Their origin and formation. 1 1 3 



mind. Blister Pearls are generally hollow nacreous 

 bodies, of irregular shape, and are often due to the 

 deposition of nacre at some point where the shell 

 has been attacked by a parasite from without. 



That the oyster does not work magic may be 

 taken for granted, and the following explanation of 

 the vexed question of the formation of Pearls is 

 now submitted to practical pearlers and conchologists. 

 The principle involved is applicable to all molluscs, 

 but due consideration in each case must be given to 

 the natural position of the shell, and its owner's 

 habits. 



The oyster lies at the bottom of the sea at an 



angle more or less considerable, but is generally 



inclined to the sea bottom at about 20** to 25°. The 



shell is usually open about \\ inches, to admit the 



entrance of water, its owner's natural sustenance, 



and the mantle is spread out over the horny outside 



lips of the shell. Respiration is carried on by means 



of the gills, and any organic particles in the water 



which bathes these vascular organs are transferred 



to the mouth. Scientists have taught us that 



" haemoglobin," or the colouring matter of the blood 



in the animal kingdom, is the agent, that owing to 



its great affinity for oxygen, extracts that supporter 



of life from the air inhaled. Of the agent that 



H 



