CLASSIFICATION OF BACTERIA 13 



in pairs, -when they are known as Diplococci, Some cocci 

 are not always round, but somewhat oval ; when in process 

 of division they are necessarily more or less elongated. 



(2) Streptococcus, or Chain Cocci. — Division in one direc- 

 tion. The cocci are arranged in chains or bead -like 

 formation. 



(3) Merismopedia, or Pediococcus. — Division in two direc- 

 tions, forming groups of four, which remain associated in a 

 single plane, giving rise to tablet-like layers of cells. 



(4) Sarcina, or Packet-cocci. — Division in three direc- 

 tions, forming packets of eight or more elements, which 

 remain associated in more or less cubical masses. 



(5) Ascococcus. — Cocci in groups, surrounded by a gela- 

 tinous intercellular substance. This form is often known as 

 a Zoogloea. 



(6) Leuconostoc. — Cocci singly or in chains, surrounded 

 by a gelatinous envelope, forming a Zoogloea. 



Bacteriaceae — (1) Bacillus. — The straight, rod-like bac- 

 teria ; reproduction by binary division, or by resting spores ; 

 are, as a rule, motile. When, owing to spore formation 

 in the end of the rod, it gives rise to peculiar enlargement 

 resembling a bottle, the bacillus is known as a Clostridium. 



(2) Bacterium. — Generally shorter than, the bacilli, and 

 form no spores and possess no power of locomotion. It is 

 difficult to draw a sharp line between these two classes. It 

 frequently happens that these characteristics are not all 

 present in one species. Some are motionless, and yet form 

 spores. Continually species are being taken out- of this 

 class, to' be included in the bacilli. 



(3) Spiro -bacteria, or Spirilla. — -These form curved or 

 spiral filaments, rigid or flexible ; reproduction by binary 

 division and by spore formation; movements rotatory in 

 the direction of the long axis of the filaments, or they may 

 be motionless. 



