. Cytology, with special reference to the metazoan nucleus. Cells. 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-. P Fig. 20. Meiosis in Ascaris megalocephala bivalens. (A-M, after Brauer, A ., 1893 ; N-P, after O. Hertwig, A ., 1890.) A, B, synizesis and syndesis ; C, D, E, formation of the definitive bivalents. In E the lef
. Cytology, with special reference to the metazoan nucleus. Cells. 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-. P Fig. 20. Meiosis in Ascaris megalocephala bivalens. (A-M, after Brauer, A ., 1893 ; N-P, after O. Hertwig, 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 divided 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. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Agar, W. E. (Wilfred Eade), 1882-1951. London, Macmillan and Co. , limited
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectcells, bookyear1920
