90 MICRO-ORGANISMS AND FERMENTATION. 



(2) Genus Bacillus. Cells covered entirely with cilia ; often forming endo- 

 spores. 



(3) Genus Pseudomonas. Cells with polar cilia only ; seldom form endospores. 



3. Family Spirillacece. 



Cells twisted spirally, or forming part of a spiral-like curve. Division only 

 in one plane after cells have expanded in length. 



(1) Genus Spirosoma, n.d. Cells without cilia ; rigid. 



(2) Genus Hicrospira. Cells rigid, with one, and, less frequently, with two 

 or three polar and undulating cilia. 



(3) Genus Spirillum. Cells rigid, with a bushy formation of polar cilia, shaped 

 in semi-circular curves. 



(4) Genus Spirochcste. Cells in serpentine curves ; cilia unknown. 



4. Family CJilamydobacteriacece. 



Cells cylindrically arranged in threads surrounded by a sheath. Propagation 

 through motile or motionless gonidia, which project from the vegetative cells, 

 and grow into new threads without undergoing any resting stage. 



(1) Genus dilamydothrix, n.d. Cells cylindrical, motionless, without branches. 

 Grouped as threads surrounded by thick or thin sheaths, with nothing to dis- 

 tinguish one end from the other. 



(2) Genus Crenothrix, Cohn. Thread-forming bacteria without branches, 

 differing at the ends ; stationary. Thick sheaths often impregnated with ochre. 

 Cells at first divide in one plane, and later in two or three planes. The products 

 of division are rounded off, and grow into gonidia. 



(3) Genus Phragmidiothrix, Engler. Cells at first assembled in unbranched 

 threads, which divide in three planes, and so produce a strand of cells. At a later 

 stage the single cells penetrate through the fine close sheath, and give rise to 

 branching. 



(4) Genus Sphcerotilus (incl. Cladoihrix). Cells cylindrically enclosed in 

 sheaths, forming asymmetric branched threads without distinction between 

 the ends. Propagation through gonidia, which swarm through sheath, and settle 

 on surrounding objects, developing immediately into fresh threads. The gonidia 

 possess bushy polar cilia. 



II. Order THIOBACTEBIA. 

 1. Family Beggiatoacece. 



Bacteria forming threads, containing no bacterio-purpurin. 



(1) Genus Thiothrix, Winogradsky. Motionless threads clustered together, 

 and surrounded by a fine sheath. Division takes place in one plane. At the end 

 of the thread rod-like gonidia form, having a crawling movement. 



(2) Genus Beggiatoa, Trevisan. Threads without sheath formed of flat cells, 

 crawling like the Oscillaria, and rotating round their axis in a free condition. 

 Gonidia unknown. 



