92 MEIOSIS IN DIPLOIDS AND POLYPLOIDS 



differentially condensed. Thus in Fritillaria (Darlington, 1935 a) 

 after pairing the chromosomes are more deeply staining m the 

 neighbourhood of the centromere and pairing is variable in all 

 species and incomplete in most. The defect of pairing is always 



4 <i 4r ^ 



Fig. 23. — The chromosomes of Bellevalia romana. Top, at mitotic 

 metaphase, 2m = 8 ; four types. A, B, C, D. Middle, the four 

 pairs of chromosomes at pachytene, drawn separately. Bottom, 

 the four pairs at metaphase, each with two chiasmata except the 

 rightmost, which has three. X 2,000 (Dark, 1934). 



in regions remote from the centromere. Particularly frequent is a 

 failure of pairing close to the nucleolus in those chromosomes which 

 are attached to nucleoli. It seems likely that such chromosomes 

 would be hampered and delayed in coming together by having to pull 

 their nucleoli after them, when the nucleoli have not already fused. 



