BACTERIA. 
1 7 
has come from the reproduction of one parent—a 
bacterium. Fig. 6. 
Under the microscope these bacteria show three 
principal shapes. Fig. 7. One like a short, round 
stick or rod, is called a bacillus and bacilli for the 
plural. Fig. 7b. Another is ball-shaped, called coccus 
or cocci for the plural (the third c sounding like s). 
Fig. 7a. A third form which resembles one turn or 
more of a screw is called a spirillum 
or spirilla for the plural. Fig. 7c. 
These typical forms may shade 
into each other. The bacilli may be 
long or short, with pointed, blunt, 
or square cut ends. They may be so 
short and plump as to closely re¬ 
semble a coccus. Fig. 8. The spi¬ 
ral forms may curve very little or 
have decided and numerous twists. 
Fig. 9. 
Bacteriologists do not always agree 
as to which class a newly found indi¬ 
vidual should belong, and to the housewife it makes 
no difference. 
The bacteria are so simple in structure and so diffi¬ 
cult to study that there is little to describe. Each 
consists of a single cell, so far as is known. This 
seems to have a denser portion on the outside, which 
forms a cell wall and may be cellulose as in the higher 
plants. 
This simple cell of protoplasm or “foundation stuff” 
Fig. 8. 'Bacilli or 
Rod-shaped Bacte¬ 
ria. 
Shape of 
Bacteria 
Structure 
Bacteria 
