175 



The eyes of blind fish. By Carl H. Eigexmann. Published in Proc. U. 

 S. JVat. Mus. for 1S92, with plates. 



[abstract.] 

 Whenever the conditions are favorable blind fishes are developed. These 

 are always related to species inhabiting neighboring open waters. Blind 

 fishes are found in caves, in the deep sea, and at San Diego one lives 

 beneath rocks. While such regions usually contain blind fishes not all the 

 fishes inhabiting these regions are blind. Many species found in the deeper 

 parts of the ocean have well developed eyes, while others living in shal- 

 lower water are blind. The explanation for this fact probably lies in the 

 length of time a given species has inhabited the present locality. In all 

 blind fishes the eyes have undergone a process of degeneration. This is 

 very strikingly seen in the development of the Point Loma blind fish, Typh- 

 logolnu calif or niensis Steindachner. The embryo, before it is hatched, has 

 eyes as well developed as the embryo of any other fish. When the indi- 

 viduals have reached the length of an inch they can still see a short distance, 

 but it is evident that the eye has stopped growing long before this age 

 is reached. In the adult condition the eye has become degenerate and 

 covered with a thick skin, and the fish is totally blind. 



On the PKE^<E^■CE OF an o]'ERfi lum IX THE Asi'KEDiNiD.K. By Carl II. 

 Ei«;enmann. Published in American Naturalist, Januar}^, 18!)2. p. 71, 

 plate VI. 



[abstkact.] 



In our " Revision of the South American Nematognathi," (p. 9) we de- 

 fined the Bunocephalidfe — Aspredinidte as having no opercle. In this we 

 followed Cope, who separated the Aspredinidae from the remaining Nema- 

 tognathi by their lack of an opercle. 



We have lately obtained a specimen of Asjyredo aspredo Linnaeus from the 

 Museum of Comparative Zoology, and have re-examined this point. The 

 closer inspection has demonstrated the presence of a minute operculum at- 

 tached to the upper posterior border of the expanded hyomandibular. It 

 is movable in moist preparations but becomes immovably fixed with dry- 

 ing, which may have led to the original statement. The interopercle is 

 about as large as the opercle, and apparently immovably joined to the hy- 

 amandibular and preopercle. (The skull of this species, with the suspen- 

 sorium, was figured. ) 



