144 



Papers from the Department of Marine Biology. 



TABLE 4. Record for 1 to 5 days Continued. 



[Forty specimens, one half of each one pulsating under the control of its sense-organs, while a 

 circuit wave of contraction was maintained in the subumbrella muscles of the other half 

 (fig. 10) . The letter C after the measurement for any day indicates that the central cavity 

 had been filled by the regenerated tissue.] 



As was pointed out previously, the stimulus for pulsation originates, 

 at any given time, from a single sense-organ, and pulsation will be 

 continued at nearly its normal rate by a medusa upon which a single 

 sense-organ remains. To test the efficacy of a single sense-organ to 

 control activities other than muscular contraction a series of disks 

 prepared as above described (except that each "active" half-disk had 

 a single sense-organ) were used in a parallel series of regeneration 

 experiments. In all instances such active disks showed an unusual 

 irregularity in the rate of pulsation, since there was present no other 

 nerve-center to take up the initiation of impulses causing pulsation 

 whenever the rate of discharge of the single organ fell below normal. 



