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 XI., Fig. 1). 
Some of the Bivalves, which bore into coral, such 
as Coralliophaga and Lithodomus, 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 coétes), 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 Capulidz, 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., Entovalva, a 
Bivalve; Eulima (Plate XXVI., Fig. 26), a relative 
of Stilifer ; and a series of other Gastropoda, Ento- 
6 
