Preliminary Report on the Collection of Mollusca and Brachiopoda Obtained in 1887-'88

Preliminary Report on the Collection of Mollusca and Brachiopoda Obtained in 1887-'88

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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. 1889 edition. Excerpt: forms with short siphons, like Ppromya and Lyonsiella, will evidently promote successful aeration of the blood by cutting off from the branchial chamber the water of the anal chamber, fouled more or less by the effcte products discharged into it. A certain amount of fibrous tissue must be developed to form this septum. It is clear that an economy of tissue would result from the transfer of retractorial functions to the septum and the obsolescence of the lateral retractile musculature. A further economy would result from the utilization of this large sheet of tissue for branchial purposes, and a-diminution of the tissue previously expended in the mass of the ctenidia. The habit of the larvae, so common among Pelecypods, of nestling for safety in the branchial folds, would lead directly to the utilization of the chamber as a refuge. 'But a close chamber such as we see in Verticordia would, from the less pure character of its contained sea-water, be less favorable than one into which the water could be more freely admitted by any means which would not imply an admixture of the foul water with that of the branchial chamber below. A system of orifices like those of Myoner a would accomplish this. A subsequent development of the muscular tissue of the septum, so that it could operate somewhat after the fashion of a pump and voluntarily frequently renew the water in the anal chamber, would obviously be beneficial. By the effect of stimulation the margins of the orifices thus subjected to repeated strong currents of fresh water would be likely to undergo a specialization of respiratory functions as oompared with the rest of the surface of the septum, which would result in something like the tubular gills of Oetoconcha, or the lamellae of...
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Product details

  • Paperback | 66 pages
  • 189 x 246 x 4mm | 136g
  • United States
  • English
  • black & white illustrations
  • 123695887X
  • 9781236958877