RESPONSES OF YOUNG TOADS 



189 



V. RESPONSE TO WEAK DIFFUSE DAYLIGHT 



A number of experiments were performed with weak diffuse 

 daylight. The light was obtained from a south window. The 

 incoming rays passed through a small slit-like opening in the 

 wall of the dark room before reaching the experimentation 

 dish. The length of the opening corresponded with the width 

 of the vessel and the width of the former was equal to the depth 

 of the latter. The window through which the light entered 

 was 4 m. distant from the dark room (see Fig. i, A). 



A 



B 



Figure 1. A. Sectional diagram showing plan of apparatus employed in testing 

 responses of young toads to stimulation from weak diffuse daylight. B. Ex- 

 perimentation dish enlarged more than is shown in A. a, Interior of dark 

 room; b, walls of dark room; c, experimentation dish containing young 

 toads; d. table; e, opening through which light enters dark room; f, window 

 through which light enters, situated in wall of outer room; +, positive; 

 — , negative; 0, indifferent. (Not drawn to scale.) 



The glass trough containing the toads was placed in close 

 proximity to the slit-like opening. It was noticed that there 

 was no immediate response to the light, neither by orientation 

 nor by movement toward or away from the source of illumina- 

 tion. This being the case observations were taken every fifteen 

 minutes, and the positions of the animals in the dish noted. The 



