REPORT ON THE SIPHONOPHOR^E. 129 



be the " primary nectophore " of Monophyes gracilis ( = Sphseronectes gracilis), afterwards 

 replaced by a keteromorpkous secondary nectophore (87, Taf. ii. fig. 5). But this 

 supposition is not very probable, and I call this form provisionally Monophyes diptera, 

 provided that it does not belong to Cymbonectes (Genus 21). The eudoxomes of Mono- 

 phyes seem to ripen attached to the stem, and not to form free Eudoxice as in 

 Sphseronectes. 



Monophyes princeps, Haeckel (PL XXVII. figs. 13, 14). 



Sphseronectes princeps, Hkl., 1887, System der Siphonophoren, p. 34. 

 Habitat. — Indian Ocean; between the Maldive Islands and Socotra, March 1882 

 (Haeckel). 



Nectophore (fig. 13, lateral view from the left side ; fig. 14, transverse section at the 

 middle of the height). — The single nectocalyx is 6 mm. long and 3 mm. broad. Its form 

 is asymmetrical, nearly ovate, witk a flat constriction near the base. Tbe surface is 

 perfectly smooth, rounded, and without sharp edges. The transverse section (fig. 13) is 

 subcircular in the upper half, more ovate in tbe lower half. 



The dorsal half of the nectopkore, wkick includes tke nectosac (iv), is of a quite simple 

 ovoid form, bilaterally symmetrical. Tke ventral kalf, wkick includes tke sipkosome 

 in its kydroecial groove, is asymmetrical. Tke tkin frontal septum (nt), or tke vertical 

 transverse jelly-plate, wkick separates tke dorsal nectosac (w) from tke ventral kydroecial 

 canal (ui), gives off two large parallel and vertical ventral wings, wkick enclose tke latter. 

 Tke rigkt wing (nx) is larger, and overlaps tke smaller left wing (nl), so tkat tke ventral 

 opening of the hydrcecial groove becomes incompletely closed by tbe two overlapping 

 wings. Tke two wings are united at tke apical or upper blind end of tke groove, wkilst 

 tkey are prolonged into two broad ovate terminal lobes at tke basal or lower opening of 

 the groove. 



Nectosac (figs. 13, 14, w). — The subumbrella of the nectophore occupies its dorsal 

 kalf (witk exception of tke apical tkird) and is subcylindrical, slightly concave on tke 

 dorsal, convex on tke ventral side, witk curved axis. Tke nectocalycine duct, wkick 

 arises from tke top of tke stem, is very skort, enters into tke ventral wall of tke 

 nectosac somewkat below its rounded apex, and divides into four curved radial canals ; 

 the ventral of these (cv) is shorter, the dorsal (cd) longer, than the two paired lateral 

 canals (cl left, ex right). They are united by a circular canal above the broad 

 velum (v). 



Hydroscium (figs. 13, 14, ui). — The cavity at the ventral side of the nectophore, 

 which includes the retracted siphosome (as), is a flattened canal, the frontal diameter 

 of which is twice as great as the sagittal. It is separated from the neighbouring ventral 

 side of the nectosac (w) by the thin frontal septum. The hydrcecial canal is blind at 



(ZOOL. CHALL. EXP. PART LXXVII. — 1888.) Hhlih 17 



