V] PEARLS 59 



removing the outer layers, if they are bad. There is 

 a great element of chance in the process, because one 

 never knows whether the deeper layers will be better 

 or worse, and each layer removed reduces the size 

 and value of the pearl. 



Fig. 7. Section of nacreous pearl, really composed of two fused 



pearls. Note the nuclei of Hypostracum and the concentric 



dark layers of Periostracum. (From Eubbel.) 



In any case the external appearance of a pearl 

 gives no clue to its internal structure, and the reason 

 for this follows from the description of the structure 

 given above. 



There is some little difference between the nuclei 

 of pearls. Thus the pearls from the common edible 



