Karyokinesis and Cytokinesis in the Maturation, Fertilization and Cleavage of Crepidula and Other Gasteropoda

Karyokinesis and Cytokinesis in the Maturation, Fertilization and Cleavage of Crepidula and Other Gasteropoda

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1902 edition. Excerpt: ...cytoplasm. "I agree," he says, " with Hertwig that the centrosomes may develop out of the achromatic substance of the nucleus, but I see no ground to extend this statement to include all centrosomes.... There is good evidence to show, I think, that similar bodies may arise in the cytoplasm also, as shown by Reinke, Mead, Watase and myself." It is a notable fact, however, that in all these cases cited by Morgan the nuclear membrane has disappeared or is much shrunken and collapsed, showing that nuclear substance has escaped from it. This is true at least of the figures of Reinke, Mead and Morgan; Watase gives no figures of the egg of Macrobdella which he describes as containing "a series of thirteen asters, ranging from the miniature aster, with the microsome in its center, to the normal aster with a veritable centrosome." In the figures of Reinke, Mead and Morgan one is much struck by the fact that at the time when the asters appear in the cell the nuclear membrane is either entirely lacking or is much shrunken, showing that achromatic material has escaped into the cell. Of his own experiments Morgan says (p. 464): " The first effect (of the salt solution on the egg) is to cause a shrinkage of the nucleus; then after the return of the eggs to sea water the division of the nucleus and subsequently that of the egg takes place;... central bodies are present in the artificial astrosphaeres in almost all the stages." Again (p. 517) he says: "At the time when the nuclear wall disappears the astrosphaares throughout the egg, whether in contact with the chromosomes or not, become conspicuous and then fade away again as the chromosomes pass into the resting nuclei. There is some connection...show more

Product details

  • Paperback | 64 pages
  • 189 x 246 x 3mm | 132g
  • Rarebooksclub.com
  • United States
  • English
  • black & white illustrations
  • 1236839811
  • 9781236839817