CTENOPHORA. 



plane. That both of them open to the exterior I do not doubt, though I have not directly observed 

 both openings. In the series of sections after which PI. VII. Fig. i has been drawn it is directly seen 

 that the left canal opens to the exterior (apparently on a small papilla, which may, however, be due 

 only to contraction on the preservation); on the right side there is certainly also an exterior opening, 

 but the lumen of the canal was not traceable the whole way from the outer opening to its opening 

 into the infnndibulum. Neither have I been able to make the canals out in a more satisfactory way 

 in other series of sections. Still I think there can be little doubt of both canals really opening to the 

 exterior, the more so as they have been directly observed to do so in the young Cydippid-larvse. 

 They are distinctly ciliated (PI. VII, Fig. 5). The openings are not shifted obliquely to the right or left 

 of the sagittal plane as is otherwise the case in Ctenophores, and there appear to be no ampullae; but 

 the position of the canals in the sagittal plane is in accordance with what obtains in typical Ctenophores, 

 the difference being only that the canals are not dichotomously branched at their upper end. (For the 

 relations of the pharynx, infundibulum and apical organ, comp. also PI. VI. Figs. 2 and 9). In some of 

 the sections I have observed small excrement-like masses lying in the excretory canals. Also sperma- 

 tozoa have been observed lying in them. 



Figs. I --2. Diagrams of the gastrovascular system and genital organs of a typical, tentaculate, Ctenophore (Fig. i) and of 

 Tjalfiella (Fig. 2). ar. v. adradial vessel (in Tjalfiella represented by the genital vessel); br. c. branching gastrovascular canals; 

 ch. o. "chimney" opening; ir. v. interradial vessel; m. v. meridian vessel; ph. pharynx; ph. v. pharyngeal vessel; t. tentacle; 



tr. v. transverse vessel; t. sh. tentacular sheath; t. v. tentacular vessel. 



The gastrovascular system. From the infnndibulum proceeds to each side in the transverse 

 (tentacular) plane a rather large vessel which continues to the tentacle, sending a branch into each 

 side-half of the tentacle-base, as is the usual condition in Ctenophores. From this main vessel (the 

 transverse canal) further proceeds a small branch towards each genital organ, into the lumen of which 

 it opens. Finally a large branch divides off from the main vessel below each subtentacular genital 

 organ; this branch continues into the walls of the body, where it ramifies, forming thus the branching 

 canals so conspicuous through the transparent epidermis, especially on the "chimneys". (PI. Ill, Figs. 9 

 and 10 show the relation of the genital canals and the branching canal to the main vessel; the open- 



TUc Ingolf- Expedition. V. 2. 2 



