women of one moiety, and B and b for those of the other moiety, shows that a marriage between a man and his son's daughter would be out of the question, for it would be a case of A marrying a. It was evident that the marriage, the consequences of which I had to formulate, must have been one in which a man married his daughter's daughter.

It would take too long to go through the whole set of relationships, and I choose only a few examples which I illustrate by the following diagram :

This diagram shows that if A marries e, c, who previous to the marriage had been only the daughter of A, now becomes also his wife's mother; and D, who had previously been his daughter's husband, now becomes his wife's father. Similarly, F, who before the new marriage was the