98 SEA FISHERIES 



less than our cities requires a system of hygiene. How 

 is this system to be provided ? Once more by the 

 bacteria ; they decompose the excess of nitric acid and 

 restore the free azote to the atmosphere. The remainder 

 is utilised for the production of plankton. I have 

 summarised all these successive transformations in the 

 following table : 



Salts in solution ;> Vegetable plankton :> Animal plankton. Free azote. 



V 

 Herbivorous species. 



Carnivorous species Carnivorous species. 



Azotic albuminoid compounds. 



I 



Carnivorous species. 



Ammonia, nitrites, nitrates. 



I 



Vegetable plankton. 



(in excess) 



Nitrifying bacteria. 



I 



Nitric acid (of the rivers) Nitric acid Denitrifying 



bacteria* 



It would be extremely interesting as a matter of 

 oceanic economics if we could estimate the total produc- 

 tion of each portion of the sea. The sea produces as much 

 as it can produce ; neither more nor less. Consequently 

 the distribution of the units of plankton is practically 

 uniform over enormous tracts of ocean, wherever the 

 composition of the water and external circumstances are 

 the same ; and the total mass of large and utilisable 

 animals, which in the last resort have no other food, 



