HUMAN INHERITANCE 277 



In a cross between a negro and a white person, children are 

 produced of an intermediate, but frequently variable skin- 

 color, and are known as mulattoes. Mulattoes mating inter se 

 produce an Fo generation of highly variable skin-color but 

 rarely pure white. Davenport has concluded that two inde- 

 pendent Mendel ian factors affecting skin-color are involved. 

 This explanation would lead us to expect one in sixteen of the 

 Fi mulatto offspring to have skin as white as a European, 

 even though his negro ancestry might show in other charac- 

 teristics, such as curly hair, broad nose, thick lips, etc. It is 

 difficult to get any wholly satisfactory evidence either for or 

 against this explanation. That published by Davenport can 

 scarcely be considered conclusive, for the data studied are 

 derived from a population in which illegitimacy, by Daven- 

 port's own statement, is as high as 72 per cent. On the 

 whole, it seems probable that segregation of skin pigmenta- 

 tion in mulattoes is either incomplete or rarely complete, be- 

 cause multiple or modifying factors are involved. 



A clearly and sharply defined Mendelian factor which in- 

 volves spotting with white occurs in many human families, 

 as in domesticated animals. In some families a lock of white 

 hair (usually above the middle of the forehead, or on top of 

 the head) is inherited as a Mendelian dominant (transmitted 

 only through affected individuals). Irregidar spotting of the 

 body with unpigmented areas has been shown to be heredi- 

 tary as a dominant character in a family of Louisiana negroes 

 (exhibited in Europe and America), and a similar variation 

 is inherited in the same way in a white family in Minnesota, 

 one or more of whom have studied at the University of 

 Minnesota. 



