NECTOPYRAMIS DIOMEDEAE. 



193 



extend beyond the nectosac to the hydroecium; but although the canal system 

 of N. diomedeae is much the more complex, the difference is not an essential one, 

 being of degree only. The difference is therefore better regarded as of specific 

 than of generic significance. The subumbral canals are direct, not bowed. 



Stem and appendages. These, though much contracted, were well pre- 

 served. An important feature is the absence of any signs of the previous attach- 

 ment of a posterior nectophore, or of any reserve buds which might suggest the 

 future development of such an organ. The appendages consist, for the most 

 part, of very young siphons and tentacles and 

 of the buds for gonophores and bracts; but 

 near the extremity of the stem in one example 

 all three organs are much further advanced. 

 Most important is the bract because it links 

 this species with the Eudoxid described below. 

 The largest bract is about 1.5 mm. long; in 

 outline it is triangular, laterally compressed, 

 with prominent antero- and posterobasal angles. 

 There is a deep basal concavity enclosing the 

 proximal portion of its pedicular canal, and 

 foreshadowing, not only in situation but in 

 form, its future hydroecial cavity. Its somato- 



cyst is represented by four canals arising together from the apex of the basal 

 concavity, one running to the apex, one to the anterior basal angle, the other 

 two toward the posterior basal angle, but over the faces of the future hydroe- 

 cium. The apical trunk already shows the beginning of a branch, and each of 

 the two hydroecial canals bears a branch of considerable length (fig. A). 



The siphons, each of which shows a well-marked basigaster, are of the 

 usual type. 



The tentilla are of the usual Calycophorid type, but are unusually large, 

 and differ in form from those of other Monophyids (e. g. Cuboides Chun, 

 '92, pi. 12, fig. 14). Their most distinctive features are the thickening, marking 

 the beginning of the contractile portion of the stalk, and the arrangement of 

 the nematocysts as the walls of a cylinder, which in young stages is compara- 

 tively long, in older ones shorter and more knob-like. It likewise appears to 

 be very contractile. The young gonophores, among which both 9 and d' 

 could be distinguished, already show the deep ventral furrow noticeable in their 

 ripe state. 



Fifi. A. — Nectopyramis diomedeae. 

 Bract. 



