284 HEREDITY AND ENVIRONMENT 



and not to his sons the sex-determiner which 

 carries the factor for color blindness. But 

 since color blindness does not develop in fe- 

 males unless it is duplex (i.e. comes from both 

 father and mother) whereas it develops in 

 males if it is simplex (i.e. comes from either 

 parent) all the daughters of a color blind 

 father and normal mother will appear normal 

 although carrying one determiner for color 

 blindness, while all the sons will be normal be- 

 cause they carry no determiner for color blind- 

 ness. But these daughters transmit to one-half 

 of their children the single determiner for color 

 blindness and if any of those receiving this de- 

 terminer are males they will be color blind- 

 Consequently we have the curious phenome- 

 non of simplex color blindness appearing only 

 in males and being transmitted to them only 

 through apparently normal females. 



On the other hand if a female is color blind 

 she has inherited it from both father and 

 mother, i.e. the character in her is duplex, and 

 in all of her children by a normal male the 

 character will be simplex; accordingly all of 

 her sons will be color blind and all of her 



