78 General Notes. - Han, 
and grouping of them, and in 1838 had proposed at least sixteen 
species, distributing them into four genera.” Cohn’s work (1853- 
1872) gave us the first really accurate knowledge of these organ- 
isms. He assumed the practical constancy of the forms ‘met 
with, and accordingly described them as species and genera, 
taking form for his principal character. Later students of the 
Bacteria have shown that Cohn’s species and genera often occur 
as phases in the life-history of a particular bacterium. What 
the specific limits are in many cases has not yet been determined. 
Zopf showed several years ago that “minute spherical cocci, 
short rodlets (‘Bacteria’), longer rodlets (‘ Bacilli’), and fila- 
mentous forms $ Leptothrix’), as well as curved and spiral 
threads (‘ Vibrio,’ ‘ Spirilum,’ etc.), occur as vegetative stages in 
one and the same schizomycete. 
With these facts before us, it is at once evident that Cohn’s 
classification breaks down entirely. No stable arrangement can 
be hoped for in the present state of our knowledge. Accord- 
ingly, a good deal of attention is now directed to the study of 
the various vegetative and reproductive states, including also 
the details as to their parasitic and saprophytic habits, and their 
deportment noder cultivation. The chief vegetative forms are 
the followin 
Cocet, a or spheroidal cells: 
Rods or rodlets, slightly, or more considerably elongated cells. 
sia ener elongated cylindrical cells, united end to end in 
long thre 
Soe or ae al forms, rods or filaments more or less curved. 
To these should be added the so-called zooglcea, or resting 
stage, in which the cell-walls swell up and form a gelatinous 
matrix. Spores are known to occur in most Bacteria, and these 
have been observed to germinate in several forms, Two principal 
types of spore formation are distinguished, viz.: 1, by the break- 
ng up (fission) of the filament into its ultimate segments or 
joints (arthrospores); 2, by the formation of spores within the 
cell or filament (endospores). 
The provisional outline of a classification of Bacteria given is 
a modification of De Bary’s, as follows, 
Group A. ASPOREZ. 
No spores distinct from the vegetative cells. 
`. I. Coccace#, including the genera, 1, Micrococcus ; 2, Sarcina ; 
3, Ascococcus. 
Group B. ARTHROSPOREZ. 
res uced by segmentation. 
er be inom ie aee 4, Bacterium; 5, Leu- 
