RESPONSES OF YOUNG TOADS 185 



dinal axes of the toads lie parallel with all the rays of light, 

 for the rays emerge from the bulb at various angles and many 

 of them must cross within the area of experimentation. 



These results seem to indicate that young toads respond 

 positively to incandescent light of 16 c.p. They orient them- 

 selves in such a manner that the long axis of the body lies 

 parallel to some of the incoming rays and the head is turned 

 directly toward the source of light. They retain this orienta- 

 tion with considerable precision while traversing the entire 

 length of the experimentation dish. The fact that the animals 

 move as near as possible to the light, and in some cases climb to 

 the top of the glass wall at the end of the vessel, leads one to infer 

 that the intensity of the light is a factor in causing the move- 

 ments, rather than the direction of the rays per se in the field. 

 In connection with the experiments on young toads just de- 

 scribed, it is interesting to compare the work of Parker (I.e.) 

 on Rana pipiens Schreber. He noticed the interesting fact that, 



"With the lower intensities the animals often did not react for from 

 five to ten minutes or even longer, and the jumping response was fre- 

 quently omitted; but their orientation was finally always with their 

 heads toward the source of light, that is, positive. In some instances 

 after a frog had remained ten minutes or more without changing its original 

 position, it was induced to jump by being touched from behind, and, 

 when this was done, the animal almost invariably turned first and then 

 jumped toward the source of light." 



It has been demonstrated that stimuli from a 16 c.p. incan- 

 descent electric light affects young toads in much the same 

 manner as Parker has observed with reference to frogs. The 

 toads orient more slowly to the weaker light than to the stimuli 

 from the projection lantern. Movement toward the incandes- 

 cent light is also more deliberate than toward the light from 

 the projection lantern. 



Dickerson (1906, p. 66) also has noticed that toads respond 

 positively to artificial light of relatively low intensity. Her 

 statement is as follows: 



"If we go to a pond at night, we shall have every opportunity both 

 to see and hear toads, especially if we carry a lantern. Instead of being 

 frightened by the light, they are attracted by it and may gather about 

 it. If the lantern is set on the ground, they sometimes try to climb to 

 its top." 



The results of my experiments with less intense artificial light 

 agree very largely with those of Cole (1907, p. 392) on Acris 

 gryllus Le Conte. This observer states that the source of the 



