CH^TOPTERUS VARIOPEDATUS. 125 



whilst the posterior part is devoid of them, and is probably therefore the more mobile. 

 When the superficial tissues are removed this posterior region of the wing presents a 

 tapering hollow tube which is elastic and glistening like a thin sheet of cartilage, but 

 it is really composed of a highly elastic fibrous sheath, and probably has a fluid driven 

 into it internally. The bristles supporting the web in front are of the type characteristic 

 of the posterior region, viz., long, straight bristles tapering at both ends and fixed 

 throughout to the muscular web. The base of these great wings is crowded with 

 glands for the secretion of- the abundant mucus. Their dorsal surface is grooved and 

 ciliated, food being thus carried forward by the median ciliated band to the funnel-like 

 mouth. 



The ventral division of this foot has united with its fellow of the opposite side to 

 form a transversely elongated disc like a sucker with the hooks on the frill-like edge. 

 In some there are indications of a median separation, but in others only a slight indenta- 

 tion of the outline occurs — the row of hooks being continuous, and they do not differ 

 essentially from those of the ninth foot, but many show the small ninth tooth, and a 

 small process for the attachment of the ligament projects at the opposite side. 



The next segment resembles a portion of gut with a soft transversely reticulated 

 wall having the raised median band continuous with the grooved one in the previous 

 segment, and with deep folds like those in the colon. The dorsal median band continues 

 backward to a curiously frilled whitish or yellowish structure which separates the segment 

 into two moieties, and which forms two flaps in front with a central circular opening and 

 a projecting pouch posteriorly containing sand-grains and muddy matter — apparently 

 contents of the gut with sponge-spicules, bristles, and fragments of shells. "Whether this 

 acts as an escape-valve, accidental or otherwise, cannot be ascertained from the prepara- 

 tions, but appearances suggest such a view. The two firm, whitish dorsal flaps of the 

 organ open forward, and have within them a second yellowish fold on each side, within 

 or behind which again is an opening of considerable size, bounded inferiorly by a tense 

 band. The raised dorsal median band passes to the base of this tense band where a 

 slight fillet occurs and then ceases. The moiety of this segment behind the folded 

 organ resembles that in front of it, minus the median dorsal band, and dipping down 

 behind becomes continuous with the third segment of the region. Ventrally two 

 great muscular masses with a deep median groove give firmness to the region and 

 support the muscular ventral disc bearing the hooks, the form of the disc resembling 

 that in front. 



The three following segments resemble each other in so far as each is somewhat urn- 

 shaped, narrow posteriorly and rising anteriorly and dorsally into a great fan-shaped 

 surface, the edge of which forms a broad frill or collar. The anterior surface is firm 

 and muscular, whilst the posterior shows the gut through its thinner walls. The broad 

 collar is continued in each ventrally so that it is complete. From the mid- ventral edge 

 of the collar is given off the nearly quadrangular disc for the hooks which are borne on 

 the free flap posteriorly. A trace of a median division is present. The next segment 

 bears a broader disc more distinctly bilobate, and so is the disc on the last segment of 

 the region. In short, each of the two just mentioned clearly foreshadows the two free 

 pads for hooks in the succeeding segments. The hooks of the last segment of the region 



