No. 569] 



REGENERATION 



289 



much less sensitive than the expelled portion, just after 

 evisceration. This is due to lack of a central nervous 

 system. 



Behavioe During Regeneration 

 After evisceration each specimen was placed in a sepa- 

 rate jar of fresh sea water. The injured end of the body 

 turns in and closes up tightly, and the entire body is 

 somewhat smaller than before evisceration. Respira- 

 tion is slower and not so vigorous. If the water is stag- 

 nant, within a few hours the animal usually climbs up 

 on the side of the aquarium by means of its tube feet. 

 This part of the animal therefore is capable of respond- 

 ing to a lack of oxygen, and the reaction is independent 

 of the central nervous system. 



The observations upon the following individual, re- 

 ferred to in my notes as Thyone A, will serve to illus- 

 trate the general behavior during regeneration: 



afternoon it climbed up on the side of the jar and clang there evidently 

 for the purpose of respiration. 



July 15-16.— Acts as on the afternoon of the fourteenth. Keeps 

 closed and well contracted at the injured end. Entire body somewhat 

 smaller than before evisceration, due in part to organs lost. Respira- 



July 17.— In the afternoon, after water was changed, Thyone took 

 up position on the sand against the side of the jar farthest away from 

 the source of light. 



July IS.— The next morning it was half buried in the sand in same 

 position, with a few pieces of debris pulled over it. Remained so all 

 day. 



July 23.— For some two days it has been slowly burrowing down until 

 only the two protruding ends of the body can be seen. When a piece 

 of debris that was being held over a part of the anterior end was 

 touched, this end retracted below the surface and the posterior end 

 withdrew until it could scarcely be seen. Later the posterior end re- 

 tracted when the shadow of my hand passed over it. the hand being held 

 about one foot away. The uninjured animal is even m.»re sensitive to 



July 28.— For the past two or three days the Thyone has been slowly 

 moving through the sand in a posterior direction without uncovering 



