SPIOPHANES. 



181 



setigerous segments. Feet with dorsal and ventral cirri. Dorsal bristles long, slender, 

 and tapering ; ventral bristles abruptly curved backward at the tip. Small winged hooks 

 occur behind the anterior region. 1 



The body- wall in this genus, e.g. in Spiophanes bombyx, is characterised by the 

 delicate nature of the cuticle, which covers a thick layer of soft and easily abraded 

 glandular hypoderm. Beneath the basement-tissue are dorsally circular muscular fibres, 

 but these are few and indistinct ventrally. The chief feature in the genus is the enormous 

 development of the ventral longitudinal muscles, which in section are about ten times as 

 bulky as the small dorsal which are separated in the middle-line by the arch of the 

 alimentary canal, and have a longer gap than their own transverse diameter between 

 them and the ventral which occupy about half the area of the entire body in section 

 (Fig. 118). These great muscles stretch on each side considerably above the feet to the 

 mid- ventral line where they almost touch, the strand from the alimentary canal and its 

 ventral blood-vessel alone separating them. In transverse section the fasciculi form a 



so 



nc. nc. 



Fig. 118. — Transverse section of the anterior region of Spiophanes bombyx, Claparede, in a nearly ripe male. 



thread-like series. In the middle line externally are the proportionally large nerve-trunks, 

 distinctly separated in this region by granular neuroglia, and bounded ventrally by the 

 hypoderm and cuticle. The alimentary canal has externally a very thin coating of coelomic 

 epithelium and circular fibres, and probably a few longitudinal fibres are also present, 

 though they were not clearly differentiated. The mucous lining is thick and often thrown 

 into four folds laterally. The club-shaped granular glands of this coat form a conspicuous 

 feature, and have their broad ends internal. 



Grube 2 (1860) found no eyes in his spirit-preparations, but two tentacular cirri on 

 the buccal segment on the dorsal surface. His species {Spiophanes Kroyeri) is probably 

 closely allied to 8. bombyx, the differences being, perhaps, due to imperfections in 

 descriptions. His example came from Greenland. 



1 Short ventral bristles at the fourteenth to fifteenth setigerous segments ; the anterior ventral 

 bristles disappearing by-and-by. An inferior ventral bristle is largely developed. Chitinoid fibres 

 (filiere) in chambers from the fifth to the fifteenth segments (Mesnil). 



2 f Arch. f. Naturges./ Bd. xxvi, p. 88, Taf. v, fig. 1. 



