178 WONDERS .OF ORGANIC LIFE. 



with such address, that no appearance of an 

 excavation is, at least upon a casual survey, to 

 be perceived. This effected, they betake them- 

 selves to the bottom, and remain quiescent until 

 the return of spring, when they emerge from 

 their dormitories, retrace their journey to the 

 sea-side, and work out their summer habita- 

 tions. A species of gelasimns, a native of 

 South Carolina, was observed by M. Bosc to 

 migrate inland, and form a burrow, in which 

 retreat three winter months are passed. In 

 fact, according to that naturalist, this species 

 does not seek the water, until the period of 

 depositing its eggs. 



But there is a group of crabs still more ter- 

 restrial and more migratory than those to 

 which we have alluded. These crabs belong to 

 the genus Gecarcinus. They are known under 

 various names, as land-crabs, toulouroux, crdbes 

 peints, crdbes violets, etc. So decidedly are 

 their branchia? or gills organized for aerial re- 

 spiration, that if submerged for any length of 

 time in the sea, they will perish from suffoca- 

 tion ; nevertheless, it is essential that the 

 branchiae be always kept moist, for death, on 

 the other hand, results from the desiccation of 

 these organs.* The land-crabs are distributed 

 through the warmer regions of the Old and New 

 World, and are also found in Australasia ; but 

 the species are most numerous in America and 

 its islands. 



* The common woodlouse, Oniscus murarius, or Cloporte of 

 the French, within the pale of the Crustacea, requires a humid 

 locality for its existence, but is drowned in water. 



