322 THE OCEAN WORLD. 
ment of spring. Four months after some fishermen, hoping to turn her 
materials to advantage, raised the boat. But in that short space of 
time the Teredos had committed such ravages that the planks and 
timbers were riddled and worm-eaten so as to be totally useless.” 
At the beginning of the eighteenth century, half the coast of 
Holland was threatened with annihilation because the piles which 
support its dikes and sea-walls were attacked by a 
species of Teredo; and it proved no contemptible 
foe. Many hundreds of thousands of pounds were 
expended in order to avert the threatened danger. 
Fortunately, a closer attention to the habits of the 
molluscs has brought a remedy to a most formidable 
evil; the mollusc has an inveterate antipathy to iron 
rust, and timber impregnated by the oxide of iron is 
safe from its ravages. The taste of the Teredo being 
known, it is only necessary, in order to avoid this 
dangerous mollusc, to sink the timber which is to be 
submerged in a tank of prepared oxide of iron— 
clothed, in short, in a thick cuirass of that antipathy 
of the Teredo, iron rust. Ships’ timbers are~also 
covered with the same protecting coating; but the 
copper in which ships’ bottoms are usually sheathed 
serves the same purpose. 
The singular Acephalous Mollusc known to natu- 
ralists as the Zéredo navalis, and popularly as the Ship 
Worm, has the appearance of a long worm without 
articulations. Between the valves of a little shell, with 
which it is provided anteriorly, may be seen a sort 
of smooth rim, which surrounds a swelling projecting 
pad or cushion. ‘This cushion is the only part of the 
- Fig. 128. : : 
Teredo navalis body of the animal which can be regarded as a foot. 
(Linnzus). 
Starting from this point, all the body of the Teredo 
is enveloped by the shell and mantle, the latter of 
which forms a sort of sheath communicating by two siphons with 
the exterior (Fig. 128). 
The mantle adheres to the circumference of the shell. The tissue 
of. the mantle is of a greyish tint, very light, and transparent enough, 
especially in the young, to permit of the mass of the liver, the ovary, 
the branchiz, and the heart being distinguished in the interior, even 
to counting the pulsations of the latter. The siphons are extensile, and 
attached the one to the other for about two-thirds of their length, 
It is by these tubes that the aérated water enters which feeds the 
