150 TriE PHlLOSOPHt 



It can move forward, by turning on itfelf like the wheel of a 

 coach. Thus the fea-urchin furnilhes an example of an ani- 

 mal employing many thoiifand limbs in its various move- 

 ments. The reader may try to conceive the number of muf- 

 cles, of fibres, and of other apparatus, which are requifite to 

 the progrclHve motion of this little animal. 



The motion of that fpecies of medufa, or fea-nettle, 

 which attaches itfelf to rocks, and to the larger fhell-fiffi, is 

 extremely flow. The fea-nettles aflume fuch a variety of 

 figures, that it is impofiible to defcribe them under any de- 

 terminate fhape. In general, their bodies have a refemblance 

 to a truncated cone. The bafe of the cone is applied to the 

 rock or other fubflance to which they adhere. With regard 

 to colour, feme of them sre red, fome greeniflij fome whitifh, 

 and others are brov/n. When the mouth, which is very 

 large, is expanded j its margin is furrounded with a great 

 number of flefliy filaments, or horns, fimilar to thofe of the 

 fnail. Thefe horns are difpofed in three rows around the 

 mouth, and give the animal the appearance of a flower. 

 Through each of thefe horns the iea-nettle fquirts water, 

 like fo many jets-d'eau. What is peculiar in the ftructure 

 of thefe creatures, the whole interior part of their body or 

 cone, is one cavity or fi:omach. When fearching for food, 

 they extend their filaments, and entangle any fmall animals 

 they encounter. When they meet with their prey, they in- 

 fbantly fwallow it, and fliut their mouths clofe like a purfe. 

 Though the animal fhould not exceed an inch, or an inch 

 and a half, in diameter, as it is all mouth and ftoniach, it 

 fwallows larare whelks and mufcles. Thefe fhell-animals 

 fometimes remain many days in the fcomach before they are 

 ejected. Their nutrifying parts are at laft, however, ex- 

 tracted J but how does the fea-nettle get quit of the fhell ? 

 The creature has no other aperture in its body but the mouth, 

 and this mouth is the inftrument by which it both receives 



