Crabs, Lobsters, Shrimps, Barnacles, etc. 



71 



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

 mones on its back — such is the impression made on anyone looking- 

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

 fascinates 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 



Fig. 165. Pagurus striatus, '/a nat. size. 



Fig. 1G4. Pagurus striatus, in a whelk-shell and 

 bearing three Anemones, '/s nat. size. 



Fig. 106. Eujjagurus Prideauxii, in 



a shell and bearing the Anemone 



Adamsia paUiata, '/a nat. size. 



they escape from the egg- tliey are just like the young- loug--taik'd prawns; 

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

 and the tiine has come for the small animal, which is scarcely half an 

 indi 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 

 tlie wlielk aiid 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. 165) possessing at its extremity a pair of rudimentary legs ; 

 with these it holds so fast to the shell, tliat in trying- to extricate the 

 auiiiial you may very often tear it to pieces. The shell thus serves as 

 a protection and is usually so large, that the Hermit-crab eau witlidraw 

 itself entirely from view in case of danger. As it grows, it must from 

 time to time cliange its dwelling, when tlie latter becomes too small ; 

 and this it does with great circumspection. Wlien it has found a shell 

 suitable for its purpose, it first examines it carefully all over, poking 

 its claws far into the cavitv so as to make sure that there is nothing 



