OXYGEN REQUIREMENTS OF SHEEEFISH. 
213 
remaining at a high temperature (e. g., 24°-26° C.) for some time, the oxygen require- 
ment at a slightly lower temperature would tend to be greater than if the shellfish had 
been at a lower temperature before the experiment. If an oyster had been out of water 
for some time before the measurement, more oxygen would be used, generally, than if 
the speeimen were left in the aquarium until the time of the experiment. After the 
shellfish had been kept in the aquarium some weeks they tended to use less oxygen 
than when taken recently from their native environment. Exceptionally an individual 
would show a high utilization of oxygen out of proportion to previous measurements 
and lasting for several days. As many of the interfering conditions as possible were, 
of course, eliminated, but still it seemed necessary to make a considerable number of 
experiments and draw conclusions only from averages. More than 350 measurements 
were made under various conditions on three types of lamellibranchs — the oyster {Ostrea 
virginica), the soft-shell or long clam {Mya arenaria), and the quahog or round clam 
(Venus mercenaria). 
RESULTS. 
OXYGEN REQUIREMENTS OF THE OYSTER. 
Three series of experiments, each made on a limited number of individuals, are sub- 
mitted. Although the results can scarcely be taken to show any seasonal variation, 
they are grouped, for convenience, according to the time they were carried out. In 
table I are the results of measurements taken during July, 1911; in table ii, those of 
July and August, 1912; and in table iii are results obtained during the latter part of 
August, 1912. 
In the experiments of table i definite temperatures were not previously chosen and 
carefully adhered to as in the later work. The results, therefore, are here grouped for 
comparison as follows : All measurements taken at temperatures between 20° and 21 .3° C. 
appear in one column, those at 21.5° to 23.5° C. in another, and those between 26° and 
28° C. in a third. Where two or more experiments were made with one oyster at tem- 
peratures within a given range the average of the results is placed in parentheses. In 
the last three columns are the averages of comparable experiments computed as the 
decimilligrams of oxygen used per hour per 100 grams of oyster. By weight of oyster 
is meant in this and other tables not otherwise specified the weight in grams taken after 
it was closed under water, wiped as dry as possible with a towel, and left to dry in the air 
not more than half an hour. Such weighings were shown by duplication to be accurate 
to within two-tenths of a gram. 
In table ii are the results of experiments performed at definite chosen temperatures 
so controlled that the variation was not more than half a degree centigrade in any single 
experiment. The first five columns of results show the decimilligrams of oxygen used 
per hour at five temperatures by nine oysters. The averages of all comparable experi- 
ments are put in parentheses. The last five columns contain the averages, expressed 
in decimilligrams, of the oxygen used per hour per 100 grams of oysters. 
