REPORT ON THE SIPHONOPHOR^E. 161 



nectophore (first, superior or proximal nectocalyx) has the form of a pentagonal prism. 

 Its main axis is 5 mm. long, lies in the natural position of the vertical eormus (tigs. 1-4) 

 nearly horizontally, and is therefore perpendicular to the vertical main axis of the large 

 basal nectophore. The latter is three times as long as the former. The length of the 

 main axis of the apical nectophore equals the sagittal diameter of the basal nectophore. 



The dorsal face of the apical nectophore (fig. 6) is pentagonal, and in the natural 

 position of the vertically standing eormus directed upwards (fig. 1-3, ud). Seen from 

 above (fig. 6) the somatocyst (cs) and the nectosac (w) are visible through the trans- 

 parent dorsal face. The ventral face (fig. 5) is heptagonal, in the natural position 

 (figs. 1-4) directed downwards, and bisected by a horizontal transverse crest. The apical 

 half of the bisected face is pentagonal, slightly concave, and through it appears the 

 somatocyst (fig. 5, cs), whereas the basal half is excavated, and contains the campanulate 

 hyebcecium (fig. 5, id), in the fundus of which the siphosome arises. The basal face of 

 the apical nectophore (fig. 8) is square with four equal concave edges, and in its centre is 

 placed the aperture of the nectosac (uo). The remaining four faces are two basi-laterals 

 and two apici-laterals ; the former are pentagonal, the latter tetragonal ; and these two 

 are separated by the coryphal crest or sagittal edge (nk). 



The Nectosac of the Apical Nectophore (fig. 6, w ; fig. 8, w) is ovate and occupies its 

 basal half. Its circular basal aperture (fig. 8, uo) is small and surrounded by a broad 

 velum (v), and a circular canal (cc). The four radial canals of the subumbrella, which 

 discharge into the latter, are of unequal length ; the ventral canal (cv), near the 

 hydrcecium, being shorter, the dorsal canal (fig. 6, cd) longer than the two curved lateral 

 canals (ex right, cl left). The four radial canals unite in the apex of the nectosac, which 

 is united by a very short peduncular canal with the apex of the siphosome. 



Somatocyst (figs. 1, 2, 5, 6, 7, cs). — The somatocyst is subglobular, or spheroidal, 

 with slightly shortened main axis. It occupies the apical half of the proximal nectophore 

 and is nearly filled with large polyhedral entoderm cells, so that its central cavity is very 

 small. It is everywhere surrounded by the thick jelly-mass of the umbrella, and only at 

 its base in contact with the apex of the nectosac (fig. 6, w ) and with the meeting apex of 

 the hydrcecium (fig. 5, id) and the siphosome. 



Hydrcecium (fig. 1, ui; fig. 5, id). — The hydrcecium or the funnel-cavity is campanu- 

 late or obliquely conical, and its wide quadrangular mouth occupies the basal half of the 

 ventral face of the apical nectophore. The main axis of the hydrcecium is obliquely 

 inclined, and in the normal position (figs. 1, 2) directed from above and behind downwards 

 and forwards. The apex of the hydrcecium is the common central point, in which 

 the somatocyst meets with the peduncular canal of the apical nectophore and the apex 

 of the siphosome. 



The Basal Nectophore (figs. 1-4), or the distal nectocalyx, has in general the form of 

 an obelisk, or of a truncated four-sided pyramid. Its main axis is vertical in the normal 



(ZOOL. CHALL. EXP. — PART LXXVII. — 1888.) Hllllh 21 



