CLASSIFICATION OF BACTERIA 19 



On the other hand, the formation of the genera is not 

 consistent, those of the Coccacese being based on the 

 mode of division of the cells, while those of the Bacte- 

 riacese are based on the morphology of the cells. 



Another classification is that proposed by Migula : l 



The Bacteria are divided into two orders : the Eubacteria 

 bacteria proper -the cells of which contain neither sulphur 

 granules nor a colouring matter, bacterio-purpurin ; and the 

 Thiobacteria, the cells of which contain sulphur granules and may 

 be coloured with bacterio-purpurin. The Eubacteria are divided 

 into five families : (1) Coccaceae, (2) Bacteriacese, (3) Spirillacese, 

 (4) Chlamydo-bacteriaceae, and (5) Beggiatoaceae. These, again, 

 are subdivided into many genera, based partly on the mode of 

 division and partly on the number and on the arrangement of the 

 flagella upon the organisms. The Coccacese globular cells 

 contain the genera Streptococcus, Micrococcus, Sarcina (non- 

 motile), and Planococcus and Planosarcina (motile) ; the Bac- 

 teriacese are defined as long or short cylindrical rods, straight and 

 never spiral ; division in one direction only after elongation of 

 the rods ; and this family has three genera : (a) Bacterium 

 non -flagellated cells, often with endospore formation ; (b) Bacillus 

 cells possessing both lateral and polar flagella, often with endo- 

 spore formation ; (c) Pseudomonas cells with polar flagella only, 

 rarely endospore formation. The Spirillacese are curved or spiral 

 rods, and include (a) Spirosoma, non -motile forms, (b) Microspira, 

 motile forms with one polar flagellum, (c) Spirillum, motile forms 

 with two or more polar flagella. 



A valuable discussion by Buchanan on the classification 

 of Bacteria and an attempt to reduce it to a scientific 

 system will be found in the volumes of the Journal oj 

 Bacteriology. The following is an outline of the system 

 proposed by an American Committee in that Journal 

 (vol. v, 1920, p. 191) : 



A. ORDER MYXOBACTERIALES. 



Cells united during vegetative stage into a pseudo-plasmodium. 

 Resting stage cystic. 



1 System der Bakterien, 1897. 



22 



