372 LUMBRICONEREIS FRAGILIS. 



Claparede and Mecznikow (1863) gave the early stages of the development of a species 

 of Lumbriconereis which they found at Naples in November and December, and though 

 the precise relations of the form are unknown, it may be mentioned that the youngest 

 stage is a rounded trochophore having two reddish eyes with lenses, a central digestive 

 region, a long anterior whip of cilia, and a broad ciliated ring behind the eyes, as Avell as 

 a posterior tuft. The following day the shape is more elongate (pear-shaped). On the 

 fourth day the long anterior whip has disappeared, but the broad zone behind is in full 

 development, as also is the posterior cincture. The digestive tract shows an anterior 

 (pharyngeal) and a posterior region, whilst a pair of bristle-bundles appears in front of the 

 anal ring. Two bristle-tufts occur on the eleventh day, and the anal ring of cilia has 

 disappeared. The prostomial region is larger. At a later date the young annelid shows 

 two well-marked setigerous segments, a conical prostomium with a lateral eye-speck on each 

 side, the pharynx is sunk in the digestive tract, and two short anal cirri occur posteriorly. 

 The outline is elongate ovoid. The authors were uncertain whether the form belonged to 

 Eunice, Lumbriconereis, or Notoeirrm. The figures of the bristles are so small that little 

 help is obtained from them. 



1. LuMBiucoNEREis EiiAGiLis, 0. F. Milller, 1788. Plate LXII, figs. 1 and la — teeth; 

 Plate LXXIII, figs. 8-8 c— feet ; Plate LXXXII, figs. 2-2 b— bristles. 



Specific Characters. — Head conical and smooth, with a dimple posteriorly leading 

 into two nuchal pits with papillae. Body 5 — 10 or more inches in length, ending in four 

 caudal cirri. First segment longer than the second. Colour iridescent brownish. 

 Mouth opens behind two massive lips separated by a median fissure, with a curved and 

 crenate hind lip. Maxillae boldly curved, continued posteriorly into two spear-shaped 

 processes. Great dental plates with four teeth (five to six, Ehlers). Inner lateral plate 

 has a horny tooth internally, and so with the outer. Horny patch behind these fits against 

 the tooth, and externally a horny bar passes towards the maxilla. Mandibles anchylosed, 

 with dense whitish calcareous edges. Body- wall (Fig. 77) massively muscular, the 

 great thickness of the ventral longitudinal muscles being conspicuous. Foot with simple 

 winged bristles as far as the twenty-first, when winged hooks appear. Anterior lobe 

 bluntly rounded, the posterior with a nearly horizontal dorsal edge, a bluntly conical 

 point, and then, after fusing with the lower edge of the anterior lobe, sloping inward and 

 backward to the body. The space between the lobes greater in the anterior foot. Feet 

 increase in length posteriorly, and the hind lobe becomes pointed. Hook with a shaft 

 like that of the bristles, but after the curve and expansion it contracts to a neck. The 

 terminal hook has a serrated crown and is guarded by a wing on each side. Spines four 

 in number, black. The tapering winged bristles disappear before the sixtieth foot, the 

 posterior feet having only the winged hooks and two black spines. 



