88 BULLETIN OF THE 



dinary development, iu only a part of the genus, of a special sensory 

 apparatus peculiarly useful to a fish unable, for any cause, to se% 

 points the same way, [i. e. to the supposition that this genus has a 

 shorter subterranean history than Amblyopsis,] and gives evidence of a 

 progressing adaptation of these fishes to their unusual abode. The in- 

 termediate relation of the sensory tubercles of Chologaster to the much 

 smaller ones of young fishes and the permanent papillae of Aml)lyopsis, 

 points out the evident origin of the last through the permanency 

 and higher evolution of structures evanescent in the young." This is 

 probably the clearest case furnished by vertebrates of the loss of sight 

 being recompensed by a higher development of the tactile sense. 



As regards the tactile papillae in the Cuban blind fish (Lucifuga), Put- 

 nam ('72, p. 9), who examined a specimen sent to the Museum of Com- 

 parative Zoology by the discoverer of the fish. Professor Poey, vsays : " In 

 the Cuban blind fish we find ciliary appendages on the head and body 

 quite distinctly developed, evidently of the same character as those of 

 Amblyopsis, and answering the purpose of tactile organs. . . . There are 

 eight of these on the top of the head, . . . and quite a number arranged 

 in three rows on each side of the body, showing that the tactile sense 

 is well developed in these fish." 



This, so far as I am aware, is all that is known on the subject, and 

 can be regarded as furnishing nothing more than a probability that 

 touch papillte have been here developed to compensate the fish for sight- 

 less eyes. The writer just quoted remarks further, that it is singular 

 that the barbels on the jaws, so commonly found in the Cod family and 

 its allies (to the latter of which the Cuban fish belongs), are entirely 

 wanting. As is well known, Lucifuga is a cave dweller, and consequently 

 the conditions which have produced its rudimentary eyes are more 

 similar to those that have produced the corresponding change in Am- 

 blyopsis than to those that have had the same effect on Typhlogobius. 

 And this fact may strengthen the probability above referred to ; for, 

 from the difference in conditions of life, Amblyopsis and Lucifuga are in 

 all probability much more active than Typhlogobius, and this would 

 make the tactile sense more useful to the first two species than to the 

 last one. 



We will now notice the condition of the blind deep-sea fishes with 

 reference to the touch papillae. The three forms described by Giin- 

 ther ('80), Typhlonus nasus, Aphyonus gelatinosus (p. 548), and 

 Ipnnps murrayi (p. 585), are all without barbels, and, so far as 

 known, other special tactile structures. The two genera first named 



