EFFECTS OF PULP MILL POLLUTION ON OYSTERS 
153 
three days are recorded here, for the purpose of the table is to demonstrate that oysters 
can remain closed for many days and then still live for a considerable time. These 
oysters were in solutions of sulphite liquor in sea water. The control specimens in 
pure sea water remained open an average of more than 20 hours per day, and in no 
case did one of them die as a result of the tests. 
One oyster (experiment No. 3, specimen No. 5) remained constantly closed for 14 
days, after which it opened and lived for at least 6 more days. Others stayed closed 
for shorter periods of time without damage as due apparently to this cause. It has 
already been pointed out that specimens in liquor solutions live longer the greater 
portion of the time they remain closed. If death were due to lack of oxygen, this 
would not be expected. When such a specimen closes after having been in the liquor 
solution for some time, the fluid filling the mantle and gill chambers is the same as 
that in the experimental tank. The liquor would slowly use up all of the available 
oxygen in this inclosed water, and it would be expected, therefore, that the oysters 
which remain closed most would die most quickly, if death is due to lack of oxygen. 
Such, however, is not the case. In spite of the fact that newly pumped sea water 
was constantly flowing into the experimental chamber, carrying with it dissolved 
oxygen, the oysters which remained open and in contact with the new water died 
more quickly than those which closed. (See fig. 33.) 
Oxygen determinations were not made, but instead of this the experiments were 
so arranged that a large supply of fresh sea water was constantly entering the experi- 
mental tanks. The lowest rate of flow of water was 61 cubic centimeters per minute 
(experiment No. 13) and the highest, 368 cubic centimeters per minute (experiment 
No. 8). In nearly all cases water entered the experimental tank at well over 100 
cubic centimeters per minute. The capacity of each tank was about 3,000 cubic 
centimeters, so there was ample exchange. When solutions concentrated enough to 
show a marked color were used, it was observed that within less than one hour after 
stopping inflow of liquor into the mixing chamber, the color disappeared completely 
from the solution in the experimental tank. 
As explained above, if the harmful effect of the liquor were due to lack of dissolved 
oxygen, it would not be expected that there would be such a difference in the dura- 
tion of life of specimens which remained open most of the time and those which stayed 
closed more. Figure 33 indicates the correlation between time required to kill and 
concentration of liquor when this factor of shell behavior is taken into consideration. 
The effect of the liquor appears to be the consequence of mass action. It is progres- 
sive and steady when the oysters are open, and the liquor is constantly in contact 
with the tissues ; but that portion of the toxic agent which is inclosed when the oyster 
closes may soon become exhausted and the tissue is then immersed in a relatively 
nontoxic medium. 
The nature of the toxicity is not known and would be difficult to establish. The 
work of Galtsoff (accompanying report) demonstrates that the liquor has an immediate 
harmful effect on the activity of the gill mechanism. This effect, however, appears 
to be marked only in the relatively high concentrations. As contrasted to the imme- 
diate reaction of the ciliary mechanism, the oyster as a whole slowly succumbs as if 
by progressive poisoning. 
The normal oyster under favorable conditions remains open most of the time, 
the shells closing and opening again periodically. The frequency of these closures is 
highly variable and the periodicity complicated. While it is difficult to express this 
activity mathematically, a simple comparison of the normal and experimental speci- 
