1 53 GENERAL BIOLOGY OE MICRO-ORGANISMS 



tached after cell-division, forming groups of two, diplo-hacillus, 

 or many cells remain attached, to form long threads, strepto- 

 bacillus. Endospore formation occurs almost exclusively in 

 the bacteriaceae and the form of the spore-bearing cell differs 

 for different species and is .fairly constant for any one species. 



tQ3 



Pig. 67. — Position of spores; resultant forms (diagrammatic), a. Median 

 spores; b, intermediate spores; c, terminal spores; 20, 6, c, change in form of cells 

 due to the presence of the sp ore; 20, Clostridium; 2C, drum-stick form. {After Novy.) 



The spore, which is always single, may be located at the center of 

 the cell, median spore, or at the end, terminal spore, or at an 

 intermediate point. The spore-bearing cell may retain its normal 

 outline or it may be bulged by the spore. The cell containiiig 

 a median spore with bulging is carlled a Clostridium; one with 

 terminal spore with enlargement of the cell is spoken of as a drum- 

 stick or sometimes as a plectridium. 



Spiral Bacteria. — The screw-shaped bacteria, Spirillacece, have 

 been subdivided into four genera by Migula. The genus Spiro- 

 soma includes those spirals which are rigid and without motility. 

 Motile cells possessing one, two or three polar flagella are classed 

 in the genus Microspira; while those possessing: more than three 

 are put in the genus Spirillum. The genus Spirochaeta includes 

 the slender flexuous forms of spirals. 



SPIRILLACECE— Cells circular in cross-section but 

 curved to form a spiral or segment of a spiral. 



Spirosoma^ — Cells rigid, without flagella, motionless. 



Microspira — Cells rigid, motile, with i to 3 polar flagella. 



Spirillum — Cells rigid, motile, with polar tufts of flagella. 



Spirochaeta — Cells slender, flexuous, motile. 



