264 



A. M. Banta 



obtained. This lack of response to light of i CM. or less (being 

 found in animals after their retention in darkness when their 

 response is normally positive, as well as after their exposure to 

 light when their response is normally negative) may be taken as 

 evidence that Asellus is not at all sensitive to light of such in- 

 tensities. The range of intensities to which Asellus failed to 

 respond was, as far as the evidence went, the same for animals 

 previously in darkness and those previously in light. 



After retention in darkness for several hours, Asellus gives a 

 positive response to light of intensities between 2.5 CM. and 80 

 CM. (19 c.p. incandescent at 0.49 m. from middle of tank). 



TABLE IV 



Asellus communis (i6 individuals) 

 January 13, 1906 

 Previous exposure: darkness {in lank) for 40 hours 

 Illumination: horizontal, 2.^ C. A/.; lamp at Section-I end 



+ 1.25 



