528 On Arachnactis brachiolata. 



The same bilateral symmetry can be traced in the tenta- 

 cles which surround the mouth. The largest are placed 

 nearest the odd tentacle, and they decrease in size toward 

 the opposite extremity of the mouth. 



The body is of a pale ochre color, perfectly transparent; 

 the edge of the tentacles and of the partitions appears some- 

 what darker, owing to the thickness of the walls. The 

 extremity of the column is rounded, the wall is slightly 

 thickened there, and there is no trace of any opening at the 

 base of the columns or at the tip of the tentacles. The 

 digitate appendages which hang in the cavity of the body 

 are simply thin folds of the prolongation of the partitions 

 twisted like a corkscrew as they become longer. When 

 seen from the narrow side, (fig. 2,) these appendages are 

 arranged symmetrically on both sides of the longitudinal 

 axis of the body; but when seen from the broad side, the 

 curves are always in one direction, the convexities turned 

 away from the side where the odd tentacle is placed. 



The tentacles of the mouth slit are short, conical, almost 

 always carried vertically upward, but when the sides of 

 the digestive cavity are in great activity and project be- 

 yond the surface of the disk, they are often extended per- 

 fectly flat upon the actinal area. In young specimens, 

 (fig. 1,) the whole cavity of the column is filled with a 

 spherical mass composed of large polygonal yolk-cells. 

 Tins sphere revolves slowly about in the interior, and as 

 the actinia becomes older it is reduced in size, and the 

 space is filled by the digitate appendages. When the 

 actinia is in motion, the young tentacles are on the side 

 of the body which is nearest the surface, the long, heavier 

 tentacles being below. 



The youngest specimens of Arachnactis found resemble, 

 in a striking manner, the more advanced figures given by 

 llaime,* of the young Cerianthus. The mode of develop- 



* Hiiimo, Jules, Mt'moire sur lo Ceiiaiithe ( Cerianthus membranaceus). Aun. Sc. 

 Nat. 4<^ Scr. I. p. 341. 



