ACALEPILE (from astratsse, a nettle), Sta-.Vett/es, a class of marine invertebrate animals, belonging to the erulskingdom Radiates is now made to include a large number of animals, of which the genus .11edasa of Liunrcus may be taken as a type.
The genus Malasa was placed by Limuens in the second section of his l'srmes, via. Mollasea. The Mollusea were divided into six sections in the 'Systeme Nature;' and in the last of these, consisting of those mollitscoiul forms which had a central mouth below, Jfedusa stood as the first genus, followed by As feria., and I:chinas. The third section of limes (Testacea), with Chiron at its head, immediately followed. In this arrangement Jfedusa came between Novi* and .Asterias ; but in the body of the work it stands between Sepia and A steriaa The following is the Linmean definition of the genus Meyiusa : Body gelatinous, orbiculate, depressed. Mouth beneath, centnd.
The genus contained 12 species, and these consisted not only of true Medusa, hut of such genera as I'm-pita and reklla.
The A caleplar of Curvier (his third chum of Zoophytes) comprehend, to use his own terms, Zoophytes which swim in the sea, and an whose organization may be perceived vessels, which in truth are most frequently nothing but productions of the intestines, hollowed in the parenchyma of the body.
Cnvier's first order of Acaleplar, or Sea-Netles, consists of the Simple A cal.-plus, which he characterises as floating and swimming iu the sea by means of the contractions and dilatations of their body, their substance being gelatinous, without apparent fibres. The sort of vessels which are seen in some are hollowed in the gelatinous sub stance ; they often visibly come from the stomach, and do not give place to a true circulation.
The genera contained in this order are the great genus Metlusa, Linn., with its subgenera l'orpita and The grtait genus Medusa is characterised as having a disk more or less convex above, similar to that of a uniehroom, and called the umbrella. its contractions and dilatations concur to the motivity of the niiimaL The edges of this umbrella, as well as the mouth, or the suckers, more or less prolonged into pedicles, which take its place, in the middle of the lower surface, are furnished with tentacles of very different form and size. These different degrees of complication have given rise to very numerous divisions.
The Arse/Inv/sr/Rata form the second class of M. de Blainville'n
A etinoroaria. He observes that this class conosponds exactly to the genus Medusa of Linn:ems.
The following is 3L de Blninville's definition of this genus : Body free, regularly oval or circular, eubgelatinous, covered with an extremely fine skin, which is but little or not at all distinct, sustained or not by a solid subeartilaginows part, and provided with very diversiform radiated appendages.
intestinal canal limited to the stomach, and provided with a single orifice.
Ovaries multiplied, radiated, and opening in the interior of the etoituu:h.
M. de Blairsville goes on to state that their form, which is regulnr, is miserly always circular (the l'cicihr alone being oval), sometimes discoid or spheroidal, but most frequently hemispherical, which causes them to resemble our umbrellas, and has given rise to the distinction of their body by that name. This body is sometimes furnished in addition, in its circumference, with more or leas long cirrhi, to which the name of tentacles, or better, of tentaculiform cirrhi, has leen given.
The lower surface of the umbrella, he observers is moinetiines entirely naked, but in other cases is provided with numerous and dispersed tenteculifonn suckers, as in the l'orpiter and rehihr, or else with very diverniform appendages, capillaceous at least at their extremity, which zoologists hive termed antis, wheace the denomination of Brachideous which they have given to some species. These appendages or anus are sometimes free from their base, but in other cases are united, which unity produces a sort of peduncle, which has originated the designation of l'edancadated for those species that are no pro vided. In the middle of the lower surface of the umbrella of these Med sir is sometimes a species of peduncle fortned by a proboncidi form prolongation of the buccal orifice, and they are then called ProGosrideoms ; but in the greater number of cusses, the middle of the lower part of the umbrella is occupied by a more or hese con siderable mass, attaching itself to the body by four roots, in the fonn of a cross, no as to divide the buccal orifice into four semi lunar parts. This pediuiele, terminated by more or less numerous cepillaceona divisions, hex caused the name of Peduncalated, or to be applied to those 411cdesm which are provided with it.