BARDWICKE'S SCI EN CE-GOSSIP. 



55 



rapidlj^ The habits of the AmLbjopsis are solitary, 

 and, notwithstanding its blindness, it is extremely 

 ditficult to be caught. At the slightest motion of 

 the water it darts rapidly away, and then suddenly 

 stops. They come to the surface to feed, where 

 their tactile organs, being brought to the level of the 

 water, can be of most service. At this time, says 

 Professor Cope, they "swim in full siglit, like 

 white aquatic ghosts!" At any noise, down tliey 

 sink to the bottom, to hide beneath the rocks or 

 stones. The head is flat above, and thus enables 

 the mouth to be at the surface. Hence the tactile 

 organs and the mouth are placed in immediate 

 rapport. The number of eggs laid by these fish is 

 about one hundred ; but there is every reason for 

 believing they are hatched in the body ; so that the 

 fish is viviparous. Unfortunately, the condition of 

 sight in the young — a very important fact in the 

 history of the degradation of the eyesight of the 

 species — has never been carefully examined. The 

 length of the Amhlyopsis is about four ana a half 

 inches. So rudimentary are the eyes that they are 

 only exposed after the removal of the skin. Their 

 longest diameter is about the sixteentli of an inch. 

 The optic nerves are placed in contact with the 

 aborted eyes. Although mentioned as a charac- 

 teristic fish of the "Mammoth" cave, i\\^\Amhly- 

 opsis is by no means confined to it, but has quite an 

 extensive distribution, "probably existing in all the 

 subterranean rivers that flow through the great 

 limestone region, underlying the carboniferous rocks 

 in the central portion of the United States." 



Fig. 36. Typhlichthys suhterraneus, nat. size. 



Another species found associated in the cave with 

 the above is Typhlichthys suhterraneus (fig. 36), whose 

 name again illustrates its sightless condition. This 

 fish is only about an inch and a half in length, and 

 the next most peculiar character to its blindness is 

 that it is without ventral fins. It has been found 

 in natural wells as well as in the waters of this 

 extensive cavern, in Kentucky, Alabama, and Ten- 

 nessee. The fishes are all about the same size. All 

 the females yet examined contained only about thirty 

 eggs in their ovaries. The next remarkable genus 

 of fish, greatly resembling the above, from the same 

 geographical region, is Chologaster, of which there are 

 two species, — cormitus and Agassizii. The former 

 (fig, 37) was first found in the ditches of the South 

 Carolina rice-fields. It is only about three inches in 

 length, and is provided with eyes. Its specific name 

 is given to it on account of the horn-like projections 

 above the snout. It is believed to be a viviparous 



fish, but, like the Typhlichthys, has no ventral fins. 

 Having eyes, it has none of the papillary ridges, or 

 organs of touch, possessed by the blind species above 

 named. It is further distinguished from its blind 



Fig. 3/. Chologashr cornutus, nat. size. 



neighbours by being coloured. Thus Chologaster 

 cornutus is brownish-yellow, with dark, longitudinal 

 bands ; whilst C. Agassizii (fig. 38) is of a brownish 

 colour, similar to many of the minnows. The latter 

 species is known only to the subterranean district 

 already mentioned, whilst the former extends to the 

 southern coasts, on the eastern side the Appalachian 

 chain. 



Fig. 38. CJiologaster Agassizii, nat. size. 



It seems strange to find blind fish, with rudi- 

 mentary eyes, living in the same subterranean waters 

 with other species in. which the eyesight is still pre- 

 served. .That the fonner have had their eyesight 

 atrophied, there can be little doubt, the position 

 and arrangement of the optic nerves being sulficient 

 proof. In many respects, however, the Chologaster is 

 a transitionary forui between the really blind fishes 

 and those living naturally in open waters. The only 

 explanation of the relations of these fish is, that 

 Amblyopsis and Typhlichthys have been tenants of the 

 subterranean district much longer than the Cholo- 

 gaster, and hence have been adapted to the circum- 

 stances more perfectly. How little is the value of 

 eyesight to the Chologaster is indicated by the Am- 

 hlyopsis preying upon it 1 This theory of the longer 

 habitaucy of these cave- waters by the former genera 

 is borne out by the fact of their white, colourless 

 skin, free from ornament, whereas the Chologaster 

 has both colour and stripes. Professor Putnam 

 thinks that originally the district now occupied by 

 these subterranean streams was a salt and brackish- 

 water estuary, in which the progenitors of these 

 fishes lived. As the waters became less brackish 

 and more fresh, and the district was elevated, only 

 such species would survive as could adapt them- 

 selves to the changes. Hence he belitves the 

 Chologaster cornutus living in the ditches of the 

 South Carolina rice-fields to be now living " under 

 very similar conditions to those under which others 

 of the family may liave lived in long preceding 

 geological times." The Professor, it should be 



