OCR Text |
Show 446 ARTICULATA. CLASS I. ANNELIDES(l ). The Annelides are the only invertebrate animals tha: have red blood. It circulates in a double system of complicated vessels(2). . . , Their nervous system consists m a double knotted c01d, like that of insects. Their body is soft, more or less elongated, and divided into a, frequently, considerable number of segments, or at least of transverse plicre. . . They nearly all inhabit the water-the Lumbr1c1 or Earth-worms excepted; several penetrate into holes at the bottom, or construct tubes there with the ooze or other matters, .or even exude a calcareous substance, which envelopes them WJth a sort of tubular shell. Division of the .llnnelid~s into three Orders. This class, which contains but few species, presents a suffi· cient basis of division in its organs of respiration. ( 1) I established this class, distinguishing it by the colour of its blood and other attributes in a Memoir read before the Institute in 1802. See Bullet. des Sc., Mesidor ~n X: where I described the organs of the circulation. . d M. La'm arck' has adopted and named ·1 t .!l.nne zt· a es. B rugu· ~: res previously umte f d b I! h' L' us placed part 0 it to the order of the intestinal worms, an e1ore tm, mn.e. . these animals among the Mollusca, and the rest among the Intestlm. 1 think 1 (2) It has been asserted that the blood of the Aphrodit.e is not red. have observed the contrary in the .!l.phrodita squamata. ANNELIDES. 447 The branchire of some resemble tufts or arbusculre, attached to the head or anterior part of the body: they, nearly all, inhabit tubes. We will call them the TuniCOLJE. Those of others resemble trees, tufts, laminre or tubercles in which vessels ramify, and are placed on the middle of the body: most of them inhabit mud or swim in the ocean, the smaller portion being furnished with tubes. We name them the DoRSIBRANCHIA T JE. Others again have no apparent branchife, and respire, either by the surface of the skin, or as some authors opine, by the internal cavities. Most of them live free in mud or water; some of them only, in humid earth. They are the AnRANCHIATJE. The genera of the first two orders are all furnished with stiff setre, of a metallic colour, that issue from their sides, sometimes simply, and at others in fasciculi, which serve in lieu of feet; but there are some genera in the third order which are deprived of that support( I). The special attention paid by M. Savigny to these feet or organs of locomotion, has resulted in the distinction of the following parts : 1. The foot itself, or the tubercle which supports the setre; sometimes there is but one to each ring, and at others there are two, one above the other, styled a simple or double oar. 2. The setre, which compose a fasciculus for each oar, and which vary greatly in form and consistence, sometimes constituting true spines, and at others fine and :flexible hairs, frequently dentated, barbed, &c.(2) 3. The cirri or :fleshy filaments adhering to the foot, either above or beneath. The head of the Annelides of the two first orders is gene- (1) ~1. Savigny has ptopos.ed a division of the Annelides, to be founded on the presence or absence of these locomotory set~; those in which they are wanting being reduced to Leeches. M. de Blainville, who 11as adopted this idea, forms his class of the ENToxozo.&RI.lE CHETOPODES with the Annelides with set~, and that of the ENTOMOZOARI.lE APonEs with those which have none, but in mixing many of the Intestini with the Apodes, he has done \Vhat M. S. did not do. (2) See on this subject the Mem. of M. Savigny on the invertebrate animals, and those of Messrs Audouin and M. Edwards on the .!lnnelide.J. |