PEARSE. — THE REACTIONS OF AMPHIBIANS TO LIGHT. 



181 



of exactly this kind have been made on amphibians, although Torelle 

 (:03, p. 474) found that a frog went toward the light with the long 

 axis of the body oblique to the direction of the rays, or made circus 

 movements, after one eye had been covered. She made no attempt, 

 however, to stimulate the eye without also affecting the skin. 



jfc, 



A B 



Figure 4. A, front sectional view through the middle of the apparatus 

 for testing eyeless frogs under unilateral stimulation; B, sectional view from 

 the side, a, wooden support for heat screen, which contained an oblong 

 opening; c, adjustable screen of blackened sheet iron; I, source of light; 

 s, black cardboard screen ; w, glass dish containing water. 



From these experiments it is apparent that the photic reactions of the 

 toad, which are brought about by stimulation through the eyes, are due 

 to intensity differences in the illumination of the two eyes, and the 

 direction of the light rays is apparently of no significance. 



