THE PEARL OYSTER OP CEYLON. - 167 



found in this bed are of more than one age. The oysters whose growth 

 has been stunted have very different characters ; their shells are thick, and 

 there is not the same length of pliable edge which young oysters have ; 

 the adductor muscle and other parts of the oyster bear also the marks of 

 age. The muscle is hard and stouter, in the adult, and further removed 

 from the hinge ; the foot is firmer and more speckled, and the groove under 

 the foot is irregular ; the liver cuts firmer, and the nacreous part of the 

 shell has a thick edge in the adult oyster. The fact that good pearls are 

 also found in these second-sized oysters, does not show that they are as old 

 as the larger ones. There are other cases which doubtless come into 

 operation here, part of which only can, in this second stage of my inquiry, 

 be demonstrated. The presence of a worm (a species of filaria) found in 

 the oysters, has, I am positive, much to do with the formation of pearls. 

 I would rather reserve this part of my investigation for longer experience- 

 But this much I can say at present, with perfect safety, that whenever I 

 found good pearls in a batch of oysters, I found this worm and its eggs in 

 large numbers in the liver, ovary, mantle, and other parts of the oyster. 

 My researches here have quite proved to me, and will also prove to others, 

 Avho will carefully and without prejudice examine for themselves, that the 

 ova of oysters and the ova of worms form the nuclei of many pearls found 

 in the soft parts of the animal, and that sand, portions of sea- weed, larva of 

 insects, &c, form the nuclei of the shell pearls, or pearls attached to the 

 shell. I have specimens demonstrating this even to the naked eye. 



It was the celebrated Sir Everard Home who, I believe, first started the 

 doctrine of eggs being the nuclei of pearls. But this theory has been con- 

 tradicted by other writers. I have, however, in my report of last year, 

 stated how escaped ova could readily form such nuclei ; and now I have 

 the pleasure of announcing to the scientific world, that I found the ovaries 

 of a pearl oyster filled with pearls of various size and shape. I have pre- 

 served the specimen for transmission to Professor Owen, to be by him 

 placed on the shelves of the Museum of the Royal College of Surgeons, as 

 a proof of the accuracy of the late Sir Everard Home's doctrine, which has 

 for many years been exploded. I obtained from one of the ovaries as many 

 as thirty-two pearls, and the other egg bag, still unopened, seems to con- 

 tain as many more. 



It will now, indeed, be a curious question, where the pearly matter 

 forming the pearl found in the ovaries was derived from. Sections of these 

 pearls show the same form of nuclei as pearls found in some parts of the 

 mantle ; and the large irregular ones have more than one such nucleus. 

 The mantle was found adhering to the ovaries as if it was the residt of 

 adhesive inflammation. And, as the mantle is acknowledged to be the 

 secreting organ of pearly matter, could this matter have been introduced 

 into the ovation ? or is it likely that other parts of the oysters, such as the 

 walls of the ovaries, occasionally secrete pearly matter under abnormal 

 circumstances ? It will be premature now to decide upon this interesting 

 physiological subject. 



