2/2 Charles Zeleny 



experiments, the individuals, except the last two are grouped in 

 pairs, one member of each pair being stimulated, and the other one 

 unstimulated. 



In four of the six pairs of cases the unstimulated individuals 

 show a greater amount of regeneration than the stimulated ones. 

 In one the two are equal and in the sixth the stimulated is greater 

 than the unstimulated. 



DISCUSSION 



I The Relation of the Degree of Injury to the Rate of Regeneration 



The results obtained in Cassiopea agree with the general rule 



1 have found to hold true in the arms of Ophioglypha lacertosa and 

 the chelae of Cambarus propinquus and which Ellis finds in the 

 legs of Mancasellus macrourus. The rate of regeneration of a 

 removed appendage is determined not only by the character 

 and position of the cut surface, but also by the character and 

 extent of other injuries received at the same time. The rate 

 increases with added injuries to other parts of the body up to an 

 optimum which represents the amount of injury most favorable for 

 regeneration. Beyond this point added injury causes a decline 

 in the rate of regeneration. In the case of the arms of Cassiopea 

 the optimum comes when six of the eight arms are removed. 



2 The Relation of Successive Injury to the Rate of Regeneration 



Careful investigations of the rate of regeneration after successive 

 injury are rare in the literature. The general statement is, how- 

 ever, frequently made that the rate and character of regeneration 

 are unaffected by successive injury within very wide limits. I have 

 been able to find descriptions of three cases which do not agree 

 with this statement. 



Vanlair finds that the sciatic nerve of the dog regenerates more 

 rapidly after the second than after the first removal. 



Driesch finds in Tubularia that the development of the aboral 

 hydranth is more rapid after a second than after a first removal. 

 He also makes out an interesting case of effect of successive re- 

 moval on the character of regeneration in Antennularia. The free 

 basal end of the stem of this hydroid, after a first removal, develops 



