242 RELATIONSHIPS OF THE COCCACE^ 



were recognized as distinct. In making a fresh start with 

 the red chromogens we have felt disinclined to form genera, 

 or even species, on the single character of cell grouping. 

 We have preferred to include all cocci possessing the 

 biological powers characteristic of the red chromogens in 

 a single genus under the name Rhodo coccus. If further 

 study indicates that the property of packet formation is 

 more important than now appears, it will be easy to form a 

 new genus of red sarcinae. It is always simpler to add 

 new genera than to eliminate old ones. 



We have therefore denned the genus Rhodococcus as 

 follows : 



GENUS RHODOCOCCUS (Winslow and Rogers). Sapro- 

 phytes. Cells in groups or regular packets. Generally 

 decolorize by Gram. Growth on agar abundant, with 

 formation of red pigment. Dextrose broth slightly acid, 

 lactose broth neutral. Gelatin rarely liquefied. Nitrates 

 generally reduced to nitrites, but not to ammonia. 



For defining species in the genus Rhodococcus the same 

 characters are available which have proved significant 

 in other genera, action upon nitrates and gelatin. The 

 property of packet formation, if not of generic impor- 

 tance, should perhaps deserve specific value. We are 

 not convinced, however, from our own observations that 

 there are really distinct type centers, showing greater and 

 less tendency to the packet grouping. It may well be 

 that all of the red cocci (perhaps all of the Metacoccaceae) 

 form packets under certain conditions. Only a com- 



