ZOOPHYTES POLYPS OF OLD AUTHORS Polyps are gelatinous, oblong, or conical animals, with a con tractile body, an intestinal cavity, and an oval aperture, which is surrounded by a circlet of arms or tentacles. Besides these arms, there are no special organs of sense, at least in the greater number of Polyps, though all appear to be very sensible to the stimulus of light. Propagation is effected partly by eggs, partly by germs or buds ; in many instances the last are not detached from the parent stem, and thus there arise compound animals, different individuals being connected. Our Polyps were, for the most part, unknown to the ancients, and under this name entirely unknown. By it they understood naked molluscs of the form of the sepia, especially that genus which is now called Octopus by Zoologists. From analogy, and from some resemblance of form, Reaumer and Jussieu first gave the name, Polyp, to those fresh water animals that had been described by Trembley, and which were provided with a circlet of arms.
To this class belong many marine animals, which, at first sight, rather resemble plants than animals. Formerly, these so-called sea plants were, on account of the hardness of the calcareous substance of which they consist, referred to the mineral kingdom, and corals were compared to branching crystallizations (Arbor Diane) and stalactites.
The ancients believed that corals were soft whilst in the sea, and only became hard in air.
Even among later authors, traces may be found of the same opinion, founded on defective observation, or on confusion of soft species with hard ones.
Up to the middle of the last century, it was the prevailing view that these corals belonged to the vegetable kingdom. Mar sigh, in 1706, observed, on the shore of the Mediterranean, some of these products, (Alcyonium, Corallium, Antipathes,) and found in their pores little bodies that contracted when the stem was removed from the water. Such bodies, or buds, he took to be flowers, and so believed, that at length the view was definitely established, which consigned these marine products to the vege table kingdom. But still, the animal odor which was observed, opposed this view, as well as the chemical investigations of Geof froy, of Lemery, and of Marsigli himself, which demonstrated ammoniacal constituents in the supposed sea-plants, just as in animal substances. Peysonnel, a physician of Marseilles, in 1723, upon repeated examinations, found Marsigli's plants to be animals.
Reaumer thought this notion very improbable, but after the discovery was confirmed by Trembley and Bernard de Jussieu, (a celebrated botanist,) he adopted the views of Peysonnel, and Linnus accordingly transferred the coral and stone plants to the animal kingdom. Polyps are either naked, or are provided with a body more or less hard, which they surround like a bark, or by which they are surrounded.