154 



OUTLINES OF BACTEEIOLOGY 



conditions arise which enable them to form filaments and zoogloeae. 

 He also maintains that a mature filament is often produced, not by 

 the division of a single thread, elongated from a coccus into small 

 cells, but rather by the arrangement of cells formed from different 

 cocci into a row. The whole life-history of this organism is not 

 yet thoroughly elucidated. It is widely distributed, probably in the 



Fig. 89. — Crenothrix polyspora. 



coccus form, but its identification, except when, as at Cheltenham 

 in 1896, it multiplies to an inordinate extent, is extremely difficult, 

 if not impossible. 



Another well known organism belonging to this group is Cladothrix 

 dichotoma (Cohn), which was discovered by Cohn in 1875. It has the 

 same habitat as Crenothrix polyspora. In 1888, in conjunction with 

 this species, it caused much trouble in the Rotterdam Waterworks. 

 Its general appearance is represented in Fig. 90. The threads of the 

 organism form a tree-like tuft of threads. In Fig. 91 the threads 

 are represented on a larger scale. As is the case with Crenothrix, 

 each thread is made up of a number of cylindrical cells, all held 

 together by a common membrane. The branching is of a peculiar 

 nature, each branch being formed by the slipping aside of one cell 

 in a thread, which then elongates and divides to form a new 

 thread, whilst still partly attached to the parent thread. We 



