90 RELATIONSHIPS OF THE COCCACE^E 



Paracoccaceae in all of these respects. We have therefore 

 redefined the two subfamilies as follows (Winslow 

 and Rogers, 1906) : 



Subfamily Paracoccaceae (Winslow and Rogers). 

 Parasites {thriving only, — or best, — on, or in, the plant 

 and animal body). Thrive well under anaerobic conditions. 

 Many forms fail to grow on artificial media; none produce 

 very abundant surface growths. Planes of fission often par- 

 allel producing pairs, or short or long chains, never packets. 

 Generally stain by Gram. Produce acid in dextrose 

 and lactose broth. Pigment, if any, white or orange. 



Subfamily Metacoccace^e (Winslow and Rogers). 

 Facultative parasites or saprophytes. Thrive best under 

 aerobic conditions. Grow well on artificial media, producing 

 abundant surface growths. Planes of fission often at right 

 angles; cell aggregates in groups, packets, or zooglcea masses. 

 Generally decolorize by Gram. Pigment yellow or red. 



The subfamily Paracoccaceae must include, besides the 

 two new color-types of the white and orange chromogens, 

 the genera Diplococcus and Streptococcus, for which it 

 was constituted in our earlier scheme. We have pointed 

 out that the diplococci are characterized not only by 

 their peculiar morphology but by strictly parasitic habit, 

 very feeble growth on artificial media, and the possession 

 of well-marked capsules under the proper conditions. 

 Recent work, too, has shown that the fermentative reac- 

 tions of the genus are characteristic. Comparative studies 

 of the best known representatives of this group, the 



