2 LEWIS R. GARY 



sence of any influences exerted through the central nervous sys- 

 tem. An affirmative answer to this question is apparently held, 

 by certain at least of these investigators, to settle finally the 

 question of nervous influence without any consideration being 

 given to the comparison of the course of the regenerative process 

 in animals in which the nervous system was removed from the 

 regenerating area and those in which the nervous system had 

 been uninjured in the portion of the animal left to regenerate. 

 In only a relatively few animals can the nerve centers be removed 

 without bringing about the destruction of, or degenerative 

 changes in, other intimately connected portions of the nervous 

 system, so that this type of operation has not been frequently 

 undertaken. 



Zeleny ('07) and Stockard ('08) removed the marginal sense 

 organs from the disk of Cassipoea xamachana to determine the 

 influence of these structures on the rate of regeneration. Both 

 report that there was no evidence of any regulatory influence. 

 In Zeleny's experiments the entire margin of the disk with its 

 sense organs was removed and the rate of regeneration in these 

 individuals compared with others in which the bell margin and 

 sense organs were intact. In Stockard's experiments the re- 

 sults obtained from specimens prepared as above described 

 were supplemented by those obtained with individuals from 

 one-half of which the marginal sense organs were removed while 

 from the other half an equal amount of tissue was cut from be- 

 tween the sense organs. The two halves were insulated by the 

 removal of two diametrically opposite strips of subumbrella 

 ectoderm. In both experiments the rate of regeneration was 

 measured inward from the periphery of a cavity in the center of 

 the disk from which a circular piece of tissue had been removed. 



In both these researches the experiments were carried out with 

 the view of ascertaining the influence of muscular activity and 

 thus indirectly of the nervous system on the rate of regeneration. 

 In each case it was held that there was no constant difference 

 in the rate of regeneration between the active and inactive 

 individuals. 



