496 
BULLETIN OF THE BUREAU OF FISHERIES 
Another cause of fluctuation in the rate of oxygen consumption may be found 
in the variation in the ciliary activity of the gill epithelium and consequently in the 
variation in the rate of flow of water through the gills. In a previous work one of 
us (Galtsoff, 1928) has shown that there exists a wide range of variation in the rate 
of flow of water through the gills of oysters of approximately equal size. Unfor- 
tunately, no method was suggested whereby the rate of flow of water in the oyster 
kept in the metabolism chamber could be determined. 
EFFECT OF OXYGEN TENSION ON OXYGEN CONSUMPTION 
The results of studies made by several investigators of the effect of oxygen 
tension on the oxygen consumption of various invertebrates are contradictory. 
Apparently much more experimental material must be accumulated before better 
understanding of the relationship existing between these two factors is obtained. 
It has been recognized by Thunberg 
(1905) that ox 3 T gen consumption of 
air breathing forms like Limax, Lum- 
bricus, and Tenebrio is dependent 
upon the oxygen tension of the sur- 
rounding medium. Henze (1910) 
extended this work on a number of 
marine invertebrates and has demon- 
strated that while in some of the 
lower forms (Actinia, Anemonia, 
Sipunculus) the oxygen consumption 
decreases with the decrease in its 
tension, in the higher forms with 
well developed circulatory system 
(Carcinus, Scvllarus, Aplysia, Ele- 
done) the consumption of oxygen is 
independent of its tension over a con- 
siderable range. Lund (1921) experi- 
menting with Planaria agilis found 
that the rate of oxygen consumption 
,23 ' 4 ' 5 „ 6 7 8910 of that worm was constant up to about 
36 hours, at which time the oxygen 
Figure 4. — The effect of oxygen tension on oxygen consumption . . . , 
tension became equal to about one- 
fourth or one-sixth of the oxygen tension of air-saturated water at 20° C. Amberson, 
Mayerton, and Scott (1924) reported that oxygen consumption of Limulus, Callinectes, 
and Palaemonites is directly proportional to the oxygen tension in the sea water. The 
opposite conclusion was reached by Helff (1928) who found that crayfish exhibits respir- 
atory independence from oxygen tension over a considerable range. He found also that 
the critical tension is different for the organisms of different sizes. In small animals 
averaging 4.3 grams, the critical tension occurs at 20 per cent of saturation; in those 
averaging 9.0 grams, the limit is 30 per cent; and for large animals averaging 17.1 
grams, the limit is 40 per cent. Below these respective limits the oxygen consump- 
tion becomes erratic. 
It is interesting that the respiratory exchange of unicellular forms (Paramaecium) 
and of the fertilized eggs (Arabacia) is virtually constant over a wide range of oxygen 
tenssion (Amberson, 1928). 
