RECENT WORK ON MARINE METABOLISM 13 



But this is certainly not the case. Vernon 1 showed in 1895 

 that the respiratory quotients in the lower invertebrata varied 

 remarkably, and in the more recent studies made by Putter 

 the same facts are disclosed. Thus in a series of determinations 

 of the exchange of oxygen and carbon dioxide in the sponge 

 Suberites the following figures were obtained, at a temperature 

 of 13-5° C: 



Oxygen absorbed = 30 mg. per kilo, per hour ; 

 Carbon dioxide excreted = 282 mg. per kilo, per hour ; 



from which the respiratory quotient is &$, an astonishingly 

 high ratio. 2 So also in the case of the holothurian Cucumaria, 

 when the following values were obtained : 3 



Thus there can be no doubt that katabolic processes occur 

 in the metabolism of these animals which must belong to a 

 type other than the purely oxidation one, and we are compelled 

 to regard these processes as analogous to those characteristic 

 of the saprozooic animal or saprophytic plant. It is well known 

 that many bacteria are anaerobic, and obtain their energy from 

 decomposition or fermentation processes which take place in 

 the complete absence of oxygen. Infusoria also live in media 

 which contain much organic matter, such as carbohydrate, 

 decomposition products of proteids, extractives, etc., and com- 

 paratively little oxygen. So also in the case of the nutrition 

 of the internal parasites of animals. Quite apart from the 

 above evidence, it would be reasonable to expect that among 

 the lower invertebrata living in the sea there would be some 

 which would display a similar or analogous mode of nutrition, 

 and this conclusion is that arrived at by Putter. From a 

 consideration of the above figures, and assuming certain types 

 of decomposition of proteids, fats, and carbohydrates, he gives 



1 " Respiratory Exchange of the Lower Marine Invertebrata," Journ. 

 Physiology ; vol. xix. 1895-6. 



2 Vergl. Phys. Stoffw. p. 33. 



3 Ibid. p. 52. 



