Contributions to the Natural History of the United States of America; PT. 1. Acalephs in General. PT. 2. Ctenophorae. 1860

Contributions to the Natural History of the United States of America; PT. 1. Acalephs in General. PT. 2. Ctenophorae. 1860

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This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1860 edition. Excerpt: ...strictly homologous to the ambulacral tubes of the Ctenophorae, as they are also to those of the Discophorae proper. Their number generally coincides in the Ctenophorae and higher Discophoras, though there are only four in the Siphonophoras and most Hydroids proper. Sometimes they are, however, very numerous in the latter, as we frequently find an indefinite repetition of identical parts in the lowest representatives of almost every type. We have already seen that the peripheric branches of the chymiferous system do not open outward, as Ehrenberg and Milne-Edwards supposed; but there are, unquestionably, openings in its axial prolongation, in Ctenophoras, which have generally been considered as anal apertures. Milne-Edwards has accurately described them in LeSueuria, and they have been observed by all later investigators. Lesson alone has mistaken accidental openings in the circumscribed area for structural features. There can be no doubt of his mistake, since he describes those holes in the Beroids proper as surrounded by fringes, while the position of the natural openings of the abactinal pole of the Ctenophorae is outside of the area, as well as outside of the fringes which encircle it. In all the Ctenophorae which I have examined, I have invariably found two such openings, in an excentric position, one on one side and the other on the other side of the antero-posterior diameter, and obliquely opposite to one another. Gegenbaur states that there is only one such opening in the species which he has examined with reference to this point. It is much to be regretted that he should not have mentioned its position; for if the opening which he saw was excentric, as I have always found these openings to be, I should infer, that while he saw one more

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  • Paperback | 166 pages
  • 189 x 246 x 9mm | 308g
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236648846
  • 9781236648846