Instinctive aversion among animals to pairing with individuals belonging to another species, pp. 278-280.—Infertility of first crosses and of hybrids, pp. 279, _et seq._—‘The Law of Similarity,’ p. 280.—Bestiality, pp. 280, _et seq._—The various human races said to have an instinctive aversion to intermingling, pp. 281, _et seq._—Intermixture of races, pp. 282, _et seq._—Its effects on fertility, pp. 283-288.—Rejection of M. Broca’s theory as to the infertility of the connections of Europeans with Australian women, pp. 284-287.—The doctrine of the unity of mankind independent of the degree of fertility of first crosses, and of mongrels, pp. 288, _et seq._ CHAPTER XIV PROHIBITION OF MARRIAGE BETWEEN KINDRED The horror of incest almost universally characteristic of mankind, p. 290.—Intercourse between parents and children, pp. 290, _et seq._—Between brother and sister, pp. 291-294.—Between half-brother and half-sister, pp. 294, _et seq._—Between uncle and niece, and aunt and nephew, pp. 295, _et seq._—Between first cousins, pp. 296, _et seq._—The prohibited degrees among peoples unaffected by modern civilization more numerous, as a rule, than in advanced communities, pp. 297-309.—Prohibition of marriage between relatives by alliance, pp. 309, _et seq._—Early hypotheses as to the origin of the prohibitions of marriage between near kin, p. 310.—Criticism of Mr. McLennan’s hypothesis as to the origin of exogamy, pp. 311-314.—Criticism of Mr. Spencer’s views, pp. 314, _et seq._—Of Sir John Lubbock’s, p. 316.—Of Professor Kohler’s, pp. 316, _et seq._—Of Mr. Morgan’s, &c., pp. 318, _et seq._—The prohibition of incest founded not on experience, but on instinct, p. 319. CHAPTER XV PROHIBITION OF MARRIAGE BETWEEN KINDRED (_Concluded_)