Some Apparent Exceptions 95 



skin, besides factors for red and yellow. The 

 white individual has the same pigments present 

 in the skin but in different proportions. The 

 skin of a tanned brunette appears on micro- 

 scopic examination identical with that of the 

 negro. There are of course other distinctive 

 negro features, like the crinkly hair and broad 

 nose. The two black factors may be designated 

 A and B, and they are present in double dose, 

 so that the chromosomes of a negro would 

 contain AA, BE. The germ cells after reduc- 

 tion must then contain factors A and B. The 

 mulatto (cross of the black and white) would 

 have the same two factors in the body cells 

 both brought in at fertilization by the negro 

 sex cell, while the corresponding white sex cell 

 would contain neither factor. Egg or sperm of 

 a mulatto may therefore conceivably contain 

 A and B, A, B, or neither. The possible 

 resulting combinations when the egg is ferti- 

 lized by a sperm are (construct the checker- 

 board) I AA BB, a fuU-blooded negro; 2 AA 

 B; 2 ABB; 4AB; i AA; i BB; 2 A; 2 B; 

 and one neither A nor B, the latter a pure white. 



