This twig, with a drop or
two of the water, we will put between two thin plates of glass, and
place under the field of view of a microscope, having lenses that
magnify the image of an object 200 times in linear dimensions.
Upon looking through the instrument, we find the fluid swarming with
animals of various shapes and magnitudes. Some are darting through the
water with great rapidity, while others are pursuing and devouring
creatures more infinitesimal than themselves. Many are attached to the
twig by long delicate threads, several have their bodies inclosed in a
transparent tube, from one end of which the animal partly protrudes and
then recedes, while others are covered by an elegant shell or case. The
minutest kinds, many of which are so small that millions might be
contained in a single drop of water, appear like mere animated globules,
free, single, and of various colours, sporting about in every direction.
Numerous species resemble pearly or opaline cups or vases, fringed round
the margin with delicate fibres, that are in constant oscillation. Some
of these are attached by spiral tendrils; others are united by a slender
stem to one common trunk, appearing like a bunch of hare-bells; others
are of a globular form, and grouped together in a definite pattern, on a
tabular or spherical membranous case, for a certain period of their
existence, and ultimately become detached and locomotive, while many are
permanently clustered together, and die if separated from the parent
mass.
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