RESPONSES OF YOUNG TOADS 193 



writers, Torelle, Dickerson and Miller, indicate clearly whether 

 the response is due to light or temperature. 



VII. RESPONSE TO COLORED LIGHT 



A few experiments of a very general nature were performed 

 with colored light as the source of stimulation. The young 

 toads were subjected to the stimuli from a 16 c.p. incandes- 

 cent light. At first the light was passed through glass of various 

 colors. Later the rays were transmitted through colored solu- 

 tions prepared according to the directions recommended by 

 Nagel (1898, pp. 649-655). Such light proved to be more 

 nearly monochromatic, as was seen on examination with the 

 spectroscope. The solutions were placed in a glass cell with 

 parallel sides. Red and blue are the only colors that will be 

 referred to here. 



The young toads are seen to be scattered promiscuously 

 throughout the experimentation dish when it is placed in the 

 beam of light transmitted through the red solution. Frequently 

 there is observed to be considerable hesitancy before the animals 

 orient themselves with reference to the light. Some of them 

 turn toward the light, while others exhibit no definite orienta- 

 tion. In some experiments it is observed that the number of 

 toads responding positively to the light is slightly in excess of 

 those responding negatively; but in other experiments the 

 reverse proves to be the case, for the number of animals exhib- 

 iting the negative response to the light is somewhat greater than 

 those exhibiting the positive response. Usually, however, it 

 may be stated that a small majority of the toads turn in such 

 a manner that their heads point toward the source of illumina- 

 tion. Some animals orient a few seconds after they are placed 

 in the beam of light. Others wait much longer than this before 

 they turn either away from or toward the red light. Certain 

 individuals jump in the direction in which their heads are point- 

 ing, immediately after orientation is completed, while others 

 wait from a few seconds to several minutes before they jump 

 away. The jumping movement toward the red light is far less 

 common than is the case with reference to the blue light. In 

 general it may be said that the movements of young toads away 

 from and toward the source of illumination are slower and with 

 more and longer pauses between the jumps than is the case when 



