88 SULPHUR BACTERIA 



A committee of the Society of American Bacteriologists 

 (Bergey, Breed, Hammer, Harrison, and Hunton) prepared 

 a Manual of Determinative Bacteriology in 1923, and in the 

 classification of the sulphur bacteria they have adopted 

 Buchanan's scheme without change. The same applies to 

 Pribram's classification which appeared in 1929. 



Ellis's Classification of the Sulphur Bacteria. 



Buchanan's classification has the merit that it takes 

 cognizance of all the sulphur bacteria that have been dis- 

 covered in recent years. The present writer's scheme has 

 been drawn up after an inspection of the stability of the 

 attributes used in the classification of bacteria in general, and 

 of the sulphur bacteria in particular. Also the life-histories of 

 these bacteria have been studied, and observations have been 

 made on the majority of the organisms included in this group. 

 In this way the defects of the earlier systems have been made 

 manifest, and so far as has been possible, they have been avoided. 

 As a quarter of a century has elapsed since a scheme of classi- 

 fication of the sulphur bacteria has been drawn up after a 

 special investigation of the group, there is much to rectify. 

 The acceptance of pleomorphism is a fact of great importance 

 in framing a scheme of division. The instability of dimensional 

 division in space is also a fact that strikes at the roots of former 

 classifications, because of the im.portance attached to it. The 

 genus Lankesteron has been created because it was felt that 

 the organisms examined respectively by Lankester, Warming 

 and Zopf were different species of a highly pleomorphic genus 

 of the sulphur bacteria. Within the last twenty-five years, 

 since the last classification was made after a detailed study 

 of the group, several additions have been made to the group, 

 and the author has added still another genus, namely, Thio- 

 porphyra. In addition a slight change has been made for the 

 ake of preserving uniformity of nomenclature. The Spirilla 

 genera of the sulphur bacteria have been divided into two, 

 namely, Thiospirilliim (colourless), and Rhodo-thiospirillum 

 (coloured). The term Thio-pseudomonas was also introduced 



