Archive image from page 38 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agaruoft Year: 1920 THE ACHROMATIC FIGURE 23 single resting nucleus again, and there is no cell division. Thus nuclei are produced with three or four times the normal number of chromosomes. The mechanism by which the achromatic figure brings about the separation of the daughter chromosomes and subsequently cell division is still imperfectly understood. Two main theories are held : one that the ' fibres ' of the astral rays and spindle figure are actual
Archive image from page 38 of Cytology, with special reference to. Cytology, with special reference to the metazoan nucleus cytologywithspec00agaruoft Year: 1920 THE ACHROMATIC FIGURE 23 single resting nucleus again, and there is no cell division. Thus nuclei are produced with three or four times the normal number of chromosomes. The mechanism by which the achromatic figure brings about the separation of the daughter chromosomes and subsequently cell division is still imperfectly understood. Two main theories are held : one that the ' fibres ' of the astral rays and spindle figure are actually what they appear to be, namely, fibres or threads, and the other that they are merely lines of force or stress. The first and simplest form of the fibrillar theory supposed that the mantle fibres are contractile, comparable to muscle fibres, inserted at one end into the centrosome and at the other into the chromosomes. The centrosome being held in place by the astral rays, contraction of the mantle fibres pulls the chromosomes
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