60 INTRODUCTION. 



victims as thirst, or any other occasion, may bring 

 to the hanks. 



On the other hand, fishes live, and move, and 

 have their being permanently in the water; and, 

 so far from requiring an occasional change of the 

 medium by which they are surrounded, are, in 

 general, soon destroyed by being removed into the 

 air. It is requisite, indeed, that the water in which 

 fishes reside be charged with a certain proportion of 

 air, otherwise it could not minister to their respira- 

 tion ; but it is still through the water that air is in 

 them subservient to this function ; and they can no 

 more breathe the air, unless water be its vehicle, 

 than terrestrial animals can breathe it in that state 

 of admixture. 



It is true, indeed, that some fishes, particularly 

 those popularly called " Flat Fish," such as the 

 turbot, the halibut, the sole, the plaice, and the 

 flounder, may be said to inhabit rather the mud 

 and sand at the bottom of the water, than the 

 water itself; and the same is the case with the 

 great loche ( 'Colitis fossilis ) ', a native of Germany, 

 which seldom quits the mud, except on the approach 

 of stormy weather hence it has sometimes been 

 used as a kind of living barometer; as also with 

 the fossile silure (Silur us fossilis), a native of the 

 Indian lakes, from the muddy bottom of which it 

 is sometimes dug up in the same manner as the 

 great loche ; and hence the specific name fossilis^ 

 by which both are distinguished. Other fishes, 

 again, as the laimer, or sand-eel (Ammodyte* 



