I had not lighted the gas. The street-lamps sent up their rays, making the room semi-lucent. I took out my tower-key. What matter, if I held the cold iron thereof to my lips awhile? there was no frost in the March air then. I sent my restless fingers in and out of the wards, prisoning them often therein. As thus I stood, with cheek pressed against the windowpane, looking out upon the city, set into a rim of darkness, from out of which it flashed its million rays, papa came up.
"I didn't say good-night," he said, coming in, and to the window where I was. "But how is this, Anna? what has happened to my child? "—and he pointed to shining drops that glistened on the window-glass.
They must have come from my eyes; I could not deny their authorship, and so I confessed to tears of gladness at seeing him once more.
He looked fondly down at me through the dim light. I asked him after the tenant of my premises. He shook his head as one does in great doubt, said "life was uncertain," and repeated several other axioms, that were quite apart from his original style, and excessively annoying to me.
"Papa," I said, "why not tell me truly? will this man recover?"
"'Man proposes, God disposes,' my child," he said.
"I don't dispute the general truth," I replied,—"but, particularly, is this man's life in danger?"
He began to quote somebody's psalm or hymn about "fitful fevers and fleeting shadows."
My father has a fine, rich, variant power of sound with which to charm such as have ears to hear, and Anna Percival has been so endowed. Therefore she listened and waited to the end. When it came, she looked up into her father's face and said,—
"Papa, I am not a child, to be coaxed into forgetfulness; why will you not trust me? I am older than Sophie was when you took her in where I have not been; why will you not make me your friend?"—and some sudden collision of watery powers among the window-drops, whether from accretion or otherwise, sent a glistening rivulet down to the barrier of the sash.
Papa folded his arms, and looked at me. I could not bear to be thus shut out. I said so.
"Could you bear to be shut in?" he thought, and asked it.
"I think I could. I could bear anything that you gave me; I could keep anything that you intrusted to my keeping."
Papa looked at me as one does at a cherished vine the outermost edges of which are just frost-touched; then he folded me to his heart. I felt the throbbings thereof, and mine began to regret that I had intruded into the vestibule of his sacred temple; but a certain something went whispering within me, "You can feed the sacred fire," and I whispered to the whispering voice, and to my father's ear,—
"You'll take me in, won't you?"
"Come," was the only spoken word.
The room was not cheery; he felt it, and said,—
"You see what the effect is when my Myrtle-Vine is off my walls;" and he tossed aside books and papers that had evidently been astray for days, and lay now in his way.
Papa took a key (he wears it too, it seems: that is even more than I do with my tower's) from a tiny chain of gold about his neck, and unlocked the door connecting this silent room with his own. He went in, leaving me outside. He lighted a candle and left it burning there. He came, took my hand, and, with the leading whereby we guide a child, conducted me in thither. Then he went out and left me standing, bewildered, there.
I had anticipated something wonderful. What was here? It was a silent room. The carpet had a river-pattern meandering over its dark-blue ground: it must have been years since a broom went over it. Strange medley of furniture was here. I looked upon the walls. Pictures that must have come from another race and generation hung there. There were many of them. One side of the room held one only. It was a portrait. I remembered the original in life. "My mother," I exclaimed. In the room's centre, surrounded by various articles, was the very boat that I knew Mary Percival had guided out to sea to save Abraham Axtell. Two tiny oars lay across it. The paint was faded; the seams were open; it would hold water no longer. A sense of worship filled me. I looked up at the portrait. My mother smiled: or was it my fancy? Fancy undoubtedly; but fancies give comfort sometimes. I looked again at the boat. On its stern, in small, golden letters, was the name, "Blessing of the Bay," the very name given to the first boat built after the Mayflower's keel touched America's shore. "The name was a good omen," I thought. An armchair stood before the portrait. A shawl was spread over it. I lifted up the fringe to see what the shawl covered. Papa had come in.
"Don't do that, Anna," he said.
"Is it any harm, papa?"
"Your mother died sitting in that chair; her hands spread the shawl over it; it was the last work they did, Anna; it has never since been taken off."
I dropped the fringe; my touch seemed sacrilegious.
Near the chair was a small cabinet; it looked like an altar, or would have done so, had my father been a devotee to any religion requiring visible sacrifice. He opened it.
"Come hither, Anna,"—and I went.
Long, luxuriant bands of softly purplish hair lay within, upon the place of sacrifice.
"Sophie's is like this," I said.
"And Sophie wears one like unto this," said my father; and he took up a circlet of shining gold that lay among the tresses. "Sophie's marriage-ring was hallowed unto her. I gave it the morning she went out from me." He uttered these words with slow reverence of voice.
Why did self come up?
"You gave Sophie our mother's marriage-ring," I said, "and I"—
"Shall wear this," said my father. "I laid it here, with hers;" and he gently lifted the sacred hair, and, freeing the ring, put it upon my finger.
"This is not my marriage-day," I said. "Papa, I don't want it. Besides, gentlemen don't wear marriage-rings: how came you to?"
"Perhaps I have not worn this one; but will you wear it to please me?"
"Why will it please you? It is not symbolical, is it?"
"It makes you doubly mine," he said; and he led me back to outside life, with this strange sort of marriage-ring circling with its planet weight around my finger.
Did my father mean to keep me forever? And with the question came an answer that left sweet contentment in its pathway; it accorded with the intent of my heart.
"Father, have you made me your friend?" I asked, in the room that was terribly tossed, as I restored to place chairs that seemed to have been in a deplorably long dance, and to have forgotten their home at its close.
"You wear my ring, you have come into my orbit," he answered.
"That being true, I am as much interested in the flying comet in there as you are,—for if it strikes you, it hurts me;" and I waited his answer.
After a moment of pause, it came.
"My poor patient is very ill; his life will burn out, if the fever is not stayed;" and as the frenzied laugh reached us, Dr. Percival forgot my presence; he passed his hand slowly across his brow, as if to retouch memory, and then taking down a volume, he began to read. I waited long. At last he closed the book suddenly, said to himself, "I'll try it," and in half a moment my father's white hairs were separated from me by the impassable barrier of the sick-room.
I waited; he did not come. The chairs were not the only articles that had lost the commodity of order in my absence. I went to the table upon which were kept the papers, etc., that lingered there a little while, and then were thought no longer of. Idly I turned them over. What a chaos on a small scale! all the elements of literature were represented. I listened for coming footsteps; none came. "I may as well arrange this table," I thought, "as wait for the morrow;" and I made a beginning by sweeping the chaos at once upon the carpet. Then slowly I began picking them up, one by one, and appointing them stations. My task was nearly done, when, in turning over some magazines, I came upon a pile of papers that had been laid between the leaves of one, and ere I was aware of their presence, they slid down and scattered. I remember having felt a little surprise that my father should have left them there, but I hastened to gather them together. The last one of the number, I noticed, was torn; it had a foreign look. "Father has some new correspondent," I thought, as I looked at the number of mail-marks upon it. "He doesn't think much of it, though, or it would have received better treatment;" and I took a second look at it. A something in the feel of the paper seemed familiar. "It is good for nothing," I said aloud, and I tossed it toward the grate, put the pile of papers where I had found them, surveyed my work with satisfaction, and stood thinking whether or not I should wait to see my father again—it was more than an hour since he went up—to say good-night to me. "I will wait a half-hour; if he doesn't come then, I'll go," I said to the housekeeper, who came to see that all was right for the night, and to remind me that Redleaf had not proved very advantageous to my complexion, and to recommend early hours as a restorative.
In accordance with my promise, I drew a chair forward, placed my feet upon the fender, and began to study the dying embers that were slowly falling through the grate-bars. One, larger than usual, burned its way down. It lighted up, for an instant, the bit of paper, that had not fallen into the coals. Strange fancy it was that led me to imagine that I saw a capital A, followed immediately by that unknown quantity represented by x. I made an effort to gain it, scorched my face, and burned my fingers; for I touched the grate, in rescuing that which I had cast into the place of burning.
"This bit of paper, found in New York, had once been integral with that I had found within the church-yard tower in Redleaf," some inner voice assured me. "Yes, it is a part of it," I said, for I distinctly remembered the fragment whose possession I had so rejoiced over. Some one had written a letter to Miss Axtell; the envelope was torn,—one part there, another here. The letter itself I had found in the gloom of the passage-way; for it Miss Axtell had gone out to search, ill, and in the night; what must its contents have been, to have been worthy of such effort?—and for the time I quite forgot to connect this man, ill in my father's house, with the Herbert whose far-out-at-sea voice I had heard winding up at me through the very death-darkness of the tower. Suddenly the consciousness scintillated in my soul, and wonderful it was; but the picture of my dream came in with it, and I said again, "I am ready for the work which is given me to do," and I waited for its coming till I grew very weary, holding this fragment of envelope fast, as a ship clings to its anchor in mild seas. I ventured to knock at the entrance of my own room. All was silent within. I tried the second time. There came no answer. I dared not venture on the conquering third.
* * * * *
AT SYRACUSE
All day my mule with patient tread
Had moved along the plain,
Now o'er the lava's ashen bed,
Now through the sprouting grain,
Across the torrent's rocky lair,
Beneath the aloe-hedge,
Where yellow broom makes sweet the air,
And waves the purple sedge.
Lone were the hills, save where supine
The dozing goatherd lay,
Or, at a rude and broken shrine,
The peasant knelt to pray;
Or where athwart the distant blue
Thin saffron clouds ascend,
As Carbonari, hid from view,
Their smouldering embers tend.
Luxuriant vale or sterile reach,
A mountain temple-crowned
Or inland curve of glistening beach,
The changeful scene surround;
While scarlet poppies burning near,
And citrons' emerald gleam,
Make barren intervals appear
Dim lapses of a dream.
How meekly o'er the meadows gay
The azure flax-blooms spread!
What fragrance on the breeze of May
The almond-blossoms shed!
Wide-branching fig-trees deck the fields
Or round the quarries cling,
And cactus-stalks, with thorny shields,
In wild contortions spring.
Here groves of cork dusk shadows throw,
There vine-leaves lightsome sway,
While chestnut-plumes serenely glow
Above the olives gray;
Tall pines upon the sloping meads
Their sylvan domes uprear,
And rankly the papyrus-reeds
Low cluster in the mere.
And Syracuse with pensive mien,
In solitary pride,
Like an untamed, but throneless queen,
Crouched by the lucent tide;
With honeyed thyme still Hybla teemed,
Its scent each zephyr bore,
And Arethusa's fountain gleamed
Pellucid as of yore.
Methought, upstarting from his bath,
Old Archimedes cried,
"Eureka!" in my silent path,
Whose echoes long replied;
That Pythias, in the sunset-glow,
Rushed by to Damon's arms,
While from the Tyrant's Cave below
Moaned impotent alarms.
And where upon a sculptured stone
The ruined arch beside,
A hoary, bronzed, and wrinkled crone
The twirling distaff plied,—
Love with exalted Reason fraught
In Plato's accents came,
And Truth by Paul sublimely taught
Relumed her virgin flame.
The ancient sepulchres that rose
Along the voiceless street
Time's myriad vistas seemed to close
And bid life's waves retreat,—
As if intrusive footsteps stole
Beyond their mortal sphere,
And felt the awed and eager soul
Immortal comrades near.
The moss-grown ramparts loom in sight
Like warders of the deep,
Where, flushed with evening's amber light,
The havened waters sleep;
Unfurrowed by a Roman keel
Or Carthaginian oar,
The speared and burnished galleys now
Their slumber break no more.
But when the distant convent-bell,
Ere Day's last smiles depart,
With mellow cadence pleading fell
Upon my brooding heart,—
And Memory's phantoms thick and fast
Their fond illusions bred,
From peerless spirits of the past,
And wrecks of ages fled,—
Joy broke the spell; an emblem blest
That lonely harbor cheered:
As if to greet her pilgrim guest,
My country's flag appeared!
Its radiant folds auroral streamed
Amid that haunted air,
And every star prophetic beamed
With Freedom's triumph there!
* * * * *
METHODS OF STUDY IN NATURAL HISTORY
All important changes in the social and political condition of man, whether brought about by violent convulsions or effected gradually, are at once recognized as eras in the history of humanity. But on the broad high-road of civilization along which men are ever marching, they pass by unnoticed the landmarks of intellectual progress, unless they chance to have some direct bearing on what is called the practical side of life. Such an era marked the early part of our own century; and though at the time a thousand events seemed more full-freighted for the world than the discovery of some old bones at the quarry of Montmartre, and though many a man seemed greater in the estimation of the hour than the professor at the Jardin des Plantes who strove to reconstruct these fragments, yet the story that they told lighted up all the past, and showed its true connection with the present. Cuvier, as one sees him in a retrospective glance at the wonderful period in which he lived, and which brought to the surface all its greatest elements,—one among a throng of exceptional men, generals, soldiers, statesmen, as well as men of commanding intellect in literary and scientific pursuits,—seems always standing at the meeting-point between the past and present. His gaze is ever fixed upon the path along which Creation has moved, and, as he travels back, recovering step by step the road that has been lost to man in apparently impenetrable darkness and mystery, the light brightens and broadens before him, and seems to tempt him on into the dim regions where the great mystery of Creation lies hidden.
Before the year 1800, men had never suspected that their home had been tenanted in past times by a set of beings totally different from those that inhabit it now; still farther was it from their thought to imagine that creation after creation had followed each other in successive ages, every one stamped with a character peculiarly its own. It was Cuvier who, aroused to new labors by the hint he received from the bones unearthed at Montmartre, to which all his vast knowledge of living animals gave him no clue, established by means of most laborious investigations the astounding conclusion, that, prior to the existence of the animals and plants now living, this globe had been the theatre of another set of beings, every trace of whom had vanished from the face of the earth. To his alert and active intellect and powerful imagination a word spoken out of the past was pregnant with meaning; and when he had once convinced himself that he had found a single animal that had no counterpart among living beings, it gave him the key to many mysteries.
It may be doubted whether men's eyes are ever opened to truths which, though new to them, are old to God, till the time has come when they can apprehend their meaning and turn them to good account. It certainly seems, that, when such a revelation has once been made, light pours in upon it from every side; and this is especially true of the case in point. The existence of a past creation once suggested, confirmation was found in a thousand facts overlooked before. The solid crust of the earth gave up its dead, and from the snows of Siberia, from the soil of Italy, from caves of Central Europe, from mines, from the rent sides of mountains and from their highest peaks, from the coral beds of ancient oceans, the varied animals that had possessed the earth ages before man was created spoke to us of the past.
No sooner were these facts established, than the relation between the extinct world and the world of to-day became the subject of extensive researches and comparisons; innumerable theories were started to account for the differences, and to determine the periods and manner of the change. It is not my intention to enter now at any length upon the subject of geological succession, though I hope to return to it hereafter in a series of papers upon that and kindred topics; but I allude to it here, before presenting some views upon the maintenance of organic types as they exist in our own period, for the following reason. Since it has been shown that from the beginning of Creation till the present time the physical history of the world has been divided into a succession of distinct periods, each one accompanied by its characteristic animals and plants, so that our own epoch is only the closing one in the long procession of the ages, naturalists have been constantly striving to find the connecting link between them all, and to prove that each such creation has been a normal and natural growth out of the preceding one. With this aim they have tried to adapt the phenomena of reproduction among animals to the problem of creation, and to make the beginning of life in the individual solve that great mystery of the beginning of life in the world. In other words, they have endeavored to show that the fact of successive generations is analogous to that of successive creations, and that the processes by which animals, once created, are maintained unchanged during the period to which they belong will account also for their primitive existence.
I wish, at the outset, to forestall any such misapplication of the facts I am about to state, and to impress upon my readers the difference between these two subjects of inquiry,—since it by no means follows, that, because individuals are endowed with the power of reproducing and perpetuating their kind, they are in any sense self-originating. Still less probable does this appear, when we consider, that, since man has existed upon the earth, no appreciable change has taken place in the animal or vegetable world; and so far as our knowledge goes, this would seem to be equally true of all the periods preceding ours, each one maintaining unbroken to its close the organic character impressed upon it at the beginning.
The question I propose to consider here is simply the mode by which organic types are preserved as they exist at present. Every one has a summary answer to this question in the statement, that all these short-lived individuals reproduce themselves, and thus maintain their kinds. But the modes of reproduction are so varied, the changes some animals undergo during their growth so extraordinary, the phenomena accompanying these changes so startling, that, in the pursuit of the subject, a new and independent science—that of Embryology—has grown up, of the utmost importance in the present state of our knowledge.
The prevalent ideas respecting the reproduction of animals are made up from the daily observation of those immediately about us in the barn-yard and the farm. But the phenomena here are comparatively simple, and easily traced. The moment we extend our observations beyond our cattle and fowls, and enter upon a wider field of investigation, we are met by the most startling facts. Not the least baffling of these are the disproportionate numbers of males and females in certain kinds of animals, their unequal development, as well as the extraordinary difference between the sexes among certain species, so that they seem as distinct from each other as if they belonged to separate groups of the Animal Kingdom. We have close at hand one of the most striking instances of disproportionate numbers in the household of the Bee, with its one fertile female charged with the perpetuation of the whole community, while her innumerable sterile sisterhood, amid a few hundred drones, work for its support in other ways. Another most interesting chapter connected with the maintenance of animals is found in the various ways and different degrees of care with which they provide for their progeny: some having fulfilled their whole duty toward their offspring when they have given them birth; others seeking hiding-places for the eggs they have laid, and watching with a certain care over their development; others feeding their young till they can provide for themselves, and building nests, or burrowing holes in the ground, or constructing earth mounds for their shelter.
But, whatever be the difference in the outward appearance or the habits of animals, one thing is common to them all without exception: at some period of their lives they produce eggs, which, being fertilized, give rise to beings of the same kind as the parent. This mode of generation is universal, and is based upon that harmonious antagonism between the sexes, that contrast between the male and the female element, that at once divides and unites the whole Animal Kingdom. And although this exchange of influence is not kept up by an equality of numeric relations,—since not only are the sexes very unequally divided in some kinds of animals, but the male and female elements are even combined in certain types, so that the individuals are uniformly hermaphrodites,—yet I firmly believe that this numerical distribution, however unequal it may seem to us, is not without its ordained accuracy and balance. He who has assigned its place to every leaf in the thickest forest, according to an arithmetical law which prescribes to each its allotted share of room on the branch where it grows, will not have distributed animal life with less care.
But although reproduction by eggs is common to all animals, it is only one among several modes of multiplication. We have seen that certain animals, besides the ordinary process of generation, also increase their number naturally and constantly by self-division, so that out of one individual many individuals may arise by a natural breaking up of the whole body into distinct surviving parts. This process of normal self-division may take place at all periods of life: it may form an early phase of metamorphosis, as in the Hydroid of our common Aurelia, described in the last article; or it may even take place before the young is formed in the egg. In such a case, the egg itself divides into a number of portions: two, four, eight, or even twelve and sixteen individuals being normally developed from every egg, in consequence of this singular process of segmentation of the yolk,—which takes place, indeed, in all eggs, but in those which produce but one individual is only a stage in the natural growth of the yolk during its transformation into a young embryo. As the facts here alluded to are not very familiar even to professional naturalists, I may be permitted to describe them more in detail.
No one who has often walked across a sand-beach in summer can have failed to remark what the children call "sand saucers." The name is not a bad one, with the exception that the saucer lacks a bottom; but the form of these circular bands of sand is certainly very like a saucer with the bottom knocked out. Hold one of them against the light and you will see that it is composed of countless transparent spheres, each of the size of a small pin's head. These are the eggs of our common Natica or Sea-Snail. Any one who remembers the outline of this shell will easily understand the process by which its eggs are left lying on the beach in the form I have described. They are laid in the shape of a broad, short ribbon, pressed between the mantle and the shell, and, passing out, cover the outside of the shell, over which they are rolled up, with a kind of glutinous envelope,—for the eggs are held together by a soft glutinous substance. Thus surrounded, the shell, by its natural movements along the beach, soon collects the sand upon it, the particles of which in contact with the glutinous substance of the eggs quickly forms a cement that binds the whole together in a kind of paste. When consolidated, it drops off from the shell, having taken the mould of its form, as it were, and retaining the curve which distinguishes the outline of the Natica. Although these saucers look perfectly round, it will be found that the edges are not soldered together, but are simply lapped one over the other. Every one of the thousand little spheres crowded into such a circle of sand contains an egg. If we follow the development of these eggs, we shall presently find that each one divides into two halves, these again dividing to make four portions, then the four breaking up into eight, and so on, till we may have the yolks divided into no less than sixteen distinct parts. Thus far this process of segmentation is similar to that of the egg in other animals; but, as we shall see hereafter, it seems usually to result only in a change in the quality of its substance, for the portions coalesce again to form one mass, from which a new individual is finally sketched out, at first as a simple embryo, and gradually undergoing all the changes peculiar to its kind, till a new-born animal escapes from the egg. But in the case of the Natica this regular segmentation changes its character, and at a certain period, in a more or less advanced stage of the segmentation, according to the species, each portion of the yolk assumes an individuality of its own, and, instead of uniting again with the rest, begins to subdivide for itself. In our Natica heros, for instance, the common large gray Sea-Snail of our coast, this change takes place when the yolk has subdivided into eight parts. At that time each portion begins a life of its own, not reuniting with its seven twin portions; so that in the end, instead of a single embryo growing out of this yolk, we have eight embryos arising from a single yolk, each one of which undergoes a series of developments similar in all respects to that by which a single embryo is formed from each egg in other animals. We have other Naticas in which the normal number is twelve, others again in which no less than sixteen individuals arise from one yolk. But this process of segmentation, though in these animals it leads to such a multiplication of individuals, is exactly the same as that discovered by K.E. von Baer in the egg of the Frog, and described and figured by Professor Bischof in the egg of the Rabbit, the Dog, the Guinea-Pig, and the Deer, while other embryologists have traced the same process in Birds, Reptiles, and Fishes, as well as in a variety of Articulates, Mollusks, and Radiates.
Multiplication by division occurs also normally in adult animals that have completed their growth. This is especially frequent among Worms; and strange to say, there are species in this Class which never lay eggs before they have already multiplied themselves by self-division.
Another mode of increase is that by budding, as in the Corals and many other Radiates. The most common instance of budding we do not, however, generally associate with this mode of multiplication in the Animal Kingdom, because we are so little accustomed to compare and generalize upon phenomena that we do not see to be directly connected with one another. I allude here to the budding of trees, which year after year enlarge by the addition of new individuals arising from buds. I trust that the usual acceptation of the word individual, used in science simply to designate singleness of existence, will not obscure a correct appreciation of the true relation of buds to their parents and to the beings arising from them. These buds have the same organic significance, whether they drop from the parent stock to become distinct individuals in the common acceptation of the term, or remain connected with the parent stock, as in Corals and in trees, thus forming growing communities of combined individuals. Nor will it matter much in connection with the subject under discussion, whether these buds start from the surface of an animal or sprout in its interior, to be cast off in due time. Neither is the inequality of buds, varying more or less among themselves, any sound reason for overlooking their essential identity of structure. We have seen instances of this among Acalephs, and it is still more apparent among trees which produce simultaneously leaf and flower-buds, and even separate male and female flower-buds, as is the case with our Hazels, Oaks, etc.
It is not, however, my purpose here to describe the various modes of reproduction and multiplication among animals and plants, nor to discuss the merits of the different opinions respecting their numeric increase, according to which some persons hold that all types originated from a few primitive individuals, while others believe that the very numbers now in existence are part of the primitive plan, and essential to the harmonious relations existing between the animal and vegetable world. I would only attempt to show that in the plan of Creation the maintenance of types has been secured through a variety of means, but under such limitations, that, within a narrow range of individual differences, all representatives of one kind of animals agree with one another, whether derived from eggs, or produced by natural division, or by budding; and that the constancy of these normal processes of reproduction, as well as the uniformity of their results, precludes the idea that the specific differences among animals have been produced by the very means that secure their permanence of type. The statement itself implies a contradiction, for it tells us that the same influences prevent and produce change in the condition of the Animal Kingdom. Facts are all against it; there is not a fact known to science by which any single being, in the natural process of reproduction and multiplication, has diverged from the course natural to its kind, or in which a single kind has been transformed into any other. But this once established, and setting aside the idea that Embryology is to explain to us the origin as well as the maintenance of life, it yet has most important lessons for us, and the field it covers is constantly enlarging as the study is pursued. The first and most important result of the science of Embryology was one for which the scientific world was wholly unprepared. Down to our own century, nothing could have been farther from the conception of anatomists and physiologists than the fact now generally admitted, that all animals, without exception, arise from eggs. Though Linnaeus had already expressed this great truth in the sentence so often quoted,—"Omne vivum ex ovo,"—yet he was not himself aware of the significance of his own statement, for the existence of the Mammalian egg was not then dreamed of. Since then the discoveries of von Baer and others have shown not only that the egg is common to all living beings without exception, from the lowest Radiate to the highest Vertebrate, but that its structure is at first identical in all, composed of the same primitive elements and undergoing exactly the same process of growth up to the time when it assumes the special character peculiar to its kind. This is unquestionably one of the most comprehensive generalizations of modern times.