2 . . . BACTERIA 



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



and grow in chains. 



(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. 



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

 bale-like packages, or blocks of eight are formed. At 

 least one variety (Sarcina agilis) is motile, having fla- 

 gella. Plates of cocci, one thick in the plane, are called 

 " merismopedia"" 



II. BACTERIACE^:. 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, peritrichic in arrangement. 



(c) Pseudomonas. Have endospores very rarely. Flagella 

 only at ends. 



in. SPIRILLACE^:. -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. 



