CHAPTER IV. 



CELL GROUPLNGS. 



It has been stated that bacteria reproduce by trans- 

 verse division, that is, division across the long axis. Fol- 

 lowing repeated divisions the new cells may or may not 

 remain attached. In the latter case the bacteria occur as 

 separate isolated individuals. In the former, arrangements 

 characteristic of the particular organism almost invariably 

 result. These arrangements are best described as cell 

 groiqnngs or growth forms. 



Fig. 43.— Streptospirillum grouping. Fig. 44.— Diplobacillus grouping. 



In the case of spiral forms it is obvious that there is only 

 one possible grouping, that is, in chains of tw^o or more 

 individuals adherent end to end. A chain of two spirilla 

 might be called a diplosinrillum (oiTiAoz, diplos — double) ; of 

 three or more, a straptospirrillum {ozpzuzoz, streptos — 

 necklace, chain) (Fig. 43). These terms are rarely used, 

 since spirilla do not ordinarily remain attached. Likewise 

 the bacillus can grow only in chains of two or more, and the 

 terms diplobacillus (Fig. 44), bacilli in groups of two, and 

 streptobaciUus (Fig. 45), bacilli in chains are frequently used. 

 (40) 



