1887.] The Norw. North- Atlantic Exped. 15 
There are 12 septa, which have their origin in the inner wall 
of the body and extend quite from the anal aperture and up to 
the under surface of the oral disc, to which they attach themselves, 
whilst also, they all insert themselves on the exterior surface of the 
gullet-tube and intestine (Pl. II fig. 11, PL III fig. 2). 
The cavity of the body is thus divided into 12 chambers 
(Pl. III fig. 2) that communicate with each other through a small 
semi-lunar opening (oral-stomata) which is found on the septa, ex- 
actly at the point where they attach themselves to the oral disc; 
the chambers, otherwise, appear to be closed. Anteriorily, or at 
the top round the gullet-tube, they are very broad, but the more 
they approach to the posterior extremity the narrower do they be- 
come, so that around the rectum they are very narrow. The in- 
dividual septa are placed at uniform distances apart, and are not in 
pairs, whilst, also, there are none of them that can be considered 
as directive septa (Pl. III fig. 2). In one specimen a few septa ap- 
peared to be somewhat different from the rest, as they were a iittle 
shorter, so that the distance between the wall of the body and the 
intestine became less, and, as a consequence of that, the correspond- 
ing chambers became narrower; but it may perhaps be, that this 
difference may have arisen from an irregular and violent contrac- 
tion, and we are therefore not in a position to form a definite con- 
clusion from it. 
The septa are formed of fibrillous connective-tissue, which is, 
here, pretty thick, and really is a continuation of the connective- 
tissue of the wall of the body, with a muscular arrangement 
quite like that of Fenja mirabilis; as both sides are clad with long- 
itudinal muscles, whilst the transversal muscles, which only occupy 
one side, appear to be little developed, and are covered by the 
longitudinal muscles (Pl. III fig. 1). 
From both sides of the septa a multitude of thin connective- 
tissue ramifications issue (Pl. III fig. 1 a), and on these sit the 
muscle-fibrils (Pl. III fig. 1 b), causing the whole to acquire a beauti- 
ful fruticous appearance. But as the longitudinal muscles issue from 
the wall of the body, in order to distribute themselves on both 
sides of the septa, they send along their insertions a collection of 
strong muscular bundles, which form the longitudinal muscles of the 
wall of the body and extend from the posterior extremity to the 
under surface of the oral disc, where they distribute themselves. 
These 12 longitudinal muscles are so broad, that when the animal 
is dilated they may be observed through the integument. 
