52 HEREDITY AND EUGENICS 



lipochrome (a group of animal-fat pigments), while 

 the brown is a melanin (a dark pigment found in hair, 

 etc.); and (3) the generalisation of the Davenports 

 (1910) that (with rare exceptions) children never 

 have darker hair than their darker parent. This 

 '' non-transgressibility of the upper limit " applies 

 also to skin colour or complexion in the white races. 

 Davenport (191 3), from a study of mulatto families 

 in Bermuda, Jamaica, and the United States, con- 

 cluded that there are probably two segregating 

 Mendelian factors for black, and that other negroid 

 features, such as kink}^ hair and thick lips, segregate 

 independently. The same would appear to be true for 

 mental characters, since mulattoes sometimes display 

 high intellectual ability, but never pure negroes, as 

 far as is known. 



The evidence in favour of a strictly Mendelian ex- 

 planation of colour inheritance in white-black crosses 

 is, however, by no means conclusive. Pearson (1909), 

 from data supplied b}^ a medical man in the West 

 Indies, gives quite a different picture. The first cross 

 gives a brown mulatto or a yellow mulatto, and the 

 basis or cause of this difference is not apparent. In 

 crosses between mulattoes " there are now and then 

 slight variations from the usual mulatto brown or 

 mulatto yellow," but never pure black or white. 

 Sports or throwbacks rarely occur, but the form 

 where the tint is barely evident is said to be not 

 uncommon. Mulatto x negro produces the sambo, 

 a deep mahogany brown, and it is said there is never 

 any other colour from this cross. Mulatto x white 

 produces the quadroon, which is never pure white, 

 but almost invariably lighter than the brown mulatto 

 and nearly always lighter than the yellow mulatto. 

 This gives the impression of intermediac}^ in the 

 various hybrid conditions, with a not very marked 

 tendency to segregation, which is never complete. 



