228 THE VOYAGE OF H.M.S. CHALLENGER. 



and the peculiar structure of the siphosome destroyed before I could begin its closer 

 anatomical examination. 



Bracts (fig. 8, b ; figs. 10 and 11, dorsal view; figs. 12 and 13, profile view). — The 

 covering scales which compose the firm carapace of the globular siphosome are very thick 

 and hard wedges of cartilaginous consistence. Their thickness increases from the proximal 

 pedicle towards the middle part and decreases again towards the distal part, which is 

 usually trilobed or five-lobed. The form of the larger bracts is rather regular and sym- 

 metrical ; there are, however, intermingled, mainly in the proximal part of the siphosome, 

 numerous smaller bracts which have a more irregular form, and partly fill up the void 

 intervals between the former. The majority of bracts were detached from the stem 

 before I could examine their peculiar arrangement. Their lower or inner face is concave ; 

 and near to it runs in the median line the blind bracteal canal (figs. 10— 13, be); the 

 upper or outer face is convex and usually provided with three or five prominent ribs ; 

 each rib is three-sided, prismatic, and bears on its prominent abaxial edge a series of 

 large cnidocysts. 



Siphons (fig. 8, s). — The feeding polypites, which proceed through the basal ostium of 

 the hydrcecial cavity just described, are of medium size, and of the form usual in Agal- 

 midae. Their pedicle is long and slender, the basigaster small and ovate, the stomach 

 fusiform and provided with four double rows of red-brown liver glands ; the proboscis is 

 slender, very protractile, and ends in a mouth, which may be expanded in the form of a 

 circular or polygonal suctorial disc. 



Tentacles (figs. 8, 14). — The long tentacle which is attached to the base of each 

 siphon bears a series of very numerous tentilla. Each tentillum (fig. 14) is composed 

 of a slender pedicle (tp) and a campanulate involucre (th) which encloses a purple 

 spiral cnidoband (tk) ; this exhibits seven or eight spiral turnings, and bears at its distal 

 end three appendages, a large spindle-shaped terminal ampulla {to), and a pair of slender 

 lateral horns (tc). 



Patyons and Papacies (fig. 8, q, r). — The tasters are very numerous and seem to be 

 irregularly scattered over the entire stem of the siphosome, partly between the siphons 

 and bracts, partly connected with the gonostyles. They are very slender pellucid tubes, 

 cylindrical or spindle-shaped, closed at the apex, which includes a number of cnidocysts. 

 From their tapering base arises usually (or always ?) a long palpacle, a very thin and 

 mobile tasting filament, of the usual shape. The palpons as well as their palpacles are 

 stretched and protruded through the intervals of the bracts as well as through the basal 

 opening of the hydrcecial cavity. 



Gonodendra. — A small number of sexual clusters is attached to the trunk of the 

 siphosome, mainly (or exclusively) to its upper or proximal half(?). The corm is 

 monoecious, but the cormidia distylic, since each cluster contains gonophores of one sex 

 only. The umbrella is well developed in the gonophores of both sexes, campanulate in 



