SECTION II. Zoophytes, or Zoophytic-worms; Polypes; Corals; and Sponges. ZOOPHYTES, or Plant-animals, are so denominated from their existing in the shape of plants. Of these the genus Hydra, or Polype, deserves our first attention; not only from its wonderful nature and properties, but because it serves as a kind of standard or example of reference in many other genera of zoophytes more or less allied to it. The genus hydra or polype, comprehending the real or fresh. water polypes, was so named by Linnæus because in reality it affords phænomena similar to those recorded of the fabulous hydra of antiquity, which, when one head is cut off, produced others in its place. The character of the hydra, or polype, is a long, tubular body, possessing a great power of contraction and extension; affix. ing itself by the tail; and furnished at its upper or open end with a certain number of long arms, or tentacula, differing in number in the different species. The principal species are the brown, the yel lowish-grey, and the green polypes, or the hydra fusca, grisea, and viridis, of Linnæus. These curious animals may be found in small streams and in stagnant waters, adhering to the stems of aquatic plants, or to the under surfaces of the leaves, and other objects. They prey on small worms, monoculi, and many other animals which happen to occur in the same waters. If a polype be cut in two, the superior part will produce a new rior part will produce a new head and arms; weather, in the course of a very few days. If cut into three pieces, the middle portion will produce both the head and tail; and in short, polypes may be cut in all directions, and will still reproduce the deficient organs. The natural mode of propagation in this animal, is by shoots or offsets, in the manner of a plant: one or more branches or shoots proceeding from the parent stem, and dropping off when complete; and it frequently happens that these young branches will produce other branches before they themselves drop off from the parent; so that a polype may be found with several of its descendants still adhering tail, and the infe. and this, in warm by Count Marsigli, which seemed to prove them of a vegetable nature; for on gathering them perfectly fresh, and placing them in sea water, they appeared to put forth small flowers from all the minute cavities, or hollow points on the surface. These, therefore, were considered as a convincing proof that coral was a plant. The arguments against this theory were, the animal odour which they dif fused in burning, and a greater degree of sensibility in the supposed flowers than seemed quite consistent with the generality of plants. A very few years after Count Marsigli's discovery and description of the supposed flowers of coral, Dr. Peysonel, a French physician, from observations made on some parts of the European coasts, as well as on those of the West Indies, ventured to propose to the French Academy, a new theory relative to the nature of corals; in which he maintained, that the supposed flowers were real animals, allied to actiniæ; and that, in consequence, the corals should be con sidered as aggregates of animals, either forming, or at least inhabiting the calcareous substance of the coral in which they appeared. To this theory no great attention was paid; and several years elapsed before a farther advance was made in the knowledge of these bodies: but at length, about the year 1730, a Mr. Trembly, of Geneva, in searching after some small aquatic plants, happened to discover the animals now called polypes: these had indeed been discovered long before by Leewenhoeck, in Holland; but he only gave a general description of the animal, and observed that it multiplied by an apparent vegetation, but was ignorant of its power of reproduction after cutting: but Mr.Trembly, surprised at the singu lar appearance of a creature which had at once the aspect of a plant, and the motions of an animal, determined to try the experiment of cutting it, in order to ascertain its doubtful nature; and was beyond measure astonished to find that instead of destroying it, both parts seemed uninjured by the wound, and that in a very few days each had reproduced every limb that had been lost, and eat, and moved. as before. This discovery being announced, was at first considered by many as a fable; and it was even contended, that this division of animal life was in itself absolutely impossible, upon the principles of common sense, as well as of sound philosophy: but at length, the attention of all Europe being excited by the singularity of the cir cumstance, the animals were every where sought after, and experi ments made by cutting them in every possible direction, and their =་ real nature thus completely ascertained; and from subsequent observations it was found that the animals of most of the coral tribes, both hard and soft, were strongly allied to polypes, and were endowed with the same re-productive properties; while others were possessel of the same power, but seemed more allied to the actiniæ, or sea-anemonies, and to the medusæ, or sea-blubbers. Afterwards the celebrated Mr. Ellis, by repeated observations made about the British coasts, proved beyond all doubt, that the smaller corals, commonly known by the name of coralines, or sea-mosses, were actually so many ramified sea-polypes, covered with a kind of strong, horny case, to defend them from the injuries to which they would otherwise be liable, in the boisterous element in which they are des tined to reside. Mr. Ellis's observations on the harder, or stony corals, as well as the observations of many other philosophers, have at length proved also that these stony corals are equally of an animal nature; the whole coral continuing to grow as an animal, and to form by secre4tion, the strong or horny part of the coral, which at once may be considered as its bone and its habitation, which it has no power of leaving, and a coral of this kind is therefore a large compound zoophyte. [Shaw. Sponges afford us another curious proof of zoophytic life; each of which is characterised in the Linnæan system as a fixed animal, flexile, torpid, of various forms, composed either of reticulate fibres, or masses of small spines interwoven together, and clothed with a gelatinous flesh, full of small mouths on its surface, by which it absorbs and rejects water. After having been regarded at different periods as an organized living substance, of a doubtful kind; then as an inorganized substance; then as a vegetable; sponge is now advanced to the animal kingdom, and usually classed as we have arranged it above. So early as the days of Aristotle, it was noticed by the persons employed in collecting it, to shrink back when torn from the rocks, and was hence supposed to be in some way or other possessed of animal sensation: and this opinion, prevalent in the time of Aristotle, was still prevalent in that of Pliny.-For many ages afterwards, however, these naturalists appear to have been regarded as mistaken upon this subject, and sponges were again held to be altogether insentient substances. Marsigli first, in modern times, declared them to be entitled to the rank of vegetables; and Dr. Peysonell, towards the middle of the last century, sent two papers upon this subject to the Royal Society, both which are printed in its Transactions, in which he maintained that they were not vegetables, but animals; and pointed out what he conceived to be the mode of their growth and propagation. The idea had, indeed, been occasionally indulged for nearly half a century antecedently; but it was conceived too romantic and visionary for general adoption: and hence all the natural histories published at this period concur in the theory of Marsigli, and Bauhine, Lobel, Tournefort, Hill, and all the celebrated botanists of the day, give them free admission into the vegetable kingdom, and describe them as submarine plants. Ellis, however, seems to have settled the point in 1762: his observations and experiments were chiefly made upon the spongia tomentosa; he satisfactorily ascertained the existence of the animal inhabitant; remarked its contraction within its cells when exposed to pain or injury; the expiration and inspiration of water through its tubes; and established the position that sponge is an animal; and that the ends or openings of the branched tubes are the mouths by which it receives its nourishment and discharges its excrement: a position which chemistry has since abundantly supported by proving the ammoniacal property of the cellular matter of sponge. There are forty-nine species of this zoophyte, of which the chief, denominated from their shape or places of residence, are common sponge; downy sponge; grape sponge; lake and river sponge; coxcomb sponge. [Pantologia. SECTION IV. Molluscous Worms, or those without Shells. ONE of the simplest specimens we can refer to belonging to this elass, is the slug or limax. Among the more curious we may mention the following. 1. Sepia, Cuttle, or Ink-fish. This is one of the most extraordinary of the entire order. The |