. The cell in development and inheritance. Cells. THE MECHANISM OF MITOSIS 107 divide without any ampiiiaster whatever. In Infusoria mitosis seems to occur in the entire absence of asters, although the cells divide by constriction, and the analogy with Heidenhain's model entirely fails. vN^^ lK >-^^VA^. ^;^S^!/f/A 'â A' ' * ' \ U'M ^I'k. Fig. 52. â The later stages of mitosis in the egg of the sea-urchin Toxopnetistcs (A-D, X 1000; £-T, X 500). A. Metaphase; daughter-chromosomes drawing apart but still united at one end. B. Daugh- ter-chromosomes separating. C. Late anaphase; daughter
. The cell in development and inheritance. Cells. THE MECHANISM OF MITOSIS 107 divide without any ampiiiaster whatever. In Infusoria mitosis seems to occur in the entire absence of asters, although the cells divide by constriction, and the analogy with Heidenhain's model entirely fails. vN^^ lK >-^^VA^. ^;^S^!/f/A 'â A' ' * ' \ U'M ^I'k. Fig. 52. â The later stages of mitosis in the egg of the sea-urchin Toxopnetistcs (A-D, X 1000; £-T, X 500). A. Metaphase; daughter-chromosomes drawing apart but still united at one end. B. Daugh- ter-chromosomes separating. C. Late anaphase; daughter-chromosomes lying near the spindle- poles. D. Final anaphase; daughter chromosomes converted into vesicles. £. Immediately after division, the asters undivided; the spindle has disappeared. F. Resting 2-cell stage, the asters divided into tvvo in anticipation of the next division. In Figs. A and /? the centrosome consists of a mass of intensely staining granules, which in Cand F elongates at right angles to the In F the centrosome appears as a single or double granule, which in later stages gives rise to a pluricorpuscular centrum like that in A. The connection between D and F is not definitely determined. In EuglypJia, according to Schewiakoff (Fig. 39), division of the cell- body appears to take place quite independently of the mitotic figure. Again, a considerable number of cases are now known in which dur- ing the fertilization of the ^.g^ a large amphiaster is formed, with. 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 Wilson, Edmund B. (Edmund Beecher), 1856-1939. New York Macmillan
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectcells, bookyear1906
