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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 _Cyclopidae_ 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 animalculae, 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 ANURAE 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 _Anurae 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 algae,
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 _flagellae_ 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 NIAGARAE.]
The most beautiful of the small _algae_ or water plants are the
_Diatomaceae_ and the _Desmidiaceae_, 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 Niagarae_. (_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 _Niagarae_ 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 _confervae_ and the
_oscillatoriae_; 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 _spiculae_ 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
_spiculae_ 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, ALGAE; 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 _Vorticellinae_ 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.