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 



] 



in/ f § § 



l I I 



£ £ 88 Si 



I 8 i S 



8 8 S 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 



1 Untersuchungen iiber Bakterien, 1894. Berlin. Separatabdruck 

 aus den Jahrbticnern fur wissenschaftl. Botanik, XXVII, 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. 



