86 POPULAR BRITISH CONCHOLOGY. 



far short of the above in poetry^ as our pearls are of the 

 beauty of oriental specimens in beauty ; — 



But yet the glittering dew-drop drawn 

 From shores or streams of British Isles, 

 With flowers of heartsease might be worn, 

 And lustre give to beauty's smiles. 

 No luckless diver's heaving breast 

 For useless ornament ojipress'd, 

 But cheerful labour, free from pain. 

 Has sought the prize for honest gain. 



All kinds of mollusca whose shells are lined with pearly 

 coatingj are apt to produce pearls under some condition. The 

 coating of the shell of pearl- oyster^ for instance, is thick and 

 iridescent; it is usually called "mother-of-pearl/* and pro- 

 duces its offspring thus : — if any little bit of sand gets in- 

 truded within the mantle, it causes such irritation to the 

 animal that an extra quantity of the nacreous secretion is 

 exuded suddenly in or near the spot surrounding the object. 

 If the latter be not removed, it will form the nucleus of 

 many layers of the secretion, successively hardening round it, 

 and so will become a jewel. If the shell is closely attached 

 to its bed, the pearl will remain fixed to the surface ; but if 

 it be "riding at anchor,** attached only by the long hairs of 

 its byssus, the oyster will roll about, and contrive to shake 



