Page:Popular Science Monthly Volume 79.djvu/90

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THE POPULAR SCIENCE MONTHLY

PSM V79 D090 Drawing test indicating mental development.pngFig. 4. Drawing Test. The upper drawing when reproduced by children of different ages indicates their mental development. The first copy shown, drawn by a white female aged eleven years, indicates a mental development of four years; the second, by a white female aged sixteen years, a development of five years; the third, by a white male aged eighteen years, a development of six years, and the fourth, by a white male aged nineteen years, a mental development of seven years. Reduced to one half.

duplex. When the germ cell of one parent only carries the determiner, this is simplex in the embryo. When neither parent carries the determiner the embryo is devoid of it. It follows that, if neither parent has a character none of their children can have it. If both parents have the character in question simplex, one fourth of their children will be without it; one fourth will have the character duplex and half will have it simplex again.
During the past ten years the study of the characters of plants and animals has revealed the nearly universal validity of this law—and during the past two or three years it has been shown to apply to many human qualities.

The law appears clearest in this form—when both parents lack a unit character all of their offspring lack it. Illustrations of this law are seen in the case of brown iris pigment. In case both parents lack it (and have blue eyes), all of their children have blue eyes. In case both parents lack curved hair all of the children have straight hair; if both parents have flaxen hair, the children are all like them; if the parents are blonds, lacking abundant skin pigment, so are their children. If both parents are defective in mental development, being imbecile, their children are all defectives.

When one parent is defective and the other has the additional character the children will have the character; but, since they get it from one side of the house only, the character is apt to appear in a diluted condition. Thus it may be confidently expected that the children of an imbecile and a normal parent will not all be as mentally strong as the stronger parent because their mental development depends on a simplex determiner.

The committee of eugenics of the American Breeders' Association has established headquarters at Cold Spring Harbor in the vicinity of New York City. It desires first to assist in a propaganda for the study of pedigrees of the feebleminded. It wishes to urge upon every training school the desirability of sup-