se he saw it attached to a rock, jumped to the
conclusion that it was of vegetable origin. But after being kicked back
and forth, so to speak, from one kingdom to the other, even by what are
called well-educated people, it has finally been received into the
family of animals; a dignity in which the sponge itself seems to take
but little interest.

The sponge is found in the bottom of the sea; at no very great depth,
however. It is usually attached to a rock or some other substance and it
is due to this fact chiefly that it has been classed as a vegetable. At
least one scientist has attempted to give it a place between the two
kingdoms, but this only adds confusion without giving any satisfactory
explanation of its origin. It seems to belong to a very low order of
animal life. It breathes water instead of air, but probably, like many
other water animals, it absorbs the oxygen from the air which is more or
less contained in the water. There is a process of oxidation going on
within the sponge in a manner somewhat as we find it in ordinary animal
life, and like the animal it expels carbon dioxide. All this, however,
is carried on apparently without any lungs or any digestive organs, or
in fact any of the organs that are common to the animals of the higher
order. The sponge, however, as we see it in our bathrooms, is only the
framework, bony structure, or skeleton of the animal.

The sponge is exceedingly porous and readily absorbs water or any fluid
by the well-known process of capillary attraction. The sponge fiber is
very tough and is not like anything known to exist in the vegetable
kingdom. The substance analyzes almost the same as ordinary silk, which
all know is an animal product. If we burn a piece of sponge it exhibits
very much the same phenomena as the burning of hair or wool, and the
smell is very much the same.

The structure of a piece of sponge when examined under a microscope is a
wonderfully complicated fabric. Under the microscope it shows a network
of interlacing filaments running in every direction in a system of
curved lines intersecting and interlacing with each other in a manner to
leave capillary openings.

It is a wonderful structure, and one that a mechanical engineer could
get many valuable lessons from. It will stand a strain in one direction
as well as another. There are no special laminations or lines of
cleavage; it is very resilient or elastic, and readily yields to
pressure, but as readi