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ly upon the transmission of mental characteristics. But our knowledge of the dependence of mind upon body should prepare us to infer mental heredity from physical heredity. Such studies as throw light on the question bear us out in making such an inference. The studies that have been more directly concerned with mental heredity are those dealing with the resemblances of twins, studies of heredity in royalty, studies of the inheritance of genius, and studies of the transmission of mental defects and defects of sense organs. The results of all these studies indicate the inheritance of mental characteristics in the same way that physical characteristics are transmitted. Not only are human mental characteristics transmitted from parent to offspring, but they seem to be transmitted in Mendelian fashion. Feeble-mindedness, for example, seems to be a Mendelian character and recessive. From the studies that have been made, it seems that two congenitally feeble-minded parents will have only feeble-minded children. Feeble-mindedness acts in heredity as does the white corn in the example given above. If one parent only is feeble-minded, the other being normal, all of the children will be normal, just as all of the corn, in the first generation after the crossing, was yellow. But these children whose parents are the one normal and the other feeble-minded, while themselves normal, transmit feeble-mindedness in equal ratio with normality. It works out as follows: If a feeble-minded person marry a person of sound mind and sound stock, the children will all be of sound, normal mind. If these children take as husbands and wives men and women who had for parents one normal and one feeble-minded person, their children will be one fourth feeble-minded and three fourths of them normal. To summarize the various conditions: If a feeble-minded person marry a feeble-minded person, all the children will be feeble-minded. If a feeble-minded person marry a sound, normal person (pure stock), all the children will be normal. If the children, in the last case, marry others like themselves as to origin, one fourth of their offspring will be feeble-minded. If such hybrid children marry feeble-minded persons, one half of the offspring will be feeble-minded. It is rash to prophesy, but future studies of heredity may show that Mendelism, or some modification of the principle, always holds true of mind as well as of body. Little can be said about
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