192 NECTOPYRAMIS DIOMEDEAE. 



Nectophore. The nectophore, in the better of the two examples, reaches 

 the unusual dimensions of 38 mm. in length bj'^ 26 mm. broad. It is roughlj' 

 rectangular as seen in side view (Plate 1, fig. 1), laterally compressed (Plate 1, 

 fig. 2) with a ridge extending from the level of the hydroecium to the dorsoapical 

 corner, and with the two lateral faces meeting along the dorsal edge in a rounded 

 subacute angle. In cross-section the nectophore is roughly triangular. At 

 the base the gelatinous substance projects below the level of the opening of the 

 nectosac in a triangular, but rounded, ventral, and a wedge-shaped dorsal promi- 

 nence (Plate 1, fig. 1). The nectosac is shallow, rounded; the hyroecium lies 

 transverse to the main axis of the nectophore, reaching dorsad nearly as far 

 as the dorsal face of the nectosac; it is deeper than broad, and opens on the 

 ventral edge by a narrow slit. Dorsally it is rounded, and sac-like, and it is 

 asymmetrical in form, as is seen in ventral view (Plate 1, fig. 2). 



Somatic canal system. The system of canals which replaces the somatocyst 

 is more complex than in N. thetis. Commencing with the point at which the 

 pedicular canal reaches the hydroecium, we can recognize a descending and an 

 ascending branch, as in the Prayinae. The former is very short and soon turns 

 apically, to run over the left-hand face of the hydroecium, where it branches 

 once (Plate 1, fig. 4), or twice (Plate 1, fig. 3). The ascending system is much 

 more extensive. In its passage over the dorsal sm-face of the hydroecium it 

 gives off two large branches, one subdividing twice, and running to the dorso- 

 basal angle (Plate 1, fig. 1, C. Pa ) the other branching four or five times, and 

 running to the apicodorsal angle (Plate 1, fig. 1, C. Pa ). The ascending canal 

 does not follow the upper wall of the hydroecium, but turns and runs to the apico- 

 ventral corner of the nectophore (Plate 1, fig. 1, C. Pa ). At the point at 

 which it bends apically it gives off a branch which runs over the left-hand face 

 of the hydroecium, and a short distance further on gives off a second trunk 

 which passes over its right-hand face. These two canals of the hydroecium are 

 asymmetrical, the right-hand one branching one and three, and the left-hand 

 one five and seven times respectively in our two specimens. {Cf. Plate 1, fig. 3 

 and fig. 4). In both A'', thetis and N. diomedeae, ascending and descending 

 branches can be distinguished, the former giving off the more or less complex 

 hydroecial canals. But, whereas it is the latter which are the parents of the 

 two canals running to the distal portions of the nectophore in N. thetis, in 

 A'', diomedeae these arise from the ascending trunk. The relation of the sub- 

 umbral canals to the somatic system is likewise different; for while in A^. dio- 

 medeae there is a single pedicular canal, in N. thetis all four subumbral canals 



