PEARLS. 231 



which naturally serves for the nucleus appears to be very 

 often, or, as Sir E. Home says, always, a blighted ovum. 

 Christophorus Sandius, in 1673, on the authority of Hen- 

 ricus Arnoldi, " an ingenious and veracious person," asserted 

 that the ova left unexpelled from the shell became the nuclei 

 on which pearls, in the freshwater mussel, were formed. 

 "Sometimes," he says, "it happens that one or two of 

 these eggs stick fast to the sides of the matrix, and are 

 not voided with the rest. These are fed by the oyster 

 against her will ; and they do grow, according to the length 

 of time, into pearls of sufficient bigness, and imprint a 

 mark both on the fish and the shell, by the situation, con- 

 form to its figure." This theory has been fully adopted 

 by Sir E. Home, from whose paper I have made the above 

 quotation. * " If," says this unworthy anatomist, " I shall 

 prove that this, the richest jewel in a monarch's crown, 

 which cannot be imitated by any art of man, either in the 

 beauty of its form or the brilliancy and lustre produced by 

 a central illuminated cell, is the abortive egg of an oyster 

 enveloped in its own nacre, of which it receives annually 

 a layer of increase during the life of the animal, who will 

 not be struck with wonder and astonishment ? " And, as 

 proofs of this, he informs us that he has always found the 

 seed-pearls in the ovarium, or connected with that part of 

 the shell on which the ovarium lay ; and he has discovered 

 that all oriental pearls have a brilliant cell in the centre, 

 of a size exactly large enough to contain one of the ova. 



introduce them through the shell of the oyster, with the convex surface 

 towards the animal ; the prominent part is, consequently, covered with 

 nacre, and annually receives an increase. By introducing hemispheres in- 

 stead of spheres, they avoid irregularities on the opposite surface. In this 

 manner half pearls are made, since they cannot make whole ones; and when 

 these are set to represent pearls, they will pass off undiscovered by an inex- 

 perienced eye, hut not by those who understand pearls, being deficient in 

 lustre." Comp. Anat. v. 296. Mr. Gray, however, has proved that this 

 people introduce, for the same purpose, pieces of mother-of-pearl, and 

 also portions of silver wire, bent into a peculiar form, between the mantle of 

 the animal (while yet alive) and the shell ; " for they could not have been 

 put in through a hole in the shell, as there was not the slightest appearance 

 of any injury near the situation of the pearls on the outer coat." Mr. Gray 

 tried the experiment on our fresh-water mussels, by introducing pieces of 

 mother-of-pearl between the mantle and the shell ; but with the result I am 

 not acquainted. He adds : " If this plan succeed, which I have scarcely 

 any doubt it will, we shall be able to produce any quantity of as fine pearls 

 as can be procured from abroad." See Home's Lectures, v'. 300, 301 ; Edinb. 

 Phil. Journ. xiv. 199 ; Annals of Philosophy. 



* The quotation varies a little from the text as printed by Forbes and 

 Hanley, who spell the author's name Sardius ; and his informant's name is 

 made Arnoldt. Moll. Brit. ii. 152. 



