INTERNAL ECONOMY OF THE SEA 85 



We may speak of it as the distinction between 

 the hard-mouthed and the soft-mouthed, and it is 

 radical. But to follow it up would take us too far 

 from our present theme. 



The middlemen are Bacteria, which get involved 

 in so many different ways in the business of life. 

 Salt is well known to be antithetic to them, but it 

 has not kept them out of the sea, where they have 

 more than one important role to play. Thus some 

 are putrefactive, breaking down the dead bodies 

 of animals and plants, and the excreta of animals, 

 reducing them to carbon - dioxide, ammonia, 

 ammoniates, and the like, which may re-enter the 

 field of life by forming food for Algae. Microbes 

 of this sort are for ever making a clean thing out 

 of an unclean. But there are others which play a 

 subtler part, by changing the ammoniacal nitrogen 

 into nitrites, and others which carry on this work 

 by completing the oxidation into nitrates. And as 

 nitrites are more available for the nutrition of plants 

 than are ammoniacal compounds, and as nitrates 

 are more available than nitrites, we see, as they said 

 of old time, how well this world is governed. It is 

 not to be forgotten, however, that there are many 

 denitrifying bacteria which work the wrong way by 

 reducing nitrates to nitrites, nitrites to ammonia, 

 and ammonia to free nitrogen. Professor Brandt 

 has suggested as a reason for the remarkable fact 

 that the cold Polar waters are richer in Plankton 

 than tropical seas, that the higher temperature 

 favors the action of denitrifying bacteria, which 



