46 MITOSIS : THE CONSTANCY OF THE CHROMOSOMES 



chromosomes. They correspond in number with the chromosomes 

 in diploid and polyploid tissues of the same plant (Manton, 1935). 

 According to Heitz (1929, 1932, 1935) this property is sometimes 

 related with excessive prophase and telophase condensation of the 

 affected parts, which, however, unlike the chromocentre, does not 

 give the Feulgen reaction {cf. Ch. VIII). 



Manton (1935) finds that small nuclei showing chromocentres 

 differ from large nuclei of the ordinary type described in several 

 correlated respects. The telophase nucleus is very much larger 

 in relation to the metaphase chromosomes, as shown by root-tips 

 (Table 4). 



Table 4 

 Relative Sizes of "Solid " and ** Vesicular " Nuclei 



Allitim ursinum . 

 Biscutella Icevigata 



Resting 

 nuclei 



900 C./x 

 I20C./X 



Nucleoli 



7OC./X 



I4C.)Lt 



Metaphase 

 chromosomes 



140 C./x 

 4C./X 



The telophase chromosomes consequently lie widely separated in 

 the nuclear sap, as prophase chromosomes always do. They are 

 therefore capable of movement and their visible parts, the chromo- 

 centres, move towards the surface of the nucleus at the end of 

 telophase. Owing to the greater fluidity of the nucleus it changes 

 its shape rapidly and the nucleoli are always coalesced into one 

 body at this stage. For the same reason the nucleoli can be dis- 

 placed by centrifuging in a way that is not possible in the compact 

 nuclei formed in the same way as in Kuwada's experiment. These 

 differences are undoubtedly significant and it is now necessary to 

 find out how far they are determined by the size of the nucleus, 

 which varies in different tissues, and how far by the size of the meta- 

 phase chromosomes. 



Conclusion. We now see that the resting nucleus has a structure 

 that may be identified both by comparison and experiment. The 

 chromosomes do not appear like ghosts to flit for a transient moment 



