II 



MEIOSIS IN ASCARIS 



51 



By the later stage shown in Fig. 20, C, synizesis has completely dis- 

 appeared, and all the chromatin is in the form of a long, doubly split 

 thread (only one split is visible in the plane of the figure). As there are 

 really two bivalent chromosomes present, these must be joined tempor- 



FiG. 20. 



end view, and therefore its quadruple constitution is revealed. F, metaphase I. ; G, H, anaphase I. ; I, 

 preparation for second division ; J, metaphase II. ; K, anaphase II. ; L-M and N-P, condensation of the 

 definitive bivalents in nuclei in which the four constituents of each are well separated. 



arily end to end to form an " unsegmented spireme " as described on p. 9. 

 Later (D) this dissociates into its two components. Each of these is a 

 bivalent chromosome, longitudinally di\dded into four owing to the fact 

 that each constituent univalent is, as described above, itself longitudinally 

 divided. The quadruple nature of each bivalent chromosome is well 



