OXYGEN CONSUMPTION OF OYSTERS 493 
Table 3. — Control experiment showing that no oxygen is consumed when the oyster remains closed 
Time, hours 
Oxygen, 
c. c. per 
liter 
Remarks 
0 _ ________ 
4. 37 
Oyster closed. 
Do. 
1 
4.30 
2__ 
4.30 
Do. 
3 
4. 34 
Do. 
4 
4.00 
Oyster open. 
All oxygen determinations were done by the well known Winkler method, modi- 
fied for the presence of organic matter. The latter modification was found necessary 
because considerable amounts of feces were present when the experiment had been 
run for more than 1 hour. All figures of oxygen content were corrected to 0° C. and 
760 millimeter Hg. 
All the experiments were carried on from July to September, inclusive, under the 
following conditions: Temperature of the water varied from 24.5° to 24.6° C.; salinity 
of the water from 30.0 to 31.0 per mille; pH at the beginning of the experiment from 
7.9 to 8.3; oxygen tension at the beginning of the experiment varied from 3.495 to 
4.66 cubic centimeters; oysters varied in size from 6.8 to 10.00 centimeters long and 
4.4 to 7.8 centimeters wide; their dry weight varied from 1.019 to 2.080 grams. 
The procedure of the experiments was as follows : The oyster was removed from 
the harbor in the late afternoon of the day preceding that on which it was to be used, 
was scrubbed, weighed, mounted on a brick, and both the oyster and brick were 
covered with a heavy coating of paraffin. The oyster was allowed to stand in the 
air overnight (by this treatment the oysters opened more quickly the next morning 
than when allowed to remain in water all night). In the morning the chamber was 
filled with filtered sea water to the 2-liter mark, the surface of the water covered with 
a heavy layer of paraffin oil, and the chamber allowed to come to constant tempera- 
ture in the thermostat. Then the oyster was put in and adjusted to the kymograph 
and the stirrer connected. As soon as the oyster opened, a sample of water was 
removed for analysis and the time recorded. 
In a few of the open-chamber experiments, where only a few readings were made, 
no fresh sea water was added to the chamber. In most of them, however, an amount 
of water approximately equal to that removed was added from a small reservoir, 
which was kept at constant temperature by the thermostat. Knowing the capacity 
of the chamber, the 0 2 -tension at the beginning, and at the end of the experiment, 
the number of cubic centimeters of oxygen used by the oysters per time interval was 
calculated. 
OXYGEN CONSUMPTION OF NORMAL OYSTERS 
The results of the determinations of the oxygen consumption of the normal 
oysters are shown in Table 4. One can see from the examination of this table that 
under the conditions of the experiment the average oxygen consumption varied from 
6.45 to 15.04 milligrams per hour per 10 grams of dry weight. There were consider- 
able fluctuations in the rate of oxygen consumption during the period of a single 
experiment which are difficult to interpret. In the experiments Nos. 8-13 the deter- 
minations were made on six oysters kept together in a closed chamber. On several 
occasions (experiments 8 and 11) there was a sudden increase in the rate of oxygen 
consumption, which may be attributed to the increase in muscular activity in the 
attempts made by the oysters to get rid of the glass rods which were introduced 
between their valves. 
