Regeneration in Cassiopea 



271 



J The Effect of Rhythtnical Pulsation of the Disk on the Rate of 



Regeneration 



o 



I am indebted to Dr. A. G. Mayer for the method of obtaining 

 a rhythmically pulsating disk. The margin with its sense organs 

 and the mouth apparatus is removed and the ventral surface is 

 cut as shown in Figs. 3 and 4. Such a disk remains quiet if 

 undisturbed, but a rhythmical pulsation can be produced by an 

 electrical stimulation at X. This pulsation in some cases con- 

 tinues for several days after a single stimulation. In an animal 

 operated on in this way there are two regenerating surfaces, an 

 outer one to replace the sensory margin and an inner one to replace 

 the mouth apparatus. In my experiments a comparison was 

 made between those with pulsating and those without pulsating 

 disks, to see whether pulsation has any effect on the rate of regen- 

 eration. 



TABLE III 



Two factors must be considered as entering into the result of 

 the present experiment, first the stimulation of the animal as a 

 result of the electrical shock, and second the pulsation resulting 

 from this. It was very difficult to get pulsation that would con- 

 tinue for a considerable period of time. In all cases it stopped 

 before the completion of the experiment. The data are given in 

 Table III, which shows that the effect of the stimulation and 

 pulsation is inhibitory on the whole. In the table, as in the 



