THE CEYLON PEARL-OYSTER. 269 



examining the parasites of the pearl-oyster and their 

 intiuence on pearl-formation. We also deciilcified such pearls 

 as were found. This work was continued as time permitted 

 during the next few weeks, and also by Mr. Hornell after 1 

 left. We found various parasites, in the liver especially, 

 some of which were Platyhelminthian and others Sporozoan 

 in their nature, and some of which were enclosed in 

 calcareous capsules. Mr. Hornell afterwards determined 

 that these were Tetrarhynchus larvae of Cestodes, and we have 

 no doubt that they are in many cases the nucleus of the 

 pearl, and the irritating cause of its formation." 



Again, in the preface to Part II. of his Report, p. vi, dated July 

 1904, Prof. Herdman says : 



" OntheCheval Paar, in March 1902, we satisfied ourselves 

 that the ' Orient ' pearl, free in the tissues of the pearl- 

 oyster, is deposited around a cyst containing a Cestode larva, 

 and preliminaiy notices to this effect were published in my 

 Royal Institution Lecture of March 27, 1903, and at the 

 Southport Meeting of the British Association in September 

 1903." 



On p. 6 of Part V. of the Report (Pearl-Pi'oductioii), Herdman 

 and Hornell say : 



" One of the first facts that we were able to determine 

 in connection with the Ceylon Pearl-Oyster, in the spring of 

 1902, was that the Orient pearl in the Gulf of Manaur is 

 deposited ai-ound the young larva of a Cestode." 



And on p. 15 : 



" We found the Cestode larvfe in association with pearls in 

 the tissues dui'ing our cruises in the ' Lady Havelock' in the 

 Gulf of Manaar, in Febi-uary and Mai'ch, 1902. It was about 

 March 6th (see Narrative, p. 70, in Pai-t I.), when cutting up 

 Oystei'S from the Avestern part of the Cheval Paar, that we 

 fii'st became convinced that the opaque white globular larva; 

 we were finding encysted in the liver belonged to Cestode 

 worms.*' 



On the other hand, Shipley and Hornell, in theii" pnper on the 

 Pai'asites of the Pearl-Oyster (Herdman's Report, II.), seem to 

 imply that at least the elaboration of these observations was 

 cari'ied out subsequently to Professor Herdnian's departure from 

 Ceylon. Thus, they say (p. 79) : 



" These larvpe first attracted attention dui'ing the second 

 cruise of the ' Lady Havelock,' on Mnrch 6th, 1902, when 

 numbers of the early globular stage wei-e dissected out from 

 the livers of oystei's dredged from the West Cheval Paai-. 

 Subsequently, dui'ing the investigation cai'i'ied out at the 

 Galle Biological Laboi'atory, a second and more advanced 

 stage of a Tetrarliyvclna^ larva was foinid in the same 



