182 C. F. CURTIS RILEY 



Water with a temperature approximately of 22 C. is poured 

 into the glass receptacle to a depth of 4 cm. The animals are 

 then placed in the water and the vessel moved into the beam of 

 light emerging from the projection lantern. The organisms 

 immediately orient themselves with the longitudinal axis of the 

 body parallel to the rays of light. Complete orientation is 

 quickly followed by every animal swimming vigorously away 

 from the source of illumination to the extremity of the dish. 

 The young toads retain their precision of orientation as they 

 move through the water for the entire length of the vessel. 

 After all the animals have assembled at the end of the dish, it 

 is turned around, thus placing the organisms again nearest the 

 source of light.- The animals as before 'respond promptly, swim- 

 ming to the far end of the vessel. In this connection it may be 

 mentioned that Torelle (1903, p. 473) while engaged with some 

 very interesting experiments, demonstrated that in water Rana 

 virescens and Rana clamata move to the illuminated end of a 

 glass trough. Diffuse daylight was used in these experiments. 

 Many consecutive experiments of the nature of the above 

 were performed, the toads orienting themselves each time in 

 such a manner that the long axis of the body becomes parallel 

 to the rays of light ; and they swim away from the source of 

 illumination as already explained. Frequently after reaching 

 the extremity of the glass trough, many of the toads climb up 

 its. perpendicular wall. Attention has been drawn to this move- 

 ment in connection with the responses out of water. The ani- 

 mals respond as if they are attempting to recede as far as pos- 

 sible from the source of stimulation. When the end of the 

 dish, where the toads are congregated, is placed next to the 

 light, they very promptly drop off the perpendicular glass wall 

 into the water. Sometimes there is an attempt at orientation 

 even before leaving the wall of the trough for the water. The 

 results of the experiments in connection with both the jumping 

 and swimming responses of young toads differ, decidedly, from 

 the results of Parker's (1903, p. 29) suggestive work on Rana 

 pipiens Schreber. He found that these animals were positively 

 phototropic in light, from a Nernst lamp, even at 20,480 ca.m. 

 Without regard to the side of the frog that was exposed to the 

 light, they turned and jumped toward its source. The frogs 

 oriented themselves until they faced the source of illumination 





