360 



Mr. H. S. Fremlin. 



[Feb. 23, 



Secondly, gelatine plates were poured from oxidised ammonia solu- 

 tions ; these also gave the same species of micro-organism, often in 

 practically pure culture. From one such plate a piece was removed, 

 and in an ammonia solution it produced oxidation. This oxidised 

 ammonia solution again yielded the same species on gelatine plates. 



Gelatine media prepared from divers soils and inoculated with 

 oxidised ammonia solutions exhibited the same species of micro- 

 organism. 



Hence it is to be inferred that, either the nitroso-bacterium grows 

 on gelatine, or that an organism morphologically similar occurs in the 

 same inorganic solutions with the nitroso-bacterium and thrives like it 

 in inorganic solutions. 



To arrive at some definite conclusion on this point further experi- 

 ments were made with agar plates. 



Agar Plates. 



In commencing my researches with Agar, beef-broth agar was used. 

 Beef -broth Agar. 



Plates of this medium, inoculated from cultures containing nitroso- 

 bacteria gave similar results to those with gelatine ; that is to say, 

 micro-organisms, morphologically similar to the nitroso-bacterium, 

 grew well on agar, as they had done on gelatine. 



Pieces of these plates showing colonies were on fifty-three occasions 

 inoculated into ammonia solutions ; of these fifty-three solutions 

 twenty showed formation of nitrite. 



Pieces of such plates, on which no colonies were found, were in 

 nineteen instances inoculated into ammonia solutions. In no case did 

 .the formation of nitrite occur. 



Hence we have : — 



Agar Plates with Colonies. 



Inoculated. Oxidised. 

 53 20 



Agar Plates without Colonies. 



Inoculated. Oxidised. 

 19 



I also made numerous experiments with a medium which I term 

 u ammonia agar." This consists of : — 



Ammonium sulphate, 1 gramme. 

 Potassium phosphate, 1 gramme. 

 Distilled water, 1 litre. 



