In the gradual evolution of the group into the tribe during the long period of transition, the modifications in the internal organisation, which took place as the necessary result in the march in progress, should have left traces which we may also be able to follow in living custom. The immigration of the outside suitor, in its synchronism with the decay of paternal incest, must have entailed continual complications demanding regulation, and the resolution of each problem would lead to an almost mechanical step in advance. When by force of circumstances of environment or others such a step became retrograde, then we may expect an aberrant form whose very anomalism should lead to a facile recognition, and prove equally fertile in interpretation. Indeed, a curious vestige of the effect in action of the habit of incest, when brought into inevitable contact with progressive social evolution, is to be discerned in the nomenclature of that earliest phase of the classificatory system which Mr. L. H. Morgan has called the Malayan. From the general prevalence among lower races of a division into classes by generations of the members of group, and the deduction we see drawn in _Ancient Society_ from the Hawaiian terms of relationship therein detailed, as to a previous state of general promiscuity, it will be desirable thoroughly to examine the whole question of the so-called classificatory system. It is doubly imperative in view of our own hypothesis, which, as regards the primary origin of society, may be said to be exactly the reverse of that of Mr. Morgan, in as far as the sexual inter-relations of brother and sister are concerned.