30 BRITISH FRESH-WATER FISHES 
herrings, carps, and other families, there exists a more or less 
elaborate connection between the air-bladder and the auditory 
process. 
In the lampreys the labyrinth consists only of two semi- 
circular canals and a vestibule. 
Of the extent to which fishes exercise and are guided by the 
sense of smell very little is known. Early writers upon angling 
The sense prescribe various odoriferous unguents, calculated 
of smell. to attract fishes to the bait ; but as the use of such 
anointing has been entirely discontinued in modern practice, 
these prescriptions must be regarded as purely empirical. Had 
assafcetida, oil of ivy, or the other strong-smelling substances 
recommended proved efficacious, fishermen would have been 
slow to abandon them. It is said that trout are drawn from 
long distances by the odour of potted salmon-roe ; but of this 
I cannot testify from observation, the use, sale, or possession 
of that article being contrary to law. Nevertheless, seeing that 
all fishes, even the brainless lancelet, possess olfactory organs, 
it is certain that they possess also the power of smelling. But 
the exercise of this faculty differs from that of terrestrial 
vertebrates in being totally disconnected with the machinery 
and function of respiration. The “breath of his nostrils” 
is the life of man ; his olfactory nerves vibrate to the odori- 
ferous atoms borne on the atmosphere; he cannot smell 
without performing half the complete act of respiration—that 
of inhaling ; and he cannot inhale properly, i.e., through the 
nostrils, without being sensible of any odour strong enough to 
excite his olfactory nerve. But fish breathe through the mouth 
and gills, with which the nostril has no connection whatever ; * 
the act, therefore, of admitting water to the nasal sac, whether 
it be voluntary or unconscious, is quite independent of 
breathing. 
In British fresh-water fish, with the exception of one 
* Except in the Difnoi, such as Lepidosiren and Protopterus, which 
spend part of the year torpid in the dried mud of rivers. 
- Pomebrgr 
