It is essential, also, to remember that it is the inferior race only which reaps the psychical advantage. Compared to the parent of the higher race, the children are a deteriorated product. Only when contrasted with the average of the lower race can they be expected to take some precedence. The mixture, if general and continued through generations, will infallibly entail a lower grade of power in the descendant. The net balance of the two accounts will show a loss when compared with the result of unions among the higher race alone. This consideration has led a recent writer, Dr. Reibmayr, to a theory of ethnic mental development which merits close attention. A family, tribe, caste, or race, to preserve and increase its faculties must sedulously avoid intermarriage with one of inferior gifts. The value of “breeding in-and-in” is familiar to all interested in the improvement of the lower animals. This was attained in primitive life by the tribal law of endogamous marriages, by which a man must take his wife within the tribe, but not of his immediate blood. The superiority which this developed led to the subjection of other tribes, and this, through capture and enslavement of the women, to intermixture of blood, with its above mentioned first consequences: deterioration of power in the captors, and, next, elevation of the lower, conquered tribe. The former was sometimes counteracted by the maintenance of purity of blood in a portion of the community, which thus became the ruling class; and if this did not take place, the tribe itself soon fell beneath the sway of some neighbour which had maintained its lineage more purely. Thus, says Dr. Reibmayr, the history of human mental development is, in fact, the history of human hybridity and its necessary consequences. Thus it appears that the reciprocal action of these two genetic processes, the one of close and closer interbreeding, the other of wide and wider intermixture of blood, is the prime element in modifying the psychical faculties,—in other words, in creating and moulding the ethnic mind. How weighty this consideration becomes when we reflect that throughout historic times, that is, from the earliest dawn of civilisation, the subspecies of man have ever been as clearly contrasted in every feature as they are to-day! The oldest monuments of Egypt and Assyria show their portraits as typical as if carved or painted yesterday. No boreal fountain can wash the Ethiopian white; no kisses of tropical Phœbus could turn Cleopatra black. We are constrained to adopt, therefore, the principle formulated by Orgeas, that, so far as history knows, “the races of men have never altered their traits except through intermarriage.”