« PreviousContinue »
Select Books on Botany. Dr. Smith's Introduction to Physiological and Systematical Botany, 8vo. with numerous plates, to which this chapter is indebted. It is an excellent work. Wakefield's Botany, 12 mo. Milne's Botanical Dictionary, svo. Hull's Botany, 2 vols., 8vo. Lee's Introduction to Botany, a new and improved edition, svo. Curtis' Lectures, 8vo. The Botanical Magazine, 8vo. originally begun by Mr. Curtis, and continued by Dr. Sims, may be considered as the foundation of the present improved state of botanical knowledge. Sowerby's Botany,
CHAP III.- ANIMAL KINGDOM. SEVERAL scientific and ingenious classifications or arrangements of the animal kingdom into classes, orders, genera, and species, have been successively adopted ; among which, that of M. Cuvier, the celebrated French anatomist, must be allowed to possess a very high degree of merit. Though the arrangement of M. Cuvier eviuces great anatomical precision, and the highest philosophical knowledge of animals, yet, upon the whole, it has a coma plicated and forbidding appearance to a general reader, and is, of course, less immediately attractive than the more simple arrangement of Linnæus, which divides the animal kingdom into six classes ;-mammaliu, uyfs, am phibiu, pisces, insectu, vermes, or such as suckle their young; birds; creatures living equally on land, or in water; fishes; insects; and worms. Each of these classes is subdivided into orders, genera, species, and varieties of those species. But, as we have commenced with the unorganized departments of nature, we shall reverse this arrangement; beginning with the lowest stages of animal existence, and ascending the scale of being till we arrive at man.
Class I. Zoophytes and worms. This class, vermes, is divided by Linnæus into mollusca, vermes, zoophyta and animalcula infusoria ; or, softbodied animals, plant-animals, worms, and animalcules of infusions. Nearly all the animals of the class vermes, have but slow locomotive powers. Many of them have arterial and venous vessels, in which the blood undergoes a real
circulation ; but these are by no means common to the whole class. In some of them eyes and ears are very perceptible, while others seem to enjoy only the senses of taste and touch, which are never wanting. Many have no distinct head, and most of them are without feet. The whole of these creatures are very tenacious of life. In most of them, parts that have been destroyed, will afterwards be re-produced.
1. 200PHYTA, zoophytes, or plant-animals, seem to hold a middle station between vegetables and animals. Most of them deprived of locomotion, are fixed by stems that take root in the crevices of rocks, among sand, orin other situatious. The genus hydra or polype first deserves our notice. These curious animals are found adhering to the stems of aquatic plants, or to the under-surfaces of the leaves. The species are multiplied by vegetation, one or two or even more young ones emerging gradually from the sides of the parent animal ; and these young are frequently again prolífic, so that it is not uncommon to see two or three generations at once in the same polype. But the most curious particular respecting this animal is, its multiplication by dissection. It may be cut in every direction, and even into very minute divisions, and not only the parent stock will remain uninjured, but every section will become a perfect animal. Even when turned inside out, it suffers no material injury: for in this state it will soon begin to take food, and to perform all its other animal functions. When one polype is introduced by the tail into another's body, the two heads unite and form one individual.
The hard or horny zoophytes are known by the name of corals, and are equally of an animal nature with the polype. The whole coral continuing to grow as an animal, and to form by secretion, the strong or stony part of the coral, which at once may be considered as its bone and its habitation, and which it has no power of leaving. * Some of the coral tribe have their animal part approach
* Our hills are in many places full of them, and some rocks are entirely of their formation, Many seas are becoming every year more difficult to navigate, being nearly choaked up by the habitations of animals, almost too small for human perception.
ing more to that of a medusa, than of a polype. Of this kind are those numerous corals known by the name of madrepores. The smaller corals are termed corallines, or sea-mosses ; and are actually so many ramified sea-polypes, covered with a horny case, to defend them from the injuries which they would otherwise be liable to, in the boisterous elements in which they are destined to reside. The principal genera of the corullines are: 1. Sertularid. 2. Tubularia. 3. Flustra. Those of the corals are, 1. Gorgonia, Venus' fau. 2. Isis. 3. Madrepora. 4. Millepora. 5. Tubipora.
II. ANIMALCULA INFUSORIA, or animalcules found in different liquids. These minute beings are principally to be observed by the aid of the microscope, in such fluids as have had any animal or vegetable substance infused in them. The ancients were totally wacquainted with this class of beings. To them, the mite was made the ne plus ultra, or utmost bound of animal minuteness ; but the moderns, assisted by that powerful instrument the microscope, have discovered whole tribes of animals, compared with which even mites may be considered as a kind of elephants. The principal genera are, 1. Vorticella. The v. convalluria, is a beautiful transparent animalcule, formed like a bell-shaped flower, and furnished with a long tail or stem, by which it generally affixes itself to the stems and under-surface of the common lemna minor, or duck-weed.
racemosa is still more elegant. It is found in clear stagnant waters during the summer months, attached to the stalks of the smaller water-plants. If submitted to the examination of the microscope, several small ramifications will be perceived to issue from a single stem, each terminated by an apparent flower, like that of a convolvulus. The whole is in the highest degree transparent, and the alternate expansion and contraction of the seeming flowers, forms a highly curious and interesting spectacle. The v. rotatoria, or wheel-animal, so named from the apparent rapid motion of the head, is remarkable for its strange power of restoration to life and motion, after being dried many months in a glass. 5. Cercaria. The c. mutabilis, or changeable cercaria, is the cause of that fine, deep-green scum which appears on the surface of stagnant waters dora ing the summer months.
3. Trichoda. The t. sol is a globe or ball beset on all sides with very long diverging rays, having the appearance of a sun.
It is about the size of a small pin's head, and is generally affixed to the stem of some small water-plant. This animalcule may be pulled or torn in pieces, by means of a pair of needles or other convenient instruments, and in the space of a single hour, each piece will be apparently complete, and perfectly globular like the original. 4. Volvor. The v. globator often equals the size of a pin's head. In the advanced state of spring, and again in autumn, it appears in immense numbers in the clearer kinds of stagnant waters. Its motions are irregular, in all directions, and at the same time rolling or spinning as if on an axis. 5. The vibrio is the largest of all the animalcular tribe.' One species of the v. anguillula, or eel-vibrio, inhabits acid paste; when full-grown, it measures the tenth of an inch in length. It is viviparous, and frequently produces a tribe of young. * Its general appearance when magnified is that of an eel. The other species may be sometimes found in vinegar. 6,7. Cyclidium and Monas are exceedingly small; a species called the m. termo, when surveyed by the utmost powers of the microscope, still appears but as a kind of moving point, having merely a sensible diameter.
A countless swarm of animalcules will always appear in any vegetable infusion, after the space of a few days; as in the infusions of hay, beans, wheat, and other substances. The blueish appearance on the surface of plums, grapes, and many other fruits, is not a living world,' but a mere vegetable efflorescence, which regularly takes place on such kind of fruit.
III. The MOLLUSCA derive their name from the soft, fleshy nature of their body. This class includes those
If one of them be cut through the middle, several young ones coiled up and inclosed, each in a membrane, will be seen to proceed from the wound. More than 100 young have issued from a single parent.
+ Mr. Baker, the celebrated microscopic observer, with an instrumentof highly magnifying powers, saw these eels an inch and a half in diameter, and of a proportionate length. They swam up and down very briskly, the motion of their intestines was very visible; when the water dried up, they died in apparent agonies, and their mouthe opened very wide.
pulpy animals, which may either be destitute of an external covering, when they are called mollusca nuda, as the slug; or may be inclosed in one or more shells, as the snail, oyster, &c. when they are termed testacea.
1. Mollusca nuda are those soft-bodied animals, which are destitute of any truly shelly, or very hard integument; though some particular genera have a coriaceous or leathery covering Most of them are furnished with tentacula or feelers. The principal genera are: 1. Limax, slug. 2. Aplysia, a marine worm. 3. Doris, a sea-spail. Nereis. 5. Terebella. 6. Pyrosoma. 7. Nais. 8. Sepia, cuttle-fish.* 9. Calamary, Loligo, pen-fish, or ink-fish. 10. Medusa, sea-blubber, sea-nettles. 11. Holothuria. 12. Actinia, sea-anemone. 13. Asterius, star-fish. · 14. Echinus, sea-urchin.
2. Mollusca testacea, or soft-bodied animals furnished with shells, are divided into three assortments, called univalves, bivalves, and multivalves; meaning that the shelly cover consists either of one, two, or several parts or valves. A univulve shell may be exemplified by that of the common snail; for the shell is simple or undivided. A bivalve shell may be exemplified by a muscle, in which, as every one knows, the shell is composed of two pieces or valves; and lastly, a multinuive shell may be exemplified by any species of lepas or bernacle, in which the shelly covering of the animal is formed of several pieces or divisions. The shell-animals are produced from eggs, which in some species are gelatinous, or gluey; and in others, covered with a hard or calcareous shell: and the young animal eneiges from the egg with its shell on its back. The most famis liar and convincing proof of this may be obtained, by observing the evolution or hatching of the eggs of the common garden snail, as well as of several of the water-snails, which deposit eggs so transparent, that the motions of ihe young, with the shell on its back, may be very distinctly seen several days before the period of hatching.
* The well-known Chinese preparation, called Indian-ink, is supposed to be no other than the black liquor found in the body of this fish, carefully managed, perfumed, and formed into ornamental cakes. The eggs of this fish, of the size of small filberts and of a black colour, are frequently seen on the sea-shore, and are popularly termed seagrapes.