On the Nervous System of Cassiopea Xamachana. 129 



margin was folded inward onto the body of the disk at each contrac- 

 tion. When, however, a similar labyrinth had been formed in the 

 subumbrella tissues of the active specimen and the continuity of the 

 sheet of muscles had been destroyed, the bell-margin was no longer 

 folded over and its pulsations lacked the appearance of greater vigor 

 than that shown by the activated specimens. 



When simultaneous kymograph records were made of the pulsations 

 of the halves of a disk, one active and the other activated, each with 

 an endless labyrinth formed in its subumbrella tissues, the amplitudes 

 of contraction were found to be equal, showing that the apparent 

 character of the contraction was a function of the normal spatial rela- 

 tionship of the muscle tissue and that when similar series of cuts were 

 made in the active tissues of each half-disk of any pair the rate of 

 pulsation was a true measure of the work done. 



Besides a control series carried along as a check for each experiment, 

 a large series of half-disks were prepared, so that each member of any 

 pair (i. e., halves of the same disk) had been subjected to the same 

 operation. Fifty pairs of such half-disks of the three operative types 

 used were recorded for rate of regeneration and loss of weight during 

 starvation, and 10 pairs for total metabolism, with the result that in 

 every instance the similarly prepared halves of each disk gave results 

 which were within the limits of error of the unit of measurements 

 employed in each set of experiments. It is evident from these results 

 that the medusa disks can be safely considered as physiological units 

 which may be subdivided, with the expectation that like areas or 

 masses of tissue of any one disk will respond in an equal degree to 

 experimental changes in environmental conditions. 



