The secrets of Nature often play like an iridescence on the surface, and escape the eye of her worshipper because it is stopped with a microscope. There are mysteries all about us as omnipresent as the movement of the air that lifts the smoke and stirs the leaves, which I cannot find that any philosopher has looked into. Often and deeply have I been impressed with this. For example, there is scarcely, in this world, a commoner or a humbler thing than a tail, yet how multifarious is it in aspect, in construction, and in function, a hundred different things and yet one. Some are of feathers and some of hair, and some bare and skinny; some are long and some are short, some stick up and some hang down, some wag for ever and some are still; the uses that they serve cannot be numbered, but one name covers them all. In the course of evolution they came in with the fishes and went out with man. What was their purpose and mission? What place have they filled in the scheme of things? In short, what is the true inwardness of a tail?

If we try to commence—as scientific method requires—with a definition, we stumble on a key, at the very threshold, which opens the door. For there is no definition of a tail; it is not, in its nature, anything at all. When an animal's fore-legs are fitted on to its backbone at the proper distance from the hind-legs, if any of the backbone remains over, we call it a tail. But it has no purpose; it is a mere surplus, which a tailor (the pun is unavoidable) would have trimmed off. And, lo! in this very negativeness lies the whole secret of the multifarious positiveness of tails. For the absence of special purpose is the chance of general usefulness. The ear must fulfil its purpose or fail entirely, for it can do nothing else. Eyes, nose and mouth, hands and feet, all have their duties; the tail is the unemployed. And if we allow that life has had any hand in the shaping of its own destiny, then the ingenuity of the devices for turning the useless member to account affords one of the most exhilarating subjects of contemplation in the whole panorama of Nature. The fishes fitted it up at once as a twin-propeller, with results so satisfactory that the whale and the porpoise, coming long after, adopted the invention. And be it noted that these last and their kin are now the only ocean-going mammals in the world. The whole tribe of paddle-steamers, such as seals and walruses and dugongs, are only coasters.

Among those beasts that would live on the dry land, the primitive kangaroo could think of nothing better to do with his tail than to make a stool of it. It was a simple thought, but a happy one. Sitting up like a gentleman, he has his hands free to scratch his ribs or twitch his moustache. And when he goes he needs not to put them to the ground, for his great tail so nearly equals the weight of his body that one pair of legs keeps the balance even. And so the kangaroo, almost the lowest of beasts, comes closer to man in his postures than any other. The squirrel also sits up and uses his forepaws for hands, but the squirrel is a sybarite who lies abed in cold weather, and it is every way characteristic of him that he has sent his tail to the furrier and had it done up into a boa, or comforter, at once warm and becoming. See, too, how daintily he lifts it over his back to keep it clean. The rat is a near relation of the squirrel zoologically, but personally he is a gutter-snipe, and you may know that by one look at the tail which he drags after him like a dirty rope. Others of the same family, cleaner, though not more ingenious, like the guinea-pig, have simply dispensed with the encumbrance; but the rabbit has kept enough to make a white cockade, which it hoists when bolting from danger. This is for the guidance of the youngsters. Nearly every kind of deer and antelope carries the same signal, with which, when fleeing through dusky woods, the leader shows the way to the herd and the doe to her fawn.

But of beasts that graze and browse, a large number have turned their tails rather to a use which throws a pathetic light on misery of which we have little experience. We do, indeed, growl at the gnats of a summer evening and think ourselves very ill-used. How little do we know or think of the unintermitted and unabated torment that the most harmless classes of beasts suffer from the bands of beggars which follow them night and day, demanding blood, and will take no refusal. Driven from the brow they settle on the neck, shaken from the neck they dive between the legs, and but for that far-reaching whisk at the end of the tail, they would found a permanent colony on the flanks and defy ejection, like the raiders of Vatersay. Darwin argues that the tail-brush may have materially helped to secure the survival of those species of beasts that possessed it, and no doubt he is right.

The subject is interminable, but we must give a passing glance to some quixotic tails. The opossum scampers up a tree, carrying all her numerous family on her back, and they do not fall off because each infant is securely moored by its own tail to the uplifted tail of its mother. The opossum is a very primitive beast, and so early and useful an invention should, one would think, have been spread widely in after time; but there appears to be some difficulty in developing muscles at the thin end of a long tail, for the animals that have turned it into a grasping organ are few and are widely scattered. Examples are the chameleon among lizards, our own little harvest mouse, and, pre-eminent above all, the American monkeys. To a howler, or spider-monkey, its long tail is a swing and a trapeze in its forest gymnasium. Humboldt saw (he says it) a cluster of them all hanging from a tree by one tail, which proceeded from a Sandow in the middle. I should like to see that too. It is worth noting, by the way, that no old-world monkey has attained to this application of its tail.

Then there is the beaver, whose tail I am convinced is a trowel. I know of no naturalist who has mentioned this, but such negative evidence is of little weight. The beaver, as everybody knows, is a builder, who cuts down trees and piles log upon log until he has raised a solid, domed cabin from seven to twenty feet in diameter, which he then plasters over with clay and straw. If he does not turn round and beat the work smooth with his tail, then I require to know for what purpose he carries that broad, heavy, and hard tool behind him.

How few even among lovers of Nature know why a frog has no tail! The reason-is simply that it used that organ up when it was in want. In early life, as a jolly tadpole, it had a flourishing tail to swim with, and gills for breathing water, and an infantile mouth for taking vegetable nourishment. But when it began to draw near to frog's estate, serious changes were required in its structure to fit it for the life of a land animal. Four tiny legs appeared from under its skin, the gills gave place to air-breathing lungs, and the infant lips to a great, gaping mouth. Now, during this "temporary alteration of the premises" all business was of necessity stopped. The half-fish, half-frog could neither sup like an infant nor eat like a man. In this extremity it fed on its own tail—absorbed it as a camel is said to absorb its hump when travelling in the foodless desert—and so it entered on its new life without one.

Aeronautics have changed the whole perspective of life for birds, as they may for us shortly; so it is no surprise to find that birds have, almost with one consent, converted their tails into steering-gear. A commonplace bird, like a sparrow, scarcely requires this except as a brake when in the act of alighting; but to those birds with which flight is an art and an accomplishment, an expansive forked or rounded tail (there are two patents) is indispensable. We have shot almost all the birds of this sort in our own country, and must travel if we would enjoy that enchanting sight—a pair of eagles or a party of kites gone aloft for a sail when the wind is rising, like skaters to a pond when the ice is bearing. For an hour on end, in restful ease or swift joy, they trace ever-varying circles and spirals against the dark storm-cloud, now rising, now falling, turning and reversing, but never once flapping their widespread pinions.

How is it done? How does the Shamrock sail? Watch, and you will see. When the wind is behind, each stiff quill at the end of the wing stands out by itself and is caught and driven by the blast; but as the bird turns round to face the gale, they all close up and form a continuous mainsail, close-hauled. And all the while the expanded tail is in play, dipping first at one side and then at the other, and turning the trim craft with easy grace "as the governor listeth."

Besides ground birds, like the quail, there are some eccentrics, such as Jenny wren, which have despised their tails, and there are specialists also which require them for other purposes than flying. The woodpecker's tail is quite useless as a rudder, for he is a woodman and has altered and adapted it for a portable stool to rest against as he plies his axe.

But that man must be very blind to the place which birds have taken in the progress of civilisation who can suppose it possible that they should think only of utility in such a question as the disposal of their tails. It is a common notion among those who have acquired some smattering of the theory of evolution that fishes developed into reptiles, reptiles into birds, and birds into beasts; but this is as wrong as it could be. Whatever the genealogy of the beasts may be, they certainly were not evolved from birds, and are in many respects not above them but below them. These are two independent branches of the tree of living forms, as the Greeks and Romans were branches of the stock of Japheth. The beasts may stand for the conquering Romans if you like, but the birds are the Greeks, and have advanced far beyond them in all emotional and artistic sensibility. They worship in the temple of music and beauty. And, like ourselves, they have found no subject so worthy of the highest efforts of art as their own dress. But the clothing of the body must conform more or less to the figure, and so, for a field in which invention and fancy may sport untrammelled, a lady turns to her hat and a bird to its tail. And by both, with equal heroism, every consideration of mere comfort, convenience, health, or safety is swept aside in obedience to the higher aim. Is this only a flippant jocularity, or is there here in very truth some profound law of the mind revealing itself in spheres seemingly so disconnected?

Look at a peacock. Its train, by the way, is a false tail, like the chignon of twenty years ago, or the fringe of the present day; the true tail is under it, and serves no purpose but to support it. Now the peacock lives on the ground, among scrub and brushwood, haunted by jackals and wild cats. They, like soldiers in khaki, reconnoitre him in a uniform expressly designed to elude the eye, but he flaunts a flag resplendent with green and gold. And when his one chance of life lies in springing nimbly from the ground and committing himself to his strong wings, he must lift and carry this ponderous paraphernalia with him. And the terrible Bonelli's eagle is soaring above. But all is risked proudly for the sake of the morning hour in the glade where the ladies assemble. And the peacock is only one of many. Not to mention the lyre bird, the Argus pheasant, the bird of paradise, and other splendid examples, there are common dicky-birds which point the moral and adorn the tail as emphatically.

If the tail is a rudder, where should you look to find it in its most simple and efficient form but among the flycatchers, which make their living by aerial acrobatics after flies? Yet this family seems to be peculiarly prone to the vanity of a stylish tail. The paradise flycatcher flutters two streamers a foot long, like white ribbons, behind it. The fantail could hide behind its own fan. The bee-eater has the two central feathers prolonged and pointed. The drongos, which are flycatchers in habit, wear their tails very long and deeply forked; and one of them, the racket-tailed drongo, has the two side feathers extended beyond the rest for nearly a foot, and as thin as wires, expanding into a blade at the ends. I have seen nothing in ladies' hats more preposterous. It is vain to object that there can be no proper comparison between tails and hats because the woman chooses her own hat while the bird has to wear what Nature has given it. I know that, but the contention is utterly superficial. What choice has a woman as to the style of her hat? Fashion prescribes for her, and Nature for the birds; that is all the difference. No doubt she acquiesces when theoretically she might rebel. The bird cannot rebel, but does it not acquiesce? Does a lyre bird submit to its tail—wear it under protest, so to speak? Believe me, every bird that has an aesthetic tail knows the fact, and tries to live up to it. We may push the argument even further, for the motmot of Brazil is not content with a ready-made tail, but actually strips the web off the two long side feathers with its own beak, except a little patch at the end, so as to get the pattern which Nature, if one must use the phrase, gave to the racket-tailed drongo. A specimen is exhibited in the hall of the South Kensington Museum.

In this connection I may also say that the shape or colour of a tail is not everything. An observant eye may find much to note in the wearing of them. There is a stylish way of carrying a tail and a slovenly way, and there are coquettish arts for the display of recherche tails. A blackbird and a starling are both tidy birds, and both walk much on the ground, but the one lifts its skirts, while the other, more practical and less fashionable, wears a walking dress and saves itself trouble.

This line of observation leads to a higher, and reveals the most important purpose that tails have served in the economy of beast, bird, and reptile, and, perhaps, even cold-blooded fish. Before the godlike countenance of man appeared on the earth, with its contractile forehead and erectile eyebrows, the answering light of the eye, the expansive nostrils, and subtilely mobile lips; before that the tail was the prime vehicle of emotion and safety-valve of passion. It is a great truth, too often buried in these days under rubbish of materialistic theories, that some way of self-manifestation is a supreme necessity of all sentient life. From the hot centre of thought and feeling the currents rush along the nervous ways and pervade the whole frame, seeking an outlet. But many passages are barred by duty, or fear, or eager purpose. A strong gust of passion may burst all barriers and force its way out at every point, but gentle currents flow along the lines of least resistance and find the idle tail. I do not know a better illustration of this than a cat watching a mouse. The ears are pricked forward, the eyes are fixed on the unsuspecting victim, every muscle of the legs is tense, like a bent bow ready to speed the arrow on its way. But see, the excitement with which the whole body is charged cannot be wholly restrained, and oozes out at the point of the tail.

Every emotion and passion takes this course. The happy kid wags its tail as it runs to its mother, the donkey when it has executed a successful bray, and the dog when it sees its master. At the sight of a rival the dog holds its tail up stiffly, unless, indeed, the rival is a bigger dog than itself, in which case the index goes down quickly between the legs. An elated horse elevates its tail, and so does a duck in the same mood. A lizard preparing to fight another lizard

and the raging lion of fiction lashes its sides with the same nervous instrument.

It would be tedious to dwell on the pretty part which the tail plays in the courtships of sparrows and pigeons, or on the sprightly attitudes by which birds of all sorts let off their spirits when shower and sunshine have overfilled their hearts with gladness. But birds twitch their tails constantly, without meaning anything by it. The ceaseless wagging of a wagtail is a mere habit of cheerfulness, like the twirling of her thumbs by an idle Scotswoman. The long tail is there and something must be done with it. Look at the embarrassment which a nervous young man shows about the disposal of his hands; how he thrusts them into his trouser pockets, hangs them by their thumbs from the arm-holes of his waistcoat, or gives them a walking-stick to play with. I like to imagine what such a fellow would do with a long tail if he had it—how he would wind it round each leg in turn, rub up his back hair, and describe figures on the floor. But no animal so self-conscious as man could bear up long under the nervous strain of having to think continually of its tail. It would die young and the race would become extinct. Perhaps it did.

A final word on the conclusion of the whole matter, for these reflections have a moral. As habit becomes character, so expression hardens into feature. The tail of a sheep grows downwards, but that of a goat upwards, and this is the only infallible outward mark of distinction between the two animals. But it is the permanent record of a long history. The sheep was never anything but sheepish; the goat and its forefathers were pert as kids and insolent when their beards grew. It is useless to inquire why insolence should express itself by an upturned tail until someone can advance a reason why it should express itself in another way.

For proof of the fact you need go no farther than your own dogs. The ancestral wolf, or jackal, hunting and fighting, fearing and hoping, showed every changing mood by the pose of its tail; but a change came when it acquired an assured position of security and importance as the chosen companion of man, so dreaded by all its kith and kin. The tail went up at once and stayed there; when it could go no higher, it curled over. But promotion breeds conceit only in base natures. The greyhound is a gentleman, respectful and self-respecting, and it shows that by the very carriage of its tail. Only a snob at heart, petted and pampered for many generations, could have produced that perfect incarnation of smug self-satisfaction, the pug. Let us take the lesson home. The thoughts on which we let our minds dwell, and the sentiments that we harbour in our hearts, are the chisels with which we are carving out our faces and those of our children's children.