NEREIS DUMBEILTI. 307 



out by Claparede, are diagnostic. In many the anterior region of the body has the 

 segment-junctions transverse, whilst those behind slant from the middle line outward and 

 backward, a feature observed in the heteronereid of iV. pelqgica. This, however, is not 

 seen in those from which the genital products have escaped, and the bodies of which are 

 semi-transparent. 



The dorsal cirrus of the first foot is considerably dilated (Plate LXXII, fig. -id) so 

 that its dorsal outline forms a semicircle. The ventral cirrus is also similarly enlarged. 

 Three elongated lobes appear in lateral view. The second foot is similar. The third 

 has a tendency to an angular condition near the tip of the dorsal cirrus, from the abrupt 

 cessation of the enlargement. In this foot, as usual, the two setigerous processes occur. 

 The peculiar knobbed condition of the dorsal cirrus is more marked in the fourth foot 

 and attains its maximum in the fifth and sixth (Plate LXXII, fig. 4e). In the seventh 

 the cirrus, though longer, is more slender, and shows the angular process at the tip. The 

 eighth on the right has a slender cirrus with the tip bent at an angle, whilst its fellow of 

 the opposite side is normal, and so with the others which follow. The bristles are normal. 



At the compressed sixteenth foot a decided change has taken place. An ovate 

 lamella arises internal to the base of the dorsal cirrus, which is long and furnished with 

 eight papillae on its ventral border, the tip tapering from the last, which is longest. The 

 dorsal lamella is long and lanceolate. The superior setigerous process ends in a blunt 

 point, and some of the old bristles are present, the rest being swimming bristles. The 

 lobe beneath it is lanceolate with a rounded spur at its base interiorly. The inferior 

 setigerous process is bifid, with an ovato-lanceolate lamella superiorly. Some of the old 

 bristles remain in the superior tuft (homo- and heterogomph) ; the rest are swimming 

 bristles. The ventral lobe is tongue-shaped. The ventral cirrus has an ovate lamella 

 internally, and a small elongated one externally. 



The pelagic foot is seen in full development at the thirty-seventh in those 

 captured near the surface, as at Castlebay, Bona, on the 22nd May. The lobes of the 

 feet are very thin and the sides glisten with the sheen of the large and long swimming 

 bristles. Dorsally (Plate LXXII, fig. 4f) is the fan-shaped lamella close to the inner 

 edge of the dorsal cirrus. The dorsal cirrus itself is long, with the papillae (eight to ten) 

 on the lower border, and distally the filiform tip. The dorsal lamella is lanceolate. The 

 upper setigerous lobe is bifid and bluntly conical, the transparent bristles projecting from 

 it in two groups. The lamella soldered to it inferiorly is broadly lanceolate with a heel 

 at its inner and inferior border. The long inferior setigerous lobe has a huge lamella on 

 its posterior face, stretching almost to the tips of the bristles, which project like a great 

 fan. A long heel likewise extends inward from its base superiorly. The tongue-shaped 

 ventral lamella leaves the stem of the former lobe and turns outward as a process with 

 a spur on its upper border near the base. The ventral cirrus projects from a large fan- 

 like lamella internally and a tongue- shaped one, with an upper heel, externally. 



All the foliaceous lamellae are finely and somewhat regularly veined from a midrib 

 or a basal region. The venation appears to be due to granular canals (?) of the hypoderm. 

 Many terminate between the pale end-organs at the margin of the lamella. 



Little change occurs in the structure of the foot till near the tip of the tail, where 

 the diminution in the size of the foot is marked. All the lamellae become less ; the dorsal 



