436 THE SHIP-WORM. 



to ciliary action, because, in fact, there is no current between the shell, or siphon, and 

 the wall of the tube." As soon as the animal has completely buried itself it ceases to 

 burrow, and only projects the ends of the siphon from the aperture of the tunnel. 



Some species of Piddock are eaten, Pholas costdta, one of the South American 

 species, being a good example. In England it is seldom used except for bait, its fine 

 white foot, which looks, when fresh, as if cut out of ice, answering that purpose 

 admirably, its glittering whiteness serving to attract the attention of the fish, and its 

 toughness causing it to adhere strongly to the hook. 



Several other genera are worthy of notice, among which the Martesia is, perhaps, the 

 most curious, shells belonging to this genus having been found in cakes of wax floating 

 on the waves off the Cuban coast, and others in masses of resin on the shores of 

 Australia. The PAPER PHOLAS, represented on the right hand of the illustration, is 

 shown as it appears when boring into the red earth of Brighton. 



IN the accompanying illustration we have an example of a creature, which, though 

 useful enough in many ways, and doing good service in transmuting dead and decay- 

 ing substances into living forms, is yet the dread of mariners and the terror of pier 

 builders. 



The SHIP-WORM, as this mollusc is appropriately called, from its depredations on the 

 bottoms of ships and all submerged wooden structures, is found in most seas, and on 

 our own coasts works fearful damage by eating into piles, planks, or even loose wood 

 that lies tossing about in the ocean. I have now before me a portion of the pier at 

 Yarmouth, which is so honeycombed by this terrible creature that it can be crushed 

 between the hands as if it were paper, and in many places the wood is not thicker than 

 ordinary foolscap. This piece was broken off by a steamer which accidentally ran 

 against it ; and so completely is it tunnelled, that although it measures seven inches 

 in length and about eleven in circumference, its weight is under four ounces, a 

 considerable portion of even that weight being due to the shelly tubes of the de- 

 stroyers. 



I have also a block of oak, picked up off Broadstairs, where the Ship-worm has been 

 nearly, though not quite so destructive as in the former instance. This specimen is 

 notable, as giving an example of a principle on which many piers, etc., have been 

 protected from this mollusc. A large iron bolt passes through the midst of the block, 

 and the rust of the projecting head has spread itself for some distance over the wood. 

 Multitudes of holes, large and small, surround the bolt, but not one has pierced that 

 portion over which the rust extends. Knowing the objection entertained by the Ship- 

 worm to rust, engineers have been in the habit of driving a number of short iron nails, 

 with very wide heads, into the timber, arranging them in regular rows, with their heads 

 at no great distance from each other. The action of the salt water soon causes the 

 rust to spread over the spaces between the heads, and upon these spots the Ship-worm 

 refuses to settle. 



Another plan, and a very effective, though rather expensive one, consists in forcing 

 a solution of corrosive sublimate into the pores of the wood. This salt of mercury is 

 very destructive to animal life, and M. Quatrefages asserts that one twenty-millionth 

 part of corrosive sublimate is enough to destroy all the young Ship-worms in two hours, 

 and that a ten-millionth part would have the same effect in forty minutes. He there- 

 fore proposes that ships should be cleared of this terrible 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 are 

 not so rapid in their operation. The wooden piles on which jetties and piers are 

 supported can be preserved in the same manner. Iron, however, is now rapidly super- 

 seding wood for such structures, and is quite impervious to the attacks of any mollusc, 

 no matter how sharp its teeth. 



When removed from the tube, the Ship-worm is seen to be a long grayish white 

 animal, about one foot in length and half an inch in thickness. At one end there is a 

 rounded head, and at the other a forked tail. The curious three-lobed valves are shown 

 in the foreground as they appear when separated from the animal. The burrow which 



