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,^ 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 



If/ 



©i in SQ Q^ 



<3 g oo OS 



3 Q Q Q 



S o 2 D 



a b 



Fig. 2.— Pseudodichotomy : a, In bacilli ; 6, in streptococci. 



■Protoplasmic layer. 

 Membrane. 

 Ipaces filled with cell-jiiice. 



Fig. 3. — Bacillus oxalatiou.s 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 



'Untersuohungen iiber Bakterien, 1894. Berlin. Separatabdnipt 

 ausden Jahrbiichern fiir wissenschaftl. Botanik, xxvii, Hett 1- ad 

 Uutersuchungen iiber den Ban der Cyanophyceen und Bakterien 

 o&n&j IHyT. *' 



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

 a picture of plasmolysis. 



