When a good compound microscope becomes as common an object in our homes
as is a clock or a piano, we may be certain that the succeeding generation
will grow up with a much broader view of life and a far greater
realisation of the beauties of the natural world. To most of us a glance
through a microscope is almost as unusual a sight as the panorama from a
balloon. While many of the implements of a scientist arouse enthusiasm
only in himself, in the case of the revelations of this instrument, the
average person, whatever his profession, cannot fail to be interested.
Many volumes have been written on the microscopic life of ponds and
fields, and in a short essay only a hint of the delights of this
fascinating study can be given.
Any primer of Natural History will tell us that our bath sponges are the
fibrous skeletons of aquatic animals which inhabit tropical seas, but few
people know that in the nearest pond there are real sponges, growing
sometimes as large as one's head and which are not very dissimilar to
those taken from among the corals of the Bahamas. We may bring home a twig
covered with a thick growth of this sponge; and by dropping a few grains
of carmine into the water, the currents which the little sponge animals
set up are plainly visible. In winter these all die, and leave within
their meshes numbers of tiny winter buds, which survive the cold weather
and in the spring begin to found new colonies. If we examine the sponges
in the late fall we may find innumerable of these statoblasts, as they are
called.
Scattered among them will sometimes be crowds of little wheels, surrounded
with double-ended hooks. These have no motion and we shall probably pass
them by as minute burrs or seeds of some water plant. But they, too, are
winter buds of a strange group of tiny animals. These are known as
Polyzoans or Bryozoans; and though to the eye a large colony of them
appears only as a mass of thick jelly, yet when placed in water and left
quiet, a wonderful transformation comes over the bit of gelatine....
"Perhaps while you gaze at the reddish jelly a pink little projection
appears within the field of your lens, and slowly lengthens and broadens,
retreating and reappearing, it may be, many times, but finally, after much
hesitation, it suddenly seems to burst into bloom. A narrow body, so
deeply red that it is often almost crimson, lifts above the jelly a
crescentic disc ornamented with two rows of long tentacles that seem as
fine as hairs, and they glisten and sparkle like lines of crystal as they
wave and float and twist the delicate threads beneath your wondering gaze.
Then, while you scarcely breathe, for fear the lovely vision will fade,
another and another spreads its disc and waves its silvery tentacles,
until the whole surface of that ugly jelly mass blooms like a garden in
Paradise--blooms not with motionless perianths, but with living animals,
the most exquisite that God has allowed to develop in our sweet waters."
At the slightest jar every animal-flower vanishes instantly.
A wonderful history is behind these little creatures and very different
from that of most members of the animal kingdom. While crabs, butterflies,
and birds have evolved through many and varied ancestral forms, the tiny
Bryozoans, or, being interpreted, moss-animals, seem throughout all past
ages to have found a niche for themselves where strenuous and active
competition is absent. Year after year, century upon century, age upon
age, they have lived and died, almost unchanged down to the present day.
When you look at the tiny animal, troubling the water and drawing its
inconceivably small bits of food toward it upon the current made by its
tentacles, think of the earth changes which it has survived.
To the best of our knowledge the Age of Man is but a paltry fifty thousand
years. Behind this the Age of Mammals may have numbered three millions;
then back of these came the Age of Reptiles with more than seven millions
of years, during all of which time the tentacles of unnumbered generations
of Bryozoans waved in the sea. Back, back farther still we add another
seven million years, or thereabouts, of the Age of the Amphibians, when
the coal plants grew, and the Age of the Fishes. And finally, beyond all
exact human calculation, but estimated at some five million, we reach the
Age of Invertebrates in the Silurian, and in the lowest of these rocks we
find beautifully preserved fossils of Bryozoans, to all appearances as
perfect in detail of structure as these which we have before us to-day in
this twentieth century of man's brief reckoning.
These tiny bits of jelly are transfigured as well by the grandeur of their
unchanged lineage as by the appearance of the little animals from within.
What heraldry can commemorate the beginning of their race over twenty
millions of years in the past!
The student of mythology will feel at home when identifying some of the
commonest objects of the pond. And most are well named, too, as for
instance the Hydra, a small tube-shaped creature with a row of active
tentacles at one end. Death seems far from this organism, which is closely
related to the sea-anemones and corals, for though a very brief drying
will serve to kill it, yet it can be sliced and cut as finely as possible
and each bit, true to its name, will at once proceed to grow a new head
and tentacles complete, becoming a perfect animal.
Then we shall often come across a queer creature with two oar-like feelers
near the head and a double tail tipped with long hairs, while in the
centre of the head is a large, shining eye,--Cyclops he is rightly called.
Although so small that we can make out little of his structure without the
aid of the lens, yet Cyclops is far from being related to the other still
smaller beings which swim about him, many of which consist of but one cell
and are popularly known as animalculae, more correctly as Protozoans.
Cyclops has a jointed body and in many other ways shows his relationship
to crabs and lobsters, even though they are many times larger and live in
salt water.
Another member of this group is Daphnia, although the appropriateness of
this name yet remains to be discovered; Daphnia being a chunky-bodied
little being, with a double-branched pair of oar-like appendages, with
which he darts swiftly through the water. Although covered with a hard
crust like a crab, this is so transparent that we can see right through
his body. The dark mass of food in the stomach and the beating heart are
perfectly distinct. Often, near the upper part of the body, several large
eggs are seen in a sort of pouch, where they are kept until hatched.
So if the sea is far away and time hangs heavy, invite your friends to go
sponging and crabbing in the nearest pond, and you may be certain of
quieting their fears as to your sanity as well as drawing exclamations of
delight from them when they see these beautiful creatures for the first
time.
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