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PACIFIC SCIENCE, VoL VIII, April, 1954 
Fig. 1. Oxygen utilization in Pseudozius caystrus. Abscissa — cubic centimeters of oxygen per liter of water; 
ordinate — percentage of oxygen consumed from the oxygen available. / 
group of animals are not well understood, a 
simple picture seems preferable and justified. 
According to our results (Table 1), the 
amount of oxygen consumed decreased with 
the decrease of the oxygen present over the 
entire range of the experiments. Oxygen 
seems, therefore, to be the limiting factor. If 
so, the utilization curve must run parallel to 
the abscissa. But this is not the case for the 
entire curve. Figures 1-4 show, for example, 
that as soon as the oxygen content of the 
water reaches a certain low level (Pseudozius 
2.8-3 cc. O 2 /L, Metopograpsus 2. S-3. 2 cc. O 2 /I., 
Calappa 3. 0-3. 2 cc. O 2 /L, and Pseudosquilla 
about 2.9 cc. O 2 /L) the utilization curve rises. 
This points definitely toward a regulation, 
6.0 5.0 4.0 3.0 2.0 1.0 
Fig. 2. Oxygen utilization in Metopograpsus messor. Abscissa— cubic centimeters of oxygen per liter of water; 
ordinate — percentage of oxygen consumed from the oxygen available. 
