himself to solve the difficulty, was contented, in the true spirit of a
lover of nature, with carefully recording the results of his accurate
observations, and advancing his opinion rather in the form of an inquiry
than of an allegation. Upward of two thousand years rolled away ere this
question was satisfactorily answered. Nay, we believe that the vegetable
theory has, even at the present time, its advocates; while some are
still disposed to consider that the sponge is at one period of its
existence a vegetable, and at another an animal.

To any one who hesitates to acknowledge that the sponge is endowed with
animal life--confessedly in its lowest form, yet with a most exquisite
adaptation to its destiny--we would offer the spectacle of a living
sponge in a portion of its native element. We would let him gaze on the
animated fountain, which is perpetually sucking the water into its
substance through its countless pores, and after assimilating such
particles of it as are essential to its existence, ceaselessly expelling
it, at more distant intervals, through the larger channels which may be
observed on its outer surface. We would point out innumerable gemmules
of gelatinous matter, which at certain seasons of the year may be seen
spouting "from all parts of the living film which invests the horny
skeleton;"[24] until, at length, escaping from the nursery in which they
grew, they are carried off to the wide sea by means of the force of the
currents issuing from the sponge, though not left to perish at the mercy
of the waves. For he will find that the young animal or egg is covered
with numberless minute hairs or _cilia_, each one of which is endowed
with a distinct and innate power of vibration; so that by means of
thousands of almost invisible oars, the young sponge "shoots like a
microscopic meteor through the sea," until it arrives at some rock or
other place properly adapted for its future growth; then it settles
calmly and contentedly down, and gradually losing its locomotive power,
begins to spread on its base; and builds up, within its living
substance, a horny framework, such as we have already seen in its
parent.

The above-named currents may be more distinctly seen by powdering the
surface of the water with chalk or any similar substance; and Professor
Grant mentions, that by placing pieces of cork or dry paper over the
apertures, he could see them moving "by the force of the currents at the
distance of ten f