DYNAMICS OF REGENERATIVE PROCESSES 213 



5. ON THE INFLUENCE OF THE CENTRAL NERVOUS SYSTEM UPON 

 REGENERATION AND ON PHENOMENA OF CORRELATION IN REGEN- 

 ERATION 



It is rather remarkable that the central nervous system plays an 

 important role in phenomena of regeneration. In 1889 I noticed that in 

 Thysanozoon Brochii, a marine Planarian, the isolated head containing 

 the ganglia is capable of rapid regeneration while the body without the 

 ganglia shows less, or a slower regeneration.* The taking up of food 

 is not responsible for this difference, since the head cannot take up food. 

 That the taking up of food is not essential for regeneration follows also 

 from the observations on the regeneration of pieces cut from the walls 

 of Cerianthus. We must not overlook the fact that the reversible chemi- 

 cal processes in the cells of an animal are liable to provide material for 

 regeneration in the same way as the taking up of food. 



A number of observers T. H. Morgan, Child, Lillie, and Lillian 

 Morgan have since found that the cesophageal ganglia exercise a con- 

 siderable influence upon regeneration in marine Planarians. f 



It is therefore obvious that there exists a typical difference be- 

 tween fresh-water and marine Planarians, since in the fresh-water 

 Planarians the presence of the cesophageal ganglia is not required for 

 complete and rapid regeneration. 



This difference in the influence of the cesophageal ganglia in marine 

 and fresh-water Planarians upon regeneration finds a probable expla- 

 nation in a fact to which 

 Bardeen has called attention; 

 namely, that the longitudinal 

 nerves which go through the 

 whole body of the Planarians 

 are very rich in ganglia in the 

 fresh-water Planarians and 

 very poor in ganglia in Thysa- 

 nozoon. 



Herbst J has discovered the 

 most beautiful case of hetero- 

 morphosis thus far known; FIG. 56. -AFTER HERBST. 



namely, that in Crustaceans in 



the place of an eye which has been cut off, an entirely different organ, 

 an antenna, can be formed (Fig. 56). Herbst proved, moreover, that 



* Loeb, Pflitger's Archiv, Vol. 56, p. 247, 1894. 

 t Lillian Morgan, Biological Bulletin, Vol. 8, 1905. 



j Herbst, Archiv fur Entwickdungsmtchanik, Vol. 9, p. 215, 1900; and Vol. 13, p. 436, 

 1901. 



