Archive image from page 66 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agaruoft Year: 1920 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- FlG. 20. Meiosis in A scaris megalocephala bivalens. (A-M, after Brauer, , 1S93 ; N-P, after O. Hert\vig, A., 1890
Archive image from page 66 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agaruoft Year: 1920 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- FlG. 20. Meiosis in A scaris megalocephala bivalens. (A-M, after Brauer, , 1S93 ; N-P, after O. Hert\vig, A., 1890.) A, B, synizesis and syndesis ; C, D, E, formation of the definitive bivalents. In E the left-hand bivalent is seen in side view and therefore only two of the constituents are visible; the right-hand bivalent is seen in 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 dixdded 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
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