Pvn H,i I'UitlS

OSTREA. 41
bygone epochs, they were not so well off as we are for
the quality of this gastronomic luxury. Oysters seem
to have been as much sought for and enjoyed in the
" stone " age as they are at present, judging from the
vast heaps of large empty shells which are found in the
Danish kjokkenmoddings, as well as in the northern
parts
of the British isles.
Lister was the first to describe the anatomy of the
oyster, from particulars which were communicated to
him by Dr. Willis. This description is tolerably accu-
rate; and if the authority could be wholly relied on,
these mollusks ought not to suffer the discredit of being
so stupid as is proverbially alleged in Norway and
Brittanv. Willis states that when the tide comes iu
they lie with their hollow shells downwards, and when
it goes out they turn on the other side; and he adds
that they do not remove from their places, unless in
cold weather to cover themselves with the ooze ! Lister
appears to have trusted too much to his friend, and not
to have learnt for himself the fact that ovsters have
at
not the slightest power of locomotion, except
in their
embryonic state. Bishop Sprat's account of our oysterfisheries,
which has been so often quoted in works on
natural history, was chiefly compiled from this com-
munication of Dr. Willis. The " spat/'
said to be like
a drop of candle- grease, is a pure fiction. From April
to July the ova are continuallv excluded from the ovary
and discharged into the gills, where they are hatched.
Every batch of fry
in succession is then committed to
the sea ; and the young commence life as free animals,
like other bivalves, swimming or rather flitting about
with considerable rapidity by means of numerous cilia
which fringe their circumference. Each is enclosed in
an extremely thin and prismatic semiglobular bivalve