64 BACTERIOLOGICAL EXAMINATION OF WATER. 



diffused growth. It is a small, highly motile bacillus, which is 

 not stained by Gram. It does not form spores. 



B. Ochraceus. 



This organism was first described by Zimmermann. 



In the depth of gelatine plates the colonies are small 

 and round and have a pale yellow colour; on the surface 

 they show a deep yellow-ochre coloured centre surrounded by a 

 thin film of a light yellow colour. Later, processes grow out 

 from the centre into the margin and the colony becomes sur- 

 rounded by a zone of liquefaction. On agar and potato it forms 

 a yellow-ochre coloured growth. It liquefies a gelatine-stab 

 horizontally with a deposit of yellow ochre pigment. It also 

 powerfully reduces nitrates. In glucose-gelatine there is no gas 

 formation. It is a thin, slowly motile bacillus ; grows best at 

 20 C. and does not form spores. It is not stained by Gram's 

 method. 



B. Tremelloides. 



Found by Tils in the Freiburg water supply. The colonies 

 in the depth of gelatine are smooth- rimmed yellow dots; on the 

 surface they form thin yellow expansions with an irregular 

 margin. In gelatine-stab there is a growth on the surface 

 resembling a colony, and along the stab a thin yellow growth 

 consisting of isolated colonies. On agar and potato it forms a 

 yellow growth. There is no gas formation in glucose-gelatine. 

 Indol is not produced in peptone, and milk is not coagu- 

 lated. It is a small, thin, motile bacillus. Gelatine is slowly 

 liquefied. 



Yellow Bacillus. 



Described by Lustig. The colonies in gelatine plates are 

 small round grey dots, which under a low power have a golden- 

 yellow colour and a serrated margin ; from the periphery of the 

 colony delicate extensions pass into the surrounding gelatine ; in 

 about ten days the colony rests in a cup of liquefied gelatine. 

 In gelatine-stab it forms a yellow slimy growth on the surface, 

 along the stab there is a yellow growth with short lateral 



