CBENOTHBIX POLYSPORA. 463 



contamination of water, but not specific (perhaps from 

 sulphite wood-pulp factories or the like). According to 

 Winogradsky, ZopI has improperly included in this variety 

 a large number of other rose-colored inhabitants of water. 

 Jegunow (C. B. ii, 279) has reported many interesting 

 observations regarding another sulphur bacterium, whose 

 classification is still undetermined, but it most likely 

 belongs to the spirilla. 



Crenothrix polyspora. Ferd. Cohn. 



(Cohn's Beitrage, Bd. I, H. II, 130.) 



Long, rigid, unbranched threads, consisting of a single 

 row of low cells, unpigmented, included by a membrane 

 which is very thin at the younger parts of the thread and 

 thick at the older parts. The membrane is a product of 

 the cuticle of the cell. In the membrane is deposited 



Fig. 26. — Crenothrix polyspora. Cohn. 



some iron hydroxid or carbonate, which stains it brown. 

 Sometimes also the membranes for considerable lengths 

 are surrounded by a yellow, ferruginous mass with a luster 

 like oil, so that macroscopic, brownish flakes appear. 



The thickness of the threads varies from 1.5 to 5.2 /i, it 

 often being easily recognized that the older part of the 



