July 1, 1903. J 
THE TROPICAL AGRICULTtJRIST. 
37 
Other species of Ocinuni are : 0 canum (Hin- 
tala), the leaves of which are pleasantly aromatic 
when Iruisei!, 0. hasilicum (suvauda tala), the 
" Sweet Bar.l," with a verj' sweet aromatic Hcent 
when bruised. 0. (/ralissiui am (gas tala) and its 
varii ty 0, sicave, wii h faintly aromatic apple-like 
scent, and used in medicinal iuinijiations. Lastly 
0. adscc)idcn>i. 
The majority of tropical labiates are character- 
ised by aromatic properties, such as species of 
Mentha, Coleus, Flectrauthus, Pogostemon, &c. 
Anisomeles ovata, another member of this order, 
whicli possesses " a warm Camphoreaceous scent " 
must, however, take the palm for keeping ofif 
noxious creatures, tor we read that the smoke 
from this is believed by the natives of Ceylon 
to drive away uot mosriuitoes but demons ! — 
"Agricultural Magazine," May, 
» 
THE PEARL FISHERIES OF CEYLON.* 
The celebrated pearl "oysters" of Ceylon are 
found mainly iu eertaiu parts of tlie wide shallow 
plateau v/hicli occupes the upper end of the Gulf of 
Manaar, off the north-west coast of the island and 
south of Adam's Bridge. 
The animal {Marqaritifera vulgaris, Schum = 
Avicula jvcata, Gould) is not. a true oyster, but 
belongs to the family Aviculida', and is therefore 
more nearly related to the mussels (Mytilus) than 
to the oysters (Ostra3i) of our sea. 
The fisheries are of very great antiquity. They 
are referred to by various classical authors, and 
Pliny speaks of tiie pearls from Taprobane (Ceylon) 
as " by far the best in the world." Cleopatra is 
said to have obtained pearls from Aripu, a small 
vilage on the Gulf of Manaar, which is still the 
centre of the pearl industry. Coming to more 
recent times, but still some centuries back, we 
have records of tisheiios under the Sinhalese kings 
of Kandy, and subsequently under the successive 
European rulers — th' Portuguese beingin possession 
from about 1505 to about 1655, the Dutch from 
that time to about 1795, and the English from the 
end of the eighteenth century onwards, A notable 
feature of these fisheries has been 
THEIR UiNCERTAINTY. 
The Dutch records show that there were no 
fisheries between 1732 and 1746, and again between 
1768 and 1796. During our own time the supply 
failed in 1820 to 1828 in 1S37 to 1854, in 1864 and 
several succeeding years, and linaily after five 
successful fisheries in 1887, 1888, 1889, 1890 and 
1891 there has been no return for the last decade. 
Many reasons, some fanciful, others with more or 
less basis of truth, have been given from time to 
time for these recurring failures of the fishery; and 
several investigations, such as that of Dr Kelaart 
(who unfortunately died before his work was 
completed) in 1857' to 1859. and that of Ux Holds- 
worth in 1865 to 1869, have been uadertaken 
without much practical result so far. 
In Ssntenilier, 1901, I was asked to examine the 
records and i eport on the matter and in the fol- 
lowing spring v.'as invited by the Government to 
go to ("eylon with a scientific assistant, and 
undertake wliat iij vesfiijation into the condition 
of the banks miglit be consi{iercd necessary. 
Arriving at Colombo in January 1902, as soon as 
a steamer could be obtained we proceeded to the 
pearl banks. In April it was necessary to return 
* Abstract of a discourse delivered at the Eoyal 
Inatitution on March 27 by Prof, W A Herdman, F,fl,S, 
to my university duties in Liverpool, but I was 
fortunate in having taken lut with me as my 
assistant Mr James Hornelijw ho was to remain in 
(Ceylon for iit least a year lougur, in <;rder to cairy 
out. the otsei valionsi and experiments we lia'd 
arranged, and complete our work. Tliis programme 
has been cariied cut, and Mr Hornell has kept me 
supplied with weekly reports and with 
SPECIMENS RFQ' IRING DETAILED EXAMINATION. 
The ss. "L.;dy Haveiock" was placed by the 
Ceylon Governmental my disposal for the work 
of examining into the biological conditions sur- 
rounding the pearl oyster banks ; and this enabled 
us on two successive cruises cf three or four weeks 
each to examine all the principal banks, and run 
lines of dredging and trawling and other observa- 
tions acrossaround and between then), in order to 
ascertain the conditions that determine an oyster 
bed. Towards the end of the time I foi/U part in 
the annual icspeetion of the pearl banks, by means 
of diveis, along with the retiring inspector, 
Op'ain J Donnac, CMC, and his successor. 
Captain Legge. During that period we lived and 
worked in the native barque Rannasuii teporaivee, 
and had daily opportunity of studying the methods 
of the native divers with the results they 
obtained, [These were discussed and illustrated. 
It is evident that there are two distinct questions 
that may be laised— the first as to tlie abundance 
of the adult " oysters," and the second as to the 
number of pearls in the oysters— and it was thehrst 
of ihase rather than the fiequency of the pearls 
that stemed to call for investigation, since the 
complaint has not been as to the number of pearls 
per adult oyster, but as to the complete ilisappear- 
ance of the shell-fish. 
Most of the pearl oyster bauKS or " Paar " 
(n,eaning rock or any form of hard bottom, in 
distinction to " Manul," which indicates loose or 
soft sand) are in depths of from 5 to 10 fathoms, 
and occupy the wide shallow area of nearly 50 
miles in length, and extending opposite Aripu to 
20 miles in breadth, which lies to the south of 
Adam's Bridge. On the western edge of this area 
there is a steep declivity, the sea deepening within 
a few miles from under 10 to more than lOOfathoms; 
while out in the cetitre of the southern part of the 
Gulf of Manaar, to the west of the Chilaw Pearl 
Banks, depths of between one and two thousand 
fath jms are reached. On our two cruises in the 
" Lady Havelock" Vv'e made a careful examination 
of the ground in several places outside the banks 
to the westward, on the chance of finding beds of 
adult oysters from which possibly the spat depo- 
sited on the inshoie banks might be derived. No 
such beds, outside the known " Paars," were 
found ; nor are they likely to exist. The bottom 
deposits in the ocean abysses to the west of Ceylon 
are entirely different in nature and origin from the 
coarse terrigenous saml, often cemented into 
masses, and the various calcareous uertic deposits, 
such as corals and Dullii)ores, found in the shallow 
water on the banks. The steepest part of the slope 
from 10 or 20 fathoms down to about 100 fathoms 
or more, all along the western coast seems in most 
places to have a hard bottom covered with Alcyo- 
naria, sponges, deep sea coials and other large 
eiiCiustiiig and dendritic organisms. Neither on 
this slope nor in the deep >vater beyond the cliff 
did we find any ground 
SUITABLE FOR THE PEARL OYSTER TO LIVE UPON. 
Close to top of the steep slope, about 20 miles 
from land and in the depths of from 8 to 10 
