THE OYSTER. 21 



SO that each new layer is a little larger in area than 

 the last one. The soft mantle readily conforms to the 

 shape of the body to which the oyster is fastened, 

 and however irregular this maybe, the new shell takes 

 its shape and closely adheres to it, because the new 

 deposits are laid down directly upon it. 



You will see from this account the error of the 

 current belief that an old oyster cannot fasten itself. 

 Since the adhesion takes place around the growing 

 edge, an oyster may fasten itself at any time, and 

 clusters of oysters are often found with their shells * 

 soldered together near their tips. This can of course 

 only occur after they are well grown. 



Oysters are able to close up broken places in their 

 shells, and most molluscs sometimes absorb and rebuild 

 parts of the shell. If any foreign body gets in between 

 the shell and the mantle, shelly matter is deposited 

 upon it. The pearls of the pearl oyster are formed in 

 this way. Some small particle, such as a grain of 

 sand, works its way in, and forms a nucleus which is 

 gradually covered by layer after layer of pearl. The 

 brilliant lustre, as well as that of mother-of-pearl, 

 which is nothing but polished shell, is due to the 

 interference of light caused by the laminated structure. 



It is said that the Chinese manufacture pearls, or 

 rather make the pearl oyster do the work for them, by 

 inserting between the shell and the mantle strings of 

 small shot. Did you ever see one of the sacred clam 

 shells which the Chinese Buddhists believe to have a 

 miraculous origin ? They are often found in collec- 

 tions. The inside of the shell has a beautiful pearl lustre, 

 and along it is a row of litde fat images of Buddha, 



