THE GENUS RHODOCOCCUS 



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This definite and peculiar combination of characters 

 clearly marks the red cocci as a natural group of 

 generic importance. Its habitat and negative Gram re- 

 action, low liquefying power, and slow but abundant 

 growth on artificial media seem to place this group at the 

 extreme saprophytic end of the series of the Coccaceae. 

 Red cocci may of course be occasionally found on the 

 skin, like any other forms common in air or earth, but their 

 occurrence there is apparently exceptional and accidental. 



Our twenty-five cultures included ten packet-formers, 

 and fifteen in which the sarcina-grouping was not observed. 

 In all other respects the packet-formers and the non-packet- 

 formers were alike. Both series showed the same habitats 

 and Gram reactions, the same chromogenesis, the same 

 peculiar relation to gelatin and nitrates. This is a striking 

 example of the fact that differences in cell-grouping are not 

 correlated with differences in general biochemical charac- 

 ters. It seems clear that the red sarcinae are related to 

 the similar forms which show no packets, more closely 

 than to the yellow sarcinae, — which exhibit such distinct 

 group differences in four or five fundamental physiological 

 properties. Logical adherence to the principle followed 

 in dealing with the yellow micrococci and sarcinae, which 

 are similarly related to each other, suggested the formation 

 of two new genera, — one for the packet-formers and one 

 for the non-packet-formers. It was, however, largely from 

 deference to custom, which must be respected in all matters 

 of terminology, that the genera Micrococcus and Sarcina 



