328 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



a few observations of the utmost importance both from a 

 scientific and an economic point of view. Writing with 

 reference to the circulation of matter in nature, he draws 

 attention to the important part played by the denitrifying 

 bacteria of the plankton. In nature the inorganic com- 

 pounds containing nitrogen are present in three forms, 

 as ammonia, as nitrates and nitrites. No plant can 

 develop without inorganic nitrogen compounds, and as 

 all animal life is dependent on plant life, it is seen that 

 all life on the earth is ultimately dependent on the 

 presence of these nitrogen compounds. It is therefore of 

 importance to endeavour to trace their circulation. The 

 three above-named nitrogen compounds and their com- 

 binations as well, are soluble in water. By the action of 

 the atmospheric agents the nitrogen compounds of the 

 land are gradually being washed out of the soil, and 

 find their way by means of rivers to the sea. It is calcu- 

 lated that the Rhine alone carries over 130 thousand 

 million grams of nitrogen every year into the sea, and the 

 total amount annually conveyed by all rivers of the world 

 is computed to be not less than 39 billion grams. But 

 for the action of denitrifying bacteria the ocean would 

 long since have become poisoned by the excess of nitrogen 

 compounds. 



These denitrifying bacteria, however, exercise a 

 reducing action on the nitrogen compounds, so that 

 nitrates are first of all reduced to nitrites, then to ammonia 

 and lastly to free nitrogen. In this way the excess of 

 nitrogen compounds in the ocean are destroyed. The 

 identification of the different species of Bacteria that carry 

 on the decomposition processes in the sea, the investiga- 

 tion of their mode of operation and their mode of life and 

 their distribution in the sea is a subject of the greatest 

 importance. 



