274 THE IRON BACTERIA 



first described by KUtzing. A second sheath-forming thread bacterium, allied 

 to the genus Cladothrix, was also examined by him, and named Sphm-otilus natans. 

 It is still too imperfectly known to be dilated upon here, although ED. EIDAM (II.) 



FIG. 66. Crenothrix polyspora. 



Germination of the cocci (g) within the sheath of the parent 

 thread. Magn. about 600. (After Zopf.) 



also occupied himself with it. Associated with this colourless species is a second 

 (coloured) species, discovered by W. ZOPF (VIII.) in a Silesian river receiving 

 the drainage from a sugar-works. The cells of this, Sphcerotilus roseus, contain 

 a yellow and a red colouring-matter, which circumstance is of itself sufficient to 

 distinguish it from all other (colourless) species of thread bacteria hitherto 

 mentioned. 



