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production and formation of pearls. 
the publisher, desiring to know the ground on which the 
author had made that assertion. 
“ As to the authority I have to assert such an origin of 
pearls, I here declare that a certain Dane, called Henricus 
Arnoldi, an ingenious and veracious person, having by his 
own experience found it so in Christiana, in Norway, with 
great seriousness assured me of the truth thereof." 
PLATE XIII. 
No. l. Afresh water muscle, one shell removed, of the 
natural size. 
The lining, with its attachment to the shell on which it 
lies, also the loose fringe upon its edge. 
A portion of the foot exposed between the linings of the 
two shells. 
A portion of the oviduct also exposed. 
The lining detached from the shell removed. 
The two muscles cut through which united the shells. 
A cluster of small pearls lying on the outer surface of the 
ovarium, close to the liver. 
No. 2. The above pearls magnified three diameters, firmly 
attached to the membrane on which they lie. 
No. 3. A pearl bursting the bag in which the ovum was 
formed ; five diameters. 
No. 4. A pearl escaped from the bag ; five diameteis. 
No. 5. Section of No. 4 ; ten diameters. 
No. 6 . Section of oriental pearl ; ten diameters. 
MDCCCXXVI. 
Yy 
