GENERAL CHARACTERISTICS OF BACTERIA. 4] 
a. Single coccus, grouped irregularly. 
. Diplococeus, forming pairs. 
ce. Streptococcus, forming chains, often showing 
paired cocci. 
d. Tetracoccus, forming fours by division through 
two planes of space. 
e. Sarcina, forming packets of eight members by 
division through three planes of space. 
2. Bacillus. Oblong or cylindrical forms, having 
one dimension greater than any other, more or less 
straight, and never forming spirals. 
a. Single bacillus. 
6. Diplobacillus and streptobacillus, forming twos 
or longer chains, the bacilli attached end to 
end. 
c. Filaments, or thread-like growths, in which 
divisions into bacilli of the normal length 
are not apparent, or occur irregularly and 
transversely, to the long axis of the growth. 
3. Spirillum. Cylindrical and curved forms, con- 
stituting complete spirals or portions of spirals. — 
The determination of morphological characters for 
the description of bacteria should always be made from 
fully developed cultures; those which are too young 
may present, as already noted, immature forms, due to 
rapid multiplication, while in old cultures altered or 
degenerated forms may be observed. 
When growth is obtained upon different media, varia- 
tions, especially in size, may sometimes be observed. 
These differences should always be described, together 
with a note of the media upon which they were devel- 
oped and a statement as to whether such variation is a 
marked feature of the species under consideration, 
o~ 
