144 SUPPLEMENT 
the determination of the identity of the different strata of the 
earth. It will discover, in the innumerable quantity of these 
animals, succeeding each other from generation to generation, 
in the depths of the sea, one of the evident causes of the in- 
crease of continents. | 
But man can find, in the knowledge of the mollusca, appli- 
cations still more direct to his well-being in society, either in 
the advantages or disadvantages which he may derive from 
them. Thus a considerable number of species are proper to 
supply him with food; the sepia, and especially the calmar, 
or ink-fish, are in great request in Greece, and even in seve- 
ral parts of Italy ; the larger species of snails, many buccine, 
and some cognate genera, are in tolerable estimation in several 
countries, and were so much so among the ancient Romans, 
that Pliny has not disdained to recount the names of those 
who thought proper to collect them in depéts, and to provide 
them with abundant nourishment, to fatten them, and render 
them more succulent. Oysters and muscles also constitute a 
prime object of commercial speculation in our own days. 
Although not very numerous, the advantages which the 
mollusea present to us are nevertheless much greater than 
the injuries we receive from them ; and it is probable that we 
cannot stigmatize among them an animal truly hurtful, except 
the teredo (ship-worm), which, attacking the wood of our 
vessels and dikes, often occasions very considerable mis- 
chief. The knowledge, therefore, of its habits and manners, 
is of the first necessity in those countries which are infected 
by it. Slugs and snails are also strongly and justly dreaded 
enemies in our gardens. 
It may neither be unuseful nor uninteresting to give a brief 
sketch here of the history of this part of zoology. 
All the ancient authors, such as Aristotle, Pliny, and their 
abridgers, appear to have been very little acquainted with 
these animals: they place them among those which they 
