to trace genealogical relationship, but to all the members of a clan of a given generation, even if no such relationship with them can be traced. Thus, a man will not only apply the term "father" to all the brothers of his father, to all the sons' sons of his father's father, and to all the sons' sons' sons of his father's father's father, to all the husbands of his mother's sisters and of his mother's mother's granddaughters, etc., but he will also apply the term to all the members of his father's clan of the same generation as his father and to all the husbands of the women of the mother's clan of the same generation as the mother, even when it is quite impossible to show any genealogical relationship with them. All these and the other main features of the classificatory system become at once natural and intelligible if this system had its origin in a social structure in which exogamous social groups, such as the clan or moiety, were even more completely and essentially the social units than we know them to be to-day among the peoples whose social systems have been carefully studied. If you are dissatisfied with the word "classificatory" as a term for the system of relationship which is found in America, Africa, India, Australia and Oceania, you would be perfectly safe in calling it the "clan" system, and in inferring the ancient presence of a social structure based on the exogamous clan even if this structure were no longer present.
Not only is the general character of the classi-
