202 CARNEGIE INSTITUTION OF WASHINGTON. 



Studies on the Physiology of the Nervous Sjjstem of Cassiopea, by L. R. Gary. 



The Influence of the Marginal Sense-Organs (Rhopalia) on the Rate of 

 Regeneration in Cassiopea. 



The results of my earlier studies on the relation of the sense-organs to the 

 rate of regeneration in Cassiopea have shown that the one half of a medusa 

 disk which is contracting normallj^ under the influence of its sense-organs 

 regenerates faster than the insulated other half of the same disk from which the 

 sense-organs have been removed, so that it is inactive. Other experiments 

 showed clearly that muscular activity is not the important determining factor 

 of this difference in the rate of regeneration, but a sufficiently large number of 

 observations had not been obtained to adequately determine the relative rates 

 of regeneration under the different sets of experimental conditions. 



The experiments this year were confined to those dealing with the effects 

 of anesthetics; those in which disks were used on one half of which the sense- 

 organs remained, while the other half was without sense-organs, but in the 

 subumbrella tissue of which a continuous labyrinth was made by appropriate 

 cuts and a circuit wave of contraction initiated by induction shocks. In the 

 third type of operations all of the sense-organs were removed from the disk. 

 A circuit wave of contraction was maintained in one half while the other was 

 allowed to remain inactive. The data obtained from these experiments con- 

 firmed and supplemented those obtained from experiments performed in the 

 same manner and reported in the Year Book of last year. 



The Control by the Sense-Organs of the Rate of Metabolism in Cassiopea. 



In the course of my series of regeneration experiments on Cassiopea, carried 

 on during the season of 1914, Dr. S. Tashiro kindly made with the "biometer" 

 a small number of determinations of the rate of metabolism, as expressed by 

 CO2 production, of the medusa disks under the different experimental condi- 

 tions to which they were subjected in the regeneration experiments. As Avas 

 to be expected, that half of any disk which was contracting normally under the 

 influence of its sense-organs had a higher rate of metabolism than the other 

 half of the same disk which had been rendered inactive through the removal 

 of its sense-organs. When a half disk containing a circuit wave of contraction 

 in its subumbrella tissue was compared with the inactive half of the same disk 

 the rate of metabolism was found to be higher in the activated half. When, 

 however, one compares the rates of metabolism of the two insulated halves of 

 a disk, one of which retained its sense-organs (and was consequently contract- 

 ing normally) while the other contained a circuit wave of contraction, it was 

 found that the half upon which the sense-organs remained showed the higher 

 rate of metabolism, although the half in which the circuit wave was entrapped 

 was contracting at a much higher rate. 



Since these few determinations indicated that the sense-organs exercise 

 some control of the rate of metabolism of the medusae that is independent of 

 muscular activity, a more thorough study of this problem was undertaken 

 during the present season, in collaboration with Dr. Tashiro. In all of our 

 experiments the sense-organs were cut out from one half of the medusa disk 

 with a small cork-borer, while from the other half an equal amount of tissue 

 was cut from between the sense-organs. A continuous labyrinth of tissue 

 was formed on the subumbrella side of the half disk without sense-organs and 

 an entrapped contraction wave was set up bj^ means of an induction current. 

 A series of cuts of the same extent were made on the subumbrella of the half 

 disk with its sense-organs, so that no error would be introduced on account of 

 differences in the extent of laceration to which the different half disks had been 



