102 Proceedings of the Royal Physical Society. 
considered had mucli to do with the formation of pearls. This 
worm he found in large numbers in the liver, ovary, mantle, 
and other parts of the oyster. He also considered, from his 
researches into the subject, that the ova of the oysters and 
the ova of worms form the nuclei of many pearls found in the 
soft parts of the animal, according to the doctrine of Sir 
Everard Home. This theory has, however, been called in 
question by many authors. Dr Kelaart had sent for examina- 
tion specimens of ovaries, containing pearls of various sizes, 
to the Museum of the Royal College of Surgeons, London, 
which he considered tended to prove the truth of these views. 
In pearls adherent to the shell he found the nuclei to be sand, 
portions of sea-weed, and larvse of insects, &c. In conclusion, 
Dr Kelaart recommended that only the larger and more 
matured oysters should be fished, and that portions of the 
banks should be reserved for breeding purposes. 
Mr Alexander Bryson believed pearls to be the result of 
disease or of irritation, caused by the presence of foreign 
bodies. He stated that, in all his experience, he had found a 
nucleus of foreign and structureless matter, generally siliceous ; 
also, that he could, by examining the microscopic structure of 
a pearl, at once infer what shell had produced it. 
II. Note on the Lantern Flij of Honduras, Bj Mr James Banks. 
Communicated by Dr J. A. Smith. 
At a previous meeting a specimen of the lantern fly [Ful- 
gora laternaria) of Honduras, from Mr Banks, was exhibited, 
and doubts having been cast on Madame Merian's statements 
as to its being really luminous at times or not, Mr Banks was 
requested to get farther information, if possible, on the subject. 
Dr Smith said he had been favoured with various letters, ex- 
tracts of which were read. These Mr Banks had received from 
correspondents in Belize, and they bore testimony to the truth 
of the statement of this fly really emitting a light. One from 
Mr Alex. Henderson, Belize, gives the following details : — 
" In answer to the question ' Is it really luminous V Cer- 
tainly the fly possesses light, and therefore emits it. The 
light is evidently under its control, for it increases and dimi- 
nishes it at pleasure. When the wings are closed, there are 
