CHAPTER II. 



Morphology 1 of bacteria Grouping Mode of multiplication Spore-forma- 

 tion-Motility. 



IN structure the bacteria are unicellular, and are seen 

 to exist as spherical, rod- or spiral-shaped bodies. 

 They always develop from pre-existing cells of the 

 same character and never appear spontaneously. 



The classifications of the older authors and of the 

 botanists are usually upon purely morphological pecu- 

 liarities, and, because of slight variations that are seen 

 to occur in the size and shape of one and the same spe- 

 cies, are more or less complicated. The present tendency 

 is to simplify this morphological classification, and to 

 bring the bacteria into three great groups, with their 

 subdivisions, the members of each group being deter- 

 mined by their individual outline, viz., that of a sphere, 

 a rod, or a spiral. 



To these three grand divisions are given the names 

 cocci or micrococci, bacilli, and spirilla. 



In the group micrococci belong all spherical forms, 

 L e., all those forms the isolated individual members of 

 which are of the same diameter in all directions. (See 

 Fig. 1, a b c d.) 



The bacilli comprise all oval or rod-formed bacteria. 

 (See Fig. 2.) 



To the spirilla belong all organisms that are curved 



1 Morphology : Pertaining to shape ; outline. 



