THE PEARL FISHERIES OF CKYI.ON. 491 



In connection with cultivation and transplantation, there are vari- 

 ous points in structure, repi'oduction. life-historv. growth and habits 

 of the oyster which we had to deal with, and some of A^llicll ^\(' were 

 able to determine on the banks, while others have been the subject of 

 Mr. Horneirs work since, in the little marine laboratory we esta))- 

 lished at Galle. 



Although Galle is at the opposite end of the island form the pearl 

 banks or ^Tanaar, it is clearly the best locality in (^'vlon for a marine 

 laboratory — both for genei'al /oology and also for working at j)earl 

 oyster problems. Little can be done on the sandy exposed shores of 

 jManaar island or the T»ight of Condatchy — the coasts op])osite the 

 pearl banks. Tlu' fislieries t:d\e place far out at sea, from 10 to 20 

 miles otf shore; and it is clear that any natural history work on the 

 pearl banks nuist be done not from iho shore, but as we did, at sea 

 from !i shij) during the ins])ections. and can not be done at all during 

 the monsoons because of the heavy sea and useless exposed shore. 

 At such times the necessary lal)oratory work suj^plementing the 

 previous observations at sea can be carricM! out nnicli more satisfac- 

 toril}^ at Galle than anywhere in the (Jidf of Manaar. 



Turning now from the health of the oyster population on the 

 " paars,'' to the subject of ])carl formation, which is e^'idently an un- 

 healthy and abnormal process, we find that in the (Vlyon oyster 

 there are several distinct causes that lead to the j)ro(luction of pearls. 

 Some j)eai']s or j^early excrescences on the interior of the shell are due 

 to the irritation caused by boring sponges and burrowing worms. 

 French writers have made similar observations in the case of Donax 

 and other Lamellil)raiichs ; and Dubois (1*.)01) has nu)iv recently 

 ascribed the ])roduction of })earls in nnissels on the French coast, to 

 the presence of the lar\:i of Distonnim margaritarnm. Jameson 

 (lOQ-i) then followed with a moi-(» detailed account of the relations 

 between the pearls in ^lytilus and the Distomid larva', which he 

 identifies as Distomum ( r)rachyc((dium) somateria> (L(>vinson). 

 Jameson's observations A\ere made on nnissels obtaiiie(l partly at IVd- 

 liers (Morbihan), a locality at which Dubois had also worked, and 

 partly at tlu^ Lancashire Sea-Fisheries marine laboi-torv at Piel in 

 the Bai'row Ghannel. Finally. Dubois lias just publislnMl a further 

 p.ote in which, referring to the causation of pearls in Mytilus, he 

 says: " Fn somme ce (]ue c(> dernier [(iarner| aA'ait \u en Angle- 

 terre en ISTl, je Tai I'eti'ouvv en Bretagne en ]!i01. (^)iie](|ues jours 

 apres mon depart de Billiers, M. Lyster Jameson, de Londres, 

 est Venn dens la meme localite et a confirme le fait observe par 

 Garner et par moi." But Jameson has done rather more than that. 

 He has shown that it is probable (his own words are '' there is liardly 

 any doubt") that the parasite causing the pearl-formation in our 



