31 



portion to the central part of the digestive cavity situated in the disc, at least quite as 

 strongly developed as in the others, extending about to the end of the l sl third part of the 

 arms, and are thus more than 4 times as long as the diameter of the disc (see Tab. VI, 

 fig. 35). They take their issue as single rather wide and somewhat flattened tubes in the 

 periphery of the upper section of the stomach (see Tab. II, fig. 8 c c, fig. 10) and radiate thence 

 on all sides, extending horisontally over the lower folded section of the stomach and over 

 the ambulacral plates of the disc into the cavities of the arms. Immediately on entering 

 into the arms, they divide themselves fork-like into 2 main trunks (see Tab. II, fig. 8 c on 

 the right; Tab. Ill, fig. 25 a) which then run side by side in a tolerably straight direction 

 along the dorsal side of the arms. On each side, these main trunks send out short and 

 closely placed thin-skinned lobes or secondary caeca, variously folded and contorted, giving 

 to the whole organ an elegant ramified appearance. The radial caeca, the number of which 

 will thus correspond with that of the arms, are firmly attached to the inside of the dorsal 

 skin in their whole extent by 2 longitudinal parallel ligaments. At a short distance from 

 the issue of the radial caeca from the stomach, each of these ligaments is connected with 

 the adjacent one by a thin arched commissure which is likewise firmly attached to the 

 dorsal skin. Then they separate themselves from this skin, and follow the radial cseca to 

 their issue from the stomach, going over into the upper wall of the latter, after having 

 again connected themselves with their neighbors by a thin membrane, which on the out- 

 side is deeply concave. The stomach is hereby as it were suspended from the dorsal skin 

 by a sort of rather complicated mesentery pierced at the angles between the issues of the 

 radial caeca, by large semilunar apertures, through which the central space between the roof 

 of the digestive cavity and the dorsal skin communicates with the other perivisceral cavity 

 (see Tab. VI, fig. 6). 



The fluid contained in the cavities of the radial caeca is of a more or less clear yel- 

 lowish color, and contains a considerable quantity of fat or oil which collects itself in larger 

 or smaller bubbles on the surface of the water, when the caeca are opened and the contents 

 allowed to flow out. 



8. The perivisceral cavity (c&loma) and the Blood system. 



The cavity, immediately limited by the skin and the interior skeleton, which contains 

 the various viscera, is in the Brisinga well developed; and it is not, as in the Ophiurae, only 

 restricted to the disc, but extends also, as in the proper star-fishes, into the arms and even 

 to their extreme points. In the basal section of the arms, it is (see Tab. Ill, fig. 3) very 

 wide; so that besides the radial caeca (d d) it can here contain also the frequently very 

 strongly developed organs of generation (e e). In the periphery of the disc, the cavities of 

 the arms are by a proportionally very narrow aperture connected with the cavity of the 



