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; 
L 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. 
