Crabs, Lobstt-rs, Shrimps, Barnacl- 



71 



A whelk-shell walking about on crab's legs and carrying sea-anemo- 

 nes on its back such is the impression made on anyone looking for 

 the first time at a Hermit-crab (tank Xr. 23). This droll figure fasci- 

 nates us at once and creates in us a desire to know something more 

 about it. The problem is simpler than it seems, and has the following 

 explanation. The Hermit-crabs live in deserted whelk-shells. When they 



Fig. 164. Pagurus striatus, 1 , r 2 "nat. size. 



Fig. 163. Pagurus striatus, in a whelk-shell and 

 bearing three Anemones, */2 nat. size. 



Fig. 165. Eupagurus Prideauxii, in 



a shell and bearing the Anemone 



Adamsia palliata, l /2 nat. size. 



escape from the egg they are just like the young long- tailed prawns; 

 but very soon their previously straight tail begins to twist itself spirally, 

 and the time has corne for the small animal, which is scarcely half an 

 inch long, to look out for a shell. If it finds an empty one suitable for its 

 size, it puts its tail into it; but if it does not, it first eats out the whelk 

 and then takes possession of the shell. In the course of many generations 

 the hind portion of the body has become so accustomed to a borrowed 

 covering, that it is quite soft, and resembles an unjointed sack (Fig. 164) 

 possessing at its extremity a pair of rudimentary legs; with these it holds 

 so fast to the shell, that in trying to extricate the animal you may very 

 often tear it to pieces. The shell thus serves as a protection and is 

 usually so large, that the Hermit-crab can withdraw itself entirely from 

 view in case of danger. As it grows, mast from time to time change its 

 dwelling, when the latter becomes too small: and this it does with great 

 circumspection. When it has found a shell suitable for its purpose, it first 

 examines it carefully all over, poking its claws far into the cavity so as 

 to make sure that there is nothing suspicious lurking within it: then, if 



