140 



Papers from the Department of Marine Biology. 



circuit wave of contraction in the muscles of a half-disk without sense- 

 organs by making a series of cuts by which an endless labyrinth of 

 subumbrella tissue is formed (figs. 4 and 5), the part played by muscular 

 activity and that by the stimuli from the sense-organs can be directly 

 compared. In such experiments all the sense-organs were removed 

 from the medusa disks, the halves insulated, and a circuit wave of 

 contraction started by an induction shock in a labyrinth cut in the 

 muscle-tissues of one of its halves. Once established, the contraction 

 wave would be maintained throughout the course of an experiment 

 unless interrupted by an unusually strong stimulus through some 

 accident in handling. When interrupted in this way the circuit wave 

 could be established again by renewed electrical stimulation. The 

 amplitude of the contraction wave becomes gradually reduced as time 

 goes on, but there is little variation in its rate. When the rates of 

 regeneration of the halves of any disk prepared hi this manner are 

 compared, it is found that the half in which the circuit wave is main- 

 tained regenerates slightly faster than the inactive one. This differ- 

 ence in rate is, however, very much less than between the halves of a 

 disk from one-half of which the sense-organs have been removed 

 (compare figs. 6 and 8) , although the activated disk pulsates from 3 to 

 10 tunes as fast as the one under the control of the sense-organs. 



TABLE 3. Record for 1 to 9 days. 



[Forty specimens from which all of the sense-organs had been removed and the subumbrella 

 muscles of one half activated by a circuit wave of contraction (fig. 8). The letter C after 

 the measurement for any day indicates that the central cavity had been filled by the 

 regenerated tissue.] 



