Evening star. [volume] (Washington, D.C.) 1854-1972, 1912-04-28

sands, or even millions OF embr.o young
80 many that IL all reached maturity
there would be nothing known like their
numbers In all the animal kingdom.
sei's life. Wholesale destruction occurs,
and 1t Is there that mans agency can
effectively intervene.
Fortunately for early practical results,
DR.. Lefevre and DR.. Curtis did not have
to work out the natural history of the
fresh water mussels from the beginning
All Of the 400 species existing in the Mis-
sissippi valley belong to families well
known to European biologists, and the
dozen or SO kinds of shells that are At
for button making had been studied in
general way at least. So 1T was known
that the minute larvae thickly embedded
in the f1uted edges of the mussel's gills
the offspring of the mussel itself, whose
gills function as a marsupium, or brood
pouch, and do not discharge the embryos
until the latter have come out of the
egg membrane and are ready for new
mode Of existence. 1t was also known
that the succeeding stage of these lar
vac was passed in parasitism, after
which the young mussel issued forth for
an Independent career.
1t was to the details of this life history,
what practical opportunities it offered.
that DR.. Lefevre and DR.. Curtis bent their
energies. The most critical period for
the young mussel was obviously just
after birth, in the chances encountered
between, on the one hand, smothering in
the sand Of the bottom or being devoured
as a microscope particle of food by one
of its myriad enemies, and, on the other
hand, securing safe Judgment on the fin
or in the gills of some passing fish. For
without fish the young mussel cannot
live. Black bass. rock bass and sunf1sh
are this frail creatures pest friends, and
once 1t secures q hold upon fin or gills 1t
is safe until able to look after itself
But there Is such great chance of no
fish being accessible at the crucial
moment that millions Of the newly
emerged larval mussels die for lack of a
host. Thus the necessity OF the case and
at the same time the culturist's oppor-
tunity are to provide the host.
A.
The bureau of fisheries can easily do
that, of course. In the Mississippi region
it's principal work is the collection of
millions Of young bass and sunf1sh every
spring and summer, when, after the an
nual floods, the overlooked streams have
returned to their banks and left these
young fish in sloughs and pools where
they would die when the dry weather
comes. This is in itself q very nice work
of conservation. It will become really
prodigious economy when these same fish
are made to serve as carriers OF the
parasite mussels.
not arrived at without study and con-
tfnued experiment. Indeed, there are
many aspects yet to be studied. 1t was
not known at first, for instance. that one
kind of fish was not as good a host as
another, or that all were not equally good
hosts for all species of mussels. It
proved, though, that carp and the cat
fishes resist the infection with some kinds
of larvae, and that some kinds of fish, on
the other hand, are so susceptible that
they may be easily killed by the process
of infection. Even the black bass and
sunf1sh, the best of all, will not bear over
infection, and 1t was of course desirable
for economy's sake to determine just what
was the proper degree, both with refer
ence to number Of mussels and survival
of fish.
Besides which. and before which. In
fact. must be known just how the larval
mussels attach themselves and how to
facilitate the process Of contact with the
fishes. This involved the study of some
interesting microscopic details.
The larva that energies from the brood
pouch. it's mothers gills. is called a
glochidium, and 1t Is few tenths of a
millimeter in diameter. According to the
species Of musset. however, the glochidia
are of two types-with hooks on their tiny
valves, without. Those with hooks
can clutch at a substantial surface: those
without must choose a more delicate
membrane upon which to close their tight
little shells.
1t follows very naturally that the
hooked glochidia may be found upon
the fms of the fish, while the hookless
type will fasten upon the gills-for
a fish breathes by opening it's mouth,
the glochidium is carried with the wa
ter into contact with the gills, and
there 1t takes it's hold upon the deli
cate flaments. Once the clutch is ac-
complished, the tissue Of the fish re-
acts and within few hours has formed
q covering over. the musseL Thus en-
cysted the little parasite, visible to the
naked eye upon close examination, re-
mains for a period which may be from
nine to thirty-six days, living upon the
tissues Of the fish.
At the end of that time the cyst is
ruptured, the larva1 shell. now de-
veloped into a young mussel with a
rim of adult growth and full-fedged
adult habits. drops OF and settles upon
the bottom for an independent exist
ence. II it falls upon unsuitable bot