THE SHORES OF BRITAIN. "9 
motion possessed by fishes is partly dependent on 
their simplicity of figure, the absence of those pro- 
minent limbs which project from the bodies of most 
other vertebrate animals; the head, without any 
visible neck, merging into the rounded body, which 
terminates in the tail in an almost unbroken out- 
line, for the fins are usually so slight and mem- 
branous in their texture as scarcely to diminish this 
unity of form. The smooth and glittering armour, 
in which these animals are for the most part in- 
vested, tends to the same end. Feathers or fur 
would greatly impede progress through water; and 
as the tribe of fishes are what is commonly called 
cold-blooded, or of nearly the same temperature as 
the fluid that surrounds them, those non-conductors 
of heat would be of no service, the animal heat ne- 
cessary for existence not being liable to be abstracted. 
In place of those clothing substarices, the fish’s 
body is encased in a coat of mail formed of many 
pieces of similar shape, of a transparent horny sub- 
stance, which are imbedded in the skin on the side 
next the head, and overlap the succeeding ones 
at the posterior edge, like the tiles of a house. 
It is obvious how beautifully and effectually this 
formation precludes any impediment in swimming, 
arising from the free edges of the scales. These 
are so Closely pressed on each other, that the water 
cannot penetrate, and are covered, moreover, in 
many fishes with a glutinous slime, which water 
does not dissolve. The scales of fishes afford objects 
of very beautiful structure when viewed with a mi- 
croscope. They are various in their form; those 
