THE B A C T K R I A L NUCLEUS 77 



nuclei, whicli he described as similar, spherical bodies disposed at each end 

 oi the cells which he studied ; a smooth culture of Saliiioiiclla typhi. Stoughton 

 described it as a single or double structure, not unlike a pair of primary 

 chromosomes, although broader. The organism which he studied, a plant 

 pathogen, formed the resting stage, a spherical body, by a rather unusual 

 method from the secondary nucleus (Chapter VI). By Stoughton 's technique, 

 a " vital " staining method, using carbol fuchsin, young cultures of this 

 bacterium stained uniformly, whereas the nuclear structures of older cultures 

 were clearly visible. This was almost certainly due to the masking effect of 



{After Stoughton. Reproduced from the Proceedings of the Royal Society.) 



Fig. 36 



THE SECONDARY NUCLEAR PHASE IN BACT. MALV ACE ARUM 

 Postulated alternative methods of division. 



the ribonucleic acid in the cell membrane of the young cultures (Chapter II). 



Bacteria in the secondary nuclear phase often produce forms which appear 

 to be in process of sexual conjugation. They are attached end to end, 

 usually at a shght angle, With the nuclear material concentrated at the point 

 of contact. From such forms Stoughton described the formation of a spherical 

 body resembhng the microcyst of myxobacteria. When the resting nticleus 

 is produced from similar forms in Bact. colt the process differs from that 

 found in Stoughton's bacterium, which he describes as extruding the spheri- 

 cal body from the point of conjugation, or from the side of a bacterium, 

 v^^hereas in Bact. coli the maturing or conjugating cells are transformed 

 directly into microcysts. 



The exact relationship between the primary and secondary phases of the 

 nucleus is not clear. The latter may be no more than the result of a reduced 



