A systematic comparison of the effect of definite forms of marriage on nomenclature, in different parts of the world is highly desirable. When we shall have examined how such an institution as the inheritance of a maternal uncle’s wife affects the systems of the Tlingit of northwestern America, of the Banks Islands in Melanesia, and the Thonga of South Africa, and know the action of whatever coexisting institutions may occur, we shall have gained considerably more insight into a very suggestive problem. It is fairly clear that a form of marriage does not determine nomenclature univocally, as the facts relating to the levirate indicate. To ascertain in how far parallelism actually occurs, is a matter of great moment. _Conclusion._ The question with which this chapter opens has now received an answer. Terms of relationship form a proper topic of investigation for the ethnologist, first because they are often directly correlated with cultural phenomena, such as social usages regulating marriage; secondly, because the features of kinship nomenclature are an index of tribal relationship. Any particular system is not a unified logical whole but a complex product of internal development and foreign connections. Accordingly, its features cannot be understood by themselves any more than other cultural phenomena, but only in association with concomitant traits of the native culture and in the light of a comparative survey of like features among neighboring tribes and ultimately throughout the world. By utilizing our ethnographical knowledge in applying the method of variation it is possible to ascertain, at least to a considerable extent, the causes, whether primary or secondary, that have shaped a given system.