32 



PULSATION OF JELLYFISHES. 



the rate of pulsation becomes slower. For example, twenty disks 

 were cut as shown in figure 33, A, and after they had been set into pul- 

 sation they were cut across as shown in figure 33, B. This cut made 

 the circuit twice as long as it was formerly, and obliged the contrac- 

 tion wave to travel double the distance in order to traverse the circuit. 



C B 



Fig. 33. — Showing how cuts may be made so as to increase the length of 

 the pulsating circuit, thereby decreasing its rate of pulsation. 



We might then expect the pulsation to be reduced to one-half its former 

 rate, but as a matter of fact the wave traveled on an average 1.16 

 times as fast in the long as it did in the short circuit, so that the cut 

 reduced the rate to but 58 per cent of its former value. 



Similarly, if we set disks cut as shown in figure 33, c, into pulsation, 

 and then make two cuts as shown in figure 33, d, making the circuit 

 almost three times as long as it was before, the rate becomes about 

 0.4 of its former value, not 0.33 as we would expect. I believe that 

 the faster rate of the contraction wave in the long circuit is due to the 

 longer rest which the tissue enjoys, thus allowing it the more com- 

 pletely to recover and regain its sensibility to the stimulus which 

 calls forth the contraction. Romanes showed that strong contraction 



