MORPHOLOGY AND CLASSIFICATION 1 55 



The recognition of the cell nucleus has received special atten- 

 tion. Zettnow, more especially, has shown that the chromatin or 

 essential nuclear substance is present in 

 the bacterial cell as finer or larger granules, 

 sometimes distributed pretty generally 

 and sometimes collected together at one 

 or more places in the cell. The Roman- 

 owsky stain and its modifications have p,^.";,.^he format^n 

 been especially useful in differentiation of of spores. (,Afier Fischer 



1 ,• r .1 from Frost and McCampbell.) 



chromatm from cytoplasm. 



Special movements of the internal granules have been described 

 by Schaudinn as being associated with beginning cell division. 

 For the great majority of bacteria these have not been observed, 



^J«-^r 



{t i? ¥} 



\ 



Fig. 72. — Bacteria with spores. 



and according to our knowledge, the process of cell division is ex- 

 tremely simple. It consists of a progressive constriction and thin- 

 ning of the ce'U at the middle until two cells are produced. In 



S) (M) (^ (SS (crzia C 0® 0™ '0^ 



a c 







(5 ! 



0,1 o 



Pig. 73. — Germination of spores, a, Direct conversion of a spore into a bacillus 

 without the shedding of a spore-wall (B. leptosporus) ; b, polar germination of B. 

 anthracis, c, equatorial germination of B. subtilis; d, same of B. megatherium; e, 

 same with "horse-shoe" presentation. (Afler Novy.) 



some forms the division is completed by a sudden snapping move- 

 ment. , 



