REPORT ON THE SIPHONOPHORvE. 129 



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

 replaced by a heteromorphous 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 Eudoxise as in 

 Sphseronectes. 



Monophyes princess, Haeckel (PI. 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, with a flat constriction near the base. The surface is 

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

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



The dorsal half of the nectophore, which includes the nectosac (w), is of a quite simple 

 ovoid form, bilaterally symmetrical. The ventral half, which includes the siphosome 

 in its hydrcecial groove, is asymmetrical. The thin frontal septum (nt), or the vertical 

 transverse jelly-plate, which separates the dorsal nectosac (iv) from the ventral hj'drcecial 

 canal (in), gives off two large parallel and vertical ventral wings, which enclose the latter. 

 The right wing (nx) is larger, and overlaps the smaller left wing («/), so that the ventral 

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

 wings. The two wings are united at the apical or upper blind end of the groove, whilst 

 they are prolonged into two broad ovate terminal lobes at the basal or lower opening of 

 the groove. 



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

 half (with exception of the apical third) and is subcylindrical, slightly concave on the 

 dorsal, convex on the ventral side, with curved axis. The nectocalycine duct, which 

 arises from the top of the stem, is very short, enters into the ventral wall of the 

 nectosac somewhat 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). 



Hydrosdv/m (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.) Hhhh 17 



