492 
BULLETIN OF THE BUREAU OF FISHERIES 
a 3-centimeter layer of heavy paraffin oil. It has been demonstrated by the work of 
Gaarder (1918) and Nozawa (1929) that the oil layer of this thickness intercepts com- 
pletely the interchange of gases between the water and the air and that, after the 
equilibrium between the oxygen tension in the water and in the oil has-been established 
the oxygen tension in the water covered with oil remains practically constant. The 
set up of the apparatus is shown in Figure 2. The chamber A 'filled with sea water 
was placed in a constant temperature water bath, B ; the water in the chamber was 
stirred with an electric stirrer; two glass tubes served for taking a sample of water, 0, 
and replenishing the supply of it, I, from bottle R, which contained filtered sea water. 
Figure 2.— Set up of the apparatus for the determination of oxygen consumption. Open chamber method. A, Giass jar 
(chamber) filled with water to the level indicated by the heavy line appearing just below oil layer (shaded ara); B, water 
bath; H, heater; C, metastatic temperature controller; I, glass tubing through which watei is added; O, glass tubing for 
taking a sample; S and S', electric stirrers; P, layer of paraffin oil; K, kymograph; R, bottle with filtered sea water of 
known oxygen content; T, thermometer. Relays to operate the temperature controller, dry cells, and rheostats for electric 
stirrers are not shown 
Temperature of the bath was controlled by means of electric heater ( H ), stirrer (S'), 
and metastatic mercury temperature controller ( C) set at 24.5° C. 
At the end of the experiment the oyster was removed, the shells pried apart, and 
the liquor allowed to drain out for exactly 30 minutes. Then the meat was scraped 
out into a tarred crucible, weighed, and dried to a constant weight, first at 60° C., 
then at 100° C. In some instances this material was used for copper determination. 
On several occasions when the oyster placed in the open chamber failed to open, 
opportunity presented itself to make control experiments. Determinations made at 
1-hour intervals (Table 3) show that under these conditions neither the environment 
nor the oyster consume any oxygen. Thus, all oxygen consumed when the oyster is 
open may be justly attributed to the respiratory exchange of the organism. 
