178 BACTERIOLOGY. 



Cohn noted, in spite of placing them with the 

 Algce, that the absence of chlorophyll connected the 

 Bacteria to Fungi, and we find Nageli subsequently 

 adopting this view, and employing the term Schi- 

 zomycetes. 



Billroth, in 1874, disputed the division into 

 species, and considered that all the forms described 

 by Cohn were but developmental forms of one micro- 

 organism, Coccobacteria septica. In the following 

 year Cohn answered the criticism of Billroth, and 

 produced a second classification, in which he still 

 maintained that distinct genera and species 

 existed. The genera Cohn considered to be dis- 

 tinguished by definite differences in shape, which 

 were adhered to throughout life, while some special 

 feature, as a difference in size or physiological 

 action, or some minute difference in form, deter- 

 mined the various species. Cohn illustrated, by his 

 well-known comparison of a sweet and a bitter 

 almond the appearances of which are similar but 

 the properties very different, that a distinction 

 into species might depend upon a difference in 

 physiological action only. Others strongly sup- 

 port Cohn's views. By cultivating various micro- 

 organisms through several generations, many 

 conclude that a micrococcus cannot be trans- 

 formed into a bacterium, or a bacterium into a 

 bacillus or spirillum. Koch does not believe- 

 and in this he is supported by Klein that a 

 bacillus can change its nature, and be converted 



