. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Evolution. Fio. 4S. (0 and b) Two Cross-sections of Eye of Specimen preserved in Alcohol. 38 mm. long. Sec- tions show Variable Extent of Pigment, Choroidal (cA.) Pigment, and Scleral Cartilages. Extent of latter represented by dotted lines in figure a. eye in size. As a consequence individual cartilages either extend beyond the eye or are bent at acute angles in their endeavor to apply themselves to the shrunken eye (fig. 46 a, ). These cartilages were mistaken for the suborbital bones by Kohl. There is absol
. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Evolution. Fio. 4S. (0 and b) Two Cross-sections of Eye of Specimen preserved in Alcohol. 38 mm. long. Sec- tions show Variable Extent of Pigment, Choroidal (cA.) Pigment, and Scleral Cartilages. Extent of latter represented by dotted lines in figure a. eye in size. As a consequence individual cartilages either extend beyond the eye or are bent at acute angles in their endeavor to apply themselves to the shrunken eye (fig. 46 a, ). These cartilages were mistaken for the suborbital bones by Kohl. There is absolutely no ground for this supposition. The suborbitals are present (fig. 44 a, stibo.) and widely separated from these cartilages. Further, the eye muscles are attached to the cartilages and to similar ones in AmUyopsis. The presence of these large cartilages is the more remarkable when we con- sider that none are found in Typhlichthys subterraneus, and in the species of Chologaster, which in other respects resemble Typhlichthys in all but the develop- ment of the eye and the color. It is quite evident that Troglichthys and Typh- lichthys are not derived from a common ancestor (except, of course, remotely). Their present superficial resemblances are the result of converging development under similar environments. A species similar to Chologaster agassizii gave rise to Typhlichthys subterraneus. What the ancestry is of AmUyopsis and of Tro- glichthys is not known. The cartilages are bound together by an abundant fibrous connective tissue containing a few corpuscles. (These I have found nowhere as abundantly as represented by Kohl.). Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Eigenmann, Carl H. , 1863-1927. Washington, D. C. , Carnegie Institution of Washington
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