RESPONSES OF YOUNG TOADS 181 



experimentation, the trough was immersed in cool water from 

 time to time, thus keeping the vessel cool and moist. 



When the dish is placed in the beam of light, it is noticed 

 that the toads are scattered promiscuously throughout the 

 entire length of the vessel. The first demonstrative movement 

 is a decided orientation. All the animals that are facing the 

 light immediately turn around until their heads are pointing 

 directly away from the source of illumination. The orientation 

 is of such a nature that the' longitudinal axes of their bodies 

 become parallel with the rays of light. Those individuals which 

 are facing away from the source of illumination, in the first 

 instance, are already commencing to jump away from the light. 

 After all the toads have completed the orienting reaction, there 

 is a general movement towards that end of the dish farthest 

 from the source of light. The animals jump rapidly toward 

 the extremity of the vessel. The pauses between the jumps 

 are very brief, in many instances barely extending over a second 

 of time. Orientation with the longitudinal axis of the body 

 parallel with the incoming rays is retained while the organisms 

 travel the entire length of the dish. After reaching the end of 

 the receptacle, the toads usually remain oriented with their 

 heads touching the glass. If they are left in this position for 

 some time, many of the individuals climb up the perpendicular 

 end of the vessel as if to move away as far as possible from the 

 source of illumination. Those that climb to the top are not 

 in the most intense glare of the prejection lantern, their elevated 

 position placing them a little above the strong central beam of 

 light. Possibly this movement may be due, in part, to response 

 to contact stimuli. The dish is now turned around until the 

 end where the animals are congregated is again brought nearest 

 to the light. Those animals clinging to the upright end of the 

 vessel quickly drop to the bottom. All the toads promptly per- 

 form the reaction of orientation and jump rapidly to the far 

 end of the trough as in the former instance. This reversing of 

 the dish is continued for about eight trials and the animals 

 respond promptly each time to the photic stimuli, the response 

 being as previously described. 



Some experiments on the influence of intense light upon the 

 swimming responses of the young toads were also undertaken. 



