92 



The Pearl Oyster of Ceylon, [no. o, new serie?, 



On removing the animal from the shell, the whole of the internal 

 part is seen enveloped in a membrano-muscular covering, called the 

 M mantle" and known popularly in Ceylon as the "skin." The free 

 border of the mantle lining each valve, dips downwards, to meet 

 with a similar veil on the opposite side ; thus forming a kind of dou- 

 ble fringed veil. The one set of tentacular fringe, in immediate con- 

 tact with the shell, is composed of hairy tentacles, looking horizon- 

 tally forwards ; the other, about three-eighths of an inch apart from 

 the former, and lining the edge of the mantle, from side to side, 

 looks downward, 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 filamen- 

 tous 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 dis- 

 tributed 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 approach to the aquarium of a lighted candle, or 

 even the approach of a hand, or the shadow of a person, near the 

 glass sides of a vessel in which it is confined. I should not, in a 

 popular Report, advert to this physiological subject, but that the 

 senses of the Oyster have a great deal to do with its habits, not only 

 in the aquarium, but also in its native bed. "Were it not for these 

 delicate fringes surrounding the mantle, the softer parts of the 

 Ovster would easily become the food of a host of carnivorous 

 creatures abounding in the sea; and many more Pearls would 

 drop out of the shell, than do now with such sentinels at the en- 

 trance of its external rim. The mantle is the only organ the ani- 

 mal has for the formation of the shell. The increase of the lateral 

 dimensions of which, and the formation of the pearly nacre, and 

 the Pearls, depending upon the condition of this important invest- 

 ment. If it is injured, the pearly matter is not secreted in such 

 abundance over the shell, or if by some cause it becomes retracted 



