94 



A. M. REESE. 



from that of the ordinary white bulb only in intensity. Owing 

 to this impurity in the colors, especially the blue, the observa- 

 tions with the red and blue lights cannot be given much weight ; 

 some of the observations will, however, be briefly given below. 

 It was found that both with CryptobrancJnis and Nectnnts the 

 responses to light were much more marked for the first ten or a 

 dozen stimulations than for succeeding stimulations, so that it was 

 necessary, on account of this loss of sensitiveness, to make only 

 a comparatively short series of experiments at any one time. 

 Ordinarily these animals will lie for many minutes or, possibly, 

 even hours without the slightest motion, so that their reaction to 

 stimuli at these times is too evident to doubt ; but occasionally, 

 especially at night, they become restless, and it becomes necessary 

 to postpone experimentation. In each case where no reaction was 

 obtained within two and one half minutes the reaction was re- 

 corded as " none." Since the animals under observation were at 

 all times covered with several inches of water it seemed unneces- 

 sary to use any form of heat screen, as this depth of water would 

 absorb all heat rays from the artificial lights if not from the solar 

 illumination. 



REACTIONS OF CRYPTOBRANCHUS TO LIGHT. 



The effect of a ray of white light when thrown on different 

 parts of the body was first tried. It was found that all parts of 

 the body are sensitive to white light, but that the tail is by far 

 the most sensitive region. While enough experiments were per- 

 formed to show that the middle regions were more or less sensi- 

 tive to white rays, it was the head and tail that were chiefly 

 studied in their reactions to light stimulation. 



When a ray of white light was thrown upon the tail the re- 

 sponse was, in very many cases, immediate, and consisted in a 

 quick forward movement of the animal until the tail was removed 

 from the illumined area. In almost no cases among many trials 

 was the response delayed for as much as a quarter of a minute, 

 the average time for a response being about three seconds or less. 

 The extreme sensitiveness of the tail of this animal to light stim- 

 ulation is quite remarkable, and the response is, in all cases, ex- 

 actly the same. 



