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

 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 is 

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

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



