88 ANNELIDES. 



them lose with impunity their exterior organs, and even considerable 

 portions of the body, reproducing the lost parts in a short time 

 under favouring circumstances. The anterior half will reproduce the 

 posterior, and that will return the favour by restoring the anterior 

 with the head and all its organs. But if the body is cut into several 

 pieces, it has not been proved that the separated pieces can live, and 

 become each a perfect worm. 



In general the Annelides rapacia have a serpentine or myriapod 

 form, but some are oblong or oval. The body is almost always ter- 

 minated anteriorly by a distinctly defined head furnished, with few 

 exceptions, with eyes, and with antennae, — a collocation of parts 

 which is not met with in any other order of the class. Underneath 

 the head, and at its junction with the first ring of the body, we find 

 the mouth (No. X. fig. 7a), which is, in some cases, prolonged back- 

 wards and buttressed by the feet. The proboscis is composed of one 

 or two rings ; it is very often armed with jaws, and not unfrequently 

 the orifice is encircled with papillary filaments (No. VII. fig. 2). 



There is a series of feet along each side of the body, having the 

 form of fleshy tubercles, more or less protuberant. These organs 

 are sometimes simple or uniramous, — sometimes bifid, with a dorsal 

 and a ventral branch. The apex of the branch is always the outlet 

 of a brush of bristles, which can be thrust out, and again withdrawn, 

 to a certain extent at least, into the ring, by certain muscles appro- 

 priated to that use. These bristles are sharp, rather firm organs, 

 very variable in regard of figure and conformation in different genera , 

 and each brush has a spine in its centre. In only a very few of this 

 Order do hooked bristles occur, and when present they make a part 

 of the ventral branch of all the feet ; while in the Tubicolse this uni- 

 formity of structure is not observable, — nor in the Tubicolse is their 

 presence coincident with the existence of cirri. 



The soft appendages of the Annelides rapacia are, in general, 

 numerous and well developed. The cirri are the most constantly pre- 

 sent, disappearing indeed only in a small number of genera placed 

 upon the limits of the Order ; but among the Tubicolse the Hermellae 

 alone have them. Their usual form is that of a filament tapered 

 gently to a point, and more or less contractile ; but in some species 

 the cirri are compressed and expanded into leaflets or miniature fins. 

 With few exceptions there are two cirri to each foot (No. VIII. 

 figs. 3, 4, 5). 



The appendages which have received the name of Branchiae are 

 often absent. In some genera they appear under the guise of mere 

 tubercles or fleshy papillae, attached either at the summit or near the 

 base of the foot ; in others they are pectinated filaments ; and in 

 others much-divided arbuscular tufts of a crimson colour. The 

 scales, which cover the back like a series of tiles, are peculiar to a 

 few genera of this Order. 



These soft appendages are repeated in nearly unvaried uniformity 

 along each side of the body, so that every segment is the same in its 

 gear ; but in some species the superior cirri, the scales, or the bran- 

 chial tubercles, appear and disappear alternately from ring to ring. 



