classificatory system are to be referred to different forms of social organisation and to the different degrees in which the regulation of marriage by means of clan-exogamy has been replaced by a mechanism dependent upon kinship or genealogical relationship. From that I was led to refer the general features of the classificatory system to the dependence of this system upon the social unit of the clan as opposed to the family which I believe to be the basis of our own terminology of relationship. I then pointed to several features of the classificatory system which suggest that it arose in that special variety of the clan-organisation in which a community consists of two exogamous moieties, forming the social structure usually known as the dual organisation. I considered more fully the dependence of our own mode of denoting relatives upon the social institution of the family, and then a study of the descriptive terminology of relationship has led me to suggest that certain modes of denoting relationship in Egypt, the Sudan and many European countries may be examples of a third main variety of system of relationship which has arisen out of the patriarchal or extended family. We should thus have three main varieties of system of relationship in place of the two which have hitherto been recognised, having their origins respectively in the clan, in the family in the narrow sense, and in the extended or patriarchal family. These three varieties may be regarded as genera within each of which are species and varieties depending upon
