MOLLUSGA. 41 
line or circle, than night after night they are 
gnawed away, until nothing remains but the brown 
earth, and the label which tells where the seed had 
been. But to the farmer the consequences are 
often much more important. In wet seasons the 
slugs increase with such rapidity in the fields, that 
a wheat-crop after one of clover, tares, or beans, is 
very uncertain, and may be said generally to fail. 
The damage annually done to corn, clover, and 
turnips, by these apparently insignificant creatures, 
is very great. In France and the South of Europe, 
the vineyards are subject to similar attacks from 
the vine snail (Helix pomatia). The buds and 
opening leaves of the vine are gnawed off by them 
as they appear, and the hopes of the autumnal 
vintage are often blasted. 
But much more lameutable than any of these 
are the injuries inflicted upon shipping, and the 
piers and defences of maritime towns, by the ship- 
worm (TZeredo navalis). Ranging over extensive 
seas trom the tropics to the shores of Northern 
Europe, this boring worm, or rather Mollusk with 
a worm-like form, is incessantly engaged in de- 
vouring and destroying all kinds of woodwork that 
is immersed in the sea. Linneus long ago styled 
it the calamity of ships, and there is no maritime 
nation which has not confessed the formidable 
power of this subtle enemy. In the years 1731 
and 1732, the United Provinces were under a 
dreadful alarm; for it was discovered that these 
mollusks had made such depredations on the piles 
which support the banks of Zealand and Freis- 
land, as to threaten them with total destruction, 
reclaiming from man what he had with unex- 
ampled labour wrested from the ocean. A few 
