Sensory reactions of Holothuria surinameusis. 



269 



-certain sense, as a measure of the amplitude of tlie shadow 

 reflex. Table VIII gives the successive "retraction times" obtained 

 from three holothurians in bright sunlight. The stimuli were applied 

 •every half minute. 



f 



Fig. B. 



Heactions to repeated shading — 0,5 min. intervals (Individuals (1) and (2) of 



Table VI). 



Retraction 

 time, sees 



Fig. C. 



Amplitude of the reaction to successive shadows, 0,5 min. intervals; "retraction- 

 time", seconds (individuals 1 and 3 of Table VIII). 



The observations of Table VIII are shown graphically in Fig. C. 

 €omparing this with Fig. B, for the reaction times to successive 

 shading, it will be seen that the curves of both the reaction time 



