. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Heteropygii. 128 BLIND VERTEBRATES AND THETR EYES. uniform in shape in different individuals or even the two sides of the same indi- vidual. It can be located and seen in cleared heads solely on account of the pig- ment which is always abundant over the distal face of the eye. It is located so far beneath the surface as to occasionally lie in contact with the brain case nearly opposite the posterior end of the olfactory lobe. It has thus been withdrawn much farther than in the other blind species. It is very much s
. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Heteropygii. 128 BLIND VERTEBRATES AND THETR EYES. uniform in shape in different individuals or even the two sides of the same indi- vidual. It can be located and seen in cleared heads solely on account of the pig- ment which is always abundant over the distal face of the eye. It is located so far beneath the surface as to occasionally lie in contact with the brain case nearly opposite the posterior end of the olfactory lobe. It has thus been withdrawn much farther than in the other blind species. It is very much smaller than the eye of either T. subterraneus or Amblyopsis. Its size is, however, quite variable, measuring 40, 49, 56, 64, 54 by 96, 56 by 120 /x in different instances, exclusive of choroid and sclera. brain. Fig. 44. (a) Cross-section of Part 'of Head of Troglichthys, 25 mm. long, showing Position and Proportions of Eye. (l>) Head of Troglichthys from above, showing Relative Positions of Tactile Organs and Eyes, (c) Part of Same Head, showing Eyes with their Peculiar Pigmentation and Distribution of Pigment Cells in Surrounding Tissues. The muscles of the eye were in no case normal. I have not found more than two rectus or more than one oblique muscle belonging to any one eye. They can best be made out from horizontal sections. In cross-sections it is very difficult to identify or follow them. The best-developed rectus was found in a specimen 35 mm. long. It is com- posed of a number of normal fibers forming a bundle 20 y. in thickness, and from its origin to its insertion it is 256 /a long. The remarkable peculiarity of this muscle is that 100 /a of this is a tendon 4 juin thickness (fig. 46 b,). The tendon spreads into a cone-shaped mass of fibers attached to the proximal face of the eye. Traces of two muscles were made out connected with the right eye of another Please note that these images are extracted from scanned page images that may have been
Size: 1546px × 1616px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookauthoreigenmanncarlh1863192, bookcentury1900, bookdecade1900
