dition of sexual communism to one in which sexual relations are restricted to the partners of a marriage. Such psychological factors as come into action are only intermediate links in a chain of causation in which the two ends are definitely social processes or events, or, perhaps more correctly, psychological concomitants of intermediate links which are themselves social events. We should be shutting our eyes to obvious features of these Melanesian customs if we refused to recognise that the terminology of relationship here "reflects" sociology.
This leads me to question for a moment whether it may not be the same with that custom of our own society which Professor Kroeber has taken as his example of the psychological causation of the terminology of relationship. Is it as certain as Professor Kroeber supposes that the classing of the brother-in-law with the brother, or of the sister-in-law with the sister, among ourselves does not reflect sociology? We know that there are social factors at work among us which give to these relationships, and especially to that of wife's sister, a very great importance. If instead of stating dogmatically that this feature of our own terminology is due to the psychological similarity of the relationships, Professor Kroeber's mind had been open even to the possibility of the working of social causes, I think he might have been led to inquire more closely into the distribution and exact character of the practice in question. He might have
