No. 51.— 1900.] 



PEARL FISHERIES. 



193 



to be hoped that Nature has limited this marvellous power of self- 

 transformation to the oyster, which exceeds, I think, all that the new 

 woman with all her claims for woman's rights could imagine in her 

 wildest dreams. But I believe even Mr. Collett is not quite sure on 

 this point, so that one of the most important problems connected with 

 the life-history of this bivalve still remains to be solved by Science. 

 Another point on which I should wish to be enlightened by Mr. Collett 

 is with regard to the formation of pearls. He has given in his adhesion 

 to the parasitic theory, and even quotes Dr. Kelaart in support of it ; 

 but a careful reading of Dr. Kelaart's reports > both of 1857 and 1858, 

 seems to me to show that while he only countenanced the parasitic 

 theory as accounting for exceptionally, as it were, the formation of 

 pearls in some cases, he never abandoned his original theory, made 

 from actual observation, that the true nuclei of true pearls are the ova 

 of the pearl oyster itself as a rule, and only exceptionally the ova of 

 parasites that enter its body with its food, while only inferior and 

 irregular false pearls result from the artificial intrusion of particles of 

 sand, &c, to serve as nuclei. So far as my reading goes, Dr. Evarard 

 Home, in the last century, was the first to advance the theory of abortive 

 ova being the nuclei of pearls, and Dr. Kelaart at first accepted it with 

 a modification by saying that it was not the ova which are left behind 

 in the ovarium, but those which escape through the over-distended coat 

 of the egg-chamber, when it ruptured as it may easily do near the hinge, 

 when they would bury themselves in the interstices of the mantle and 

 so become the nuclei of pearls. But in his later Report of 1859 he says 

 he was so fortunate as to find an entire ovarium charged with no less 

 than 32 pearls, and still another which he did not open, but which 

 appeared to contain as many more — thus completely confirming Dr. 

 Home's theory. Both these specimens he sent to Dr. Owen, and are 

 now to be seen in the Museum of the College of Surgeons in London. 

 How, or whence the nacre or pearl-lining substance was formed for 

 these pearls in the ovary, Dr. Kelaart would not orcould not determine, 

 but he supposes with great probability — what Science at the present day 

 can easily confirm — that the ovarium membrane can secrete it. For 

 it is a curious circumstance that human pathology affords analogous 

 illustrations both of abortive ova and even embryos becoming the 

 centres of new and varied forms of all growth, and sometimes of 

 concretions of an intensely hard character known aslithopadia ; but, still 

 more curiously, that the lining membrane of the ovary from which 

 proceed these metamorphosed but unimpregnated ova sometimes 

 secretes the most extraordinary structures, such as bones, teeth, hair, 

 &c, without any trace of embryonic formation, which may even grow 

 from the ovary of the embryo itself, and become serious pathological 

 tumors in after life. It is unnecessary for me to point out the bearing 

 that this theory of Dr. Kelaart's has on the proper method of oyster 

 culture. Entirely opposed as it is to that now proposed, based on the 

 theory that conditions which favour the entrance of parasites which 



