206 



ZOOLOGY 



SECT. 



and in this way secures a more varied and abundant food-supply 

 than would fall to its lot if it remained in one place. On the other 

 hand, the Hermit-crab is protected from the attack of predaceous 

 Fishes by retreating into its shell and leaving exposed the Sea- 

 anemone, which, owing to its toughness, and to the pain caused 

 by its poisonous stinging-capsules, is usually avoided as an article 

 of food. Species of Peachia, which in the adult state burrow in 

 sand, in a larval condition live as parasites or commensals in the 

 radial canals of Scyphomedusse. 



" 



.-- 



.* 



FIG. 158. Adamsia palliata, four individuals attached to a Gastropod shell inhabited by 

 a Hermit-crab, ac. ac l . acontia ; sh. shell of Gastropod. (After Andres.) 



Other Sea-anemones such as the gigantic Discosoma of the 

 Great Barrier Reef are found associated with small Fishes or 

 Crustacea, which have their abode in the enteric cavity. In this 

 case the Fish secures shelter in a place where it is very unlikely to 

 be disturbed, and the two animals are strictly commensals or " mess- 

 mates " since they share a common table. A somewhat similar 

 instance is furnished by the Blue Coral (Heliopora), already referred 



