FOOTNOTES:

Fig. 1.—Chœrocampa porcellus.Fig. 1.—Chœrocampa porcellus.

I say "generally," because there are some interesting exceptions. The large caterpillars of some of the Elephant Hawkmoths are very conspicuous, and rendered all the more so by the presence of a pair of large eyelike spots. Every one who sees one of these caterpillars is struck by its likeness to a snake, and the so-called "eyes" do much to increase the deception. Moreover, the ring on which they are placed is swollen, and the insect, when in danger, has the habit of retracting its head and front segments, which gives it an additional resemblance to some small reptile. That small birds are, as a matter of fact, afraid of these caterpillars (which, however, I need not say, are in reality altogether harmless) Weismannhas proved by actual experiment. He put one of these caterpillars in a tray, in which he was accustomed to place seed for birds. Soon a little flock of sparrows and other small birds assembled to feed as usual. One of them lit on the edge of this tray, and was just going to hop in, when she spied the caterpillar. Immediately she began bobbing her head up and down in the odd way which some small birds have, but was afraid to go nearer. Another joined her and then another, until at last there was a little company of ten or twelve birds all looking on in astonishment, but not one ventured into the tray; while one bird, which lit in it unsuspectingly, beat a hasty retreat in evident alarm as soon as she perceived the caterpillar. After waiting for some time, Weismann removed it, when the birds soon attacked the seeds. Other caterpillars also are probably protected by their curious resemblance to spotted snakes. One of the large Indian caterpillars has even acquired the power of hissing.

Among perfect insects many resemble closely the substances near which they live. Somemoths are mottled so as to mimic the bark of trees, or moss, or the surface of stones. One beautiful tropical butterfly has a dark wing on which are painted a series of green leaf tips, so that it closely resembles the edge of a pinnate leaf projecting out of shade into sunshine.

The argument is strengthened by those cases in which the protection, or other advantage, is due not merely to colour, but partly also to form. Such are the insects which resemble sticks or leaves. Again, there are cases in which insects mimic others, which, for some reason or other, are less liable to danger. So also many harmless animals mimic others which are poisonous or otherwise well protected. Some butterflies, as Mr. Bates has pointed out, mimic others which are nauseous in taste, and therefore not attacked by birds. In these cases it is generally only the females that are mimetic, and in some cases only a part of them, so that there are two, or even three, kinds of females, the one retaining the normal colouring of the group, the other mimicking another species. Some spidersclosely resemble Ants, and several other insects mimic Wasps or Hornets.

Some reptiles and fish have actually the power of changing the colour of their skin so as to adapt themselves to their surroundings.

Many cases in which the colouring does not at first sight appear to be protective, will on consideration be found to be so. It has, for instance, been objected that sheep are not coloured green; but every mountaineer knows that sheep could not have had a colour more adapted to render them inconspicuous, and that it is almost impossible to distinguish them from the rocks which so constantly crop up on hill sides. Even the brilliant blue of the Kingfisher, which in a museum renders it so conspicuous, in its native haunts, on the contrary, makes it difficult to distinguish from a flash of light upon the water; and the richly-coloured Woodpecker wears the genuine dress of a Forester—the green coat and crimson cap.

It has been found that some brilliantly coloured and conspicuous animals are either nauseous or poisonous. In these cases thebrilliant colour is doubtless a protection by rendering them more unmistakable.

Some animals may delight us especially by their beauty, such as birds or butterflies; others may surprise us by their size, as Elephants and Whales, or the still more marvellous monsters of ancient times; may fascinate us by their exquisite forms, such as many microscopic shells; or compel our reluctant attention by their similarity to us in structure; but none offer more points of interest than those which live in communities. I do not allude to the temporary assemblages of Starlings, Swallows, and other birds at certain times of year, nor even to the permanent associations of animals brought together by common wants in suitable localities, but to regular and more or less organised associations. Such colonies as those of Rooks and Beavers have no doubt interesting revelations and surprises in store for us, but they have not been as yet so much studiedas those of some insects. Among these the Hive Bees, from the beauty and regularity of their cells, from their utility to man, and from the debt we owe them for their unconscious agency in the improvement of flowers, hold a very high place; but they are probably less intelligent, and their relations with other animals and with one another are less complex than in the case of Ants, which have been so well studied by Gould, Huber, Forel, M'Cook, and other naturalists.

The subject is a wide one, for there are at least a thousand species of Ants, no two of which have the same habits. In this country we have rather more than thirty, most of which I have kept in confinement. Their life is comparatively long: I have had working Ants which were seven years old, and a Queen Ant lived in one of my nests for fifteen years. The community consists, in addition to the young, of males, which do no work, of wingless workers, and one or more Queen mothers, who have at first wings, which, however, after one Marriage flight, they throw off, as they never leave the nest again, and in it wings would ofcourse be useless. The workers do not, except occasionally, lay eggs, but carry on all the affairs of the community. Some of them, and especially the younger ones, remain in the nest, excavate chambers and tunnels, and tend the young, which are sorted up according to age, so that my nests often had the appearance of a school, with the children arranged in classes.

In our English Ants the workers in each species are all similar except in size, but among foreign species there are some in which there are two or even more classes of workers, differing greatly not only in size, but also in form. The differences are not the result of age, nor of race, but are adaptations to different functions, the nature of which, however, is not yet well understood. Among the Termites those of one class certainly seem to act as soldiers, and among the true Ants also some have comparatively immense heads and powerful jaws. It is doubtful, however, whether they form a real army. Bates observed that on a foraging expedition the large-headed individuals did not walk in theregular ranks, nor on the return did they carry any of the booty, but marched along at the side, and at tolerably regular intervals, "like subaltern officers in a marching regiment." He is disposed, however, to ascribe to them a much humbler function, namely, to serve merely "as indigestible morsels to the ant thrushes." This, I confess, seems to me improbable.

Solomon was, so far as we yet know, quite correct in describing Ants as having "neither guide, overseer, nor ruler." The so-called Queens are really Mothers. Nevertheless it is true, and it is curious, that the working Ants and Bees always turn their heads towards the Queen. It seems as if the sight of her gave them pleasure. On one occasion, while moving some Ants from one nest into another for exhibition at the Royal Institution, I unfortunately crushed the Queen and killed her. The others, however, did not desert her, or draw her out as they do dead workers, but on the contrary carried her into the new nest, and subsequently into a larger one with which I supplied them, congregating round her forweeks just as if she had been alive. One could hardly help fancying that they were mourning her loss, or hoping anxiously for her recovery.

The Communities of Ants are sometimes very large, numbering even up to 500,000 individuals; and it is a lesson to us, that no one has ever yet seen a quarrel between any two Ants belonging to the same community. On the other hand it must be admitted that they are in hostility, not only with most other insects, including Ants of different species, but even with those of the same species if belonging to different communities. I have over and over again introduced Ants from one of my nests into another nest of the same species, and they were invariably attacked, seized by a leg or an antenna, and dragged out.

It is evident therefore that the Ants of each community all recognise one another, which is very remarkable. But more than this, I several times divided a nest into two halves, and found that even after a separation of a year and nine months they recognisedone another, and were perfectly friendly; while they at once attacked Ants from a different nest, although of the same species.

It has been suggested that the Ants of each nest have some sign or password by which they recognise one another. To test this I made some insensible. First I tried chloroform, but this was fatal to them; and as therefore they were practically dead, I did not consider the test satisfactory. I decided therefore to intoxicate them. This was less easy than I had expected. None of my Ants would voluntarily degrade themselves by getting drunk. However, I got over the difficulty by putting them into whisky for a few moments. I took fifty specimens, twenty-five from one nest and twenty-five from another, made them dead drunk, marked each with a spot of paint, and put them on a table close to where other Ants from one of the nests were feeding. The table was surrounded as usual with a moat of water to prevent them from straying. The Ants which were feeding soon noticed those which I had made drunk. They seemed quiteastonished to find their comrades in such a disgraceful condition, and as much at a loss to know what to do with their drunkards as we are. After a while, however, to cut my story short, they carried them all away: the strangers they took to the edge of the moat and dropped into the water, while they bore their friends home into the nest, where by degrees they slept off the effects of the spirit. Thus it is evident that they know their friends even when incapable of giving any sign or password.

This little experiment also shows that they help comrades in distress. If a Wolf or a Rook be ill or injured, we are told that it is driven away or even killed by its comrades. Not so with Ants. For instance, in one of my nests an unfortunate Ant, in emerging from the chrysalis skin, injured her legs so much that she lay on her back quite helpless. For three months, however, she was carefully fed and tended by the other Ants. In another case an Ant in the same manner had injured her antennæ. I watched her also carefully to see what would happen. For some days she didnot leave the nest. At last one day she ventured outside, and after a while met a stranger Ant of the same species, but belonging to another nest, by whom she was at once attacked. I tried to separate them, but whether by her enemy, or perhaps by my well-meant but clumsy kindness, she was evidently much hurt and lay helplessly on her side. Several other Ants passed her without taking any notice, but soon one came up, examined her carefully with her antennæ, and carried her off tenderly to the nest. No one, I think, who saw it could have denied to that Ant one attribute of humanity, the quality of kindness.

The existence of such communities as those of Ants or Bees implies, no doubt, some power of communication, but the amount is still a matter of doubt. It is well known that if one Bee or Ant discovers a store of food, others soon find their way to it. This, however, does not prove much. It makes all the difference whether they are brought or sent. If they merely accompany on her return a companion who has brought a store of food,it does not imply much. To test this, therefore, I made several experiments. For instance, one cold day my Ants were almost all in their nests. One only was out hunting and about six feet from home. I took a dead bluebottle fly, pinned it on to a piece of cork, and put it down just in front of her. She at once tried to carry off the fly, but to her surprise found it immovable. She tugged and tugged, first one way and then another for about twenty minutes, and then went straight off to the nest. During that time not a single Ant had come out; in fact she was the only Ant of that nest out at the time. She went straight in, but in a few seconds—less than half a minute,—came out again with no less than twelve friends, who trooped off with her, and eventually tore up the dead fly, carrying it off in triumph.

Now the first Ant took nothing home with her; she must therefore somehow have made her friends understand that she had found some food, and wanted them to come and help her to secure it. In all such cases, however, so far as my experience goes, the Ants broughttheir friends, and some of my experiments indicated that they are unable to send them.

Certain species of Ants, again, make slaves of others, as Huber first observed. If a colony of the slave-making Ants is changing the nest, a matter which is left to the discretion of the slaves, the latter carry their mistresses to their new home. Again, if I uncovered one of my nests of the Fuscous Ant (Formica fusca), they all began running about in search of some place of refuge. If now I covered over one small part of the nest, after a while some Ant discovered it. In such a case, however, the brave little insect never remained there, she came out in search of her friends, and the first one she met she took up in her jaws, threw over her shoulder (their way of carrying friends), and took into the covered part; then both came out again, found two more friends and brought them in, the same manœuvre being repeated until the whole community was in a place of safety. This I think says much for their public spirit, but seems to prove that, in F. fusca at least, the powers of communication are but limited.

One kind of slave-making Ant has become so completely dependent on their slaves, that even if provided with food they will die of hunger, unless there is a slave to put it into their mouth. I found, however, that they would thrive very well if supplied with a slave for an hour or so once a week to clean and feed them.

But in many cases the community does not consist of Ants only. They have domestic animals, and indeed it is not going too far to say that they have domesticated more animals than we have. Of these the most important are Aphides. Some species keep Aphides on trees and bushes, others collect root-feeding Aphides into their nests. They serve as cows to the Ants, which feed on the honey-dew secreted by the Aphides. Not only, moreover, do the Ants protect the Aphides themselves, but collect their eggs in autumn, and tend them carefully through the winter, ready for the next spring. Many other insects are also domesticated by Ants, and some of them, from living constantly underground,have completely lost their eyes and become quite blind.

But I must not let myself be carried away by this fascinating subject, which I have treated more at length in another work.[14]I will only say that though their intelligence is no doubt limited, still I do not think that any one who has studied the life-history of Ants can draw any fundamental line of separation between instinct and reason.

When we see a community of Ants working together in perfect harmony, it is impossible not to ask ourselves how far they are mere exquisite automatons; how far they are conscious beings? When we watch an ant-hill tenanted by thousands of industrious inhabitants, excavating chambers, forming tunnels, making roads, guarding their home, gathering food, feeding the young, tending their domestic animals—each one fulfilling its duties industriously, and without confusion,—it is difficult altogether to deny to them the gift of reason; and all ourrecent observations tend to confirm the opinion that their mental powers differ from those of men, not so much in kind as in degree.

FOOTNOTES:[11]The Horse.[12]Lubbock,Fifty Years of Science.[13]The Open Air.[14]Ants, Bees, and Wasps.

[11]The Horse.

[12]Lubbock,Fifty Years of Science.

[13]The Open Air.

[14]Ants, Bees, and Wasps.

An organic being is a microcosm—a little universe, formed of a host of self-propagating organisms, inconceivably minute and numerous as the stars of heaven.Darwin.

An organic being is a microcosm—a little universe, formed of a host of self-propagating organisms, inconceivably minute and numerous as the stars of heaven.

Darwin.

We constantly speak of animals as free. A fish, says Ruskin, "is much freer than a Man; and as to a fly, it is a black incarnation of freedom." It is pleasant to think of anything as free, but in this case the idea is, I fear, to a great extent erroneous. Young animals may frolic and play, but older ones take life very seriously. About the habits of fish and flies, indeed, as yet we know very little. Any one, however, who will watch animals will soon satisfy himself how diligently they work. Even when they seem to be idling over flowers, or wandering aimlessly about, they are in truth diligently seeking for food, or collecting materials for nests. The industry of Bees is proverbial. When collecting honey or pollenthey often visit over twenty flowers in a minute, keeping constantly to one species, without yielding a moment's dalliance to any more sweet or lovely tempter. Ants fully deserve the commendation of Solomon. Wasps have not the same reputation for industry; but I have watched them from before four in the morning till dark at night working like animated machines without a moment's rest or intermission. Sundays and Bank Holidays are all the same to them. Again, Birds have their own gardens and farms from which they do not wander, and within which they will tolerate no interference. Their ideas of the rights of property are far stricter than those of some statesmen. As to freedom, they have their daily duties as much as a mechanic in a mill or a clerk in an office. They suffer under alarms, moreover, from which we are happily free. Mr. Galton believes that the life of wild animals is very anxious. "From my own recollection," he says, "I believe that every antelope in South Africa has to run for its life every one or two days upon an average, and that he starts orgallops under the influence of a false alarm many times in a day. Those who have crouched at night by the side of pools in the desert, in order to have a shot at the beasts that frequent it, see strange scenes of animal life; how the creatures gambol at one moment and fight at another; how a herd suddenly halts in strained attention, and then breaks into a maddened rush as one of them becomes conscious of the stealthy movements or rank scent of a beast of prey. Now this hourly life-and-death excitement is a keen delight to most wild creatures, but must be peculiarly distracting to the comfort-loving temperament of others. The latter are alone suited to endure the crass habits and dull routine of domesticated life. Suppose that an animal which has been captured and half-tamed, received ill-usage from his captors, either as punishment or through mere brutality, and that he rushed indignantly into the forest with his ribs aching from blows and stones. If a comfort-loving animal, he will probably be no gainer by the change, more serious alarms and no less ill-usage awaits him: hehears the roar of the wild beasts, and the headlong gallop of the frightened herds, and he finds the buttings and the kicks of other animals harder to endure than the blows from which he fled: he has peculiar disadvantages from being a stranger; the herds of his own species which he seeks for companionship constitute so many cliques, into which he can only find admission by more fighting with their strongest members than he has spirit to undergo. As a set-off against these miseries, the freedom of savage life has no charms for his temperament; so the end of it is, that with a heavy heart he turns back to the habitation he had quitted."

But though animals may not be free, I hope and believe that they are happy. Dr. Hudson, an admirable observer, assures us with confidence that the struggle for existence leaves them much leisure and famous spirits. "In the animal world," he exclaims,[15]"what happiness reigns! What ease, grace, beauty, leisure, and content! Watch these living specks as they glide through theirforests of algæ, all 'without hurry and care,' as if their 'span-long lives' really could endure for the thousand years that the old catch pines for. Here is no greedy jostling at the banquet that nature has spread for them; no dread of each other; but a leisurely inspection of the field, that shows neither the pressure of hunger nor the dread of an enemy.

"'To labour and to be content' (that 'sweet life' of the son of Sirach)—to be equally ready for an enemy or a friend—to trust in themselves alone, to show a brave unconcern for the morrow, all these are the admirable points of a character almost universal among animals, and one that would lighten many a heart were it more common among men. That character is the direct result of the golden law 'If one will not work, neither let him eat'; a law whose stern kindness, unflinchingly applied, has produced whole nations of living creatures, without a pauper in their ranks, flushed with health, alert, resolute, self-reliant, and singularly happy."

It has often been said that Man is the onlyanimal gifted with the power of enjoying a joke, but if animals do not laugh, at any rate they sometimes play. We are, indeed, apt perhaps to credit them with too much of our own attributes and emotions, but we can hardly be mistaken in supposing that they enjoy certain scents and sounds. It is difficult to separate the games of kittens and lambs from those of children. Our countryman Gould long ago described the "amusements or sportive exercises" which he had observed among Ants. Forel was at first incredulous, but finally confirmed these statements; and, speaking of certain tropical Ants, Bates says "the conclusion that they were engaged in play was irresistible."

We share with other animals the great blessing of Sleep, nature's soft nurse, "the mantle that covers thought, the food that appeases hunger, the drink that quenches thirst, the fire that warms cold, the cold thatmoderates heat, the coin that purchases all things, the balance and weight that equals the shepherd with the king, and the simple with the wise." Some animals dream as we do; Dogs, for instance, evidently dream of the chase. With the lower animals which cannot shut their eyes it is, however, more difficult to make sure whether they are awake or asleep. I have often noticed insects at night, even when it was warm and light, behave just as if they were asleep, and take no notice of objects which would certainly have startled them in the day. The same thing has also been observed in the case of fish.

But why should we sleep? What a remarkable thing it is that one-third of our life should be passed in unconsciousness. "Half of our days," says Sir T. Browne, "we pass in the shadow of the earth, and the brother of death extracteth a third part of our lives." The obvious suggestion is that we require rest. But this does not fully meet the case. In sleep the mind is still awake, and lives a life of its own: our thoughts wander, uncontrolled, by the will. The mind, therefore, isnot necessarily itself at rest; and yet we all know how it is refreshed by sleep.

But though animals sleep, many of them are nocturnal in their habits. Humboldt gives a vivid description of night in a Brazilian forest.

"Everything passed tranquilly till eleven at night, and then a noise so terrible arose in the neighbouring forest that it was almost impossible to close our eyes. Amid the cries of so many wild beasts howling at once the Indians discriminated such only as were (at intervals) heard separately. These were the little soft cries of the sapajous, the moans of the alouate apes, the howlings of the jaguar and couguar, the peccary and the sloth, and the cries of (many) birds. When the jaguars approached the skirt of the forest our dog, which till then had never ceased barking, began to howl and seek for shelter beneath our hammocks. Sometimes, after a long silence, the cry of the tiger came from the tops of the trees; and then it was followed by the sharp and long whistling of the monkeys, which appeared to flee from the danger whichthreatened them. We heard the same noises repeated during the course of whole months whenever the forest approached the bed of the river.

"When the natives are interrogated on the causes of the tremendous noise made by the beasts of the forest at certain hours of the night, the answer is, they are keeping the feast of the full moon. I believe this agitation is most frequently the effect of some conflict that has arisen in the depths of the forest. The jaguars, for instance, pursue the peccaries and the tapirs, which, having no defence, flee in close troops, and break down the bushes they find in their way. Terrified at this struggle, the timid and distrustful monkeys answer, from the tops of the trees, the cries of the large animals. They awaken the birds that live in society, and by degrees the whole assembly is in commotion. It is not always in a fine moonlight, but more particularly at the time of a storm of violent showers, that this tumult takes place among the wild beasts. 'May heaven grant them a quiet night and repose, and us also!' said themonk who accompanied us to the Rio Negro, when, sinking with fatigue, he assisted in arranging our accommodation for the night."

Life is indeed among animals a struggle for existence, and in addition to the more usual weapons—teeth and claws—we find in some animals special and peculiar means of offence and defence.

If we had not been so familiarised with the fact, the possession of poison might well seem a wonderful gift. That a fluid, harmless in one animal itself, should yet prove so deadly when transferred to others, is certainly very remarkable; and though the venom of the Cobra or the Rattlesnake appeal perhaps more effectively to our imagination, we have conclusive evidence of concentrated poison even in the bite of a midge, which may remain for days perceptible. The sting of a Bee or Wasp, though somewhat similar in its effect, is a totally different organ, being a modified ovipositor. Some species of Ants do not sting in the ordinary sense, but eject their acrid poison to a distance of several inches.

Another very remarkable weapon is theelectric battery of certain Eels, of the Electric Cat Fish, and the Torpedoes, one of which is said to be able to discharge an amount of electricity sufficient to kill a Man.

Some of the Medusæ and other Zoophytes are armed by millions of minute organs known as "thread cells." Each consists of a cell, within which a firm, elastic thread is tightly coiled. The moment the Medusa touches its prey the cells burst and the threads spring out. Entering the flesh as they do by myriads, they prove very effective weapons.

The ink of the Sepia has passed into a proverb. The animal possesses a store of dark fluid, which, if attacked, it at once ejects, and thus escapes under cover of the cloud thus created.

The so-called Bombardier Beetles, when attacked, discharge at the enemy, from the hinder part of their body, an acrid fluid which, as soon as it comes in contact with air, explodes with a sound resembling a miniature gun. Westwood mentions, on the authority of Burchell, that on one occasion, "whilst resting for the night on the banks of one ofthe large South American rivers, he went out with a lantern to make an astronomical observation, accompanied by one of his black servant boys; and as they were proceeding, their attention was directed to numerous beetles running about upon the shore, which, when captured, proved to be specimens of a large species of Brachinus. On being seized they immediately began to play off their artillery, burning and staining the flesh to such a degree that only a few specimens could be captured with the naked hand, and leaving a mark which remained a considerable time. Upon observing the whitish vapour with which the explosions were accompanied, the negro exclaimed in his broken English, with evident surprise, 'Ah, massa, they make smoke!'"

Many other remarkable illustrations might be quoted; as for instance the web of the Spider, the pit of the Ant Lion, the mephitic odour of the Skunk.

We generally attribute to animals five senses more or less resembling our own. Buteven as regards our own senses we really know or understand very little. Take the question of colour. The rainbow is commonly said to consist of seven colours—red, orange, yellow, green, blue, indigo, and violet.

But it is now known that all our colour sensations are mixtures of three simple colours, red, green, and violet. We are, however, absolutely ignorant how we perceive these colours. Thomas Young suggested that we have three different systems of nerve fibres, and Helmholtz regards this as "a not improbable supposition"; but so far as microscopical examination is concerned, there is no evidence whatever for it.

Or take again the sense of Hearing. The vibrations of the air no doubt play upon the drum of the ear, and the waves thus produced are conducted through a complex chain of small bones to the fenestra ovalis and so to the inner ear or labyrinth. But beyond this all is uncertainty. The labyrinth consists mainly of two parts (1) the cochlea, and (2) the semicircular canals, which are three in number, standing at right angles to oneanother. It has been supposed that they enable us to maintain the equilibrium of the body, but no satisfactory explanation of their function has yet been given. In the cochlea, Corti discovered a remarkable organ consisting of some four thousand complex arches, which increase regularly in length and diminish in height. They are connected at one end with the fibres of the auditory nerve, and Helmholtz has suggested that the waves of sound play on them, like the fingers of a performer on the keys of a piano, each separate arch corresponding to a different sound. We thus obtain a glimpse, though but a glimpse, of the manner in which perhaps we hear; but when we pass on to the senses of smell and taste, all we know is that the extreme nerve fibres terminate in certain cells which differ in form from those of the general surface; but in what manner the innumerable differences of taste or smell are communicated to the brain, we are absolutely ignorant.

If then we know so little about ourselves, no wonder that with reference to other animals our ignorance is extreme.

We are too apt to suppose that the senses of animals must closely resemble, and be confined to ours.

No one can doubt that the sensations of other animals differ in many ways from ours. Their organs are sometimes constructed on different principles, and situated in very unexpected places. There are animals which have eyes on their backs, ears in their legs, and sing through their sides.

We all know that the senses of animals are in many cases much more acute than ours, as for instance the power of scent in the dog, of sight in the eagle. Moreover, our eye is much more sensitive to some colours than to others; least so to crimson, then successively to red, orange, yellow, blue, and green; the sensitiveness for green being as much as 750 times as great as for red. This alone may make objects appear of very different colours to different animals.

Nor is the difference one of degree merely. The rainbow, as we see it, consists of seven colours—red, orange, yellow, green, blue, indigo, and violet. But though the red andviolet are the limits of the visible spectrum, they are not the limits of the spectrum itself, there are rays, though invisible to us, beyond the red at the one end, and beyond the violet at the other: the existence of the ultra red can be demonstrated by the thermometer; while the ultra violet are capable of taking a photograph. But though the red and violet are respectively the limits of our vision, I have shown[16]by experiments which have been repeated and confirmed by other naturalists, that some of the lower animals are capable of perceiving the ultra-violet rays, which to us are invisible. It is an interesting question whether these rays may not produce on them the impression of a new colour, or colours, differing from any of those known to us.

So again with hearing, not only may animals in some cases hear better than we do, but sounds which are beyond the reach of our ears, may be audible to theirs. Even among ourselves the power of hearing shrill sounds is greater in some persons than in others. Sound, as we know, is produced byvibration of the air striking on the drum of the ear, and the fewer are the vibrations in a second, the deeper is the sound, which becomes shriller and shriller as the waves of sound become more rapid. In human ears the limits of hearing are reached when about 35,000 vibrations strike the drum of the ear in a second.

Whatever the explanation of the gift of hearing in ourselves may be, different plans seem to be adopted in the case of other animals. In many Crustacea and Insects there are flattened hairs each connected with a nerve fibre, and so constituted as to vibrate in response to particular notes. In others the ear cavity contains certain minute solid bodies, known as otoliths, which in the same way play upon the nerve fibres. Sometimes these are secreted by the walls of the cavity itself, but certain Crustacea have acquired the remarkable habit of selecting after each moult suitable particles of sand, which they pick up with their pincers and insert into their ears.

Many insects, besides the two large"compound" eyes one on each side of the head, have between them three small ones, known as the "ocelli," arranged in a triangle. The structure of these two sets of eyes is quite different. The ocelli appear to see as our eyes do. The lens throws an inverted image on the back of the eye, so that with these eyes they must see everything reversed, as we ourselves really do, though long practice enables us to correct the impression. On the other hand, the compound eyes consist of a number of facets, in some species as many as 20,000 in each eye, and the prevailing impression among entomologists now is that each facet receives the impression of one pencil of rays, that in fact the image formed in a compound eye is a sort of mosaic. In that case, vision by means of these eyes must be direct; and it is indeed difficult to understand how an insect can obtain a correct impression when it looks at the world with five eyes, three of which see everything reversed, while the other two see things the right way up!

On the other hand, some regard eachfacet as an independent eye, in which case many insects realise the epigram of Plato—

Thou lookest on the stars, my love,Ah, would that I could beYon starry skies with thousand eyes,That I might look on thee!

Even so, therefore, we only substitute one difficulty for another.

But this is not all. We have not only no proof that animals are confined to our five senses, but there are strong reasons for believing that this is not the case.

In the first place, many animals have organs which from their position, structure, and rich supply of nerves, are evidently organs of sense; and yet which do not appear to be adapted to any one of our five senses.

As already mentioned, the limits of hearing are reached when about 35,000 vibrations of the air strike on the drums of our ears. Light, as was first conclusively demonstrated by our great countryman Young, is the impression produced by vibration of the etheron the retina of the eye. When 700 millions of millions of vibrations strike the eye in a second, we see violet; and the colour changes as the number diminishes, 400 millions of millions giving us the impression of red.

Between 35 thousand and 400 millions of millions the interval is immense, and it is obvious that there might be any number of sensations. When we consider how greatly animals differ from us, alike in habits and structure, is it not possible, nay, more, is it not likely that some of these problematical organs are the seats of senses unknown to us, and give rise to sensations of which we have no conception?

In addition to the capacity for receiving and perceiving, some animals have the faculty of emitting light. In our country the glow-worm is the most familiar case, though some other insects and worms have, at any rate under certain conditions, the same power, and it is possible that many others are really luminous, though with light which is invisible to us. In warmer climates the Fire-fly, Lanthorn-fly, and many other insects, shine withmuch greater brilliance, and in these cases the glow seems to be a real love-light, like the lamp of Hero.

Many small marine animals, Medusæ, Crustacea, Worms, etc., are also brilliantly luminous at night. Deep-sea animals are endowed also in many cases with special luminous organs, to which I shall refer again.

It has been supposed that animals possess also what has been called a Sense of Direction. Many interesting cases are on record of animals finding their way home after being taken a considerable distance. To account for this fact it has been suggested that animals possess a sense with which we are not endowed, or of which, at any rate, we possess only a trace. The homing instinct of the pigeon has also been ascribed to the same faculty. My brother Alfred, however, who has paid much attention to pigeons, informs me that they are never taken any great distanceat once; but if they are intended to take a long flight, they are trained to do so by stages.

Darwin suggested that it would be interesting to test the case by taking animals in a close box, and then whirling them round rapidly before letting them out. This is in fact done with cats in some parts of France, when the family migrates, and is considered the only way of preventing the cat from returning to the old home. Fabre has tried the same thing with some wild Bees (Chalicodoma). He took some, marked them on the back with a spot of white, and put them into a bag. He then carried them a quarter of a mile, stopping at a point where an old cross stands by the wayside, and whirled the bag rapidly round his head. While he was doing so a good woman came by, who seemed not a little surprised to find the Professor solemnly whirling a black bag round his head in front of the cross; and, he fears, suspected him of Satanic practices. He then carried his Bees a mile and a half in the opposite direction and let them go. Three out often found their way home. He tried the same experiment several times, in one case taking them a little over two miles. On an average about a third of the Bees found their way home. "La démonstration," says Fabre, "est suffisante. Ni les mouvements enchevêtrés d'une rotation comme je l'ai décrite; ni l'obstacle de collines à franchir et de bois à traverser; ni les embûches d'une voie qui s'avance, rétrograde, et revient par un ample circuit, ne peuvent troubler les Chalicodomes dépaysés et les empêcher de revenir au nid."

I must say, however, that I am not convinced. In the first place, the distances were I think too short; and in the second, though it is true that some of the Bees found their way home, nearly two-thirds failed to do so. It would be interesting to try the experiment again, taking the Bees say five miles. If they really possess any such sense, that distance would be no bar to their return. I have myself experimented with Ants, taking them about fifty yards from the nest, and I always found that they wandered aimlesslyabout, having evidently not the slightest idea of their way home. They certainly did not appear to possess any "sense of direction."

The total number of species may probably be safely estimated as at least 2,000,000, of which but a fraction have yet been described or named. Of extinct species the number was probably at least as great. In the geological history of the earth there have been at least twelve periods, in each of which by far the greatest number were distinct. The Ancient Poets described certain gifted mortals as having been privileged to descend into the interior of the earth, and exercised their imagination in recounting the wonders thus revealed. As in other cases, however, the realities of Science have proved far more varied and surprising than the dreams of fiction. Of these extinct species our knowledge is even more incomplete than that of the existing species. But even of our contemporariesit is not too much to say that, as in the case of plants, there is not one the structure, habits, and life-history of which are yet fully known to us. The male of the Cynips, which produces the common King Charles Oak Apple, has only recently been discovered, those of the root-feeding Aphides, which live in hundreds in every nest of the yellow Meadow Ant (Lasius flavus) are still unknown; the habits and mode of reproduction of the common Eel have only just been discovered; and we may even say generally that many of the most interesting recent discoveries have relation to the commonest and most familiar animals.

Whatever pre-eminence Man may claim for himself, other animals have done far more to affect the face of nature. The principal agents have not been the larger or more intelligent, but rather the smaller, and individually less important, species. Beavers may have dammed up many of the rivers of BritishColumbia, and turned them into a succession of pools or marshes, but this is a slight matter compared with the action of earthworms and insects[17]in the creation of vegetable soil; of the accumulation of animalcules in filling up harbours and lakes; or of Zoophytes in the construction of coral islands.

Microscopic animals make up in number what they lack in size. Paris is built of Infusoria. The Peninsula of Florida, 78,000 square miles in extent, is entirely composed of coral debris and fragments of shells. Chalk consists mainly of Foraminifera and fragments of shells deposited in a deep sea. The number of shells required to make up a cubic inch is almost incredible. Ehrenberg has estimated that of the Bilin polishing slate which caps the mountain, and has a thickness of forty feet, a cubic inch contains many hundred million shells of Infusoria.

In another respect these microscopic organismsare of vital importance. Many diseases are now known, and others suspected, to be entirely due to Bacteria and other minute forms of life (Microbes), which multiply incredibly, and either destroy their victims, or after a while diminish again in numbers. We live indeed in a cloud of Bacteria. At the observatory of Montsouris at Paris it has been calculated that there are about 80 in each cubic meter of air. Elsewhere, however, they are much more numerous. Pasteur's researches on the Silkworm disease led him to the discovery of Bacterium anthracis, the cause of splenic fever. Microbes are present in persons suffering from cholera, typhus, whooping-cough, measles, hydrophobia, etc., but as to their history and connection with disease we have yet much to learn. It is fortunate, indeed, that they do not all attack us.

In surgical cases, again, the danger of compound fractures and mortification of wounds has been found to be mainly due to the presence of microscopic organisms; and Lister, by his antiseptic treatment which destroys thesegerms or prevents their access, has greatly diminished the danger of operations, and the sufferings of recovery.

In the size of animals we find every gradation from these atoms which even in the most powerful microscopes appear as mere points, up to the gigantic reptiles of past ages and the Whales of our present ocean. The horned Ray or Skate is 25 feet in length, by 30 in width. The Cuttle-fishes of our seas, though so hideous as to resemble a bad dream, are too small to be formidable; but off the Newfoundland coast is a species with arms sometimes 30 feet long, so as to be 60 feet from tip to tip. The body, however, is small in proportion. The Giraffe attains a height of over 20 feet; the Elephant, though not so tall, is more bulky; the Crocodile reaches a length of over 20 feet, the Python of 60 feet, the extinct Titanosaurus of the American Jurassic beds, the largest land animal yet known to us, 100 feet in length and 30 in height; theWhalebone Whale over 70 feet, Sibbald's Whale is said to have reached 80-90, which is perhaps the limit. Captain Scoresby indeed mentions a Rorqual no less than 120 feet in length, but this is probably too great an estimate.

The complexity of animal structure is even more marvellous than their mere magnitude. A Caterpillar contains more than 2000 muscles. In our own body are some 2,000,000 perspiration glands, communicating with the surface by ducts having a total length of some 10 miles; while that of the arteries, veins, and capillaries must be very great; the blood contains millions of millions of corpuscles, each no doubt a complex structure in itself; the rods in the retina, which are supposed to be the ultimate recipient of light, are estimated at 30,000,000; and Meinert has calculated that the gray matter of the brain is built up of at least 600,000,000 cells. Noverbal description, however, can do justice to the marvellous complexity of animal structure, which the microscope alone, and even that but faintly, can enable us to realise.

How little we yet know of the life-history of Animals is illustrated by the vagueness of our information as to the age to which they live. Professor Lankester[18]tells us that "the paucity and uncertainty of observations on this class of facts is extreme." The Rabbit is said to reach 10 years, the Dog and Sheep 10-12, the Pig 20, the Horse 30, the Camel 100, the Elephant 200, the Greenland Whale 400 (?): among Birds, the Parrot to attain 100 years, the Raven even more. The Atur Parrot mentioned by Humboldt, talked, but could not be understood, because it spoke in the language of an extinct Indian tribe. It is supposed from their rate of growth that amongFish the Carp is said to reach 150 years; and a Pike, 19 feet long, and weighing 350 lbs., is said to have been taken in Suabia in 1497 carrying a ring, on which was inscribed, "I am the fish which was first of all put into the lake by the hands of the Governor of the Universe, Frederick the Second, the 5th Oct. 1230." This would imply an age of over 267 years. Many Reptiles are no doubt very long-lived. A Tortoise is said to have reached 500 years. As regards the lower animals, the greatest age on record is that of Sir J. Dalzell's Sea Anemone, which lived for over 50 years. Insects are generally short-lived; the Queen Bee, however, is said by Aristotle, whose statement has not been confirmed by recent writers, to live 7 years. I myself had a Queen Ant which attained the age of 15 years.

The May Fly (Ephemera) is celebrated as living only for a day, and has given its name to all things short-lived. The statement usually made is, indeed, very misleading, for in its larval condition the Ephemera lives for weeks. Many writers have expressed surprisethat in the perfect state its life should be so short. It is, however, so defenceless, and, moreover, so much appreciated by birds and fish, that unless they laid their eggs very rapidly none would perhaps survive to continue the species.

Many of these estimates are, as will be seen, very vague and doubtful, so that we must still admit with Bacon that, "touching the length and shortness of life in living creatures, the information which may be had is but slender, observation is negligent, and tradition fabulous. In tame creatures their degenerate life corrupteth them, in wild creatures their exposing to all weathers often intercepteth them."

When we descend still lower in the animal scale, the consideration of this question opens out a very curious and interesting subject connected with animal individuality. As regards the animals with which we are mostfamiliar no such question intrudes. Among quadrupeds and birds, fishes and reptiles, there is no difficulty in deciding whether a given organism is an individual, or a part of an individual. Nor does the difficulty arise in the case of most insects. The Bee or Butterfly lays an egg which develops successively into a larva and pupa, finally producing Bee or Butterfly. In these cases, therefore, the egg, larva, pupa, and perfect Insect, are regarded as stages in the life of a single individual. In certain gnats, however, the larva itself produces young larvæ, each of which develops into a gnat, so that the egg produces not one gnat but many gnats.

The difficulty of determining what constitutes an individual becomes still greater among the Zoophytes. These beautiful creatures in many cases so closely resemble plants, that until our countryman Ellis proved them to be animals, Crabbe was justified in saying—

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