The cell in development and inheritance / by Edmund B. Wilson.

  • Edmund Beecher Wilson
Date:
1902, ©1900
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Licence: Public Domain Mark

Credit: The cell in development and inheritance / by Edmund B. Wilson. Source: Wellcome Collection.

Provider: This material has been provided by the Francis A. Countway Library of Medicine, through the Medical Heritage Library. The original may be consulted at the Francis A. Countway Library of Medicine, Harvard Medical School.

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    plasm. These investigators agreed that the amphiaster is formed under the influence of the centrosome, which by its division creates two new centres of attraction about which the astral systems arise, and which form the foci of the entire dividing system. In them are centred the fibrillae of the astral system, toward them the daughter- Fig. 28. — Metaphase and anaphases of mitosis in cells (spermatocytes) of tlie salamander. [Druner.] E. Metaphase. The continuous central spindle-fibres pass from pole to pole of the spindle. Outside them the thin layer of contractile mantle-fibres attached to the divided chromosomes, of which only two are shown. Centrosomes and asters. F. Transverse section through the mitotic figure showing the ring of chromosomes surrounding the central spindle, the cut fibres of the latter appearing as dots. G. Anaphase; divergence of the daughter-chromosomes, exposing the cen- tral spindle as the interzonal fibres; contractile fibres (principal cones of \'an Beneden) clearly shown. H. Later anaphase (dyaster of Flemming) ; the central spindle fully exposed to .view; mantle-fibres attached to the chromosomes. Immediately afterward the cell divides (see Fig. 29). chromosomes proceed, and within their respective spheres of influ- ence are formed the resulting daughter-cells. Both Van Beneden and Boveri fuUy recognized the importance of their discovery. We are justified, said Van Beneden, in regarding the attraction-sphere with its central corpuscle as forming a permanent organ, not only of the early blastomeres, but of all cells, and as constituting a cell-organ equal