Birds are divided, according to the form of their bills, into six orders : Acci. pitres ; as eagles, vultureS, and hawks. Pica; as crows, jackdaws, humming birds, and parrots. Anseres ; as ducks, swans, and gulls. Grallm ; as herons, woodcocks, and ostriches. Galling ; as peacocks, pheasants, turkies, and corn. mon fowls. And, lastly, Passeres ; com prehending sparrows, larks, swallows, thrushes, and doves. The Amphibia are in some respects very nearly allied to birds : but their blood is little warmer than the surrounding medium. Their respi ration is not necessarily performed in a continual succession of alternations, since the whole of their blood does not pass through the lungs, and the circulation may continue without interruption in other parts, although it may be impeded in these organs for want of the motion of respiration. They are very tenacious of life ; it has been asserted on good autho rity, that some of them have lived many years without food, inclosed in hollow trees, and even in the middle of stones : and they often retain vestiges of life some days after the loss of their hearts. Their eggs are generally covered with a mem brane only. They have sometimes an in termediate stage of existence, in which all their parts are,not yet developed, as we observe in the tadpole; and in this re spect they resemble the class of insects. They are now universally considered as divided into two orders only ; Reptilia : as the tortoise, the dragon, or flying lizard, the frog, and the toad ; all these have tour feet: but the animals which belong to the order Serpentes are without feet. Most of the serpentes are perfectly inno cent, but others have fangs, by which they instil a poisonous fluid into the wounds that they make. In England the viper is the only venomous serpent ; it is known by its dark brown colour, and by a stripe of whitish spots running along its back ; but to mankind its bite is seldom, if ever fatal.
The first three classes of animals have lungs, as we have already seen, for respi ration, and receive air by the mouth ; those which have gills, and red blood, are fishes, residing either in fresh or in salt water, or indifferently in both : their eggs are involved in a membrane, and have no albumen.
Of the six orders of fishes, four have regular gills, supported by little bones ; and they are distinguished according to the place of their ventral fins, into Apodes, as the eel and lamprey : Jugulares, as the cod : Thoracici, as the sole and perch : and Abdominales, as the salmon and pike, distinctions which appear to be perfectly artificial, although useful in a systematic arrangement. The two remaining orders are without bones in the gills, those of the one being soft, and of the other carti laginous or gristly. These are, the Bran chiostegi and Chondropterygii of Artedi, which Linnxus, from a mistake, classed among the Amphibia. The sun fish, the lump fish, the fishing frog, and the sea horse, are of the fbrmer, and the sturgeon, the skate, and the shark, of the latter or der.
Insects derive their name from being almost always divided, into a head, tho rax, and abdomen, with very slender in. tervening portions : although these divi sions do not exist in all insects. They are usually oviparous ; they respire, but not by the mouth ; they have a number of little orifices on each side of the abdomen by which the air is received into their ramified trachea ; and if these are stop ped with oil, they are suffocated. Instead of bones, they have a hard integument or shell. Their mouths are formed on con structions extremely various, but gene rally very complicated : Fabricius has made these parts the basis of his classifi cation ; but from their minuteness in most species, the method is, in practice, insuper ably inconvenient : and the only way, in which such characters can be rendered really useful, is when they are employed in the subdivision of the genera, as deter mined from more conspicuous distinctions.
Insects have most frequently jaws, and often several pairs, but they are always so placed as to open laterally or horizon tally. Sometimes, instead of jaws, they have a trunk, or proboscis. In general they pass through four stages of exist ence, the egg, the larva or stage of growth, the pupa, or chrysalis, which is usually in a state of torpor or complete inactivity, and the imago, or perfect insect, in its nuptial capacity. After the last change, the insect most frequently takes no food till its death.
The Linnxan orders of insects are the Coleoptera, with hard sheaths to their wings, generally called beetles; the Hem iptera, of which the sheaths are of a softer nature, and cross each other, as grasshop pers, bugs, and plant lice: the Lepidop tera, with dusty scales on their wings, as butterflies and moths ; the neuroptera, as the libellula, or dragon-fly, the may-fly and other insects with four transparent wings, but without stings ; the Hymenop tera, which have stings, either poisonous or not, as bees, wasps, and ichneumons ; the Diptera with two wings, as common flies and gnats, which have halteres, or balancing rods, instead of the second pair of wings ; and, lastly, the Aptera, without any wings, which form the seventh order, comprehending crabs, lobsters, shrimps, and prawns, for these are properly insects; spiders, scorpions, millepedes, centipedes, mites and monoculi. The Monoculus is a genus including the little active insects; found in pond-water, which are scarcely visible to the naked eye, as well as the Molucca which is the largest of all insects, being sometimes six teet long. Besides these there are several genera of apterous insects, which are parasitical and infest the human race as well as other animals.
The Vermes are the last and lowest of animated beings, yet some of them are not deficient either in magnitude or in beau ty. The most natural division of vermes is into five orders ; the Intestina, as earth worms and ascarides, which are distin guished by the want of moveable appen danges, or tentacula, from the Mollusca, such as the dew snail, the cuttle fish, the sea anemone, and the hydra, or fresh wa ter polype. The Testacea have shells of one or more pieces, and most of them in habit thq sea and are called shell fish, as the limpet, the periwinkle, the snail, the muscle, and the oyster, and the barnacle The order Zoophyta contains corallines, sponges, and other compound animals, united by a common habitation, which has the general appearance of a vegeta ble, although of animal origin; each of the little inhabitants resembling a hydra, or polype, imitating, by its extended arms, the appearance of an imperfect flower. The last order, Infusoria, is scarcely dis tinguished from the Intestina and Mollus ca by any other character than the mi nuteness of the individuals belonging to it, and their spontaneous appearance in animal and vegetable infusions, where we can discover no traces of the manner in which they are produced. The process by which their numbers are sometimes increased, is no less astonishing than their first production ; for several of the genera often appear to divide spontane ously, into two or more parts, which be come new and distinct animals, so that in such a case the question respecting the identity of an individual would be very difficult to determine. The volvox, and some of the vorticellm are remarkable for their continual rotatory motion, probably intended for the purpose of straining their food out of the water : while some other species of the vorticellm resemble fungi or corallines in miniature.