The cell in development and inheritance . no direct relation to the spindle-formation (Fig. 133). Again Juel 1 Cf. pp. 52, 214. 3o6 SOME PROBLEMS OF CELL-ORGANIZATION (97) finds that an isolated chromosome, accidentally separated fromthe equatorial plate (pollen-mother-cells of Hcmerocallis), may giverise to a small vesicular nucleus which may subsequently divide bymitosis, though it is quite out of relation to the spindle-poles of thepreceding mitosis (Fig. 149). Strong evidence of the same characteras the last is given by the facts in the- heliozoon Acanthocystis, asshown by Schaudinn (96, 3
The cell in development and inheritance . no direct relation to the spindle-formation (Fig. 133). Again Juel 1 Cf. pp. 52, 214. 3o6 SOME PROBLEMS OF CELL-ORGANIZATION (97) finds that an isolated chromosome, accidentally separated fromthe equatorial plate (pollen-mother-cells of Hcmerocallis), may giverise to a small vesicular nucleus which may subsequently divide bymitosis, though it is quite out of relation to the spindle-poles of thepreceding mitosis (Fig. 149). Strong evidence of the same characteras the last is given by the facts in the- heliozoon Acanthocystis, asshown by Schaudinn (96, 3), the ordinary vegetative cells containinga persistent extra-nuclear centrosome, while in the bud-formation ofthe swarm-spores a centrosome is formed de novo, without relation tothat of the mother-cell, inside the nucleus of the bud (Fig. 41). The strongest case in favour of the independent origin of centro-somes is, however, given by the observations of Mead on ChcEtopteriis(98) and the remarkable experiments of R. Hertwig (95, 96) and. Fig. 149. — Abnormal mitosis in pollen-mother-cells of- Hemerocallis, showing formation ofsmall nucleus from one or l-wo stray chromosomes and its subsequent division. Quel.] Morgan (96, i ; 99, i) on the eggs of echinoderms and other eggs of CJicBtopterus are taken from the body-cavity and placedin sea-water, a multitude of small asters appear in the cytoplasm, twoof which are believed to persist as those of the polar spindle, whilethe others degenerate (Fig. 150). Mead is therefore convincedthat the polar centrosomes arise in this case separately and de novo}R. Hertwig showed that when unfertilized eggs of sea-urchins{Strongylocentrotris, EcJdnus) are kept for some time in sea-water ortreated with dilute solutions of strychnine the nuclei undergo some of 1 A number of other authors {^ Griffin, Thalassema, Coe, Cerebratulus) have likewisefound the first polar asters -widely separated at their first appearance. On the other
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