THE (J It AT FISH 



139 



to the length of their aljclomen. The abdomen is soft, and 

 the young animal, which is at first free-living, protects it by 

 inserting it within the coiled shell of some gastropod. The 

 alxlomen becomes nns3'mmetrical, l)eing coiled to one side 

 to correspond with the shape of the borrowed house (Fig. 133). 

 The abdominal feet become degenerate, mth the exception of 



Fig. 133.- 



- Buj^agurus longicarpus. Two individuals in sliclls. Photo, wiiile 

 alive l3y W. H. G. P. 



the posterior pair, which are each modified into a sort of hook, 

 by means of which the crab maintains itself securely in the 

 shell. When one shell becomes too small, it is abandoned for 

 a larger one. Numerous species of hermit-crabs occur on our 

 coast, ranging from the shore line to a depth of several himdred 

 fathoms. EuqMgurus longicarpus is the active little hermit 

 found in almost any tide-pool from Massachusetts Bay to the 

 Gulf of Mexico. Hj'droids, poly[3S, sponges, often attach 

 themselves to these borrowed shells (Fig. 133) ; indeed, one 

 Chinese species always bears an anemone on its large claw, 

 with which it plugs up the aperture when obliged to retreat 

 within its shell. One of the East Indian hermit-crabs, the 



