Here we see longitudinal and transverse integration going on simultaneously; and in the highest crustaceans they are both carried still further. The _Vertebrata_ clearly exhibit transverse integration in the development of the generative system. The lowest of the mammalia—the _Monotremata_—in common with birds, to which they are in many respects allied, have oviducts which towards their lower extremities are dilated into cavities, severally performing in an imperfect way the function of a uterus. “In the _Marsupialia_ there is a closer approximation of the two lateral sets of organs on the median line; for the oviducts converge towards one another and meet (without coalescing) on the median line; so that their uterine dilatations are in contact with each other, forming a true ‘double uterus....’ As we ascend the series of ‘placental’ mammals, we find the lateral coalescence becoming more and more complete.... In many of the _Rodentia_ the uterus still remains completely divided into two lateral halves; whilst in others these coalesce at their lower portions, forming a rudiment of the true ‘body’ of the uterus in the human subject. This part increases at the expense of the lateral ‘cornua’ in the higher herbivora and carnivora; but even in the lower quadrumana the uterus is somewhat cleft at its summit.”[10] In the social organism integrative changes are not less clearly and abundantly exemplified. Uncivilized societies display them when wandering families, such as the bushmen show us, unite into tribes of considerable numbers. Among these we see a further progress of like nature everywhere manifested in the subjugation of weaker tribes by stronger ones; and in the subordination of their respective chiefs to the conquering chief. The partial combinations thus resulting, which among aboriginal races are being continually formed and continually broken up, become, among the superior races, both more complete and more permanent. If we trace the metamorphoses through which our own society, or any adjacent one, has passed, we see this unification from time to time repeated on a larger scale and with increasing stability. The aggregation of juniors and the children of juniors under elders and the children of elders; the consequent establishment of groups of vassals bound to their respective nobles; the subordination afterwards established of groups of inferior nobles to dukes or earls; and the still later establishment of the kingly power over dukes or earls; are so many instances of increasing consolidation. This process through which petty tenures are combined into feuds, feuds into provinces, provinces into kingdoms, and finally contiguous kingdoms into a single one, slowly completes itself by destroying the original lines of demarcation. And it may be further remarked of the European nations as a whole, that in the tendency to form alliances more or less lasting, in the restraining influences exercised by the several governments over