1 882.] The Blind Cave Fishes and their Allies. 5 



Recurring now to the argument of Mr. Putnam, we note that 

 the discovery of a species of Chologaster which frequents exter- 

 nal waters of an immediately subterranean origin, supplies all 

 needed proof that the genus either has a shorter subterranean 

 history than Amblyopsis, or, at any rate, has remained less closely 

 confined to subterranean situations ; and that in either case the 

 occurrence of eyes, partial absence of sensory papillae and per- 

 sistence of color, are thus accounted for consistently with the 

 doctrine of " descent with modification." 



The extraordinary development, in only a part of the genus, of 

 a special sensory apparatus peculiarly useful to a fish unable, for 

 any cause, to see, points the same way, and gives evidence of a 

 progressing adaptation of these fishes to their unusual abode. 



The intermediate relation of the sensory tubercles of Cholo- 

 gaster to the much smaller ones of young fishes and the perma- 

 nent papillae of Amblyopsis, points out the evident origin of the 

 last through the permanency and higher evolution of structures 

 commonly evanescent in the young. 



especially the naked am 



\ nearly naked kinds, ar 



o usually covered with an ep 



idermis 



several layers deep, and 



by the further fact that 



the papillae of Chologaster wc 









; paper (except for the filam 





the former were denude 



d, as supposed. 













specimen of Amblyopsis 



with the epidermis intac 



■t over considerable areas of tr 



lehead. 







sse regions at once showed ! 





rectness of my surmise, t 



hat they are in Amblyopsis, as in the new Chologaste 



r, to be 









simply 



more highly developed 







young 



fishes. Each papilla he 







similar 





1 ; and I have little doi 



ibt that the figures of Prof. ' 









dentally lost their sensory cells. The 



"filaments" seen hy hi] 



n on two or three of th 



e papillae were probably remi 



iants of 



the cell clusters. Thee 



T-.i dermis of the head is not composed of a single 



layer of 



delicate cells, as described by him, but of at lea 









large spherical or oval 





t, and a 



superficial layer of thin, 1 



flat cells. The epiderm 



i> is. in fact, so thick that it 



almost 











A fuller account of th< 



:se structures will be gi 



yen in another article. 





