the microscope reveals to us dust as existing
under a thousand charming and admirable
forms. The microscopist is obliged to study
dust attentively, that he may not mistake
some stray hair, or scale, for a portion of the
object he is engaged in examining. There is
antediluvian dust, which was organised into
beauty before Adam had come into the world
to behold it; there are dust-skeletons, which
constitute mountains in their immense aggregate;
there is living dust, which drops from
cheese, or metamorphoses itself out of
farinaceous matter, or discolours water, or eats
through solid oak. On a ship out at sea,
leagues and leagues away from land, there
falls a shower of impalpable dust, brought
from the great desert by the heated winds,
and close examination proves it to consist of
the remains of dead animalcules. There is
fertilising dust, or pollen, without whose
influence neither grain nor fruit would reward
the cultivator's care. Pollen is very curious
as an object of study, even if we look no
further than its outward form, which varies
greatly in different plants. The rose and the
poppy have pollen like grains of wheat,
magnified into semi-transparent weavers'
shuttles; that of the mallow resembles
cannon-balls covered with spikes; the fuschia
has pollen like bits of half-melted sticky
sugar-candy, with which a small quantity of
horse-hair has become entangled; the
passion-flower has pollen-grains resembling
Chinese carved ivory balls. Pollen, however,
varies more when dry than when moist; for
the effect of the imbibition of fluid, which
usually takes place when the pollen is placed
in contact with it, is to soften down
angularities, and to bring the cell nearer to the
typical sphere. Besides the extraordinary
markings and inequalities of their surface,
most pollen-grains have what appear to be
pores, or slits, in their outer coat, varying in
number in different species, through which
the inner coat protrudes itself, when the bulk
of its contents has been increased by absorption.
Sometimes the pores are covered by
little disc-like pieces, or lids, which fall off
when that wonderful phenomenon occurs—
the protrusion of the pollen tube. This
action takes place naturally, when the
pollen-grains fall upon the surface of the stigma,
which is moistened with a viscid secretion;
and the pollen-tubes, at first mere protrusions
of the inner coat of their cell, insinuating
themselves between the loosely-packed
cells of the stigma, grow downward through
the style, sometimes even to the length of
several inches, until they reach the ovarium.
The first change—namely, the protrusion of
the inner membrane through the pores of the
exterior, may be made to take place artificially,
by moistening the pollen with water, thin
syrup, or dilute acids (different kinds of
pollen-grains requiring a diiferent mode of
treatment), but the subsequent extension by
growth will take place only under the natural
conditions. These latter facts, however, belong
rather to the botanist than the microscopist.
Pollen, for winter observation, may be stored
and mounted during the season of flowers.

Another interesting class of objects, slightly
assimilating in form to pollen-grains, but
visible with instruments of much lower power,
are the eggs of insects. If we fancy them to
be like bird's eggs, universally oval and
smooth, as if cast in moulds of the same
pattern, though differing in size—we mistake
greatly. Egg-cups, wherein to eat the eggs
of insects, must be quite a fancy article of
design, if they are to fit their contents and
answer their purpose. Examine a butterfly's
egg, which you have found sticking to
the back of a leaf, and the chances are, that
it resembles a mince pie, or a tartlet, or an
elaborate sponge-cake. Decorative
confectioners, in search of novelty, would glean
valuable hints from insect's eggs, especially
from those of butterflies and moths. The
silk-worm's egg would make a very pretty
pudding-shape; and I should be delighted to
see a box of sweet biscuits modelled after
the eggs of the peacock butterfly, who
deposits her future progeny on nettle-leaves.
The flea lays a pretty little white egg; the
bug's egg is like a circular game-pie with a
standing crust, the lid of which is lifted when
the young one makes its exit after hatching.
The blow-fly's egg is like a white cucumber
with longitudinal stripes. The shells, or skins,
of insects' eggs are also extremely curious
when emptied of their contents. The eggs
themselves are somewhat troublesome to
preserve, to be looked at; if you leave them
as they are, they are almost sure to hatch;
if you squeeze them between two plates of
glass, they are crushed to a smash and a
mess; and if you boil them, they shrivel up
and spoil. One of these days we shall hit
upon a method of taking accurate casts of
the eggs of insects, so as to publish them,
as we do busts of Victoria. The egglets
well deserve the honour, on account of
their great beauty, the regularity of their
form, the symmetry of the markings on their
surface, and their easy visibility.

To return to our dust. There is a tribe of
organised beings called Diatomaceæ (for
shortness diatoms), the name being derived
from a Greek word which signifies division,
or dissection. They may be Englished as
brittle-worts, because the forms with which
naturalists first became acquainted, grow in
coherent masses that may be readily cut or
broken through. It is disputed whether they
belong to the animal or the vegetable kingdom.
On the one hand, a green colour and a
simplicity of cellular structure are not decisive
proofs of their being plants; on the other hand,
mere motion is no proof that an organised
substance is an animal. Innumerable minute
living creatures are furnished with hair-like
instruments of locomotion, called cilia, from
the Latin word for eyelashes. The rapid