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



Hydrcecium (figs. 1, 5, ui, from the right side; fig. 4, from below). The infundi- 

 bulum of the first nectophore, or the hydrceciurn, occupies its middle third, and is larger 

 than both the nectosac (w) at its dorsal, and the somatocyst (cs) at its ventral side. It 

 is slenderly campanulate or conical, in the superior half rather cylindrical, in the inferior 

 much dilated. Its blind apex reaches nearly the frontal crest of the apical face. Its 

 basal opening is isosceles triangular (fig. 4, ui) ; the base of the triangle is formed 

 by the prominent frontal septum, whilst the apex meets with the inferior apex of the 

 triangular ventral face of the nectophore. 



Somatocyst (figs. 1, 5, cs, lateral view; fig. 6, cs, ventral view). — The somatocyst is a 

 very large cylindrical sac, and occupies the ventral third of the first nectophore. Its 

 cavity is nearly filled with large vacuolated polyhedral entoderm -cells. It is separated 

 by a thin septum from the ventral wall of the hydroecium. A short bent canal connects 

 its apex with the top of the common stem. 



Basal Nectophore (figs. 1, 9, lateral view from the left side ; fig. 10, distal part from 

 the right side ; fig. 8, ventral view ; fig. 11, basal view). — The second nectophore (the 

 distal, inferior, or basal nectocalyx) is about twice as long and broad as the first, and has 

 in general the form of an asymmetrical pentagonal pyramid ; but three of its five 

 edges are far more developed than the other two, so that the general appearance of 

 the irregular pyramid is more trigonal. Its apex is a curved conical condyle, its base 

 rounded. 



The five edges of the basal nectophore, one odd dorsal and four paired, corresponding 

 to those of Dipliyes and Calpe, are developed in a different manner ; the largest and 

 most prominent wing is the right ventro-lateral edge (nx), and next to it the obliquely 

 opposed left dorso-lateral edge (n 1 ). The odd dorsal edge (nd) is of intermediate size. 

 The left ventro-lateral edge (nl) is short and broad in the middle part ; the right dorso- 

 lateral edge is the smallest, and more rudimentary. 



The hydrcecial canal of the second nectophore is an open groove on its ventral side, 

 protected by the two broad ventro-lateral wings, the right of which (nx) is much larger 

 and overlaps the left (nl). The shorter left wing is prominent as a vertical triangular 

 plate, the inferior part of which is broad and its margin strongly dentate (figs. 8, 9, nl). 

 The larger overlapping right wing (nx) is more crescentic, and has a convex dentate 

 margin, which is much thickened in the inferior third ; the free basal edge of this 

 thickened margin bears two parallel rows of teeth ; the right row (nx") is somewhat larger 

 than the left (nx', figs. 8 11). 



The apical condyle of the triangular pyramid (figs. 8, 9, nq) on the articular apophysis 

 of the second nectophore, which fits into the hydrcecium of the first and connects them, 

 is curved and beak-shaped ; it contains on its concave ventral side a deep hydrcecial 

 groove, in its convex dorsal part the nectocalycine duct (en). 



The base of the second nectophore, seen from below (fig. 11), offers a very peculiar 



