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