48 A PRELIMINARY LIST OF THE 



tucky caves, some thirty miles below the surface, 

 a number of fishes among whose very numerous 

 offspring will be some defective in sight, as some 

 babies are born blind, or without any eyes at all. 

 The fish who can see some faint glimmerings of 

 light will swim away toward that light, while those 

 will remain that cannot perceive the gleams. This 

 with every succeeding generation would occur, the 

 stronger in sight swimming away and the weaker 

 remaining, and as the breeding would therefore oc- 

 cur between those of the worst sight, fish would be 

 born with weaker eyes and weaker until born blind." 



The above is quoted from a newspaper, and 

 probably does not in all respects report Professor 

 Lankester correctly, since it is hardly to be sup- 

 posed that he believes Mammoth Cave to penetrate 

 the earth for a distance of thirty miles. But in 

 the main it gives his theory as to the origin of cave 

 animals correctly. It will probably strike the ma- 

 jority of those who are familiär with the caves sim- 

 ply as a curiosity in speculation. The views ex- 

 pressed by Herbert Spencer (Populär Science 

 Monthly, xliii, 487, 488) seem to me much more 

 sound and consistent with the facts : 



"The existence of these blind cave-animals can 

 be accounted for only by supposing that their re- 

 mote ancestors began making excursions into the 

 cave, and, finding it profitable, extended them, 

 generation after generation, further in, undergoing 

 the required adaptations little by little.' , 



357. Chologaster agassizii, Putnam. 



Underground streams. 



358. Blind Fish (Typhlichlhys subterraneus , Girard). 



Inhabits wells, caves and Springs in the vicin- 

 ity of Mammoth Cave. 



