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THE POPULAR SCIENCE MONTHLY 



b D 



Fig. 4. Drawing Test. The up- 

 per drawing when reproduced by chil- 

 dren of different ages indicates their 

 mental development. The first copy 

 shown, drawn by a white female aged 

 eleven years, indicates a mental develop- 

 ment of four years ; the second, by a 

 white female aged sixteen years, a de- 

 velopment of five years ; the third, by a 

 white male aged eighteen years, a de- 

 velopment 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 chil- 

 dren 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 ap- 

 pear 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 sim- 

 plex determiner. 



The committee of eugenics of the 

 American Breeders' Association has es- 

 tablished 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 feeble- 

 minded. It wishes to urge upon every 

 training school the desirability of sup- 



