REPORT ON THE ACTINIARIA. 33 



membrane forms a circular fold, with numerous small evaginations on its edge. 

 These correspond to the intraseptaJ and interseptal spaces, and must be compared to the 

 marginal spherules, which are found in the same situation in Actinia mesembry anthem nm, 

 and are conspicuous by their splendid colour ; they are, however, not so richly furnished 

 as in the above-named Actinia with the strongly refractive nematocysts, which Rotteken, 

 Schneider, and Duncan (Proc. Roy. Soc, London, vol. xxii. p. 263) held to be retinal rods, 

 and were thus led to regard the marginal spherules as eyes. 



The circular muscle (PL VI. fig. 6) is not visible to the naked eye, as it is veiy 

 weak, and may be easily overlooked even under the microscope. The endodermal circular 

 muscular layer is only folded a little more thickly than at other points, and shows three to 

 four larger and a few smaller dendritic figures in transverse section. The folded muscular 

 lamellae, which are supported by relatively strong connective substance, project towards 

 the gastric space, and are not enclosed in the connective substance of the wall, and in 

 this way an insignificant circular swelling is formed. The nature of the circular muscle 

 as described above furnishes a further point of comparison with Anthea cereus, in which 

 the organ is only slightly stronger. 



The tentacles are over a hundred in number, and lie in three circles close to the 

 peripheral margin of the oral disk ; the largest of them, belonging to the innermost circle, 

 are only 0"5 cm. long ; they are all thick-walled, and as thick at the rounded end as at 

 the base. They are pierced by a small terminal opening, wdiich is usually perceptible to the 

 naked eye, especially in tentacles from which the epithebum has been stripped off. 



The longitudinal muscles in the ectoderm, which pass on to the oral disk as radial 

 fibres, recall in many respects the ectodermal muscular fibres in the wall of Cerianihus ; 

 they are borne by very thin supporting lamella?, which are slightly branched and 

 lie close together, though they never attain the same extraordinary length as in 

 Cerianthus (PI. VIII. fig. 9). Here and there we find isolated mesodermal bundles 

 of muscles, whose fibres correspond in their extreme fineness to the longitudinal 

 ectodermal muscles. As the wide oesophagus protrudes outwards the numerous longi- 

 tudinal streaks on it are almost obliterated. The oesophageal grooves are also some- 

 what indistinct, as the tube is folded irregularly here and there. There is no reason, 

 however, to question their existence, as I observed the directive septa in transverse 

 sections. 



All the septa appeared to be perfect, though the youngest did not reach far down 

 the oesophagus. I could not settle their number accurately : the portion which I cut off. 

 and which I took to be about one-fourth of the entire animal, contained six pairs of two 

 different sizes, the smaller alternating regularly with the larger. This would give forty- 

 eight septa for the whole animal, which are distributed in three cycles, taking for granted 

 that this Actinia follows the hexamerous type. This view is so far warranted by the 

 undeniable approximation of Comactis flagellifera to the hexamerous Anthea cereus. 



(ZOOL. CHALL. EXP. — FART XV. — 1882.) P 5 



