12 CLASSIFICATION. 



Zopf. who insists upon the polymorphism of these low organisms, divides 

 tho h;trt-n.- into four groups: 



Genera. 



Streptococcus, 



1. OrcocE,. Up to the pre- | Merismopedia, 

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

 cocci. Micrococcus, 



Ascococcus. 



2. BACTERIACE^E. Have for the 

 part spherical, rod-like, and 

 filamentous forms ; the first (cocci) 



Bacterium, 



Spirillum, 



Vibrio, 



may be wanting ; the last are not j Leuconostoc, 

 different at the two extremities; fila- Bacillus, 



ments straight or spiral. Clostridium. 



:\. LEPTOTRICHE.E. Spherical, ] Crenothrix 

 rod-shaped, and filamentous forms; Beaaiatoa ' 



the last show a difference between the Phragmidiothrix, 



two extremities ; filaments straight | Levtothrix 

 < u-s i >i ral ; spore formation not known. J 



4. CLADOTRICHE^E. 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^riaceae which has only been 

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

 rod shaped and spiral bacteria. 



De I&arv diviaes 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. 



I lie first group includes the micrococci, the bacilli, and the 



' ilia; the second group the spirulina of Hueppe, leptotrichece 

 '/"pf), and cl(ul<>trirln><t'. 



The pleomorphous species described by Hauser under the generic 

 n;iine Proteus are included in the second group among the spirulina. 

 In the present volume we have described these pleomorphous species 

 among tin- harilli. 



The COCCI, fa tin- classification of Haumgarten, constitute a sin gle 

 genus with the following subgenera : 1. I ) i plococcus ; 2, Strepto- 

 M<Tisnn,/H'<li,i (Xopf) Mcrista" (Hueppe); 4, Sar- 

 <<"" ((i tor) : 5, Mn -rut-nt-cus (" staphylococci "). 



The P,\( n.i.i ; ,iv included in a single genus embracing all of 



