OF NATURAL HISTORY. 14^ 



Timid animals, as tiie hare, the rabbit, the Guiney-pig, 

 ^c. are almoft perpetually in motion. Even when perfedly 

 undifturbed, they are refllefs, and betray a continual anxiety 

 of danger. They run about, flop fhort, eredt their ears 

 and liften. The Guiney-pig frequently raifes itfelf on its 

 hind legs, and fnufFs all around to catch the fcent of food 

 when hungry, or to increafe its circle of hearing when afraid. 



The movements of many animals are fo extremely flow, 

 that fome of them, particularly thofe of the fhell tribes, are 

 generally fuppofed to be deftitute of the power of moving, 

 It is a common notion, that both frefli and fait water muf^ 

 cles have not the locomotive faculty. But this is a vulgar 

 error. It is almOft unneceiTary to mention, that the exte- 

 rior part of mufcles confifts of two fhells hinged together, 

 which the animals can open or fhut at pleafure. Every per- 

 fon mufl likewife have obferved, in the ftruclure of the ani- 

 mal itfelf, a flefliy protuberance of a much redder colour, 

 and denfer conliftence, than the other parts of the body. 

 This mufcular protuberance, which confifls of two lobes, has 

 been denominated a trimk, or tongue : But it is an inftru- 

 ment by which the creature is enabled to perform a pro- 

 grefiive, though a very flow motion •, and, therefore, in de- 

 fcribing its manner of moving, I fhall call thefe two lobes 

 the animal's tentacula, or feet. 



When inclined to remove from its prefent lituation, th^ 

 river-mufcle opens its fhell, thrufts out its tentacula, and, 

 while lying on its fide in an horizontal pofition, digs a fmali 

 furrow in the fand. Into this furrow, by the operation of 

 the fame tentacula, thd animal makes the fliell fall, and thus 

 brings it into a vertical pofition. "We have now got our muf- 

 cle on end •, but how is he to proceed ? He flretches forward 

 his tentacula, by which he throws back the fand, lengthens 

 the furrow, and this fulcrum enables him to proceed on his 

 journey. 



