LXII 



BOWMAN LECTURE. 



ascendant of V, 23, in which case the cousinships do 

 not count, for V, 23 was from an outside stock. 



But limitation of the disease to the males and trans- 

 mission through normal females is not invariable. For 



though I believe that an unaffected male never carries 

 colour-blindness, exceptions are found to the other part of 

 the rule. Thus an affected male sometimes transmits to 

 his son, and colour-blindness is sometimes seen in females. 

 The influence, whatever it is, that usually prevents the 

 colour-blind male from passing the defect on to, or 

 through, his sons and compels him to transmit it only 



