1887.] The Norw. North-Atlantic Exped. 7 
far these rest directly upon the muscles, or whether there is an 
intermediate layer — or ventral layer — (Peritoneum) to which 
they are attached, in the manner that will subsequently be shown 
to be the case with the oesophagus and the intestinal canal, can 
not be here determined. 
All the septa carry mesenterial filaments and reproductive or- 
gans (Pl. I fig. 2). These have their origin exactly at the upper- 
most part of the gullet- tube, just below the oral dise; and are 
secured to the one surface of the septum, between the muscle- 
fibres, by a membranous prolongation of the connective-tissue of 
the septum. The septa have not, here, as usually is the case with 
the Actinida, a free margin to which the organs named are attached, 
as it will be remembered that there is in Fenja no gastrovascular 
cavity in which the septa could freely hang; on the contrary, they 
are everywhere secured, exteriorly, to the body-wall, and interiorly 
to the gullet-tube and the intestinal canal. The mesenterial fila- 
ments are placed next to the gullet-tube, and extend themselves 
spirally, backwards, (downwards) to nearly the middle of the rectum 
without, however, being secured to it (Pl. I fig. 2 b). Their struc- 
ture presents no divergence from the common. 
The reproductive organs are situated outside the mesenterial 
filaments, and are also secured to the septum by a connective- 
tissue prolongation which is clad with endothelium (Pl. I fig. 8, 9, 
10 a). The ovaries form ribbon-shaped, somewhat adpressed, tubes 
that twine themselves down along the septum, quite from the oral 
disc, and much farther than the mesenterial filaments (Pl. I fig. 8 b). 
I have seen, indeed, in one specimen, the ovary on a couple of 
septa terminate in the proximity of the bottom of the body-cavity. 
These tubes are clad, internally, with an epithelium, consisting of 
large, round cells, with nucleus and nucleolus, and, here, the ova 
are seen in various stages of development, usually lying two to- 
ge ther (Pl. I fig. 2 c, 10 b). 
The testicles lie outermost (Pl. I fig. 2 d, 8 c), so that the ova- 
ries are situated between them and the mesenterial filaments. 
They have their origin exactly at same point as the ovaries, but 
extend themselves farther backwards than the latter do. They are, 
like the ovaries, secured to the septum by a prolongation of its 
connective-tissue (Pl. I fig. 9 a), and consist of two spiriform, al- 
most round, tubes that are clad, externally, with cylindrical en- 
dothelial cells, which also cloth the mesentery, and between which 
a multitude of nematocysts are visible. Internally, they are coated 
