SYSTEMATIC AND DESCRIPTIVE. 189 



in places twisted in irregular spirals with pseudo- 

 branchings. The development can be traced 

 from the cocci to rods and threads. The latter 

 are at the beginning simple threads, which were 

 formerly described as Leptothrix parasitica, or if 

 coloured by impregnation with iron, as Leptothrix 

 ochracea. Later they form false branches by 

 single rods turning aside, which by repeated 

 division lengthen into threads. A thread appears 

 to be first composed of long rods, then of short 

 rods, and lastly of cocci. The iodine reac- 

 tion must be applied to distinguish these forms, 

 especially when the sheath of the threads has 

 a yellow, rust-red, olive-green, or dark-brown 

 coloration. The cocci may grow into rods 

 while still in the sheath, and finally become lep- 

 tothrix threads, surrounded by a delicate gelatinous 

 sheath, from which the false branching proceeds. 

 Fragments may break off, which are actively motile, 

 and appear as vibrios, spirilla, and spirochseta- 

 forms. They may also occur in zoogloea. 



They are the commonest of all bacteria in 

 both still and running water, in which organic 

 substances are present. They are observed also 

 in the waste water of certain manufactures, such 

 as sugar. Artificially they can be cultivated on 

 infusions of rotting algae and animal substances, 

 forming on these media small tufts, about i 3 //,, 

 and floating masses. 



Cladothrix Fcersteri (Slreptothrix Forsttri, 



