54 CRUSTACEA. 



the ready-made coats in a clothing store, until it finds 

 one to fit, when it slips in and closes the entrance with 

 its large arms. The habit of hiding either a part or 

 the whole body in holes arises from the desire for 

 protection, and we can readily understand how such 

 animals, seeking protection, should gradually lose the 

 parts which had been made useless by the new habit, 

 or should modify others which still remained useful, or 

 perhaps even develop new organs. In this connection 

 the great Hirgus, or Palm-thief, is of special interest. 

 This is a land-crab which inhabits the islands of the 

 Pacific and Indian oceans. Instead of seeking for 

 safety in deserted shells, these crabs make deep holes 

 in the ground, beneath the roots of cocoa-nut trees. 

 In Woods' "Homes without Hands," the crabs are 

 pictured in the act of husking and feeding upon the 

 nuts. The jaws of the first pair of legs do most of the 

 hard work in husking the fruit, and the meat is taken 

 out through the soft "eyes" of the nut by the hinder 

 pair of walking-legs after they have been bored out by 

 the jaws. 



The crabs go to their original habitat, the sea, to 

 lay their eggs, and the young are hatched and live for 

 some time on the coast. The Hirgus is very instruc- 

 tive, as it illustrates how a marine animal may become 

 adapted to live on the land and breathe air instead 

 of water. It appears to have accomplished this by 

 changing a part of each gill-cavity into a lung. 



According to Semper,* each gill-cavity consists of a 



* Zeitsclirift fur Wissenschaft. Zoologie, Vol. XXX. Trans- 

 lated in International Scientific Series, " Animal Life as affected 

 by Natural Conditions," by Carl Semper, 1881. 



