28o 



Marvels of the Universe 



PEARLS AND PEARL OYSTERS 



BY CHARLES DE BOISMAISON. 



When the Pearl Oyster was ver}' young, it left the parental mantle and floated along, a mere film, 

 on the ebb and flow of the tide. Each day it grew a little bigger, a little heavier, a little more 

 important, while its increasing size protected it more and more from the voracious appetites 

 of one or other species of the innumerable hosts of marine life that lie in wait for such minute 

 organisms. As it grew in bulk and weight, it became less active, till at last it sank upon " the ooze 

 and bottom of the sea " and fastened itself by its beard, which grew near the hinge imiting its 

 shells, to the most convenient rock that chanced to project from the gravelly soil. There it grew 

 still larger, still heavier, still more important, opening its two shells to let the water flow in, for the 

 water carried the minute life which nourished it ; and so a year or two passed by. One day- a micro- 

 scopical creature ventured too near these open doors and was swept in by the current, but not near 

 the expectant mouth. It was caught in the tentacle-fringed mantle that was moving with a gentle 

 undulation along the lip of the shell. This very movement carried it still further into the mantle 

 of the oyster, and caused the tiny victim to break the filmy skin that envelops the edge of this 

 mantle and carry a fragment with it into the interior of the expectant oyster. Now is the biter 

 bit. The oyster cannot swallow his disappointing visitor, for that visitor is nowhere within reach 

 of his mouth ; and while he is himself denied the expectant feast, the little creature who was to 

 form that feast is causing intense irritation to his nervous system. Time, however, and his own 

 constitution help to ease him of his annoying intruder. His nervous disorder causes him to secrete 

 the delicate film with which he has lined his shell and which has hardened into mother-o'-pearl. 



I'hol,, I,;] 



IHE PEARL OYSTER'S SHELL. 



The open shell of the Pearl Oyster after the death of the animal, showing a large pearl. This was probably formed in a 

 free condition and globular in form, but afterwards became attached to the shell. 



