1 84 BACTERIOLOGY. 



GROUP III. LEPTOTRICHE^E. 



Genus I. Crenothrix. Threads articulated ; cells sul- 

 phurless ; habitat water. 



Genus II. Beggiatoa. Threads unarticulated ; cells with 

 sulphur granules ; habitat water. 



Genus III. PJiragmidiotJirlr. Threads jointless ; suc- 

 cessive subdivision of cells is continuous ; 

 cells sulphurless ; habitat water. 



Genus IV. Leptothrix. Threads articulated or unar- 

 ticulated ; successive subdivision of cells not 

 continuous ; cells sulphurless. 



Genus I. Crenothrix. 



Crenothrix Kuhniana, Rabenhorst. Cocci, 

 rods, and thread-forms. The cocci are globular, 

 i 6ju- in diam. The threads are colourless, 1*5 

 5 p, thick, and club-shaped at the extremity, reach- 

 ing a diam. of 6 9 JJL. The threads form colonies 

 with a brick- red, olive-green, or dark-brown to 

 brown -black coloration caused by impregnation 

 with oxide of iron. The threads are distinctly ar- 

 ticulated, and ensheathed. The segments are set 

 free when the sheath bursts, and develop into new 

 threads. In other cases the segments remain en- 

 closed, and subdivide into discs, which, by vertical 

 fission, break up into globular forms (cocci). These 

 again develop into new threads, either within the 

 sheath and eventually penetrating it, or, after they 

 are set free. 



