tISHES. 
116 
covering to the body, and at the same time defend 
it from the pressure of the water, dhey are really 
curious, and afford sufficient cause for admiration 
when examined by the microscope. The whole sur- 
face of the animal is moistened by an oily substance, 
which is probably intended to defend it from ex- 
treme cold. 
We should reasonably suppose, that, as the fins 
are the instruments of motion in fishes, those 
provided with the greatest number would be the 
quickest swimmers ; but this is not always the case, 
as the shark, who wants the ventral or belly fins, 
Swims with greater velocity than the haddock, 
which is completely fitted for motion. Assisted by 
these natural oars the fish cuts the water with 
amazing velocity, and in a moment passes the 
swiftest-sailing vessel. They also serve to keep the 
body properly balanced, particularly the belly fins, 
whose chief function is to regulate the motions of 
the body by poising it in equilibrium ; so that, if 
the fish only moves the fins on its right side, and 
brings those on its left close to the body, all the 
motion is immediately determined that way ; just 
as a boat with two oars, when only one of them is 
employed, will always turn to the side to which it 
is impelled by the other *. deprive the fish of these 
fins, and the back, which is heavier than the belly, 
being no longer kept in a due poise, will slant on 
one side, or be quite inverted ; and this happens to 
dead fish, who rise to the surface of the water with 
their fins uppermost. It is not to the fins alone 
