The Shipley Collection of Scientific Papers Volume 151

The Shipley Collection of Scientific Papers Volume 151

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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. 1911 edition. Excerpt: The nuclei of these sister-cells must undergo dissolution before such a plasmodium is formed, for I have never observed them in the growing ovum, which, moreover, is often bordered by cells in which the nucleus is but faintly discernible (fig. 2). The ovum continues its growth, in this manner at the expense of its sister cells, until at or about the time of liberation of the medusae the last are incorporated j and I have observed that one or two of their nuclei, at this stage, have in some cases persisted in the cytoplasm of the egg (figs. 3, 8, 9, 10). Finally the ova encroach upon the vacuolated substance of the manubrium until it is reduced to very small proportions (fig. 12), when they are set free. In the material examined it was clear that the vacuolated substance of the ova in the free medusae, in all cases, contained numerous zooxanthella?; but they were equally absent from the ova of the numerous unliberated medusa? that had been inspected. However, after a long search some half a dozen medusae were found which, I think, afforded conclusive evidence that zooxanthella? pass in numbers from the manubrium into the ovum, and that this invasion may commence at a period prior to the liberation of the medusa?. The ovum, until it has attained a considerable size, is sharply divided off from the vacuolated substance of the manubrium. Eventually a period is reached when its compact cytoplasm becomes continuous with the central mesh work (fig. 8). This stage could be commonly observed, and zooxanthellae be seen round the margin of the egg, but never in its compact substance. Sometimes the egg cytoplasm displayed small incipient vacuoles. The subsequent period, during which vacuolization of the cytoplasm of the ovum occurs, and more

Product details

  • Paperback | 110 pages
  • 188.98 x 246.13 x 5.84mm | 213.19g
  • United States
  • English
  • black & white illustrations
  • 123675493X
  • 9781236754936