488 AUGUSTO BONAZZI 



dioxide by virtue of equation II, the latter source of the gas 

 appears to be the one most active in furthering nitrification. This 

 is probably attributable to the fact that it is directly connected 

 with the life activities of the organism concerned. 



The supply due to reaction I is, therefore, slowly utilized, 

 probably because very rapidly distilled from the immediate 

 surroundings of the cells; or a molecular rearrangement of the 

 basic carbonate used may take place. These considerations 

 would then place the process of nitrification dependent upon and 

 secondary to the process of carbon assimilation. We shall have 

 occasion to return to this point later in this paper. 



According to Warington, nitrification of ammonia can take 

 place only with ammonium carbonate, and the function of the 

 carbonated base is to furnish that compound by reaction with 

 other ammonium salts. Ashby found nitrification to take place 

 in presence of ferric hydrate to a considerable extent, and also 

 some nitrification of the ammonia absorbed by modehng clay 

 alone (1907-1908). 



Hopkins and Whiting (1916) also claim that nitrification will 

 take place in presence of tri-calcium phosphate as a neutraUzing 

 substance. It is evident that in the experiments of the last 

 named investigators ammonium carbonate could not be formed 

 by reaction between the neutralizing base and the source of 

 nitrogen, a fact that throws a doubt on Warington's assumption. 

 The reaction leading to the formation of ammonium carbonate 

 should then be directly connected with the nitrogen nutrition of 

 the organism of nitrosofermentation rather than with the 

 carbon nutrition. The question of the autotrophy and hetero- 

 trophy of the organisms is also intimately connected with these 

 observations. 



If it were possible to avoid, in a culture, reactions I and II, 

 a step would be taken towards the understanding of the phenom- 

 enon that Winogradsky named, " chlorophyllic action without 

 chlorophyll". The aim could be approached either by the use 

 of a non-carbonated base or by allowing nitrification of the 

 ammoniacal nitrogen in the form of hydroxide. Experiments 

 in the hope that the second of these two assumptions might prove 



