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Show 374 ACAL~PHA. CLASS III. ACALEPHA. . es Zoophyta which swim in the 0 th' rd class compr1s . . ur 1 t f the ocean an d I. n whose ,o rganization we can stlll wa er~ o w'hich it is true, are generally mere properceive vessel~, . ' d · the parenchyma of the ductions of the Intestines excavate In body. ORDER I. SIMPLICIA. The sim le Acalepha float and swim in ~he ocean by the It nate c!tractions and dilatations of their body, although ath eeirr substance is gelatinous an d W·i t h ou t any ap parent 1f1i bresd. The species of vessels observed in some of them are hod owe. out of their gelatinous substance; they frequently an evidently originate from the stomach, and do not occasion a true circulation. MEnusA, Lin. The Medusre are furnished superiorlt W•l t h a disk more or less SIMPLICIA. 375 convex, resembling the head of a mushroom, and called the umbel/a. Its contractions and dilatations assist the locomotion of the animal. The edges of this umbella., as well as the mouth, or the suckers more or less prolonged into pedicles which supply the want of it, in the middle of the inferior surface, are furnished with tentacula of various forms and very different sizes. These various degrees of complication have given rise to numerous divisions(!). We will designate by the general name of MEDUSA, Or Medusa proper, those which have a true mouth in the middle of the inferior surface, either simply open at the surface or prolonged into a pedicle. Under the name of We may reunite those in which this mouth is simple and not prolonged, nor furnished with arms. When there are no tentacula round the umbella they constitute the PuonoYNIA of Lamarck(2). When the circumference of the umbella is furnished with tentacula we have the ...:Eq,uonEA proper-...:Eq,uonEA of Peron-one of the most numerous of all the subgenera, particularly in the seas of hot climates(3). · Certain species are remarkable for having their inferior surface (1) For this genus, see the Prodromus of P~ron and Lesueur, Ann. du Mus., XIV, and XV; it is well to remember that their genera are frequently founded on bad figures, such as those of Baster and Borlasse and without having seen the animals; and that they have increased the number of species beyond all bounds. (2) The Plwrcini and Eulimenes of P6ron. (3) Medusa ~equorea, Gm.; Forsk., XXXI; Encyc., Vers, XCV, 1; .1EqU()1'etJ muonema, P~ron; Forsk., XXVIII, B;-Med. mucilagi1UJ8a, Chamiss., and Eisenh., Ac. Nat. Cur., X, part I, pl. xxx, f. 2, and the species engraved by M. Lesueur and indicated by P~ron, Ann. du Mus., XV, and by M. de Lamarck, Hist., des Anim. sans vert., II, 498, et seq. It is to be regretted that these plates are not to be purchased. I also add to them the P:zo.uu., and MELxTu of Peron. |
