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



little distance from them ; the thirty-six following still easily recognisable ; the wall tra- 

 versed by reticulated furrows ; mesodermal muscle developed throughout the entire length 

 of the wall. 



jyrt?,/^rt;._Station 313. January 20, 1876. Lat. 52° 20' S., long. 68° 0' W. Depth, 



55 fathoms. Three specimens. 



Dimensions. — Diameter of the oral disk, 3-5-6-0 cm. ; height of the body column, 



2 -0-2 -5 cm. 



The three specimens of Antholoha reticulata included in the Challenger material were 

 admirably adapted for examination, as the body was only slightly contracted. This 

 applied especially to the largest specimen, which was 6 cm. broad and 2*5 cm. in height, 

 and upon which the following observations have been principally made. 



The pedal disk is very thin walled, so that the insertions of the septa shine through it 

 as innumerable clear lines ; the margin is indistinctly lobed, probably five-lobed like the 

 margin of the oral disk. The firm compact wall of the Actinia rises in a curve at an 

 acute angle from the pedal disk, and is constricted more or less distinctly at a third 

 of its height. The lower part of the wall is traversed by circular furrows, which are 

 perhaps merely caused by the contraction of the muscles of the body, its upper part is 

 covered with soft papillae, about 0"5-r5 mm. broad, which are not sharply separated, 

 lie close together, and are very much flattened. Shallow furrows, which give the surface 

 of the body its reticulate appearance, and which Couthouy had in view in naming the 

 species, remain between the papillae. 



The mesodermal circular muscle is never very strong, but, on the other hand, it extends 

 from the upper to the lower end of the wall, a formation which I have never found in any 

 other Actinia. In longitudinal section it can be distinguished by the naked eye as a 

 yellowish layer, situated close under the endoderm, which is 0'5 mm. broad in its upper 

 third, but diminishes as it runs downward (PL XIII. fig. 9). Its bundles of fibrillse (PL X. 

 fig. 11) are all very small but thickly compacted, and only separated by a little con- 

 nective substance ; they are all strongly flattened in the same direction in such a way that 

 their edges lie perpendicular to the endodermal epithelium. They have an inclination to 

 lie one behind the other in rows, which run outwards from the epithelium, and in this way 

 they have the appearance of being produced by the breaking up of long thin muscular 

 plates. The large bundles of fibrillse are found on the outside, but the smaller ones inside, 

 close under the endodermal layer of circular fibres,- which is repeatedly pleated over 

 them. From all this it seems probable that small bundles of fibriUae are continuously 

 detached by pleating from the endodermal layer, and are transformed by growth into 

 larger bundles in the depth of the layer. 



At the upper end the wall passes gradually into the oral disk, the margin of which is 

 swollen like a pad. The limits of the disk are indicated by the appearance of the ten- 

 tacles and the disappearance of the circular muscle. 



