224 PROCEEDINGS OP THE MALACOLOGICAL SOCIETY. 



It is difficult to understand why Mr, Mikimoto should have 

 patented and thereby published the details of his process. The 

 grafting operation is one of a very delicate nature, requiring quick 

 and deft workmanship more likely to be attained in an Asiatic race 

 in which the cultivation of the arts is instinctive, than in Western 

 races ; and the implantation of the artificial sac in the body proper 

 or "under the liver" in the posterior part of the living oyster, 

 where the secretion of pure white pearl is to be secured, is a much 

 more difficult matter than in the mantle in the anterior region, 

 where in Pinctada martensii, Dkr., there is great probability of the 

 pearl being of a decidedly yellowish tinge. Nevertheless, the grafting 

 of shell- secreting epidermis and its conversion into a pearl-secreting 

 sac, marvellous as it may sound, is inferior in novelty to and less 

 remarkable to pathologists than the experiments performed at 

 Plymouth by Mr. G. H. Drew on Pecten and the formation of a cyst 

 within the adductor muscle of one scallop by the conversion into 

 columnar ciliated epithelium of the inner layer of fibroblasts, 

 stimulated by the artificial introduction of a fragment of living 

 ovarian tissue from a second scallop, such fragment (acting as a 

 nucleus) degenerating in six days leaving a residue of a few 

 blood cells and granular matter. This marks a new departure in 

 metaplasia, as will be seen from the following conchisions culled 

 from Mr. Drew's paper ^ : — 



Ribbert, 1908. " Only tissues that, while externally different, 

 possess nevertheless the same histogenetic capacities can 

 undergo metaplasia one into the other. 



On the other hand, 

 Leo Loeb, 1899, records that in cases of epithelial regeneration in 

 vertebrates, he has observed epithelial cells migrate into under- 

 lying tissues, and take on the appearance of fibroblasts. 

 Drew, 1910, on Cardium norvegicum. Corpuscles coming into 

 contact with a rough foreign body or injured tissue possess the 

 power of agglutination and forming a compact plasmodial 

 mass, and the same in Pecten. 

 Sir Ray Lankester, 1886-93, shows that certain corpuscles in 

 Ostrea edulis have a phagocytic action on diatoms and minute 

 green algae. 

 Drew, 1910, Corpuscles of Cardium norvegicum have phagocytic 

 action on bacteria and are attracted towards extracts of dead 

 tissues. 

 From a pearl student's point of view Mr. Drew's experiments 

 would have been more interesting if the insertion had been made 

 in the body proper, or in the mantle lobes, rather than in the 

 adductor muscle, the pearls from which in a pearl oyster are of 



^ Journal of Experimenta] Zoology, vol. x, 1911 (U.S.). 



