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



7. Optimum Temperature. 



We have divided the cocci into five groups, according to their 

 optimum growth temperature. Forty-one cuhures gave "much 

 better," and 42 "better," growth at 20°; 335 developed "equally" 

 at both temperatures; 57 grew "better," and 25 "much better," 

 at 37°. 



We have classed together the first two and last two groups. In 

 making the tables it was more convenient to have fewer groups, and 

 quite as accurate, since the main distinctions (and those not very 

 rigid) are shown in "better growth at 20°" or "better at 37°," and 

 "equal" growth at both temperatures. 



We have already noted the correlation between optimum tem- 

 perature and habitat, the parasitic forms growing best at 37°, and 

 the saprophytic forms at 20°, when any difference appears. The 

 sarcinas belong notably to the second class, as do the Gram-positive 

 cultures. These are the only correlations which have so far ap- 

 peared. 



We have been somewhat surprised not to find special correlation 

 between the optimum temperature for growth and that for color 

 production; but no such correlation appears. With gelatin liquefac- 

 tion also no definite relation appears. 



We have observed also the effect of the body and room tempera- 

 ture upon color production, but without important results. Of 

 the cocci studied, 69 showed a very much higher chromogenic power 

 at 20° than at 37°; 169 showed more color, but not so much more, 

 at the lower temperature; in 245 cases no difference appeared, while 

 13 cultures showed more, and 14 cultures much more, pigment at 

 37°. We have calculated correlation tables for all the various char- 

 acters studied, but in no case did any constant relation appear, 

 except, as noted later, in connection with the kind of chromogenesis. 



8. Chromogenesis. 



As noted above, chromogenesis was determined by matching 

 the pigment dried on white paper against a color chart prepared 

 after a thorough study of the colors actually found among the cocci. 

 This chart included nine hues, designated by Roman numerals, 

 corresponding to the pigments noted below the figure. Under 



