THE BACTERIAL NUCLEUS 79 



amorphous material, nuclear or otherwise, lying within an elongated cell. 

 That this is not so, however, is attested by the retention of the rod form by 

 that portion of the nucleus which is included in the spore of Clostridium tctani, 

 during the initial stages of the process of maturation. 



Bacterial cells in this nuclear phase arc still capable of vegetative reproduc- 

 tion. Gram-negative, intestinal bacteria may adopt the condition in cultures 

 not more than a day old, although they do not invariably do so, as it is 

 alternative to the secondary nuclear phase, which is often found in such 

 circumstances. 



The entire secondary mycelium of streptomyces, from which the spore- 

 bearing hyphae arise, contains rod-shaped nuclei, and they are frequently 

 found in the early stages of sporulation in Bacillus and Clostridium, although 

 it is uncertain whether, in this case, vegetative reproduction may still be in 

 progress. 



Although rod-shaped nuclei are usually found to be associated with sexual 

 conditions in bacteria, their significance is not always the same, as some forms 

 may precede and others succeed conjugation. In the case of the Bacteriacece , 

 the secondary nucleus or the rod-shaped form, either of which may be found 

 in the later, vegetative stages of the culture, are both capable of giving rise 

 directly to the mature, resting nucleus by an apparendy sexual or autogamous 

 process. The rod is often obviously granular, and it is possible that the 

 granules may represent the elementary chromosomes in an alternative arrange- 

 ment, although diey are too small for their behaviour at cell division to be 

 observed. 



In streptomyces and spore-bearing bacilh the rods appear sohd and con- 

 sistent, giving no clue as to their composition. A very early study by Schaudinn 

 (1902, 1903) described the rod, in the process of spore formation. Schaudinn 

 considered that it was formed by a condensation of granular material dis- 

 tributed throughout the cytoplasm. This observation has been regarded as 

 supporting the theory that the bacterial nucleus normally exists in a diffuse 

 form, and the more modern views of its nature have caused doubt to be 

 shed upon the vahdity of Schaudinn's observations. In fact, however, there 

 is reason to believe that, in the process of transformation from the primary 

 ^condition of the nucleus, the chromatinic material may be dispersed in the 



