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THE INHABITANTS OF THE SEA. 



Shipworm. — (Teredo navalis.) 



therefore completely inadequate for its defence. For better 

 security it bores deep passages in submerged timber, which it 

 lines with a calcareous secretion, closing 

 the opening with two small lids. Un- 

 fortunately, while thus taking care of 

 itself, it causes considerable damage to 

 the works of man. It is principally 

 to guard against the attacks of this 

 worm that ships are sheathed with 

 copper, and the beams of submarine 

 constructions closely studded with nails. 

 During the last century, the Teredo 

 caused such devastations in the dykes which guard a great part 

 of Holland against the encroachments of an overwhelming 

 ocean that the Dutch began to tremble 

 for their safety ; and thus a miserable 

 worm struck terror in the hearts ot 

 a nation which had laughed to scorn 

 the tyranny of Philip II., and bid de- 

 fiance to the legions of Louis XIV. 



But while blaming the teredo for its damages, justice bids us 

 not pass over in silence the services which it renders to man. If it 

 here and there destroys useful constructions, on the other hand, it 

 removes the wrecks that would otherwise obstruct the entrance 

 of rivers and harbours ; and we may ask whether these services 

 do not outweigh the harm it causes. The pholades also belong 

 to the noxious animals ; they perforate the walls and calcareous 

 jetties which man opposes to the fury of the sea, or raises for the 

 creation of artificial harbours and land- 

 ing places, destroy their foundations, and 

 gradually cause their destruction. 



The foot of the lamellibranchiates 

 presents a great variety of form, and is 

 found in various degrees of development, 

 gradually passing into a rudimentary 

 state, until finally it is completely 

 wanting in the oyster family. In most 

 of those which live at large it is strong 

 and muscular, serving either as an ex- 

 cellent spade for speedy concealment in the sand when an 



