black of the common sponge _(Euspongia officinalis)_ to a pure white.
Also, it may be remarked, the sponges growing in deep water are of less
decided color and more elastic in character than those living in shallow
water, and from the last named quality are more valuable in commerce.
The irregular honeycombed appearance of the sponge is due to a most
complicated canal system, consisting of a series of chambers through
which the water is drawn by the animal in always the same direction.

The inhalent pores are very minute, and open into small subdermal
cavities which communicate by means of interradial tubes with the
ciliated chambers, the latter being very small ramifications of the
interradial channels, and in them the movement causing the current of
water is maintained. From hence all faecal and other matter is
discharged through the oscula, the larger openings observed on the
surface of the sponge. Dr. Ledenfeld showed the different parts of
sponges by means of microscopic slides thrown on to a screen, and also
the shape and arrangement of the chambers in different species. The
ciliated chambers especially attracted attention. They are very small
and circular, and the interior is clothed with cells very similar to the
cilia cells in higher animal life.

These cells are arranged around the ciliated chambers in the form of a
collar, and from each cell flagella protrude, which are in continual
motion. These flagella, like bats' wings, are capable of being bent in
only one direction, so that, in the course of their pendulum-like
motion, in the movement one way the flagella are bent, while in the
return movement they remain stiff, thus causing a current of water
always flowing in one and the same direction. These ciliated chambers
are easily detected in the sponge by means of a microscope, as they
appear more highly colored. After the lecturer had thus given a general