THE PRINCIPLES OF CLASSIFICATION 83 



2. Peritrichime. — ^Cells spherical, or rod-shaped, never 

 spiral. Either peritrichous or non-motile. Not typically 

 water bacteria. Energy not by oxidation processes. 



Seven families are included in the first order : — 



Oxydobacteriacece. 



Luminibacteriacece. 



Reducibacteriacece . 



* Thiobacteriacece. — Containing sulphur but no bacterio- 



purpurin. 



* Rhodobacteriacec?. — Containing sulphur and bacteriopur- 



purin. 

 Actino)}Lyces. 



* Triihobacteriacere. — Water forms. Absence of mycelium. 



Filamentous. 



Four families are included in the second order : — 



Acidobacteriacece. 



Alkalibacteriacece. 



BntyribacteriacecE. 



Putribacteriacecs. 



All the sulphur bacteria then known were placed in one or 

 other of the three families marked with an asterisk. 



Family Thiobacteriacece : 



1. Cells not spiral. 



A. Cells rod-shaped or not spherical. 



* Snlphomonas. — Autotrophic, rod shaped. 

 Thionionas. — heterotrophic, oval. 



B. Cells spherical. 

 Thiococcus. — Cells spherical. 



2. Cells spiral. 



Thiospirillum. 



Family Rhodobacteriacece : 



Rhodoinoiias [Chromatium). 

 Rhabdotnonas [Rhabdochromatium) . 



* Sulphomonas is not rightly included in ThiobacteriacecB as the cells do 

 not store sulphur. 



6* 



