106 RELATIONSHIPS OF THE COCCACE^E 



duction of more active enzymes of a particular type; or 

 it may simply be associated with greater vigor of growth 

 and multiplication. It is possible that these two charac- 

 ters, which differ in the sarcinae and micrococci, may both 

 be expressions of a greater general vigor, which manifests 

 itself in the property of packet formation as well. If 

 such be the case, the generic difference between these 

 types can scarcely be maintained. Without absolutely 

 conclusive evidence of identity, it does not, however, seem 

 wise to overrule genera which have become so firmly 

 established by long usage. We have, therefore, included 

 in our scheme of the Coccaceae two yellow types, * Micro- 

 coccus and Sarcina, distinguished from each other by the 

 presence or absence of packet formation, but alike in all 

 other respects. These genera are defined as follows: 



GENUS VI. MICROCOCCUS (Hallier) Winslow and 

 Rogers. Facultative parasites or saprophytes. Cells in 

 plates or irregular masses (never in long chains or packets). 

 Generally decolorize by Gram. Growth on agar abundant, 

 with formation of yellow pigment. Dextrose broth slightly 

 acid, lactose broth generally neutral. Gelatin frequently 

 liquefied. Nitrates may or may not be reduced. 



GENUS VII. SARCINA (Goodsir) Winslow and Rogers. 

 Facultative parasites or saprophytes. Division occurs 

 under favorable conditions in three planes, producing 

 regular packets. Generally decolorize by Gram. Growth 

 on agar abundant, with formation of yellow pigment. Dex- 

 trose broth slightly acid, lactose broth generally neutral. 



