46 HEREDITY OF SKIN COLOR IN NEGRO-WHITE CROSSES. 



narrow noses, and, as is well known, with many or all the inhibitions 

 and educability of the Caucasians. And, also (and this is of great and 

 increasing moment), we have white-skinned persons not only with 

 negroid features but with that lack of inhibitors, that absence of 

 educability, that characterizes the typical west coast African. From 

 a social point of view one may suggest that it had been better for 

 society had it been possible to find some simple criterion of mental 

 inferiority that is as conspicuous as skin color. Then we could have 

 separate cars and schools for the feeble-minded without regard to 

 skin color, as we now have, on railroad lines that run from a great city 

 to suburban state hospitals, special cars for the insane, and, in most 

 large northern cities, special schools for the mentally retarded. 



H. FECUNDITY OF HYBRIDS. 



There is an ancient tradition that mulattoes are unprolific. This 

 was affirmed by Long (1774), who stated that he had never heard of 

 a union of two mulattoes in Jamaica that was prolific; and Nott de- 

 clared that mulattoes, at least of South Carolina, were unprolific. 

 Broca's (1864) great argument against the unity of the human species 

 was based on the assertion that human "hybrids" were sterile. This 

 matter has been considered recently by Fischer (1911, 1912), who 

 finds that the number and vigor of the hybrids of the Boers and Hot- 

 tentots has not suffered any decline. In such hybrids "die durch- 

 schnittliche Zahl pro Ehe ist y.7; die Sterblichkeit ist nichts grosser 

 in Verwandten- und Insuchtsehen, der Gesundheitszustand um nichts 

 schlechter." 



Our own records afford no support to the view of the inferior 

 fecundity of the black X white crosses. Even Fi crosses are fully 

 fecund. Referring to table 19 we find four certain fraternities of F x 

 hybrids. They have respectively 12, 1, and 9 children. Case B XXI 

 is particularly instructive. The mother had 1 1 children at an average 

 interval of less than two years. Nine of these were seen by the field 

 worker; none had died! Taking table 19 as a whole, there are 88 chil- 

 dren to 21 matings or an average of 4.4 children to a fraternity; which 

 is equal to the average fecundity of all the matings. There is no sup- 

 port in our data for the notion of lack of fecundity of negro X white 

 crosses, nor of their deficient viability. 



I. SUMMARY OF CONCLUSIONS. 



By the use of quantitative methods of expressing skin color and 

 by means of the study of complete families, it is possible to get at the 

 law of inheritance of skin color in negro X white crosses. 



Skin pigmentation develops chiefly after birth (i.e., from the begin- 

 ning of exposure of the skin to daylight), attaining its maximum at 

 about the age of puberty, and then diminishing in intensity. 



