NATURALISTS CABINET. 



The tail a chief instrument of motion. 



which the fin is folded. To produce a retrograde 

 motion, tbe pectoral fins are struck in a contrary 

 direction. If the creature desire to turn, a blow 

 from the tail sends it about in an instant; but if 

 the tail strike both ways, then the motion is 

 progressive. And it is observable, that some fish 

 that have no fins at all, such as lobsters, dart for- 

 ward with prodigious rapidity by means of their 

 tail, which is now found to be the instrument of 

 progressive motion in all the aquatic species; 

 and when the tail is cut off, the fish gives itself 

 up entirely to the impulse of the water, being 

 deprived of all motion. 



A slimy glutinous matter, with which fish are 

 in general furnished, defends their bodies from 

 the immediate contact of the surrounding fluid, 

 and which, likewise, in all probability, assists 

 their motion through the water. Beneath this, 

 in many kinds, is found a strong covering of 

 scales, that like a coat of mail, defends it yet 

 more powerfully ; and under that, before we 

 come to the muscular parts of the body lies an 

 oily substance, which also tends to preserve the 

 requisite warmth and vigor. The scales of this 

 cuticle are laid on one another like tiles on a 

 building, and the use of which is analogous to 

 the hair, wool, feathers, &c. of other animals, 

 and below which their proper cuticula and cutis 

 may be discovered. 



In order to prove whether fish which are 

 formed for living entirely in the water, could 



