EUTHALLOPHYTA— SCHIZOPHYTA 



161 



of the cell by the transformation of vegetative cells into endospores, or by the 

 transformation of ordinary vegetative cells into arthrospores ; nuclei absent, 

 but a so-called "central body" occasionally present ; coloring matter equally 

 distributed. This sub-division includes the Bacteria or Schizomycetes and the 

 Blue-green Algae or Schizophyceae. 



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Fig. 20. Schizophyta. Shizomycetes. Bacteria with flagellae. 1. Planococcus citrus 

 2. Pseudomonas pyocyanea. 3. Pseudomonas syncyanea. 4. Bacillus typhi. 5. Spirillum 

 comma. 6. Spirillum rubrum. Fig. 1-6x1000; all after Migula. 



SCHIZOMYCETES 



Schizomycetes is one of the two classes of the sub-division Schizophyta. All 

 the members of this sub-division are characterized by having no known sexual 

 method of reproduction, multiplying by means of simple fission or cell division. 

 The bacteria are distinguished from the first, or Schizophyceae, by the absence of 

 the blue-green coloring matter which is characteristic of these forms. The two 

 sub-divisions approach each other very closely at some points, particularly among 

 the branched bacteria. The shape of the bacteria is used as the character in the 

 separation of the families. They are either rod-shaped, and unbranched, 

 spherical, bent, or spiral and straight and branched, and v/ith or without sheath- 

 ing, covering, or membrane. Five families are distinguished by Migula. Some 

 of these contain considerable numbers of bacteria important from their toxigenic 

 properties. 



Bacteria are among the smallest of living beings, some undoubtedly being 

 so small that they cannot be seen with the highest powers of the microscope. 

 Others are large enough so that they may be seen as minute specks by the naked 

 eye. In other words, they vary from less than 1/10 fj. to 100 fx. They may be 

 arranged in the case of the rod-shaped forms or bacilli, either singly or in chains. 

 The same is true of the spirilla, or spiral forms. The cocci or spherical forms 

 may be single, in pairs, in regular mass of 4 and multiples of 4, in chains, in 

 irregular clusters, or imbedded in gelatinous mass forming zoogloeae. Multi- 



