34 TAXONOMY 



Family 3. SPIRILLACEAE. 

 Vegetative cell cylindrical but spirally twisted. Fission always transverse. 



Genus VIBRIO, Miiller and Loffler. Very slightly curved rods, ' comma ' shaped ; 

 motile, monotrichous. Vibr.'o cholerae asiaticae and numerous other vibrios of fresh and 

 salt water. 



Genus SPIRILLUM, Ehrenberg. Cylindrical cells twisted in an open spiral ; motile, 

 lophotrichous. Spirillum undula, Sp. rubrum. 



Genus SPIROCHAETE, Ehrenberg. Cells long and attenuated, spirally twisted with 

 numerous turns ; cilia unknown ; the cell membrane is perhaps yielding. Spirochaete 

 Obermaieri (remittent fever). 



Order 2. TRICHOBACTERINAE. 



Vegetative phase an unbranched or branched filament or chain of cells, the indi- 

 vidual members of which break off as swarm-spores (gonidid). 



Family i. TRICHOBACTERIACEAE. 

 (a) Filaments non-motile, rigid, enclosed in a sheath. 



Genus CRENOTHRIX, Cohn. Filaments unbranched and devoid of sulphur granules. 

 Genus THIOTHRIX, Winogradsky. The same, but containing sulphur granules. 

 Genus CLADOTHRIX, Cohn. Filaments branched, false dichotomy (includes 

 Sphaerotilus). 



(b) Filaments motile, with oscillating and gliding movements, and devoid of 



a sheath. 

 Genus BEGGIATOA, Trevisan. Containing sulphur. 



For the genus Streptothrix see next chapter. Further particulars as regards the 

 discrimination of genera and species will be found in the works quoted in Appendix 

 (No. 3). 



