209 



ANNELIDA. 



ANNELIDA. 



Home, ' Leet. on Comp. Anat.' ii. pi. 1. Upon this spiral rolling up 

 of the branchiae Savigny established his subdivision of Cymospin 

 Serpula, from which II. de Blamville afterwards established a genus. 



The genus Spirorbis, Lam., consists of those Serpulw whose branchial 

 filaments are much less numerous, only three or four on each side ; 

 their tube is rolled up into a tolerably regular spiral, and they are 

 ordinarily xery small. 



Sabella. The species of this genus have the same body and the 

 same fan-shaped branchial as the Serpidie ; but their two fleshy 

 filaments adhering to the branchiae each terminate in a point, and do 

 not form an operculum ; they are even sometimes absent. The tube 

 of the Sdbellce appears, most frequently, to be composed of grains of 

 sand, of clay, or very fine mud, and is rarely calcareous. The known 

 species are rather large, and Cuvier notices their branchial plumes as 

 being of admirable delicacy and brilliancy. 



Example, Sabella protula, Guv. (Protula Rudolphii, Risso).' This 

 beautiful and large species, with a calcareous tube like that of the 

 Serpultp, has the branchiae of a rich orange. 



Terebella. The species like the greater part of the Sabellre, inhabit 

 a factitious tube ; but it is composed of grama of sand and fragments 

 of shells ; their body, moreover, has much fewer rings, and their head 

 is differently ornamented. Numerous filiform tentacles, susceptible 

 of much extension, surround their mouth, and on their neck are 

 arborescent branchiae, not fan-shaped. 



Example, Terebella conchilega. 



Ai/iji/iitrite. Cuvier remarks that the species of this genus are 

 easily known by straw-like processes ranged in a pectinated form, or 

 in that of a crown, in one or more rows, where they probably serve 

 for defence, or perhaps as means of creeping or collecting the materials 

 for their tube. Around the mouth are very numerous tentacles, and 

 on the commencement of the back on each side are branchiae in the 

 form of a comb. 



Cuvier's genus A mphitrite comprehends the Pectinaria of Lamarck, 

 the Ampkictdncs of Savigny, the Ckrysodons of Oken, the Oistencs of 

 Leach, the Sabettaria: of Lamarck, the UermeUet of Savigny, and the 

 genus Pkerusa of De Blainville. 



^i/:/t/jtoma (Otto). The species of this genus, which Cuvier suspects 

 should be referred to this order, have on each articulation above a 

 bundle of fine bristles ; below, a simple bristle ; and, at the anterior 

 extremity, two packets of strong and golden-coloured bristles. Under 

 these bristles is the mouth, preceded by a sucker surrounded by many 

 soft filaments, which Cuvier thinks may be branchiae, and accompanied 

 by two fleshy tentacles. The knotted medullary cord may be seen 

 through the skin of the belly. The Siphoitomata live burrowed in 

 the sand. 



Examples, Siphnstoma diplorhaitos, Okenj 5. uncinata Aud. et 

 Edw. ' Littoral de France, Annel.' pi. ix., f. 1. 



The close connection between the Ttibicvlte and the Dorsibranchiatce 

 18 seen in the fact that the young of these orders pass through 

 precisely the same stage before arriving at maturity. It is only during 

 the last stages of change that the embryoes of Tubicolte manifest their 

 ultimate destination by the unequal development of certain of their 

 segments, some of which become almost abortive, whilst others are 

 disproportionately developed. 



The Terricolce have a cylindrical body tapering at both ends. The 

 segments of their bodies are not well marked, and the head is not 

 distinct from the trunk. They have neither eyes, mandibles, cirrhi, 

 nor tuberculous feet. This order includes two principal groups, one 

 of which only is terrestrial, whilst the other is aquatic. To the 

 former belong the Common Earth- Worm (]." n> ///('.* tomfriv), whilst in 

 the latter is included the Lob or Lug-Worm (Arenicola). As the 

 Earth-Worm is so well-known, we shall refer to its structure and 

 habits to illustrate the order. 



Cuvibr remarks that the Lumbrici ought to be subdivided; and 

 Savigny has, in effect, subdivided the Earth-Worms into the genera 

 Enteritm, Jfypogarun, and C'lUdlia. Messrs. Audouin and Mime-Edwards 

 distinguish also the genus Trophonia. 



Of these Enterion has upon each ring four pairs of small bristle-like 

 processes, eight in all 



Clilellio is stated to have two bristle-like processes only on each ring. 



II '//"/"'< has, besides the other bristle-like processes, one on the 

 back of each ring. (This form is noticed as being American only.) 



r/tonia has on each ring four bandies of short bristle-like 

 processes, and at the anterior extremity a great number of long and 

 brilliant bristle-like processes which surround the mouth. 



Savigny described upwards of twenty species, which he considers 

 to be distinct, and to have been confounded previously under the 

 name of Lumhrictu terrettra. M. Morren, in his ' Treatise on the 

 Natural History and Anatomy of the Lu.mbric.ut terrettris,' appears to 

 be doubtful with regard to the number of species described by 

 Savigny and others, and inclines to the opinion that they are merely 

 varieties. M. Milne-Edwards (edit, of Lamarck's 'Animaux sans 

 Vertebras,' 1838,) considers the characters on which Savigny relied as 

 distinctions for dividing the group into the three genera as of little 

 importance. 



Externally the Earth-Worm (Lum ' .'n', Linnaeus) presents 



a IMJV composed of numerous narrow rings rlosrly Approximated to 



<f ln-i- ; ;it, iiliout one third of their length may be seen, particularly 



MAT. HIST. HIV. VOL. I. 



at the season of reproduction the clitellum, which becomes at that 

 time a liighly important agent. The colour of the body is reddish or 

 bluish, and of a shining aspect, and the animal has the power of 

 secreting a viscous substance, which forms a sort of protecting sheath 

 to its body, and greatly facilitates its progress throxigh the earth. 

 The animal is eyeless, and unprovided with either tentacle, branchiae, 

 or cirrhi. 



Respiratory System. The generally received opinion is that the 

 blood of the Earth-Worm is aerated by means of lateral series of 

 small pyriform vesicles, analogous to the breathing sacs of the Leech, 

 and opening externally by very minute pores. 



Disgestire System. The mouth consists of two lips without tentacles 

 or armature of any description ; but the upper lip is elongated and 

 proboscidiform. The oesophagus, which is a wide membranous canal, 

 is continued straight down for half an inch, and ends in a dilated bag 

 or reservoir, to which succeeds a muscular stomach or gizzard, disposed 

 in the form of a ring. The intestine is constricted at each segment of 

 the animal by a series of ligaments or partitions, connecting it to the 

 parietes of the body, and swells out the intermediate spaces, when 

 distended by the particles of earth. 



Nervous System. The nervous system of the Earth-Worm consists 

 of a double row of small ganglions close to each other. 



Generative System. Allotriandrous, or with male organs so disposed as 

 to fecundate the ova of a different individual. (Owen.) It has been 

 doubted whether these animals are oviparous, ovoviviparous, or vivipa- 

 rous. The fact is, that after fecundation by another individual, the ova, 

 which are contained in the ovary, are set free in the cavity of the 

 body by the bursting of the ovary, and are gradually propelled to a 

 cavity near the anus. In this spot they undergo the usual changes, 

 and they may or may not emerge from the parent before the egg- 

 membrane is broken. 



Organs of Progression. Earth -Worms creep at a good pace by means 

 of muscular contraction and dilatation acting on the rings, which carry 

 on their under-side the bristle-like processes above mentioned : these 

 last operate as feet. The power of elongation is considerable, and the 

 anterior part of the animal acts as a sort of awl in peueti'ating the 

 earth. 



Habits, ttc. The Earth- Worm, as far as relates to its appearance 

 above the surface of the ground, may be considered almost a nocturnal 

 animal. In the night-season and at early morning hundreds may be 

 seen, though not one, unless they are disturbed either by moving the 

 ground or pouring liquids into their holes, is to be found moving about 

 in the day. The power of reproducing parts after mutilation is very 

 great in this animal and the whole of the order. 



Utility to Man. The worm-casts, which so much annoy the gardener 

 by deforming his smooth-shaven lawns, are of no small importance to 

 the agriculturist ; and this despised creature is not only of great 

 service hi loosening the earth and rendering it permeable by air and 

 water, but is also a most active and powerful agent in adding to the 

 depth of the soil, and hi covering comparatively barren tracts with a 

 superficial layer of vegetable mould. In a paper ' On the Formation 

 of Mould," read before the Geological Society of London, by Charles 

 Darwin, Esq., F.G.S., the author commenced by remarking on two of 

 the most striking characters by which the superficial layer of earth, 

 or, as it is commonly called, vegetable mould, is distinguished. These 

 are, its nearly homogeneous nature, although overlying different kinds 

 of subsoil, and the uniform fineness of its particles. The latter fact 

 may be well observed in any gravelly country, where, although in a 

 ploughed field, a large proportion of the soil consists of small stones, 

 yet in old pasture-land not a single pebble will be found within some 

 inches of the surface. The author's attention was called to this subject 

 by Mr. Wedgwood, of Maer Hall, in Staffordshire, who showed him 

 several fields, some of which, a few years before, had been covered with 

 lime, and others with burnt marl and cinders. These substances, in 

 every case, are now buried to the depth of some inches beneath the 

 turf. Three fields were examined with care : the first consisted of 

 good pasture-land, which had been limed, without having been ploughed, 

 about 124 years before ; the turf was about half an inch thick ; and 

 24 inches beneath it was a layer or row of small aggregated lumps of 

 the lime, forming, at an equal depth, a well-marked white line. The 

 soil beneath this was of a gravelly nature, and differed very consider- 

 ably from the mould nearer the surface. About three years since 

 cinders were likewise spread on this field : these are now buried at the 

 depth of an inch, forming a line of black spots parallel to and above 

 the white layer of lime. Some other cinders, which had been scattered 

 in another part of the same field, were either still lying on the surface 

 or entangled in the roots of the grass. The second field examined was 

 remarkable only from the cinders being now buried in a layer, nearly 

 an inch thick, 3 inches beneath the surface. This layer was in parts 

 so continuous, that the superficial mould was only attached to the 

 subsoil of red clay by the longer roots of the grass. 



The history of the third field is more complete. Previously to 

 1 5 years since it was waste land ; but at that time it was drained, 

 harrowed, ploughed, and well covered with burnt marl and cinders. 

 It has not since been disturbed, and now supports a tolerably good 

 pasture. The section here was turf half an inch, mould 24 inches, a 

 layer 1 J inch thick, composed of fragments of burnt marl (conspicuous 

 from their bright red colour, and some of considerable size, namely, 



