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Young Folks' Library: Wonders of Earth, Sea and Sky

A Bit Of Sponge
(Written on Scotland.)
(From Glimpses of Nature.)
This morning, despite the promise of rain over-night, has broken with all the signs and
symptoms of a bright July day. The Firth is bathed in sunlight, and the wavelets at full
tide are kissing the strand, making a soft musical ripple as they retire, and as the pebbles
run down the sandy slope on the retreat of the waves. Beyond the farthest contact of the
tide is a line of seaweed dried and desiccated, mixed up with which, in confusing array,
are masses of shells, and such olla podrida of the sea.
Tossed up at our very feet is a dried fragment of sponge, which doubtless the unkind
waves tore from its rocky bed. It is not a large portion of sponge this, but its structure is
nevertheless to be fairly made out, and some reminiscences of its history gleaned, for the
sake of occupying the by no means "bad half-hour" before breakfast. "What is a sponge?"
is a question [pg 206] which you may well ask as a necessary preliminary to the understanding of
its personality.
The questionings of childhood and the questionings of science run in precisely similar
grooves. "What is it?" and "How does it live?" and "Where does it come from?" are
equally the inquiries of childhood, and of the deepest philosophy which seeks to
determine the whole history of life. This morning, we cannot do better than follow in the
footsteps of the child, and to the question, "What is a sponge?" I fancy science will be
able to return a direct answer. First of all, we may note that a sponge, as we know it in
common life, is the horny skeleton or framework which was made by, and which
supported, the living parts. These living parts consist of minute masses of that living jelly
to which the name of protoplasm has been applied. This, in truth, is the universal matter
of life. It is the one substance with which life everywhere is associated, and as we see it
simply in the sponge, so also we behold it (only in more complex guise) in the man. Now,
the living parts of this dried cast-away sponge were found both [pg 207] in its interior and on its
surface. They lined the canals that everywhere permeate the sponge-substance, and
microscopic examination has told us a great deal about their nature.
For, whether found in the canals of the sponge themselves, or embedded in the sponge-
substance, the living sponge-particles are represented each by a semi-independent mass
of protoplasm. So that the first view I would have you take of the sponge as a living
mass, is, that it is a colony and not a single unit. It is composed, in other words, of
aggregated masses of living particles, which bud out one from the other, and manufacture
the supporting skeleton we know as "the sponge of commerce" itself. Under the
microscope, these living sponge-units appear in various guises and shapes. Some of them
are formless, and, as to shape, ever-altering masses, resembling that familiar animalcule
of our pools we know as the Amoeba. These members of the sponge-colony form the bulk
of the population. They are embedded in the sponge substance; they wander about
through the meshes of the sponge; [pg
they seize food and flourish and grow; and they
probably also give origin to the "eggs" from which new sponges are in due course