158 OUTLINES OF ICHTHYOLOGY. 



with which they come in contact. A remarkable 

 instance is observable in the Gurnards, which may 

 be said to be provided with long, flexible, sensitive 

 fingers, to compensate for their bony lips. 



It is an almost universal rule that " bearded " 

 fish, like the Barbel and Gudgeon, obtain their 

 food close to the ground ; and these feelers appear 

 to be given as a compensating equivalent to species 

 which, restricted by instinct to feeding near the 

 bottom of water that is often turbid and deep, 

 must necessarily experience more or less imperfect 

 vision from the deficiency of light. 



Fish are subject to comparatively few diseases, 

 probably owing to the even temperature of the 

 medium in which they exist. They are, however, 

 very liable to external and internal parasites, which 

 (with the exception of those peculiar to the 

 Salmon) generally attach themselves to sick or 

 wounded fish. 



The sense of Smell in fish is considered by most 

 comparative anatomists to be very perfect. The 

 nerves are large, and the extent of the membranes 

 over which they expand so considerable that in a 

 shark 25 feet long.it has been calculated at 12 to 

 1 3 square feet. 



The discrimination shown by fish in the selec- 

 tion and rejection of food, and the preference 

 stated to be exhibited for certain scented oils, &c., 

 have been adduced as arguments in favour of 



