THE GENUS AUROCOCCUS 187 



nitrate medium and withdrawing portions for exami- 

 nation at intervals for three weeks. These experiments 

 showed that in some cultures nitrites appeared first, 

 while both nitrites and ammonia were found on suc- 

 ceeding days. With other cultures nitrites alone were 

 found, and with still others the ammonia test alone was 

 positive, day after day. x Apparently some of the cocci 

 produce ammonia in the peptone-nitrate medium without 

 the formation of nitrites. In a very careful study of the 

 action of sewage bacteria upon nitrates, Gage (1905) has 

 shown that the direct reduction of nitrates to ammonia 

 without the intermediate production of nitrites is un- 

 questionably accomplished by certain forms. In other 

 respects the ammonia producers among the auro cocci 

 apparently resemble the nitrite producers; and in the 

 absence of further evidence it seems best to include 

 them with the latter. Including all the aurococci which 

 produce either ammonia or nitrites in nitrate media, 

 thirty-five cultures belonged to this type. Twenty of 

 the thirty-five were from the normal or diseased body 

 and eleven from the air. Acid production was about 

 the same as in the Aur. aureus type. The Gram stain, 

 however, was negative in eight strains on two succes- 

 sive tests and negative eleven times in one test out 

 of two. Of the eight Gram-negative cultures, five were 

 from air and one from earth. The proportion of strains 

 which showed better color production at 20 degrees 

 was smaller in this type than in either of the pre- 



