Читать книгу Nature's Teachings - John George Wood - Страница 10

The Net, as used in Hunting and War.—The Seine-net, as used for Fishing.—Also as a means of Hunting.—Net for Elephant-catching.—Steel Net for Military Purposes.—Web of the Garden Spider.—The Casting-net, as used in Fishing.—Also as employed in the Combats of the ancient Circus.—Various Kinds of Casting-nets.—The Argus Star-fish and the Barnacle.—The Rod and Line.—Angling of various Kinds.—The Polynesian as an Angler.—The Angler-fish.—“Playing” a Fish.—The Nemertes and its Mode of Feeding.—Mr. Kingsley’s Account of it.—Power of Elongation and Contraction.—The Cydippe.—Spring-traps.—The Gin, Rat-trap, and Man-trap.—Jaws of Dolphin, Porpoise, and Alligator.—Legs of Phasma.—Baited Traps.—Carnivorous Plants and their Mode of Feeding.—Birdlime.—“Pegging” for Chaffinches.—Curious Mode of Tiger-killing.—Ant-eater and its Mode of Feeding.—The Drosera.—Web of Spider and its Structure.

The Net

ALTHOUGH the Net is but seldom employed for the purposes of general warfare, it was once largely used in individual combats, of which we will presently treat. In hunting, however, especially in fishing, the Net has been in constant use, and is equally valued by savages and the most civilised nations.

To begin with the fisheries. Even among ourselves there are so many varieties of fishing-nets that even to enumerate them would be a work of time. However, they are all based on one of two principles, i.e. the nets which are set and the nets which are thrown.

We will begin with the first.

On the right hand of the illustration, and at the bottom, may be seen a common Seine-net being “shot” in the sea. This form of net is very long in proportion to its width, some of these nets being several miles long. The upper edge of the net is furnished with a series of cork bungs, which maintain it on the surface, while the lower edge has a corresponding set of weights, which keep the net extended like a wall of meshes. Any fish which come against this wall are, of course, arrested, and are generally caught by the gill-covers in their vain attempts to force themselves through the meshes.

We may see representations of fishing with the seine-net in the sculptures and paintings of Egypt and Assyria; and in the Berlin Museum there is a part of an Egyptian seine-net with the leads still upon the lower edge, and the upper edge bearing a number of large pieces of wood, which acted as buoys, and served the same purpose as our corks.

In hunting, this plan has been adopted for many centuries, the upper edge of the net being supported on poles, and the lower fastened to the ground in such a manner as to leave the net hanging in loose folds. While this part of the business is being completed by the servants, the hunters are forming a large semicircle, in which they enclose a number of wild beasts, which they drive into the nets or “toils” by gradually contracting the semicircle. The ancient sculptures give us accounts of nets used in exactly this manner. There are represented the nets rolled up ready for use, and being carried on the shoulders of several attendants, who are bearing them to the field. Then there are the nets set up on their poles, and having enclosed within them a number of wild animals, such as boars and deer.

In various parts of India, hunting with the net is one of the chief amusements of their principal men, and the variety of game driven into the toils is really surprising, and affords a magnificent sight to those who view it for the first time. Even the tiger himself cannot leap over the nets because they are so high, nor force his way through them, because their folds hang so lightly that they offer no resistance to his efforts.

A very simple net on similar principles is used for catching elephants. It is formed of the long creeping plants that fling themselves in tangled masses from tree to tree. These creepers are carefully twisted into a net-like form, without being removed from the trees, and when a sufficient space has been enclosed the elephants are driven into it. Not even their gigantic strength and tons of weight are capable of breaking through a barrier which, apparently slight, is as strong as if it were built of the tree-trunks on which the creepers are hung.

This net is seldom used for military purposes, though I have seen one, which I believe still exists, and would do good service. In one of our largest fortresses there is a subterranean corridor, through which it is desirous that the enemy should not penetrate. One mode of defence consists of a large net made of steel hanging loosely across it. The meshes are about ten inches square, so that the defenders can fire from their loopholes through the meshes, while the assailants, even if they knew of its position, would find that nothing smaller than a field-gun would have any effect on this formidable net.

The natural analogy of the fixed net is evidently the web of the common Garden Spider, or Cross Spider (Epeira diadema), whose beautiful nets we all must have admired, especially when we are wise enough to get up sufficiently early in the morning to see the webs with the dewdrops glittering on them.

Last year there was a wonderful sight. Within a mile of my house there is a long iron fence, which in one night had been covered with the webs of the garden spider. The following morning, though bright, was chilly, so that the dewdrops were untouched. I happened to pass by the fence soon after sunrise, and was greatly struck with the astonishing effects which could be produced with such simple materials as water and web. The dewdrops were set at regular intervals upon the web, so as to produce a definite and beautiful pattern, the whole line of fence looking as if it had been woven in fine lace.

Then, as the fence runs north and south, and the path is on the westward of it, every passenger saw the rays of the rising sun dart through these tiny globules, and convert every one of them into a jewel of ever-changing colours. It seemed a pity that such beauty could but last for an hour or so, or that these exquisite webs should only be used for catching flies.

Next comes the Casting-net in its various forms. This net is mostly circular, and is loaded round the edge with small leaden plummets. It is evident that, if such a net could be laid quite flat upon the water, it would assume a dome-like shape, in consequence of the circumference being heavier than the centre, and would sink to the bottom, enclosing anything which came within its scope.

The difficulty is to place the net in such a manner, and this is accomplished by throwing it in a very peculiar way. The net is gathered in folds upon the shoulder, which it partially envelops. By a sudden jerk the thrower causes it to fly open with a sort of spinning movement, and when well cast it will fall on the water perfectly flat.

After allowing it to sink to the bottom, the fisherman draws it very gently by a cord attached to its middle. As he raises it the weights of the leaded circumference are drawn nearer and nearer together by their own weight, and finally form it into a bag, within which are all the living creatures which it has enclosed.

Though the Casting-net has never been used in warfare, it was one of the favourite implements in gladiatorial combats among the Romans. Two men were opposed to each other; one, called the Retiarius or Netsman, being quite naked, except sometimes a slight covering round the waist, and armed with nothing but a Casting-net and a slight trident, which could not inflict a deadly wound. The other, called the Secutor or Follower, from his mode of fighting, was armed with a visored helmet, a broad metal belt, and armour for the legs and arms. He also carried a shield large enough to protect the upper part of the body, and a sword. It will be seen, therefore, how great was the power of the Casting-net, when it enabled its naked bearer to face such odds of offensive and defensive armour.

When the two met in combat, the Retiarius tried to fling his net over his adversary, and if he succeeded, the fate of the latter was sealed. Entangled in the loose meshes, he could scarcely move his limbs, while the sharp prongs of the long-shafted trident came darting in at every exposed point, and exhausting the man with pain and loss of blood. The trident was in itself so feeble a weapon, that if the Secutor were vanquished and condemned to death by the spectators, his antagonist could not kill him, but had to call another Secutor to act as executioner with his sword.

Should he fail in his cast, the Retiarius drew back his net by the central cord, and took to flight, followed by the Secutor, who tried to wound him before he could re-fold his net upon his shoulder, ready for another cast. It is worthy of notice that in these singular combats the netsman seems generally to have been the victor. A Retiarius with his net is shown in the illustration.

I may mention that our ordinary bird-catchers’ nets, and even the entomologist’s insect-net, are only modifications of the Casting-net.

Now for Nature’s Casting-nets, two examples of which are figured, though there are many more. These two have been selected because they are familiar to all naturalists.

The first is the Argus Star-fish, Basket-urchin, or Sea-basket. The innumerable rays and their subdivisions, amounting to some eighty thousand in number, act as the meshes of the net. All the rays are flexible and under control. When the creature wishes to catch any animal for prey, it throws its tentacles over it, just like the meshes of a net. It then draws the tips of the rays together, just as is done by the circumference of the casting-net, and so encloses its prey effectually.

The next specimen is the net-like apparatus of the common Acorn Barnacles, with which our marine rocks are nearly covered. These curious beings belong to the Crustacea, and the apparatus which is figured on page 89, and popularly called the “fan,” is, in fact, a combination of the legs and their appendages of bristles, &c. When the creature is living and covered with water, the fan is thrust out of the top of the shell, expanded as far as possible, swept through the water, closed, and then drawn back again. With these natural casting-nets the Barnacles feed themselves, for, being fixed to the rock, they could not in any other way supply themselves with food. There are many similar examples in Nature, but these will suffice.

The Rod and Line

That both terrestrial and aquatic nets should have their parallels in Nature is clear enough to all who have ever seen a spider’s web, or watched the “fan” of the barnacle. But that the rod and baited line, as well as the net, should have existed in Nature long before man came on earth, is not so well known. Yet, as we shall presently see, not only is the bait represented in Nature, but even our inventions for “playing” a powerful fish are actually surpassed.

We will begin with the Bait.

In nearly all traps a bait of some kind is required, in order to attract the prey, and when we come from land to attract the dwellers in water to our hooks, it is needful that bait of some kind should be used, were it only to deceive the eye, though not the nostrils or palate, of the fish.

A notable example of the deception is given in the common artificial baits of the present day, which are made to imitate almost any British insect which a fish might be disposed to eat.

Perhaps the best instance of this deception is that which is practised by sundry Polynesian tribes. They have seen that the Coryphene or Dorado, and other similar fish, are in the habit of preying upon the flying-fish, and springing at them when they are tolerably high in the air. So these ingenious semi-savages dress up a hook made of bone, ormer-shell, and other materials, making the body of it into a rudely designed form of a fish. A hole is bored transversely through it at the shoulders, and a bunch of stiff fibres is inserted to represent the wings. Another bunch does duty for the tail.

The imitation bait being thus complete, it is hung to a long and slender bamboo rod, which projects well beyond the stern of a canoe, and is so arranged that the hook is about two feet or so from the surface. The Coryphene, seeing this object skimming along, takes it for a flying-fish, leaps at it, and is caught by the hook. There are in several collections specimens of these ingenious hooks, and I possess one which is made on similar principles, but intended for use in the water, and not in the air. It is, in fact, a “spoon-bait.”

One point of ingenuity must be mentioned, as it really belongs to the principle of the bait. These same savages, having noticed that large sea-birds are in the habit of hovering over the flying-fish, and would probably be seen by the Coryphenes, rig up a very long bamboo rod, tie to its end a large bundle of leaves and fibres, and then fix it in the stern of the boat, the sham bird being hung some twenty feet above the sham fish. There is a refinement of deception here, for which we should scarcely give such savages their due credit.

In Art, then, we bait our hooks either with real or false food, and so attract the fish.

In Nature we have a most accomplished master of the art of baiting, who has the wonderful power of never needing a renewal of his bait. A glance at the left-hand figure of the next illustration will show that I allude to the Angler-fish, sometimes called the Fishing-frog (Lophius piscatorius). This remarkable creature has a most enormous mouth, and comparatively small body. On the top of its head are some curious bones, set just like a ring and staple, so as to move freely in every direction. A figure of this piece of mechanism will be given in a future page. At the end of these bones are little fleshy appendages, which must be very tempting to most fish, which are always looking out for something to eat. As they are being waved about, they look as if they were alive. The fish darts at the supposed morsel, and is at once engulfed in the huge jaws of the Angler-fish, which, but for this remarkable apparatus, would be scarcely able to support existence, as it is but a sluggish swimmer, and yet needs a large supply of food. The illustration, representing on the right hand a fish attracted to a bait, and on the left, the Angler-fish, with its bait-like appendage to the head, speaks for itself.

Passing to the art of Angling with a rod and line, we now arrive at another development.

Supposing a fish to have taken the bait, and to have been firmly hooked, how is it to be landed? The simplest plan is, of course, to have a very thick and strong line which will not break with the weight of any ordinary fish.

This is very well in sea-fishing, where a line made of whip-cord will answer the purpose in most cases. But, in river fishing, we have the fact that the fish are so shy that a linen thread would scare them, and so strong and active, that even whip-cord would not prevent them from breaking the line, or tearing the hook out of their mouths. So the modern angler sets himself to the task of combating both these conditions. In the first place, he makes the last yard or two of his line of “silkworm-gut”—a curious substance made from the silk-vessels of silkworms, and nearly invisible in the water. In the next place, he has a very elastic rod; and, in the third, he has forty or more yards of line, though perhaps only twenty feet are in actual use until the fish is hooked. The remainder of the line is wound upon a winch fixed to the handle of the rod. Thus, when a powerful fish is hooked and tries to escape, the line is gradually let loose, so as to yield to its efforts. When it becomes tired by the gradual strain, the line is again wound in, and in this way a fish which would at the first effort smash rod and line of a novice will, in the hands of an experienced fisherman, be landed as surely as if it were no bigger than a gudgeon.

Nature has in this case also anticipated Art, and surpassed all her powers.

There is a wonderful worm, common on our southern coasts, and bearing, as far as I know, no popular name. It is known to the scientific world as Nemertes Borlasii. It possesses the power of extension and contraction more than any known creature, and uses those powers for the purpose of capturing prey. The fishermen say that this worm can extend itself to a length of ninety feet, and as Mr. Davis found one to measure twenty-two feet, after being immersed in spirits of wine, it is likely that their account may be true, especially as the spirit greatly contracted the animal in point of length.

A most vivid description of this worm is given by C. Kingsley, in his “Glaucus,” and was written before he knew its name.

“Whether we were intruding or not, in turning this stone, we must pay a fine for having done so; for there lies an animal as foul and monstrous to the eye as ‘hydra, gorgon, or chimæra dire,’ and yet so wondrously fitted to its work that we must needs endure for our own instruction to handle and to look at it. Its name I know not (though it lurks here under every stone), and should be glad to know. It seems some very ‘low’ Ascarid or Planarian worm.

“You see it? That black, shiny, knotted lump among the gravel, small enough to be taken up in a dessert spoon. Look now, as it is raised and its coils drawn out. Three feet, six, nine at least; with a capability of seemingly endless expansion; a slimy tape of living caoutchouc, some eighth of an inch in diameter, a dark chocolate black, with paler longitudinal lines.

“Is it alive? It hangs helpless and motionless, a mere velvet string, across the hand. Ask the neighbouring Annelids and the fry of the rock-fishes, or put it into a vase at home, and see. It lies motionless, trailing itself among the gravel; you cannot tell where it begins or ends; it may be a dead strip of seaweed, Himanthalia lorea, perhaps, or Chorda filum, or even a tarred string.

“So thinks the little fish who plays over and over it, till he touches at last what is too surely a head. In an instant a bell-shaped sucker mouth has fastened to his side. In another instant, from one lip, a concave double proboscis, just like a tapir’s (another instance of the repetition of forms), has clasped him like a finger; and now begins the struggle: but in vain. He is being ‘played’ with such a fishing-line as the skill of a Wilson or a Stoddart never could invent; a living line, with elasticity beyond that of the most delicate fly-rod, which follows every lunge, shortening and lengthening, slipping and twining round every piece of gravel and stem of seaweed, with a tiring drag such as no Highland wrist or step could ever bring to bear on salmon or on trout.

“The victim is tired now; and slowly, and yet dexterously, his blind assailant is feeling and shifting along his side, till he reaches one end of him; and then the black lips expand, and slowly and surely the curved finger begins packing him end foremost down into the gullet, where he sinks, inch by inch, till the swelling which marks his place is lost among the coils, and he is probably macerated to a pulp long before he has reached the opposite extremity of his cave of doom.

“Once safe down, the black murderer slowly contracts again into a knotted heap, and lies, like a boa with a stag inside him, motionless and blest.”

The accuracy as well as the pictorial effect of this description cannot be surpassed. The “velvety” feel of the creature is most wonderful, as it slips and slides over and among the fingers, and makes the task of gathering it together appear quite hopeless.

This astonishing worm is drawn on the left hand of the illustration on page 93, so as to show the way in which the body is contracted or relaxed at will. On the other side of the illustration is an angler, armed with all the paraphernalia of his craft, and doing imperfectly that which the Nemertes does with absolute perfection.

A similar property belongs to the long, trailing tentacles of the Cydippe, which is described and figured on page 16. When they come in contact with suitable prey, all struggle is useless, the tentacles contracting or elongating to suit the circumstances, and at last lodging the prey within the body of the Cydippe.

The Spring-trap

We are all familiar with the common Spring-trap, or Gin, as it is sometimes called.

It varies much in form and size, sometimes being square and sometimes round; sometimes small enough to be used as a rat-trap, and sometimes large enough to catch and hold human beings, in which case it was known by the name of man-trap. This latter form is now as illegal as the spring-gun, and though the advertisement “Man-traps and Spring-guns are set in these grounds” is still to be seen, neither one nor the other can be there.

They are all constructed on the same principle, namely, a couple of toothed jaws which are driven together by a spring, when the spring is not controlled by a catch. They are evidently borrowed from actual jaws, the same words being used to signify the movable portions and notches of the trap as are employed to designate the corresponding parts in the real jaw.

In both figures of the accompanying illustration we shall see how exact is the parallel. On the right hand is a common rat-trap, or gin, such as is sold for eightpence, with the jaws wide open, so as to show the teeth. On the left is a sketch of the upper and lower jaws of the Dolphin, in which an exactly analogous structure is to be seen.

The figure on the right hand of the lower illustration shows a man-trap as it appears when closed, the teeth interlocking so as exactly to fit between each other. The same principle is exhibited in the jaws of the Porpoise, which are seen on the left of the illustration. The jaws of an Alligator or Crocodile would have answered the purpose quite as well, inasmuch as their teeth interlock in a similar fashion, but I thought that it would be better to give as examples the jaws of allied animals. The reason for this interlocking is evident. All these creatures feed principally on fish, and this mode of constructing the jaws enables them to secure their prey when once seized.

Another example of such teeth is to be found in the fore-legs of various species of Phasma and Mantis, as may be seen by reference to the illustration. The latter insects are wonderfully fierce and pugnacious, fighting with each other on the least provocation, and feeding mostly on other insects, which they secure in their deeply-toothed fore-legs. They use these legs with wonderful force and rapidity, and it is said that a pair of these insects fighting remind the observer of a duel with sabres.

The Baited Trap

Our space being valuable, we are not able to give many examples of Baited Traps, whether in Art or Nature.

The most familiar example of this trap is the common Mouse-trap, the most ordinary form of which is shown at the right hand of the illustration on page 96. In all the varieties of these traps, whether for mice or rats, the prey is induced to enter by means of some tempting food, and then is secured or killed by the action of the trap. Sometimes these traps are made of considerable size for catching large game, and in Africa are employed in the capture of the leopard, in India for taking both tigers and leopards, and in North America for killing bears.

We have already noticed one instance of a bait in the Angler-fish, described in page 92, but in this case the bait serves only for attraction, and the trap, or mouth, is not acted upon by the prey.

There are, however, many examples in the botanical world, where the plant is directly acted upon by the creature which is to be entrapped, such being known by the now familiar term “Carnivorous Plants.” Of these there is a great variety, but under this head I only figure two of them.

The plant on the right hand is the Venus Fly-trap (Dionea muscipula), which is common in the Carolinas. The leaves of this plant are singularly irritable, and when a fly or other insect alights on the open leaf, it seems to touch a sort of spring, and the two sides of the leaf suddenly collapse and hold the insect in their grasp. The strange point about it is, that not only is the insect caught, but is held until it is quite digested, the process being almost exactly the same as if it had been placed in the stomach of some insect-eating animal.

So carnivorous, indeed, is the Dionea, that plants have been fed with chopped meat laid on the leaves, and have thriven wonderfully. Experiments have been tried with other substances, but the Dionea would have nothing to do with them. The natural irritability of the leaves caused them to contract, but they soon opened and rejected the spurious food.

On the left is the Cephalotus. This plant, instead of catching the insect by the folding of the leaf, secures it by means of a sort of trap-door at the upper end. The insect is attracted by the moisture in the cup, and, as soon as it enters, the trap-door shuts upon it, and confines it until it is digested, when the door opens in readiness to admit more prey.

Birdlime

By a natural transition we pass to those traps which secure their prey by means of adhesive substances.

With us, the material called “birdlime” is usually employed. This is obtained from the bark of the holly, and is of the most singular tenacity. An inexperienced person who touches birdlime is sure to repent it. The horrid stuff clings to the fingers, and the more attempts are made to clear them, the more points of attachment are formed. The novice ought to have dipped his hands in water before he touched the birdlime, and then he might have manipulated it with impunity.

The most familiar mode of using the birdlime is by “pegging” for chaffinches.

In the spring, when the male birds are all in anxious rivalry to find mates, or, having found them, to defend them, the “peggers” go into the fields armed with a pot of birdlime and a stuffed chaffinch set on a peg of wood. At one end of this peg is a sharp iron spike. They also have a “call-bird,” i.e. a chaffinch which has been trained to sing at a given signal.

When the “peggers” hear a chaffinch which is worth taking, they feel as sure of him as if he were in their cage. They take the peg, and stick it into the nearest tree-trunk. Round the decoy they place half-a-dozen twigs which have been smeared with birdlime, and arrange them so that no bird flying at the decoy can avoid touching one of them.

The next point is, to order the call-bird to sing. His song is taken as a personal insult by the chaffinch, which is always madly jealous at this time of year. Seeing the stuffed bird, he takes it for a rival, dashes at it, and touches one of the twigs. It is all over with him, for the more he struggles and flutters, the tighter is he bound by the tenacious cords of the birdlime, and is easily picked up by the “pegger.”

Even the fierce and powerful tiger is taken with this simple, but terrible means of destruction. It is always known by what path a tiger will pass, and upon this path the native hunter lays a number of leaves smeared with birdlime. The tiger treads on one of them, and, cat-like, shakes his paw to rid himself of it. Finding that it will not come off, he rubs his paw on his head, transferring the leaf and lime to his face.

By this time he is in the middle of the leaves, and works himself into a paroxysm of rage and terror, finishing by blinding himself with the leaves that he has rubbed upon his head. The hunters allow him to exhaust his strength by his struggles, and then kill him, or, if possible, capture him alive.

Both these scenes are represented on the right hand of the illustration.

On the left hand are several examples of natural birdlime, if we may use the term. The upper represents the Ant-bear, or Great Ant-eater. This animal feeds in a very curious manner. It goes to an ant-hill, and tears it open with its powerful claws. The ants, of course, rush about in wild confusion. Now, the Ant-eater is provided with a long, cylindrical tongue, which looks very like a huge earth-worm, and which is covered with a tenacious slimy secretion. As the ants run to and fro, they adhere to the tongue, and are swept into the mouth of their destroyer.

Below the Ant-eater is the common Drosera, or Sundew, one of our British carnivorous plants. It captures insects, just as has been narrated of the Dionea. But, instead of the leaf closing upon the insect, it arrests its prey by means of little globules of viscous fluid, which exude from the tips of the hairs with which the surface of the leaf is covered. As soon as the insect touches the hairs, they close over it, bind it down, and keep it there until it is digested. Several species of Drosera are known in England, and are found in wet and marshy places.

Another plant, the Green-winged Meadow Orchis (Orchis morio), has been known to act the part of the Drosera. A fly had contrived to push its head against the viscous fluid of the stigmatic surface, and, not being able to extricate itself, was found sticking there.

Next comes a portion of the web of the common Garden Spider (Epeira diadema). We have already treated of this web as a net, and we will now see how it comes within the present category.

In the web of the spider there are at least two distinct kinds of threads. Those which radiate from the centre to the circumference are strong and smooth, while those which unite them are much slighter, and are covered with tiny globules set at regular intervals. When the web is newly spun, these globules are found to be nearly as tenacious as birdlime, and it is by these means that an insect which falls into the web is arrested, and cannot extricate itself until the spider can seize it. After awhile the globules become dry, refuse to perform their office, and then the spider has to construct another web. So numerous are these globules that, according to Mr. Blackwall’s calculations, an ordinary net contains between eighty and ninety thousand. Below the figure of the web itself are shown the two kinds of thread, the upper bearing the globules, and the lower representing one of the plain radiating threads.