268 



W. J. Crozier, 



shadows cast every 0,5 minute, in the diifuse light of the laboratory. 

 A similar table for the isolated tentacular ends is shown in Table VIL 

 The shadows in each case lasted approximately one second, though 

 their actual duration was of no consequence for the experiment. It 

 will be seen that the rate of exhaustion varied greatly among the 

 different individuals. Two of the animals (Nos. 4 and 7) ceased to 

 react with the tentacles retracted, while all the rest remained 

 expanded. A feature of this reaction which the plot in Fig. B brings 

 out more plainly, is the rhythmic character of the exhaustion curves. 

 The sensitivity to shadows first falls off to some extent, then 

 increases in recurring periods of some regularity, finally disappearing 

 altogether, but returing after a short interval of rest. 



Table VII. 

 Exp. 27.3. Shadow reactions of five (a — e) isolated tentacle-bearing parts. 



June 30. 4,00 P.M. 1,5 cms of anterior end removed from each 

 of 5 animals ranging in size from 5,0 to 8,5 cms in length. 



July 2. 9,00 A.M. Tentacles expanded; the small anterior pieces 

 had successfully closed over the cut, and three of them were moving about 

 with the aid of their tube feet. 



Shaded at intervals of 1 min., in diffuse light, the shadows lasting 

 l_j_ second. Temp. 26, O*'. Reaction times in seconds. 



No. 



a 



b 



c 



d 



e 



1 



1,0 



1,4 



2,1 



1,2 



1,5 



2 



3,4 



17 



1,3 



1,0 



1,8 



3 



21 



3,0 



3,1 



1,1 



2,1 



4 



1,7 



2,4 



1,0 



2.4 



iß 



5 



CO 



1,8 



oo 



3;4 



2,5 



6 



oo 



1,6 



1,8 



1,8 



3,2 



7 



oo 



1,6 



oo 



1,3 



1,0 



8 





oo 



1,4 



i;o 



1,0 



9 







1,6 



oo 



oo 



oo 



10 







1,0 



oo 



oo 



oo 



11 







oo 



oo 



oo 



oo 



12 







oo 



oo 



oo 



oo 



13 







oo 



. 





, 



14 







oo 



. 







Note, oo Indicates "no reaction" (i. e., infinite reaction time). 



When the tentacles retracted as the result of shading, they 

 remained concealed for a length of time which may be taken, in a 



