ACTINIAN BEHAVIOR 217 



pain that play so prominent a part in the central nervous activi- 

 ties of the higher animals (Holmes, '11). The best instance of 

 the beneficial responses is that seen in feeding, and the noxious 

 responses are well shown in general retraction and in locomotion, 

 for in all actinians, so far as is known, locomotion is always 

 away from the centre of stimulus. It is from a consideration 

 of activities such as these that sound conclusions can be drawn 

 concerning the possible presence of higher nervous operations in 

 these animals. 



From the standpoint of these general reactions the question 

 of organic unity and centrahzation has already been discussed. 

 The view clearly set forth by Jennings ('05) that the feeding 

 actinian acts as a unit and that hunger and satiety are impor- 

 tant elements in explaining the changes that appear in the 

 course of its general responses seems to be quite unsupported 

 by subsequent work. The essentially independent action of the 

 tentacles as well as that of the reversing mechanism in the 

 esophageal cilia and the discovery by Allabach ('05) that the 

 changes in the whole mechanism as feeding proceeds are due to 

 fatigue and not to anything comparable with satiety, a dis- 

 covery with which my own observations are in accord, make 

 clear that the feeding process is an activity which involves many 

 semi-independent parts as such rather than the activity of the 

 animal as a unit. When one contrasts the utter loss of effec- 

 tiveness of the isolated appendages of higher animals with the 

 almost normal activities of the detached tentacles of many 

 actinians, the low degree of unity present in such forms as the 

 sea-anemones becomes at once apparent. In the feeding of 

 actinians each part reacts appropriately to its proper stimulus 

 and the total act is carried out by a sequence of responses that 

 have almost no relation to a central control. As already stated 

 I agree thoroughly with Gee ('13) that the feeding reactions of 

 actinians give no real support to the idea of organic unity in 

 these animals. 



General retraction is a response to conditions of an unfavor- 

 able or deleterious kind. It is an exhibition of the excessive 

 tonicity of actinian muscle as pointed out by v. Uexkiill ('09) 



