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more in detail in its proper place, this little spherical body, scarcely larger than a pea, is composed of upwards of five millions of fibres, which lock into one another by means of more than sixty-two thousand five hundred millions of teeth. If such be the complication of a portion only of the eye of that animal, how intricate must be the structure of the other parts of the same organ, having equally important offices! What exquisite elaboration must those textures have received, whose functions are still more refined ! What marvellous workmanship must have been exercised in the organization of the nerves and of the brain, those subtle instruments of the higher animal faculties, and of which even the modes of action are to us not merely inscrutable, but surpassing all our powers of conception !” — Vol. 1. pp. 59, 60.

Not the least interesting and useful portion of this work, is that which is devoted to the description of the structure and functions of those animals which occupy a place at or near the foot of nature's scale. Many of these are such as come under our common observation, and occasionally excite our particular attention, but concerning which we are very ignorant, and sometimes feel our ignorance to be rather uncomfortable. Such is the Asterias, or Star-fish, of which there are several species, but which is not a fish at all. Such is the Echinus, or Sea-urchin, or Sea-egg; and such is the Actinia, or Animal-flower, both of which genera have also several species under them. How often these are seen, — how often they are taken up in the hand, — how little is known of them. Nay, it is not an uncommon idea, that, because these things are apparently so insignificant, no one has ever taken the trouble, — we believe that is the expression, — taken the trouble to examine them, or write about them, or find out where their place is in nature, — if indeed they have a place, and are not anomalies and outlaws. Then there is the Medusa, or Jelly-fish, which we see floating and flapping in the water when the weather is calm, or lying helpless on the sand as the tide recedes ; has that ever been examined or described ? They have all been examined; they have all been described; they have all a place assigned to them in the ranks of creation; they have all a use and office. Their construction is known, their motions have been analyzed, the manner in which they take their food, and the process by which they digest it, have been traced by accurate observation; and a sketch of all this may be found, in a popular and intelligible form, in the treatise before us. VOL. XX. -30 s. VOL. II. NO. II.

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They all belong to the Zoöphyta, the fourth and lowest great division of animated nature; but, low as they are, they are not beneath the care of God. He who made us, and placed us in the rank which we occupy

alas ! how do we often occupy it ?—made them, and placed them in the rank which they occupy, and gave them their share of work and enjoyment.

Who that has ever crossed the Atlantic, has not seen at times in pleasant weather, the rainbow hues of that light little mariner, the Portuguese Man-of-War, as the sailors call him ? We have heard it called, by those who aimed to be more correct than the sailors, the Nautilus, and they have thought that in seeing it, they have seen the far-famed Nautilus. But the sailors are the more accurate party by far. They call it the Portuguese Man-of-War; - and who have a better right than they to name the creatures of the sea ? They do not rob another creature of its classical appellation, to bestow it on one to which it is altogether unlike. Though they are not naturalists, except in their own way, they have generally seen something of the world, the "watery world” in particular, and they know that a Portuguese Man-of-War is not a Nautilus. The scientific naturalists confirm their decision, and tell us that this animal, which they call the Physalia, belongs to the same division of the Zoöphytes, with the creatures already mentioned, while the Nautilus ranks among the Mollusca, in the second great division of animated nature; and that consequently there is about as wide a difference and distance between the latter and the former, as there is between a duck and a butterfly. The following is Dr. Roget’s brief but pretty description of the Physalia.

"A construction still more artificial is provided in another family of the same order, denominated the Physalida or Hydrostatic Acalepha. They have attained this latter appellation from their being rendered buoyant by means of vesicles filled with air, which enable them to float without the necessity of using any exertion for that purpose. The Physalia, or Portuguese Man-ofWar, as it is called, is furnished with a large air-bladder, of an oval shape, placed on the upper part of the body; and also with a membrane of a beautiful purple color, which, as in the Velella, serves as a sail. These Zoöphytes are met with in great numbers in the Atlantic Ocean, and more especially in its warmest regions, and at a considerable distance from land. In calm weather they float on the surface of the sea, rearing their purple crests, and appearing at first like large air-bubbles, but

distinguishable by the vivid hues of the tentacula which hang down beneath them. Nothing can exceed the beauty of the spectacle presented by a numerous fleet of these animals, quietly sailing in the tropical seas. Whenever the surface is ruffled by the slightest wind, they suddenly absorb the air from their vesicles, and, becoming thus specifically heavier than the water, immediately disappear, by diving into the still depths of the ocean. Ву what process they effect these changes of absorption and of reproduction of air yet remains to be discovered. Other genera, as the Physsophora, have several of these air-bladders; but in other respects resemble the ordinary Medusa, in having no membranous crest.” — Vol. 1. pp. 196, 197.

Much has of late years been discovered concerning the Infusoria, that wonderfully minute class of beings which has been brought to view by the powers of the microscope. Some kinds of them are so small and so numerous, that it has been computed by Professor Ehrenberg, the chief explorer in this region, that in a single drop of fluid there may be contained five hundred millions, about the number there is of human beings on the face of the earth. It has been ascertained that there are many distinct and permanent genera of these animalculæ; and such has been the perseverance of the abovenamed naturalist, that in their inexpressible diminutive bodies have been verified by him the processes of muscular action, circulation, and digestion ! From the abstract which Dr. Roget has given of these discoveries, we take the following account.

“ The Infusory animalcules, or Infusoria, were so named by Muller, a Danish naturalist, from the circumstance of their swarming in all infusions of vegetable or animal substances which have been kept for a sufficient time. They are, in general, far too minute to be perceptible to the naked eye: it is to the microscope alone, therefore, that we owe our knowledge of their exista ence, and of the curious phenomena they present : yet even the best instruments afford us but little insight into their real organis zation and physical conditions. On this account it is extremely difficult to assign their true place in the scale of animals. By most systematic writers they have been regarded as occupying the very lowest rank in the series, and as exemplifying the simplest of all possible conditions to which animal life can be reduced. Monads, which are the smallest of visible animalcules, have been spoken of as constituting the ultimate term of animality'; and some writers have even expressed doubts whether they really belong to the animal kingdom, and whether they should not rather be considered as the elementary molecules of organic

beings, separated from each other by the effects of chemical decomposition, and retaining the power of spontaneous, but irregular and indeterminate motion. It was conceived that all material particles belong to the one or the other of two classes; the first, wholly inert, and insusceptible of being organized; the second, endowed with a principle of organic aptitude, or capability of uniting into living masses, and constituting, therefore, the essential elements of all organization. According to this view, all vegetables or animals in existence would be mere aggregations of infusory animalcules, which gradually accumulate by continual additions to their numbers, derived from organic matter in the food : so that the body of man himself would be nothing more than a vast congregation of monads !

“ This bold and fanciful hypothesis, devised by Buffon, and recommended by its seductive appearance of simplicity, as well as by the glowing style and brilliant imagination of its author, has had many zealous partisans. The new world, which was disclosed to the wondering eyes of naturalists by the microscope, abounding in objects and in phenomena of which no conception could have been formed previously to the invention of that instrument, was peculiarly calculated to excite curiosity, and to inspire the hope of its revealing the secret of the living principle in the arrangement of the atoms of organic bodies. During the greater part of the last century, infusory animalcules were the subject of frequent and laborious microscopical research, and gave rise to endless conjecture and speculation as to their origin, their vitality, and their functions in the economy of nature. Notwithstanding their minuteness, considerable differences of organization were perceived to exist among them : but many naturalists still clung to the idea that monads, the most diminutive of the tribe, and whose very presence can be detected only by the application of the highest magnifying powers, are homogeneous globules of living matter, without organization, but endowed with the single attribute of voluntary motion : and even this property was denied to them by some authors.

“ All these fanciful dreams have been dispelled by the important discoveries of Ehrenberg, who has recently found that even the Monas termo is possessed of internal cavities for the reception and the digestion of its food ; and who has rendered it probable that their organization is equally complex with that of the larger species of infusoria, such as the Rotifera, in which he has succeeded in distinguishing traces of a muscular, a nervous, and even a vascular system. - Vol. 1. pp. 183 - 186.

The method, by which Ehrenberg arrived at his singular conclusions, is thus stated in another place.

“ Ever since the discovery of the animalcula of infusions, naturalists have been extremely desirous of ascertaining the nature of the organization of these curious beings; but, as no mode presented itself of dissecting objects of such extreme minuteness, it was only from the external appearances they present under the microscope, that any inferences could be drawn with regard to the existence and form of their internal organs. In most of the larger species, the opaque globules, seen in various parts of the interior, were generally supposed to be either the ova, or the future young, lodged within the body of the parent. In the Rotifer, or wheel animalcule of Spallanzani, a large central organ is plainly perceptible, which was by some imagined to be the heart; but which has been clearly ascertained by Bonnet to be a receptacle for food. Muller, and several other observers, have witnessed the larger animalcules devouring the smaller; and the inference was obvious that, in common with all other animals, they also must possess a stomach. But as no such structure had been rendered visible in the smallest species of insusoria, such as monads, it was too hastily concluded that these species were formed upon a different and a simpler model. Lamarck characterized them as being throughout of a homogeneous substance, destitute of mouth and digestive cavity, and nourished simply by means of the absorption of particles through the external surface of their bodies.

« The nature and functions of these singular beings long remained involved in an obscurity, which appeared to be impenetrable; but at length a new light has been thrown on the subject by Professor Ehrenberg, whose researches have recently disclosed fresh scenes of interest and of wonder in microscopic worlds, peopled with hosts of animated beings, almost infinite in number as in minuteness. In endeavouring to render the digestive organs of the infusoria more conspicuous, he hit upon the fortunate expedient of supplying them with colored food, which might communicate its tinge to the cavities into which it passed, and exhibit their situation and course. Obvious as this method may appear, it was not till after a labor of ten years that Ehrenberg succeeded in discovering the fittest substances, and in applying them in the manner best suited to exhibit the phenomena satisfactorily. We have already seen that Trembley had adopted the same plan for the elucidation of the structure of the hydra. Gleichen also had made similar attempts with regard to the infusoria ; but, in consequence of his having employed metallic or earthy coloring materials, which acted as poisons, instead of those which might serve as food, he failed in his endeavours. Equally unsuccessful were the trials made by Ehrenberg with the indigo and gum-lac of commerce, which are always contaminated with a certain quantity of white lead, a substance highly deleterious to all animals;

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