and two or more kinds are often found coexistent on the same foot. The forms may, perhaps, be reduced to the following : Capillary-Slender, flexile and hair-like, as e. g. the coloured hairs of Aphrodita aculeata. Setaceous, slender and tapered insensibly from the root to a sharp point (Pl. III. figs. 6, 7). Lanceolate, straight on the lower half, bulged about the middle, whence it tapers to a point sharp on both sides (figs. 10, 11, 13, 14). Ventricose. When the shaft is enlarged on one side (figs. 8, 9). Tarsiform.-A stout bristle terminating in a point curved and sharp like a claw (figs. 17, 18, 19). This is common in the Aphroditaceæ. It is somewhat grooved and denticulate on one side. Spinous. A stout bristle resembling the spine or spinet, but distinguished by being fasciculate (figs. 21, 22). It is more or less flexuose or bent like the letter / (fig. 23) in many subcephalous annelids; and is dark-coloured and straight in Aphrodita aculeata. The compound Bristle is peculiar to the "Annelida rapacia." It is a bristle of which the shaft is broken into two halves by an imperfect sort of joint. The lower portion is the shaft, and the upper the terminal piece. (See Pl. IV.) The intermediate joint may be simply oblique with the edges approximate (Pl. IV. fig. 1), or separate (figs. 4, 5), or with the shaft and terminal piece attached merely by a point (fig. 11). Or the two pieces may be connected by a mortise joint (fig. 7), or by a variously formed socket (figs. 2, 9, 13). The shaft is usually straight, smooth or serrulate, and a little enlarged towards the outer end. The terminal piece varies in shape like the simple bristle. It is acicular when it is straight and slender, and tapers to a very sharp point (Pl. IV. fig. 7). Tarsiform. When it is elongated and slightly bent, and brought to a point, like the hind claw of a small bird (Pl. IV. fig. 1). Falcate.-When the piece is short, and curved at the apex so as to resemble the mandible of a small bird (Pl. IV. figs. 2, 6, 12). : The British species are divided into the following Tribes : Tribe I. RAPACIA. Animal-killers. Body with soft appendages, generally disposed on the whole length of the body. Feet distinct, armed with setæ, which are sometimes hooked. Head generally distinct, provided with eyes, antennæ, a retractile proboscis, and often with jaws. marine animals. Tribe II. LIMIVORA. Mud-eaters. Living on Body with the soft appendages collected together at the cephalic extremity. Feet of two kinds, generally deprived of cirrhi, and armed with hooked bristles. Head not distinct, without eye-tentacles. Protractile proboscis or jaws. Eating mud and the dead animals and vesicles it contains. 81 VI. ANNELIDES. I. RAPACIA. SCOLOPENDREÆ MARINE, Jonst. de Insect. lib. iv. 205. ANNELEIDES, Leach in Ann. Phil. xiv. 205 (1819). ANNELIDES ANTENNÉES, Lam. Anim. s. Vert. v. 302. NOTOBRANCHIA, Latreille, Fam. Nat. 238. NEREIDINA, Macleay in Murchison's Silur. Syst. ii. 699; and in Ann. ANN. ERRANTES, Aud. & M.-Edw. Litt. de la France, ii. 27. DORSIBRANCHIATA, Griffith's Cuv. Syst. Ind. lix. Jones, Anim. ANNÉLIDES ERRANS OU DORSIBRANCHES, M.-Edwards, Elem. de ANNELIDA ERRANTIA, Ann. & Mag. Nat. Hist. xiv. 32. ANNELIDES NEREIDEE, Savigny, Syst. Annel. 7. MARICOLE, Oersted, Ann. Dan. Consp. 2. RAPACIA, Grube, Fam. Annel. 30. Char. "Body with soft appendages (cirri, branchiæ or antennæ), generally disposed over the whole length of the animal, and not collected towards the cephalic extremity. Feet generally very distinct, armed with setæ or bristles, which have very rarely the form of hooks. Head generally distinct, and provided with eyes, antennæ, and a retractile proboscis, often with jaws.”—MilneEdwards. Obs. Organized for locomotion, this tribe of Annelides—the tyrants or the aristocracy of their race-wander abroad, and are in constant warfare with all around them. They crawl on the surface at a pace that varies in the species from extreme slowness to energetic activity. Many of them swim with ease; and others burrow in the wet sand of the shore. A few construct tubes or cases for their residence, but these are not essential to the existence of the tenant, and can be vacated at pleasure. They are eminently carnivorous, with the exception, perhaps, of the Ariciada, which may be geodephagous or feeders on putrescent matter. The sexes are separate so far as is known; and the female is oviparous. The young undergo a certain metamorphosis which tends to higher development of the organs. G Lost portions are restored with facility. A few secrete a luminous fluid, but an organ appropriated to the secretion has not been demonstrated. The skin is very generally margaritaceous or iridescent; and this is occasionally the case also with the bristles. 1. General Form.-The Annelides have an elongated worm-like figure, which, in some genera, inclines more or less to an oblong or No. VI. oval. The Nereides offer examples of the vermiform species (No.VI.); the Polynoë, and, more especially, the Aphrodites, may be instanced as examples of the latter. The length is often considerable. On our shores species are to be found nearly two feet in length, and as thick as the barrel of a large quill; but in equatorial seas some attain the length of five feet with a diameter of thirteen lines. 2. Body. The body is composed of narrow segments or rings (No. VI. fig. d), not calcareous nor even corneous as they are in the great majority of crustacea and insects, but membranous, and merely separated by a fold of still thinner membrane, such as we observe in many larvæ and caterpillars, so that it is occasionally difficult to mark their exact limits. The number of the rings is in general very considerable, and proportionate to the length of the body, for the growth of this in length depends much more on the production of new segments than on the development of any one in particular. There are great differences in the number of rings necessary to complete maturity. In some Polynoë there are not more than from 20 to 30 rings; in Phyllodoce lamellata not less than 500. In the species which have few rings, as in Aphrodite and Polynoë, the number appears to be specifically limited, and the same in all the individuals; but in the Nereides and others nothing is more variable, and less to be relied upon as a discriminative character. This variety depends on age, on circumstances more or less favourable to growth, and on the effects of injuries. 3. Head and Appendages.-The first segment forms a head more or less distinct (No. VII. fig. 1). On the upper or dorsal surface of this head there are usually one or two pairs of black specks, believed to be eyes* (fig. 1, a). The head bears also usually a * Blainville doubted whether they were eyes (Dict. des Sc. Nat. xlvii. p. 210). But Müller believes them to be really visual organs, for they have nerves from the brain, the form of eyes, and are provided with a black pigment. He admits, certain number of conical or filiform appendages, which we distinguish into antennæ, palpi, and tentacula. The antennæ are directly attached to the head, and their insertion is always superior (fig. 1, 0; fig. 2, 6). The palpi are more connected with the mouth, and their insertion is inferior (fig. 1, b b)*. The tentacula (fig. 1, c c) are filiform organs inserted, in pairs, on each side of the head, and of the post-cephalic segment, when this is apodous. 4. Mouth. In the Annelides with a head obscurely defined, as, for example, in the Tubicoles, the mouth is usually terminal; but in all the cephalous genera it is on the ventral or inferior aspect. It is either a simple wide aperture, or it is furnished with a proboscis (fig. 1 and fig. 2, e, e), which can be extruded at the will of the animal, although it is kept retracted and concealed in the state of quiescence. It may be considered as simply a portion or continuation of the alimentary canal. It is often armed with horny jaws however, that they do not contain any transparent parts, and are not furnished with any optical apparatus: they are simple swellings of the optic nerves, surrounded with a black pigment, sensible to light, and enable the worm to distinguish between light and darkness,-between places which lie in shade and those which are exposed to the glare of day; but not imparting the power of recognizing the shape, or colour, or texture of bodies.-Ann. des Sc. Nat. tom. xxii. p. 25. See also in favour of their being eyes, Bourjot in Microsc. Journ. i. p. 77; and Cuvier in Analyse des Travaux de l'Acad. Roy. des Sc. 1828, p. 82, &c.; De Quatrefages in Ann. des Sc. Nat. iv. (1845) p. 178. But M. de Quatrefages has found in some species, especially in Torrea vitrea, eyes that have a crystalline lens, a choroid coat, a vitreous humour, a transparent cornea, &c. "Some Annelida have other eyes besides those on the head. M. Quatrefages believes that he has discovered them upon the branchiæ of the Sabellæ, and he has no doubt that the red points which we find upon the sides of each ring in several Annelida of the genus Nais are true eyes; there is, however, nothing surprising in this, when we recollect the very great independence existing between the various rings of which the body of these animals consists."-Ann. & Mag. Nat. Hist., Ser. 2. vi. p. 228. * Audouin and Milne-Edwards call the central organs median antennæ, and the palpi external antennæ; but our nomenclature does away with the adjective, and the structure of the organs would seem to indicate a difference in their functions. (fig. 1, f) that indicate the power and cruelty of the species. No acephalous Annelid has jaws of such strength; and few have any organs of the kind. The proboscis is occasionally roughened with small horny prickles collected into clusters (fig. 1), or clothed with minute fleshy papillæ; and its orifice is either plain or encircled with tentacles (fig. 2, h). 5. Feet. In the majority of Annelides there is a foot on each side of every ring which is armed with bristles, and provided with certain soft appendages to which the names of cirri, branchiæ, and scales have been applied*. The foot in general is composed of two parts or branches placed one above the other. These branches are sometimes wide asunder, and easily to be distinguished into a dorsal or superior (No. VIII. figs. 3, 4, a), and a ventral or inferior branch (6); but sometimes, on the contrary, they are intimately united, and appear to have coalesced in one (fig. 5). Each branch is provided with a brush of bristles (figs. 3, 4, 5, c), which the animal can protrude considerably from the outer or distal end. The bristles are of two kinds,-the subulate and the hooked. The subulate bristles are distinguished into bristles (festuca) properly so called (figs. 3, 4, 5, c), and into aciculi or spines (d). The former are either grouped in brush-like bundles or arranged in a fan-like series: their shape and structure are very variable. The spines are stouter than the bristles, always straight and needle-like, and deeper coloured. There is only one to each brush of bristles, and it is enveloped in a proper sheath. The hooked bristles (uncinuli, No. X. fig. 9 6) are never met with on the two branches of the same foot: they exist only in the Tubicoles, and their presence is always coincident with a head indistinctly developed or obsolete. They are disposed in one or two series, and occupy the margin of a transverse fold or of a slightly raised mamilla. Their arrangement in a more or less oval ring has given occasion to *On the structure of the foot, see De Quatrefages in Ann. des Sc. Nat. x. (1848) 51. I prefer to call the divisions of the foot branches rather than oars, as Savigny and Blainville call them; for the Annelides "with reptile motion creep," and do not swim except when placed in untoward circumstances. Oersted names the feet "pinnæ," and each has its "pinna superior v. dorsalis," and its "pinna inferior v. ventralis."-Consp. Ann. Dan. p. 5. |