IV. NEUROPTEROUS.--Having four membranous and semi-transparent wings, veined like network; and the tail without a sting, as the dragon-fly and ephemera. V. HYMENOPTEROUS.--Having four membranous and semi-transparent wings, veined like network; and the tail armed with a sting, as the wasp and bee. VI. DIPTEROUS.--Having only two wings, as the common house-flies. VII. APTEROUS.--Having no wings, as the spiders. ORDERS OF VERMES, OR WORMS. The sixth and last Linnæan class consisted of Worms, or Vermes. These are slow of motion, and have soft and fleshy bodies. Some of them have hard internal parts, and others have crustaceous coverings. In some of the species, eyes and ears are very perceptible, whilst others appear to enjoy only the senses of taste and touch. Many have no distinct head, and most of them are destitute of feet. They are, in general, so tenacious of life, that parts which have been destroyed will be reproduced. These animals are principally distinguished from those of the other classes by having tentacula, or feelers, and are divided by Linnæus into five Orders: I. INTESTINA.--Are simple and naked, without limbs; some of them live within other animals, as the ascarides and tape-worms; others in water, as the leeches; and a few in the earth, as the earth-worm. II. MOLLUSCA.--Are simple animals, without shells, and furnished with limbs, as the cuttle-fish, medusa, star-fish, and sea-urchin. III. TESTACEA.--Are animals similar to the last, but covered with shells, as oysters, cockles, snails, and limpets. IV. LITHOPHYTA.--Are composite Polyps, dwelling in cells in a calcareous base which they produce, as corals and madrepores. V. ZOOPHYTA.--Are usually composite animals, but do not reside in stony cells. The coral, sponge, and polyps are instances of this order, which also includes the Infusorial Animalcules. _MODERN SYSTEM._ It will be found by reading the following sketch of the Modern System that the greatest change has taken place in the latter two classes. The others remain nearly the same in effect, though their distinctions are different, and the classes are not arranged in the same order. According to Cuvier, all animals are arranged in four great divisions, which are subdivided into classes and orders, as follows:--