Marriage by purchase, however, does not represent the terminus of the development. On the contrary, it prepares the way for _marriage by contract_, an important advance that was already, to a certain extent, made by the Greeks, and later particularly by the Romans. Not purchase, but a contract between him who concludes the marriage and the parents of the woman--this is an arrangement which still finds acceptance with us to-day. Now, the marriage contract determines the conditions for both bride and groom, and eventually also the marriage portion which the man brings to the union, as well as the dowry of the wife. As soon, therefore, as property considerations come to be dominant within the field of marriage, marriage by contract opens the way for a twofold marriage by purchase. The man may either buy the woman, as was done in the case of the earlier marriage by purchase, or the woman may buy the man with the dowry that she brings. At first, in the days of marriage by capture, the struggle with fellow-clansmen or with strangers was of decisive importance; at a later time, however, differences in property, rank, and occupation came to be the determining factors in the case of marriage. Thus, if we regard marriage by gift as a mode of marriage by purchase, though, in part, more primitive, and, in part, more spontaneous, our summary reveals three main stages: _marriage by capture, marriage by purchase_, and _marriage by contract_. Between these modes of marriage, of course, there are transitional forms, which enable us to regard the course of development as constant. The fact, however, that the entire development bears the character of a more or less thorough-going exogamy, is due to the _oldest_ of these modes of marriage--a mode which, as we may assume, was prevalent at the beginning of the totemic age. This is a form of marriage by capture in which the woman belonged, not to a strange tribe, but to a neighbouring clan of the same tribe, or to one with which there were other lines of intercourse. When capture disappeared, the exogamy to which it gave rise remained. The old customs connected with the former passed over, though more and more in the form of play, into the now peaceful mode of marriage by purchase; their survivals continued here and there even in the last form of marriage, that by contract. 6. THE CAUSES OF TOTEMIC EXOGAMY.