THEORY OF EVOLUTION 125 



In man there are several characters that show 

 exactly this same kind of inheritance. Color 

 blindness, or at least certain kinds of color 

 blindness, appear to follow the same scheme. A 

 color blind father transmits through his daugh- 

 ters his peculiarity to half of liis grandsons, 

 but to none of his grand-daughters (fig. 38A) . 



Diploid Nuclei XX 



Gametes 

 Fertilizat-Jon 

 Zygotes 



Fig. go. Diagram of sex deterininatinn in type with XX 

 female and XO male (after Wilson). 



The result is the same as in the case of the white 

 eyed male of Drosophila. Color blind women 

 are rather unusual, wliich is expected from the 

 metliod of inheritance of this character, but in 

 the few known cases where such color blind 

 women have married normal husbands the sons 

 liave inherited the peculiarity from the mother 

 (fig. 38B) . Here again the result is the same 

 as for the similar combination in Drosophila. 



