. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Evolution. 144 BLIND VERTEBRATES AND THEIR EYES. not be determined with certainty. The relative development of the lens is not dependent on age. The lens described by Wyman was undoubtedly one of the scleral cartilages, for these cartilages are frequently nodular in this species and one usually lies in front of the eye. The supposition of Wyman that one of the scleral cartilages is the lens need not be criticised too severely. The structures descril^ed above as the lens are con- sidered such, more because they coul
. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Evolution. 144 BLIND VERTEBRATES AND THEIR EYES. not be determined with certainty. The relative development of the lens is not dependent on age. The lens described by Wyman was undoubtedly one of the scleral cartilages, for these cartilages are frequently nodular in this species and one usually lies in front of the eye. The supposition of Wyman that one of the scleral cartilages is the lens need not be criticised too severely. The structures descril^ed above as the lens are con- sidered such, more because they could not be identified as anything else, and be- cause nothing else that could with certaintv be considered a lens could be found. Fig. s5. M Two Successive Sections through Right Eye of very Old 130 mm. long, showing a Lenslike Body. (J) Outline Section of Left Eye of Individual 108 mm. long, showing highly developed Lenslike Body. aside from these structures, rather than on any direct evidence. The development of the eye would indeed lead one to suppose that the lens is actually placed entirely outside the optic cup, and in that case none of the structures here described can be the lens. With as much varication as is found in all the structures it is not improb- able that the lens may, in some indi\nduals, be found within the optic cup, and in others outside of it. The progressive ontogenetic degeneration of the eye after maturity will be given in the section dealing with its ontogenetic history. Measurements of the Eve of Amhlyn psis in fj. Length of Fish. Diameter of Eye, .\xial. Diameter of Eye, Vertical. Pigment Layer Nuclear Layer. (^.ranular Layer. (langlionic Layer. Posterior. .\nterior. mm. 2S 60 75 85 108 108 160 â 44 9" 56 204 200 ? 160 108 108 142 108 142 84 28 ^6 28 56 16 52 ? 20 12 4 4 8 4 16 16 12 12 12 10 24 12 24 24 28 12 22 5 4 13 X 120 Averages .39 8? 13 24 12. Please note that these images are extracted from scanned page images that may have
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