The mixing of hereditary units and _blending of heritages_ is shown in the color of the skin, as where a mulatto child is born to a negress by a white father; _mutually exclusive heritages_ are well illustrated in the color of the eyes, as where a child has either the blue eyes of one parent or the black of the other, but never any blending of the colors; this may also be illustrated where the white game bird and black one are crossed, the young being either white or black, but never blended. _Prepotency_ is illustrated where the silky variety of fan-tailed pigeon is mated with any other small-sized variety of pigeon, for the silkiness is invariably transmitted. A most interesting case of prepotency in mankind, mentioned by Ribot, is that of Lislet-Geoffrey, an engineer in Mauritius. He was the son of a very stupid negress and an educated white man. In physical constitution he was as much a negro as his mother; he had the woolly hair, the features, the complexion, and the peculiar odor of his race. He was so thoroughly a white man as regards intellectual development that he succeeded in vanquishing the prejudices of race, so strong in the French colonies, and in being admitted into the most aristocratic houses. At the time of his death he was Corresponding Member of the Academy of Sciences. In this, it will be observed, we have prepotency in the mother’s physical constitution, and in the father’s intellectual characteristics. The struggle of heritages in the impregnated ovum may lead to such structural changes of the nucleus, and therefore of the cell, as to develop the most marked variations—such variations as the biologists call _sports_. In the latter part of the eighteenth century the farmers of Massachusetts had flocks of ordinary sheep on their farms. These sheep were continually jumping fences and getting on neighboring farms. They were the source of many disputes and much irritation between neighboring farmers. Finally, one of the sheep had a lamb which, when grown, displayed well-marked peculiarities (a sport). It had a longer body than the ordinary sheep and shorter legs, which were bowed. It was noticed that this sheep could not get over the fences. The cute Yankee farmer, noticing this valuable peculiarity, carefully preserved this peculiar sheep, and from it was ultimately derived, by careful selective breeding, a special variety known as the Ancon sheep. The germinal variations resulting from the mixing of two separate hereditary masses by impregnation find their expression in the most varied qualities of the minds and bodies of developing children. If the variations are not especially marked, they are looked upon as normal and attract no special attention. But if the variations are so pronounced as to compel attention, and at the same time it is known that they are useful, they are spoken of as talents, or, on the other hand, if they are harmful or useless, they are designated as pathological or monstrosities.