THE MITOTIC CYCLE 



nucleic acids were increased in amount (Figure 4). Schultz et alii^^^ 

 found that genetical rearrangements of heterochromatin in the X- 

 chromosome were reflected in differences in the absorption spectra of 

 the nucleoli. These observations have assumed a prominent part in the 



:^ 



V 



?^1 y . Right arm of '^, x chromosome 



m 



^ ■■/ '' /^ chromosome ■ ,/*.. ■ * 



m: 



I 



j'^-h^ 







^^' 



ss Chromosome jjj, 

 Z. If, '^ 



.# 





'A 



» ^ 



Chromosomes from oyarian tissue 



(same enlargement) 



Chromocentre ^^)^^^ 



^ 



<S^, 



It 



55,>-. 



'^. 



%.. 







*■•#. 



^^it:3)0% 



Leff arm of cej 

 chromosome M 4i?^' 



^' 



^ 



Leif arm of 

 chromosome ff 



^ 



Righf arm of 

 chromosome n 





'<^-: 







Figure 15 Chromosomes of salivary gland nucleus oi Drosophila melanogaster together 

 with those of oogonial nucleus to same scale. In the salivary nucleus the synopsis of 

 homologous elements is everywhere complete except for the proximal part of the 2nd 

 chromosome. The 4th chromosomes are partly covered by the chromocentral mass 

 common to all the chromosomes, here shown in two portions. From 'Painter^^^* 

 {By courtesy, J. Hered.). 



46 



