ivision of the Animal Kingdom on that account. But even this simplicity
was only apparent in many of them. At certain seasons of the year
myriads of these little Animalcules may be seen in every brook and
road-side pool. They are like transparent little globules, without any
special organization, apparently; and were it not that they are in
constant rotation, exhibiting thus a motion of their own, one would
hardly suspect that they were endowed with life. To the superficial
observer they all look alike, and it is not strange, that, before they
had been more carefully investigated, they should have been associated
together as the lowest division of the Animal Kingdom, representing, as
it were, a border-land between animal and vegetable life. But since the
modern improvements in the microscope, Ehrenberg, the great master in
microscopic investigation, has shown that many of these little
globules have an extraordinary complication of structure. Subsequent
investigations have proved that they include a great variety of beings:
some of them belonging to the type of Mollusks; others to the type of
Articulates, being in fact little Shrimps; while many others are
the locomotive germs of plants, and so far from forming a class by
themselves, as a distinct group in the Animal Kingdom, they seem to
comprise representatives of all types except Vertebrates, and to belong
in part to the Vegetable Kingdom, Siebold, Leuckart, and other modern
zooelogists, have considered them as a primary type, and called them
Protozoa; but this is as great a mistake as the other. The rotatory
motion in them all is produced by an apparatus that exists not only
in all animals, but in plants also, and is a most important agent in
sustaining the freshness and vitality of their circulating fluids and of
the surrounding medium in which they live. It consists of soft fringes,
called Vibratile Cilia. Such fringes cover the whole surface of these
little living beings, and by their unceasing play they maintain the
rotating motion that carries them along in the water.

The Mollusks, the next great division of the Animal Kingdom, also
include three classes. With them is introduced that character
of bilateral symmetry, or division of parts on either side of a
longitudinal axis, that prevails throughout the Animal Kingdom, with the
exception of the Radiates. The lowest class of Mollusks has been named
Acephala, to signify the absence of any distinct head; for though