FOOD, HABITS, ETC. 81 



the coral polyps draw towards themselves by their 

 ciliary action. So, too, probably do its close rela- 

 tives Coralliophila, Leptoconcha, and Rhizochilus. The 

 last named in its adult state attaches itself to the 

 branches of Antipathes, and all but closes the mouth 

 of its shell (Plate XL, Fig. i). 



Some of the Bivalves, which bore into coral, such 

 as Coralliophaga and Lithodomns, may also similarly 

 profit by their situation. 



Whether the occurrence of the small Planorbis-like 

 Cochliolepis, which was found in Charleston Harbour 

 under the scales of the Annelid (A coetes), was a case 

 of commensalism or parasitism has not yet been 

 made clear. 



Several molluscs are themselves parasitic on other 

 creatures : Starfish and Echinoderms are peculiarly 

 liable to these parasites. Stilifer (Plate XXVI. , 

 Fig. 27) and Robillardia nestle among the spines of 

 Echinoderms, while both the former and Stiliferina 

 occur buried in the skin of Starfish, and Thyca, one 

 of the Capulidse, attaches itself to the under side of 

 the rays. These feed on the juices of their host, 

 which they absorb through the long proboscis they 

 insert into their victim. The Sea-Cucumbers come 

 even worse off, for not only are they thus similarly 

 attacked from without, but afford lodgment within 

 to a variety of blood-suckers — viz., Entovaha, a 

 Bivalve; Eulima (Plate XXVI., Fig. 26), a relative 

 of Stilifer ; and a series of other Gastropoda, Ento- 

 6 



