PEARL-CULTURE AND PEARL-FARMING 295
Reference has already been made to the parasitic stage of Unios.1 The
attachment of the newly-hatched mollusks to the gills or fins of a fish
is entirely a matter of chance, and unless this takes place they die
within a few days. Under natural conditions the fish thus infected will
rarely be found carrying as many of the parasitic Unios as they can
without serious injury. If the fish are placed in a tank or a pond
containing large numbers of newly-hatched Unios, it is possible to
bring about the attachment of hundreds of them for every one that would
be found there by chance of nature. A fish six inches in length may
thus be made to carry several hundred parasitic Unios, and thus a
thousand fish artificially infected may do the work of several hundred
thousand in a state of nature. Experiments with small numbers of fish
under observation in the laboratory indicate that their infection on a
large scale is entirely possible, and the experiment by Messrs. Lefevre
and Curtis now in progress at La Crosse, Wisconsin, in which over
25,000 young fish have been infected, gives every indication that such
work may be begun even with the scanty knowledge now possessed.
Since
it has already been shown that the production of pearls is an abnormal
condition, it does not follow that an increase in the quantity of
mollusks would necessarily result in a corresponding increase in the
yield of pearls. Indeed, it might even be that the artificial
conditions bringing about an enhanced prosperity and abundance of the
mollusks would result in a corresponding decrease in the product of
gems, the improved surroundings impairing if not destroying the
conditions to which the pearls owe their origin. This has resulted in
directing efforts toward abnormally increasing the abundance of oearls
in a definite number of mollusks.
The
development of the parasitic theory of pearl formation has naturally
invited attention to the possibilities of increasing the yield of
pearls by inoculating healthy mollusks with distomid parasites. It does
not appear that this has yet advanced beyond the experimental stage,
and virtually all that has been accomplished has been set forth in the
chapter on the origin of pearls. It seems that there are great
possibilities in the artificial production along these lines; and that
under skilful management it could be made a profitable industry,
especially if carried on concurrently with the systematic cultivation
of mother-of-pearl shells.
Although
there is scientific basis for the belief that it may be possible in
time to bring about pearl growth in this manner, the public should not
be too hasty in financing companies soliciting capital for
establishing so-called "pearl farms." Every once in a while
announcement
*See p. 7z.
