166 PHYLUM I. MYXOPHYCEAE 
ORDER BACTERIALES. Tue Bacteria 
226. The Bacteria, which are here regarded as degen- 
erated chlorophyll-less Blue Greens, are so important 
that they require a somewhat fuller treatment. They 
are the smallest of living things, some being as small as | 
0.0005 millimeters (1/50,000 inch), or even smaller. Al- 
though typically filamentous they break up easily into 
one-celled or few-celled forms, in which condition they 
are most commonly found. In some species they occur 
as minute rounded cells (‘‘cocci’’), in others elongated 
(then called “‘rods’’), and in still others they are more or 
less curved. They are frequently provided with one or 
more cilia or flagella by means of which they are motile. 
227. Bacteria are found in great numbers in the watery 
parts of decaying organic matter, causing various kinds 
of fermentation, and in fact they occur so 
Gor generally in Nature that their presence is 
2 almost universal. They reproduce by fis- 
=—— __ sion with such astonishing rapidity that in 
Fra. 63- several 4 short time they swarm in any exposed 
substance which is capable of furnishing 
them with food. Some of the species live in the 
watery juices of plants and animals, causing various 
diseases. However, of the hundreds of species known, 
the great majority are harmless, or actually beneficent. 
228. Some bacteria can endure high temperatures, 
especially in the spore state, and frequently appear in 
tightly closed vessels whose contents have been boiled. 
Some people have been led to explain their appearance 
under such circumstances by ‘spontaneous generation”’; 
but thus far the facts are capable of other explanation. 
229. The proper spores of bacteria (endospores) are 
produced singly within the cells, and are thick-walled, 
rounded bodies. By the breaking of the filaments into 
