Reactions of I so pods to Light 



265 



TABLE V 



AsELLUS COMMUNIS (18 individuals) 

 December 12, 1906 

 Previous exposure: disuse daylight 



Illumination: horizontal, 80 C. M.; lamp at Section-6 end 

 Experiment began as soon as animals were in tank 



Satisfactory positive reactions were obtained from Asellus after 

 it had been kept in darkness for three or four hours or longer. 

 Often when the intensity was only 2.5 CM. the positive response 

 was not very evident. The most marked positive response fol- 

 lowed exposure to intensities between about 11 CM. (19 c.p. 

 incandescent at 1.32 m. from middle of tank) and 80 CM. Asellus 

 exposed to an intensity of 2855 CM. often appeared positive at 

 first, but remained so for only a very short time, then becoming 

 negative. 



Table IV shows the results of an experiment with 16 Asellus 

 when subjected to light of 2.5 CM. intensity after retention in 

 darkness for 40 hours. This Table shows that the animals began 

 to respond to the directive light within three or four minutes and 

 that within sixteen minutes virtuall)^ the maximum reaction bad 

 taken place. Few random movements occurred in this expen- 



