From early times on, the phenomena of totemism have been accompanied by certain _forms of tribal organization_. Every tribe is first divided, as a rule, into two halves. Through a further division, a fairly large number of clans arise, which, in turn, eventually split up into subclans and separate totem groups. Each of these groups originally regarded some particular totem animal or other totem object as sacred. The most important social aspect of this totemic tribal organization, however, consists in the fact that it involved certain norms of custom regulating the intercourse of the separate groups with one another. Of these norms, those governing marriage relations were of first importance. The tribal organization of this period was bound up with an important institution, _exogamy_, which originated in the totemic age. In the earliest primitive period every tribal member could enter into marriage with any woman of the tribe whom he might choose; according to the Veddahs, even marriage between brother and sister was originally not prohibited. Thus, endogamy prevailed within the primitive horde. This, of course, does not mean that there was no marriage except within the narrow circle of blood relationship, but merely that marriage was permitted between close relatives, more particularly between brothers and sisters. The exogamy characteristic of totemic tribal organization consists in the fact that no marriages of any kind are allowed except between members of different tribal divisions. A member of one particular group can enter into marriage only with one of another group, not with a person belonging to his own circle. By this means, totemic tribal organization gains a powerful influence on custom. Through marriage it comes into relation with all phenomena connected with marriage, with birth and death and the ideas bound up with them, with the initiation ceremonies in which the youths are received into the association of men, etc. As a result of the magical significance acquired by the totem animal, special associations are formed. These become united under the protection of a totem animal and give impetus to the exoteric cult associations, which, in their turn, exercise a profound influence upon the conditions of life. Though it is probable that these associations had their origin in the above-mentioned men's clubs, their organizing principle was the totem animal and its cult.