198 



CARNEGIE INSTITUTION OF WASHINGTON. 



In order to detcnninc as accurately as possible the relative amounts of 

 muscular work performed by the two half-disks under the conditions of this 

 type of experiment, simultaneous kymograph records were made from the 

 two halves of the same disk which had been operated on in the manner 

 described. If no cuts were made in the subumbrella tissues of the half-disk 

 with sense-organs, its pulsations were registered on the kymograph as of 

 about three times the amplitude of those of the activated half-disk. When, 

 however, the cuts necessary to form a labyrinth of the subumbrella tissue 

 similar to that in which the circuit wave of contraction was maintained in 

 the activated half were made in the disk with sense-organs, the amplitude 

 of the contractions was no longer greater for the half-disk with sense-organs 

 attached. The striking visual difference in the extent of contraction is there- 

 fore due to the ability of the undisturbed sheet of muscle to cause the margin 

 of the disk to fold inward in contraction in a normal half-disk, giving the 

 regular SAvimming movement, while the cuts necessary to form the labyrinth 

 of subumbrella tissue essential for the maintenance of the circuit wave of con- 

 traction breaks the continuity of this sheet of muscles and makes impossible 

 the folding over of the margin of the disk, which gives the appearance of greater 

 vigor to the pulsation of the uncut disk. When the two half-disks have been 

 subjected to the same type of operation, except that the rhopalia have not 

 been removed from one half, the amplitudes of contraction are registered as 

 of equal extent, so that the pulsation-rate is, therefore, a true index of the 

 amount of muscular work done. 



A comparison of the loss of weight between activated and inactive half- 

 disks, given in table 4, shows that the differences in the rate of loss are 

 relatively small, although the activated disks were undergoing great muscular 

 activity. 



Table 4. — Differences in loss of weight 

 between active and activated half -disks. 



Table 5. — Differences in loss of weight betvcen 

 activated and inactive half-disks. 



The two last-mentioned experiments indicate very clearly that muscular 

 activity, even when greater than normal, is a relatively small factor in the 

 metabolism of Cassiopea, thus confirming the conclusions drawn from the 

 study of the rates of regeneration under similar experimental conditions. 



In connection Avith the experiments in which both the rates of regeneration 

 and the loss of weight were observed for two series of 40 half-disks each, another 

 series of measurements was made, the results of which support the conclusions 

 drawn from the two just mentioned. When the half-disks were prepared for the 

 regeneration measurements a circular disk of tissue 22 mm. in diameter 

 was removed from each half-disk. The diameter of the cavity left 

 when this disk was removed, when measured daily, was found to have 

 decreased in diameter more rapidly in the specimens bearing sense-organs, 

 less rapidly in the inactive specimens, and to only a slightly greater extent 

 in the activated specimens than in those which were inactive. 



