THE SHIP WORM. 
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is commissioned to destroy. The Shipworm ( Teredo navalis ), 
on the contrary, always burrows with the grain, and never makes 
a transverse tunnel, unless turned from its course by some 
obstacle, such as a nail, or the burrow of another Teredo. 
At first sight, few would perceive that the Shipworm belongs 
to the same class as the oyster and the snail, for it is long, 
slender, and worm-like in shape, from six to eight lines in 
diameter, and nearly a foot in length. One end is rather larger 
SHIPWORM. 
than the shaft, if we may use the term, and is furnished with a 
pair of curved and very narrow shell-valves, while the other is 
divided into a forked apparatus containing the siphon. The 
colour is greyish-white. 
Such is the aspect of the Shipworm when adult, but in its 
early stages of existence it possesses a totally different form. 
When it first issues from the sheltering mantle of its parent, it 
is a little, round, lively object, covered with cilia, like a very 
minute hedgehog, and, by the continual movement of these 
appendages, passing rapidly through the water. It does nor. 
