THE BIOLOGY OF BACTERIA 7 



pyocyaneus produces a green to olive colour on gelatine, 

 but a brown colour on potato ; the bacillus of Tetanus is 

 virulently pathogenic, and yet may not act thus unless in 

 company with certain other micro-organisms. Hence it will 

 at once appear to the student of bacteriology that, though 

 there is great need for classification amongst the six or 

 seven hundred species of microbes, our present knowledge 

 of their life-history is not yet advanced enough to form 

 more than a provisional arrangement. 



We know that bacteria are allied to moulds on the one 

 hand and yeasts on the other, and that they have no dif- 

 ferentiation into root, stem, or leaf ; we know that they are 

 fungi (having no chlorophyll), in which no sexual reproduc- 

 tion occurs, and that their mode of multiplication is by 

 division. From such facts as these we may build up a 

 classification as follows : 



VEGETABLE KINGDOM. 



Ill I 



Thallophyta. Muscineae. Pteridophyta. Phanerogamia. 



[= The lowest forms 

 of vegetable life. No 

 differentiation into 

 root, stem, or leaf.] 



Protophyta. 

 [= No sexual reproduction.] 



I | 



Algse. Fungi. 



[= Chlorophyll [= No chlorophyll.] 

 present.] 



I I I I I I I I I 



Schizomycetes 



[= multiplication by cell 



division or by spores] 



r (i) Coccaceae 1 round cells. 



(2) Bacteriaceae rods and threads. 



Bacteria. 



or 



(3) Leptotrichese. 



Cladotrichese. ) 



[ Higher Bacteria. 



1 Migula has recently (1896) suggested that the Schizomycetes should be subdivided into 

 Coccaceee, Bacteriacete^ Spirillacea (spirilla, spirochoeta), Chlamydobacteriacefe (Streptothrix, 

 Crenothrix, Cladothrix), and Beggiatoa. 



