These facts help to explain how the unlimited exogamy which first arises from marriage by capture comes to pass over into a 'limited exogamy,' as it does immediately upon the appearance of conditions that regulate the forceful capture and substitute for it the friendly exchange of women. These factors, however, always come into play whenever the intercourse between tribal members becomes closer, and particularly when the struggle with strange tribes keeps in check the strife between individuals of the same tribal association. In such cases, exchange, or, in later development, purchase, proves the means of putting an end to force. Thus, blood revenge, which persists into far later times, is displaced by the _wergild_ which the murderer pays to the kin of his victim. This transition is precisely the same, in its own field, as that which occurs in the institution of marriage, for in the former case also the strife involves members of the same tribe. The passion, however, which causes the murder and which creates the demand for vengeance, sometimes prevented the introduction of peaceful means of settlement. In the case of marriage by capture, however, a marriage relationship, unrestricted and friendly in character, was doubtless first developed between the two clans, particularly wherever tribal division and clan were identical. And though marriage by capture was for a time still occasionally practised--since all changes of this sort are gradual--such marriages, nevertheless, more and more assumed a playful character. The actual capture everywhere finally gave way to exchange and later to the gift. When, however, the totem groups, and with them the cult associations that established a bond between clan and clan, gained the ascendancy, the totem groups naturally displaced the clan in respect to marriage arrangements; those totems who maintained close cult relations with one another, entered also into a marriage relationship. Thus, exogamy became limited; the members of a totem of clan A married only into the friendly totem of clan B, and this usage became an established norm whose violation might result in the death of the guilty person, unless he escaped this fate by flight. This transition of exogamy from clan to totem group, and from the unlimited to the limited form, came only gradually. This is clearly shown by the conditions among the Dieri. Certain of their totems have already entered upon the stage of limited marriage relationship, whereas others have not advanced beyond unlimited exogamy.