128 LIFE IN THE SEA [CH. 



compounds are generally similar to those found in 

 the soil and known as humus they consist of fatty 

 acids and soluble carbohydrates ; the nitrogen com- 

 pounds are such as are described by the water 

 analysts as 'albuminoid ammonia/ that is amino-acids 

 and analogous compounds. They would finally be 

 reduced to their simplest terms by the action of 

 bacteria, but before they become so oxidised part of 

 them is made use of as food-stuff by the saprozoic 

 animals and the saprophytic plants. 



Trustworthy analyses made from the water of the 

 North Atlantic show that these substances are present 

 in the following proportions : 



Carbon compounds other than carbonates dis- 

 solved in sea-w r ater 9*2 milligrams per litre (9*2 

 parts per million). 



Nitrogen compounds other than ammonia or 

 nitrate dissolved in sea- water 0*126 milligram per 

 litre (0*126 part per million). 



The amount of these substances at the disposal of 

 saprozoic organisms is therefore very small, but it is 

 greater than the amount of proteid or carbohy- 

 drate contained in similar volumes of sea-water in 

 the form of plankton. Thus some recent trustworthy 

 estimations of the food value of the plankton give 

 the following results (northern seas) : 



Carbon present in the form of organisms 0*083 

 milligram per litre (0*083 part per million). 



