2i8 
BULLETIN OF THE BUREAU OF FISHERIES. 
NONUTILIZATION OF OXYGEN BY CLOSED OYSTERS. 
Since oysters can close absolutely water tight, it seemed possible that under such 
conditions they would take in no oxygen. The very small oxygen requirements of 
voluntarily closed individuals could not, however, be interpreted as proof of this because 
when the oyster appears to be closed it may be slightly and invisibly open. This was 
proved by graphic records. To insure closure throughout an observation it was neces- 
sary, therefore, to use some artificial closing device. Several clamps were tried. An 
ordinary surgeon’s artery clamp was found to be most satisfactory. If clamps without 
imperfections, carefully vaselined, were used, they did not appreciably rust during the 
experiment and withdrew from the water only a small and constant quantity of oxygen. 
As control experiments the oxygen absorption of empty shells of oysters about the same 
size as the one observed was measured. The control shells were fastened together by a 
clamp duplicating the one used on the oyster. Water had some access to the interior 
of the empty shells through nicks in their edges. On their immersion in water all air 
was driven from them. In many experiments controls were deferred until the same 
oyster could be emptied and its shells used for control measurements. 
The results of a number of determinations are given in table v. It is seen that in 
every case the experiment and its control are in close agreement, as the difference is 
within the limit of experimental error except in the case of the largest oyster used. 
Even these differences, however, show a larger oxygen absorption by the empty shells 
than by the closed intact oysters. That the slight oxygen disappearance does not repre- 
sent a respiratory intake by diffusion through the shells is indicated not only by the 
controls but by the observation that a two hours’ exposure of the clamped oyster does 
not cause twice the oxygen absolution observed during one hour. Thus in one experi- 
ment a clamped oyster used 1.83 decimilligrams of oxygen in one hour, but 3.01 in two 
hours, while another, which used 1.70 decimilligrams in one hour, required 2.80 for two 
hours. 
The explanation of the constant slight absorption of oxygen by clamped oysters 
and empty shells was not positively determined, but would seem to lie in several 
causes. Bacteria and various marine vegetative growths on the shells were first con- 
sidered as possible oxygen users. Oyster shells that had been soaked 16 hours in 80 
per cent alcohol and then carefully scrubbed and dried, did, indeed, show a diminished 
oxygen absorbing capacity, in one case lowered from 5.25 decimilligrams per hour before 
the alcohol treatment to 4.68 after it, and in another, from 3.08 to 2.34. This indicates 
that foreign growths do not account for all the oxygen absorption, and, indeed, it was 
found that the cleanest and most carefully sterilized shells took oxygen from the water. 
An adsorption effect of porous substances on dissolved oxygen suggested itself as 
another possibility. It was found that porcelain evaporating dishes about the size 
of oysters showed equivalent oxygen absorbing powers. Corks had the same capacity. 
Water containing medium sized corks lost 2.34 decimilligrams of oxygen per hour,'while 
in a control experiment water alone lost only 0.26 decimilligram, which is within the 
limit of experimental error. 
