MTt. It. GATINEH ON BTtTTTSTI PEATILS. 



427 



not positively affirm that in that bivalve, or, indeed, in Vnio or 

 Anodon, the pearls arise from the same exciting cause, although in 

 the last two genera we have found them together. We are not 

 certain what is the early life-history of the distomes ; but in Vnio 

 the foot is sometimes found distended with capsules or mother 

 cells, each one containing several distomes. 



The above account of the matter the writer gave at one of the 

 Meetings of the British Association, at least the principal facts ; 

 and he is not aware that it has ever been contravened. He would 

 now proceed a little further in the subject, with a utilitarian aim. 



Attempts have been made to force the mollusks to produce 

 these pearls at the will of the experimenters. And, first, might 

 not the Alasmodon of our rivers be cultivated like the salmon, so 

 as to become more plentiful and possibly more entitled to its 

 name marqaritiferus? — many gravelly and rapid streams (the Dove, 

 for instance, in its upper course) being apparently well suited for 

 it, and having neither this species nor any of its representatives. 

 Secondly, it has been supposed that a morbid state of the animal 

 is more favourable to the production of pearls, or, in our view, 

 more favourable to the generation of the distomes ; and could not 

 that be brought about by a transfer, or some such contamination 

 of the water as the Chinese are said to practice? Thirdly, could 

 not the Alasmodon be forced to form pearls by carefully introdu- 

 cing foreign bodies between the mantle and the shell, not as 

 Linna3us is said to have done, by breaking or boring the shells, but 

 by prizing them a little open and so introducing such bodies ? 

 The people just alluded to, we should suppose, so introduced the 

 metallic or shelly nuclei, thus producing the well-known pearly 

 excrescences resembling Buddha, as w r ell as large pearls. "We 

 have had no opportunity of operating on the TInio or Alasmodon, 

 though they may be kept alive for a long time under a tap ; 

 but we have made a few trials on the common Anodon, and 

 present the specimens. Our plan was to prize open the valves 

 a little, separate the mantle from the valves, and then intro- 

 duce several pearls from the common Mytilus, in the hope that 

 they would become coated with a layer of brighter nacre. In 

 two months the pearls had become adherent to the shells — and in 

 three, more or less increased by coats of nacre. As I before said, 

 with the true British pearl-mussel I have not been able to make 

 the trial. Reaumur and Linnseus seem to have failed with ex- 

 periments of this kind ; but other trials might be more successful, 



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