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substance immediately below this called corpus 

 mucosum, of which the nails and hairs are merely 

 modifications, and the true skin or cutis, the 

 seat of the papillae in question ; and there are few 

 animals, even of the lowest tribes, which have 

 not all these envelopes in one form or another. 

 In the armed polype indeed, the sea-blubber, the 

 slug, the earth-worm, and many similar animals, 

 the cuticle takes the form of mere mucilage ; 

 while in the corallines, on the other hand, it as- 

 sumes that of a calcareous mass, by which their 

 bodies are invested. In others again, it is the 

 corpus mucosum which gives them their earthy 

 covering, a proper cuticle being found exterior 

 to it, as in the sea-urchin, the star-fish, and all the 

 testaceous tribes : the sharp prickles, also, on the 

 shell of the sea-urchin, as well as the hairs of the 

 earth-worm, and numerous other animals of this 

 tribe, are merely modifications of the same sub- 

 stance, A proper cutis seems indeed to be want- 

 ing in the corallines, as well as in some other 

 animals of quite the lowest orders ; but in the 

 testaceous tribes, as the oyster, the cloak is pro- 

 bably a modification of this part, and it is accor- 

 dingly upon this, or some corresponding organ, 

 that the tentacula, or immediate instruments of 

 touch, are commonly met with. The perspira- 

 tion from the surface seems to bear the same 

 relation to touch as the saliva bears to taste ; 

 and there are, therefore, few animals which do 

 not perspire in one form or another. In some 

 of these tribes, as the sea-blubber, the perspired 



