Archive image from page 38 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar Year: 1920 B Fig. II. Early and late anaphase in the formation of the first polar body in Echinus esctiUfitus. (Bryce, , 1903.) towards the centrosome. This simple theory, however, is met by in- superable difficulties. One of these is that in telophase of most mitoses the chromosomes come very close indeed up to the centrosome, thus demanding an apparently impossible amount of contraction on the part of the fibres, while such a contraction
Archive image from page 38 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agar Year: 1920 B Fig. II. Early and late anaphase in the formation of the first polar body in Echinus esctiUfitus. (Bryce, , 1903.) towards the centrosome. This simple theory, however, is met by in- superable difficulties. One of these is that in telophase of most mitoses the chromosomes come very close indeed up to the centrosome, thus demanding an apparently impossible amount of contraction on the part of the fibres, while such a contraction would of necessity be accompanied by a relatively enormous thickening of the fibres, which, however, is not observed. Again, in the formation of the polar bodies during the matura- tion of the egg, the spindle fibres appear to exert a pushing rather than —or at any rate in addition to—a pulling action in bringing about their extrusion from the surface of the egg (Fig. ii). These and many other considerations have led to the further hypothesis that the separation of the daughter chromosomes is aided by an elongation of the fibres which connect the separating daughter chromosomes, together with those of the central spindle, which pushes the centrosomes apart. How-
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