RATE OF REGENERATION IN CASSIOPEA 19 



rinth cut in the muscle tissues of one of its halves. Once estab- 

 lished 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 in- 

 terrupted in this way the circuit wave could be established again 

 by renewed electrical stimulation. The ampUtude of the con- 

 traction wave becomes gradually reduced as time goes on, but 

 there is little variation in its rate. When the rates of regenera- 

 tion of the halves of any disk prepared in this manner are com- 

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

 tained regenerates slightly faster than the inactive one. This 

 difference 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. 4 and 9) although the activated 

 disk pulsates on the average more than three times as fast as one 

 under the control of the sense organs. The amount of activity 

 and metabolism in the muscles if they have any noticeable influ- 

 ence on the rate of regeneration ought to produce a clearly demon- 

 strable result, but as shown by the data in table 3 and figure 9 

 the difference is relatively small. From the point of view of the 

 chemical nature of metabolism (including regeneration) the dif- 

 ference in temperature might conceivably be sufficient to account 

 for the observed difference in rate of regeneration. The half 

 disks in which the circuit wave is maintained show a greater 

 regularity in the rate of regeneration than do the active disks in 

 experiments of type 2 (see table 1). 



The records for 40 disks used in an experiment of this type are 

 shown in table 3 and figure 9. A further demonstration of the 

 influence of the sense organs on the rate of regeneration is fur- 

 nished in another series of experiments, — type 6, figure 10 — in 

 which the two insulated halves of a disk are compared, one of 

 which is contracting normally under the influence of its sense 

 organs while all the sense organs are removed from the other half 

 and a circuit wave of contraction maintained in a labyrinth of 

 its subumbrella muscles. In a disk prepared in this manner the 

 rate of pulsation will be on the average more than three times as 

 great in the activated half disk as in that contracting under the 



