362 POLYZOA INFUNDIBULATA. 



3. A. PARASITICUM, incrusting corallines^ earthy, the surface 

 Rev. Dr. Fleming. 



PLATE LXVIII. FTG. 4, 5. 



Alcyonium parasiticum, Flem. Brit. Anim. 518. Alcyonidium parasiticum, Johns. 

 Brit. Zooph. 304, pi. 41, fig. 4, 5. Couch Corn. Faun. iii. 134. Hassall in Ann. 

 and Mag. N. Hist. vii. 370. Reid in Ann. and Mag. Nat. Hist. xvi. 393. Halo- 

 dactyle parasite, Van Beneden Recherch. 62, pi. 8, fig. 9-12. 



Hob. Parasitical on Sertulariadse. 



This production spreads up the stem and branches of various flexi- 

 ble corallines, coating them with an incrustation of an earthy appear- 

 ance, from a line to the eighth of an inch in thickness. The sur- 

 face is porous or cellular, even, roughish, the pores roundish or 

 pentagonal, distinct and separate, but not arranged in rows, or in 

 any regular fashion ; the interior is irregularly cellular, and earthy. 

 None of the mineral acids have any effect on this substance, nor does 

 it absorb water like a sponge, but when dropped into a glass of water, 

 it sinks to the bottom, and lies there unaltered. No siliceous nor 

 calcareous spicula enter into its structure, but it seems to be entirely 

 composed of particles of sand cemented together with mud or clay. 



Considerable doubts were entertained of the nature of this unat- 

 tractive production, which have been entirely removed by the re- 

 searches of Mr. Hassall, Van Beneden, and Professor Reid. The best 

 account of the polypes is given by the last naturalist. They have 

 fifteen or, as Mr. Hassall says, sixteen tentacula, nearly of the length 

 of that part of the animal which protrudes beyond the cell, and 

 these are ciliated. " Before the animal protrudes itself it pushes up 

 from the interior of the cell a short tube of the form of a truncated 

 cone. From the orifice of this tube several hairs or very fine bristles 

 project. This tube next becomes still more elongated; and this 

 elongation is evidently effected, not by its continued protrusion, but 

 by the unfolding of a part which had been previously bent inwards. 

 When this takes place the hairs or bristles are now seen to be at- 

 tached to the edge of the opening in this tube, instead of protruding 

 out of its interior. These bristles are connected at their base by a 

 fine membrane; and, if I am not mistaken, the tube itself is composed 

 of similar bristles connected together by a membrane. This tube is 

 translucent, and the tentacula are seen within it. The neck of the 

 polype projects, when the animal protrudes itself, to a considerable 

 extent. The mouth is rounded, is surrounded by the tentacula, and 

 opens into a very wide cavity (pharynx). On breaking up some of 



