NUTRITION AND METHODS OF FEEDING 185 



for metabolic needs arising from other activities than these 

 two. The small amount of muscular metabolism in marine 

 creatures as compared, say, with terrestrial vertebrates, is 

 thought to have two causes : firstly, there is little or nothing 

 required for maintenance of temperature ; and, secondly, 

 marine animals are balanced or counterpoised in water so 

 that locomotion entails relatively very little exertion (Moore, 

 Edie and Whitley, 1914). 



Putter's Theories on the Nutrition of Marine Organisms. 

 — We have emphasised the strong contrast between the 

 typical modes of nutrition of plants and animals and have 

 stated that, apart from one or two minor considerations, 

 marine animals feed solely upon the bodies of other animals 

 or plants. A German worker, however, Piitter (1907-8), 

 has developed a theory which is in strong contradiction to 

 this traditional view. The arguments which Putter employs 

 are so cogent and have aroused such interest that, even though 

 his theory may not have been generally accepted, we must 

 give them a certain amount of consideration. Before 

 doing so, we must in fairness point out that an Italian worker, 

 Carazzi (1896), had already, several years before the 

 first publication of Putter's views, come to the conclusion 

 that oysters absorb nutritive material in solution from the 

 water and feed only in a secondary way on plankton organisms. 

 While, therefore, it is customary to speak of " Piitter's 

 theory," the credit for first suggesting the occurrence of a 

 saprozoic mode of nutrition among marine invertebrate 

 animals would seem to belong to Carazzi (1920). 



The theories of Putter have their basis in the difficulty 

 of demonstrating satisfactorily the food of many of the larger 

 invertebrates. Johnstone {op. cit.) refers to the trouble he 

 has experienced in convincing a class of " sceptical fisher- 

 men " of the presence of food in the alimentary canal of the 

 cockle, and remarks on the absence of food in the gut of 

 mature plaice during the period of the maturation of the 

 gonads. Others have encountered a similar difficulty when 

 investigating the food of such animals as Pycnogonids, 

 Gephyreans, and other forms. The reason for this difficulty, 



