PART II

THROUGH A MICROSCOPE

BY MARY TREAT

IX.--THE UTRICULARIA.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

X.--FREE SWIMMING ANIMALCULES.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

XI.--ON THE BEACH.

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

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

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

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

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

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

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

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

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.

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

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

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

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

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

XII.--RHIZOPODS.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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.