THE SHELL-FISII OF THE COAST. 



41 



attack the floating cocoa-nut. The rapidly-forming 

 burrow follows in a sinuous line the grain of the 

 wood, passing out of the way of knots, and con- 

 scientiously avoiding the burrows of confederate 

 workers. In this manner a piece 

 of wood is soon honey-combed. 

 The entrance is made by a minute 

 hole, the size of the barrow in- 

 creasing with the growth of the 

 auimal. A lining of white calca- 

 reous matter usually extends along 

 the entire length of the burrow, 

 to the farther end of which the 

 two valves of the shell are at- 

 tached. 



It is well ascertained in the case 

 of the ship-worm that the burrow 

 is largely, or even principally, ex- 

 cavated by shell-abrasion , although 

 perhaps the exact process has not 

 yet been clearly made out. Large 

 quantities of the wood-dust are 

 frequently found within the intes- 

 tine of the auimal, and it appears 

 not unlikely that some of it is 

 intentionally swallowed, and even 

 used for nourishment. The rav- 

 ages of the ship-worm may be such 

 as to destroy Mntbin a very short 

 time the stoutest timber; indeed, it is said that 

 piles that had been driven only s|x or seven weeks 

 on the Dutch coast were found at the end of that 



4* 



Wood bobed by 

 ship-wokm. 



