LTJMBBICONEREIS FRAGILIS. 375 



change being the somewhat different arrangement of the bristles, which often form 

 groups of two and three. 



The twenty-first foot usually shows the first long winged hook. This has a shaft 

 similar to that of the bristles, but after the bend and expansion, it narrows to a neck, 

 with a terminal hook having a serrated crown. A narrow wing on each side guards the 

 hook and stretches from the dilatation to the tip. This hook appears below the spines, 

 which are four in number. The spines at the thirtieth foot are three in number, but the 

 structure of the foot is little altered except by the presence of the long winged hooks. 



At the fiftieth foot or thereabouts (Plate LXXIII, fig. 8 b), only a single bristle is 

 present, or occasionally two of the tapering winged type (Plate LXXXII, fig. 2) remain, 

 whilst the strong winged hooks are prominent. These (Plate LXXXII, fig. 2 a) have a 

 considerably stouter shaft than the bristle of the same foot, and the shaft is curved distally, 

 the winged region being comparatively short and obliquely striated with fine lines. A 

 constriction forming a neck occurs below the terminal hook which has a crown of minute 

 serrations, directed obliquely forward to the hook. The developing hook has a long 

 filiform cap or process distally (Plate LXXXII, fig. 2 b) — apparently a translucent exten- 

 sion of the wing. When seen antero-posteriorly, the double wing is observed to curve 

 inward at the tip on each side and to be attached to the central stem of the hook. Two 

 black spines occur in these and the succeeding feet. 



The tapering winged bristles disappear before the sixtieth foot, so that the posterior 

 feet only have the long winged hooks with the comparatively short wing and the two 

 black spines supporting the foot (Plate LXXIII, fig. 8 c). 



In looking at the feet from above in spirit-preparations a tendency to a " probe-point " 

 at the tip of the posterior lobe is apparent, especially anteriorly. A blood-vessel passes 

 round the posterior lobe of the foot, a little within the margin. 



Habits. — An active form. It frequently twists itself into a knot, and occasionally 

 is preserved in this condition. 



In a variety from Grodhavn Harbour, Greenland, dredged by the ' Valorous,' the tips 

 of the long bristles are remarkably attenuated and have a double curve. Moreover, the 

 posterior lobe of the foot anteriorly is less attenuate, that is, has a broader cone in lateral 

 view. By-and-by, as at the fifty-seventh foot, the attenuation of the long bristles becomes 

 extreme, the tip forming a long, delicate, hair-like process, and the wings are very narrow. 

 The shafts are brownish. The winged hooks have blackish-brown and very long shafts, 

 with a short dilated terminal region and a narrow wing. Both lobes of the feet posteriorly 

 form narrow cones. Whether this is a marked variety remains to be seen. The spines 

 are similar to those of L. fragilis. 



Langerhans l describes L. fragilis from Madeira, but his figures of the hooks give 

 rise to some doubt as to the species referred to by him. 



Two species described in the 'Challenger' volume 2 from the Amierican coast, viz., 

 Lumbriconereis punctata and L. Ehlersii var. tenuisetis, approach this form in many 

 respects. 



A form (B) procured in Herm in 1868 is distinguished from the ordinary Lumbrico- 



1 'Zeitschr. f. wiss. Zool./ Bd. xxxiii, 1879, p. 297, fig. 30. 

 3 Pp. 252 and 253, etc. 



