THE CEYLON PEARL-OYSTER, 269 
examining the parasites of the pearl-oyster and their 
influence on pearl-formation. We also decalcified such pearls 
as were found. ‘This work was continued as time permitted 
during the next few weeks, and also by Mr. Hornell after I 
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. Horneil afterwards determined 
that these were Tetrarhynchus larve 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 IL. of his Report, p. vi, dated July 
1904, Prof. Herdman says : 
* On the Cheval 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 preliminar y 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 
LOS? 
On p. 6 of Part V. of the Report (Pearl-Production), Herdinan 
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 Manaar is 
deposited around the young larva of a Cestode.” 
And on p. 15: 
“ We found the Cestode larvee in association with pearls in 
the tissues during our cruises in the ‘ Lady Havelock’ in the 
Gulf of Manaar, in February and March, 1902. It was about 
March 6th (see ieee! p. 70,in Part Tg when cutting up 
Oysters from the western part of the Cheval Paar, that we 
first became convinced that the opaque white elobul: ar larvee 
we were finding encysted in the liver belonged to Cestode 
worms.” 
On the other hand, Shipley and Hornell, in their paper on the 
Parasites of the Pearl-Oyster (Herdman’s Report, IT.), seem to 
imply that at least the elaboration of these observations was 
carried out subsequently to Professor Herdman’s departure from 
Ceylon. Thus, they say (p. 79): 
“These larvee first attracted attention during the second 
cruise of the ‘ Lady Havelock.’ on March 6th, 1902, when 
numbers of the early globular stage were dissected out from 
the livers of oysters dredged from the West Cheval Paar. 
Subsequently, during the investigation carried out at the 
Galle Biological Laboratory, a second and more advanced 
‘yy S 
stage of a Tetrarhynchus larva was found in the same 
[11] 
