probably
considerably greater, since the facilities of transport by rail
greatly increase the inland consumption of these as of other marine
luxuries. French naturalists report, that before an oyster is
qualified to appear in Paris, he must undergo a course of education in
discretion; for the artificial oyster-beds on the French coast, where
the animals are stored to be carried away as required, are constructed
between tide-marks; and their denizens, accustomed to pass the greater
part of the twenty-four hours beneath the water, open their valves and
gape when so situated, but close them firmly when they are exposed by
the recession of the tide. Habituated to these alternations of
immersion and exposure, the practice of opening and closing their
valves at regular intervals becomes natural to them, and would be
persisted in to their certain destruction, on their arrival in Paris,
were they not ingeniously trained so as to avert the evil. Each batch
of oysters intended to make the journey to the capital, is subjected
to a preliminary exercise in keeping the shell closed at other hours
than when the tide is out; until at length the shell-fish have learned
by experience that it is necessary to do so whenever they are
uncovered by sea-water. Thus they are enabled to enter the metropolis
of France as polished oysters ought to do, not gaping like astounded
rustics. A London oyster-man can tell the ages of his flock to a
nicety. They are in perfection when from five to seven years old. The
age of an oyster is not to be found out by looking into its mouth; it
bears its years upon its back. Everybody who has handled an
oyster-shell must have observed that it seemed as if composed of
successive layers or plates overlapping each other. These are
technically termed 'shoots,' and each of them marks a year's growth;
so that, by counting them, we can determine at a glance the year when
the creature came into the world. Up to the epoch of its maturity, the
shoots are regular and successive; but after that time they become
irregular, and are piled one over the other, so that the shell becomes
more and more thickened and bulky. Judging from the great thickness to
which some oyster-shells have attained, this mollusc is capable, if
left to its natural changes and unmolested, of attaining a patriarchal
longevity. Among fossil oysters, specimens are found occasionally of
enormous thickness; and the amount of time that has passed between the