In the Banks Islands the term used between two brothers-in-law is _wulus_, _walus_, or _walui_, and a man who applies one of these terms to another may not utter his name, nor may the two behave familiarly towards one another in any way. In one island, Merlav, these relatives have all their possessions in common, and it is the duty of one to help the other in any difficulty, to warn him in danger, and, if need be, to die with him. If one dies, the other has to help to support his widow and has to abstain from certain foods. Further, there are a number of curious regulations in which the sanctity of the head plays a great part. A man must take nothing from above the head of his brother-in-law, nor may he even eat a bird which has flown over his head. A person has only to say of an object “That is the head of your brother-in-law,” and the person addressed will have to desist from the use of the object. If the object is edible, it may not be eaten; if it is one which is being manufactured, such as a mat, the person addressed will have to cease from his work if the object be thus called the head of his brother-in-law. He will only be allowed to finish it on making compensation, not to the person who has prevented the work by reference to the head, but to the brother-in-law whose head had been mentioned. Ludicrous as some of these customs may seem to us, they are very far from being so to those who practise them. They show clearly the very important part taken in the lives of those who use the classificatory system by the social functions associated with relationship. As I have said, these functions are not universally associated with the classificatory system, but they are very general in many parts of the world and only need more careful investigation to be found even more general and more important than appears at present. Let us now look at our own system of relationship from this point of view. Two striking features present themselves. First, the great paucity of definite social functions associated with relationship, and secondly, the almost complete limitation of such functions to those relationships which apply only to individual persons and not to classes of persons. Of such relationships as cousin, uncle, aunt, father-in-law, or mother-in-law there may be said to be no definite social functions. A school-boy believes it is the duty of his uncle to tip him, but this is about as near as one can get to any social obligation on the part of this relative.