THE LEUCO-THIOBACTERIA 93 



non-motile, and may be either free or enclosed in slime 

 (zoogloea condition). 



The developmental life-history and methods of reproduction 

 are fully known only in B. alba. In this species reproduction 

 is by fission, and probably also by formation of endospores. 

 Raw cultures in nature form a white slimy or felted cover on 

 the surface of various objects undergoing decomposition ; or 

 if the organism is growing in sewage-laden water, on the bed 

 of the stream. 



Beggiatoa alba (Voucher), Trevisan (i), 1842. 

 Synonyms. — Oscillaria alba (Vaucher) ; Hygrocrocis Van- 

 dellii (Meneghini) ; Beggiatoa punctata (Trevisan) 

 Beggiatoa media, and Beggiatoa minima (Winogradsky) 

 Literature. — Vaucher, 1803; Meneghini (1833-36); Tre 

 visan (1842) ; Cohn (10), 1875 ; Warming, 1875 

 Zopf (i), 1882; Winogradsky (2), 1888; Butschli (i) 

 1890; Fischer (i), 1891 ; (3), 1897; Mitrophanow 

 1893; Corsini, 1905; Keil, 1912 ; Ellis (1924, 1927) 

 Bergey, 1924 ; Bavendamm, 1924. 



Description. — In mass cultures Beggiatoa alba typically 

 forms a dark grey, loosely textured, felted shroud, covering 

 the surface of its host : or if the water is sewage-contaminated 

 a covering on the bed of the stagnant or slow-moving water. 

 Beggiatoa is typically made up of long threads of cylindrical 

 form with rounded ends, and unless very long these are of uni- 

 form thickness, 2 — 6/x. The movement is normally slow and 

 without undulation. Lengths of even a centimetre and more 

 have been observed.* Long threads do not move forward but 

 exhibit a slow swinging jerky movement at the ends, resembling 

 that of Oscillatoria. The average length is 50 — lOOju.. The 

 cells contain, under favourable conditions, an abundance of 

 sulphur globules. 



Motile, colourless threads, with oil-like contents, in a water 

 containing organic matter in sohitioii, may with certainty be 

 referred to Beggiatoa alba. 



* A filament of this length is on the same scale as an inch-thick rope 

 about 140 yards long ; a remarkable instance of cohesion in a substance of 

 such soft matter. 



