13 



fuch gellatinous fubjedls, unlcfs he has the hand 2nd the 

 experience of a Swammerdam. But we wifli to induce an 

 opinion that the animal in queftion is nothing more than a 

 teftaceous Afcidia, formed with fliells hke thofe of a Pholas, 

 for the prote6lion of that part which is effential to the per- 

 formance of a work nature has afTigned to it, and which has 

 fo unnaturally been afcribed to fo tender and fragile a fub- 

 flance as the fhell. A little attention to the fubjeft by com- 

 parifon, as well as to the fhell in queftion, would at oiice 

 convince us of the impoffibility of found oak timber being 

 deliroyed by fuch means, either by cutting with its edge, or 

 rafping it by its rugous furface : befides, as an additional 

 proof that fuch is not the cafe, live Ihells are always ob- 

 ferved to be covered with a fine olivaceous epidewih, which 

 muft eventually have been removed by the neceflary fric- 

 tion applied to the boring or filing of timber. The tranf- 

 parent, cartilageous fubllance which has been termed a pro- 

 bofcis, and the centrebit on which the animal turns in the 

 a6l of boreing, muft be intended for a very different pur- 

 pofe ; probably to fupply the place of bone, fimilar to that 

 we find in Sep'ui media, and may afTin: the organs neceifary 

 to the work in queftion. 



If indeed the Teredo navalis was the only mcllufcous ani- 

 mal that had been difcovered capable of perforating fuch 

 liard fubftances, it might not have been furprifing that fuch 

 an opinion had fo long obtained, upon the principle tliat the 

 procvfs was fo gi-adual, that, by the laws of nature, fridfion 

 eventuiilly muil tend to deflruction ; but furely in this cafe 



the 



