104 MOTIONS OF ANIMALS. 



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they are obliged to pass through large tracts, and they have 

 also many enemies to avoid. 



Timid animals, as the hare, the rabbit, the guinea-pig, &c., 

 are almost perpetually in motion. Even when perfectly un- 

 disturbed, they are restless, and betray a continual anxiety 

 of danger. They run about, stop short, erect their ears, and 

 listen. The guinea-pig frequently raises itself on its hind 

 legs, and snuffs all around to catch the scent of food when 

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



The movements of many animals are so extremely slow 

 that some of them, particularly those of the shell tribes, are 



fenerally supposed to be destitute of the power of moving, 

 t is a common notion, that both the fresh and salt water 

 muscles have not the locomotive faculty. But this is a vul- 

 gar error. It is almost unnecessary to mention, that the 

 exterior part of muscles consists of two shells hinged together, 

 which the animals can open or shut at pleasure. Every per- 

 son must likewise have observed, in the structure of the ani- 

 mal itself, a fleshy protuberance of a much redder color, and 

 Denser consistence, than the other parts of the body. This 

 muscular protuberance, which consists of two lobes, has been 

 denominated a trunk or tongue; but it is an instrument 

 by which the creature is enabled to perform a progressive 

 though a very slow motion ; and, therefore, in describing its 

 manner of moving, I shall call these two lobes the animal's 

 tentacula or feet. 



When inclined to remove from its present situation, the 

 river muscle opens its shell, thrusts out its tentacula, and 

 while lying on its side in a horizontal position, digs a small 

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

 same tentacula, the animal makes the shell fall, and thus brings 

 it into a vertical position. We have now got our muscle on 

 end ; but how is he to proceed ? He stretches forward his ven- 

 tacula, by which he throws back the sand, lengthens the fur- 

 row, and this fulcrum enables him to proceed on his journey. 

 V With regard to marine muscles, their progressive motion is 

 performed in the same manner, and by the same instruments. 

 When not in motion, they are firmly attached to rocks or small 

 stones, by many threads of about two inches in length, which 

 serve the purpose of a cable. Without this provision of na- 

 ture, these animals must become the sport of the waves, and 

 the species would soon be annihilated. But how does the 

 creature spin these threads? A cylindrical canal extends 

 from the origin to the extremity of the tentacula. In this 



