12 CLASSIFICATION. 



Zopf , Avho insists upon the polymorphism of these low organisms, divides 

 the bacteria into four groups: 



Genera. 

 Streptococcus, 



1. COCCOCE^: Up to the pre- Merismopedia, 

 sent time, only known in the form of j Sarcina, 

 cocci. Micrococcus, 



Ascococcus. 



2. BACTERIACEJE. Have for the ] Bacterium, 

 most part spherical, rod-like, and j Spirillum, 

 filamentous forms ; the first (cocci) ( Vibrio, 

 may be wanting ; the last are not \ Leuconostoc, 

 different at the two extremities; fila- Bacillus, 

 ments straight or spiral. Clostridium. 



3. LEPTOTRICHE.E.-- Spherical, ] Crmnthri'r 

 rod-shaped, and filamentous forms; ^ l 'Y 

 the last show a difference between the 



two extremities ; filaments straight | Levtothrix 

 orspiral ; spore formation not known. J 



4. CLADOTRICHE^. -- Spherical, | 

 rod-shaped, filamentous, and spiral | 



forms ; the filamentous form pre- \ Cladothrix. 



sents pseudo-branches ; spore forma- | 

 tion not known. 



The main objection to this classification is that it assumes a pleomorph- 

 ism for the bacteria of the second group Bact^riaceoe which has only been 

 established for a few species, and which appear? not to be general among the 

 rod shaped and spiral bacteria. 



De Bary divides the bacteria into two principal groups, one including 

 those which form endospores, and the other those which are reproduced by 

 arthrospores. But our knowledge is yet too imperfect to make this classifi- 

 cation of value, and the same may be said of Hueppe's recent attempt at 

 classification, in which the mode of reproduction is a principal feature. 



The classification of Baumgarten (1890) appears to us to have 

 more practical value, and, with slight modifications, we shall adopt 

 it in the present volume. This author divides the bacteria into two 

 principal groups, as follows : 



GROUP I. Species relatively monomorphous. 



GROUP II. Species pleomorphous. 



The first group includes the micrococci, the bacilli, and the 

 spirilla; the second group the spirulina of Hueppe, leptotrichece 

 (Zopf), and cladotrichece. 



The pleomorphous species described by Hauser under the generic 

 name Proteus are included in the second group among the spirulina. 

 In the present volume we have described these pleomorphous species 

 among the bacilli. 



The Cocci, in the classification of Baumgarten, constitute a single 

 genus with the following subgenera : 1, Diplococcus j 2, Strepto- 

 coccus ; 3, Merismopedia (Zopf) "Merista" (Hueppe); 4, Sar- 

 cina (Goodsir) ; 5, Micrococcus (" staphylococci"). 



The BACILLI are included in a single genus embracing all of 



