26 THE COMMERCIAL SE4 FISHES OF 



as in the blind or bib. In the snipe-fish (Centriscus), one 

 example of which has been captured in this country, some 

 minute scales are present upon the outer fourth of the skin 

 covering the globe of the eye, except in its anterior portion, 

 probably for its protection against direct injuries. Some 

 forms have a sort of almost fixed eyelid along the upper 

 portion of the eye, consisting of thickened and coloured 

 skin, in which scales are often present, as in the sting-fish 

 (Trachinus). This opaque upper lid, evidently used as a 

 protection, is found in some flat fishes. In the turbot, not 

 only does this thick skin cover its upper and lateral por- 

 tions, but, being insufficient to protect the eye from the 

 irritation of the sand in which it hides itself, it is able 

 to elevate a thick lower eyelid or else to depress the trans- 

 parent portion of the globe of the eye below this fold of 

 skin. 



Doubtless the foregoing modifications of fishes' eyes 

 might be largely increased, and many more illustrations 

 given, but I think they are sufficient for the purpose of 

 pointing out that the skin which passes across this organ 

 may be employed as a protection when it is scaled, coloured, 

 thickened, or even transparent. 



Fishes are provided with organs of smell, which enable 

 them to receive impressions from the surrounding medium, 

 direct them to their food, or warn them against impurities. 

 These organs are placed much as in the higher animals, but 

 (except in the Cyclostomatd) with this difference, that they 

 never communicate with the mouth, or are related to the 

 function of breathing, for were their delicate lining mem- 

 brane subject to incessant contact with currents of water, 

 such would doubtless occasion deleterious results. The 

 nostrils are depressions or cavities, lined with a large and 

 highly vascular pituitary membrane, packed into as small a 



