SEX-LINKED INHERITANCE 109 



(or any other sex-linked character) hi Drosophila, 

 for the O-sperm in man would be equivalent to the 

 I^-sperm in the fly. 



Painter's later evidence {fig. 47), showing that 

 there is a small I^-chromosome in the male that acts 

 as the mate of the A"-chromosome {fig. 48), is very 

 convincing. Whether in man the male is XO or XY 

 the explanation of sex-linked inheritance is the same 

 since the factors involved are carried bv the X- 

 chromosomes. 



