152 
BULLETIN OF THE BUREAU OF FISHERIES 
the new shell, does not extend outward as in the normal oyster, but withdraws several 
millimeters back into the shell. In addition, there may be more fundamental physio- 
logical reasons why treated specimens do not grow, but the above observation has 
been repeatedly made during these tests. 
In an early part of this report it was pointed out that most of the works dealing 
with sulphite pollution have been concerned with the effect of diminished oxygen 
supply on fishes. It is certain that sulphite liquor is a strong reducing agent. Some 
fishes are very sensitive to reduced oxygen content of the water, and it may well be 
that this constitutes the major harmful effect on them of the liquor. In the case of 
oysters, however, dissolved oxygen is of secondary importance in this matter, for it 
is well known that the oxygen requirement of oysters is low. Because of this fact, 
oysters can be kept out of water for long periods of time with little harmful effect. 
Verrill (1885) observed that oysters which were out of water lived for about 
eight weeks, during which time they necessarily remained closed, or the inclosed 
water would have been lost. Mitchell (1912) found that medium-sized oysters at 
between 19° and 28° C. used from 7 to 35 decimilligrams of oxygen per 100 grams of 
total weight, the amount used varying with temperature. He determined that com- 
pletely closed oysters take in no more oxygen from the medium than do the shells 
alone. In one case an oyster lived in an almost oxygen free medium for 7 days with- 
out apparent ill effect, although it had absorbed only 1.2 milligrams of oxygen during 
the period. 
Nozawa (1929) showed that the oxygen consumption of the oyster is independent 
of the oxygen tension until reduced to 0.1 per cent or lower. Even after oxygen 
consumption is reduced to none, carbon dioxide is still produced, and he agreed with 
Barkeley (1923) that the crystalline style plays a role in this anaerobic respiration. 
A more complete review of the physiology of respiration in the oyster may be found 
in the recent publication of Galtsoff and Whipple (1930), who found that oxygen 
consumption depends upon oxygen tension only when the amount of oxygen in the 
medium is below 2.5 cubic centimeters per liter. 
Table 4. — Showing lengths of time specimens remained closed continuously 
[Only periods of four days or more are included] 
Experiment number 
Specimen 
number 
Number 
days 
closed 
consecu- 
tively 
Condition following period of closure 
l 
4 
Still living 18 days later. 
2 
1 
6 
Still living. 
3 
5 
14 
Still living 6 days later. 
6 
Still living 15 days later. 
16 
5 
4 
Died 1 day later. 
1 
8 
Died 6 days later. 
18 and 19 
4 
5 
Still living 4 days later. 
20 
6 
8 
Died 5 days later. 
2 
-9 
On the 1st, 2d, and 7th days the specimen was open 0.1 hour each. Died 11 days 
later. 
24 
5 
4 
Died 8 days later. 
6 
6 
Died 10 days later. 
When the valves of the oyster are closed, the normal flow of water is stopped, 
and very little, if any, oxygen is able to enter. In the experiments just described, 
it frequently occurred that specimens would remain closed for many consecutive 
days without once opening the valves to take in new water. Table 4 summarizes 
the most important examples of this reaction. Only periods of closure of more than 
