32 



Fig. 31. Descent of a form of stationary night-blindness. (Condensed from 

 Only those families which contain affected members are here set out in det 

 by the i6 th black symbol from the left in generation vn. 



Black symbols show the night-blind individuals. The descent is al 

 According to the records there is a great excess of normals over the affect 

 theless the table gives a remarkable illustration of the permanence and mo 



