ZOOLOGY: L. R. GARY 
711 
In the activated and inactive series as well as in the series composed 
of activated and inactive half disks the visible activity, i.e., muscular 
contraction was much greater in those members of each series in the 
tissues of which the circuit wave of contraction was maintained. When 
compared with half disks under the control of the sense-organs, the rate 
of pulsation of the activated disks was from 3.5 times as great at the 
beginning of any experiment to 10 times as great at the end of the first 
day. During this interval the rate of the half disks with the sense- 
organs fell to scarcely more than half the original rate while, on the 
contrary, the rate of the activated half disk always increased. 
Simultaneous kineograph records of the pulsations of the two halves 
of the same disk, one with its sense organs and the other activated by a 
circuit wave of contraction, were made to measure the amount of mus- 
cular work done by each half under the given experimental conditions. 
In all these determinations it was found that the amplitude of the con- 
traction as recorded on the drum depended upon the character of the 
operation that had been performed upon the half disk. When the ac- 
tive half remained with its subumbrella muscles undisturbed, the re- 
sulting contraction was more extensive than that of the activated mate. 
When, however, the same operation had been made upon each of the 
two halves of a disk, from one of which the sense organs were removed, 
the amplitudes were equal for each half, so that the rate of pulsation is 
apparently a true measure of the work done. 
The comparison of the loss of weight shown by activated and active, 
as well as by the activated and inactive pairs of half-disks, shows very 
clearly, just as when regeneration is used as the basis for comparison, 
that muscular activity is a relatively unimportant factor in determining 
the metabolic activity of Cassiopea. 
Influence of marginal sense-organs on total metabolism. — To measure 
the total metabolism of half disks of Cassiopea under the several opera- 
tive conditions involved in the regeneration and starvation experi- 
ments, specimens prepared in the manner previously described for 
these experiments were placed in closed jars containing known volumes 
of fresh sea water, and after different intervals of time the amount 
of CO2 given off was determined for each specimen. In making these 
determinations, the records were kept in terms of increased hydrogen 
ion concentration, the values of which were later determined by add- 
ing known volumes of CO2 to a volume of fresh sea water equal in 
amount to that contained by the jars used in the experiments with the 
medusa disks. In many of the experiments the disks were kept in the 
closed jars until one member of a pair had ceased to pulsate, because of 
the narcotizing effects of the CO2, so that it was possible to obtain a 
