38 THE VOYAGE OF H.M.S. CHALLENGER. 



mesenteries are somewhat shorter, and on account of the fact that the point where they 

 leave the stomodseum is nearer to the body-wall, have a shorter horizontal course ; they 

 bear a rudimentary mesenterial filament, but are devoid of reproductive elements. The 

 section of the ccelenteron corresponding to a tentacle will be seen from the foregoing 

 account to vary in different parts. Two tentacles correspond to the sagittal axis, one 

 being situated at each end of the stomodseum (these are " lateral " as regards the position 

 of the zooids on a pinnule). In these cases the section of the coelenteron corresponding 

 to a tentacle, that for example between mesenteries 1 and 12, is an enlargement of 

 one of the twelve interseptal chambers present in the oral cone. In the species under 

 consideration these tentacles are usually longer and thicker than the others, and 

 frequently extend horizontally in spirit specimens, whilst the other four stand up vertically. 

 The remaining four tentacles each cover a section of the coelenteron corresponding to 

 two and a half chambers in the oral cone. When the mesenteries numbered 3 and 

 10 come to occupy the median transverse axis, one tentacle corresponds to the space 

 between mesenteries 1 and 3, another to that between 3 and 6, and so on. 



Cirripathes ( Cirrhipathes). 



In the genus Cirripathes, as restricted in the present Eeport, the zooids are distributed 

 all around the axis, and are never found in single linear series, as in Stich<ypathes and 

 most other Antipathidae. Cirripathes propinqua, n. sp., has been selected as type of the 

 genus, in preference to the older Cirripathes spiralis, on account of the fact that it is 

 the only species of which I have been enabled to make a satisfactory examination of the 

 zooids. In this species the zooids are closely packed, more so apparently than in Cirri- 

 pathes anguina and Cirripathes spiralis. In spirit they are dull black in colour, have 

 a rounded outline, and the six tentacles are usually arched inwards over the mouth. 

 The greater portion of the peristome projects as a prominent round knob, on the surface 

 of which the mouth opens. The mouth is usually slit-like, and the elongation takes 

 place in the sagittal axis. Sometimes a portion of the stomodaeum is somewhat everted, 

 giving the aperture a crenate outline. The oral prominence is usually constricted at 

 the point where it joins the general surface of the peristome, as figured by Ellis 

 and Solander for Cirripathes spiralis. If a longitudinal incision be made through the 

 zooids and coenenchyma, and the whole stripped from the sclerobasic axis, it is seen 

 that the inner surface is traversed by numerous series of irregular rugae projecting beyond 

 the base of the zooids (PI. X. fig. 13). The precise relation of the zooids to the 

 sclerenchyma has not yet been made out, on account of the fact that the axis is 

 so thick and brittle that it is difficult to cut sections of it in situ. The tentacles are 

 comparatively thick and fusiform, and are arranged in a radiate manner. Those in the 



