CH. X. MORPHOLOGY OF THE BACTERIA. ARTHROSPOROUS BACTERIA. 471 



Beggiatoa alba (Figs. 197,198) forms filaments which in an intact state are attached 

 in an ere6t position to fixed objects in dirty water, in water discharged from factories, 

 and in hot sulphur springs. 

 The filaments vary in 

 thickness from i to more 

 than 5 /*, and consist of 

 a single row of cells, the 

 protoplasm of which con- 

 tains granules of sulphur 

 in quantities differing in 

 each cell (see page 455) ; 

 when the sulphur is very 

 abundant it may be diffi- 

 cult to perceive the boun- 

 daries between the cells. 

 The filaments have no 

 separate common sheath 

 and readily divide trans- 

 versely into pieces. Their 

 cells pass successively 

 from the lengthened rod- 

 form into the isodiametric 

 form, and these in the 

 case of the thicker fila- 

 ments into flat discswhich 

 finally divide by longitu- 

 dinalwalls into fourquad- 

 rants (Fig. 127, 6-8). 

 The disc-like cells as 

 well as the isodiametric 

 members of the slender 

 filaments separate after 

 a time from one another 

 (Fig. 197, 9) and round 

 themselves off, and then 

 become active swarm- 

 cells (Fig. 197, 10); at 

 length they come to rest 

 and attach themselves to 

 fixed objects. They mul- 

 tiply abundantly by bi- 

 partition and form irregu- 

 larly-shaped zoogloea-heaps. They may also develope into rods and these again 

 into the filaments above described after the rods have in many cases themselves 

 passed through the swarming-state. In this species also spirally twisted filaments 

 are found as well as the straight ones which we have been hitherto considering, 



FIG- 197. Beggiatoa alba, i group of attached filaments. 25 portions of filaments 

 of different stoutness, 5 in the act of breaking up into fragments. The small dark circles in 

 the interior are granules of sulphur; in the parts of the filaments where the granules are 

 abundant the transverse segmentation is indistinct, in others it is more clearly seen. 6 8 

 fragments rich in sulphur showing the transverse septation clearly after treatment with 

 methyl-violet solution ; in 8 the longitudinal division also is shown in the separate members 

 (formation of cocci or spores). 9 filaments which have broken up into spores. 10 spores 

 in states of movement. The dark circles are in all cases granules of sulphur. After Zopf. 

 i magn. 540, the rest of the figures 900 times. 



