CH. X] THE CONDITIONS OF LIFE IN THE SEA 209 



water from the atmosphere by means of its green leaves. From 

 these food-stuffs, and with the aid of the energy intercepted from 

 the sunlight, the plant can build up proteid, carbohydrate and 

 fat. These simple food-stuffs are therefore those of the plant 

 organism \ 



The plants are the producers, since they alone can manufacture 

 organic out of inorganic materials. Borrowing terms from animal 

 physiology we may speak of the characteristic process in the life- 

 activity of the plant as an anabolic, or synthetic one. It intercepts 

 the energy of the solar light by means of the chlorophyll contained 

 in its green parts ; and by the aid of this energy it can elaborate 

 materials which possess little oxygen ; and which, when oxidised 

 or fermented can set free a great amount of energy in the form 

 of heat or otherwise. The characteristic process in the life-activity 

 of an animal is a katabolic, or analytic one. It ingests and assimi- 

 lates the highly complex substances prepared by the plants, and 

 either oxidises or ferments these within its tissues; obtaining, 

 in so doing, the energy provided by the synthetic processes of the 

 plant. Thus (on the land) there is a fundamental distinction 

 between the metabolic processes of animals and plants ; and since 

 the latter can alone manufacture living, out of inorganic substance, 

 while the former are able to make use only of the products of 

 the vital activity of some other organism, it follows that the 

 totality of animal life on the land depends on the totality of plant 

 life. If the latter — the producers — were gradually to disappear 

 the former — the consumers — would also disappear. 



We will see that this sharp distinction between animals and 

 plants on the land does not hold good in the sea. Nevertheless 

 we may, for the moment, consider that it does, so that we may 

 divide marine organisms into those which make use of organised 

 food-stuffs, and those which can make use of inorganic, or relatively 

 simple, nitrogenous and carbonaceous food substances. This will 

 enable us to distinguish between the organised food-stuffs of the 

 sea, and the ultimate food-stuffs. 



1 Plant physiologists make a distinction between the "food" and the "raw 

 materials of the food " of a plant. Ammonia and nitric acid salts, carbon dioxide, 

 and water are the raw materials. The proteids and carbohydrates elaborated in 

 the tissues of the plant itself are the foods. 



J. F. 14 



