114 MEIOSIS IN DIPLOIDS AND POLYPLOIDS 



so tliat their pairs of centromeres lie in the axis of the spindle they 

 divide ; the pairs of chromatids associated at the two centromeres 

 move to opposite poles. This means that in segments distal to a 

 chiasma pairs of chromatids pull apart. And it is evident that they 

 resist this separation, for bivalents which have the greatest length 

 of chromatids to pull apart lag behind the rest (Plate VI, and Figs. 



1 



5:2. 



^ 



% 



2.2 2.a 2.1 



amnios 



^, ^ \f 



5.1 



4-^ 





Fig. 35. — Left, metaphase, and right, anaphase, in Uvularia perfoliata . 

 with three lon-g and four short pairs. Internal spirals shown by- 

 some chromosomes. X 2200 (D., unpub.). 



28 and 35). Such chromosomes are seen at anaphase with their 

 two chromatids separated throughout their length. Conversely, 

 the simplest and quickest separation is found amongst bivalents 

 with terminal chiasmata. These merely break their terminal con- 

 nections and pass to the poles without any forced separation of their 

 paired chromatids. Indeed, sometimes they give no evidence, 

 except at their tips, of their double structure. The extremes 

 are therefore found with proximal localisation (Fig. 34, M, V, W) 



\ 



