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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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._)

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.

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.

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.

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.

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.

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.

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_.

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.

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.

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.

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.

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.

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.

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.

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.

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.