I lo Pearls. 



experience is, that a nucleus is always to be found. 

 On the other hand the pearlers in the North West 

 of Australia, state, that most of the Pearls broken 

 there have presented a small golden-coloured cavity 

 capable of holding a No. 8 shot. The experience 

 of these pearlers on the general subject, however, is 

 much inferior to that of the jeweller. 



The nucleus of the Pearl may be either a 

 grain of sand, or the frustule of one of those 

 minute siliceous vegetables known as diatoms^ or 

 a minute parasite, or even one of the ova of the 

 Pearl oyster itself. Around this foreign body thin 

 layers of nacre are deposited, one after another, like 

 the successive skins of an onion, until the object 

 is completely encysted. The Pearl is formed of 

 concentric layers of carbonate of lime, of extreme 

 tenuity, but of the same general character as those 

 composing the shell. 



Sir Everard Home, a distinguished surgeon in 

 the early part of this century, having been led to 

 study the structure of Pearls, came to the following 

 conclusion : " A Pearl is formed upon the external 

 surface of an ovum, which having been blighted, 

 does not pass with the others into the oviduct, but 

 remains attached to its pedicle in the ovarium, and 

 in the following season, receives a coat of nacre at 

 the same time that the internal surface of the shell 



