HISTORICAL. . 23 



fact which in his opinion demonstrates conclu- 

 sively their relationship. Each of these two 

 forms can also present variations of size, in ac- 

 cordance with which he establishes the following 

 divisions : 



Micrococcos Microbacteria. 



Mesococcos Mesobacteria. 



Megacoccos Megabacteria. 



And varieties of association which give rise to the 

 following names : 



Monococcos Monobacteria. 



Diplococcos Diplobacteria. 



Streptococcos Strep tobacteria. 



Gliacoccos Gliabacteria. 



Petalococcos Petalobacteria. 



Ascoccos. 



The following year (1875), Cohn, in the second 

 part of his " Researches " upon the bacteria, criti- 

 cised the opinions expressed by Billroth in the pre- 

 ceding memoir. Cohn believes that we should 

 regard as distinct genera and species all the bac- 

 teria having a particular form and acting differ- 

 ently as ferments, so long as the proof of their 

 identity has not been demonstrated in an evident 

 manner. Coming back also to the affinities and 

 classification of these organisms, he insists anew 

 upon their near relationship to the Phycochro- 

 macese; and, no longer distinguishing the bac- 

 teria as a special family, he distributes his 

 different genera in a group, which he calls Schi- 

 zopkytes, which includes the greater part of the 



