Amongst marriage customs that which has given rise to most discussion as regards its origin is ‘Exogamy’ or marriage outside the family group, or outside the limit of the totem name. My general argument, as will be seen, places me in antagonism with all theories yet advanced on the subject. But Mr. Lang, in _Custom and Myth_, 1884 (p. 258), hazards, as his own impression, a conception of this matter which I will note--namely, that ‘Exogamy, may be connected with some early idea of which we have lost touch,’ and he adds, ‘If we only knew the origin of the prohibition to marry within the _family_[3] all would be plain sailing.’ However utterly beyond human ken, in these our latter days, any truthful image of so remote a past may seem to be, it is yet precisely this hypothetic early idea which I hope to be able to expose. (If I am correct, we shall find that it was connected with the sexual relations of primitive man, _whilst in the animal stage_, and especially with the mutual marital rights of the males within a group.) Such idea in travail, hastened and sharpened by needs of environment, created issues which necessarily gave birth to a ‘Primal Law’ prohibitory of marriage between certain members of a family or local group, and thus, in natural sequence, led to _forced_ connubial union _beyond_ its circle the family, or local group--that is, led to Exogamy. But if such was in reality the original order of succession in the growth of custom, it becomes evident that Exogamy as a _habit_ (not as an expressed law) must have been of primordial evolution. Thus (in contra-distinction to generally received opinion and to Mr. McLennan’s theory in particular) Exogamy must have been a cause rather than an effect in relation to its ordinary concomitants, i.e. Female Infanticide as a custom, Polyandry as a fixed institution, and Totemism as connected with exogamous groups, within which marriage was forbidden. As thus my new hypothesis finds itself in opposition to those of recognised authorities, it is evident that it will require to account for all the facts if it is to hold its ground. However convinced the author may be by the array of seemingly confirmatory details in favour of his hypothesis, it is possible that from their paucity they may yet to others seem to constitute but a feeble line of defensive proof. But if the theory shall prove in itself to have merit, this defect (arising, as I believe, from lack of general anthropological knowledge on my part, for I dwell ‘far from books’) will quickly be remedied, for a hundred other details in favour of my view will be at once perceived by more experienced students. Should my hypothesis really furnish the clue to the problem of the prohibition to marry within the family name, or totem name, all the rest will doubtless become ‘plain sailing’ in competent hands.