232 A HISTORY OF FISHES 



In some parts of the world the abundance of food in caves, 

 wells, and other subterranean waters, coupled with the absence 

 of larger predaceous fishes, has led certain species belonging to 

 very different families to take up their existence in these regions 

 of more or less total darkness. These include two or three 

 Cyprinid fishes allied to the Barbels (Barbus), found in wells 

 and subterranean lakes in Africa; Cat-fishes of four different 

 tribes inhabiting caves and wells in Africa, the United States, 

 Trinidad, and Brazil; the famous cave-dwelling Cyprinodonts 

 of the United States; and the bhnd Brotulids of Cuba. As 

 might be expected, where the cave-dwelling habit has been 

 adopted comparatively recently the fishes are not especially 

 modified, but in nearly every case the absence of light has led 

 to the reduction or loss of the organs of vision, and a complete 

 loss of pigment, sometimes accompanied by the special develop- 

 ment of certain sense organs to compensate for the loss of sight 

 {cf. p. 1 89) . In the Cyprinid species the scales are either very thin 

 and flabby or are absent altogether, and the sensory organs of 

 the skin are highly developed. 



The most interesting of the blind forms are the KiUifishes or 

 Cyprinodonts of the family Amblyopsidae, all small fishes under 

 four or five inches in length, and all occurring in the United 

 States of America. Eight species are included in this family, 

 some of them cave-dwellers, some living in the open, but all 

 agree in possessing degenerate eyes, and in having the vent 

 placed remarkably far forward in the region of the throat. One 

 {Chologaster cornutus) inhabits open streams and ditches, being 

 particularly abundant in the ditches of the rice-fields of South 

 Carolina. This fish is normally coloured, and the body is striped 

 with longitudinal bands of black. Another very closely related 

 form (C. agassizii) found in the subterranean streams of Tennessee 

 and Kentucky is coloured pale brown and the sides are un- 

 striped. Both these fishes have small but quite functional eyes, 

 and no special development of sense organs is apparent. A 

 third species (C. papilliferus), likewise related to the above, has 

 the black stripes on the body, small eyes, and, in addition, ridges 

 of sense organs developed on the head and body. The remain- 

 ing members of the family {Amblyopsis, Typhlichthys), including 

 the famous Kentucky Blind-fish {Amblyopsis spelaeus) first de- 

 scribed in 1842 (Fig. 8ib), all live permanently in the under- 

 ground waters of limestone caves. They are translucent and 

 colourless, the eyes are variously degenerated and generally 

 represented in the adults by mere vestiges hidden under the 



