FISHES. 13 



nerves are very large, and distributed over a great 

 extent of surface. Professor Owen concludes, 

 from certain anatomical peculiarities, that some 

 Fishes, as the Rays, which have the olfactory 

 nerves greatly developed, " scent as well as smell; 

 i. e., actively search for odoriferous impressions 

 by rapidly changing the current of water through 

 the olfactory sac."* Many observations of living 

 Fishes concur with deductions from structure 

 to prove the exercise of smell. A Pike was seen 

 to approach a dead Fish, but when within a foot 

 of it, turned away, as if he had then become 

 aware of what was the fact, that his supposed 

 prey was stale. Mr. Couch observed, in a Stickle- 

 back, kept in a glass vase, that the nostrils opened 

 and closed simultaneously with the action of the 

 gill- covers, and felt convinced that the water was 

 received and rejected for the purpose of sensa- 

 tion. f Mr. Jesse states that Fishes prefer paste 

 and worms that have been prepared with par- 

 ticular perfumes. 



No external ear, nor even an auditory orifice 

 is detected in Fishes, yet there is a complex in- 

 ternal apparatus of large size, for the reception 

 of sounds. In many species of bony Fishes there 

 is a communication between the acoustic cham- 

 ber and the air-bladder, of which we shall pre- 

 sently speak. Mr. Jesse has seen Fishes start 

 at the report of a gun, when they could not see 

 the flash ; and several instances are on record of 

 tame Fishes having been taught to come to the 

 surface of the water at accustomed sounds. 



From the density of the medium inhabited by 



* Comparative Anatomy, ii. 202. 



t Yarrell, British Fishes, Introd. xix. 



