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MANUAL OF ZOOLOGY 



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, 



FIG. 63. A, Dendrophyllia nigrescens; B, Madrepora aspera. Natural size. 

 co, corallites ; cs, coenosarc; /, polypes. Pacific Ocean. (After Dana.) 



and to the pain caused by its poisonous stinging-capsules, 

 is usually avoided as an article of food. 



A similar case is that of Cancrisocia, of the China seas, 

 which lives on the back of a crab (Dorippe facchino, 

 Fig. 64). The crab carries, for its protection when young, 

 a small shell over its back, which it holds in this position by 



