130 Papers from the Department of Marine Biology, 



EXPERIMENTAL. 

 INFLUENCE OF NERVE-CENTERS ON RATE OF REGENERATION. 



Previous studies on the influence of the nervous system upon re- 

 generation have given very divergent results which can hardly be recon- 

 ciled even when we consider that widely separated groups of animals 

 were used as the material for experimentation. 



While certain students of this problem (Herbst, Goldstein, Walter, 

 Wolff) have taken the position that the nervous system in general, 

 or some portion of it (sensory ganglion, Herbst, Walter), exerts a stim- 

 ulus necessary for the complete regeneration of normal structures, on 

 the contrary other workers have attributed less and less importance to 

 these influences. The intermediate position that the influence of the 

 nervous system is indirect, being exerted mainly through the con- 

 trolling of motor activity, is well expressed by Child (1905a) in the 

 statement concerning anterior regeneration in Leptoplana, that, ''as in 

 posterior regeneration, there is close parallelism between the rapidity, 

 amount, and completeness of anterior and lateral regeneration and the 

 characteristic motor activity of the part concerned." 



Goldfarb (1909) concludes from his experiments on newts, earth- 

 worms, and planarians that ''these experunents * * * should 

 make one cautious about accepting the view of the direct or even 

 indirect influence of a nervous influence on regeneration." 



In all these studies the point at issue has been whether or not 

 complete regeneration of typical structures is possible in the absence 

 of any influences exerted through the central nervous system. An 

 affirmative answer to this question is apparently held, at least by 

 certain 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 annuals 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 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 (1907) and Stockard (1908) removed the marginal sense- 

 organs from the disk of Cassiopea 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 experi- 

 ments 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 results obtained from specimens prepared as above 

 described were supplemented by those obtained with individuals from 



