42 BIOLOGY AND TECHNIQUE 



Genus III. Pseudomonas. Cells with polar flagella. Endospores occur 

 in a few species, but are rare. 



FAMILY III. SPIRILLACE^B. Cells spirally curved or representing a part of 



a spiral curve. Division in one direction of space only, after preceding 



elongation of cell. 



Genus I. Spirosoma. Cells without organs of locomotion. Rigid. 

 Genus II. Microspira. Cells rigid, with one or, more rarely, two or 



three polar undulated flagella. 

 Genus III. Spirillum. Cells rigid, with polar tufts of five to twenty 



flagella usually curved in semicircular or flatly undulating curves. 

 Genus IV. Spirochcete. Cells sinously flexible. Organs of locomotion 



unknown, perhaps a marginal undulating membrane. 



FAMILY IV. CHLAMYDORBACTERIACE^E. Forms of varying stages of evolu- 

 tion, all possessing a rigid sheath (Hiille), which surrounds the cells. 

 Cells united in branched or unbranched threads. 



Genus I. Streptothrix. Cells united in simple, unbranched threads. 

 Division in one direction of space only. Reproduction by non-motile 

 conidia. 



Genus II. Cladothrix. Cells united or pseudodichotomously branching 

 threads. Division in one direction of space only. Vegetative multipli- 

 cation by separation of entire branches. Reproduction by swarming 

 forms with polar flagella. 



Genus III. Crenothrix. Cells united in unbranched threads, at first with 

 division in one direction of space only. Later the cells divide in all 

 three directions of space. The daughter cells become rounded and 

 develop into reproductive cells. 



Genus IV. Phragmidiothrix. Cells at first united in unbranched threads, 

 dividing in three directions of space, thus forming a rope of cells. 

 Later some of the cells may penetrate through sheath, and thus give 

 rise to branches. 



Genus V. Thiothrix. Unbranched, non-motile threads, inclosed in fine 

 sheaths. Division of cells in one direction only. Cells contain sulphur 

 granules. 



FAMILY V. BEGGIATOACE^E. Cells united in sheathless threads. Division 

 in one direction of space only. Motility by undulating membrane as in 

 Oscillaria. 

 Genus Beggiatoa. Cells with sulphur granules. 



It will be seen in reviewing the classification just given that the 

 subdivisions are based upon questions of form, motility, and situa- 

 tion of flagella. While these characteristics, so far as we know, are 



