220 G. H. PARKER 



gartia from which the oral halt has been cut away. Such frag- 

 ments not only creep but creep away from the light as normal 

 individuals do. In fact their activities are in no essential par- 

 ticular different from those of whole animals. Creeping, then, 

 is in no sense dependent upon the animal as a unit but is an 

 activity of the pedal disc and adjacent parts. It is, however, 

 an activity of the disc as a whole. I have never been able to 

 observe locomotion in pieces of the pedal disc. When actinians 

 are cut in such a way that the fragments retain only parts of 

 the original pedal disc, they remain attached to the substratum 

 by their pedal surface but they never exhibit locomotion. It is 

 only after regeneration has set in and a new pedal disc has been 

 established that locomotion recommences. Creeping then is a 

 response which calls for a much more unified mechanism than 

 feeding and I agree with Lukas ('05, p. 126) in regarding it as a 

 response which gives evidence of the highest form of nervous 

 activity thus far discovered in actinians. I am, however, not 

 prepared to go as far as he does and see in it evidence of a primi- 

 tive form of desire and the earhest traces of consciousness (Lukas, 

 '05, p. 127), but of its importance as indicative of a certain- 

 amount of unity in actinians there can be not the least doubt. 



Another line of investigation that is suggestive of more than 

 the simplest form of nervous activity in actinians is the modifia- 

 bility of their responses. This subject has been justly empha- 

 sized by Jennings ('05), who has shown its significance by direct 

 experiment. If a drop of water is allowed to fall on the surface 

 of the water in which an expanded Aiptasia rests, the animal 

 will usually retract. After expansion a second drop often fails 

 to call forth any such response and in fact it is necessary to 

 allow as a rule an interval of five minutes before a second response 

 can be ehcited. Thus the earher stimulus influences the neuro- 

 muscular apparatus of the sea-anemone in such a way that a 

 repetition of the stimulus is not followed by a response. To 

 put the matter as Jennings does, the previous history of an 

 organism has its influence upon its subsequent responses. This 

 feature in actinians and in fact in most other animals has long 

 been famihar to workers in this field, but it is to the credit of 



