40 GENERAL SYSTEMATIC BACTERIOLOGY 



recognized, and specific descriptions given of over 650 species. Many 

 of the species and even some of the genera cannot at present be identi- 

 fied with certainty, but this classification has nevertheless been entirely 

 too much ignored by bacteriologists. 



De Toni and Trevisan's Classification of Bacteria (1889) 

 Key to Subfamilies of Schizomycetaceae Naeg. 



1. Three stages of development, filaments, rods, and cocci. Filaments (in the 



primary stage) sheathed or sheathless, usually with base and apex differenti- 

 ated, attached or radiating from a central point, rarely free. Rods and cocci 

 included in the filaments I. Trichogenae Trev. 



2. Three stages of development, individual rods, filaments and cocci. Rods 



(in the primary stage) forming filaments and cocci; filaments (2" stage) 

 never sheathed, nor with distinct base, nor fixed, nor radiating from a central 

 point, formed by single bacilli remaining attached, due to imperfect division. 



II. Baculogenae Trev. 



3. One stage only, cells spherical III. Coccogenae Trev. 



Key to Tribes and Genera of the Trichogenae Trev. 



a. Spores (arthrospores) produced in special parts of the filaments (pseudo- 

 sporangia) Tribe I. Crenotriceae Trev. 



Filaments sheathed unbranched Crenothrix Cohn 



aa. Spores (arthrospores) produced in normal filaments: 



b. Filaments pseudoramose. . .Tribe II. Cladotriceae Trev. 

 c. Filaments sheathed: 



d. Filaments subequal from base to apex. Arthrospores 

 numerous, dividing in three directions of space. 



Sphaerotilus Kuetz 

 dd. Filaments from base to apex more and more thickened. 

 Arthrospores formed, dividing only transversely. 



Cladothrix Cohn 

 cc. Filaments not sheathed. Arthrospores coccus-shaped, division 



transverse only Nocardia Trev. 



bb. Filaments unbranched. . . .Tribe III. Kurthieae Trev. 



c. Arthrospores rod shaped Detoniella Trev. 



cc. Arthrospores cocci: 



d. Filaments fixed at base in zoogloeal masses. 



Rasmussenia Trev. 



dd. Filaments free Kurthia Trev. 



aaa. Spores absent, at least never detected. Filaments unbranched. 



Tribe IV. Leptotricheae Trev. 

 b. Filaments sheathed. Base and tip unequal. Rod-shaped gonidia. 



Leptotrichia Trev. 

 bb. Filaments, not sheathed, equal, no rod gonidia. 



