166 PHYLUM I. MYXOPHYCEAE 



ORDER BACTERIALES. The Bactmbia 



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 

 generally in Nature that their presence is 

 almost universal. They reproduce by fis- 

 sion with such astonishing rapidity that in 

 '°'bacteria.^^''* a 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 Ijodies. By the breaking of the filaments into 



