20 BACTERIOLOGICAL INTRODUCTION 



pole (Amphitricha) ; while a third variety (Lopho- 

 tricha) possesses at one extremity of the cell a 

 bundle or brush of flagella. Perhaps the com- 

 monest arrangement is that shown in Fig. 11, in 

 which flagella of varying number start from different 

 parts of the periphery and surround more or less 

 completely the cell body (Peritricha) ; these organs 

 of motion can in some of the larger varieties be 

 seen in the unstained condition, but the great 

 majority require for their demonstration special 

 staining methods. 



Multiplication by fission is the method of repro- 

 duction common to the entire group of Schizophytes, 

 but certain organisms are also capable of reproduc- 

 tion by spore formation. Spores are of two kinds — 

 arihrospores and endospores. In those organisms 

 which form arthrospores certain of the vegetative 

 cells — e.g., one member of a streptococcus chain 

 (Leuconostoc) — becomes modified and acquires 

 powers of resistance to harmful chemical and 

 physical agents which are not possessed by the 

 unchanged vegetative cells, while they at the same 

 time retain the power of reproduction when placed 

 under suitable conditions. It is a little doubtful 

 how far these modified cells can be looked upon as 

 true spores, and whether they should not be regarded 



