On the Nervous System of Cassiopea Xamachana. 



127 



Three comparisons were made in the experiments dealing with 

 regeneration, loss of weight during starvation, total metabolism, and 

 the influence of the sense-organs on the change in rate of pulsation in 

 response to change in temperature. For all these experiments the 

 oral arms and stomachs were removed and the disk alone used, to avoid 

 the contamination of the water by mucus and to facilitate the opera- 

 tions. In each experiment disks of the same size were used, although 

 specimens of the same diameter showed considerable variation in 

 weight due to differences in the thickness of the mesoglcea. For 

 studying the general metabolism large specimens were used because 

 it was easier to perform the necessary operations. In the first type 

 of experiment, normal disks, or half-disks, were compared with others 

 that had been rendered inactive by the removal of all sense-organs 

 (figs. 1, 2, 3). The sense-organs were cut out from the border of the 



FIGS. 1 and 2. Entire medusae. From fig. 2 all the sense-organs have been removed. From 

 fig. 1 an equal amount of tissue has been removed from between the sense-organs. 



FIG. 3. A medusa prepared with active and inactive halves by removing the sense-organs from 

 half of the disk and then insulating this half from that on which the sense-organs remain by 

 removing two diametrically opposite strips of subumbrella tissue, shown as stippled areas. 

 A piece of tissue was removed from between each pair of sense-organs on the active half-disk. 

 The inner circle represents the limits of the cavity in which the amount of regeneration was 

 measured. 



disk by a sharp cork-borer just large enough to completely remove 

 this structure at one stroke. From between the sense-organs of the 

 "active" specimens a piece of tissue of equal size was removed so that 

 the amount of injury was the same for both specimens. 



In all the experiments on regeneration recorded in the tables given 

 in this paper the halves of each disk were insulated by the removal of 

 two diametrically opposite strips of subumbrella ectoderm extending 

 from the periphery of the disk on each side to a cavity in the center of 

 the disk where the amount of regeneration was measured (fig. 3). 

 In later regeneration experiments and all other experiments where this 

 type of operation was used the medusa disk was separated into halves 

 and the regular operation was performed upon each half. For measur- 

 ing the amount of regeneration a disk of tissue 22 mm. in diameter was 

 removed from a similar part of each half-disk. This complete separa- 



