Sex totemism, similarly to conception totemism, is also of somewhat limited distribution, and seems to occur principally in those regions where tribal totemism proper is lacking or is at least strongly recedent. Among the Kurnai of southern Australia, for example, no tribal totemism has been discovered, though sex totemism occurs and actually forms the basis of certain marriage ceremonies. Sex totemism probably has its origin in the individual totem, especially in the appearance of this totem in dreams. If, after such a totem has appeared to an individual man or woman, it is then adopted by others of the same sex, specific sex totems may well come into being, particularly under the influence of the separate associations of men and women. It is also significant that in the case of sex totemism nocturnal animals predominate. The totem of the women is usually the bat; that of the men, the owl. This fact is indicative of a dream origin and of a genesis from the individual totem. Diurnal birds may, of course, also appear in dreams. Whether or not this occurs depends solely upon concomitant circumstances. At the stage of culture, however, when man is accustomed to sleep in the open, it is probable that the nocturnal birds which circle about him will also appear in his dreams. A further characteristic phenomenon of the regions where sex totemism prevails, is the manner in which marriage is consummated. In this case also, the woman eats of the totem of the man. This causes a struggle between the man and the woman, which is really a mere mock-fight ending with an offer of reconciliation on the part of the man. With this, the marriage is concluded. Such customs likewise point back to individual totemism as their original source, and probably also to marriage by capture. The fact that tribal totemism everywhere receded with the dominance of individual totems, explains why sex and tribal totemism seem to be mutually exclusive. Of the two rare forms of totemism, accordingly, it is probable that conception totemism was the earlier, and that sex totemism belongs to a relatively late stage of development. A further indication of the primitive nature of conception totemism is to be found in the fact that the Aranda possess a tribal organization in which the grouping of totems to form clan divisions follows a principle which elsewhere obtains only in the case of the two tribal halves. Two clans, A and B, that enjoy exogamous relations with each other, do not have different totem groups, as they do among all other tribes; their totem groups are largely the same. Among the Aranda, therefore, a man of one totem may, under certain circumstances, marry a woman of the same totem, provided only she belongs to the other clan. True, phenomena are not lacking--such particularly as those of plant totems, to be mentioned below, and the ceremonial festivals connected with them--which indicate that these northern tribes were affected by Papuan immigrations and by race-mixture. But influences of this kind are the less apt to lead to the submergence of primitive views and customs according as they are instrumental, particularly when they are operative at an early age, in maintaining conditions which might otherwise possibly disappear as a result of further development.