I can now turn to the second line of attack, that which boldly discards the origin of the terminology of relationship in social conditions, and seeks for its explanation in psychology. The line of argument I propose to follow is first to show that many details of classificatory systems have been directly determined by social factors. If that task can be accomplished, we shall have firm ground from which to take off in the attempt to refer the general characters of the classificatory and other systems of relationship to forms of social organisation. Any complete theory of a social institution has not only to account for its general characters, but also for its details, and I propose to begin with the details. I must first return to the history of the subject, and stay for a moment to ask why the line of argument I propose to follow was not adopted by Morgan and has been so largely disregarded by others. Whenever a new phenomenon is discovered in any part of the world, there is a natural tendency to seek for its parallels elsewhere. Morgan lived at a time when the unity of human culture was a topic which greatly excited ethnologists, and it is evident that one of his chief interests in the new discovery arose from the possibility it seemed to open of showing the uniformity of human culture. He hoped to demonstrate the uniformity of the classificatory system throughout the world, and he was content to observe certain broad varieties of the system and refer them to supposed stages in the history of human society. He paid but little attention to such varieties of the classificatory system as are illustrated in his own record of North American systems, and seems to have overlooked entirely certain features of the Indian and Oceanic systems he recorded, which might have enabled him to demonstrate the close relation between the terminology of relationship and social institutions. Morgan’s neglect to attend to these differences must be ascribed in some measure to the ignorance of rude forms of social organisation which existed when he wrote, but the failure of others to recognise the dependence of the details of classificatory systems upon social institutions is rather to be ascribed to the absence of interest in the subject induced by their adherence to McLennan’s primary error. Those who believe that the classificatory system is merely an unimportant code of mutual salutations are not likely to attend to relatively minute differences in the customs they despise. The credit of having been the first fully to recognise the social importance of these differences belongs to J. Kohler. In his book “Zur Urgeschichte der Ehe,” which I have already mentioned, he studied minutely the details of many different systems, and showed that they could be explained by certain forms of marriage practised by those who use the terms. I propose now to deal with classificatory terminology from this point of view. My procedure will be first to show that