. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Evolution. THE EYES OF AMBLYOPSIS. 135 Wyman was mistaken in his identification of Nos. 2 and 4, and part of 3. Of tliis species I liave Iiad an unlimited supply of fresh material from the Shawnee Caves in Lawrence County, Indiana. I shall first give the histology of the eyes of fishes from 25 mm. long to their maximum size, 135 mm. The details of the development of the eye will follow. In well-fed adult specimens of Amhlyopsis there is no external indication of an eye. In poor individuals the large amount of fat s
. Cave vertebrates of America; a study in degenerative evolution. Cave animals; Evolution. THE EYES OF AMBLYOPSIS. 135 Wyman was mistaken in his identification of Nos. 2 and 4, and part of 3. Of tliis species I liave Iiad an unlimited supply of fresh material from the Shawnee Caves in Lawrence County, Indiana. I shall first give the histology of the eyes of fishes from 25 mm. long to their maximum size, 135 mm. The details of the development of the eye will follow. In well-fed adult specimens of Amhlyopsis there is no external indication of an eye. In poor individuals the large amount of fat surrounding the eye and collected in a ball-shaped mass becomes apparent through the translucent skin. In young specimens, before they have reached a length of 50 mm., the eyes are perfectly evident from the surface. By this I do not mean that they are conspicuous, for the minute eyes would not be conspicuous were they situated just beneath the skin. The skin is not modified in the region over the eyes, but has the same structure it possesses in the neighboring regions. This condition is in strong contrast to the conditions described for Chologaster papilliferus. The position of the eye can be determined from the surface in older individuals by certain tactile ridges, being. Fig. 40. (a) Section of Right Half of Head of Chohgasler, through Eye. (6) SeclionofRightHalf of Head of/I mWyopjis, through Eye. between a long longitudinal ridge (supraorbital) situated caudad of the posterior nares and two Vertical (suborbital) ridges. They can also be approximately located by the mucous canals, being situated above the middle of the suborbital canal forward from the fork of the suborbital and rostral canals. The exact location in relation to these ridges differs, however, to some extent in different specimens. The skull is surprisingly little modified, there being deep orbital notches, large enough to accommodate a large eye. The maintenance of this skull structure long after the eye has
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