276 HEREDITY AND ENVIRONMENT 



to produce a color blind male, just as is true 

 of sex. The accompanying diagrams (Figs. 

 61, 62) illustrate the method of inheritance of 

 color blindness. As in the previous diagrams 

 X represents the sex-determiner, @ its absence, 

 and X the sex-determiner which carries the 

 factor for color blindness. 



It will be seen that a color blind father and a 



Fig. 61. Diagram of inheritance of color blindness througl) 

 the male. A color blind male (here black) transmits his 

 defect to his grandsons only. The corresponding distribution 

 of the sex chromosomes is shown on the right, the one carry- 

 ing the factor for color blindness being black. (After 

 Morgan.) 



