ZOOLOGY: L. R. CARY 
615 
figure 1) . In experiments of this type the rate of regeneration is through- 
out its course about 1.3 times greater for the half-disk on which the rho- 
paHa remain than for the half of which the muscles are contracting under 
the influence of a circuit wave of contraction. In terms of muscular 
activity the last mentioned half-disk is developing more than three times 
the energy of the former but its rate of regeneration still remains lower 
than that of the half -disk under the control of the rhopalia. It is quite 
apparent, therefore, that there is no direct relationship beween the 
extent of muscular activity and the rate of regeneration, but that some 
other factor directly related to and controlled by the marginal sense- 
organs plays the most important part in determining the rate of regen- 
eration. In the absence of the influence of the sense-organs regenera- 
tion can take place in an apparently normal manner, but always at a 
decidedly lower rate than that shown by a specimen under the control 
of the sense-organs. 
2. Influence of the Sense-Organs of Cassiopea on the Rate of Metabolism 
as Measured by Production of Carbon Dioxide. The striking evidence of 
some sort of influence exerted by the rhopalia on the rate of regeneration 
in Cassiopea, as described above, naturally raises the question as to 
whether or not a similar influence on other activities not included in the 
former experiments can be detected. Since a measure of general metal 
bolic activity may be obtained by determining the relative rates of 
CO2 production of different animals under various sets of experimenta- 
conditions a series of determinations of total metabolic activity of half- 
disks of Cassiopea under conditions similar to those characterizing the 
regeneration experiments were carried out. To accomplish this end 
the disks were separated into halves, the appropriate operations per- 
formed, and each one put into a separate jar containing 1000 cc. of 
sea water. The jars were then tightly closed by a rubber gasket and a 
clamped top, and, after a given interval of time, the relative amount of 
CO2 produced was measured by titrating against normal sea water 
taken as a control at the time the jars were filled. 
When a half-disk with its sense-organs was compared with the other 
half of the same disk from which the sense-organs had been removed 
the amount of CO2 produced was always found to be greater for the nor- 
mal half-disk. This result is parallel to that obtained from the com- 
parison of the rates of regeneration and may be, at least in part, ex- 
plained by the activity of the muscular system in the half-disk with sense- 
organs. When a comparison of the rates of metabolism is made between 
the halves of a disk from which ah its sense-organs have been removed 
while the muscular system of one-half is contracting under the influence 
