154 NATURE OF BACTERIA 



one. By the formation of sporangia numerous dust-like spores 

 are produced that are capable of germinating and forming 

 zoospores that increase rapidly by division. The aggregation of 

 the zoospores results in the formation of the plasmodium which 

 after a time completes the life history by creeping upon suitable 

 dry objects and forming sporangia. The mingling of the zoo- 

 spores in the formation of the plasmodium is not a sexual process, 

 since the nuclei do not fuse, but Olive has shown that the spores 

 are formed in the same manner as in plants characterized by 

 sexual reproduction and that therefore there must be a sexual 

 fusion of the nuclei at some time in the life history of the plas- 

 modium. The structure and life history of these plants is so 

 simple that it is possible that they may have been derived from 

 forms allied to the first forms of life upon the earth. The 

 common occurrence among simple animals and plants of motile 

 stages or zoospores in their life history certainly suggests that 

 possibly such forms may represent the first appearance of living 

 matter. 



Subdivision 2. Schizophyta or Bacteria and Blue Green Algae 



As in the preceding group these forms are extremely simple 

 and possess some characters suggestive of the lower forms of 

 animal life. They have received the name of Schizophyta, mean- 

 ing splitting plants, owing to their common method of repro- 

 duction by division of the cell into two equal parts. There are 

 two important classes of Schizophyta: A, Bacteria; B, The Blue 

 Green Algae. 



CLASS A. BACTERIA 



62. The Structure and Nature of Bacteria. Bacteria are com- 

 monly known by such vague terms as microbes and germs. They 

 are, however, unicellular plants that are of almost universal dis- 

 tribution, though more abundant about dwellings and less com- 

 mon in cold countries, at high altitudes and on the sea. They 

 include the smallest and simplest forms of plants, ranging from 

 scarcely 1/50,000 in. to 1/10,000 in. in diameter (Fig. 91). Such 

 forms would have many times more room in a drop of water 

 than a whale would find in New York harbor. So minute and 



