158 



THE CYTOLOGY AND LIFE-HISTORY OF 



More recently Lederberg and his collaborators have produced evidence 

 that vegetative diploid strains of Bact. coli may exist. The cells are longer than 

 the haploids and have a larger number of similar nuclear elements. 



i%f^ 



^- •*-'*a: 



\cs^ 



»^ ^ 



'%% 



(Keproducfd from Cold SpnnK Ha/hor Symposia). 



Fig. 68 

 DIPLOID OR POLYPLOID FORMS OF NUCLEUS 



(1) Cells of Bacterium coli known to be genetically diploid. {By permission of Dr. J. 

 Lederberg) . 



(2) Presumed diploid or polyploid nuclei in post-fusion stages of a .sporing bacillus. 



(3) Secondary mycelium of Streptomyces. 



In the sections deahng with the nature of the chromosome it has already 

 been argued that the behaviour of the nuclear material at cell division indicates 

 that all the nuclear units contained in the vegetative cell must be of equal 

 value, that is, the cell is haploid but multinucleate. In sexual conjugation the 

 two partners appear to be similar in status, and in bacteria of this type reduction 



