RELATIONS OF THE COCCACE^E 37 



sitic habit is, on the whole, correlated with quite distinct 

 morphological and physiological peculiarities. In our first 

 paper on this subject we pointed out that the family of the 

 Coccaceae is divisible on this basis ' ' into two subfamilies. 

 The first, for which we suggest the name Paracoccaceae 

 (paratrophic cocci), includes Diplococcus and Strepto- 

 coccus, parasitic forms 1 which do not develop abundant 

 growth on artificial media and which thrive better 

 under anaerobic than under aerobic conditions, and ap- 

 pear in small cell aggregates of pairs or chains. The 

 second subfamily, the Metacoccaceae (metatrophic cocci), 

 includes Micrococcus, Sarcina, and Ascococcus, sapro- 

 phytic or semi-saprophytic types which are aerobic and 

 form abundant surface growths of large cell groups." 



The study of the literature alone led us to suggest the 

 restoration of the genera, Diplococcus, Weichselbaum, 

 and Ascococcus, Cohn. The reasons for this course will 

 be discussed somewhat fully in succeeding chapters. 

 The former genus was evidently characterized by strictly 

 parasitic habit, very feeble growth on artificial media, 

 and the possession of capsules under proper conditions, 

 as well as by its diplococcoid form. The organisms gen- 

 erally classed in the genus Streptococcus, which obviously 

 form a second natural group of considerable definiteness, 

 are related more closely to the genus Diplococcus than to 

 the rest of the family. Like the diplococci they are 

 normally parasitic on the animal body. Their growth on 

 artificial media, tho more vigorous than that of the 



