University Missourian. [volume] (Columbia, Mo.) 1908-1916, 1912-05-09

shells. Perhaps you have found cup
shaped shells and observed the pinl
and white inner surface.
"Mussel Shells" you may have
called them. Well. they were. Bu
they were also the remains of tn,
home of fresh water clam.
If you walk up the long flight o.
stairs in the Zoology Building ant
wander around through several small
passages, past doors that have com
binatiOn locks you will. find 81,
big tanks in the center of one of the
laboratory rooms. Emptying into
each tank is stream of water from
pipe above. If you step up to the
tanks and look down at the bottom
of six inches of water you will SEE
number of large shells. Darling in
and out among the shells are scores
of small tadpOles and crayfish.
But look at that big shell. 1t is
moving. Look at the trail it leaves
in the sand of the artificial riyerbed
Something like miniature snow
plOw. No, it is more like the hull OF
small boat. And it is being pulled
along by sort of foot that reaches
out into the sand and drags the shell
after it. You have seen the fresh
water clam in his artificial river-at
home in his crude shell.
What are they?" You ask the
zOOlOgist.
His answer: They are bivalve
mollusks of the species 'Mytilus
Edulis."'
Those same clans may have lived
for years and years and travelled
through many waters and over the
beds of many streams before they
reached the size they are now.
When they first showed symptoms
of life they had just emerged from
eggs that were many times smaller
than the point of pin. They had
several thousand brothers and Sis
ters the season they were born.
For a long time they remained in
the hOme-like shell of their mother
until they grew larger. They were
in little cells close to the opening in
the shell through which a current of
pure water passed. This water fur
nished oxygen for breathing and food
for sustenance of the large mussel.
Then their substance charged to a
number of small cells, some of which
formed new part of their body and
some another. On the back of each
of the micro-organisms was a. slight
depression. This was the beginning
of the shell-gland. The function of
this gland is to gather the limestone
in solution in the water and secrete
it so that the mussel will have a
shell. First it develops into a
straight plate on top of the animal.
Then, as it grows, it develops into
two small cOncave valves.
AS these valves grow more dis
tinct. small hooks. turning downward
and inward, develop. That is, of
course. if the mussels are living in
the waters around Columbia. Many
other kinds of mussels do not have
the hooks on the inside of their
shells.
Now they are ready to leave the
paternal shell. On the bottom of
the river or creek they find a resting
place. Sometimes they are carried
with the current. They are taking
more the shape of mussel by this
time. Both of the valves are opened
wide and a small thread of muscle
tissue sticks up from the irregularly
formed mass that holds the walls of
the shell together. This might be
called their "feeler" in language not
geological.
They are now ready to become a
,arasite on another and larger ami
NAL. But they are still very small.
t would take two of them to cover
the head of pin.
While they are taking life easy
with their feeler out for possible
sictim, they are drawn through the
siI!s of fish. When the feeler
touches the gills, the edges of the
yalves are clamped together and the
mussel youngsters have a new home
for while. The outer skin of the
fish closes over them in two or three
hours and they thrive on it's blood.
They remain there for two or three
months Their rapid growth soon
bursts the skin of the fish in a small
irritation and the mussels are free
again.
But their development has been
rapid and their transformation from