386 
THE OCEAN WORLD. 
thick cuirass of that antipathy of the Teredo, iron rust. Ships’ timbers 
are also served with the same protecting coating ; but the copper i ]1 
which ships’ bottoms are usually sheathed serves the same purpose. 
The singular Acephalous Mollusc known to naturalists as the 
Teredo navalis, and popularly as the Ship Worm (Fig. 178), has the 
appearance of a long worm without articulations. Bet ween the valves of a 
little shell, with which it is provided anteriorly, may he seen a sort of 
smooth trnncature, which surrounds a swelling projecting pad or cushion • 
This cushion is the only part of the body of the animal 
which can he regarded as a foot. Starting fr olB 
this point, all the body of the Teredo is envelope^ 
by the shell and mantle, which form a sort of sheath 
communicating by two syphons with the exterior- 
The mantle adheres to the circumference of the 
shell. Above, it forms two great folds, which n)»y 
both he swollen by the afflux of the blood, and acqWf 0 
considerable size. One of these folds placed 111 
advance, which is called the cephalic hood, is worthy 
of attention. The tissue of the mantle is of a greyish 
tint, very light, and transparent enough, especially 111 
the young, to permit of the mass of liver, the ovary* 
the branchiae, and the heart being distinguished lJ1 
the interior, even to counting its pulsations. Th e 
syphons are extensible, and attached the one to the 
other for about two-thirds of their length, the npfl l1 
part being longer and thinner than the lower. It i s 
these tubes that the aerated water enters which i ee ‘ ij 
and enables the animal to breathe. It is discharge" 
by the second tube, when deprived of its ox yg en ’ 
and no longer respirable, carrying with it the uselea- 
products of digestion. This movement is contiuu 0 " ’ 
but from time to time the animal shuts at once 
orifices of both tubes, and slightly contracts itself- 
The shell, seen on the side, presents an irreg 
ularly 
triangular form; it is nearly as broad as it is 1°®?’ 
ilg ' 17 (LinSs°)." a ' als its two valves are solidly attached the one 1° ^ 
other above and below by the mantle in such a manner as only 
permit of very slight movements. It is coloured in yellow and bro 
