General Bacteriology. 61 



. Cells without organs of motion (flag- 



ella), - 9. Spirosoma MIGULA. 



b. Cells with organs of motion (flagella) 



1. Cells with 1, very rarely 2-3 



polar flagella,. - - 10. Microspira SCHEOETER. 



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, - 13. Streptothrix COHN. 



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 COHN. 



b. Cell threads branched, - 16. Cladothrix COHN. 



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. 



