THE LEUCO-THIOBACTERIA 



109 



Thiothrix nivea 

 „ tenuis 



tenuissima 



Apex. 



2— 2-5/x I-7M 1-4— I-5M 



All threads of uniform thickness and — i — i-i/x 

 All threads of uniform thickness and = 0-3 — 0-5^ 



As all these forms may be found in the same microscope- 

 field, the inference that may be drawn is that threads of Thio- 

 thrix are of uniform thickness 

 when very young, and that they 

 show inequality of thickness 

 when they further develop. It 

 appears as though Winogradsky 

 had assigned different specific 

 names to different stages in the 

 development of one organism. 



Habitat of Thiothrix nivea. — 

 Found in sulphur springs and in 

 waters, both fresh and salt, which 

 contain sulphuretted hydrogen 

 in solution. 



Thiothrix ANNULATA (Molisch). 



Literature. — (Molisch (5).) 



Description. — The threads are 

 attached by a well-developed 

 slime anchor (about 3*5/x in 

 thickness). The young colonies 

 are composed of short, sulphur- 

 filled threads, all in attachment 

 to the same slime anchor (Fig. \ia). After further growth 

 a long thread is formed which is at first unicellular, but 

 later is segmented by transverse septa. In Fig. 11& is shown 

 a still older thread in which the upper part is septate, but free 

 from sulphur. Very old threads may attain a thickness of 

 7/A, and exhibit knotty thickenings separated by ring-like, 

 constricted, sulphur-free areas (Fig. lie). Fragments break 

 off at the constricted parts and a portion of such a fragment 



Fig. II. — Thiothrix marina 

 (Molisch, 1907). 



