12 BACTERIOLOGICAL INTRODUCTION 



the passage from cocci to spirilla as an ascent in the 

 scale of plant life. 



The method of multiplication common to the entire 

 group of Schizophytes is that by fission, or cell 

 division. By outgrowths from the cell walls 

 advancing in two directions until they meet, the 

 original cell is divided into two exactly similar 

 daughter cells. The number of planes of division, 

 the parallelism of these planes, and the associa- 

 tion of the daughter cells resulting from the process 

 of division give rise to various sub-groups of the 

 three primary morphological divisions. 



Cocci. — These are spherical cells showing no 

 differentiation. The cells of different organisms of 

 this group show very considerable variation in 

 size, as may be seen in Figs. 1 and 2, the difference 

 in the cells ranging from "3 fx to 2-3 fi in diameter. 

 In the same micro-organism considerable difference in 

 the size of the individual cells may be observed. 



The principal sub-groups of the Coccaceae are — 



(a) Staphylococci. — This name is given to cocci 

 forming bunches or irregular groups of cells produced 

 by the successive division of the spherical organisms ; 

 the planes of division are probably uniaxial, but the 

 successive planes not parallel to one another. 



Cover-glass preparations of organisms of this 



