SPIRALISATION 



Table 2 

 The Time Taken by Division of the Nucleus 



31 



3. THE STRUCTURE OF CHROMOSOMES 



(i) Spiral Structure. At metaphase all chromosomes consist of 

 two cylindrical rods, the chromatids, which are normally of even 

 diameter. This diameter is a racial characteristic constant in most 



Table 3 



Estimated Total Lengths of Chromosomes in Complement 



(in Microns) 



* This length is halved to correspond with the haploid complement measured 

 at meiosis. 



t Belling states (1931 a) that leptotene threads in Lilium are six and a half 

 times as long as at metaphase. This seems to disagree with the results 

 recorded here. 



