20 MORPHOLOGY. 



and represented this abnormal division in streptococci. It 

 occurs very frequently ; indeed, we have often seen it. 



Regarding the structure of the bacterial cell, much 

 has been recently written. I must limit myself to what 

 seems to me the most probable. 



According to Alfred Fischer, 1 the conditions are very 

 simple (Fig. 3): The bacteria consist of a cell-membrane, 

 a protoplasmic layer, and a central fluid. Regarding a 

 nucleus see below. In saline solutions (sodium chlorid, 

 potassium nitrate, etc. ) there occurs, the more concentrated 



I I 



ll T 



S 



f 9 8 



a b 



Fig. 2. Pseudodichotomy : a, In bacilli ; b, in streptococci. 



Protoplasmic layer. 



Membrane. 



Spaces filled with cell-juice. 



Fig. 3. Bacillus oxalaticus Migula (after Migula). 



the solution the more rapidly, through abstraction of 

 water, a '* plasmolysis," i. e., a contraction of the mass 

 of protoplasm with partial separation from the cell-mem- 

 brane. 2 Thus are explained many clear vacuoles which 

 occur in an ordinary cover-glass preparation of many bac- 

 teria (for example, B. typhi), and which were formerly 



^ntersuchungen iiber Bakterien, 1894. Berlin. Separatabdruck 

 aus den Jahrbuchern fur wissenscbaftl. Botanik, xxvn, Heft 1 ; and 

 Untersuchungen iiber den Bau der Cyanophyceen und Bakterien., 

 Jena, 1897. 



2 Frequently the drying on the cover-glass is sufficient to produce 

 a picture of plasmolysis. 



