the details which distinguish different forms of the classificatory system from one another have been directly determined by the social institutions of those who use the systems, and only when this has been established, shall I attempt to bring the more general characters of the classificatory and other systems into relation with social institutions. I am able to carry out this task more fully than has hitherto been possible because I have collected in Melanesia a number of systems of relationship which differ far more widely from one another than those recorded in Morgan’s book or others which have been collected since. Some of the features which characterise these Melanesian systems will be wholly new to ethnologists, not having yet been recorded elsewhere, but I propose to begin with a long familiar mode of terminology which accompanies that widely distributed custom known as the cross-cousin marriage. In the more frequent form of this marriage a man marries the daughter either of his mother’s brother or of his father’s sister; more rarely his choice is limited to one of these relatives. Such a marriage will have certain definite consequences. Let us take a case in which a man marries the daughter of his mother’s brother, as is represented in the following diagram: [Illustration: DIAGRAM 1[8] [8] In this and other diagrams capital letters are used to represent men and the smaller letters women. +----------------------------+ | | B = a A = b | | | +----------+----------+ | | | | C =================== d E f ] One consequence of the marriage between _C_ and _d_ will be that _A_, who before the marriage of _C_ was only his mother’s brother, now becomes also his wife’s father, while _b_, who before the marriage was the mother’s brother’s wife of _C_, now becomes his wife’s mother. Reciprocally, _C_, who before his marriage had been the sister’s son of _A_ and the husband’s sister’s son of _b_, now becomes their son-in-law. Further, _E_ and _f_, the other children of _A_ and _b_, who before the marriage had been only the cousins of _C_, now become his wife’s brother and sister. Similarly, _a_, who before the marriage of _d_ was her father’s sister, now becomes also her husband’s mother, and _B_, her father’s sister’s husband, comes to stand in the relation of husband’s father; if _C_ should have any brothers and sisters, these cousins now become her brothers- and sisters-in-law. The combinations of relationship which follow from the marriage of a man with the daughter of his mother’s brother thus differ for a man and a woman, but if, as is usual, a man may marry the daughter either of his mother’s brother or of his father’s sister, these combinations of relationship will hold good for both men and women.