T. Southwell 
^ 1 
o\ 
become covered with concretions wiiich adhere to the shell. When these 
concretions have reached a suitable size, they are carved out of the shell 
and sold. The industry is carried on largely by women who have small 
farms of about 1,000,000 oysters. The pearls thus artificially produced 
are never round and they always have one bad face, anti are therefore 
only used for mounting, when the defects are hidden in the mount. It 
is obvious that if the potential pearl-inducing larvae of the Ceydon 
oyster could be treated so as to die in situ, the production of true 
cyst pearls would be greatly enhanced and would result in the fishing of 
a small number of these oysters being as profitable as is the fishing of 
millions at the present time. 
Passing on from this first known stage in the history of the pearl- 
inducing worm (viz. the globular cyst in the oyster), we find that the 
next stage known is the young but adult Tetrarhynchid occasionally 
found encysted in the gut of the oyster’. Being practically' adult, they 
are so different from the globular cyst that there seemed at first to be 
no particular reason for presuming that they represented different stages 
in the development of the same parasite. They ocorr almost in every 
case encysted in the wall of the gut, just where the intestine turns 
to run direct to the anus. They are usually found in cluster’s of two 
to five. They often rrreasure 1'5 mnr. The four proboscides and the 
two bothridia are fully formed, and the former are often protruded. No 
strobila is present, but the worms are adult in every other way, except 
that they are small. The dissimilarity between this stage and the stage 
represented by the globular cyst will be obvious when it is stated that 
the larvae irr the globular cyst are so yoirng that the Cestode characters 
are by no means well defined. No stage or stages have ever been found 
intermediate between them, and the evidence that they really are stages 
in the life history of the same parasite rests on circumstantial evidence 
only and on the results obtained by the feeding experiments to which 
we shall refer later. The only other known stage in the life history of 
this parasite is the adidt worm itself, which was first obtained from 
Rliinoptera javanica It is unfortunate that specimens are so rare that 
the adidt has not been described as fully as it might have been. With 
the material now in my possession, and the observations which have been 
made, I am hoping shortly to add further particulars regarding this 
parasite. So rare is the adult, that, in spite of the fact that several 
thousands of fish, caught with the trawl, • have been carefully and 
repeatedly examined — including large numbers of both sharks and 
rays—the adult has never since been found except in Gingli/))iostoma 
