248 



Papers from the Department of Marine Biology. 



temperature from 30° to 20° increases the viscosity of water about 

 25 per cent, and of a 40 per cent sucrose solution 42 per cent, and of a 

 3 per cent gelatine solution 1,000 per cent (von Schroeder). The 

 increase in viscosity of gelatine, however, does not cause a proportionate 

 decrease in difTusion. We may assume that this fall of temperature 

 may possibly cause about 30 per cent decrease in diffusion of O2 within 

 the cell, due to viscosity alone. Tension is proportional to the absolute 

 temperature. Although diffusion accounts for only about a third of 

 the change in rate of oxidation with temperature, it is undoubtedly 

 a factor. Since diffusion affects oxidation and concentration-gradient 

 affects diffusion, it seems very probable that concentration of O2 should 

 affect oxidation, even though every cell received some oxygen. 



Krogh interprets the experiments on warm-blooded animals as show- 

 ing increased oxidation with increased oxygen tension, and reviews the 

 work of Thunberg, showing the same effect to a greater degree on cold- 

 blooded animals. Henze (1910a) found that the oxidation-rate of sea- 

 anemones and anneUds varies with O2 concentration (and of nudibranchs 

 at low concentrations) and supposed that only a varying fraction of 

 the cells received oxygen; his tables show that the oxidation-rate 

 of Crustacea and jelly-fish fell rapidly with time, but that in one 

 series of determinations on Pelagia, the oxidation-rate varied reversibly 

 with O2 concentration. In order to reduce the diffusion effect, he kept 

 sea-urchin eggs agitated in sea-water and found that the oxidation-rate 

 apparently increased about 8 per cent on doubling the O2 concentra- 

 tion. Henze attributes this apparent difference in respiration to 

 faulty technique, but since the experiments have not been repeated 

 with improved technique, we may assume that a real difference exists. 



It is interesting to compare the metabolism of Cassiopea with that 

 of jelly-fish studied by Vernon. Since only the living cells metabolize, 

 it would be an advantage to know the proportion of cellular tissue to 

 the body-weight, but there is no data on this subject. The skeletal 

 structure, mesogloea, contains less organic matter than the cells, and 

 hence the percentage of organic matter in the body is a partial indica- 

 tion of the cellular mass. The proportion of mesoglea increases with 

 the size of the individual within the same species, but there can be no 



Table 23. 



