940 SUPPLEMENT 
of our animal nutriment. It is indeed well known, that they 
cause considerable injury to fishermen employed in pursuit 
of the crustacea, by the great destruction which they make 
among these animals, because, like them, they inhabit rocky 
places. 
Our vegetable aliments indubitably suffer more considera- 
ble damage from the voracity of the limaces and helices which 
inhabit our fields and gardens. But this is an inconvenience 
proportioned to the development of our agricultural or horti- 
cultural industry, which accumulates in a small space the 
substances of which these animals are fondest. 
Our habitations in the open country do not appear to suffer 
any damage from the mollusca; but it is not the same with 
our constructions on the sea-shore, or with those which are 
destined to float upon its surface: the lithophagous venus, 
and especially the lithophagous mussels, and the pholades, 
to lodge themselves in the stones which constitute our dikes, 
pierce them in all directions; and although they do not do 
this very deeply, they nevertheless hasten the destruction of 
these works. 
This is still more evident in the case of the teredo, the 
species of which select wood in which to excavate their 
dwelling. In those countries where the people are obliged 
to construct dikes supported by wooden piles to protect them- 
selves from the invasions of the sea, as in Holland, the damage 
is considerable ; for at the end of a few years they are so much 
pierced below the level of the water that it is necessary to 
renew them. Vessels which remain a long time in harbour or 
in docks are also exposed to the destructive action of these 
animals, more especially, as it would appear, in the seas of 
warm climates. In fine, even living trees, whose roots or 
stem happen to be submerged, are attacked by the teredo, as 
Adanson relates of certain trees on the banks of the Niger in 
Senegal. 
