disregard of generations in the form described. My instances show, then, that cultural traits may be functionally related, and this fact renders possible a parallelism, however limited, of cultural development in different parts of the globe. The field of culture, then, is not a region of complete lawlessness. Like causes produce like effects here as elsewhere, though the complex conditions with which we are grappling require unusual caution in definitely correlating phenomena. It is true that American ethnologists have shown that in several instances like phenomena can be traced to diverse causes; that, in short, unlike antecedents converge to the same point. However, at the risk of being anathematized as a person of utterly unhistorical mentality, I must register my belief that this point has been overdone and that the continued insistence on it by Americanists is itself an illustration of cultural inertia. Indeed, the vast majority of so-called convergencies are not genuine, but false analogies due to our throwing together diverse facts from ignorance of their true nature, just as an untutored mind will class bats with birds, or whales with fish. When, however, rather full knowledge reveals not superficial resemblance but absolute identity of cultural features, it would be miraculous, indeed, to assume that such equivalence somehow was shaped by different determinants. When a Zulu of South Africa, an Australian, and a Crow Indian all share the mother-in-law taboo imposing mutual