120 LIFE IN THE SEA [CH. 



food-stuff is the carbonic acid of the atmosphere, and 

 the nitrogenous food-stuff is some salt of nitric acid 

 or ammonia. The respirable material is the carbohy- 

 drate built up from the carbonic acid and water, and 

 this is then combined with the amino-acid formed 

 from it and the nitrogenous food-stuff to form the 

 proteid. These processes are to us chemical miracles 

 which we cannot as yet imitate in the laboratory. 

 In holozoic nutrition the carbonaceous food-stuff is 

 fat and carbohydrate, and these are converted in the 

 tissues into sugars and fats which are the respirable 

 materials ; and the nitrogenous food-stuff is proteid 

 which is converted into the specific proteid of the 

 animal after having been digested. The mode of 

 nutrition of the plant-animals is a combination of 

 these two primary modes ; and that of the parasites 

 and other saprozoic organisms is simply the holozoic 

 mode abbreviated in some way. 



All animals, whether they live in the open, or are 

 parasites, or whatever be their manner of feeding, 

 must nourish themselves by ingesting the dead or 

 living bodies of other animals or plants, or proteid or 

 amino-acid derived from these sources ; and they can 

 only obtain their carbonaceous and nitrogenous food- 

 stuffs in this way, and not from inorganic materials. 

 Animals must eat other animals or plants. Let us 

 think of an ocean containing only animals and we see 

 that the larger must eat the smaller ones in order to 



