234 W- '^- Ceozier, 



Page 



c) The body surface 253 



d) Experiments on mutilated animals 255 



e) Discussion 255 



2. Continued mechanical stimuli 257 



a) Stereotropism and the righting reaction 257 



b) The climbing of vertical walls 259 



3. Vibratory mechanical stimuli 260 



IV. Light 261 



1. Introduction 261 



2. Phototropism 261 



3. The shadow reflex 265 



4. Discussion 273 



a) Phototaxis and the shadow reflex 274 



b) The mechanism of photo-reception 274 



V. Heat 278 



1. Introduction 278 



2. Effects of altering the temperature 278 



3. Local application of heat 280 



4. Discussion 280 



VI. Chemical stimuli 281 



1. Introduction 281 



2. Method ; reactions obtained 282 



3. Quantitative experiments 284 



4. Discussion 288 



VIL Summary 291 



I. Introduction. 



The behavior of those echinoderms which in the adult possess a 

 considerable degree of bilateralsj'mmetry has not received the attention 

 which the morphological peculiarities of these animals would warrant. 

 Of the Holothurioidea, Thyone briareus alone has been studied (Peaese, 

 1908, 1909) with reference to the working possibilities of its 

 nervous system, though there are a number of isolated observations, 

 scattered through the literature, on the habits and reactions of other 

 members of the group. 



The present contribution deals with the sensory physiology of 

 an Actinopodous holothurian found in the shore waters of the Bermuda 

 Islands.^) I wish to express my gratitude to Prof. E. L. Maek, 

 who made it possible for me to enjoy the privileges of the Bermuda 



1) This investigation was assisted by a grant from the Humboldt 

 Fund. 



