no PEARLS [CH. 



It will be seen that there are two possibilities. 

 If one be taken there are two hosts only for the 

 parasite. In the other case there are three hosts. 

 In this latter, the worm larva has first to enter a 

 pearl oyster (in which it passes its first days). The 

 pearl oyster must then be eaten by a file fish or 

 other Teleostean in order that the second stage of 

 life of the parasite may be safely negotiated, and 

 finally a third host, the ray, must be reached, by the 

 annihilation of the file fish: — truly an interesting 

 picture of the dependence of animals one on another. 

 If these theories are correct, it is therefore neces- 

 sary for pearl production to be assured to have pearl 

 oysters, worm parasites, file fishes and the rays, pre- 

 sent together in the same locality. 



As a matter of fact it is very probable that the 

 file fish is only an accidental host and that the direct 

 passage of the larva from the pearl oyster to the ray 

 is all that is required \ 



Xow, are we to consider that the majority of fine 

 oriental pearls have been produced by the influence 

 of worm parasites or not ? Jameson doubts the 

 cestode worm theory, although in 1902 he stated 

 that he himself found worm parasites in decalcified 

 and sectioned pearls from the Ceylon oyster. Let us 



1 Jameson believes that there are three distinct species of parasites 

 encysted in the pearl oyster, but in each case the adult worm is to be 

 found in some fish that feeds upon the oysters. 



