When the instinct for association developed more strongly, the differences due to age, plus the physiological factor, conditioned the natural formation of two classes,—one of men before puberty, and one of men after puberty. This natural twofold division was also strengthened by another factor; for until the age of puberty, boys were under the influence of women, and were therefore to be reckoned as one with them. The three groups—men before puberty, unmarried men after puberty, and married men—are thus built upon the basis of age distinction and common interest. They are the norms of primitive social organization, and, as we have seen, their origin is due to inherited instincts. By implication Schurtz has here also assumed the existence of a definite sequence; for the division into pre- and post-puberty groups is a consequence of the sexual instinct, and is therefore primary. Differentiation into the groups of married and unmarried men thereupon followed; but the initiation, which is synchronous with the age of sexual maturity, has introduced another factor, that of promiscuous sexual intercourse; and the regulation that this has demanded is found outwardly expressed in the “men’s house.” The common interests that drew men together into groups have thus far been those conditioned largely by age. In the development of society, however, interests became more and more diversified, and resulted, first, in the disappearance of the age factor as the essential element for associations, and, secondly, in the necessity for more closely organized units with specific characteristics. To obtain this close organization, one of the essential elements was secrecy, and thus developed out of the “men’s house” those innumerable clubs and secret societies which we find so common to-day.