46 BACTERIOLOGY. 



other as single cells, the tendency then is for the seg- 

 mentation to be incomplete, the cells remaining together 

 in masses. The indentations upon these masses or 

 cubes, which indicate the point of incomplete fission, 

 give to these bundles of cells the appearance commonly 

 ascribed to them that of a bale of rags. As already 

 said, division in two opposite directions results in the 

 formation of a group of forms as tetrads. Division 

 irregularly in all directions results in the production 

 of clusters. The rod-shaped bacteria never divide 

 longitudinally. 



Spore-formation must be distinguished from vegeta- 

 tive reproduction. This is the process by which the 

 organisms are enabled to enter a stage in which they 

 resist deleterious influences to a much higher degree 

 than is possible for them in the growing or vegetative 

 condition. There are two kinds of spores which have 

 been described : 1. Endospores, which are strongly 

 refractile and glistening in appearance, oval or round 

 in shape, and developed within the interior of the cell. 

 They are characterized by the power of resisting to a 

 considerable extent the injurious influences of heat, 

 desiccation, and chemical disinfectants. 2. Arthro- 

 sporeSy or jointed spores, developed not within the cell 

 but as a sprout like separation of one of its extremi- 

 ties. These jointed bodies are believed by some to 

 have also greater resisting power to desiccation, etc., 

 than the ordinary cells, though less than the endo- 

 spores, and to serve the purpose of reproductive 

 elements. Recent researches into the formation of 

 arthrospores, however, have resulted in nothing defi- 

 nite, and the question of their existence even in bac- 

 teria still remains open. In describing the biological 



