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  THROUGH A MICROSCOPE

  SOMETHING OF THE SCIENCE
  TOGETHER WITH MANY CURIOUS OBSERVATIONS
  INDOOR AND OUT
  AND DIRECTIONS FOR A HOME-MADE MICROSCOPE


  BY
  SAMUEL WELLS, MARY TREAT AND
  FREDERICK LEROY SARGENT



  CHICAGO
  THE INTERSTATE PUBLISHING COMPANY
  BOSTON: 30 FRANKLIN STREET


  COPYRIGHT, 1886,
  BY
  INTERSTATE PUBLISHING COMPANY.




CONTENTS.


CHAPTER.                        PAGE.

I. Through a Microscope             7

II. The Outfit                     14

III. The Objects                   20

IV. Home Experiments               26

V. Cochituate Water                33

VI. Interesting objects            39

VII. The Brickmaker                46

VIII. The Vorticellas              54

IX. The Utricularia                61

X. Free Swimming Animalcules       70

XI. On the Beach                   78

XII. Rizopods                      86

XIII. How to See a Dandelion       97

XIV. How to See a Bumble Bee      107

XV. Some Little Things to See     114




PART I

THROUGH A MICROSCOPE

BY SAMUEL WELLS




THROUGH A MICROSCOPE


I

An object one hundredth of an inch in diameter, or of which it would
take one hundred placed side by side to make an inch, is about the
smallest thing that can be easily seen by the unassisted eye. Take a
piece of card and punch a little hole through it with the point of a
small needle, hold it towards a lamp or a window, and you will see the
light through it.

  [Illustration: FIG. 1.]

This hole will be about the size just mentioned, and you will find that
you can see it best and most distinctly when you hold it at a certain
distance from your eye; and this distance will not be far from ten
inches, unless you are near-sighted. Now bring it towards your eye and
you will find it becomes blurred and indistinct. You will see by this
experiment that you cannot see things distinctly when held too close to
your eye, or in other words, that you cannot bring your eye nearer to an
object than eight or ten inches and see it well at the same time.

You could see things much smaller than one hundredth of an inch if you
could get your eye close enough to them. How can that be done? By a
microscope? yes, but what is that? This name comes from two Greek words
that mean "to see small things;" and a microscope is an instrument by
which your eye can get very close to what you want to see.

To understand this, take out one of your eyes and look at it with the
other one. You see that it is a little round camera; most boys have seen
a camera and some boys can make one. The simplest way to do that is to
take a box, say a cigar box (empty, of course); pull off the cover and
fasten in the place of it a piece of ground glass if you have one: if
not a piece of white letter paper, oiled, will do; bore a hole in the
middle of the bottom with a small gimlet and your camera is done. Point
the bottom with the hole in it out of the window, and throw a piece of
cloth over your head and over the box, as the photographers do, to shut
out the side light, but mind and not cover up the hole; look at the
ground glass (or oiled paper) and you will see things upside down. (Fig.
1.) But what has it to do with my eye? you say. Why, your eye is just
like it, only round, as in fig. 2. And if you hold a doll or anything
else about ten inches in front of the eye you have taken out and look at
the inside of it (the eye, not the doll) just as you look at the ground
glass of your box camera, you will see the doll upside down on the back
of the eye.

But how, do you say, can I see things right side up when they are upside
down in my eye? This is a very good conundrum and it will keep a long
time, till you are about seventy years old and have spare time to sit
down and think about it.

Now you see how your eye is a camera; the pupil is the hole and the
back of the eye, called the retina, is the ground glass.

But you will find that the camera you have just made does not show
things distinctly and beautifully as the photographer's camera does; how
can they be distinct in the eye then?

Because in the photographer's camera, in the hole is a lens, which is a
piece of glass, shaped like a sun glass; and so in your eye just behind
the pupil is a lens, not made of glass, but still almost as transparent
as if it were. In order to see what effect this lens has, take your box
camera, make the hole larger and put a lens in it; one of your magic
lantern lenses will do; and if the lens has the right focus you will see
the images sharp and distinct on your ground glass. The focus probably
will not be just right, so make a paper tube, into which fasten your
lens and slide the tube in and out of the hole until you find the right
focus.

When you have got that right so that you see a boy on the sidewalk
upside down and see his teeth when he laughs, put some small object, the
little doll will do, about three feet in front of your lens, and you
will find the image of it is blurred and indistinct, and that you must
pull your tube out to get the focus on the doll; or if you had another
lens of just the right shape to hold in front of your camera, you would
with that get the focus on the doll.

  [Illustration: FIG. 2.]

Thus you can see how it is with your eye, and why you cannot see things
distinctly held close to it. The lens in the eye can change its shape a
little, so that it will focus objects a mile off, or ten inches off, but
it cannot be pushed in and out like the tube in your camera. You can do
this, however, if you take another lens and hold it outside your eye and
let the light go through that first before it comes to the lens in your
eye, and in this way you can get a focus in your retina, and the outside
lens thus forms a part of that optical instrument called your eye. Does
your grandma know that her spectacles are a part of the cameras that she
calls her eyes?

How is it that a lens bends (refracts is the big word for it) the rays
of light? You will learn by and by. You can see that it does so by a few
experiments with your sun glass or any such lens. Hold it between the
sun and a piece of white paper until the white spot in the centre is as
small as you can make it. You will see that the rest of the lens casts a
shadow although it is all glass; this is because the rays of sunlight
that fall on the lens are all bent towards the centre, and so you have a
small white spot on which is concentrated the light and the heat, and
before you have found out how it is all done, your paper takes fire and
the experiment ends in smoke.

Take another piece of paper, and when the white spot is at its smallest,
measure the distance between the lens and the paper, and you will have
the focal distance of the lens.

You have now found out how to get your eye close to an object and see
something that is very small; this is usually called magnifying it,
because it seems to make it look large. Suppose you have a lens that
will let you see a flea through it held just one inch from it, this lens
is now an addition to your eye, as we measure from the lens. If you had
another flea held ten inches off, so big that it would just be hidden by
the little flea, the one farthest off would be ten times as large as the
near one. (Fig. 3.) In this case it is said that the lens having a focal
length of one inch magnifies ten times, or has a power of ten.

  [Illustration: FIG. 3.]

The shortest usual distance of objects seen distinctly being taken as
ten inches, microscopists have agreed to consider that as the standard
of measurement, and objects seen through a lens are considered magnified
to the size they would have if projected ten inches off, like our little
flea.


II.--THE OUTFIT.

Now that we have got hold of the idea that the eye is an optical
instrument, and that to increase its capacity for seeing small things we
add to it other optical contrivances, making with it one instrument
composed of several parts, let us look at such additions more
particularly.

  [Illustration: FIG. 1.]

  [Illustration: FIG. 2.]

  [Illustration: FIG. 3.--OPEN AND CLOSED.]

One pleasant September afternoon, three gentlemen were strolling along
the banks of the Wissahickon, in Philadelphia's beautiful park, and
stopping now and then to examine some little flower or insect with
pocket lenses, when they discovered that some little boys out for a
holiday were watching their proceedings with a curious and mystified
interest. One of the gentlemen had a pocket microscope with three lenses
of different sizes, as in Fig. 1. Calling the boys up to him he showed
them a little flower magnified. They had never dreamed of such a sight,
and their wonder and amazement were as great as if they suddenly beheld
a new world. You will be as surprised as they were when you take your
first peep, but you must learn to see such things _by yourselves_. The
first thing you need is a simple microscope, that is, one with a single
lens, small enough to be carried in the pocket. There are different
forms and sizes of such microscopes, varying in quality and price. Those
like the one just mentioned are made with from one to four lenses each,
and are perhaps the most generally useful. Then there is the Coddington
lens (Fig. 2) which is still more compact; and it is sometimes made in
the form of Fig. 3. It has a very short focus, and is not, therefore,
very easy to use. Achromatic doublets and triplets are made of two or
more lenses cemented together and mounted in the same style as the
Coddington lens; they are very much better than the Coddington, but are
more expensive.

  [Illustration: FIG. 4.]

  [Illustration: FIG. 5.]

There are several devices for mounting these simple microscopes on
stands so that they can be kept steady and the objects to be examined
placed behind them. One of these is illustrated in Fig. 4. An ingenious
boy with a block of wood for a base, some stout wire and corks, can make
one almost as useful, though not so handsome.

  [Illustration: FIG. 6.]

A more elaborate form is shown in Fig. 5. It has a glass stage to hold
transparent objects, and a brass one for opaque objects, and a mirror
below to reflect light up through transparent objects.

It is much better to use a good simple microscope than a poor and cheap
compound one; be sure and remember this and not be enticed to buy such
an one by any representations as to its great magnifying power.

A compound microscope is one with a tube from four to ten inches long,
an arrangement for holding the object to be looked at, and a mirror
below to reflect light upon or through it. The lenses at the end next
the object are small, and are set in a small brass tube, which is called
an "objective." It screws into the large tube. The lenses at the end of
the large tube next the eye are set in a tube, called the eye-piece,
which slides in and out of the large tube. Different objectives contain
lenses of different sizes according to the magnifying power desired, and
they are named "two inch," "one inch," "half inch," and so on down to
"one seventy-fifth." Eye-pieces are sometimes named "A," "B," "C," but
more properly "two inch," and so on down to "one eighth." There is a
very great variety in the forms of compound microscopes, from the very
simple up to the very elaborate, and the prices vary accordingly. A
simple but useful form is given in Fig. 6.

A great deal of money can be expended on a microscope and the various
instruments made to use with it and which are called "accessory
apparatus"; but it is best not to buy these instruments until you know
just what you want, and not to spend much money at first except under
the advice of a "microscopist."

Some simple things, however, you will need at once, such as a few slips
of glass three inches long and one inch wide, called "glass slides,"
some pieces of very thin glass, called "cover glass," a pair of
tweezers, some needles fastened into pen-holders for handles, and a few
glass tubes commonly called "pipettes," or "dipping tubes." These can be
readily bought, and some of them easily made.

  [Illustration: CATCHING ANIMALCULA WITH A PIPETTE.]


III.--OBJECTS.

As soon as you have a microscope you will begin to look at everything
and anything: dust, crumbs of bread, flour, starch, mosquitoes, flies,
and moth millers in their season; flowers and leaves, cotton, wool, and
silk. But this scattering kind of observation will soon weary you. In
order to get the greatest pleasure and best results from your work, you
must proceed with some system.

  [Illustration: BULL'S EYE LENS.]

There are so many objects visible only through the microscope that life
is not long enough for you to see them all, much less to study them.
Some microscopists devote the time they have for such studies to the
observation of single classes of objects; the physician observes the
various parts of the animal structure, and calls his work "histology;"
the botanist examines the vegetable kingdom; the entomologist, insects;
but in all these departments there are numerous subdivisions. As a guide
to your work, you will find some book on the microscope very useful; the
best one is _The Microscope and its Revelations_, by Dr. William B.
Carpenter.

  [Illustration: MAGNIFIED 50 DIAMETERS.]

  [Illustration: FLY'S EYE--5 DIAMETERS.]

Objects through which you can see light are called "transparent," and
are the easiest to look at with the microscope, because you can lay them
on a glass slide and throw light up through them with your mirror. Thick
objects through which light cannot pass are called "opaque," and are
more difficult to examine, and can only be seen with low powers and a
bright light.

In order to see such objects in the evening, you will need a "bull's
eye" lens mounted on a stand, which you can place beside your microscope
and between the lamp and the stage, condensing the light of the lamp on
the object. (_Fig. 1._) There are other methods of illuminating opaque
objects, but they are expensive and difficult to manage, yet by and by
if you persevere in this delightful occupation you will learn what they
are.

  [Illustration: Scale of Butterfly
  MAGNIFIED 200 DIAMETERS.]

  [Illustration: HEAD OF MOSQUITO. MAGNIFIED 15 DIAMETERS.]

Some persons will expect you to show them a fly as big as a horse; but
you will soon be able to prove to them that you know more about the
matter than they do. With a large hand-lens, you can see a whole fly at
once and magnify it two or three times; but when you put it on the stage
of your compound microscope and try to magnify it still more, you will
find that you can only see a part of it at a time, and the higher the
power you use, the less can you see; in other words, the more you
magnify an object, the smaller is the field of view.

An inch-objective will show the head of an housefly, which in a bright
light is a very beautiful object. No picture can equal the delicacy of
the color of the eyes of a live fly.

  [Illustration: SECTION OF WOOD.
  MAGNIFIED 50 DIAMETERS.]

After a little practise you will be able to separate the different parts
of insects and look at them with higher powers. The moth fly will soon
be on the wing, and your aunt will not call you cruel if you kill and
cut up large numbers of them. Put a little of the dust that comes off
from the wing of a moth on a glass slide, look at it with a high power,
and you will find that each particle of dust is a pretty leaf-like
scale. You have seen in summer the dust on the wings of butterflies;
remember this, and look at this butterfly dust with your microscope.

Flowers and leaves you can always easily obtain; but in looking at them
you must remember what has already been said about "transparent" and
"opaque" objects.

Thin slices or sections of stems, leaves, and portions of flowers, can
be made with a sharp knife, and examined as transparent objects, so that
thus you can observe the internal or cellular structure of the vegetable
kingdom.


IV.--HOME EXPERIMENTS.

  [Illustration: FIG. 1.]

During the cold weather it is not pleasant to make excursions into the
country and search for objects for the microscope; so you will look
about and see what you can find at home; and if you live in Boston,
Cochituate water will invite your inspection. The best way to get at the
minute objects in this or any water that is supplied through pipes, is
to make a bag of cotton cloth, not too fine, well washed in water
without soap, about a foot long, large enough at the top to slip over a
faucet that has a screw on it (like the common kitchen faucet adapted
for a filter), so that it can be tied with a string, and small enough at
the bottom to be tied on to the neck of a small bottle such as is used
for homoeopathic pills. This bag should taper gradually in size from
the top to the bottom. (_Fig. 1._)

  [Illustration: The Water Flea
  FIG. 2. CYCLOPS QUADRICORNIS. MAGNIFIED 20 DIAMETERS.]

  [Illustration: FIG. 3. CANTHOCAMPTUS MINUTUS. 40 DIAMETERS.]

If there is a strong head of water where your faucet is, you must reduce
the pressure by opening other faucets on the same floor, such as those
in the laundry, otherwise many of the small creatures will be crushed in
the interstices of the bag. Now let the water run. The bag will swell
out and the water ooze through its sides, and all objects too small to
pass through it will fall down and settle in the little bottle at the
bottom. When you see that there is a considerable amount of sediment in
the bottle, shut off the water and gently squeeze the bag between your
thumb and forefinger, beginning at the top and moving your hand down
towards the bottle. This movement will cause much of the sediment that
has adhered to the sides of the bag to fall down. Now untie your bottle
and set it aside and let the water run through the bag to clean it. If
you have a filter attached to your kitchen faucet you can get a very
good idea of the solid contents of the water by unscrewing it, or
turning it over if it is made so as to reverse, and letting the sediment
that has collected on it drip into a tumbler, but the bag gives much
better results, as many of the delicate forms that live in the water are
crushed to death on the filter.

  [Illustration: FIG. 4. CHYDORUS SPHOERICUS. 50 DIAMETERS.]

Having got the sediment in either a tumbler or a bottle, you must make
your first observation on it with the naked eye by holding it up to the
light and looking through it. You will find it of a brown color, because
a large part of it consists of particles of earth and decayed vegetable
matter, but you will presently see many little white specks moving about
with a jumping or hopping movement. These are commonly called
"water-fleas," on account of their peculiar movements, but the name is
misleading, as they belong to the crustacea (animals having a shell or
crust like the lobster), and not to the insects.

They are found abundantly in ponds and ditches, and in salt water.
Sometimes they are so abundant in drinking water that has not been
filtered, as to alarm a timid person, but you will find them just as
good to eat raw as they are cooked. The most common of these little
creatures is the _Cyclops Quadricornis_, so called because he has one
eye and four horns. (_Fig. 2._)

This picture represents a female, and she carries her eggs in the two
little black bags that you see fastened on each side of the abdomen. You
will find it very interesting by and by to watch the eggs hatch and see
the little cyclops hop away. When young they do not look much like their
parents; they are rounder and their legs are more prominent. The female
cyclops (the male is comparatively rare) is the most common creature in
Cochituate water, and as it is constantly eating, it helps to purify the
water, and, in its turn, is eaten by the fishes.

In swimming it contracts its four horns and its fringed feet with a
quick movement that throws it forward through the water with a leap.

Its one eye is of a brilliant red, and is a beautiful object under the
microscope. The shell also is sometimes beautifully colored, and is
often transparent, so that the internal organs are plainly visible
through it.

  [Illustration: FIG. 5.]

Another of the family of _Cyclopidæ_ is the _Canthocamptus minutus_
(_fig. 3_), which you see is longer and more tapering in its form than
the _Cyclops Quadricornis_. It is also very common and very active.

_Chydorus Sphoericus_ (_fig. 4_) is a very pretty round form
interesting to study when transparent.

All these and some others with rather hard names are in that division of
the _Crustacea_ called _Entomostraca_, meaning shelled creatures whose
shells are cut and do not cover them all round. On this principle, an
oyster on the half-shell might be called an _Entomostracan_.

Now to catch these lively fellows, you must take a dipping tube and be
patient, and when you have got one in the tube, carefully drop it on the
bottom of the "live-box" (_fig. 5_), and put on the cover. Examine it
first with the lowest power you have. By careful management of the cover
you can catch it between the top and bottom without breaking the shell,
and in this prison you can study it at leisure.


V.--COCHITUATE WATER.

You have read or been told that if you look at a drop of water through a
microscope you will find it full of animalculæ, and showmen will
sometimes exhibit water containing _entomostraca_ hopping about, and
will try to persuade you that all water looks in the same way.

  [Illustration: ROTIFER VULGARIS.]

But this is a common mistake, as you will soon find out for yourselves.
Water such as is commonly used for drinking purposes, whether it comes
from a well, spring, river, or pond, contains but little animal or
vegetable life in proportion to its quantity; you may place drop after
drop under the microscope without finding anything visible, and you can
only tell what is in it by filtering a great deal of it. Water standing
in ditches or pools for a long time, becomes full of growth of various
kinds, and is then so discolored and slimy that no one would think of
drinking it.

  [Illustration: CARAPACE OF ANURÆ STIPITATA.]

Let us return to the little bottle which you filled with Cochituate
filterings last month. Take a little from the bottom with your
dipping-tube; put it in the live box and examine it with a half-inch
objective. You will see many forms that are strange to you, and we will
suppose that the first is that of one of the rotifers. These little
creatures are called by this name because of two Latin words meaning
wheel-carriers, for on their heads they have an arrangement which looks
like a wheel, sometimes in rapid motion.

  [Illustration: FLOSCULARIA ORNATA.]

The most common kind is called _Rotifer vulgaris_ (_fig. 1_), and is a
very interesting and elastic being. Sometimes he is gloomy and draws
himself in so that he looks like a ball; then he will stretch out full
length, and opening his wheel, shoot through the water with great speed.
Again he will attach his tail to some fixed object, and by the aid of
his wheel draw a rapid current of water through his mouth; it is thus
that you can best observe him, and by and by you will discover that the
apparent wheel is only a result of the rapid sweeping movement of the
long hairs or cilia which fringe the opening in the top of the head.
Through this opening the water passes, the rotifer gathers his food from
the current, and the food passes into the mastax, where it is ground by
the masticating apparatus, which is easily seen in motion.

  [Illustration: DINOBRYON TORTULARIA.]

There are several different rotifers found in Cochituate water; among
them the most common is the _Anuræ Stipitata_. (_Fig. 2._) It is like a
turtle, with a shell, or carapace, beautifully ornamented. You will see
plenty of these empty shells, and sometimes you will find one inhabited,
when you will see that the creature has a bright red eye, and several
bundles of cilia, in front of the projecting spires.

One of the families of the rotifers is called _Floscularia_, because it
resembles a flower; it is attached at the base to small plants, or algæ,
and occupies a sheath so transparent that it is hardly visible. One
species is occasionally found in the Cochituate, the _Floscularia
ornata_. (_Fig. 3._) It is a beautiful object, with its elongated
radiating cilia, which remain quiet, and do not vibrate. The specimen
figured has three eggs attached to its stem.

You will find other rotifers in the Cochituate, some formed like vases,
others with long spires, but all graceful and beautiful. The _Dinobryon
Tortularia_ is sometimes very common in this water.

In October, 1881, when the taste of the water was very bad, the
_Dinobryon_ was very abundant, though we do not know that it had
anything to do with the bad taste. You will see by the figure, that it
is like a tree, with an individual of the family at the end of every
branch. Each one has its own organs of existence, although attached to
its brothers by its stem. Each has a bright red eye, and a long slender
whip, called a _flagellum_, with which it lashes the water, and when all
the _flagellæ_ are in motion, the whole tree swims about. The
individuals are very small indeed, and it will take your best objective
to show the _flagellum_.

  [Illustration: VORTICELLA NEBULIFERA.]

Another tree-like group is that of the _Vorticella_, of which you will
sometimes find in the Cochituate, the species _Vorticella nebulifera_.
Each animal is at the top of a stem, and this stem has the peculiar
property of being able to coil up and draw its head down close to the
bottom. This appears to be a defensive movement, for whenever a big ugly
creature comes by, down go the whole family so quickly that your eye
cannot follow the movement. Sometimes they will all bob down when you
tap the stage of the microscope so as to jar them. At a certain period
of its life the animal suddenly leaves its stem, and goes swimming about
with great speed.


VI.--INTERESTING OBJECTS.

  [Illustration: STEPHANODISCUS NIAGARÆ.]

The most beautiful of the small _algæ_ or water plants are the
_Diatomaceæ_ and the _Desmidiaceæ_, sometimes called for brevity diatoms
and desmids. They are remarkable for the geometrical character of their
forms, consisting of circles, triangles and polygons of infinite
variety. They are very small, and cannot be satisfactorily seen with an
objective of less power than a four tenths. The diatoms are found
everywhere in both fresh and salt water, but the desmids live only in
fresh water. One of the most common diatoms in Cochituate water is the
_Stephanodiscus Niagaræ_. (_Fig. 1._) It is in shape like a pill box,
and its sides, which would be called its top and bottom if it were a
pill box, are beautifully ornamented with dots in radiating lines with a
ring of spines near the edge. This circle of spines or thorns explains
its name, _Stephanodiscus_, from the proto-martyr, Saint Stephen. The
name _Niagaræ_ is from Niagara River, where it was found. Like all
diatoms, it contains when alive a yellowish brown matter with small
globules of oil, which is called _endochrome_. The box or shell, called
_pustule_, is of silex or quartz, and is therefore almost
indestructible; and when the diatom dies, sinks to the bottom of the
water. In this way beds of shells of diatoms are sometimes formed of
considerable thickness.

  [Illustration: ASTERIONELLA BLEAKLEYII.]

  [Illustration: TABELLARIA FENESTRATA.]

Under the city of Richmond, Va., there is such a deposit, varying from
ten to twenty feet in depth, and extending for many miles. Some of the
diatoms, especially those shaped like a boat, called _Navicula_, have a
peculiar motion which at one time led observers to think them animals.
No one knows how this motion is produced, and if you can find this
out, you will make a very important discovery. The most common diatom in
Cochituate water is _Asterionella Bleakleyii_. It resembles a star with
rays, or the hub and spokes of a wheel. (_Fig. 2._) This diatom is often
found in abundance in the water supplies of cities. It never forms a
complete circle, but grows into spirals or whorls which easily break up.

  [Illustration: SPONGILLA FLUVIATILIS.]

  [Illustration: DESMIDIUM SWARTZII. FRONT AND SIDE VIEW.]

Another diatom common in Cochituate is _Tabellaria Fenestrata_, which
grows in ribbon-like forms. (_Fig. 3._) The desmids resemble the diatoms
in the geometrical character of their forms, but they have no shell of
silex, and are therefore easily destroyed. They are readily
distinguished at sight by the beautiful green color of the contained
matter. In many of them there is a curious circulation of small
particles, especially in the ends of those of a crescent or new-moon
shape. This circulation can only be seen with a high power. Desmids are
easily found in ponds and ditches; and there are several species in
Cochituate. Among them is _Desmidium Swartzii_ (_fig. 4_), and
_Closterium moniliferum_. (_Fig. 5._) Their beauty depends so much on
color that they do not appear to advantage in the figures. You will find
in examining the filterings of Cochituate water, many objects which have
not been described in these papers, and among them many fragments of
green filaments of the small plants belonging to the _confervæ_ and the
_oscillatoriæ_; sometimes you will find small round opaque forms of
brown or green color, which are probably spores of plants of a larger
growth; sometimes you will see the pollen of pine-trees which has fallen
into the water and looks like three small balls fastened together;
sometimes, though rarely, you may find one of those curious little
creatures called water bears, or _tardigrada_; and you may be fortunate
enough to catch a water spider.

  [Illustration: CLOSTERIUM MONILIFERUM.]

But you will often see the _spiculæ_ of the sponge, called _Spongilla
fluviatilis_. They look like pins of glass, blunt at one end and
pointed at the other, and are sometimes very abundant. You may have
heard that this sponge has been considered the source of the
occasionally bad taste and smell of Cochituate water. When it is alive,
it is not disagreeable, but when it decays it imparts to the water a
very unpleasant taste and odor. It certainly is one cause of the bad
quality of the water, but whether it is entitled to the sole credit is
still open to question.

You can see what it looks like in _fig. 6_. When alive, it is of a
light-green color, but when decayed it becomes brown. It is full of the
_spiculæ_ above described, which serve to stiffen it, but it easily
crumbles and scatters them through the water.

Though the microscope shows us many beautiful and interesting objects,
yet in the present state of our knowledge we cannot ascertain by its use
whether the water we examine is harmless or injurious.


VII.--THE BRICKMAKER.

The microscope reveals so many strange odd-looking water creatures and
plants that we can easily imagine ourselves transported to some new
world. Look at this field of view as seen through the microscope. In the
centre stands a brickmaker. He is a queer little animal, and so small
that he looks like a mere speck to the naked eye, but through the
microscope we see how wonderfully curious and strange a creature he is.
He is no idle, lazy fellow. He is instead a most busy mechanic.

Just now he is building a house out of tiny bricks, and he manufactures
the bricks himself, making them one at a time, and when one is finished
he lays it down carefully by the side of the last, and fastens it firmly
in its place with a kind of cement. The bricks are laid in regular tiers
one above the other.

We find these brickmakers in still water where various water-plants
grow, especially the water-milfoil and bladderwort. They seem to be
social beings. They live in large communities, attaching their houses to
the stems and leaves of the plants so thickly sometimes that they almost
touch one another. They look, to the naked eye, like lines about one
eighth of an inch in length. Sometimes they are very thick on the plants
in New Jersey ponds.

If you take some of the plants and water, and put them in a bottle, you
can carry a large number of the brickmakers home, where you can watch
them at your leisure. Take a glass slide which has a little cup-shaped
hollow to hold a few drops of water, and put a tiny piece of the plant
with the house attached into this hollow and fill it with some of the
water from the bottle. Now cover it with a very thin piece of glass and
lay it over the stage of the microscope, and it is ready to be looked at
and studied. You will look with both eyes, for your microscope is a
binocular--one that has two tubes to look through. The size of the
objects will depend upon the magnifying power you have chosen.

The first thing you see is a dark, brick-colored, cylinder-shaped house
which looks to be about the size of a cigar. The little builder who
lives in this house has been disturbed by the means we have taken to
make his acquaintance; he has stopped work and gone within. But he is so
industrious a fellow that he will not remain within very long. As soon
as it is quite still he will probably come to the door of his house, and
you will see him thrust out two horns. He will move these horns to the
right and left, cautiously feeling all around him. He seems very
cautious indeed. But at last he is satisfied that no enemy is near. Now
he ventures out. He unfolds his wheels.

These wheels are surrounded with a band of _cilia_, or flexible hairs,
which he can put in rapid motion, making the wheels have the appearance
of revolving very fast. This rapid motion of the cilia forms a swift
current in the water; and this current brings tiny particles of various
things to the little mechanic. Some of these particles he uses for food;
of others, he makes brick. They are carried into an opening between the
wheels where you can see them revolving very fast until they are
gathered into a little round, dark-colored pellet. The particles are
probably held together by a sticky secretion made by the builder.

It takes him about three minutes to make a brick. As soon as it is
finished, he bends his head over, takes it from its mould between the
wheels, and lays it down carefully by the side of the last. Then he
raises his head and begins to make another. The tube thus constructed is
quite firm and strong. Sometimes when I have found a long tube, I have
cut off a portion from the top. This can be done, with care, for the
brickmaker drops to the bottom when disturbed. It is very amusing to
watch him repair damages and rebuild. Sometimes I have forced one out of
his tube, but it always soon died. But though industrious, he is so
cautious, or timid, that he is easily frightened, and therefore he is
often interrupted in his work. For instance, like some people that we
know, he is very afraid of snakes. If a harmless little tiny snake comes
wriggling along through the water anywhere near him, he folds his wheels
and drops down into his house as quick as a flash. One day a little boy
was delighted with the fast-revolving wheels. Suddenly, by and by, he
turned toward me with great disgust plainly showing in his face: "He's
gone in, 'fraid of a little snake!" he exclaimed.

  [Illustration: FIGURE 1, BRICKMAKER; 2, CURRENT IN WATER; 3, 4, 5, 6,
  DIATOMS; 7, 8, DESMIDS; 9, ALGÆ; 10, 11, TRICHODA LYNCEUS; 12,
  SNAKE-LIKE LARVA; 13, PART OF PLANT TO WHICH BRICKMAKER IS ATTACHED;
  14, BATRACHOSPERMUM MONILIFORM.]

He is always a great favorite with those who have watched him through
the microscope. I do not know how long they live, but I have kept the
same individuals three months or more. I think no one knows the entire
life-history of any of these little creatures, so here is a grand chance
for any young microscopist to investigate and become famous.

On the left of the brickmaker in our field of view is a delicate,
beautiful plant. Only a small part of it is seen in the engraving. It
has a long, floating stem, thickly set with rosettes of a pearly green
color. To the naked eye it looks like green slime, and is called "frog's
spawn;" but the microscope shows us that it is a lovely plant, and some
wise man has given us a long fine name to call it by if we
choose--_Batrachospermum moniliform_. Let us see if this long name has
any meaning: _Batrachia_, a frog, _spermum_, spawn; ah, after all, only
another name for frog spawn! The other name, _moniliform_, means a
bead-like necklace; and this was given it because the threads that make
the rosettes look like strings of small pearly-green beads.

All of the strange-looking plants and animals that we see in the
microscope are known as well by sight and by name by those who make them
a study, as are the larger animals and plants that we see around us
every day.

A bright little girl once asked me why such long hard names are given to
everything in nature. We told her if there was but one language spoken
in the world there would be no need of using Latin names. But as there
are many languages, it was found necessary to agree upon some system, so
that all peoples of different nations might have the same name for an
animal or plant, and a long time ago all the civilized world agreed to
use Latin names. Thus our little brickmaker is known all over the world
as _Melicerta ringens_.

"A field of view" depends for its interest and variety upon what kind of
water we put under the microscope. In the one here represented, I first
took a tiny spray of plant with a brickmaker's house attached, and laid
it on the hollow glass slide and then used the dipping-tube and brought
up some of the sediment from the bottom of the bottle; this proved to
contain several singular-looking plants and animals shown here.

_Figures_ 3, 4, 5 and 6, are diatoms, and _figures_ 7 and 8 are
desmids. Naturalists formerly placed both diatoms and desmids in the
animal kingdom, but now all agree that the desmids are plants, while
some few still maintain that the diatoms are animals. But the weight of
evidence is on the plant side of the question.

The desmids are wonderfully beautiful plants; the markings and colors
are exquisite. A number of species are found in the sediment of every
swamp and pond.

The diatoms often grow in long ribbon-like masses (_fig. 3_), and then
partially separate, remaining joined together at the angles so as to
form a zigzag chain as seen at _figure 4_. They have the power of moving
through the water, changing their places like animals.

A great variety of forms are found, both diatoms and desmids, many still
undescribed, inviting the young microscopist to study and name them.

_Figures_ 10 and 11 are different forms of a little animal, _Trichoda
lynceus_. It undergoes a great many changes. In some of its stages, it
looks so different from the figures here represented that you would
never dream of its being the same creature.


VIII.--THE VORTICELLAS.

  [Illustration: CARCHESIUM POLYPINUM.]

The tree-vorticellas must ever stand first among all the varied and
beautiful objects which the microscope reveals. A species common in New
England and the Middle States is known scientifically by the name of
_Carchesium Polypinum_. It is impossible to convey a true idea of its
beauty from a dead black and white drawing. To be appreciated it must be
seen in all its living glory--charming little animals resembling
bell-shaped lilies on the ends of lovely transparent stems.

How curious nature is in the microscopic world! Only think of a tree of
living animals! The stems of the tree are jointed, and the little
creatures can sway the branches about and even throw them into a spiral
coil so as to bring themselves near the main stem. This gives them the
appearance of being very polite toward each other; they bow and courtesy
as if preparing for a grand quadrille, and they are decked out in gay
colors, red, green, and yellow. The margins of the little cups are
fringed with hairs, or _cilia_, which they can put in such rapid motion
that it makes a current in the water and brings little particles to
their mouths which they consume as food. They do not accept everything
that comes in the current. They seem to know what they like as well as
the higher animals, and act as if they were vexed with some of the
particles, rejecting and sending them off with a rapid whirling motion.

The largest of these fairy-like trees are visible to the naked eye, but
it will be necessary for a novice in such matters to use a good strong
lens to be able to find them readily. They are attached to plants
growing in water. I have always been most successful in finding them
among the water-milfoil (_Myriophillum_) several species of which grow
in New England and the Middle States. Some of the species are found in
deep water, others in shallow ponds.

The Bladderworts (_Utricularia_) are also good plants to search among.
They grow in similar places. On either of these plants we shall be sure
to find a good many interesting creatures. If we fail to find the tree,
we may secure other species of vorticella, all of which are very
beautiful.

Do you know the _Utricularia_? I will devote the next chapter to these
curious plants, and to the microscopic animals which they capture.

It will take a little practice to learn where and how to collect
material for the microscope. We should not depend too much upon books in
any branch of natural history. To be successful, you must observe for
yourselves, experiment and examine independently, consulting books that
you may name and classify, that you may recognize and name what you
find. If you fail to find specimens in one spot, try another.

You should not fill your collecting bottles more than two thirds full of
water, nor crowd too many plants in them. These little creatures must
have air in order to live, as well as the higher animals.

  [Illustration: FIG. 2.]

The finest tree-vorticellas I ever found were in Florida, in the St.
John's River. These trees were attached to long, floating stems of
_Myriophillum verticillatum_, and were unlike any species that I ever
found at the North. They were very large--in a microscopic
sense--plainly visible to the naked eye, and it took only a moderate
power to bring out their beauty.

_Vorticella nebulifera_ is quite common in swamps and ponds. We find it
attached to a great number of water plants. This species is not built up
in the form of a tree, but it is nevertheless beautiful and graceful.
The delicate, slender stems start from a node, or rounded mass,
sometimes fifty or more of these fairy like creatures in one colony, all
attached to a common centre, swaying about, coiling their delicate
transparent stems, and again uncoiling quick as a flash, apparently
dallying and playing, but never interfering nor becoming entangled one
with another.

The _Stentor_ is another member of the _Vorticellinæ_ family. It is one
of the largest of the infusoria, plainly visible to the naked eye, and
one of the most interesting and curious of all the strange animals in
the microscopic world. It assumes various forms. When swimming, it looks
round and plump (_Fig. 2_), and rushes through the water pell-mell,
knocking the smaller animals right and left, always seeming to be in a
great hurry, unless two friendly ones happen to meet, when they
frequently stop and put their heads together a moment as if exchanging
greetings, then away they sail again, dashing through the water,
capturing and devouring the smaller creatures as they go. And now a
couple meet that are very communicative--two gossips, no doubt! At all
events, they put their heads together and conclude to have a good
sociable time.

And they are sensible enough to know that they cannot stand around loose
in the water or public highway. So they select a cosey spot and fasten
their feet to a plant or some firm object, and stretch out their
footstalks sometimes to a great length, making veritable trumpets of
themselves. (_Fig. 3._)

And who knows what grave matters may be settled during these conclaves?
or perhaps they are only rehearsing gossip, as they have had every
possible chance to see what was going on among their neighbors.

  [Illustration: THE STENTORS.--"VERITABLE TRUMPETS."]

Sometimes one settles down alone near a group of others, and seems to
proclaim in stentorian voice that it is reception day and he is ready to
receive. Or perhaps he is simply a herald as his name indicates, whose
business it is to conduct ceremonies and regulate affairs! At any rate,
though our ears are too dull to catch the voices of these curious beings
of a lower world--so near, and yet in another sense, so far away, it
would be difficult to believe that these animated creatures have no
means of communication and nothing to communicate.




PART II

THROUGH A MICROSCOPE

BY MARY TREAT


IX.--THE UTRICULARIA.

It seems strange that innocent-looking plants should capture and kill
animals; but this is really what the Bladderworts (_Utricularia_) are
all the time doing. They grow in ponds and swamps, some species in deep,
still water, others in shallow ponds.

Fig. 1 shows a portion of the stem of _Utricularia clandestina_, natural
size. The little bladders are so nearly transparent, that on bringing
them under the microscope, or even under a good lens, you can see the
numerous creatures that they have captured, some partly consumed, others
still alive.

The bladders on these curious plants remind one of some of the
_Entomostracans_ which Mr. Wells described in his fourth paper. Look at
_Chydorus sphericus_ for instance, and then at the magnified bladder
(_Fig. 2_) in this article. The branched horns at the mouth or entrance
have very much the appearance of the antennæ of some of the minute
animals, and the stem when it is attached to the main branch may be
likened to a tail. But the way in which they capture and devour the
pretty little creatures that come within their grasp makes them appear,
even more than they look, like wicked animals.

  [Illustration: FIG. 1. PORTION OF A STEM OF UTRICULARIA CLANDESTINA;
  NATURAL SIZE.]

I have found almost every swimming animalculæ with which I am
acquainted, caught in these vegetable traps; and when caught they never
escape. Their entrance is easy enough; there is a sensitive valve at the
mouth of the bladder, which, if they touch it, flies open and draws
them in as quick as a flash. These downward-opening bladders not only
entrap animalculæ, but, more wonderful still, the strong larvæ of
insects. The larvæ most frequently caught are those of the mosquito and
chironomus. Often the mosquito is caught tail first--the entire body
inclosed and the head left sticking out. It always looks as if the
victim might walk or wriggle out, but it never does; and you may be sure
that it never backed in there of its own accord.

You all know how the mosquito larva wriggles in the water, and is known
by the common name of "wriggler," or sometimes inaccurately, "wiggler."
Now just as sure as the tail of this wriggler strikes the mouth of the
bladder, just so sure is he caught--drawn in by some unknown power
quicker than you can speak.

There is yet much to learn about these curious plants. How it is that
the valve or trap can so firmly hold these strong larvæ is still a
mystery. I have seen a mosquito larva caught by the head when the first
joint of the body was too large to be admitted through the entrance of
the bladder, and have patiently watched its frantic efforts to escape,
but it was never released. The more it thrashed about, the tighter grew
the fatal trap until death put an end to its struggles.

The chironomus larva is quite unlike that of the mosquito. The
chironomus has brush-like feet which it can withdraw from sight--a sort
of telescopic arrangement--or extend when it wishes to crawl along the
plants, while the mosquito wriggles and swims.

The chironomus is caught more often even than the mosquito larva. At
certain seasons of the year it is almost impossible to find a bladder
without one or more of these victims entrapped.

They feed on the water plants, and seem to have a special liking for the
long-branched antennæ which grow at the mouth of the bladders, and, all
unconscious of the trap, on, on they go, their sickle-shaped jaws
cutting the antennæ which they eat as they advance, until their heads
reach the mouth of the bladder, when they heedlessly touch the valve and
the trap is sprung and they are drawn within, never more to escape, but
to be slowly devoured.

There is another interesting species of _Utricularia_, the _Purfurea_,
quite different in many particulars from the first. It grows in deep,
still water. The stems are long, sometimes two feet or more in length,
and the branches radiate in every direction, so that one plant often
covers quite a large surface of water. The flowering stems stand above
the water, and each stem bears three or four very pretty violet purple
flowers, and it blossoms nearly all summer.

  [Illustration: FIG. 2. BLADDER OF U. CLANDESTINA MAGNIFIED TWENTY
  DIAMETERS.]

The flowers are about half an inch broad and quite conspicuous. Most of
the other species have yellow flowers.

There are no little thread-like leaves on this species, and the bladders
are on the ends of the little branchlets, and they have no sharp-pointed
antennæ as in the other species; but in their place is an elegant
cluster of transparent glassy-like ornamental appendages. The ornaments
are just above the entrance, and who knows but this is a contrivance set
there to lure unwary creatures into the trap.

One of the most common little creatures that was caught in this trap,
was the _Tardigrada_, or water bear. He looks like a tiny cub, but
unlike his great namesake, he has eight legs, and he frequently slips
out of his old skin and comes out in a new suit.

I often find them crawling in a forest of these plants, peering out of a
thick jungle--now ascending a branch and out on a limb, holding fast
with their long claws, and apparently looking around to see what they
can find.

Now one seems to be attracted to this elegant glassy cluster of
_Utricularia_. At all events he is soon pushing his head among the
delicate stems, then stops a moment, standing perfectly still as if
listening. Perhaps he hears the groans of his dying comrades, but all
unheeding the warning, he steps forward, touches the fatal spring, when
in he goes to perish with his comrades.

  [Illustration: FIG. 3. CHIRONOMUS LARVA: BACK VIEW WITH FEET DRAWN IN
  AND JAWS CLOSED; SIDE VIEW WITH FEET EXTENDED AND JAWS CLOSED.]

Young microscopists may like to know that the _Utricularia_ can be
preserved in the house a long time by putting the stems or sprays in an
open, shallow dish of water where they will grow readily. I have kept
the plants months together in a large glass dish where they looked
charmingly beautiful and were the admiration of all who saw them. It is
very interesting to watch their growth. The ends of the growing sprays
unroll like ferns, and with a magnifying glass you can see the
development of the little bladders, and you may make discoveries--who
knows? I know that for a long time it was a mystery to me how the
bladders captured and imprisoned the little animals. Every day I saw
they were entrapped and never escaped, and I studied and pondered over
the matter a long time, and was so interested and determined to learn
the secret that I spent night after night looking through the
microscope, watching the strange, unwary creatures fall into the trap.

At last I concluded to adopt the following plan: I took sprays of the
plants that I had grown in clear water that contained no animalcules, so
that all the bladders were empty and quite transparent. In another dish
I had put a great many masses of mosquito eggs. Mosquito eggs are found
floating on almost any standing water, in dark, compact masses. In warm
weather they hatch in a few hours. So you can understand how quickly I
could swarm a small vessel of water with the mosquito larvæ by
introducing the eggs where I wished them to hatch. When they were
hatched I put some of the water in which was a large number of the tiny
creatures into the live box with a spray of the plant containing empty
bladders. I placed the box under the microscope and closely watched the
manner of capture. I became certain that in almost every instance the
larvæ were caught tail first. The tail is brush-like, and when it swept
over the door or valve that leads into the bladder, I saw that the door
would immediately fly open and always draw the larva in. I soon became
satisfied that the valve was very sensitive when touched at the right
point, but to this day I cannot tell what the power is that so quickly
draws the creatures within. I earnestly hope that some young
microscopists will yet be able to ferret out the cause of this singular
power.

Those who have read Mr. Darwin's very interesting book on _Insectivorous
Plants_, will have noticed that he says the valve of _Utricularia_ is
not in the least sensitive, and that the little creatures force their
way into the bladders--their heads acting like a wedge. But this is not
the case, as Mr. Darwin himself was convinced some years before his
death. In his usual kind, gracious manner he admitted that he was wrong,
and gracefully says the valve must be sensitive, although he could never
excite any movement. In a letter to me bearing date June 1st, 1875, he
says:

"I have read your article (in _Harpers Magazine_) with the greatest
interest. It certainly appears from your excellent observations that the
valve is sensitive.... I cannot understand why I could never with all my
pains excite any movement. It is pretty clear I am quite wrong about the
head acting like a wedge. The indraught of the living larva is
astonishing."


X.--FREE SWIMMING ANIMALCULES.

The Brickmaker, Floscules, and Vorticellas are quiet peaceable citizens
of the microscopic world, and seem to be impressed with the graver
duties of life; they set up housekeeping and settle down for life moored
to one spot. But there are many others that live a free-and-easy sort of
life--a wandering gypsy kind of an existence, always on the move; and
there is not much satisfaction in trying to follow these rovers if we
wish to make a careful study of their structure.

  [Illustration: SKELETON WATER WHEEL.]

So to be enabled to examine them you will be compelled to imprison them
in the live-box and bring just as much pressure to bear upon them as
they will stand without crushing, which with careful practice you may
soon learn to do. But if you are simply making the acquaintance of these
little creatures for amusement, it is more interesting and satisfactory
to watch them while they are unrestrained, and see the curious feats
they perform.

One of the most amusing of these little animals is the Skeleton
Wheel-bearer (_Dinocharis pocillum_). His portrait is seen at _Figure
1_. He has a long foot consisting of three joints, and these joints are
as perfect as those of our own knees and elbows, and can be moved as
easily forward and sideways, but not backward. The joints and foot are
not covered with any fleshy substance, from which fact--the joints being
so conspicuous--it probably received the name Skeleton. Two long slender
toes extend from the last joint, and from the tips of these the Skeleton
can show us more wonderful feats than any circus performer.

The toes can be widely separated, or brought close together, like a pair
of tongs. Sometimes he stands on the tip of one toe and throws his body
forward, or from side to side with a rapid motion; then straightening
himself up, he stands on the tips of both toes as if posing, remaining
perfectly still for a few moments and giving us an opportunity to take a
good look at his curious body which is encased in a pretty vase-shaped,
three-sided transparent shell. The head extends from the top of the
vase, and is surmounted with the usual cilia, or wheel, which we see
among all the rotifera. When he is tired of posing, away he swims in a
graceful, easy manner, with his long foot straightened out and the toes
brought close together.

You sometimes will find these pretty creatures, especially in
summer-time, very numerous in the sediment at the bottom of your
collecting bottles. Often I have found dead specimens, and very
beautiful objects they sometimes are. Great numbers of tiny scavengers
have completely cleaned out all of the soft parts of the body in a most
neat and perfect manner, leaving the beautiful shell and vertical
column, that runs through it, and the foot and toes, entire and perfect
in all of their parts.

Think of the minuteness of these scavengers--untold numbers of them
preying upon the body of an object invisible to the naked eye; and yet
this body is a mammoth by the side of one of the scavengers! The mind
can scarcely grasp the minuteness of these tiny creatures--creatures
that seem to enjoy existence, eating, and apparently playing and
entertaining each other like the higher animals.

  [Illustration: WHIPTAIL.]

The whiptail (_Mastigocerca carinata_) (_Fig. 2_) is another delicate
pretty little creature, and, like the skeleton, is encased in a glassy
shell. It has a long, tapering, spine-like foot, or, more properly
speaking, a toe which is attached to a very short foot by means of a
flexible joint which allows free motion. You often will find him in
company with the Skeleton, and they seem to vie with each other in
performing strange feats. The Whiptail, if possible, looks even more
comical than the Skeleton when it stands on the tip of its long toe, a
toe which is longer than the entire length of the body, now bending over
and nibbling at the plants, now whisking around as if looking and
inquiring into some passing object, then sailing through the water with
a graceful, easy motion beyond sight.

_Brachionus pala_ is also a lovely creature encased in a delicate
transparent shell. It is considerably larger than the Skeleton or
Whiptail, and is just visible to the unassisted eye. If you drop it in a
phial of clear water and hold it up to the light, you can distinctly see
it gliding through the water like a revolving white speck. A moderate
power of the microscope reveals its beauty. The shell is swelled at the
sides, and narrow at the mouth, and round over the back, while the under
side is flat.

  [Illustration: LARGE ROTIFER.]

Like the Skeleton and Whiptail, the head of the little Brachion is seen
protruding from the upper part of the shell; but instead of one wheel
this charming little creature has two, and nothing can be more lovely
than a sight of these fast revolving wheels, like two beautiful crowns.

The reason the wheel looks so strikingly beautiful in _Brachionus_ is
owing to the long cilia which is longer in this genus than in other
genera of this great family.

The foot of _Brachionus_ is more curious than that of the Skeleton. It
is telescopic, and the little animal has the most perfect control over
it. He can draw it within the body so that it looks like a ball, and
again quickly thrust it out and whisk it around in all directions like a
tail. It has two short toes at the end which can be separated or brought
together at pleasure. And he can firmly anchor himself by the toes and
stretch forward, showing you the great length of the foot. Now he rolls
from side to side without letting go his hold and performs other strange
feats, and all the while the wheels are rapidly revolving, he has
stopped his headlong career through the water and has settled down to
get his supper.

_Fig. 3_ represents one of the largest rotifers with which I am
acquainted. I have never been able to find a description or engraving
of it in any work on microscopy. But it is probably well known to
microscopists, for it has a wide range. I have found it in New
Hampshire, New Jersey and Florida.

You cannot get a true idea of its graceful beauty from the drawing, as
it is represented as it was seen in the live box with sufficient
pressure upon it to keep it from moving, while serving as a model. And
no engraving, however perfect, can give you any idea of its brilliant
transparency and delicate coloring.

The play of the muscles and internal organs are plainly visible, and you
can always tell what he has chosen for dinner. Diatoms and desmids form
a portion of his diet. His mouth is below the wheel. When he is hungry
he anchors himself by his forked tail and sets his wheel in rapid
motion, which makes a powerful current sufficient to bring quite large
objects to his head, frequently too large to admit into the mouth. He
will often repeatedly try to take a desmid entirely too large for his
mouth, and his manoeuvres are quite comical as he whirls it round and
round, nipping it on all sides. You will see by looking at the figure
that everything has to be swallowed or taken within the body before it
reaches the mouth. While the desmid is within the body the rotifer has
control over it sufficient to take it into the mouth if it is of the
right size, but if it is too large he soon becomes disgusted and ejects
it with a sudden movement which sends it whirling rapidly away. And now
he takes a smaller one and his jaws work vigorously a moment or two,
when he swallows it almost entire, and we can plainly see the pretty
markings and brilliant green color after it has passed into the stomach.

This large rotifer is plainly visible to the naked eye, and you will
find it in both shallow and deep ponds, wherever water plants grow,
during the months of July and August.


XI.--ON THE BEACH.

Many of our young people spend the month of August at the seaside, and
if those who wish to learn something of the curious microscopic animals
will stroll along the beach when the tide has receded, until they come
to rocky places and little pools filled with salt water and various
marine plants, they will find a form of animal life quite different from
that in fresh water ponds. These little pools along the rocky coast are
the homes of countless numbers of zoophytes--animals which have a
stronger resemblance to plants and flowers than any we have found in
fresh water.

Look for specimens for microscopic work on the surface of the rocks, on
dead sea shells, and on the sea-weeds. On the sea-weeds you will often
find a white filmy network which to the unassisted eye looks like simple
white threads running and spreading in every direction, and at every
angle of the network a tiny stem shoots up, branching out like a tree
and making a miniature forest.

Now if you apply a low power of the microscope, you will find the little
forest is made up of a strange animal called _Laomeda geniculata_.
(_Fig. 1._) Each branch of this compound animal terminates and expands
into a lovely vase and is the home of a polype. The polype is not a
separate individual any more than the end of a growing branch is
separate from the tree on which it grows.

  [Illustration: LAOMEDA.]

When the creature is hungry he sends out from the margin of the vase
from fifteen to twenty tentacles, ranged around the rim like the petals
of a flower. _Figure 1_ shows one of these expanded polypes as seen
through the microscope.

The tentacles or feelers are fishing rods to bring game to the fleshy
mouth which is protruded from the centre of the vase. A great many such
mouths surrounded with their tentacles are necessary to feed this
singular compound creature.

All that I can tell you of these microscopic animals will be nothing
compared to a study of them with your own eyes, so I will only give you
hints of what you may expect, thereby hoping to create sufficient
interest to induce you to stroll to out-of-the-way places, where you may
find many of Nature's marvellous works. We want more field workers in
every department of Natural History, and especially in microscopy where
unexplored fields are awaiting you.

When the tide has receded, various objects of interest will meet your
eye at every step. Look at that old dead sea shell covered with a rough,
shaggy nap. Ah, as we approach, the shell is moving off! What can it
mean? Why, it means that a hermit crab has set up housekeeping in the
old shell, and he, no doubt, thinks us suspicious characters and wants
none of our company. But we are after microscopic objects now, and this
hermit, interesting as he is, is not to claim our attention to-day. The
rough coat on the outside of the shell is of more interest.

With the aid of a pocket lens you will find it another zoophyte. You
can see the polypes, as thick as they can well stand, rising erect and
straight from the shaggy coat like a miniature field of wheat. With a
higher power you will see that each mouth is surrounded with tentacles
like those of _Laomeda_, but yet it is quite a different looking
creature. If we touch one of these polypes ever so lightly, the great
army immediately close their tentacles, for the same life pervades the
entire colony, and those on the extreme outer edge feel the contact as
quickly as the one we touched.

  [Illustration: LARES.]

One of the most comical and amusing creatures of all the zoophyte tribe,
is figured and described by Mr. Gosse under the name of _Lar
Sabellarum_. He was the first observer of this curious creature; he
found it inhabiting the outer edge of the tube of a worm--the Sabella.
So when you are looking for microscopic objects do not overlook any tube
that you may see standing above the surface of sand and mud, as it may
be surrounded by this singular zoophyte. The tubes usually extend an
inch or two above the surface, and about as far below. I have found the
tubes surrounded with the creatures, but not in as good condition for
investigation as those Mr. Gosse mentions. Mine were too thick and
crowded to distinguish clearly. But as Mr. Gosse describes them, they
have a most close resemblance to the human figure as they stand erect
around the mouth of the tube of Sabella.

A loose network surrounds the top of the tube and the strange forms
spring from the angles of the meshes. The creatures are furnished with
heads, and immediately below the head are two arms. (_Fig. 2._) The head
moves to and fro on the neck, while the arms are tossed wildly about as
if gesticulating in the most earnest manner. Or, as in the wild and
disorderly dances of savages the body sways back and forth while the
arms are thrown upward and downward in a frantic way.

One summer I found a colony standing so thickly together that they did
not show off to very good advantage. Apparently they were like a packed
army of Liliputians, striking out with their arms and struggling with
one another. But when I came to observe them more carefully, I found
they were not interfering with one another at all, but each was intent
on his own business of obtaining a livelihood.

  [Illustration: HAND OF BARNACLE.]

The Sabella which inhabits the tube, is of itself a most attractive
object. Most elegant fringed filaments proceed from the head, and wave
back and forth like a fan, and near the ends of these delicate slender
filaments are little black balls, supposed to be eyes. If they are eyes,
the Sabella has no lack of vision, and this may account for his seeming
watchfulness. He is always on the alert and drops down into his house at
any approach. Only with the utmost caution will you have an opportunity
to leisurely look at his rare beauty.

When for the first time I saw this elegant, beautiful creature rising
out of the tube, and waving its fringed fan-like filaments, I did not
wonder at Mr. Gosse's enthusiasm. Neither was I surprised that he should
be reminded of the old Roman mythology and call the zoophytes which
surround the tube, "Lares," for the rare beauty of Sabella would suggest
the protection of guardian spirits. He says:

"These curious creatures have afforded much entertainment, not only to
myself, but to those scientific friends to whom I have had opportunities
of exhibiting them. When I see them surrounding the mansion of the
Sabella, gazing, as it were, after him as he retreats into his castle,
flinging their wild arms over its entrance, and keeping watch with
untiring vigilance until he reappears, it seems to require no very vivid
fancy to imagine them so many guardian demons; and the Lares of the old
Roman mythology occurring to memory, I described the form under the
scientific appellation of _Lar Sabellarum_. You may, however, if it
pleases you better, call them 'witches dancing round the charmed pot.'"

When the tide is out you will frequently notice barnacles adhering to
the rocks, or to the timbers used in the construction of wharves. Pray
stop and examine them critically and see what admirable fishers they
are. Their fishing-nets are composed of several long, flexible, jointed
fingers, thickly beset with sensitive hairs. When the fisher wants a
meal he thrusts his long hand (_Fig. 3_) out the door of his stone
house; the sensitive fingers quickly tell when they come in contact with
anything good to eat, and they curl over and grasp it and convey it to
the mouth.

These barnacles are wonderful creatures and well worthy your continuous
study. They pass through several stages. When young they are a gay
rolicking set, swimming freely in the water; but as maturity approaches
they settle down in stone houses, never more to rove about, and set up
fishing for a living.


XII.--RHIZOPODS.

Rhizopods are the lowest creatures in the animal kingdom. Some of them
are apparently nothing more than animated protoplasm. Protoplasm
pertains to the first formation of living bodies, whether vegetable or
animal, and it appears to be only a viscid, glutinous, unformed mass of
jelly-like substance, yet these rhizopods seem endowed with something
more than simple life.

  [Illustration: FIG. 1. AMOEBA PRINCEPS, IN DIFFERENT FORMS.]

Let us take the lowest of these lowly creatures, the _amoeba_, or
proteus, which we may find during the summer in almost every fresh water
pond. I cannot describe it, for, like its namesake, it is constantly
changing its form, slipping away from us, as it were, right before our
eyes, and assuming a new shape. As Proteus of old could assume any form,
either plant or animal as he pleased, so our _amoeba_ can assume
various forms at pleasure.

You will remember that Homer introduces Proteus in the fourth book of
the _Odyssey_. He makes him the servant of Neptune, and says his office
was to take care of the seals or sea-calves. And who knows but his
namesake may have some such office among the curious beings of the
microscopic world which is peopled with as many strange creatures as
those we read of in ancient mythology?

We frequently see our proteus adhering to a leaf of some water plant
when it looks like a little ball of jelly; and while we are looking at
it, it pushes out an arm here, and now another there, and still another,
as if feeling for something. (_Fig. 1, Amoeba princeps._) Not finding
anything to its taste, it moves or crawls along with its temporary arms
extended--all the while changing them, throwing one out on this side,
then on that, then contracting and pushing out in another place. It
seems to be actively in search of something. At last it has reached a
moving diatom with one of its long arms, which it immediately wraps
around it, and now the other arms are contracted and the creature
actually folds itself around its dinner! He turns himself outside in,
and makes a temporary stomach, and proceeds to digest the soft parts of
the diatom. After he has extracted all the nourishing part, he squeezes
or pushes out the clear, transparent shell, and starts in search for
something more.

It is not known to a certainty how the _amoebæ_ are produced, but this
much is known: If a portion of the body is detached from the rest, it
does not die, but becomes an independent _amoeba_. If a portion of one
of the arms becomes separated from the main body, it does not seem to
incommode the creature in the least, and the small part soon begins to
extend tiny arms and behave in every way like its parent. And this may
be the only way in which the children of Proteus are made--veritable
children of his own flesh.

How strange it seems that a jelly-like mass of substance without form or
organization should be endowed with life and sufficient sense to go in
search of food and have the power of selection.

Life manifested in the lowest animal or plant is just as wonderful and
hard to understand as that which pervades the higher animals.

Some of the species of the fresh water _amoeba_ live in shells of
various forms and patterns. One which we often see has a little house
made of tiny particles of sand and minute bits of shell soldered
together with a kind of cement which hardens in water; these are vase or
pitcher-shaped and always look rough on the outside.

  [Illustration: FIG. 2. TESTACEOUS FORMS OF AMOEBAN RHIZOPODS.]

We may always know the different species by the forms and patterns of
the shells in which they live. Some have very regular shells and
prettily marked. These are usually rounded or arched on one side and
flat on the other.

When you are looking for various microscopic objects in pond water you
will often see these tiny shells among the sediment on your slides, and
if you will patiently wait a few moments you will soon see delicate,
transparent arms slowly pushing out on every side like cautious feelers.
(_Figure 2, Amoeba in Shell._--_Carpenter_, p. 445.)

But the most beautiful forms, and by far the greatest variety of these
microscopic shells are found in the ocean and in marine deposits. If we
look at the seaweeds which grow on the rocks we may see many white
specks adhering to every part of the plants. With a lens we find the
minute specks are spiral shells of many species belonging to the class
_Foraminifera_, and very closely allied to the _amoeba_. The shells
are of most elegant form and pattern. The large sea-shells which we so
much admire are not half so lovely in form or color as these seen
through a microscope. Some of the living animals and the castles in
which they dwell are crimson in color, others a delicate pink.

Let us take one of these living shells while it clings to the sea-weed
and carefully cut off the smallest portion of the plant to which it
adheres, so as to disturb the occupant as little as possible; and now
place it in the live box with some of the salt water and we shall soon
have a most beautiful sight.

See, the creature is throwing out delicate, transparent threads or
filaments in every direction, like fine-spun glass. How charming it
looks with the beautiful shell in the centre, surrounded by this moving,
filmy halo, and how slowly and cautiously the filaments are extended! He
is not a heedless, reckless creature, rushing into needless danger, but
a quiet, timid citizen. Although he was such a long time throwing out
his misty arms, when he scents danger he withdraws them as quick as a
flash. The least jar of the live-box, or a little wriggling larva--much
too large for him to manage, however--are sufficient to make him take in
all of his lines; but when quiet is restored, they are again stretched
out. And for what purpose are these slender filaments extended? Ah, an
innocent animalcule has become entangled among the shimmering, filmy
threads, and now the threads coalesce, run together like the arms of
_amoeba_, and disappear, and the animalcule is drawn within the walls
of the beautiful castle, and we are left to conjecture the fate of the
little victim. _Figure 3, Rotalia Ornata_--which shows its delicate
filaments extended.

These tiny creatures have been so numerous way back in the early ages of
the world, that entire strata of rocks, several feet in thickness, in
various parts of the world, are made up of their skeletons. The city of
Richmond, Virginia, is built over rocks, composed largely of the minute
fossils of _Diatomaceæ_ intermingled with the _Foraminifera_ and others.

  [Illustration: FIG. 3. ROTALIA ORNATA.]

A single prepared slide of these fossils will afford entertainment for
an entire evening, so great is the diversity of form and so many
hundreds on one slide. The Bahama Islands furnish the finest specimens
of these fossils. The slides can be procured of any large dealer in
optical instruments, or, what is still better, the young microscopist
can soon learn to prepare them for himself, as ample directions are
given in the books on the microscope.

In bidding my young readers adieu I shall not lose entire thought of
them, but often when I am engaged in looking through the microscope, I
shall think and ask myself, "Are they, too, absorbed in this pleasant
work, and how many will become true workers and original investigators
in this great field?" We shall all know in due time, for no earnest
worker in any branch of science can long remain unknown. He will be
found out sooner or later. A devoted student in microscopy will become
so happy over the marvellous creatures and their curious ways that he
cannot keep his pleasure to himself.




PART III

A HOME-MADE MICROSCOPE, AND HOW TO USE IT

BY FREDERICK LEROY SARGENT


XIII.--HOW TO SEE A DANDELION.

A simple microscope, some mounted needles, a sharp knife and a pair of
small forceps, are the only things needed to begin with.

There are many kinds of simple microscopes sold, some of which are of
moderate price and answer every purpose; but if one has a little
mechanical skill the cheapest way is to buy a magnifier and make the
rest of the microscope one's self. What is known as the "bellows
pattern," with three lenses, is one of the best of the cheaper forms of
magnifiers, and is an admirable little instrument.

_Fig. 1_ shows a home-made microscope ready for use. It will be seen
that the main part consists of a wooden box having a hole in the top and
open in front. To the back is attached a cork by means of a piece of
thin metal as shown in _fig. 2_. Through this cord slides a rod on which
slides another cork. A piece of brass wire has one end wound round the
upper cork while the other end projects as an arm at right angles to the
rod, and this projecting end sharpened and upturned, passes through
holes drilled in the handle of the magnifier, and thus supports it. The
lenses are focused, _i. e._ brought to the right distance from the
object viewed, by sliding the cork up and down on the rod.

  [Illustration: FIG. 1.]

The object rests on a piece of glass laid over the hole in the top of
the box. A piece of wood covered with white paper and placed below the
object at an angle of about forty-five degrees answers for a reflector
to illuminate those objects through which the light can pass. The pure
white surface is better for the purpose than a mirror.

  [Illustration: FIG. 2.]

The most delicate part of the construction is making the holes in the
corks for the rod to slide through. This may be done perfectly, however,
by making the holes with a rat-tail file, trying the rod now and then
until it moves just right. The best thing for the rod is a piece of
brass wire one quarter of an inch thick; a lead pencil however is a good
substitute. Before bending the end of the brass wire arm it is well to
heat it red-hot at the point of bending, to take out the temper: as
otherwise it may break. The holes in the handle of the magnifier should
be drilled as near the front as possible and so arranged that when the
magnifier is in position the smallest lens will be near the object.

  [Illustration: FIG. 3.]

The mounted needles are shown in _fig. 3_. One pair of each kind will be
enough to start with. To make one, take a fine needle, break off about a
third, so it will not be too long and springy; then with a pair of
pincers force it into the handle point first, withdraw it and finally
force it in again with the point out. It may be easily bent with the
pincers by first heating it to redness in a flame. When bent, heat it
red once more and plunge quickly into water to re-temper it. Rubbing on
an oil stone may be necessary to remove roughness. Should the handles
show any tendency to split, it would be well to wrap the end tightly
with waxed thread.

The forceps (_fig. 4_) may be purchased either of brass or steel at no
great expense. Although not necessary it is more convenient to have them
curved than straight.

  [Illustration: FIG. 4.]

If the reader will carefully follow the directions given below and
endeavor to see for himself all the parts spoken of, he will probably
have very little difficulty afterward in the use of the instruments just
described; and the enjoyment he will have when he has learned how to
examine little things, will amply repay for careful and persistent
efforts at the start. Get a Dandelion in full bloom and also one that
has gone to seed.

Have the microscope and the other instruments ready for use. The best
place to work is on a table in front of a window where there is plenty
of light, but not the direct rays of the sun.

Now cut the blossom in halves from the stem up. It will be seen that the
stem is hollow and ends above in a cushion-like expansion. From the
upper surface of this grow a number of little flowers, while from the
sides there sprang two rows of little green organs that enclose the
flower cluster like a cup. Remove one of the flowers with the forceps
and place it in a drop of water on the glass stage of the microscope.
Examine with one and one half inch power.[A]

Be careful to get just the focus. You are now ready to see the general
form of the flower. At the base is a little body with roughened sides
and slightly narrowed above (the ovary). Springing from the top of the
ovary are a number of fine bristles (the pappus). Inside the bristles is
a yellow portion, tubular below and flat above (the corolla).
Projecting from the tube of the corolla is a little yellow rod (the top
of the stamens joined together); and coming from among the stamens are
two slender recurved organs (the stigmas).

Now take a mounted needle in each hand and holding one needle on the
flat part of the corolla split open the tubular part with the other. By
keeping the lower part spread open with the needles, you will see that a
number of delicate yellow threads grow from the sides of the corolla and
are connected with the yellow stamen rod. These threads are another part
of the stamens. In the middle of the flower is a single thread-like
organ (the style) which comes from the top of the ovary and passing
through the stamens projects beyond them, divided into two stigmas.

Most of my readers have probably studied enough botany to know the names
of the different parts of a flower, but very likely many of them do not
recognize the parts of the Dandelion flower as looking anything like the
parts of the flower with which they are familiar.

Before proceeding further, therefore let us take a Morning-Glory
flower--which you all know and can easily obtain, or at least some
flower like it--and let us see that the parts of the two correspond.

Commencing in the centre we find in both a pistil, consisting of an
ovary at the base and a stigma at the top and a style between. In the
Dandelion the stigma is split in halves, while in the morning-glory it
is not split but has three little knobs. Around the pistil come the
stamens in each case. Each stamen is composed of two parts: a slender
stem (the filament) and a little sac at the end (the anther) which is
filled with pollen dust. In both cases the filaments grow out of the
sides of the corolla. But while in the Morning-Glory the anthers are
entirely free from one another, in the Dandelion they are joined
together by their sides and form a tube around the style. The corolla in
both cases is all of one piece, but in the Dandelion it is as if the
upper part of the corolla were split open one side and then made flat.
Instead of a green calyx as in the Morning-Glory, the Dandelion has a
number of delicate white bristles. And, finally, in the Morning-Glory
both the calyx and corolla grow out from below the ovary, while in the
Dandelion its calyx of bristles and its corolla issue from above the
ovary. So after all, you will see that corresponding organs are in both,
and the difference between the two flowers is not so great as one might
think at first.

Let the different parts of the Dandelion be examined now more minutely.
First take some of the bristles and examine them with one quarter inch
power. They are not perfectly smooth, but are more or less saw-like on
the edge. With the same power look at other parts of the flower; notice
the hairiness of the stigmas, the pollen grains coming out of the
anthers (some grains may be found on the stigmas) also the roughness of
the ovary and the delicate ribs or veins in the corolla. Examine one of
the seed-like fruits with one and one half inch power. It is a ripened
ovary. Compare the fruit with the ovary of a flower. The nutlet has
become hard, rougher and more strongly ribbed. The narrowed upper part
of the ovary has become much elongated and the pappus is spread out like
an inverted umbrella.

Examine some bristles with one quarter inch power. They show the
saw-like edges much more developed than in the younger bristles of the
flower. We see throughout a beautiful adaptation of every part for
fitting the little parachute to be carried long distances by the wind
and finally to catch on some suitable place in which to sprout.


XIV.--HOW TO SEE A BUMBLE BEE.

You will first need to catch your Bumble Bee. A little chloroform poured
on one will kill it instantly. Make a general examination at the outset
of the insect. The outside of the body is horny and covered thickly with
hairs. On the upper side the hairs are much more numerous than on the
under side. The whole body is divided into three regions: the head,
bearing the feelers and mouth-parts; a middle part (thorax) bearing the
four wings and six legs; and a hind part (abdomen) armed with the sting.

Remove the head and examine with one and one half inch power. At the
sides are two prominent oval bodies (compound eyes) which seem to be
crossed by five lines; near the top of the head, between the compound
eyes, are three little shiny bead-like organs (simple eyes); starting
from about the middle of the face are the two feelers (antennæ) and at
the lower part of the head are the mouth-parts. The sides, top and front
of the head are all covered with hair.

Examine one of the compound eyes with one fourth inch power. The surface
is made up of innumerable little facets, something like a cut diamond.

Cut off a piece of one of the compound eyes, remove some of the black
pigment on the back and examine the piece in a drop of water. Each facet
is a tiny hexagon. Some care is necessary to see them well.

Remove an antenna and examine it with three fourths inch power. It is
thickly covered with minute hairs which give it a velvety appearance.
Count the joints. At the base is the longest joint; at the lower end of
which is a little knob that fits into a socket in the head. The next
joint is quite small while those beyond are much alike.

Scrape the hairs from the face and examine the horny shell with three
fourths inch power. The surface is full of little pits. In the upper
part of the face there is a groove, in the middle of which is one of
the simple eyes. Just below the antennæ sockets is a groove which
extends crosswise a short distance on either side and then bends
downwards to the mouth. The portion of the face bounded by this groove
is called the clypeus. At its lower part is hinged a little oblong piece
(labium) which may be moved up and down with a needle.

Melt a piece of sealing wax on the centre of a slip of glass (taking
care not to break the glass by too sudden heating) and before the wax
hardens press the head into it face downwards.

Examine with one inch power. The hole near the top of the head shows the
position of the neck. The portion of the head around this hole is
destitute of hairs and is hollowed in, to make room for the rounded
front part of the thorax. Below this one there is another cavity which
contains a portion of the mouth parts when they are retracted. At each
side of the mouth in front of the base of the sucking organs, are the
two jaws (mandibles) each with a little tuft of hair on the outer side.
The jaws move freely to and from each other, sideways instead of up and
down as do the jaws of the higher animals. The sucking apparatus
consists of five pieces viz: two outermost pieces each tapering to a
fine point, two, each of which ends in three little joints and one in
the centre which projects beyond the others. It may be necessary to
spread these out with the needle, to see them well.

Separate the thorax from the rest of the body. Scrape off the hairs on
the back. Two principal grooves extend across the back, one near the
front and one near the hind margin. The thorax is composed of three
divisions and these grooves show where they are joined together. The
hind division bears the hind wings and the hind pair of legs; the middle
division, much the largest division of the three, bears the fore wings
and the middle pair of legs; and the foremost division is quite small
and bears only the front pair of legs.

Remove the wings of one side and examine in a drop of water with one and
one half inch power. The wings consist of a shining transparent membrane
strengthened by numerous horny veins running through it. Examine with
one half inch power. The membrane is seen to be covered with minute
hairs and little dots. On the front edge of the hind wing a short
distance from the outer end is a row of hooks. At a corresponding place
on the hind edge of the fore wing there is a thickening or ridge. When
flying, the hooks catch onto the ridge and thus the wings are held
together and act as one large wing.

Examine this grappling apparatus with one fourth inch power and with the
needles hook the wings together and pull them apart. If you look through
the magnifier while you do this you will get a good idea of the form of
the ridge and of how the hooks catch onto it. Remove one of the
forelegs, being sure that none remains attached to the body. Examine
with one and one half inch power. The extremity is armed with two claws;
then come four short joints followed by one about as long as the others
together. All these make up the foot. The next joint above is the shank,
then comes the thigh and then quite a small joint, the lower hip, and
lastly attached to the body is the upper hip.

Remove the last five joints of the foot (the claw part, and the other
four joints) examine with one third inch power. The claws have each a
branch projecting from the inner edge. Between the claws is a little
velvety pad. Each of the small joints is covered with short closely
appressed hairs and from the lower end of each joint project several
spines. Now examine the remaining long joint of the foot attached to the
shank. At the upper end of the inner side is a deep semicircular notch,
the upper portion of which is light colored. Beside the notch is a
peculiarly shaped movable spine which projects from the lower end of the
shank. This queer arrangement is what the bee uses to clean his feelers.
The reader has probably seen the operation performed by a bee or a wasp.
The leg is thrown over the feeler, the latter is grasped at that
particular bend of the leg where the cleansing apparatus is situated and
then drawn through from base to tip; and this is repeated several times
with each feeler.

Examine with one and one half inch power a leg from each of the other
pairs and compare the corresponding parts. They differ chiefly in size
and in the absence of the cleansing apparatus. You cannot fail to
admire the many beautiful forms of the different portions. On the outer
side of the hind shank is a smooth flattish surface destitute of hairs,
excepting a fringe of long ones at the margin. At this place may
sometimes be found a sticky mass of pollen intended for bee-bread.
Examine the abdomen with one and one half inch power. It is composed of
several wings. If some of the hairs are scraped off this will be shown
more clearly. From the hind extremity projects the sting.

We have far from exhausted all the beautiful and interesting points in
the make-up of a Bumble Bee, not even those that may be seen with the
limited powers of a simple microscope; but probably enough has been said
to show the reader that such things are well worthy of study and it is
hoped that enough directions have been given to render future use of the
instruments comparatively free from difficulty.


XV.--SOME LITTLE THINGS TO SEE.

There is no end to the beautiful and wonderful things one can see with
the simple microscope. Only a few of the more attractive and easily
obtained of these are now to be mentioned.

To begin with, there are ever so many pretty flowers to look at. The
asterworts, that is, such flowers as the daisy, aster, golden rod,
dandelion and thistle, are particularly full of beauty. The blossoms are
all made up of a number of little flowers as in the dandelion; but the
shapes and colors and so forth, of the different kinds are exceedingly
various. Some, such as the asters and daisies, have two kinds of flowers
in the same blossom--flowers with strap-shaped corollas (like the
dandelion's) are arranged along the margin of the blossom, while in the
centre are little flowers with star-shaped corollas presenting a much
different appearance. Flowers of many of the Parsley Family, for
example wild carrot, wild parsnip and caraway, are quite odd. Very
pretty flowers are found among the grasses, sedges and common weeds. The
different trees as they bloom in spring--the maples, elms, willows,
poplars, sassafras and hosts of others--all have flowers that are
perfectly lovely. Most of these flowers need to be picked to pieces
under the magnifier to show up their full beauty. The parts of flowers,
both small and large ones, deserve attention. Frequently one meets with
remarkable forms.

Seeds are highly interesting. They are often handsomely marked with
series of pits or projections, grooves or ridges. One meets with many
curious appendages by means of which the seeds are carried off and sown
at a distance from the plant. Some, like the dandelion, have a parachute
attachment; others have wings to catch the wind, and others still are
covered with hooked spines whereby they become attached to the fur of
animals, there to remain until brushed off onto the ground.

Leaves and stems sometimes have on them beautiful hairs and oil-glands.
The wooly covering of common mullein, for example, is made up of
innumerable slender-branched hairs. These show best when a piece of the
leaf broken off is looked at edgewise.

If you examine the fruit-dots on the backs of the different kinds of
ferns you will be surprised to find how pretty they are and of how many
different shapes. Sometimes the fruit is not borne on the back of the
leaf but forms little clusters by themselves, which are sometimes at the
end of the fern, sometimes in the middle, sometimes on a separate stalk.

Mosses, lichens and sea-weeds are well worth looking at.

Early in the summer an exquisite little fungus called "Cluster cups" may
be found on the underside of barberry leaves. Hawthorn and other plants
have handsome fungi on them later in the season.

By observing closely while out in the fields or woods, one sees hovering
about in swarms, myriads of tiny insects. Under the lens some of them
are very odd, others very beautiful. The easiest way to catch these
little midgets, is to wet the palm of the hand and then sweep it among
them, or in the same way use a piece of sticky paper.

The study of the different parts of insects is one of the most
fascinating of the many uses of the Simple microscope. Although all
insects are made up on the same general plan and corresponding organs
occur in most of them, there is an endless variety in the forms under
which we see the different organs and the uses to which they are put.

Take for example the antennæ. In the grasshopper it is long and
threadlike; in the butterflies always ending in a knob; in moths always
tapering to a point, although sometimes threadlike and sometimes much
branched, forming a beautiful plume; in the beetles, sometimes fan-like,
sometimes like a comb; and in other insects assuming still other forms.
Insects' eyes are often colored beautifully. A horse-fly's eyes are
striped. Butterflies' eyes have usually a soft liquid coloring, and
moths' eyes in the dark shine like little fiery beads.

The mouths of insects, such as beetles, grasshoppers and dragon flies,
have strong jaws for biting; flies, bugs, moths and butterflies, have
the mouth-parts transformed into sucking organs, while bees, wasps and
the like have both sucking organs for honey, and biting organs for
leaf-cutting, wood-tearing etc. as we saw was the case in the Bumble
Bee.

Butterflies' wings and moths' wings are covered with little scales of a
variety of shapes. These should be examined attached to the wing to show
their arrangement which is like that of shingles on a roof; but to show
their form they should be looked at when brushed from the wing onto a
piece of glass. Many other peculiarities may be noticed in the wings of
other kinds of insects.

Legs, the same as the other organs, have various forms, markings and
appendages, and so it is with the abdomen and its stings or its
egg-laying apparatus.

The hairs of "Wooly Bears" and caterpillars of that kind are peculiarly
branched.

The four hind pairs of feet in caterpillars are armed each with a row
of little hooks which are used in walking to get a firm hold. The larger
caterpillars show the hooks best.

Sometimes you will find pretty insect eggs on the underside of leaves or
on stems, and also little silken cocoons in similar places. If you are
near a pond-hole, or an old hogshead that collects rain water, you can
find a good many little animals, some of them very frisky--young
mosquitoes or "polywogs," water-fleas, cyclops, little worms, young
dragon-flies and lots of others. When you go to collect them take a
small wide-mouth bottle and, having found a place where there is what
you want, lower your bottle, mouth down, in the midst of them and when
it is well under water turn the mouth upwards. A good many of the
animals will run in with the water. If the first time you do not get
what you want, the second time you may. When you want to examine them at
home you can fish them out with a glass tube and put them in a watch
crystal or on the glass stage of the microscope. In using the tube take
it between the thumb and middle and third fingers, and close the top
with your first finger; then put the lower end of the tube in the water
close to the thing you want to catch; now lift your first finger quickly
and the water will run in the lower end of the tube carrying with it
your little squirmer, unless he has been too quick for you. Close the
top of your tube again and the water will not run out when you remove
the tube, until you lift your finger. Sometimes it takes a good deal of
patience and skill to catch the more agile of the little water animals.
Glass tubes are sold in drug stores for five or ten cents.

If you begin by examining the objects already spoken of, you will while
looking for these be continually discovering for yourselves new objects
possessing new beauties and will soon see that not half the interesting
things you can find have been ever hinted at.

The way to find out about all these things is to go out into the fields
and woods, and form the habit of observing closely what is around you.
Carry your magnifier along and look at this flower, that fern, this
insect, that moss, with different powers of the magnifier; and when you
come across any objects worthy of a more careful examination carry them
home and examine them systematically with Simple microscope, needles,
knife, and so forth. Insects may be kept well in alcohol until winter,
and then careful studies may be made of them.

When using the magnifier in the field, hold it in such a way that the
smallest lens will be nearest the object when the lenses are combined
and be careful not to shade the object with the hand or the hat brim.
Just enough light should fall on the object to make its examination
comfortable for the eyes. If you rest the hand holding the magnifier on
the hand that holds the object, both lens and object can be held much
steadier. When commencing to examine an object it is best to have the
three lenses spread apart, for in this way you can use first the lowest
power then those higher and finally, if you wish to, the three lenses
combined. The dissecting forceps are very handy to have in the field,
both for picking up anything too small for the fingers and for holding
an object to be examined.

A collection of some of these little things preserved and ready for
examination adds greatly to the pleasures of studying them. Of course
all the different kinds of objects cannot be preserved so as to show
their full beauty, but many can be and the following directions will
tell how to make a very good collection:

Seeds, fern-fruit, insects and other opaque objects like these may be
mounted on pasteboard slides. One of these slides consists simply of a
stout piece of pasteboard, having a hole cut in the centre and a piece
of thick paper or cardboard glued on the under side. The object is
attached to the cardboard at the bottom of the hole.

It is best to make a number of these slides at a time. Having procured
some quite thick pasteboard, from old paper boxes, rule lines on the
surface dividing it up into spaces three inches long by one inch wide.
In the centre of each space cut out a hole about half an inch in
diameter. A sharp knife will make a neat square hole or a good round one
may be made with a gun-wad punch. This done, the spaces may be cut apart
with a sharp knife and ruler, along the lines already drawn. Pieces of
cardboard for the backs should be cut a trifle larger than the
pasteboard portion of the slide; after they are glued onto the latter
they may be trimmed down neatly with a pair of scissors. Glue or
mucilage containing glycerine (in the proportion of one or two
teaspoonfuls to an ordinary bottle of mucilage) is the best thing to use
for sticking on the backs. While the slides are drying they should be
either under a weight or in a clamp screwed up tightly, so as to prevent
their twisting out of shape. The mucilage may be prevented from being
squeezed in round the edges of the hole, by taking care when putting it
on not to have it come too near the hole. One or two coats of India Ink
may be painted on the middle of some of the pieces of cardboard, either
before or after they are put onto the slides; and thus a black
background may be obtained for the lighter-colored opaque objects. Many
of the objects will however show best on a white background.

When you have the slides all made, nothing more is needed to mount an
object, than simply to attach it to the bottom of the hole with a
little mucilage and glycerine, or something of that sort, and finally to
write the name of the object on the front part of the slide, and on the
back any desirable notes. A good way to mount such objects as fine seeds
is to put them in the hole loosely and then cover them with a piece of
mica such as will be spoken of presently.

Objects which are to be examined by the light shining through them, for
example a bee's wing or a butterfly's scales, must be mounted on glass
slides.

A glass slide three inches by one is taken, on the centre is placed the
object; over this is laid a thin piece of clear mica three fourths of an
inch square, and this is attached to the glass by pasting narrow strips
of tissue paper around the edges of the cover, partly on the cover and
partly on the slide. Finally the slide is covered with some pretty
colored paper and labeled.

Two pieces of paper are needed to cover each slide. One for the under
part is cut about one and one half by three and one half inches, with a
hole in the centre (round or square). This piece is first pasted on,
the corners being cut and the edges brought over onto the front. The
upper piece, which has a hole in the centre similar to that in the lower
piece, and is cut a trifle larger than the three by one inch slide, is
next pasted on so that the hole will correspond with the one below. The
upper piece of paper is now trimmed down to the slide and the label
attached. Window glass will answer for the slides and you can get any
glazier to cut up a piece for you into the right-sized slips. Mica can
be bought at a stove store, in sheets which may be cut up into three
fourths of an inch squares with a pair of scissors. The mica should be
as clear as you can get it. You will find it handy to have some tissue
paper all mucilaged like postage stamps and cut up in strips the right
size ready to use. The same may be said of the colored paper covers and
the labels.

The dust may be excluded from the uncovered opaque objects by keeping
the mounted slides in small groups, held together by elastic bands. This
will also serve to classify them so that all the insects will be
together, all the seeds, and so on; and the transparent slides may also
be treated in the same way. When an elastic band wears out, it is no
great trouble to replace it.

In working with the Simple microscope there is a fine chance to display
ingenuity, not only in making the instruments and mounting the objects
but in discovering new things to look at and in seeing how much can be
found out about those things which are the most common.




FOOTNOTES:

[A] In these directions "1-1/2 _in._ power" means a lens having
  a focus of 1-1/2 inches; "1/2 _in._ power" means a lens or combination
  of lenses having a focus of 1/2 inch; and so on. All the different
  powers mentioned in the directions may be obtained in the small-sized
  3-lens, bellows form magnifier, either by using the lenses singly or
  combined in different ways. The magnifying power of any single lens or
  simple combination is easily found by dividing 10, by the focus in
  inches. Thus the magnifying power of a 1/2 _in._ lens is found in this
  way: 10÷1/2 = 10×2/1 20. The lens magnifies therefore 20 diameters
  _i. e._ makes an object appear twenty times as long and twenty times as
  broad as it is.




TRANSCRIBER'S NOTES:


Text in italics is surrounded with underscores: _italics_.

Inconsistencies in hyphenation have been retained from the original.

Obvious typographical errors have been corrected as follows:

  Page 8: hundreth changed to hundredth
  Page 11: iustrument changed to instrument
  Page 15: diferent changed to different
  Page 17: he changed to the
  Page 20: wil changed to will
  Page 44: or changed to of
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  Page 86: DIFFRENT changed to DIFFERENT
  Page 125: fouths changed to fourths