THE SHIPWORM. 



107 



appendages, passing rapidly through the water. It does not, 

 however, retain this form for more than six and thirty hours, but 

 undergoes a further process of development, and is then fur- 

 nished with a distinct apparatus for swimming and crawling. 

 It also possesses rudimentary eyes, and in that portion of the 

 body which may be considered the head, there are organs of 

 hearing resembling those of certain molluscs. When it has 

 passed its full time in this stage of development, it fixes upon 

 some favourable locality, and then undergoes its last change, 

 which transforms it into the worm-like mollusc with which 

 naturalists are so familiar. 



SHIPVVURM 



The ravages committed by this creature are almost incredible. 

 Wood of every description is devoured by the Shipworm, whose 

 tunnels are frequently placed so closely together that the parti- 

 tion between them is not thicker than the paper on which this 

 account is printed. As the Teredo bores, it lines the tunnel with 

 a thin shell of calcareous matter, thus presenting a remarkable 

 resemblance to the habits of the white ant. When the Teredos 

 have taken entire possession of a piece of timber, they destroy it 

 so completely, that if the shelly lining were removed from the 

 wood, and each weighed separately, the mineral substance would 

 equal the vegetable in weight. 



The Shipworm has been the cause of numerous wrecks, for it 



