tHE TROPICAL Ad-RlCULTtJRIST. [April 1, 1903. 
report further sales which, we think, will be of 
interest to your readers 
Mark Cases Sold at per lb 
Onlloden 6 Fine thin biscuits 4/2 
flo 2 , Good scrap B/ii 
flo 1 Large balls scrap 3/0| 
«o I Scrap good 3/2 
do 1 Scrap fair 3/0| 
EdengoUa 3 Fine thin biscuits 4/2 
do 1 Good scrap 3/l| 
Clyde 2 Fine thin biscuits 4/ . 
do a Scrap 3/ 
Kumaradola 1 Fine in small biscuits 3/4? 
Yatipauwa 8 Scrap 3/o| 
Igalkande 1 crate Fine thin biscuits 4/2 
Aberdeen 1 case Fine thin biscuits 3/10 
do 1 bag Good scrap 3/li 
Tudngnlla 5 cases Fiue thin biscuits 4/2| 
The market is strong and prices seem likely 
to go higher. Kindly insert above in your paper, 
as planters are much interested.— We are, dear 
Sir. yours faithfully, LEWIS & PEAT. 
P.S — Fine Para Ss 8Jd to 3s 9d. 
PLANTING NOTES. 
The Nahavilla Estate Co. Ltd.,— The 
directors and shareholders and the Agents 
and Secretaries of this Company have our 
warm congratulations on the return of 
prosperous times after some two or three 
years decidedly discouraging balance sheets. 
The report appears on page 698, and it 
will be noted a 5 per cent dividend is 
declared. 
Vanilla,— An item that will have some in- 
terest to vanilla growers is the following :— A 
consignment ot about 300 kilos of vanilla culti- 
vated in German East A.frica arrived in Hamburg 
a short time ago. The beans are said to be of fine 
dark chocolate colour and are commencing to crys- 
tallise. They are ot various lengths, and are 
reported to compare favourably with the best 
Bourbon quality. — Agricultural News, Feb. 14. 
Failure in the Rubber Trade.- At a meet- 
ing yesterday afternoon of the creditors of Messrs 
Kramrischand Co, rubber merchants, of Liverpool, 
the liabilities were stated at £111,663 lis, and the 
assets at £7,089, leaving a deficit of about .€104,000. 
in regard to the absence of Mr Kramrisch abroad, 
about which rumour has been busy, it is stated on 
goad authority that he has been endeavouring to ar- 
range matters for the benetifc of his creditors and 
will shortly return. A committee has been ap- 
pointed to carry out a deed of assignment. — 
London Times, Feb. 25. 
Gum Arabic- The unsettled condition of 
several parts of the world, notably Soraaliland 
and Morocco, has influenced the position of some 
well known products, one of which we may instance 
namely, gum arable, a fact which shows the 
necessity, witlier of secondary sources for any in- 
dispensable product, or of soma available substi- 
tute. Opposed as we are to substitutes generally, 
it would seem that out of the numerous species 
of Acacia known, a picked or sorted gum might 
yet be found to tide over a time of scarcity, which 
might perhaps end in establishing for itself a repu- 
tation of a lasting character, if not for use in 
food or medicine, at least for manufacturing pur- 
poses,— a remaric that applies to products other 
than y,mua.— Agricultural News, Feb. 14. 
THE FORMATION OP PEARLS. 
A SEASONABLE AETICLE. 
By far the greater number of recent writers on 
pearls, whether scientific or otherwise, when dis- 
cussing the cause of pearl-formation, have con- 
tented themselves with recapitulating what has 
already been written on the subject, without 
attempting to verify or refute the various hypo- 
theses that have been propounded. The question 
is one which has called forth speculative theories 
since the earliest times of which we have any re- 
cords ; but, with the exception of the brilliant 
researches of Filippi and a few of his contempora- 
ries, theory has prevailed to the almost complete 
exclusion of practical investigation. 
In a recent paper, based upon an examination 
of large quantities of material comprising a num- 
ber of the pearl -producing species of mollusca, I 
have tried to place our knowledge of the matter 
upon a more satisfactory basis. By observations 
upon pearl-bearing examples of the common mussel 
Mytihis edulis (which were confirmed in the case 
of all other species examined), I proved that the 
formation of the pearl takes place inexactly the 
same way as that of the shell, except that a true 
pearl is laid down in a closed sac of the shell- 
secreting epithelium, embedded in the subepidermal 
tissue of the mantle and completely cut off from 
the outer epithelium itself. Inside this spherical 
epithelial sac, the shell substance is laid down 
in the concentric layers that are so characteristic 
of the pearls, instead of in the parallel lamellae 
which are fouad in the shell itself. Such a sac, 
with its contained pearl, may be compared to a 
human atheroma cyst. This makes it necessary 
for us to draw a sharp 
DISTINCTION BETWEEN PEARLS PROPER AND 
BLISTERS OR PEARLY EXCRESCENCES 
of the shell lining, which are secreted by the outer 
(shell-forming) mantle epithelium, to cover over 
foreiern bodies that have intruded themselves 
between the mantle and the shell or to repair the 
damages done by shell-boring domiciliaries. " Con- 
cretions" are, again, distinguished from pearls as 
cak'osphseritic bodies Which have not a cuticular 
origin from an epithelium, but seem to arise by 
free crystallisation in the mantle or other tissues. 
The term "attached pearl" should be applied 
only to pearls which have become secondarily 
fused to the shell by absorption of the intervening 
tissues. From the facts of pearl-formation, it is 
easy to understand why the pearl presents the 
special characters of the particular species of shell 
from which it is taken, and also why, in the same 
mollusc, the characters of the pearls produced are 
determined by the part of the mantle in which 
they are formed. Thus, pearls formed in the 
extreme mantle margin are composed mainly of 
periostracum, e. g. the leathery pearls of Modiola 
modiolvLS, while those which occur in the part of 
the mantle concerned in depositing the prismatic 
substance are made up of concentric layers of rod» 
like prisms, as in the brown or " black " pearls 
of the Scotch river mussel^ Margaritana mar- 
garitifera {¥\g. 1). By far the greater part of 
the mantle epithelium deposits the nacre, and 
pearls which arise in this part of the mantle are 
the typical nacreous ones, to which the great 
majority of the marketable gems belong. 
Even the unealcified substance of the hinge liga- 
ment of the shell may be represented in the pearls; 
