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Show 330 ECl:liNODERMA T .A. ORDER I. PEDICELLAT A. . . . bed by organs of motion ex- The Pedicellata are distlngu~h ir skin is pierced with a elusively pecur l a r to them. d. ev ery regular sert. es, t h roug h number of 11. tt1 e r hole.s ' arrandg e tn branous tentacu1 a , eac h one driCal an mem . 1 which pass cy m . . k h'ch acts like a cuppmg-g ass. terminated by a httle dts w 1 1 which remains within the . f these tentacu a . . That portion o . effused through thetr enttre . 1 • a humour ts . 1 . body is vest?u ~r ' elled at the will of the amma mto cavity, and ts etther.pro? 1 tion . which it distends, or rethe exterior and c!hndri~al por hen 'the former sinks and be-turns to the interto~ vesl~h~s :longating and shortening their comes relaxed. It ts by t t cula and by fixing them by hundreds of little fee~ .or :; these animals effect their pro· their cup-like extremttleS' a d' g from these feet extend . Vessels procee m . h gressi ve mottons. d t their ranges, and whlc ter· to trunks which corrt~po~h:y form a system dis~inct from minate near the mou . b ved in some speetes(l ). that of the i~t~stinal v::e~~t: :~:ee very natural, but nume· Linnreus dtvtded th d f ch various species, that they d mpose o su rous genera,. an cdo {: ing three families. The may be constdere as orm AsTERIAS, Lin. . b d is divided into called because their o y . be Or Starfish, have been so f hich and underneath, lS t ( lly five) in the centre o w ' rays genera ' . mou th , that is also the anus. · • d Bolo- . tion of the Star-fish, Ursuu an 6 (1) For details resp~cting th~ org:~~~ raph of Tiedemann, Landshut, 181' thur1.a :, se e the splendid anatomical g in folio. PEDICELLATA. 331 The framework of their body is composed of small osseous pieces, variously combined, the arrangement of which merits examination. Their power of reproduction is very great, as they not only reproduce the rays which have been separately removed, but a single one with the central ray remaining will reproduce all the others; for this reason their figure is frequently irregular. In the AsTERIAs, Lam. Or Asterias properly so called, each ray has a longitudinal groove above, the sides of which are perforated by the little holes beforementioned, for the transmission of the feet. The rest of the inferior surface is furnished with small and movable spines. The whole surface is also pierced by pores, which allow a passage to tubes much smaller than the feet, that probably serve to absorb water, and convey it into the general cavity for a sort of respiration. On the middle of the body, and a little on one side, is a stony plate, with a corresponding internal canal, filled with a calcareous matter, which is thought to serve for the growth of the solid parts. Internally we find a large stomach, immediately on the mouth, from which two creca proceed to each ray, ramifying like trees, and suspended (each) to a sort of mesente1·y. There are also two ovaries in each ray, and it appears to us that they possess the faculty of selfimpregnation. A particular system of vessels is connected with their intestines, and another with their feet. M. Tiedemann thinks that their nervous system consists in a very fine thread which surrounds the mouth, and sends a branch to each foot, which runs between those organs exteriorly, and gives off two twigs internally. The osseous framework of each ray consists of a sort of column extending along the inferior surface, and composed of vertebrre articulated with each other, from which proceed the cartilaginous branches that support the exterior envelope. Between the roots of these branches are the holes that transmit the feet. Other osseous pieces, frequently furnished with movable spines, are observed on the lateral edges of the branches in many species. Some of this genus have the figure of a pentagon with rectilinear sides, rathe1· than that of a star. The radiation is only marked externally by the groove of the feet( 1 ). (1) .!bteri~di8coidea, Lam., Encyc. M6tbod., Vers, XCVII, XCVlll;-.ds. ttJ8elata, var., A, Lam.; Link., XIII, 22; Encyc., XCVI. |
