146 THE INDUSTRIES OF ANIMALS. 



dangers from without, undergoes development, and 

 one fine day the little fish emerges and frisks away 

 from his peaceful retreat. 



Other animals, more respectful of property, avoid 

 using another's dwelling until it is abandoned by its 

 proprietor, and no reproach of indelicacy can be 

 addressed to the Gobius minutus, a fish which lives 

 on our coasts at the mouth of rivers. The female lays 

 beneath overturned shells, remains of Oysters, or 

 Cardium shells. The valve is buried beneath several 

 centimetres of sand, which supports it like a vault. It 

 forms a solid roof, beneath which the eggs undergo 

 their evolution. Sometimes the male remains by the 

 little chamber to watch over their fate. It is possible 

 to distinguish the two holes of entrance and exit 

 which mark his habitual passage. 



The Hermit-crab perhaps knows best how to take 

 advantage of old clothes. (Fig. 19.) He collects 

 shells of Gasteropods, abandoned flotsam, the first 

 inhabitant of which has died. The Hermit-crab 

 {Pagurus Bernhardus) is a Decapod Crustacean — 

 that is to say, he resembles a very small Crab. 

 But his inveterate habit during so many generations 

 of sheltering his abdomen in a shell prevents this 

 part from being encrusted with lime and becoming 

 hard. The legs and the head remain in the 

 ordinary condition outside the house, and the 

 animal moves bearing it everywhere with him ; on 

 the least warning he retires into it entirely. But 

 the Crustacean grows. When young he had chosen 

 a small shell. A Mollusc, in growing, makes his 

 house grow with him. The Hermit-crab cannot do 

 this, and when his dwelling has become too narrow 

 he abandons it for one that is more comfortable. 



