TTTE SHORES OF BRITAIN". 79 



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 substances, 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 

 manv 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 



