Through a Microscope Part 4

XI.--ON THE BEACH.

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

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

Now if you apply a low power of the microscope, you will find the little forest is made up of a strange animal called _Laomeda geniculata_.

(_Fig. 1._) Each branch of this compound animal terminates and expands into a lovely vase and is the home of a polype. The polype is not a separate individual any more than the end of a growing branch is separate from the tree on which it grows.

[Ill.u.s.tration: LAOMEDA.]

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

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

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

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

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

[Ill.u.s.tration: LARES.]

One of the most comical and amusing creatures of all the zoophyte tribe, is figured and described by Mr. Gosse under the name of _Lar Sabellarum_. He was the first observer of this curious creature; he found it inhabiting the outer edge of the tube of a worm--the Sabella.

So when you are looking for microscopic objects do not overlook any tube that you may see standing above the surface of sand and mud, as it may be surrounded by this singular zoophyte. The tubes usually extend an inch or two above the surface, and about as far below. I have found the tubes surrounded with the creatures, but not in as good condition for investigation as those Mr. Gosse mentions. Mine were too thick and crowded to distinguish clearly. But as Mr. Gosse describes them, they have a most close resemblance to the human figure as they stand erect around the mouth of the tube of Sabella.

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

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

[Ill.u.s.tration: HAND OF BARNACLE.]

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

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

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

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

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

XII.--RHIZOPODS.

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

[Ill.u.s.tration: FIG. 1. AMOEBA PRINCEPS, IN DIFFERENT FORMS.]

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

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

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

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

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

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

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

[Ill.u.s.tration: FIG. 2. TESTACEOUS FORMS OF AMOEBAN RHIZOPODS.]

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

When you are looking for various microscopic objects in pond water you will often see these tiny sh.e.l.ls among the sediment on your slides, and if you will patiently wait a few moments you will soon see delicate, transparent arms slowly pushing out on every side like cautious feelers.

(_Figure 2, Amoeba in Sh.e.l.l._--_Carpenter_, p. 445.)

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

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

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

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

[Ill.u.s.tration: FIG. 3. ROTALIA ORNATA.]

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

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

PART III

A HOME-MADE MICROSCOPE, AND HOW TO USE IT

BY FREDERICK LEROY SARGENT

XIII.--HOW TO SEE A DANDELION.

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

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