THE PENNSYLVANIA BLIND FISH. 31 



pout or horned pout, and of about the same size (ten inches in 

 length). It was taken in the Conestoga river in Lancaster Co., 

 Penn., where it is "occasionally caught by fishermen and is sup- 

 posed to issue from a subterranean stream said to traverse the 

 limestone in that part of Lancaster Co.. and discharge into the 

 Conestoga." We quote the following from Prof. Cope's remarks 

 on the fish: *- 



"Two specimens of this fish present an interesting condition of 

 the rudimental eyes. On the left side of both a small perforation 

 exists in the corium, which is closed by the epidermis, representing 

 a rudimental cornea ; on the other the corium is complete. Here 

 the eyeball exists as a very small cartilaginous sphere with thick 

 walls, concealed by the muscles and fibrous tissue attached, and 

 filled by a minute nucleus of pigment. On the other the sphere is 

 larger and thinner walled, the thinnest portion adherent to the 

 corneal spot above mentioned ; there is a lining of pigment. It 

 is scarcely collapsed in one, in the other so closely as to give a 

 tripodal section. Here we have an interesting transitional condi- 

 tion in one and the same animal, with regard to a peculiarity which 

 has at the same time physiological and systematic significance, 

 and is one of the comparatively few cases where the physiological 

 appropriateness of a generic modification can be demonstrated. It 

 is therefore not subject to the difficulty under which the advocates 

 of natural selection labor, when necessitated to explain a structure 

 as being a step in the advance towards, or in the recession from, 

 liny unknown modification needful to the existence of the species. 

 In the present case observation on the species in a state of nature 

 may furnish interesting results. In no specimen has a trace of 

 anything representing the lens been found." 



When we remember that the lens of the eye in Amblyopsis has 

 been found, even though the eye is less developed in all its parts 

 than in Gronias, it is probable that a careful microscopical exami- 

 nation would show its existence in this genus also. 



It is interesting to note that this fish is black above (lighter on 

 the sides and white below), notwithstanding its supposed subter- 

 ranean habits, and that all the other members of the family having 

 rudimentary or covered eyes are also dark colored, while the blind 

 fishes of the Mammoth Cave and of the caves in Cuba are nearly 

 colorless. This want of color in the latter fishes has been consid- 

 ered as due to their subterranean life. If this be the cause, why 

 should the blind cat fishes retain the colors characteristic of the 

 other members of the family living in open waters ? 



* Proceedings of the Academy of Natural Sciences of Philadelphia for 1864, p. 231. 



