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

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

 by the 16'^ black symbol from the left in generation vii. 



Black symbols show the night-blind individuals. The descent i 

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

 theless the table gives a remarkable illustration of the permanence and 



