Cave Vertebrates of America; A Study in Degenerative Evolution

Cave Vertebrates of America; A Study in Degenerative Evolution

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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. 1909 edition. Excerpt: ...is developed in earlier stages and disappears I have not been able to determine. In the specimens 40 mm. and less in length the pigment layer consists of a series of cells, but little separated from the underlying outer nucleated layer. The separation between the layers is greatest near the exit of the nerve and at the iris. In older individuals a considerable space is formed between the pigment layer and the outer nucleated layer on the dorsal and proximal parts of the eye, but since in all of the cases under consideration a good share of this space is attributable to reagents, a more detailed description is useless. However, in these regions delicate protoplasmic processes extend inward to the nucleated layer. The nuclei of the pigmented layer stain much more faintly than those of the rest of the retina with Biondi-Ehrlich, but just as deeply as the others with hsemalum. The cells of the pigment layer are in one series, but occasionally a cell is found below the level of the rest. A few cells very elongate in section may be mentioned here. They were found (fig. 41a) on the inner face of the pigment layer. These are important in the interpretation of the structure of the eye of Troglichthys roses, where they are also found. Their origin and significance are not known.1 Fro. 41. (a) Sagittal Section through Right Eye of Typhlichthys subtcrraneus, 25 mm. long. lb) Mtillerian Nuclei (?) from Retina of Individual 25 mm. long. (c) Horizontal Section of Eye of Individual 40 mm. long. Rods and Cones with their Nuclei.--While the outer nuclear layer is very well developed indeed, the rods and cones are not definite. In the most highly developed eye there is a distinct outer limiting membrane. Without this are filmy processes continuous with those from...show more

Product details

  • Paperback | 118 pages
  • 189 x 246 x 6mm | 227g
  • Rarebooksclub.com
  • Miami Fl, United States
  • English
  • black & white illustrations
  • 1236506480
  • 9781236506481