TUE CEYLON PEARL-OYSTER. 295 



1 tlieu tried the Colombo Museum in the hope of getting some 

 oysters with pearls in situ, but Dr. Pearson had no preserved 

 material to spare. I tried to obtain material from Madras from 

 Mr. Hornell, but he wrote me, in January 191 1, that his own 

 material was exhausted, and that he would not be able to obtain 

 any more till the next inspection, a year later. However, 

 H.H. the Jam 8aheb of Nawanagar most kindly sent me some 

 [•reserved specimens of this species with pearls iu sita from the 

 Culf of Kutch, and I hope, in a later publication, to be able to 

 l»ut forward some observations on the actual process of pearl- 

 pioduction, based on these. 



The following material was available for these investiga- 

 tions : — 



(i.) Twenty-one pearls bought in Ceylon. It is, of course, 

 possible, though not probable, that some of these originally came 

 from elsewhere, e.g. the Persian Gulf vid Bombay, but they, or 

 at least the great majority of them, were certainly derived 

 from 31. vulgaris, the pearls of which have a chaiacteristic 

 colour and lustre quite different from that of the peai'ls found in 

 ^1/. margaritifera and M. maxima. 



They were small " fine pearls," mostly spherical, a few oval or 

 slightly lenticular. One was a brown pearl formed in the mantle- 

 margin from the prismatic substance. They wei'e all decalcilied 

 and examined whole, cleared in oil of cloves, and drawn. They 

 were then sectioned (except in the case of three examples which 

 were preserved whole). Their nuclei were in no cases Cestodes ; 

 they usually contained a cavity with a few granules surrounded 

 by sphan-ocrystal-like matter, allied to or identical with the 

 " repair-substances " described below. In several cases, howevei', 

 the actual nucleus was a grain of sand. These specimens are 

 preserved as preparations XL, XLII, XLIII, XLIV, XLV, 

 XLVII, LI, LII, LIII, LIV, LIV a, LIV b, LIV c, LIV d, 

 LIV E, LIV F, LIV G, LIV H, LIV i, LIV j, and LIV k 

 (Pis. XLI.-XLIII. figs. 35-4.5 and Pis. XLV., XLVI. figs. 50-57). 



(ii.) Dr. Kelaarfs Material in the British Museum. 



In 1901, when I was investigating the origin of peai-ls in 

 Mytilus, Mr. E. A. Smith, I.S.O., allowed me to examine five old 

 specimens of the Ceylon Pearl-Oyster from Dr. Kelaart's 

 collections in the British Museum. Mr. Smith very kindly 

 allowed me to make further use of some of this material for the 

 present investigations. 



The specimens are labelled : — 



" 1 specimen of pearls in ovaiia, 

 3 specimens of pearls in mantle, 

 1 specimen of ova of Entozoa in liver of Meleagrina 

 mar gar itifera ." 



The specimen with '' pearls in ovaria " was a pearl-oyster with 



