124 SPOLIA ZEYLANICA. 
SOME NOTES ON THE CEYLON PEARL-INDUCING WORM.* 
By T. Soutuwe uz, A.R.C.Sc. (Lond.), F.L.8., F.Z.8., 
Scientific Adviser to the Ceylon Company of Pearl Fishers. Limited, 
and Inspector of Pearl Banks. 
THE present series of barren years on the Ceylon Pearl Banks 
has provided opportunities for extensive scientific research, 
which under other conditions would have been impossible. It is, 
however, extremely unfortunate that during these blank years the 
few oysters essential for scientific work have been almost unavailable. 
The only bed which now exists is confined to an inshore area, and © 
the oysters found thereon only rarely contain the pearl-inducing 
parasite. Consequently the investigations on this interesting worm 
have been severely hampered by lack of material, and the research 
work has had to be directed into other channels, such as the investi- 
gation of the part played by currents with relation to exotic spat, 
the examination of rays and sharks for Cestode parasites, &c. 
Whereas normal oysters often each contain from 30 to 100 pearl- 
inducing parasites, the scattered oysters now remaining rarely 
contain a single one, and 200 to 300 oysters may commonly be 
examined without finding a single larva. This condition is doubtless 
due to the inshore position of the oysters. 
Most people are familiar with the old ideas as to the nature of 
pearls, viz., that they were the tears of Nereids, or mysteriously 
consolidated drops of dew, or caused by lightning flashes. These 
poetic beliefs were subsequently superseded by others, which attri- 
buted the origin of pearls to grains of sand, abortive eggs, calculi, 
and the like. 
It was only in 1859 that the naturalist Kelaart, working on the 
spot, made the discovery that the formation of pearls was intimately 
connected with the occurrence in the oyster of “‘ worms,” and all 
subsequent work by other naturalists has only further proved and 
elucidated Kelaart’s statements and observations. In 1894 Thurston 
confirmed Kelaart’s results, and further identified the worm as 
the larva’ of some Platyhelminthian (flat worm). The extensive 
investigations made by Professor Herdman in 1902 further showed 
that the worm was a Cestode (Tape-worm), round the larve of 
which pearls are formed. 

* From the Ceylon Marine Biological Laboratory (Ceylon Company of Pearl 
Fishers, Limited). 
