CHAPTER III. 



CLASSIFICATION. 



THE classification of the Schizomycetes is at present in a 

 remarkable transition state. That presented in the fore- 

 going pages, Chapter I., is due in the main to Cohn, and 

 has been supported by Koch, Van Tieghem, and others. 

 It is founded upon the idea, which would obviously occur 

 first to an observer, that all the various morphologically 

 or physiologically distinct forms belong to different species. 

 This idea received strong apparent support from Koch's 

 experiments (Jour. Roy. Micr. Soc., 1881, pp. 950-952, 

 and Quart. Jour. Micr. Set., 1881, pp. 651-654) in the 

 cultivation of bacterial forms upon gelatine of sufficient 

 consistence to keep the progeny of any one germ in its 

 immediate neighbourhood, and thus prevent that mixture 

 of diverse forms which has been so often perplexing. 

 Under these conditions, according to Koch, Micrococcus 

 produced nothing but Micrococcus, Bacterium nothing 

 but Bacterium. 



In opposition to this theory, Na'geli, Billroth, Hallier, 

 Hoffmann, Liiders, Cienkowski, Neelsen, Zopf, Haberkom, 

 and others maintain that in most cases a Schizomycete 

 passes through a series of adaptive forms that a Micro- 



