CLASSIFICATION. 27 



2. BacteriacecB. 



Cells without organs of motion 1. Bacterium. 



Cells with organs of motion (flagella) : 



a. Flagella distributed over the whole body . . 2. Bacillus. 



b. Flagella polar 3. Pseudomonas. 



3. Spirillacece. 



Cells rigid, not snake-like or flexuous : 



a. Cells without organs of motion 1. Spirosoma. 



b. Cells with organs of motion (flagella) : 



1. Cells with one, very rarely two or three 



polar flagella 2. Microspira. 



2. Cells with polar flagella-tufts ..... 3. /Spirillum. 

 Cells flexuous 4. Spirochceta. 



4. ChlamydobacteriacecB. 



Cell contents without granules of sulphur: 



a. Cell-threads unbranched: 



I. Cell-division always in only one plane . 1. Streptothrix. 

 II. Cell-division in three planes previous to 

 the formation of conidia : 



1. Cells surrounded by a very delicate, 



scarcely visible sheath (marine) . . 2. Phragmidiothrix. 



2. Sheath clearly visible (in fresh water) 3. Crenothrix. 



b. Cell-threads branched 4. Cladothrix. 



Cell contents containing sulphur granules .... 5. Thiothrix. 



5. Beggiatoacem. 



Only one species known (Beggiatoa Trev.}, which 

 is scarcely separable from Oscillana. 



