82 Drs. Kelaart and Mobius on the Natural History of the 



the natural history of the Pearl Oyster, and we have now before 

 us that gentleman's first report upon the subject. His investi- 

 gations were carried on by keeping the animals partly in 

 tubs and other vessels, partly in perforated wooden boxes and 

 old canoes sunk at various depths in the sea, and partly in 

 aquaria with glass fronis, to the usefulness of which in facili- 

 tating observations Dr. K jlaart bears strong testimony ; and he 

 also, apparently unexpectedly, obtained great "facilities of ob- 

 servation amongst the small beds of oysters found in the inner 

 harbour of Trincomalee. They are found of all ages and sizes, 

 at various depths and on different kinds of banks ; so that," adds 

 Dr. Kelaart, "no naturalist has perhaps ever had the same 

 opportunities of observing the habits of the Pearly mollusk as I 

 have at present." 



The Ceylonese Pearl Oyster is the Mytilus margaritiferus, 

 Linn., the Meleagrina margaritifera of Lamarck, which appears 

 to be common to all the shores of the Indian and Pacific Oceans, 

 from the Red Sea and the east coast of Africa in the west, to 

 California, Panama and Chili in the east. The Ceylonese shells 

 belong to that variety of the species described by Leach under 

 the name of Avicula radiata ; indeed, Templeton seems inclined 

 to regard it as a distinct species. On the other side of the 

 Isthmus of Panama, in the Gulf of Mexico, and wherever Pearl 

 Oysters occur on the west coast of America, the species appears 

 to be the Avicula squamulosa, Lamk. The anatomy of the animal 

 is described by Dr. Kelaart as follows : — 



" The free border of the mantle lining each valve dips down- 

 wards to meet a similar veil on the opposite side, thus forming 

 a kind of double-fringed veil. The one set of tentacular fringe, 

 in immediate contact with the shell, is composed of hairy ten- 

 tacles, looking horizontally forwards ; the other, about fths of 

 an inch apart from the former, and lining the edge of the mantle 

 from side to side, looks downwards, and dovetails with the 

 tentacles of the opposite flap of the mantle. These tentacles 

 consist of a series of long and short flat filaments — the long 

 ones having lateral filamentous projections. The tentacles are 

 exceedingly sensitive; and one would almost give them the 

 power of seeing ; for not only the touch of a feather, but the 

 approach of one, when the animal is lively and in good health, 

 makes them draw forwards, and perfectly shut out the intruder. 

 As these molluscs have no organ of sight, I have no doubt that 

 the delicate nerves which are distributed through the mantle 

 and its tentacular processes, possess in some degree the sense 

 answering to vision in other animals, as well as of touch ; for 

 an oyster will be observed rapidly to close its valves on the ap- 

 proach to the aquarium of a lighted candle, or even the approach 



