2 BACTERIA 



^ (a) Streptococcus. Cells that divide in one direction only 



and grow in chains, "f 

 ^ (b) Micrococcus. Cells that divide in two directions, or 



irregularly; with this group staphylococcus may be 



classed. Also tetrads, which form into fours by division 



in two directions. j> 

 ^ (c) Sarcina. Cells that divide in three directions so that 



balelike packages, or blocks of eight are formed./^ At 



least one variety (Sarcina agilis) is motile, having flagella. 



Plates of cocci, one thick in the plane, are called "meris- 



mopedia." 



II.fBACTERIACE^. Rod bacteria are straight or slightly 

 curved. { Each cell is from two to six times as long as broad. 

 Division takes place in one direction only, and at right angles 

 to the long axis. Spores may be produced or may not. 

 They may have flagella, or may not. 



(a) Bacterium. Neumann Have no endospores. Migula 

 no flagella. 



(b) Bacillus. Neumann Have endospores, and often 

 grow in long threads. Migula- Flagella present at any 

 part of cell. 



(c) Pseudomonas. Have endospores very rarely. Fla- 

 gella only at ends. 



III. vSPIRILLACE^E. Spiral bacteria^ Unicellular, more or 

 less elongated. Twisted more or less like a corkscrew. 

 Cells are sometimes united in short chains.^ Generally 

 very motile. Spores are known in two varieties only. 



(a) Spirosoma rigidly bent. No flagella. 



(b) Vibrio or Microspira. Cells that are rigidly bent like 

 a comma, and have always one, occasionally two polar 

 flagella. 



(c) Spirillum. Are long and spiral, like a corkscrew, are 

 rigid, and have a bunch of polar flagella. 



