222 
BUI^IvETIN op the bureau op fisheries. 
UTILIZATION OF OXYGEN BY CLOSED OUAHOGS. 
Clamping these shells as in the experiments described for oysters showed that closed 
quahogs used no oxygen. Their very smooth shells apparently took almost no oxygen 
from the water. With various sizes of quahogs clamped and observed at 24° C., results 
were obtained as follows: 0.37, 0.25, 0.38, 0.23, and 0.25 decimilligram of oxygen per 
hour. The empty shells, considerably broken in the process of opening, used a 
distinctly larger amount of oxygen than did the closed intact animal. The small amounts 
of oxygen taken up under these conditions are no more than would disappear from the 
sea water with a clamp in it. 
It was clearly shown, however, that voluntarily closed quahogs did take up appre- 
ciable quantities of oxygen. In observations where the shells were apparently quite 
closed, various medium and large sized specimens took up, at 24° C., 2.9, 6.1, 4.6, and 
4.3 decimilligrams of oxygen per hour. It would seem, then, that when voluntarily 
closed they do not remain shut absolutely tight, but take in small amounts of water 
through an aperture too narrow to be visible to the naked eye. The results are sum- 
marized in table vii. 
CONCLUSIONS. 
1. Oysters of medium sizes, at temperatures between 19° and 28° C., used from 7 to 
35 decimilligrams of oxygen per hour per 100 grams of entire weight. The amount varies 
with the temperature, so far as experiments show, according to simple relationship, so 
that the curve approximates a straight line. It is proportionally less for larger speci- 
mens. The oxygen utilization is, however, exceedingly variable, depending on a variety 
of conditions, most of which probably affect the openness of the shell. 
2. Oysters when tightly closed take no oxygen from the surrounding water; at 
least, no more than is taken by empty shells. 
3. Oysters show considerable resistance to lack of oxygen. Only exposure for more 
than a week to water containing very small quantities of oxygen proved fatal. This 
indicates that any conditions causing temporary decrease in the available oxygen are not 
a significant factor in oyster culture. 
4. The common clam {Mya arenaria) shows a higher oxygen requirement than the 
oyster. This seems surprising, in view of the fact that clams so often exist in muds 
where oxygen-consuming putrefactions are going on. The oxygen requirements of 
clams and oysters in proportion to their dried weights are about equal. 
5. Both clams and quahogs {Venus mercenaria) use no oxygen from the water when 
tightly closed, but the quahog takes up oxygen while slightly and invisibly open. 
6. The oxygen requirements of the quahog are, under the conditions of these experi- 
ments, conspicuously low. 
