THE MAMMALIAN EYE 255 



ual discrimination normal focal distances for all the animals 

 used if our results are to be at all trustworthy; second, if the 

 conditions so nearly approach those of peripheral vision, the 

 stimulus should preferably be a moving one; third, the light 

 conditions should be those to which the animal is best adapted; 

 and fourth, we should not expect sharp discrimination of form 

 from eves such as those we have described. 



