594. APPExNDIX 



paid for lie unused and depreciating in value. Mobius states that in his time (the end of the 

 ■■fifties) a string of from seventy to eighty three-carat pearls was worth from 4000 to 6000 

 thaler, that is to say, about 70 thaler (old German thaler = 3s.) for each pearl. This was 

 approximately twice the price curi-ent at that time for a single pearl of the same size and 

 quality. 



In conclusion, it will be interesting to note the value of some of the more fan)ous 

 pearls. That in the Hope Collection was valued at ^12,500. At the valuation made 

 in 1793 of the French Crown jewels, a round maiden-pearl weighing 27t^ carats, and of 

 magnificent lusti'e, was valued at 200,000 francs (,£8000) ; while 300,000 francs was the 

 value attached to two well-formed, pear-shaped pearls of very beautiful " water " which 

 together weighed 51\^ carats ; and 60,000 francs to four differently shaped pearls the 

 combined weight of which was 164<^ carats. Another pear-shaped pearl weighing SBff 

 carats, and therefore much larger than the one first mentioned, was valued at 12,000 francs 

 only, on account of its being flat upon one side. At the International Fishery Exhibition 

 held at Berlin in 1880, the Berlin jewellers exhibited a string of yellowish Indian pearls 

 worth d£'4000, a string of white pearls from Panama which cost ^£"5000, and a string of black 

 pearls from the Pacific Ocean which was valued at ^^6000. The value attached to the 

 " Great Southern Cross '' pearl found off the north-west coast of Western Australia in 1886 is 

 £10,000. 



PEABL-PISHING. — Though as we have seen there are many molluscs which 

 occasionally produce pearls, there are only two species which produce these objects in numbers 

 sufficient to make the systematic collection of them a profitable industry. By far the more 

 important of the two is the marine pearl-oyster Meleagrina { = Avicula) margaritifera,v/\nc\i 

 inhabits the warm seas of many tropical regions. The other and less important mollusc is 

 the fresh-water pearl-mussel Unio { = Margaritana. =Alasmodon) margaritifer, and a few 

 near relations inhabiting the streams of northern regions, or, at any rate, of extra- 

 tropical countries. By far the largest number of pearls, and those also of the finest quality, 

 are, and have always been, obtained from the pearl-oyster, which in addition supplies the 

 bulk of the mother-of-pearl for industrial purposes. Only a small number of pearls, 

 generally of poor quality, are obtained from the pearl-mussel. 



The Peai-l- Oyster. — According to the opinion of the majority of conchologists the 

 salt-water pearl-forming molluscs from almost all regions of the world belong to one and 

 the same species. Individuals from different regions do, indeed, show differences in the size 

 and thickness of the shell, in the roughness of the exterior, the colouring of the inner 

 surface, &c., but these differences are not of specific importance. A small, thin-shelled form 

 from which no mother-of-pearl is profitably obtained is sometimes distinguished from the 

 large thick-shelled Meleagrina margaritifer a by the name Avlcula margaritifera, but there 

 are many transitional forms between the two, so that they cannot be sharply separated. 



The pearl-oyster, like the common oyster, lives with large numbers of its fellows, 

 forming the so-called oyster-banks. These lie usually from 3 to 5 fathoms, occasionally from 

 6 to 10 fathoms below the surface of the water, rarely any deeper. The bank has a foundation 

 of calcareous material ; very often, indeed, it is built on a coral-reef. The molluscs are not 

 free but attach themselves firmly to any suitable object by means of the beard, or byssus, a 

 bundle of tough horny threads, which reach the exterior through a hole in the hinge line of 

 the shell. The pearl-oyster banks are inhabited also by corals, univalve molluscs, and many 

 other marine animals ; the temperature of the water in which the whole community lives is 

 never much below 25° C. (= 77° F.). 



The pearl-oysters are brought up from the sea-bottom by divers, who descend into the 



