BACTERIA. 45 



pole and the young cell emerges so that its long axis is in the same direc- 

 tion as the long axis of the spore. In another type the spore ruptures 

 equatorially and the young cell emerges with its long axis at right angles 

 to the long axis of the spore. In still other types the spore swells and 

 the young cell absorbs the wall of the spore. 



In the lower or true bacteria only a single spore is formed in a cell. 

 In the case of the higher bacteria, however, a number of spores may be 

 formed at the distal end of the filament. These are spoken of as gonidia, 

 and possess properties similar to those of the endospores. 



OB m <S> c= d=> Q C O 0- Qsn 



a c 



1 



FIG. 25. -Spore germination, a, direct conversion of a spore into a bacillus without 

 the shedding of a spore-wall (B. lepiosporus} ; b, polar germination of Bact. anthracis; c, 

 equatorial germination of B. suUilis; d } same of B. megaterium; e, same with "horse- 

 shoe" presentation. (After Novy.) 



In some cultures of bacteria, as for example in the micrococci, certain 

 cells seem to be larger and different from the other cells. In a strepto- 

 coccus filament, certain cells suggest to the observer the joint spores of 

 the algae and have therefore been spoken of as arthrospores or joint spores. 

 There is, however, no evidence of an experimental nature, which warrants 

 the belief that these cells are in reality spores, and it must be said that 

 at the present time the presence of arthrospores among the bacteria is 

 purely hypothetical. 



CELL GROUPING. 



Bacteria rarely occur singly but usually in groups. These cell 

 aggregates are frequently very constant and quite characteristic of the 

 organism possessing them. They are of sufficient definiteness and 

 constancy to be used by the systematists in chacterizing large groups. 



CELL AGGREGATES AMONG THE MICROCOCCI. The grouping of 

 micrococci depends upon the plane of division and also upon the cohe- 

 sion of the cells. Since it is quite as economical for the rnicrococcus to 



