THE PAGURI. 187 



the shell as exactly as the lid or operculum of its original pos- 

 sessor. It is surprising how rapidly they will rim about with 

 the dwelling they have appropriated on their back ; and when 

 by the progress of their growth it becomes uncomfortably 

 narrow, the remedy is easy, as convenient shells abound 

 wherever hermit-crabs exist. 



Thus we find a wonderful harmony between the organization 

 of the paguri and the structure of the alien domicile to which 

 they owe their safety, and which serves to complete their exist- 

 ence. Evidently the same creative idea has given birth to the 

 mollusc and the crab, for how could mere fortuitous circum- 

 stances have produced so marvellous a relation between animals 

 belonging to two classes so widely distinct ? 



In point of intelligence the crustaceans are far inferior to the 

 insects. Their instincts are confined to the violent seizure or 

 the cunning entrapping of their prey, to the burrowing of a 

 hole in the ground, or to the seeking of a shell fit for the con- 

 cealment of their otherwise defenceless body : in them we find 

 no care for their young, no mutual affection, no joint labours 

 for the welfare of a large community, no love but frequent out- 

 bursts of an angry and quarrelsome temper. 



The land-crabs, however, afford us a remarkable instance 

 of that wonderful migratory instinct which in the following 

 chapters we shall have frequent occasion to admire. These 

 animals generally spend their days in holes and cavities 

 among the mountains ; but when the season for spawning 

 arrives, vast armies of them set out from the hills, marching in 

 a direct line towards the sea-shore, for the purpose of depositing 

 their eggs, which are attached to the lower surface of the abdo- 

 men and are washed off by the surf. On this grand expedition 

 they pursue so direct a line to the place of their destination 

 that scarcely anything will divert their course ; even the most 

 formidable obstacles are overcome by their unyielding perse- 

 verance. When they have effected the purpose for which they 

 undertook their journey, they recommence their toilsome march 

 to their upland retreats. They set out after nightfall, and 

 steadily advance until the approach of daylight warns them to 

 seek concealment in the inequalities of the ground, or among 

 any kind of rubbish, where they lie ensconced until the stars 

 again invite them to pursue their undeviating course. Of the 



