272 INTRODUCTION TO CONCHOLOGY. 



ralists, till the year 1717, when M. Eeaumur, in a curious 

 paper which appeared in the Memoirs of the Trench 

 Academy, on the structure of both shells and pearls, con- 

 jectured with great probability (and his notions are now 

 generally admitted), that pearls are formed of a juice extra- 

 vasated out of some ruptured vessels, and detained, and 

 fixed, among the membranes of the mollusk. 



To evince the probability of this ingenious supposition, 

 he shows that oceanic and river shells are formed wholly of 

 a glutinous and stony matter, which oozes from the body 

 of the inhabiting mollusk, and that, consequently, an 

 animal famished with vessels fraught with a sufficient 

 quantity of stony juice to build, thicken, and extend a shell, 

 is fully capable of forming pearl, if the juices designed for 

 the increase of its habitation should chance to overflow 

 among the membranes, or to fill up any accidental cavity in 

 the animal himself. 



In proof of which, he has further shown, that when 

 pearls of two colours are discovered in the pearl-mussel 

 of Provence, the tints of each are precisely the same 

 with those of the shell, and that each kind of coloured 

 pearl is found in the corresponding coloured part of the 

 shell; thus clearly evincing that where the transpiration 



