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’. 5° 3 °°. Mherobacteria. 
WMesococcos 's)..6.. s 6 4 Soe 4 Mesobacteria. 
Meracoccos + °. ©. \. 6 . 5:00 se’ Megabacteria. 
And varieties of association which give rise to the 
following names : — 
Monococcos’’s: -\)' s. 285.1. ~  Monobacteria. 
Diplococcos . +)... 4) wis) Diplobaeteria. 
Streptococcos . . . . .  Streptobacteria. 
GriIACOCCOS: .. Ss, ».d-%-.4e - Ghabacteria. 
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- 
maces; and, no longer distinguishing the bac- 
teria as a special family, he distributes his 
different genera in a group, which he calls Schi- 
zophytes, which includes the greater part of the 
