244 Mr. E. Forbes on two remarkable Marine Invertebrata 



I notice them together, as, in each case, the peculiarity of 

 the organization and habit is the result of a similar adaptation 

 of form in two very distant tribes to a similar locality. 



The body of the Actinia is cylindrical, terminating poste- 

 riorly in an obtuse extremity, anteriorly in a disc, in the cen- 

 tre of which is a circular mouth surrounded by numerous, 

 rather short, linear tentacula, which spring from its internal 

 margin. Round the margin of the disc is another circle of 

 tentacula, thirty-two in number, very long, tubular and sim- 

 ple, resembling the tentacula of an ordinary Actinia or An- 

 thea. These tentacula cannot be drawn within the mouth, 

 but are highly contractile, and can be shortened to small di- 

 mensions. The disc and oral tentacula are white, the mar- 

 ginal tentacula are banded with yellowish brown ; the neck or 

 upper part of the body is white, and the remainder to the 

 extremity yellowish brown. The body can be greatly length- 

 ened, so as to assume the form of a worm or Holothuria. It 

 is protected by a membranous tube, which is itself strength- 

 ened by an incrustation of gravel and shells in the manner of 

 a Terebellum. In this tube the Actinia can. move up and 

 down freely; and when kept for some time in sea- water,. the 

 tube being injured, it came out of it altogether, and moved 

 about, twisting its body in the manner of some Annelides. 

 On being supplied with sand and gravel it proceeded to con- 

 struct another tube, rolling itself in the sand, and secreting 

 glutinous matter for the membranous lining. It eats vora- 

 ciously, and attacks other animals that come within reach of 

 its tentacula. It lives buried in sand, in places a few inches 

 below the sea-level. Internally its structure is similar to that 

 of others of its tribe. There are eight yellowish ovaries ter- 

 minating in as many long, contorted threads. 



In its habit of protecting itself by sand and gravel it resem- 

 bles Actinia viduata and some other species, none of which, 

 however, construct a regular tube. In its being free, and 

 having no adhesive disc at its posterior termination, it re- 

 minds us of Iiuanthos, a genus of Actiniadce which I dis- 

 covered three years ago on the Scottish coast, and which I de- 

 scribed and figured in the * Annals of Natural History/ vol. v. 

 p. 181. It is evident the animal I now describe fills up an 

 important gap among the Polypes, and leads to analogical 

 considerations of great interest to the philosophical zoologist. 



Whether the second animal I would notice, the tubicolar 

 Annelide, be described, 1 do not know, but have reason to 

 think it is not. It is one of the most beautiful creatures in a 

 beautiful but much-neglected family. It lives in sand where 

 the sea is three or four feet deep, and its position is indicated 

 by funnel-shaped cavities. At times, in sailing over their ha- 



