XV1H INTRODUCTION. 



From the rigid nature of the scaly covering in the gene- 

 rality of fishes, it is probable they possess but little external 

 sense of touch ; but they are not wholly unprovided with 

 organs "which in the selection of their food are of essential 



o 



service. The lips in many species are soft and pulpy ; the 

 mouths of others are provided with barbules or cirri, largely 

 supplied with nerves, which are doubtless to them delicate 

 organs of touch, by which they obtain cognizance of the qua- 

 lities of those substances with which they come in contact. 

 The Gurnards may be said to be provided with elongated, 

 flexible, and delicate fingers, to compensate for their bony 

 lips. It is a rule, almost without an exception that I am 

 aware of, that those fishes provided with barbules or cirri 

 about the mouth obtain their food near the ground ; and these 

 feelers, as they are popularly called, appear also to be a valu- 

 able compensation to those species which, restricted by in- 

 stinctive habits to feeding near the bottom of water that is 

 often both turbid and deep, must experience more or less 

 imperfect vision there from the deficiency of light. 



The olfactory nerves in fishes are of very large size, and 

 the extent of surface over which the filaments are disposed is 

 very considerable. The nostrils are generally double on each 

 side, but both openings lead to one common canal. Their 

 sense of smell may be presumed to be acute from the selec- 

 tion they are known to make in their search after food ; and 

 the advantage said to be gained by the use of various scented 

 oils with which some anglers impregnate their baits. A Pike 

 in clear water has been seen to approach and afterwards turn 

 away from a stale gudgeon, when at the distance of a foot 

 from his nose, as if perfectly aware at that distance of the 

 real condition of the intended prey. Mr. Couch has ob- 

 served in a Fifteen-spined Stickleback of large size, kept in 

 a glass vessel, that the opening and closing of the nostrils 

 was simultaneous with the action of the gill-covers, and he 



