It may at first strike our young readers that this is a question very easily answered; if they think so, let them try what sort of an answer they can give to it, and if they break down in the definition, we will endeavour to help them, as we are told in the old fable, Jupiter did the waggoner; but it is best for young people to try, and, for that matter, old people too; let them never believe that they can't do a thing—"where there's a will there's a way." Many a boy that will take a deal of pains, and incur no inconsiderable risk of life and limb, to climb up a tree after a bird's nest, finds it too much trouble to read and learn about the habits of the creature he is thus ready to deprive of its warm comfortable home and beautiful eggs. He cannot tell you, if you ask him, of what the nest is composed, nor how, nor when it was built, much less can he answer the question which we have just put to our readers,—

WHAT IS AN EGG?

"Well," we hear some one say, "an Egg is a thing of an oval shape, large or small, white or coloured and speckled, as the case may be; it has a shell which breaks if you knock it, because it is brittle; and inside is a yellow substance called the yolk, surrounded by a white, clear liquid; if you boil it for a little time it becomes set, so that you can take it up in a spoon, and in this state it is good to eat. Oh! very good, I like an egg, especially for breakfast, with a little salt; and then eggs, and other things with them, make custards, and pancakes, and puddings, and all sorts of nice things; and then I recollect some such funny 'Stanzas to an Egg by a Spoon,' which begin,

Well, never mind the rest. Now listen to our definition of an Egg. The word itself, we may observe first of all, is of Saxon origin; that this is how the ancient dwellers on our island used to write it Æ?, you may call it aeg or oeg, which you like. Johnson says the term means, "That which is laid by feathered and some other animals, from which their young is produced;" it is also, we are told by the same authority, "the spawn or sperm of other creatures," as fish, which are said, you know, not to lay eggs, but to spawn. Another dictionary-maker defines it to be "the ovum of birds," giving us here the Latin for egg, hence that peculiar shape is called oval, and the science of eggs is sometimes termed

OVOLOGY.

As we have told you in the first volume of this series, Oology is another term for this science, which has occupied the attention of many learned men, who have gone deeper into Eggs than ever you or I shall, and told us such strange things about them, as would scarcely be believed by the very hens that laid them. Little does the happy mother think, when she goes cackling about the yard, proclaiming the event, that she has produced such a wonderful object. It looks a simple affair enough, one might make a thing very like it with a piece of chalk; touch it, roll it about; boil it, eat it, or crack it, and let the inside flow out; there's the yellow, and there's the white; there's nothing very particular in that, all eggs are so. Well, who made them so? and of what are they made? and what reason is there for this peculiar arrangement of the different parts of an Egg? and how is it that, under certain circumstances, so complete a change should take place in the nature of its contents—that the fluids should be gradually absorbed into a solid body, and that, by and by, at the end of a period which can be calculated to a nicety, the shell should be burst open, and there should come forth a living creature? Truly this is wonderful; but we are surrounded by wonders, and only heed them not because they are so common.

But about this common thing, an Egg? It is the germ or seed, so to speak, of animal life; in it is contained all that is necessary for the formation of the perfect living creature; in that little oval case lie snugly packed up, bones, and muscles, and sinews, and all the delicate parts, organs, as they would be called, from a Greek word signifying an instrument, thus the tongue is an organ of speech, the eye of sight, and so on. But all these organs are in an undeveloped state, as the flower is in the bud; develope is a French word, and signifies to unroll, or unfold. The animal is there in embryo; this again is Greek, and means a thing unperfected, or unfinished, so the poet Thompson says:—

And so with closer reference to our subject, we might say,

Dr. Harvey, who made that great discovery, the circulation of the blood, uttered a truth when he said omne animal ex ovo, every animal is born of an egg, for although some animals are oviparous, and others viviparous,—the two words come from ovum egg, vivum life, and pario to bring forth—yet may the first stage of all animal life be compared to an Egg. From the smallest insect up to the most huge and unwieldy creature that swims in the deep sea, or walks upon the land. All were at one time alike, mere specks, surrounded by fluid matter, which afforded the material for growth and nourishment, and enclosed in some kind of a case, which if not exactly like an egg shell, answers the same purpose of protection from injury.

What a vast difference is there between the bright-winged insect, whose history we traced in our volume on Butterflies, and the bird with downy plumage and the voice of melody; between that again and the great crocodile, in his scaly coat of mail; the mighty boa constrictor, king of serpents; or that tyrant of the deep, the fierce voracious shark; and yet all these come from Eggs, very similar in form, and precisely so in their nature and internal construction. Look too at the difference in size, between the egg of the Humming Bird, no bigger than a pea, and that of the Ostrich, as large as a man's head nearly, or bigger still that of the Epyornis, of which fossil remains have been found in Madagascar, the contents of which must have been equal to six ostrichs', or one hundred and forty-eight common hens' eggs, that is about seventeen English pints; and yet in all these the germ, or as it would be called, the vital principle, that is, the principle of life, is but a tiny speck, or circle, which is attached to the membrane that surrounds the yellow portion, or yolk; it is from this that the animal in embryo derives nourishment, and the size of it, and consequently of the whole egg, is in proportion to the quantity that is required to sustain life, until the protection of the shell is no longer necessary. There is only so much food stored up as the bird, or reptile, or whatever it may be, requires before it is strong enough to make an opening in its prison, and come forth to provide for itself, or be fed by the parent. Some creatures that eventually attain a large size are born, or hatched, as it is termed, comparatively small; thus the size of the egg is not always in proportion to that of the animal which lays it; the crocodile's egg, for instance, is but little larger than that of the common fowl; the young comes forth like a small lizard, about two or three inches long, takes to the water at once, and begins to catch insects on its own account; its mother may be twenty or thirty feet in length. Most creatures that produce eggs small in proportion to their size lay a great many; this is especially the case with fish, whose spawn must be numbered by millions: it has been calculated that if the young of a single pair of herrings were suffered to breed undisturbed, they would in twenty years together make up a bulk six times the size of the earth; but so many creatures feed upon this spawn, that few of the eggs of which it is composed ever come to young fish, that is comparatively few, for the vast shoals which every year visit our shores, for the purpose of depositing their spawn in shallow water, shew that immense numbers must escape the dangers to which they are exposed. There are some fish of the fierce and rapacious kind, such as the Ray, the Dog-fish, and the Shark, which attain a considerable size before they lose the protection of the egg-shell, which is of a very peculiar shape and construction, being of a leathery texture, flat, and four-cornered, with a long curling string-like projection from each corner; frequenters of the coast, to whom they are very familiar objects, being often cast up on the beach, call them Mermaid's purses, and Fairy-purses, while the clustered Eggs of the Cuttle-fish they term Sea Grapes.

All eggs require warmth to hatch them; the fishes know this, not as we know it, because we have read, or been told so, and can reason upon causes and consequences, and so understand why, but they know it instinctively; they possess, in common with all unreasoning creatures, what we call instinct, that is, a natural impulse to do in the right way, and at the proper time, whatever may be necessary for the maintenance of that state of existence in which God has placed them; so instinct directs the fishes when the time for spawning has arrived, to leave the deep waters, where they generally remain safe from the pursuit of man, for the shores, where the warmth of the sun can reach the eggs, and awaken the principle of life within them. So instinct teaches the bird to leave its winter home, in some far southern country, and fly hundreds of miles across land and ocean, to reach a spot suitable for the purpose of breeding and rearing its young; to collect the materials and to build its nest, and after the eggs are laid, to sit patiently on them the appointed time; to select the food proper for those little gaping bills, and to tend the fledglings carefully, until they are able to fly and provide for themselves, and then, when their wings are strong enough for the journey, and their food begins to get scarce, away they go back to the south of Europe, or Africa, straight as an arrow, and the young ones, which have never flown that way before, seem to know it as well as those which have been backwards and forwards, often and often.

But the egg, what of that? Can we describe its nature and construction in a way sufficiently clear for our readers to understand? Let us try:—it is like a series of cases or envelopes, one within the other; the outer one only, which is the last formed, being hard and unelastic, that is, it will not stretch or change its shape. Like the shells of some fish, and other testaceous animals, it is composed of carbonate of lime, which the animal has the power of secreting, as it is called, from its food. Hens sometimes lay soft eggs, without a shell; this shews a deficiency of the secreting power, or a want of the necessary material, and may generally be remedied by mixing some chalk with the food, or scattering it about the yard. Next to the shell is a skin called the membrana putaminis, that means the membrane or skin of the shell; it has also a Greek name—chorian; it is divided into two layers, which separate at the larger end, and leave a space called the vesicula aËris, that is, air vesicle, or little bladder; this contains the air necessary for the chick to breathe before it chips the shell. Enclosed in this membrane is the albumen, or white fluid, sometimes called the glair, from the Latin glarea; in the same language albus means white; and our readers who live in Albion, so called from her chalky cliffs, ought to see at once from whence we derive the word albumen; the little chords by which this bag of fluid is suspended are called chalaza; this word comes from a Greek root, and has reference to the connection between the suspending chords and the germ, or spot, in which is the vital principle.

We now come to what may be called the provision bag, because it encloses the yolk, which serves as food for the animal in embryo; it is called membrana vitelli, or the skin of life. Thus our examination of the egg has brought to view the three great necessities of all existence—protection, the shell and albumen; nutrition or food, the yolk; and the vital principle, to understand the nature of which has puzzled the greatest philosophers that the world ever saw. It is said in the Scriptures that God breathed into man the breath of life, but what this may be we can none of us tell; it is given to us and we live, it is taken away from us and we die; and so do all God's creatures, which by Him, and Him alone, live, and move, and have their being. Man can do many wonderful things, but he has not yet been, nor will he ever be, able to make an egg, much less to produce a chick from it.

Let us now fancy that we are looking upon one of these strange little elongated globes, and that instead of being opaque, that is, dark—not clear, it is transparent, so that we can see into it, and observe the changes which are taking place there. The mother bird has been sitting on it for, say twelve hours, and the warmth of her body has called into action the principle of growth, or of vitality; the little spot and ring in the centre of the yolk have become somewhat enlarged and changed in form; they are no longer round, but the outline is irregular, shewing a tendency to shoot or spread out on all sides. Four hours later shews them yet more enlarged, and getting into an oval shape, with a distinct, though somewhat broken line down the centre. When the incubation has lasted thirty-six hours, (for meaning of this word, see the first series of "Nests and Eggs,") there is a still greater increase in the germ, and a spreading of its mottled margin over a portion of the yolk; if at this stage of growth we examine it through a magnifying glass, we shall see a little body like some curious kind of caterpillar, and veins shaped like stags' horns branching out of it in every direction. On the fourth day the chick is a more strange-looking object still, with great projecting eyes with rings round them, like spectacles, and what appears to be a very blunt sort of a snout or muzzle; the whole head, and there is not much else, reminds one of that of a serpent, it might be the Cobra di Capello, or the Spectacle Snake, seen through a diminishing glass. But we cannot give a proper description of it, so we have called in the aid of our artist, who has furnished us, on the next page, with portraits of the interesting creature at four different stages of its growth. In the last we get a side view, and begin to fancy we discover some resemblance to a baby-fowl, although a very hideous one.

All this time a great change has been going on in the whole interior of the egg; the chick has, of course greatly increased, and the red veins have become more numerous, and spread over the entire surface; the yolk is scarcely distinguishable from the other portions. Now, too, the bones of the chick have begun to form, and we clearly perceive the projection of the wings and the stump of the tail, while the pupil of the eye is quite clear and distinct. Larger and larger the creature grows, until it fills all the space, and has to be doubled up in a very curious manner, with the feet and the head brought together, and the bill close to the shell, ready to be used as the instrument of liberation. Many persons suppose that the parent bird chips the shell, but this is not so, it is done by the little creature within, which has first to make its way through a thick membrane, or skin; this it does on the twenty-first day of incubation; we are speaking now of the common fowl, the periods in different species of birds vary considerably, although the process of growth in all is the same. One wonders how, with its soft bill, the little creature can make its way through the tough skin, and hard, though brittle shell; but it must be remembered that the elastic skin is stretched to its greatest extent, and when in this state, a slight prick will make a large opening; and the shell, too, is no doubt, by the pressure from within, rendered less capable of resisting the stroke, slight though it be, of the bill of the prisoner, which does sometimes fail to make its escape, and dies in confinement, if not released by some friendly hand from without.

As if to assist in the work of opening a passage to the light and air, there is found on the tip of the chick's bill a small horny scale, having at the centre a hard and sharp projecting point, which, from the position of the head, is brought into direct and constant contact with the inner surface of the shell; this scale soon loosens and comes away after the chick is hatched, there is then no further use for it. The preceding figure represents the chick as it lies closely folded up on the twenty-first day, just previous to its deliverance from bondage.

We have now finished our account of this wonderful process, and may say in the words of a recent writer, "Dull indeed of soul must the man be, (or boy either,) in whom an egg does not inspire emotions of awe and admiration, wonder and worship. The circle of life is from the adult (fully-grown animal,) to the egg. This is the vital round—the beginning and the ending—the ending and the beginning. The wheel goes round continually, life kindling sparks of life; and what is called death is the worn-out forms becoming cold and decaying away."

HOW TO PRESERVE EGGS FOR THE CABINET.

For this purpose eggs which are newly laid should always be chosen, as any decomposition of the contents will, probably, cause a discolouration of the shell. Make a hole at the smaller end, with an awl, or some other pointed instrument, and another at the larger end, which should be as small as possible, merely a pin hole will do; to this latter the mouth must be applied to blow out the contents. If the yolk does not come out readily, get a cup full of water, and immersing the sharp end into it, put your mouth to the blunt end, and suck up some of the water into the shell, then shake it about well, and blow it out again; repeat this operation two or three times, if necessary. If the shell has got soiled in any way, wash it well in strong lather, using a nail-brush if the stains do not come off readily, but great care must be taken in the handling of so brittle and fragile an article. Now as the membrane which lines the shell would be likely to decompose, and render it offensive, if not injure its beauty, it is best to wash the inside with a solution of the bichloride of mercury, commonly called corrosive sublimate, in spirits of wine; this solution should be prepared by a chemist, and used with great caution, as it is extremely poisonous. Pour it into a wineglass, and holding the egg firmly, yet tenderly, with the finger and thumb, which should not touch the liquid, put the smaller end therein; then apply the mouth, as previously directed, to the larger end, and suck up gently; cease doing so as soon as you are aware, by a cold sensation in the finger and thumb, that the liquid has entered the shell, which then take up by the two ends, so as to stop the orifice, and shake it well, then blow the solution back into the glass, taking care to wash the lips or the fingers if it comes in contact with either of them. The Oological specimen will soon dry, and is now ready for the cabinet. To render it more glossy and brilliant, it may have a coat of mastic varnish, put on thinly with a camel-hair brush, or, if the egg be of a blue or green tint, as many are, a solution of very pure white gum arabic is best, as the varnish is apt to injure those delicate colours.

As to the formation of the cabinet, and arrangement of the eggs therein, directions are scarcely necessary; this must depend very much upon the means and conveniences, as well as the taste of the collector. Shallow drawers with divisions sufficiently broad for the names of the specimens to be written or pasted along the tops, are perhaps best. Small pill-boxes, which may have the names on the lids, are not bad receptacles, and the cost of a few dozens of these is not much; but above all things let the arrangements be carried out with neatness and order; do not let the specimens be huddled together, but classified, and placed so that the hand may be laid upon any one which may be required. Duplicates for exchanging with other collectors, or replacing any which may be broken, may be put carefully in a drawer by themselves, their presence with the others will only cause unnecessary confusion and trouble.

Care should be taken not to name a specimen positively, if there is any doubt of its identity, it may be named with a query; and in the note-book, which every collector should keep, should be entered all the circumstances which weigh for or against the correctness of the designation given to it. This note-book ought to be a complete record of the time and place of acquisition of every specimen included in the collection, and of all that is curious or interesting connected with it. If nests as well as eggs are preserved, of course drawers with divisions are the very best receptacles; they occupy a great deal of space, and, except in some cases where the structure is peculiarly neat or curious, it is perhaps scarcely worth while to take and preserve them, especially as doing so often involves a cruel spoliation of the feathered architects, whose carefully chosen situations for building are well described by Dr. Bidlake, in his "Walks in a Forest."