OXYGEN CONSUMPTION OF OYSTERS 
495 
activity occupied an intermediate position between the two others. As one can see 
from Table 4 the highest oxygen consumption was recorded in oyster 81, the muscular 
contractions of which were the most active. 
An analysis of all the data when kymograph tracings were obtained was made. 
Kymograph records were grouped into three arbitrary classes (table 5) according to 
the number of contractions per hour. Class A comprised oysters which displa 3 ^ed 
vigorous contractions at the minimum rate of 30 per hour. Oysters that made 5 
or less contractions per hour were placed in class C while those intermediate between 
the extremes, with more than 5 and less than 30 contractions per hour formed class B. 
By" examining Table 5 one can see that the average consumption of oxygen was highest 
in class A and lowest in class C. 
CLASS A. 
CLASS B. 
V - — V \ V- 
CLA55 C. 
_ r ^. 
Figure 3. — Photograph of three kymograph tracings of shell movements used in the experi- 
ments. One-minute intervals indicated by dots. Class A, oyster No. 81; class B, oyster No. 
75; class C, oyster No. 74 
Table 5. — Relation between the muscular activity and the oxygen consumption 
Class : O 2 consumption, c. e. per hour per 10 g. dry weight 
A (more than 30 contractions per hour) 10. 52 
B (more than 5, less than 30 contractions per hour) 9. 80 
C (5 or less contractions per hour) 8. 42 
The scale is obviously only an approximation and fails to explain the fluctuations 
observed within each class or during one experiment. It is quite probable that 
besides muscular activity other factors are responsible for the differences in the rate 
of oxygen consumption observed during this work. One of them is related to the 
seasonal changes in the metabolic activity of the oyster. It has been demonstrated 
by Bruce (1926) that in Mytilus edulis the seasonal changes in absolute oxygen 
requirements are intimately associated with concurrent changes in the chemical com- 
position of the tissues. It is probable that as the time of spawning approaches, the 
metabolic activity of the oyster increases and falls off again after the eggs or sperm 
have been expelled. This problem, however, was not studied during the present 
investigation . 
7895—31 2 
