that for a man merely to see or touch his mother-in-law sufficed to blast the fertility of his wife’s womb, yet he may have thought, with much better reason, that intimate social converse between him and her might easily lead to something worse, and that to guard against such a possibility it was best to raise a strong barrier of etiquette between them. It is not, of course, to be supposed that these rules of avoidance were the result of deliberate legislation; rather they were the spontaneous and gradual growth of feelings and thoughts of which the savages themselves perhaps had no clear consciousness. In what precedes I have merely attempted to sum up in language intelligible to civilized man the outcome of a long course of moral and social evolution. These considerations perhaps obviate to some extent the only serious difficulty which lies in the way of the theory {95} here advocated. [Sidenote: The mutual avoidance between persons of the same sex was probably an extension by false analogy of the mutual avoidance between persons of different sexes.] If the custom of avoidance was adopted in order to guard against the danger of incest, how comes it that the custom is often observed towards persons of the same sex, for example, by a man towards his father-in-law as well as towards his mother-in-law? The difficulty is undoubtedly serious: the only way of meeting it that I can suggest is the one I have already indicated. We may suppose that the deeply rooted beliefs of the savage in the fatal effects of marriage between certain classes of persons, whether relations by blood or connexions by marriage, gradually spread in his mind so as to embrace the relations between men and men as well as between men and women; till he had worked himself into the conviction that to see or touch his father-in-law, for example, was nearly or quite as dangerous as to touch or have improper relations with his mother-in-law. It is no doubt easy for us to detect the flaw in this process of reasoning; but we should beware of casting stones at the illogical savage, for it is possible or even probable that many of our own cherished convictions are no better founded.