THE BORERS OF THE SEA. 6 3 



work consists in forcing into its pores a solution of corrosive sublimate. 

 The only objection to this method is its great cost. Quatrefages, how- 

 ever, asserts that one twenty-millionth part of corrosive sublimate is 

 enough to destroy all the young Ship-worms in two hours. He, there- 

 fore, proposes that ships should be cleared of this fearful pest by 

 being taken into a closed dock, into which a few handfuls of corrosive 

 sublimate should be thrown and well mixed with the water. The salts 

 of copper and lead have a similar effect, but do not act so instan- 

 taneously. 



The Teredo does not perforate rock, but the Pholas acts an impor- 

 tant part in bi'inging about geological changes, owing to his habit of 

 boring rocks. There is no doubt that the chalk-cliffs of England are 

 first tunnelled by the Pholades, and then gradually destroyed by the 

 waves of the sea. 



Of the Date-shell, another very interesting borer, Wood gives the 

 following account : " It is truly a wonderful little shell. Some of the 

 hardest stones and stoutest shells are found pierced by hundreds of 

 these curious beings, which seem to have one prevailing instinct, 

 namely, to bore their way through every thing. Onward, ever on- 

 ward, seems to be the law of their existence, and most thoroughly do 

 they carry it out. They care little for obstacles, and, if one of their 

 own kind happens to cross their path, they quietly proceed with their 

 work, and drive their tunnel completely through the body of their 

 companion." 



Of the Saxicava rugosa, another borer, "Wood gives this descrip- 

 tion : " It is a fiattish bivalve, symmetrical in shape when young, 

 but oblong when old. It burrows as rapidly as the Lithodomus, and 

 into rock of adamantine density. Sometimes it bores into corals, fre- 

 quently into limestone, and often into shells, which it penetrates as 

 deeply as the Date-shell. Some of the enormous stones employed in 

 building the Plymouth Breakwater are now much wasted by the holes 

 made in them by the Saxicava.'''' Like the Date-shell, too, this animal 

 runs its tunnels at every angle, and turns out of its course for no con- 

 sideration whatever. 



The Razor-shell makes a burrow in the sand, and there lives with its 

 siphon, or recurved food-tube, appearing just above the mouth of the 

 burrow. It may often be seen " spouting," or sending forth small jets 

 of water from its hiding-place in the sand after the tide has retreated. 

 On examining the spot cautiously for the creature is somewhat shy 

 two round holes in the sand, answering to the two fringed openings 

 of the Razor-shell's siphon, will be seen, resembling a key-hole, and 

 each large enough to admit a common goose-quill. But, if the animal 

 be approached rudely, or if the finger be placed on the openings, the 

 mollusk disappears deep in the burrow. The Razor-shell is possessed 

 of a very muscular " foot," as it is called, but it might as well be 

 named a hand or a tongue. By means of this organ, which they 



