Pearls & parasites / by Arthur E. Shipley.

  • Arthur Shipley
Date:
1908
Catalogue details

Licence: In copyright

Credit: Pearls & parasites / by Arthur E. Shipley. Source: Wellcome Collection.

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    which feeds largely on oysters, the cestodes exist in swarms in the stomach, and the eggs make their way from the fish into the oysters, and there some of them grow up, but most of them perish in their pearly casket. If, as I believe, this is the history of the pearl-forming organism, we must regard the Rhinoptera as a friend to the industry, and not, as hitherto, an enemy which helps to destroy the oyster-beds. The discovery of the cestode larva as a real cause of pearl-formation received an interesting confirmation shortly after it had made it. M. G. Seurat, working independently at Rikitea on the island of Mangareva, in the Gambier group, discovered a very similar larva in the local pearl-oyster around which pearls are formed; this larva, if we may judge from pictures, is almost certainly the same as the one from Ceylon. Professor Giard regards it as belonging to a tape- worm of the genus Acrobothrium ; and, if he be right, then Professor Herdman’s larva is an Acrobothrium too. We have so little knowledge of the early forms of cestodes that we cannot accept this attribution as final. We may, however, hope for further informa- tion, for a French zoologist, M. Boutan, started some little time ago for the East to work at the problem; Mr. Hornell is still at work in Ceylon; and Mr. C. Crossland, who has had much experience in marine work in the tropics, has been appointed, at the request of the Soudan Government, to investigate the pearl- oyster beds of the Red Sea. Finally Dr. Willey, of the Colombo Museum, has recently described similar larvae in the pearls of the 1 window-pane ’ oyster, Placuna placenta) from the eastern shores of Ceylon. In 1904 it was again found possible to hold a fishery in Ceylon. It was held at a place called Marichikaddi, also on the north-west coast. In the course of thirty- eight days over 41,000,000 oysters were taken. The trade was very brisk; the prices paid were un-
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