94 



The Pearl Oyster ( f Ceylon, [so. 5, new series 



immediate part of the animal through which the ova found their 

 exit ; and I have not been able to detect a regular oviduct. The 

 ovaria, when distended with ova, cover nearly the whole of the 

 stomach, heart, and liver, and project even on the conical csecal 

 process of the stomach, and also on the base of the foot. The sto- 

 mach is very small, placed in the centre of the liver : the oesophagus 

 is very narrow, scarcely admitting a moderate sized probe : it is 

 about 3 lines long. The mouth situated near the hinge, behind the 

 foot and byssus, is a horizontal slit, of about 3 lines in length, in 

 the duplicature of the lower pair of labial palps. These palps are 

 large, broad, truncated anteriorly, and rounded on the sides ; the 

 inner surface plaited, or rather grooved. The sense of feeling, or 

 touch, is no doubt by this rugose structure, greatly increased. The 

 palps serve the animal as organs of touch, if not of taste ; they also 

 serve to collect food, and give the animal the power of rejecting in- 

 digestible particles of matter, or such substances as jmight prove 

 injurious. 



I have, through the Microscope, ascertained the kind of food Pearl 

 Oysters live on. This consists of minute algae or weeds, animal- 

 cules and shells, called Foraminifera. Diatoms also, those minute 

 vegetables forms which can scarcely be detected with the naked eye, 

 are found growing oji the external surface of the shell; where a 

 host of infusorial and microsopical objects likewise find a pasturage. 

 So that the Oyster may be said to carry on its back, the food upon 

 which it lives. The siliceous internal skeletons of these Diatoms, 

 I have detected in the excrementitious matter of t the Oyster. It 

 will be a subject for future inquiry, whether any of these sharp- 

 t pointed skeletons do not permeate the coats of the mantle, and thus 

 become nuclei of Pearls. I have, on examination of " seeding" 

 pearls found the skeleton of a Xavicula, (species of Diatom) among 

 the ova; but whether this proceeded from the stomach of the ani- 

 mal, or got there by passing under the mantle, it was not possible 

 for me to determine. 



The Pearl Oyster, like other Bivalves, (Conchiferae) are Mo- 

 noecious, or rather hermaphrodites ; though, properly speaking, 

 they can neither be said to belong to one or two sexes, for, with the 

 exception of the presence of ovaria (or egg bags,) no other sexual 



