4 CEYLON PEARL OYSTER REPORT. 



natural pear] is an inorganic particle. This " grain-of-sand " theory was supported by 

 Redi and many other early and also more recent Naturalists, and it is the view which 

 has been most generally adopted in the text books, and perhaps we may add in 

 educated public opinion, as expressed, for example, in Sir Edwin Arnold's lines : 



" Know you, perchance, how that poor formless wretch 

 The Oyster gems his shallow moon-lit chalice 1 

 Where the shell irks him, or the sea-sand frets 

 This lovely lustre on his grief." 



Of late years, however, this view has been discredited by scientific investigators, 

 and some recent writers seem to exclude altogether the grain of sand from participation 

 in pearl causation. We cannot agree with that attitude. There is no doubt that 

 occasionally a particle of sand or other inorganic material does form the nucleus of a 

 free pearl. We have ourselves found three such, out of hundreds of pearls examined. 

 in the course of our investigation. But, as a rule, any such foreign inorganic matter 

 introduced between the mantle and the shell gives rise only to a pearly or nacreous 

 excrescence, or blister, attached to the shell. Artificial pearls of an inferior sort are, 

 however, sometimes produced in this way ; and the practice in China of forming rows 

 of nacreous beads, or images of a Joss, or of Buddha, on the inner surface of the fresh- 

 water mussel Dipsas plicatus, Leach, depends simply upon the fact that foreign 

 bodies placed outside the mantle will be cemented to the shell by a layer of nacre. 

 The so-called "secret-process" of Linnaeus, often referred to in the literature of 

 pearl-formation, has been shown,* from manuscripts now in the library of the Linnean 

 Society of London, to consist merely in piercing the shell and inserting a small 

 fragment of calcareous matter kept in position by a piece of fine silver wire. 

 Linnaeus, on the evidence of contemporary manuscripts, seems to have obtained by 

 the process certain pearls which the Swedish crown-jeweller declared to be in every 

 way as good as those produced naturally. Probably they were compared not with 

 the most precious pearls from the pearl oysters of Eastern seas, but with those of the 

 Swedish fresh-water mussels (Unio margaritifera). 



In 1898 Boutan experimented in artificial pearl -formation at Roscoff, and succeeded 

 in obtaining pearls from the marine Gastropod Haliotis ; and no doubt they might 

 be obtained artificially from other shell-fish also. 



The importance of all this, from our present point of view, is merely to show that the 

 grain-of-sand method is occasionally found operative in the causation of true pearls, 

 and it is possible that some of those that appear to have no nuclei may have been 

 deposited around very minute inorganic particles. 



The view that the pearl is produced as a calculus, or pathological deposit, was 

 originated by Reaumur in 1717, followed by Bohadsch in 1761, was supported 

 by Meckel and by Pagenstecher nearly a century later, and again revived by 



* ' Proc. Linn. Sue.,' 117th session, p. 18, 1905. 



