T H F B A C T i: R I A L N U f ! L I- U S 75 



A pair ot cliromosonics or chromosoinc complexes take part in the niciotic, 

 reduction process wliich follows nuclear fusion in M. tuberculosis. The cells 

 ot the vegetative bacillus contain small, spherical nuclei, and the zygote a 

 large, vesicular one. It must be concluded that the difference between the 



@ 



(Modified after I'oclion, et al.) 



Fig. 34 



NUCLEAR DIVISION IN AZOTOBACTER 



The vesicular nucleus reforms as four large chromosome complexes, two of which pass 

 into each half of the dividing cell. Here they divide and reconstitute the vesicular nucleus 

 in each daughter cell. 



condition in those bacteria which appear to possess a spherical, vegetative 

 nucleus and those in which the chromosomal condition is obvious and semi- 

 permanent, lies in the power of the former to resume the resting form of the 

 nucleus between each cell division, a state of affairs which is normal in most 

 organisms. 



H: THE SECONDARY NUCLEUS 



(13, 41, 42, 4.S, 46, 4«) 



The secondary type of bacterial nucleus was first described in an interesting 

 paper by Stoughton (1929), and later, independently by Piekarski (1937) 

 who contrasted it with the primary form, but it has been little studied. This 

 is in part explained by the fact that Stoughton tailed to demonstrate the 

 primary nucleus by the technique which he employed, so that his findings 

 were not correlated with the later observations upon this phase of the nuclear 

 cycle, whereas Piekarski, although successful in demonstrating both types 

 of nucleus by the Feulgen reaction and by the acid-Giemsa technique as well 

 as by ultra-violet light, failed to resolve them properly, and figured them 

 ( as spherical bodies, which cast doubt upon the value of his morphological 



