Ii6 Pearls. 



found here, bound together like a cluster of grapes, 

 showing that even within this muscle these Pearls 

 receive further accretions. In course of time such 

 Pearls as avoid passing into this muscle find their 

 way downwards to the lowest part of the oyster, 

 and according to their position therein, may or may 

 not find their way out of the tissues of the oyster 

 into the shell. 



Up to this time the Pearl has received regular 

 layers all over its surface, but rings, and other 

 marks of lesser brightness frequently occur, the 

 result probably, of contact with the coarser tissues 

 of the oyster. For a short time the Pearl is loose 

 in the shell, and it falls into the same category as a 

 stone, or any other intruder. It is encircled by the 

 growing layer of shell, and proceeds on its down- 

 ward course through the shell, like an ordinary 

 *' blister," the upper portion receiving further layers, 

 until it is hidden beneath the shell which by 

 degrees, resumes its natural shape. This process 

 is well illustrated by Figs. 2 and 3, p. 95. 



The shell, as stated in the last chapter, is 

 worn away from the outside at the same rate 

 that it is renewed within, so that in time, the Pearl 

 with its surrounding tomb yields to the general 



