31 8 LEIOOHONE BOREALIS. 



region. Then follows a densely papillose belt, the papillse being in rows. The distal 

 part is smooth. 



The first two bristled segments are somewhat long, the succeeding being shorter, the 

 rest a little longer. The eighth is short, and the feet are behind the middle ; then follow 

 eleven segments, of which the first and still more the last are short, the intermediate 

 longer. There are, Arwidsson notes, five bare segments, the last three being very short, 

 whilst the three anterior have rudiments of feet. The part in front of the anal cone is 

 wider, with a prominent rim, from which the cirri project. There are nineteen bristle- 

 bearing segments. 



The longest anal cirrus is mid-ventral, and none occurs in the mid-dorsal line, but 

 on each side is a short pair, then a longer pair, between which and the long median ventral 

 are a shorter pair on each side. There may be from seven to eleven cirri. The anal 

 cone (Plate C, fig. 15 a) is long, and the ventral ridge is distinct. 



The nephridia occur from the sixth to the ninth bristled segments, and their external 

 apertures are behind the hook-rows. 



Integumentary glands are on the cephalic plate, and behind the mouth. The first 

 bristled segment has rows of glands dorsally behind the feet, and they also occur ventrally. 

 The next two have glands anteriorly, whilst the three following are more densely glandular. 

 The seventh has glands anteriorly — chiefly in front of the feet. The eighth has a 

 triangular glandular area ventrally in front, and the succeeding segments have glands 

 dotted along the nerve area — these being especially distinct at the feet, where a ring of 

 glands occurs in each segment. Indeed, glands appear as far as the anal cone. 



The three anterior bristled segments have modified hooks, in which the gular bristles 

 are absent, though the ridge of origin may be present. The bristles (Plate CVIII, figs. 

 5 and 5 a) anteriorly present a distinct wing, and at the second these are accompanied by 

 spinous bristles (Plate CVIII, fig. be). The posterior bristles are slender, winged forms, 

 with long tips, the wings varying in breadth, and these bristles in the terminal segments 

 are stouter. 



The typical hook (Plate CVIII, figs. 5 d and 5 e) has a high crown and about seven 

 teeth above the main fang. 



Arwidsson found females with ripe eggs in May, June, and July. 



Reproduction of lost parts, either anterior or posterior, occurs in this as in other 

 Poly ch sets. 



The tube is friable, apparently free, and is composed of fine sand, a little mud, and 

 secretion. A few minute Foraminifera and sponge-spicules occur amongst the sand. 



Leiochone borealis, var. 



A form procured in the North Sea 1 slightly differs in the structure of the hooks, for 

 only five teeth occur above the main fang (Plate CVIII, fig. 6). The rim of the cephalic 

 plate w T as very faintly marked laterally, and the posterior margin was also shallow. 

 A prolapse of the gut had taken place per amim, but the thread-like cirri occurred on the 



1 I am indebted to the courtesy of Prof. D'Arcy Thompson for an opportunity of making this note 



