intelligible how the phonetics of one language may influence those of another one. Many of the American tribes are very small and intertribal marriages are, comparatively speaking, frequent, either owing to peaceful intercourse, or to the abduction and enslavement of women after warlike raids. There must always have been a considerable number of alien women in each tribe who acquired the foreign language late in life and who, therefore, transmitted the foreign pronunciation to their children. It is true that we cannot give definite observations which prove the occurrence of this phenomenon, but it can hardly be doubted that these processes were operative in all those cases where the number of alien women was considerable in proportion to the number of native women. The objective study of languages also shows that phonetic influences do spread from one people to another. The most characteristic example probably is that of the southern Bantu who have adopted the clicks of the Bushmen and Hottentots, notwithstanding the hostility that prevails between these groups.
It is not so easy to understand the development of similar categories of words in neighboring languages. It is undoubtedly true that forms of social and political organization, as well as religious life, have become alike among neighboring tribes owing to a process of acculturation. The similarity in forms of life creates the necessity of developing terms expressing these forms, and will thus bring about indirectly similarity in those ideas that are expressed by words. When we apply this assumption to such concepts as terms of relationship, in which we remain in doubt as to whether the term creates the feeling accompanying the sub-summation of an individual under a category, or whether the feeling creates the term, it seems difficult to understand the psychological process that led to the similarity of classification, although the facts of distribution make it perfectly clear that the similarities are due to diffusion. This difficulty is still greater when we deal with the fundamental concepts contained in the ancient stems that underly the modern words. How, for instance, should the habit of mind to classify all motion according to form spread from one language to another?
