CLASSIFICATION OF THE BACTERIA. 61 



phenomena of reproduction by fission or by 

 spores, as the only character which can serve to 

 establish our natural genera; but, unfortunately, 

 this has only been ascertained for a small number 

 of bacteria, the Bacillus anthracis, for example. 



The genera of bacteria cannot have the same 

 significance as among animals and superior vege- 

 tables ; they can only be established in accordance 

 with the most prominent characters, reserving the 

 feeble modifications of these generic forms as 

 specific characters. 



Are there distinct, well-defined, species among 

 the Bacteria ? 



The microscopists have given the most diverse 

 opinions upon this subject. Miiller, Ehrenberg, 

 Dujardin, Davaine, have admitted the specific dis- 

 tinction of the numerous vibrioniens which they 

 have described. Davaine, however, raises some 

 doubts as to the absolute value of the species 

 established in his time. " Those which are de- 

 scribed to-day by the classifiers," he says, " ought 

 to be considered as the expression of types under 

 which are hidden a certain number of distinct 

 species." 



Cohn dwells still more upon the impossibility, 

 in which we are to-day, of distinguishing with 

 certainty genera and species among the bacteria. 

 However, he is convinced that the bacteria are di- 

 vided into species as distinctly as the other plants 

 and inferior organisms. It is only the imperfection 

 of our means of observation which makes it impos- 

 sible to recognize these differences. This is above 



