The late Mr. McLennan was the first to call attention to the general prevalence of the rule which forbids the members of a tribe (or clan) to intermarry with members of their own tribe (or clan). This rule he called “exogamy,” in contradistinction to “endogamy,” or the rule which forbids the members of a tribe to intermarry with members of other tribes. In his celebrated essay on ‘Primitive Marriage’ he made an attempt to show that exogamy had arisen from female infanticide, “common among savages everywhere.” He assumes that to tribes surrounded by enemies, and unaided by art, contending with the difficulties of subsistence, sons were a source of strength, both for defence and in the quest for food, whilst daughters were a source of weakness. Hence the cruel custom which left the primitive human hordes with very few young women, thus seriously disturbing the balance of the sexes within the hordes, and forcing them to prey upon one another for wives. Usage, induced by necessity, would then in time establish a prejudice among the tribes observing it—a prejudice strong as a principle of religion, as every prejudice relating to marriage is apt to be—against marrying women of their own tribe.[1859] Mr. Herbert Spencer has subjected this hypothesis to a searching criticism,[1860] and from an article in the ‘Fortnightly Review’ it appears as if Mr. McLennan himself had in the end some doubts as to its correctness.[1861] To Mr. Spencer’s objections others might be added. A minute investigation of the extent to which female infanticide is practised has convinced me that Mr. McLennan has much exaggerated the importance of this custom. It certainly prevails in many parts of the world; and it is true that, as a rule, female children are killed rather than male. But there is nothing to indicate that infanticide has ever been so nearly universal, or has anywhere been practised on so large a scale as Mr. McLennan’s hypothesis presupposes. Among a great many existing savage peoples it is almost unheard of—as, for instance, among the Tuski,[1862] Ahts,[1863] Western Eskimo,[1864] Botocudos,[1865] and in certain tribes of California.[1866] Among some of these peoples new-born children are killed now and then—in case of the birth of twins, if the children are weak and deformed, or for some other reason—but always, it is said, without distinction of sex. Among the Dacotahs and Crees, female infanticide is only occasionally committed.[1867] The Blackfeet, according to Richardson, believe that women who have been guilty of this crime will never reach the happy mountain after death, but are compelled to hover round the seats of their crimes, with branches of trees tied to their legs;[1868] and the Aleuts think that a child-murder brings misfortune on the whole village.[1869] Among the Abipones, the women often practised infanticide, but it was the boy who was generally thus sacrificed, for when a son grew up it was necessary to buy a wife for him, while a