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



Jourdan, E., Recherches zoologiques et histologiques but les Zoanthaires du Golfe de Marseille, Ann. Sci. Nat. 



(Zool.), s.k 6, t. x. pp. 1-154, 17 pis., 1879-80. 

 Koch, G. von, Fauna u. Flora d. Golfes v. Neapel., Monogr. xv., Die Gorgoniden, Berlin, 1887. 

 Wilson, E., The Development of Renilla, Phil. Trans., vol. clxxiv., 1884. 

 Wilson, E., The Mesenterial Filaments of the Alcyonaria, Mith. d. Zool. Stat. z. Neapel, Bd. v., 1884. 



Antipathella subpinnata. 



The polyps of this species are subregular in size, but occasionally near the apex of 

 a pinnule small and immature individuals are to be observed (cf. PL XIII. fig. 3). 

 The average length of a polyp in the sagittal axis is 1 mm., and about 0'5 mm. in 

 the transverse axis. The elongation in the transverse axis is frequently most marked in 

 young individuals. The tentacles in spirit specimens are subcylindrical with a dilated 

 base ; they may be 0"6 mm. long. The space between the tentacles is occupied by a large 

 rounded prominence, on which the mouth opens. The oral aperture is usually much 

 elongated and slit-like. In certain cases, where the mouth is preserved widely open (PI. 

 XIII. fig. 4), it forms a large, circular, shallow pit, exposing the elongate stornodgeum below, 

 and has a diameter corresponding with that of the oral prominence itself. The outer 

 margin is circular, but the inner one is crenate, each depression corresponding with the 

 insertion of a mesentery. The zooidal tissues consist of a relatively thick ectoderm, a 

 thin and apparently homogeneous mesoglcea, and a glandular entoderm of variable thick- 

 ness. The polyps are incompletely separated from one another by plate-like mesoglceal 

 septa, clothed on each side with entoderm. In sections parallel to the axis of a pinnule, 

 but which do not pass through the sclerobasic axis and its surrounding tissue (PI. XIII. 

 fig. 5), the septa are seen to pass straight across from the mesoglcea of the zooidal 

 surface to that beneath. In mesial sections, however, the septa are seen to cease 

 above the circumaxial tissue, and a series of transverse sections of a pinnule in the 

 interzooidal regions shows that each septum has a somewhat circular aperture near its 

 base, through which the sclerenchyma and the tissue surrounding it pass. As the 

 septa are not fused with the circumaxial tissue, the ccelentera of adjoining polyps are in 

 communication with one another at this point. The stomodseum is much elongated in 

 the sagittal axis of the polyp and has a slit-like lumen. It consists of a flattened, 

 straight or slightly-folded, tube, which reaches to within a short distance of the circum- 

 axial tissue (cf. PL XIII. figs. 5, 6, and 7). In sagittal sections (PL XIII. fig. 6) it- 

 extends to a point on a level with the insertion of the sagittal tentacles, and the free 

 border is usually somewhat thickened. In sections parallel with the long (transverse) 

 axis of a polyp, the inner margin of the stornodseurn is seen to take a sharp bend 

 outwards, and, after a short subhorizontal course, it ultimately fuses with the transverse 

 mesenteries. The structure and arrangement of the mesenteries is best studied from 

 a series of horizontal sections, commencing at the surface of the oral cone. A little 



