194 



C.-E, A. WiNSLow AND Anne F. Rogers 



With regard to the reduction of nitrates, the white and colorless 

 forms show generally negative results. Nitrites are produced by 

 one in lo of the yellows, a slightly higher fraction of the orange 

 forms, and by half the red-pigment-producers. Ammonia produc- 

 tion, on the other hand, appears in one in eight of the yellows, one 

 in I o of the orange forms, and not at all among the reds. 



TABLE 39. 

 Correlation between Chromogenesis and Optimum Temperature for Growth. 



Optimum Temperature 



20° 



20° or 37° 



37° 



WUte 



Yellow 



Orange 



Red 



4 



28 



8 



66 



156 



32 



13 



126 



42 



o 



25 



o 



Excluding the majority of forms which grow equally at either 

 temperature, it appears that, among the white and orange forms, 

 most of those which exhibit any preference grow best at 37°, while 

 among the yellows 20° is more often the optimum. These results 

 accord with the habitats, respectively parasitic and saprophytic, 

 of the two classes. 



TABLE 40. 

 Correlation between Chromogenesis and Optimum Temperature for Color Formation. 



It appears from Table 40 that temperature differences affect 

 the production of orange pigment much more than that of yellow 

 and that the body temperature interferes with red chromogenesis 

 most of all. 



TABLE 41. 

 Correlation between Chromogenesis and Gelatin'Liquefaction. 



The licjuefaction of gelatin presents another close correlation 

 with pigment production. The white and red forms are almost 

 all non-liquefiers, the yellow cocci show a maximum among the 



