168 THE MICROSCOPICAL NEWS. 
BACTERIACEA. 
I. Cells not united into filaments, separating immediately after, 
division, or in couples, free or united into colonies (zoogloea) by a 
gelatinous substance. 
A. Cells dividing in one direction only. 
a. Cells globular : Aftcrococcus. 
8. Cells elliptical or shortly cylindrical : Bacterium. 
B. Cells dividing regularly in three directions, and thus forming 
cubical families, having the form of packets strung crosswise, and 
consisting of 4, 8, 16, or more cells: Sarcina. 
II. Cells united into cylindrical filaments. 
A. Filaments straight, imperfectly segmented. 
a. Filaments very fine and short, forming rods: acillus. 
8. Filaments very fine and very long: Lepfothrix. 
y. Filaments thick and long: Beggzatoa. 
B. Filaments wavy or spiral. 
a. Filaments short and stiff. 
(a) Filaments slightly wavy, often forming woolly flocks : 
Vibrio. 
(2) Filaments spiral, stiff, moving only forwards or back- 
wards : Speridlum. 
B. Filaments long, flexible, with rapid undulations, spiral 
through their whole length, and endowed with great 
mobility: Spzrochete. 
Prof. v. Nageli considers that any division of these organisms into 
species can be of no scientific value, since the same species may 
assume different forms in different media and conditions of life, and 
all known distinct forms are connected by intermediate links. Dr. L. 
Rabenhorst, in arecent work on the “ Avyptogamen Flora” gives full 
descriptions and measurements of the species which he has recog- 
nized or which have been described by others. He makes an 
attempt at arranging them, in some of the genera, with regard to 
their qualities or functions, as colourless, pigment-forming, those 
producing fermentation, and those that are pathologically active. 
We learn that the round or oval cells of Micrococcus (Cohn) vary 
according to the species from .3 to 2 w in length (1 w = ss¥qo Of 
an inch), and that a ‘‘ doubtful species ” may, in the act of division, 
attain the length of 6 or 7 ». One pigment-forming species (AZzcro- 
coccus prodigiosus, Cohn) is the cause of the so-called ‘‘ blood-rain ” 
on bread, the “host,” &c. Another, the AZ. wree of Cohn, is the 
agent of ammoniacal fermentation ; and another (JZ. crepusculum) 
appears with Bacterium termo in nearly all organic substances un- 
dergoing decay. The pathogenic species contain JZ. vaccine, the 
active element of vaccine lymph and small-pox ; JZ. diphtheriticus, 
found on the mucous membrane in the subjects of diphtheria ; and 
M. septicus, found in the blood and on wounds in cases of blood- 
