Blind Fish, the common name of several species of fish, of different genera, living in the subterranean waters of the United States and Cuba; but especially of the amblyopsis spelams (De Kay) of the Mammoth cave of Kentucky. In some of the lamprey-like fishes the eyes are mere specks, serving only for the simple perception of light, without the formation of an image; many catfishes (siluridae) have similar rudimentary eyes, entirely unfit for purposes of vision. In the Mammoth cave these fishes are nearly colorless, while the blind catfishes retain the general dark color of other members of the family. The common blind fish comes nearest to the cyprinodonts and the shore minnows. They are rather solitary, difficult to capture by the net from the acuteness of their senses of hearing and touch, and look like ghosts in the water; they are very active, taking their food both at the surface and near the bottom, and are able to capture a rapid-moving mudfish (melanura), having eyes, living in the same waters; the blind fish, with its sensitive tactile organs, is able to pursue and overtake the fish with eyes, but without a highly developed sense of touch, and which constantly encounters obstacles in the darkness.
They are viviparous, bringing forth their young in September and October; they vary in length from 2 to 4 1/2 inches. The head of amblyopsis is without scales as far as the pectoral fins, the rest of the body having small ones; the sides of the head are provided with numerous transverse and longitudinal ridges, each having 20 to 30 papillae, cup-shaped at the top and with a delicate tactile filament freely supplied with nerves from the 5th pair; there are also on the sides, from the pectoral to the tail, about 10 vertical ridges, with the papilla less well defined; the naked skin is of extreme delicacy. The optic lobes of the brain are as well developed as in ordinary fishes, and rudimentary eyes have been found under the skin by Prof. J. Wyraan and others. The eyes have the membranes, pigment, and lens, and, though imperfect, are constructed after the vertebrate type. They cannot form an image, as the integument and areolar tissue over them would prevent the transmission of any but very diffused light; no pupil or undoubted iris has been found. The organ of hearing is largely developed. The vent is in advance of the pectorals.
They are probably distributed in all the subterranean rivers flowing through the limestone region under the carboniferous rocks of the central United States; they have often been taken from wells. - Another colorless blind fish (typhlichthys subterraneus, Gi-rard), 1 1/2 to 2 inches long and having no ventral fins, has been found in the Mammoth cave, and in the central and southern portion of the subterranean region. In the genus cho-logaster (Ag.) are found all the family characters of the above two blind species, but it has eyes, a brownish color, and no papillary ridges on the head and body; yet it is a subterranean fish in some instances. In the Cuban blind fishes (genera luclfuga and stygicola), described by Prof. Poey, there are ciliary appendages on the head and body, well developed as organs of touch, but without the tactile barbels 0:1 the jaws usually found in the cod group, to which these fishes are nearly allied; the optic lobes are large, and the eyes exist, but so imbedded in the flesh of the head as to be useless; the body, cheeks, and opercular bones are covered with scales.
Though they resemble amblyopsis, it will be seen that they belong to a marine family, though now found in fresh water in caves, and are far removed from the latter. - From the facts here enumerated, and many others that may be found in the "American Naturalist," vol. vi., pp. 6-30, for January, 1872, Mr. F. W. Putnam expresses the opinion that these fishes have always been blind, and have not become so from living in darkness. As far as known, the young of blind fishes have no external eyes when born.