THE BACTERIA IN GENERAL 23 



and the numerous individual forms are united into slimy, skin-like 

 or lumpy masses known as zoogloea. 



The interior of the cell shows no differentiation into nucleus and 

 cytoplasm, but the nuclein in certain forms seems to be scattered in 

 the plasma (Fig. 5). Considerable diversity of opinion exists as to the 

 nature of the cell substance of bacteria. The uniform staining of the 

 cell by ordinary methods suggests that the cell substance is all cyto- 

 plasm without nucleus. An opposite opinion is that the cell substance 

 is composed almost entirely of nuclear matter (chromatin) with perhaps 

 a thin layer of ectoplasm. Another view is that 

 of Zettnow (Zeitschr. f. Hyg., 1899: 18), who regards 

 the cell body of bacteria as composed largely or 

 almost wholly of chromatin mingled with varying 

 amounts of cytoplasm. This, however, can be said, 

 that it is fairly certain that bacteria contain both 

 chromatin and cytoplasm which vary in amount and 

 position in different cells (Fig. 5). The cell mem- Fig. 5.— i,c/!)'o- 

 brane is mostly colorless; seldom does it appear BTg^glai'oT"aibl' 

 greenish or rose-red, as in the purple bacteria. Bacteria with a cen- 

 When colonies of bacteria are colored, the coloring ch^'romatln °g'rtTns 



matter is an excretion product. which are considered 



Locomotion. — The movement of many bacteria is equiv^rienTof^a 

 a true movement from place to place, not merely a nucleus. (From 

 Brownian movement. It is accomplished in nearly f^l"'sfLTE7uion, 

 all cases by the presence of cilia, or.flagella, which p. 91- After 

 by some are considered to arise directly from the ^"^^'^''^^■^ 

 cell membrane," by other investigators to arise from the ectoplasm 

 within; its origin in some way associated with a blepharoplast. Which- 

 ever view is the correct one, the motile filaments can in some large 

 spirilla be seen in the living unstained organism, but generally it re- 

 quires special methods of treatment and staining to make them out. 

 Great differences exist as to their distribution. Some forms, as the 

 cholera bacillus, have a single flagellum at one pole {monotrichous) ; 

 others, as many spirilla, have a flagellum at each pole {amphitrichous) ; 

 others, as certain large spirilla, have a tuft at one pole {lophotrichous) ; 

 while others have cilia covering the whole cell, as the typhoid organism 

 {peritrichous) . Many organisms are without cilia, or flagella {atrichous) , 

 and hence are non-motile. 



