8 BACTERIOLOGY. 



peripheral layer, b, the mantle of cytoplasm, the red granules, e, 

 are chromatin grains and the blue reticulum is linin. 



2. Spirillum undula in process of division. The nucleus, c, 

 lies next to the membrane ; the cytoplasm, b, occupies a rela- 

 tively small part of the cell and is found at the poles and in the 

 middle. 



3. A bacterium found in stagnant water ; the cell is almost 

 wholly nuclear substance, c, and the cytoplasm, b, is confined 

 to a small amount at one pole. 



4. Cladothrix dichotoma ; portion of filament, /=sheath. 



5. Chromatium Okenii in conjugation (after F. Forster), s = 

 sulphur grains ; ^ = the channel of connection between the con- 

 jugating cells. 



o. a and ft, Chromatium Okenii ; c, B. lineola (after a photo- 

 graph) ; linear magnification about 900. 



be regarded as undeveloped nuclei. (Fig. i.) 

 Ernst was the first to observe these granules 

 which stained red and not blue with methylene 

 blue. A. Fischer z has, however, recently main- 

 tained that this coloration was due not to a 

 chemical peculiarity, but to physical conditions. 

 In his opinion the substance of a bacterial cell, 

 in spite of the fact that it stains after the man- 

 ner of nuclear substance, behaves on the whole 

 like the cytoplasm of a plant cell. When it is 

 plasmolyzed by strong salt solution, alcohol or 

 heat, it adheres to the cell wall and breaks up 

 into irregular masses or even at times into 

 masses so regular as to present the appear- 

 ance of " central bodies " or polar granules 

 (Fig. 2). The " central body " of Butschli is 

 therefore considered by Fischer as merely 

 plasmolyzed cytoplasm. Whatever be the 

 truth of the matter, the bacterial cell is cer- 

 tainly not the simplest form of cell that may 



1 Ueber den Ban cler Cyanophyceen und Bakterien, Jena, 1897. 



