232 



THE CONDITIONS OF LIFE IN THE SEA [PART III 



come from carbon compounds present in solution in the water 

 circulating through the aquarium ^ 



Is a large part of the carbonaceous food of these animals (and 

 by implication, a part also of the nitrogenous food) obtained from 

 compounds in solution in the sea ? I think that the evidence 

 outlined above, though indirect, is fairlv conclusive in favour of 

 such a statement. If it is, what is the nature of the metabolic 

 process to which this dissolved food-stuff is subjected in its 

 passage through the tissues of the animal body ? This cannot 

 be similar to the oxidation process which is characteristic of the 

 warm-blooded animal. In the case of the latter the absorption of 

 oxygen from the atmosphere is carried out in the lungs, and 

 probably more of the gas could be taken into the blood stream 

 than would be sufficient for the oxidation of the food products in 

 the tissues. But this is probably not the case with the two 

 animals studied by Putter. The following figures shew the results 

 of several estimations of the COo and exchanged"^: 



Respiratory exchange in Suberites and Cucumaria. 



These results shew that the amount of oxygen contained in 

 the carbon dioxide given off is far more than can be accounted for 

 by the oxygen taken in ; that is to say the respiratory quotients 

 are astonishingly high. All the carbon dioxide which is given off 

 cannot proceed from the oxidation of carbon, since not enough 

 oxygen is taken in to balance the gas contained in the COo which 

 is excreted. In the case of the fermentation of sugar by a yeast, 

 both carbon dioxide and alcohol are formed but the former does 



^ Vergleich. Phys. Stoffw. p. 61. 

 2 Ibid. pp. 33 and 52. 



