THE DECAPOD CRUSTACEA. 185 



the hermit-crabs dredged from deep water, or cast ashore 

 after storms, seem at first sight to be markedly contrasted. 

 They inhabit the large shells of full-grown specimens of 

 Fusus or Bticcinum, shells often nearly six inches in length 

 and heavy in proportion, and the hermits reach a size 

 commensurate with that of their dwellings. The abdomen 

 is a deep brick-red, and the rest of the body deeper in 

 tint than in the shallow-water forms. It requires some 

 study to convince one's self that such hermits are not specifi- 

 cally distinct from the more familiar forms found on the 

 tidal rocks, and the fact that the latter become mature in 

 shallow water, almost justifies one in speaking of them 

 as a variety. 



One other point of interest about the hermits is their 

 habit of living in symbiosis or partnership with other 

 animals. In certain localities the hermits very commonly 

 inhabit shells covered externally by the beautiful zoophyte 

 Hydractinia. This seems, however, to depend very largely 

 upon the locality. Most hermits from deep water have, as 

 companions within their shells, one or more specimens of a 

 very beautiful worm, Nereis fucata (see p. 106). So common 

 is this association, that in some places fishermen catch the 

 hermits, and turn them out of their shells for the sake of 

 the partner worms, which are used as bait. It is not easy 

 to see what the hermit gains by the presence of the worm, 

 but at least it is not injured by it, as it is by another 

 common associate, the parasitic Peltogaster, which hangs 

 like a sac from the under surface of the abdomen in very 

 many hermit-crabs. 



As everyone who has tried to keep hermits in confinement 

 knows, they are exceedingly sensitive to unfavourable con- 

 ditions, especially to a diminished oxidation of the water. 

 The first sign of discomfort displayed is the tendency to 

 quit the shell, or to change rapidly from one shell to another, 

 and this restlessness is usually quickly followed by death. 

 It is difficult to say whether this delicacy of constitution 

 is due to a difficulty in respiration produced by the shell, 

 or to that racial decadence which has made the appropriation 

 of the shell necessary. If, however, you wish to keep the 

 hermits alive, they must be allowed a large bulk of water, 

 as frequently renewed as possible. Under such conditions 



