General Bacteriology. 
a. Cells without organs of motion (flag- 
ella), - - =~ = = 9. Spirosoma Miquua. 
b. Cells with organs of motion (flagella) 
1. Cells with 1, very rarely 2-3 
polar flagella, - - - 10. Microspira SCHROETER. 
2. Cells with polar flagella-tufts, 11. Spirillum EHRENB. 
B. Cells flexuous,  - - - - 12. Spirochaeta EHRENB. 
(3) Cells enclosed in a sheath. CHLAMYDOBACTERIACEAE MIGULA. 
A. Cell contents without granules of sulphur. 
a. Cell threads unbranched. 
1). Cells division always only in one 
* plane, - - - - 18. Streptothrix Coun. 
2). Cell division in three planes pre- 
vious to the formation of 
condia. 
i). Cells surrounded by very 
delicate scarcely visible 
sheath (marine), - —§- 14. Phragmidiothrix ENGLER. 
ii). Sheath clearly visible 
(fresh water), - - 15. Crenothrix Coun. 
b. Cell threads branched, - - 16. Oladothric Conn. 
B. Cell contents containing sulphur granules. 17. Thiothrix WINOGRADSKY. 
(4). Cells destitute of a sheath, united into threads 
motile by means of an undulating 
membrane. BEGGIATOACEAE. 
Only one genus. (The single species is 
scarcely separable from Oscillaria) - 18. Beggiatoa TRAVISAN. 
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