The acids in the earthworm's "stomach," acting on the leaves, help make other acids which remain in the soil after it has pa.s.sed through the earthworm's body and help dissolve those fine grains of sand which make your bare feet so gritty when mud dries on them. And, not only that, but this coating of soil lying upon the bed rock hastens its decay; for the earthworm's burrow runs down four to six feet, sometimes farther.

Besides the soil he thus grinds up and fertilizes so well with leaf-mould--what your text-book on agriculture calls "humus"--the earthworm does a lot of useful grinding in connection with the building of his house. He begins, as we do, by digging the cellar; but there he stops, for _his_ house is _all_ cellar! He makes it in two ways: (1) By pushing aside the earth as he advances; (2) by swallowing earth and pa.s.sing it through his body, thus making the little mounds you see on the surface.

THE EARTHWORM SYSTEM AT PANAMA

A principle similar to his swallowing operations is frequently employed in engineering; as in making the Panama Ca.n.a.l, where dredging machinery dug out swamps and pumped the mud through a tube into other swamps to fill them up and help get rid of the mosquitoes.

In pushing the earth away the worm uses the principle of the wedge, stretching out his "nose"--as you have often seen him do when crawling--and poking it into the crevices in the ground; much as the wheat roots poke _their_ little noses through the fertile soil the earthworm makes.

And, as in human engineering and the work of the ant, the earthworm doesn't throw the dirt around carelessly. He casts it out, first on one side and then on the other; using his tail to spread it about neatly.

THE TILING IN THE EARTHWORM'S HOUSE

The walls of the earthworm's house are plastered, too. At first they are made a little larger than his body. Then he coats them with earth, ground very fine, like the clay for making our cups and saucers, and for making the beautiful white tiling on the walls at the stations of a city subway. When this earthworm "porcelain" dries it forms a lining, hard and smooth, which keeps the earthworm's tender body from being scratched as he moves up and down his long hallway. It also enables him to travel faster because it is smooth, and it strengthens the walls.

The burrows which run far down into the ground, as all finally do toward Autumn, end in a little chamber. Into this tiny bedroom the worm retires during the hot, dry days of August and there he spends the Winter--usually with several companions, all sound asleep, packed together for warmth.

AND RUGS ON THE FLOORS!

Sometimes the Summer and Winter residences are quite ambitious, several burrows opening into one large chamber and each tunnel having two, sometimes three, chambers of its own--like a fashionable apartment with its main reception-room, and still more like the central sitting-rooms in Greek and Roman palaces. And the earthworm seems even to have some idea of mosaics, for it is the general practice to pave these chambers with little pebbles about the size of a mustard-seed. This is to help keep the worm's body from the cold ground. In addition to the mosaic floors the earthworms have rugs with lovely leaf patterns like the Oriental rugs that are so highly prized; and, as in the case of genuine Oriental rugs, no two patterns are alike. These rugs are leaves which the earthworm drags into his burrow, not for food but for house furnishing. When used for house furnishing they are placed in the entrance-hall; that is to say, they are used to coat the mouth of the burrow to prevent the worm's body from coming in contact with the ground. The mouth of the burrow, of course, is just where it is coldest at night in the Summer, the time of year when the earthworm spends a great deal of his time in the front of his house. The surface of the earth, you know, cools very rapidly after sunset and the dew on the gra.s.s in the morning is so cold it makes your bare feet ache. The worm requires damp earth around him because he breathes through his skin and must keep it moist, but at the same time he is sensitive to cold.

And to drafts. Ugh!

PEBBLE-FORT DEFENSES AGAINST THE FOE

So he is very careful to keep the front door closed. This he does by stopping it up with leaves, leaf stems, and sticks. He also protects the door with little heaps of smooth round pebbles; but these pebbles are of a larger size than those he uses for paving the floor of his chamber.

Besides helping to keep out drafts these pebbles serve another purpose.

As our ancestors, the cave-builders, barred the door with boulders to keep out bears and other unwelcome callers, so the earthworms are protected by the pebbles, to a certain extent, from one of their enemies--the thousand-legged worm. Because of these little forts, the earthworms can remain with more safety near the doorway and enjoy the warmth of the morning sun. (So we might have reproduced Corot's "Morning" as a kind of landscape the earthworm enjoys!)

II. THE MIND OF THE EARTHWORM

From all of which you can see the earthworm, for what small schooling he gets, is a very bright boy! If we were as bright, according to our opportunities, we would probably have answered long ago such puzzles as the question whether there is really anybody at home in Mars, how to keep stored eggs from tasting of the sh.e.l.l, and other great scientific problems of our day.

WHERE MR. EARTHWORM KEEPS HIS BRAIN

Just as we have little brains in the tips of our fingers, the earthworms have brains in the ends of their "noses." They have neither eyes nor ears, but, like that wonderful girl, Helen Keller, they make up for the lack of these senses, to a remarkable degree, by the development of the sense of touch. They acquire quite a little knowledge of Botany, for example. They not only know that leaves are good to eat, but they know which is the "petiole" and which is the "base." They always drag leaves into their burrows by the smallest ends, because this makes it easier to get them through the door. And it is not by mere instinct that they do this. Supply worms with leaves of different form from those which grow in the region where they live, and they will experiment with them until they find just the best way in which to pull them into the burrows.

After that they will always take hold of them so, without further experiment. That is the majority of them will do this; for earthworms are like other little people--all of them are not equally ambitious or studious.

And the earthworm also knows something about Geometry. Cut paper into little triangles of various shapes and pretend to the worms that they are leaves by scattering them near the mouths of the burrows. Then remove the leaves with which the burrows are stopped. The worms will pull in the slips to close the door and they will--most of them--take hold by the apex of the triangle because that is the narrowest point.

THE EARTHWORM'S TASTE IN MUSIC

So you see the earthworm is a very cultivated country gentleman with his knowledge of Botany and Geometry, and his taste for landscape. But this is not all. He also has opinions about music. There are certain notes that apparently get on his nerves. Put worms in good soil in a flower-pot, and some evening when they are lying outside their burrows set the pot on the piano and strike the note C in the ba.s.s clef.

Instantly they will pull themselves into their burrows. They will do the same thing at the sound of G above the line in the treble clef. Although they cannot hear, they are sensitive to vibrations, and these are carried from the sounding-board of the piano into the pot. They are less sensitive when the pot itself is tapped. The music seems to go right through them.

WHY THE EARLY BIRD GETS THE WORM

Except in rainy weather worms ordinarily come out of their burrows only at night. By early morning they have withdrawn into their holes and lie with their noses close to the surface to get the warmth of the morning sun. Then the early bird gets _them_! The reason a robin c.o.c.ks his head in such a funny way--like a lord with a monocle--just before he captures a worm, is not because he is _listening_, as many people think; for the worm isn't saying a word and he isn't moving, and wouldn't make a bit of noise if he did move. The robin's eyes are on each side of his head and not in the middle of his face like ours, so he must turn his head in order to bring his eye in line with the hole where he sees the tip of Mr. Earthworm's nose.

[Ill.u.s.tration: THREE EARLY BIRDS. FIND THE THIRD

Don't they look happy--these two tow-heads? They are evidently going fishing in the early morning. Another early bird--several of him--that we are saying a good deal about in these pages is to be found in the can. Still another, the one at the bottom of the page, is taking advantage of the earthworm's family habit of warming his "nose" in the early sun rays.]

[Ill.u.s.tration]

And many people also believe that earthworms come down with the rain.

Even park policemen believe it. At least, one said to me, in Central Park:

"In dhry spells ye won't see wan. But let there come a little shower an'

th' walks and the dhrives will be covered wid them; like the fairy stones that fall wid the rain in the ould counthry."

DO EARTHWORMS COME DOWN WITH THE RAIN?

The reason you see so many worms after a rain is that earthworms like moisture, and the rain seems to make them feel particularly good and breed a spirit of adventure. So out of their holes and away they go! A rain is their shower-bath; and you know how a shower-bath makes you feel. The mornings when the earthworms are apt to be thickest are those following a comparatively light rain in early Spring when the worms have recently awakened from their long Winter nap. With the beginning of the rainy season in the Fall, the worms also do a good deal of travelling into foreign lands, but in both Spring and Fall you will usually find more worms after a light shower than after a long, heavy downpour. If the worms were drowned out it would be the other way around, don't you see?

To be sure, you will often find dead worms in shallow pools by the roadside; particularly after Autumn rains. These are sick worms and the chill was too much for them. But it's remarkable how low a temperature a good husky angleworm can stand. A professor in the University of Chicago, near which I live, tells me he has often found the ground in the neighboring park covered with worms after November rains when his hands, and those of the students who were helping him gather them for study, were numb with the cold.

And how much work do you suppose these farmers do in grinding up and fertilizing the soil? In many parts of England the whole of the best land--the vegetable mould--pa.s.ses through their bodies every few years, and they are doing similar work all over the world.

They not only fertilize the earth by mixing it with the leaves they eat and those that decay in their burrows, but their castings help to bury fallen leaves and twigs and dead insects, and they also bring up lower soil to the surface, thus increasing its fertility. And by loosening the soil they let in more air. Remember that roots, like people, must have air.

III. THE MILL OF THE EARTHWORM

For the grinding up of the earth and the leaves, the earthworm has, as I have already said, a little mill that he always carries with him. Do you know what a gold mill is? Well, a gold mill is a mill that grinds up rock and so grinds out the gold. The earthworm's mill, in a manner of speaking, also grinds out gold, for it grinds the little particles of stone in the soil, and this soil grows fields of golden grain.

The earthworm's mill is his gizzard. This gizzard is made and works very much like the gizzard of the chicken. And like the chicken the earthworm swallows little stones to help his digestion. So these stones, too, are ground into soil.

Like the chicken's gizzard the gizzard of the earthworm is lined with a thick, tough membrane, and it has muscles--such muscles! There are two sets of these muscles and they cross each other somewhat like the warp and woof of the cloth in your clothes. The muscles that run lengthwise are not so very strong, for all they have to do is to help the earthworm swallow, but the muscles that run around the gizzard are wonderfully strong. They are about ten times as thick as the other muscles. One of Mr. Earthworm's French biographers[10] calls these muscles "veritable armatures"; that is, freely translated, "veritable hoops of steel."

[10] When you study French, if you want to read this book--like most French works on science it is very interesting--ask for Perrier's "Organization des Lumbricus Terrestris."

I said, in the second paragraph above this, that worms swallow grains of sand and stones to help their digestions, as chickens do. But the earthworm saves time, for he takes the stones with his meals; just as some Englishmen, fat old squires, when they get along in years, or for any other reason are a little weak in their digestive regions--keep pepsin on the table with the pepper and salt.

And--believe it or not--the earthworm actually makes his _own_ millstones sometimes! The chalk in the chalky fluid of the glands that help him digest his meals frequently hardens into little grains in grinding the food. It's almost as if the saliva in our mouths, in addition to acting directly on the food, also made a new set of teeth for us!

Suppose we had a stomach like the earthworm, wouldn't it be fun? We could digest the biggest dinners at Thanksgiving and Christmas and picnics and birthdays. We could even eat apples without waiting for them to get quite ripe. Haven't you done it to your sorrow? And no stomachache and no mince-pie nightmares!