Page:A Lady's Cruise in a French Man-of-War.djvu/293

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calculate that by hiring divers and working the beds themselves, the shell can be raised at less than £6 per ton. In former years the annual harvest of Paumotu pearl-shell was immensely in excess of the present supply, which is said not to average above 200 tons—the natural result of allowing the beds no time to recruit. Doubtless there are vast beds untouched, at lower levels, where the divers do not care to venture; and it is supposed that the outer face of the barrier-reef is probably one vast oyster-bed, but the bravest divers dare not venture to attempt work beneath the awful breakers.

Certain it is, that the colonies in the lagoons are annually replenished by myriads of infant pearl-oysters, which have been spawned in the deep sea, and which, in the months of December and March, may be seen floating in with the rising tide; tiny glittering shells, a quarter or a half inch in diameter, like fairy coins. Once in those calm waters, the young oysters apparently have no wish again to seek the stormy outer seas, for they are never seen floating out with the retiring tide. It takes seven years for an oyster to attain maturity, so only those which settle in deep water have a chance of reaching a ripe age.

Strange to say, these creatures, which appear to be so immovably attached to their coral-rock, are proved to be migratory. Not only do the closely packed young oysters detach their silken cables and move off in search of more roomy quarters, but even the heavy grown-up shells sometimes travel from one shelf in the coral to another, probably in search of better feeding-grounds. They are singularly capricious in the selection of their homes; in one lagoon they are abundant, and perhaps in the very next not an oyster is to be found: and no attempt to raise artificial beds, even by transporting masses of rock covered with young shells, has ever succeeded, although the surroundings are apparently identical in every respect. Of course they will not settle anywhere near sand, which, by any disturbing cause, might enter their shells, and cause them as much inconvenience as do the innumerable tiny red crabs,—uninvited guests, which take up their quarters in the oyster-shells, to the great aggravation of the helpless owners.