Kitabı oku: «The Atlantic Monthly, Volume 09, No. 51, January, 1862», sayfa 2

The publication of Cuvier’s proposition, that the animal kingdom is built on four plans, created an extraordinary excitement throughout the scientific world. All naturalists proceeded to test it, and many soon recognized in it a great scientific truth,—while others, who thought more of making themselves prominent than of advancing science, proposed poor amendments, that were sure to be rejected on farther investigation. There were, however, some of these criticisms and additions that were truly improvements, and touched upon points overlooked by Cuvier. Blainville, especially, took up the element of form among animals,—whether divided on two sides, whether radiated, whether irregular, etc. He, however, made the mistake of giving very elaborate names to animals already known under simpler ones. Why, for instance, call all animals with parts radiating in every direction Actinomorpha or Actinozoaria, when they had received the significant name of Radiates? It seemed, to be a new system, when in fact it was only a new name. Ehrenberg, likewise, made an important distinction, when he united the animals according to the difference in their nervous systems; but he also incumbered the nomenclature unnecessarily, when he added to the names Anaima and Enaima of Aristotle those of Myeloneura and Ganglioneura.

But it is not my object to give all the classifications of different authors here, and I will therefore pass over many noted ones, as those of Burmeister, Milne, Edwards, Siebold and Stannius, Owen, Leuckart, Vogt, Van Beneden, and others, and proceed to give some account of one investigator who did as much for the progress of Zoölogy as Cuvier, though he is comparatively little known among us. Karl Ernst von Baer proposed a classification based, like Cuvier’s, upon plan; but he recognized what Cuvier failed to perceive,—namely, the importance of distinguishing between type (by which he means exactly what Cuvier means by plan) and complication of structure,—in other words, between plan and the execution of the plan. He recognized four types, which correspond exactly to Cuvier’s four plans, though he calls them by different names. Let us compare them.

Though perhaps less felicitous, the names of Baer express the same ideas as those of Cuvier. By the Peripheric he signified those in which all the parts converge from the periphery or circumference of the animal to its centre. Cuvier only reverses this definition in his name of Radiates, signifying the animals in which all parts radiate from the centre to the circumference. By Massive, Baer indicated those animals in which the structure is soft and concentrated, without a very distinct individualization of parts,—exactly the animals included by Cuvier under his name of Mollusks, or soft-bodied animals. In his selection of the epithet Longitudinal, Baer was less fortunate; for all animals have a longitudinal diameter, and this word was not, therefore, sufficiently special. Yet his Longitudinal type answers exactly to Cuvier’s Articulates,—animals in which all parts are arranged in a succession of articulated joints along a longitudinal axis. Cuvier has expressed this jointed structure in the name Articulates; whereas Baer, in his name of Longitudinal, referred only to the arrangement of joints in longitudinal succession, in a continuous string, as it were, one after another. For the Doubly Symmetrical type his name is the better of the two; for Cuvier’s name of Vertebrates alludes only to the backbone,—while Baer, who is an embryologist, signifies in his their mode of growth also. He knew what Cuvier did not know, that in its first formation the germ of the Vertebrate divides in two folds: one turning up above the backbone, to inclose all the sensitive Organs,—the spinal marrow, the organs of sense, all those organs by which life is expressed; the other turning down below the backbone, and inclosing all those organs by which life is maintained,—the organs of digestion, of respiration, of circulation, of reproduction, etc. So there is in this type not only an equal division of parts on either side, but also a division above and below, making thus a double symmetry in the plan, expressed by Baer in the name he gave it. Baer was perfectly original in his conception of these four types, for his paper was published in the very same year with that of Cuvier. But even in Germany, his native land, his ideas were not fully appreciated: strange that it should be so,—for, had his countrymen recognized his genius, they might have claimed him as the compeer of the great French naturalist.

Baer also founded the science of Embryology, under the guidance of his teacher, Dollinger. His researches in this direction showed him that animals were not only built on four plans, but that they grew according to four modes of development. The Vertebrate arises from the egg differently from the Articulate,—the Articulate differently from the Mollusk,—the Mollusk differently from the Radiate. Cuvier only showed us the four plans as they exist in the adult; Baer went a step farther, and showed us the four plans in the process of formation. But his greatest scientific achievement is perhaps the discovery that all animals originate in eggs, and that all these eggs are at first identical in substance and structure. The wonderful and untiring research condensed into this simple statement, that all animals arise from eggs and that all those eggs are identical in the beginning, may well excite our admiration. This egg consists of an outer envelope, the vitelline membrane, containing a fluid more or less dense, the yolk; within this is a second envelope, the so-called germinative vesicle, containing a somewhat different and more transparent fluid, and in the fluid of this second envelope float one or more so-called germinative specks. At this stage of their growth all eggs are microsopically small, yet each one has such tenacity of its individual principle of life that no egg was ever known to swerve from the pattern of the parent animal that gave it birth.

III

From the time that Linnæus showed us the necessity of a scientific system as a framework for the arrangement of scientific facts in Natural History, the number of divisions adopted by zoölogists and botanists increased steadily. Not only were families, orders, and classes added to genera and species, but these were further multiplied by subdivisions of the different groups. But as the number of divisions increased, they lost in precise meaning, and it became more and more doubtful how far they were true to Nature. Moreover, these divisions were not taken in the same sense by all naturalists: what were called families by some were called orders by others, while the orders of some were the classes of others, till it began to be doubted whether these scientific systems had any foundation in Nature, or signified anything more than that it had pleased Linnæus, for instance, to call certain groups of animals by one name, while Cuvier had chosen to call them by another.

These divisions are, first, the most comprehensive groups, the primary divisions, called branches by some, types by others, and divided by some naturalists into so-called sub-types, meaning only a more limited circumscription of the same kind of group; next we have classes, and these also have been divided into sub-classes, then orders and sub-orders, families, sub-families, and tribes; then genera, species, and varieties. With reference to the question, whether these groups really exist in Nature or are merely the expression of individual theories and opinions, it is worth while to study the works of the early naturalists, in order to trace the natural process by which scientific classification has been reached; for in this, as in other departments of learning, practice has always preceded theory. We do the thing before we understand why we do it: speech precedes grammar, reason precedes logic; and so a division of animals into groups, upon an instinctive perception of their differences, has preceded all our scientific creeds and doctrines. Let us, therefore, proceed to examine the meaning of these names as adopted by naturalists.

When Cuvier proposed his four primary divisions of the animal kingdom, he added his argument for their adoption,—because, he said, they are constructed on four different plans. All the progress in our science since his time confirms this result; and I shall attempt to show that there are really four, and only four, such structural ideas at the foundation of the animal kingdom, and that all animals are included under one or another of them. But it does not follow, that, because we have arrived at a sound principle, we are therefore unerring in our practice. From ignorance we may misplace animals, and include them under the wrong division. This is a mistake, however, which a better insight into their organization rectifies; and experience constantly proves, that, whenever the structure of an animal is perfectly understood, there is no hesitation as to the head under which it belongs. We may consequently test the merits of these four primary groups on the evidence furnished by investigation. It has already been seen that these plans may be presented in the most abstract manner without any reference to special animals. Radiation expresses in one word the idea on which the lowest of these types is based. In Radiates we have no prominent bilateral symmetry, as in all other animals, but an all-sided symmetry, in which there is no right and left, no anterior and posterior extremity, no above and below. They are spheroidal bodies; yet, though many of them remind us of a sphere, they are by no means to be compared to a mathematical sphere, but rather to an organic sphere, so loaded with life, as it were, as to produce an infinite variety of radiate symmetry. The whole organization is arranged around a centre toward which all the parts converge, or, in a reverse sense, from which all the parts radiate. In Mollusks there is a longitudinal axis and a bilateral symmetry; but the longitudinal axis in these soft concentrated bodies is not very prominent; and though the two ends of this axis are distinct from each other, the difference is not so marked that we can say at once, for all of them, which is the anterior and which the posterior extremity. In this type, right and left have the preponderance over the other diameters of the body. The sides are the prominent parts,—they are charged with the important organs, loaded with those peculiarities of the structure that give it character. The Oyster is a good instance of this, with its double valve, so swollen on one side, so flat on the other. There is an unconscious recognition of this in the arrangement of all collections of Mollusks; for, though the collectors do not put up their specimens with any intention of illustrating this peculiarity, they instinctively give them the position best calculated to display their distinctive characteristics, and to accomplish this they necessarily place them in such a manner as to show the sides. In Articulates there is also a longitudinal axis of the body and a bilateral symmetry in the arrangement of parts; the head and tail are marked, and the right and left sides are distinct. But the prominent tendency in this type is the development of the dorsal and ventral region; here above and below prevail over right and left. It is the back and the lower side that have the preponderance over any other part of the structure in Articulates. The body is divided from end to end by a succession of transverse constrictions, forming movable rings; but the character of the animal, its striking features, are always above or below, and especially developed on the back. Any collection of Insects or Crustacea is an evidence of this; being always instinctively arranged in such a manner as to show the predominant features, they uniformly exhibit the back of the animal. The profile view of an Articulate has no significance; whereas in a Mollusk, on the contrary, the profile view is the most illustrative of the structural character. In the highest division, the Vertebrates, so characteristically called by Baer the Doubly Symmetrical type, a solid column runs through the body with an arch above and an arch below, thus forming a double internal cavity. In this type, the head is the prominent feature; it is, as it were, the loaded end of the longitudinal axis, so charged with vitality as to form an intelligent brain, and rising in man to such predominance as to command and control the whole organism. The structure is arranged above and below this axis, the upper cavity containing all the sensitive organs, and the lower cavity containing all those by which life is maintained.

While Cuvier and his followers traced these four distinct plans, as shown in the adult animal, Baer opened to us a new field of investigation in the embryology of the four types, showing that for each there was a special mode of growth in the egg. Looking at them from this point of view, we shall see that these four types, with their four modes of growth, seem to fill out completely the plan or outline of the animal kingdom, and leave no reason to expect any further development or any other plan of animal life within these limits. The eggs of all animals are spheres, such as I have described them; but in the Radiate the whole periphery is transformed into the germ, so that it becomes, by the liquefying of the yolk, a hollow sphere. In the Mollusks, the germ lies above the yolk, absorbing its whole substance through the under side, thus forming a massive close body instead of a hollow one. In the Articulate, the germ is turned in a position exactly opposite to that of the Mollusk, and absorbs the yolk upon the back. In the Vertebrate, the germ divides in two folds, one turning upward, the other turning downward, above and below the central backbone. These four modes of development seem to exhaust the possibilities of the primitive sphere, which is the foundation of all animal life, and therefore I believe that Cuvier and Baer were right in saying that the whole animal kingdom is included under these four structural ideas.

Leuckart proposed to subdivide the Radiates into two groups: the Coelenterata, including Polyps and Acalephs or Jelly-Fishes,—and Echinoderms, including Star-Fishes, Sea-Urchins, and Holothurians. His reason for this distinction is the fact that in the latter the organs are inclosed within walls of their own, distinct from the body-wall; whereas in the former the organs are formed by internal folds of the outer wall of the body, as in the Polyps, or are hollowed out of the substance of the body, as in Jelly-Fishes. This implies no difference in the plan, but merely a difference in the execution of the plan. Both are equally radiate in their structure; and when Leuckart separated them as distinct primary types, he mistook a difference in the material expression of the plan for a difference in the plan itself. So some naturalists have distinguished Worms from the other Articulates as a separate division. But the structural plan of this type is a body divided by transverse constrictions or joints; and whether those joints are uniformly arranged from one end of the body to the other, as in the Worms, or whether the front joints are soldered together so as to form two regions of the body, as in Crustacea, or divided so as to form three regions of the body, as in winged Insects, does not in the least affect the typical character of the structure, which remains the same in all. Branches or types, then, are natural groups of the animal kingdom, founded on plans of structure or structural ideas.

What now are classes? Are they lesser divisions, differing only in extent, or are they founded on special characters? I believe the latter view to be the true one, and that class characters have a significance quite different from that of their mere range or extent. These divisions are founded on certain categories of structure; and were there but one animal of a class in the world, if it had those characters on which a class is founded, it would be as distinct from all other animals as if its kind were counted by thousands. Baer approached the idea of the classes when he discriminated between plan of structure or type and the degree of perfection in the structure. But while he understands the distinction between a plan and its execution, his ideas respecting the different features of structure are not quite so precise. He does not, for instance, distinguish between the complication of a given structure and the mode of execution of a plan, both of which are combined in what he calls degrees of perfection. And yet, without this distinction, the difference between classes and orders cannot be understood; for classes and orders rest upon a just appreciation of these two categories, which are quite distinct from each other, and have by no means the same significance. Again, quite distinct from both of these is the character of form, not to be confounded either with complication of structure, on which orders are based, or with the execution of the plan, on which classes rest. An example will show that form is no guide for the determination of classes or orders. Take, for instance, a Beche-de-Mer, a member of the highest class of Radiates, and compare it with a Worm. They are both long cylindrical bodies; but one has parallel divisions along the length of the body, the other has the body divided by transverse rings. Though in external form they resemble each other, the one is a worm-like Radiate, the other is a worm-like Articulate, each having the structure of its own type; so that they do not even belong to the same great division of the animal kingdom, much less to the same class. We have a similar instance in the Whales and Fishes,—the Whales having been for a long time considered as Fishes, on account of their form, while their structural complication shows them to be a low order of the class of Mammalia, to which we ourselves belong, that class being founded upon a particular mode of execution of the plan characteristic of the Vertebrates, while the order to which the Whales belong depends upon their complication of structure, as compared with other members of the same class. We may therefore say that neither form nor complication of structure distinguishes classes, but simply the mode of execution of a plan. In Vertebrates, for instance, how do we distinguish the class of Mammalia from the other classes of the type? By the peculiar development of the brain, by their breathing through lungs, by their double circulation, by their bringing forth living young and nursing them with milk. In this class the beasts of prey form a distinct order, superior to the Whales or the herbivorous animals, on account of the higher complication of their structure; and for the same reason we place the Monkeys above them all. But among the beasts of prey we distinguish the Bears, as a family, from the family of Dogs, Wolves, and Cats, on account of their different form, which does not imply a difference either in the complication of their structure or in the mode of execution of their plan.

AGNES OF SORRENTO

CHAPTER XVIII.
THE PENANCE

The course of our story requires us to return to the Capuchin convent, and to the struggles and trials of its Superior; for in his hands is the irresistible authority which must direct the future life of Agnes.

From no guilty compliances, no heedless running into temptation, had he come to love her. The temptation had met him in the direct path of duty; the poison had been breathed in with the perfume of sweetest and most life-giving flowers: nor could he shun that temptation, nor cease to inhale that fatal sweetness, without confessing himself vanquished in a point where, in his view, to yield was to be lost. The subtle and deceitful visit of Father Johannes to his cell had the effect of thoroughly rousing him to a complete sense of his position, and making him feel the immediate, absolute necessity of bringing all the energy of his will, all the resources of his nature to bear on its present difficulties. For he felt, by a fine intuition, that already he was watched and suspected;—any faltering step now, any wavering, any change in his mode of treating his female penitents, would be maliciously noted. The military education of his early days had still left in his mind a strong residuum of personal courage and honor, which made him regard it as dastardly to flee when he ought to conquer, and therefore he set his face as a flint for victory.

But reviewing his interior world, and taking a survey of the work before him, he felt that sense of a divided personality which often becomes so vivid in the history of individuals of strong will and passion. It seemed to him that there were two men within him: the one turbulent, passionate, demented; the other vainly endeavoring by authority, reason, and conscience to bring the rebel to subjection. The discipline of conventual life, the extraordinary austerities to which he had condemned himself, the monotonous solitude of his existence, all tended to exalt the vivacity of the nervous system, which, in the Italian constitution, is at all times disproportionately developed; and when those weird harp-strings of the nerves are once thoroughly unstrung, the fury and tempest of the discord sometimes utterly bewilders the most practised self-government.

But he felt that something must be done with himself, and done immediately; for in a few days he must again meet Agnes at the confessional. He must meet her, not with weak tremblings and passionate fears, but calm as Fate, inexorable as the Judgment-Day. He must hear her confession, not as man, but as God; he must pronounce his judgments with a divine dispassionateness. He must dive into the recesses of her secret heart, and, following with subtile analysis all the fine courses of those fibres which were feeling their blind way towards an earthly love, must tear them remorselessly away. Well could he warn her of the insidiousness of earthly affections; better than any one else he could show her how a name that was blended with her prayers and borne before the sacred shrine in her most retired and solemn hours might at last come to fill all her heart with a presence too dangerously dear. He must direct her gaze up those mystical heights where an unearthly marriage awaited her, its sealed and spiritual bride; he must hurry her footsteps onward to the irrevocable issue.

All this was before him. But ere it could be done, he must subdue himself,—he must become calm and pulseless, in deadly resolve; and what prayer, what penance might avail for this? If all that he had already tried had so miserably failed, what hope? He resolved to quit for a season all human society, and enter upon one of those desolate periods of retreat from earthly converse well known in the annals of saintship as most prolific in spiritual victories.

Accordingly, on the day after the conversation with Father Johannes, he startled the monks by announcing to them that he was going to leave them for several days.

“My brothers,” he said, “the weight of a fearful penance is laid upon me, which I must work out alone. I leave you today, and charge you not to seek to follow my footsteps; but, as you hope to escape hell, watch and wrestle for me and yourselves during the time I am gone. Before many days I hope to return to you with renewed spiritual strength.”

That evening, while Agnes and her uncle were sitting together in their orange-garden, mingling their parting prayers and hymns, scenes of a very different description surrounded the Father Francesco.

One who looks on the flowery fields and blue seas of this enchanting region thinks that the Isles of the Blest could scarcely find on earth a more fitting image; nor can he realize, till experience proves it to him, that he is in the immediate vicinity of a weird and dreary region which might represent no less the goblin horrors of the damned.

Around the foot of Vesuvius lie fair villages and villas garlanded with roses and flushing with grapes whose juice gains warmth from the breathing of its subterraneous fires, while just above them rises a region more awful than can be created by the action of any common causes of sterility. There, immense tracts sloping gradually upward show a desolation so peculiar, so utterly unlike every common solitude of Nature, that one enters upon it with the shudder we give at that which is wholly unnatural. On all sides are gigantic serpent convolutions of black lava, their immense folds rolled into every conceivable contortion, as if, in their fiery agonies, they had struggled and wreathed and knotted together, and then grown cold and black with the imperishable signs of those terrific convulsions upon them. Not a blade of grass, not a flower, not even the hardiest lichen, springs up to relieve the utter deathliness of the scene. The eye wanders from one black, shapeless mass to another, and there is ever the same suggestion of hideous monster life,—of goblin convulsions and strange fiend-like agonies in some age gone by. One’s very footsteps have an unnatural, metallic clink, and one’s garments brushing over the rough surface are torn and fretted by its sharp, remorseless touch,—as if its very nature were so pitiless and acrid that the slightest contact revealed it.

The sun was just setting over the beautiful Bay of Naples,—with its enchanted islands, its jewelled city, its flowery villages, all bedecked and bedropped with strange shiftings and flushes of prismatic light and shade, as if they belonged to some fairy-land of perpetual festivity and singing,—when Father Francesco stopped in his toilsome ascent up the mountain, and, seating himself on ropy ridges of black lava, looked down on the peaceful landscape.

Above his head, behind him, rose the black cone of the mountain, over whose top the lazy clouds of thin white smoke were floating, tinged with the evening light; around him the desolate convulsed waste,—so arid, so supernaturally dreary; and below, like a soft enchanted dream, the beautiful bay, the gleaming white villas and towers, the picturesque islands, the gliding sails, flecked and streaked and dyed with the violet and pink and purple of the evening sky. The thin new moon and one glittering star trembled through the rosy air.

The monk wiped from his brow the sweat that had been caused by the toil of his hurried journey, and listened to the bells of the Ave Maria pealing from the different churches of Naples, filling the atmosphere with a soft tremble of solemn dropping sound, as if spirits in the air took up and repeated over and over the angelic salutation which a thousand earthly lips were just then uttering. Mechanically he joined in the invocation which at that moment united the hearts of all Christians, and as the words passed his lips, he thought, with a sad, desolate longing, of the hour of death of which they spake.

“It must come at last,” he said. “Life is but a moment. Why am I so cowardly? why so unwilling to suffer and to struggle? Am I a warrior of the Lord, and do I shrink from the toils of the camp, and long for the ease of the court before I have earned it? Why do we clamor for happiness? Why should we sinners be happy? And yet, O God, why is the world made so lovely as it lies there, why so rejoicing, and so girt with splendor and beauty, if we are never to enjoy it? If penance and toil were all we were sent here for, why not make a world grim and desolate as this around me?—then there would be nothing to seduce us. But our path is a constant fight; Nature is made only to be resisted; we must walk the sharp blade of the sword over the fiery chasm to Paradise. Come, then!—no shrinking!—let me turn my back on everything dear and beautiful, as now on this landscape!”

He rose and commenced the perpendicular ascent of the cone, stumbling and climbing over the huge sliding blocks of broken lava, which grated and crunched beneath his feet with a harsh metallic ring. Sometimes a broken fragment or two would go tinkling down the rough path behind him, and sometimes it seemed as if the whole loose black mass from above were about to slide, like an avalanche, down upon his head;—he almost hoped it would. Sometimes he would stop, overcome by the toil of the ascent, and seat himself for a moment on a black fragment, and then his eye would wander over the wide and peaceful panorama below. He seemed to himself like a fly perched upon some little roughness of a perpendicular wall, and felt a strange airy sense of pleasure in being thus between earth and heaven. A sense of relief, of beauty, and peacefulness would steal over him, as if he were indeed something disfranchised and disembodied, a part of the harmonious and beautiful world that lay stretched out beneath him; in a moment more he would waken himself with a start, and resume his toilsome journey with a sullen and dogged perseverance.

At last he gained the top of the mountain,—that weird, strange region where the loose, hot soil, crumbling beneath his feet, was no honest foodful mother earth, but an acrid mass of ashes and corrosive minerals. Arsenic, sulphur, and many a sharp and bitter salt were in all he touched, every rift in the ground hissed with stifling steam, while rolling clouds of dun sullen smoke, and a deep hollow booming, like the roar of an immense furnace, told his nearness to the great crater. He penetrated the sombre tabernacle, and stood on the very brink of a huge basin, formed by a wall of rocks around a sunken plain, the midst of which rose the black cone of the subterraneous furnace, which crackled and roared and from time to time spit up burning stones and cinders or oozed out slow ropy streams of liquid fire.

The sulphurous cliffs were dyed in many a brilliant shade of brown and orange by the admixture of various ores, but their brightness seemed strange and unnatural, and the dizzying whirls of vapor, now enveloping the whole scene in gloom, now lifting in this spot and now in that, seemed to magnify the dismal pit to an indefinite size. Now and then there would come up from the very entrails of the mountain a sort of convulsed sob of hollow sound, and the earth would quiver beneath his feet, and fragments from the surrounding rocks would scale off and fall with crashing reverberations into the depth beneath; at such moments it would seem as if the very mountain were about to crush in and bear him down in its ruins.