RECREATIVE NATURAL HISTORY. 



158 



variety of tho unio (17. roittyi) was found to prodaoe a very 



iuli. The rivor flowing noar Braddon 

 .1. 'l'!i.' ri-..-r Conway, in 



.\urtli . "-oil known to bo ono of tho chosen 



hornet) I'oth tho Halt-water mussol at tho 



mouth, u:l t!i uniu high up auiun.,' tho brawling rills 



Is and yellow furzo blossom, bear 



witli tin in ever and anon tho inuuh-oovotod troaauro. Bottws- 



o tradition says, tho honour of being tho locality near 



the l>old and handsome Welah noblouian, Sir I. 



. ol'tuiiu-il tin- rioh and costly pearl which ho presented 



to tin- <}'.: .'ii of Charles II. Tho term "Cretin diluw" has boon 



by tho \\Yl.-h given to tho Conway shells from an idea, which 



they appear to have entertained, that they were brought to tho 



river at tho time of tho deluge. The formation of pearls in tho 



appear* no reason why they should not be found as abundantly 

 as when Sir Robert Bedding wrote : speaking of the proportion 

 of prizes to blanks, be says, " Although, by common estimate, 

 not above ono shell in a hundred may hare a pearl, and of theao 

 pearls not above ono in a hundred bo tolerably clear. Yet a 

 vast number of fair merchantable pearls, and too good for the 

 apothecary, are offered for sale by these people every summer 

 assize." 



Tho streams of Bavaria at the present day produce from 

 time to time pearls well worth obtaining, and about thirty 

 years since a most important find of them was made by mere 

 chance in Norway. An unusually dry summer had caused the 

 waters of the Zeddern Channel to become nearly dry. A 

 peasant who chanced to be wandering about over the shingle 

 and pebbles, seeing a dead and partially dried unio laying in it* 



L LTJOTEA STAGNALIS. 2. TRITON. 3. HELIX HEMASTOMA. 

 SILK MUSSEL). 6. UNIO MABGAHITIFERUS (THE FBESH-WATER 

 8. ADONTA (1'OND MUSSEL). 



4. Mrnrrs EDUXIS (THE EDIBLE MUSSEL). 5. PIJTXA NOBILIS (THE 

 PEARL SHELL). 7. DAMAOED SHELL REPAIRED BY PEARLY DEPOSIT. 



tissues of this or any other mollusk can be only viewed in the 

 light of a diseased or abnormal secretion, caused in the majority 

 of cases by the presence of some foreign and irritating cause. 

 Linnoms discovered by actual experiment that grains of sharp 

 Band introduced between tho valves of tho shell in such a way 

 that they rested between the body of tho animal and tho 

 " mother-of-pearl," or shell-lining, caused in a short time the 

 deposition of a coating or crust of pearl on tho sand grain, 

 which, acting as a nucleus, gathered tho shielding matter 

 around it, and so guarded the delicate tissues of tho mollusk 

 from friction and injury. It has also been found that by 

 drilling a small hole through the outer coatings of the shell, 

 and leaving tho lining untouched by tho boring instrument, 

 that a pearl nodule was in a short time formed, as shown in the 

 annexed illustration (Fig. 7), so as to defend the weak point, just 

 as a skilful armourer would patch a weak place in breast or back 

 plate. It is somewhat remarkable that the search for home 

 pearls should be MO larely followed at the present day, as there 



wide-spread shell, stopped, and picked it up, when, much to his 

 wonder and delight, out rolled a pearl worth ,50. Specimens 

 of even greater value than this were soon after discovered by tho 

 people, who rushed from far and noar to tho treasure-yielding 

 sands, which were thoroughly searched until the return of the 

 water to its accustomed level put a stop to tho search. A shell 

 closely resembling the Unio margaritifenu is to be found in 

 most of the ponds, brooks, and rivers of England ; it is known 

 as the " pond mussel," or Adonta. A reference to Fig. 8 will at 

 once show the particulars of external form in which the two shells 

 differ. The Adonta, so far as we have observed, yields no pearls, 

 but produces an incredible number of young adontas, which ate 

 carried within the parent shell completely valved and ready to 

 shift for themselves when cast on the world of waters. It is 

 said that an American naturalist has succeeded in computing 

 ono Adonta family at 600,000 in number. There are many more 

 shell-dwellers interesting in habits and curious in form, and to 

 those we hope to refer in another paper- 



