4 LEWIS R. CARY 



every case the experiments were started within two hours after 

 the medusae had been removed from their normal surroundings: 



As the normal habitat of Cassiopea is in rather stagnant quiet 

 water, the disks retain their vitality indefinitely when a single 

 pair are kept in a medium sized battery jar of sea water. In- 

 deed Stockard found that the benefit derived from the daily 

 change of water was more than offset by the harmful effects of 

 the agitation attendant upon the changing of the disks from one 

 jar to another. Since my experiments necessitated the daily 

 measuring of the regenerated tissue which could be done only by 

 removing the disks from the jars and placing them upon a back- 

 ground of colored glass, the water was changed daily. 



In specimens in which the halves were insulated it was neces- 

 sary to scrape over the denuded strips at least once every forty- 

 eight hours, as within that space of time new nerve fibers would 

 be regenerated connecting the old nerve fibers of the insulated 

 halves and consequently transmitting the stimulus necessary for 

 pulsation from the sense organs of the half disk on which they 

 were retained to the muscles of the half disk from which they had 

 been removed. 



In a few of the experiments in which regeneration was slowest, 

 particularly some of those where the sense organs were removed 

 from both halves of the disks, new fxmctional sense organs were 

 developed in the course of an experiment so that a second re- 

 moval of tissue from the portion of the bell margin originally 

 occupied by the sense organs was necessitated. 



In order to determine the influence of the sense organs on the 

 rate of regeneration the following experiments were carried out. 

 First those in which the influence of the sense organs was removed 

 from an entire disk (Zeleny's operation, figs. 1 and 2) or from one- 

 half of a disk (Stockard's operation, fig. 3) by the removal of an 

 appropriate number of sense organs and insulation of the two 

 halves (figs. 1 and 2). Second, disks from which all but one of 

 the sense organs were removed, with the disk either left with its 

 subumbrella ectoderm continuous or with the halves insulated 

 (figs. 4 and 5). Third, disks prepared according to Stockard's 

 method were subjected to the action of anesthetics to eliminate 



