146 NATURAL HISTORY OF OUR SHORES 



termination of the tail (or telson) is jointed, across and in 

 median line, which is not usual in ordinary crustaceans. 



(I must ask my reader to bear in mind these little details.) 



When first the hermit crab develops from the egg it is 

 bilaterally symmetrical, like a little shrimp ; in fact, it is a 

 little Macruran, and it swims freely at the sea surface. 

 Then, when about a quarter of an inch in length, it seeks a 

 shelter, and generally finds one in the cast skin (or " shell ") 

 of some small crustacean. (I usually find it inserting its 

 abdomen into the broken cast shell of some amphipod, 

 which, by its lightness, is floating on the sea.) 



Soon it sinks to bottom, and seeks some little univalve 

 shell, at first a diminutive one. (This day I have found one 

 in a Rissoa, a microscopic shell.) When it has grown too 

 big for this habitation it seeks a larger one, and is frequent 

 in the common " Periwinkle." Finally the shell of the 

 whelk alone will suit it. 



Possibly this is what has fixed its size limit : we having 

 no larger univalve shells in sufficient number to furnish 

 tenements for the great number of applicants, and a 

 shell-less hermit crab, unless he has some little advantage 

 in being tougher than his mates, or has some plan of tucking 

 his tender abdomen into security, must perish. 



The two pairs of legs which serve for locomotion (two 

 pairs are out of use within the shell) are very largely de- 

 veloped, through their increased use in having to drag 

 about a borrowed shell, and usually an additional burden 

 in the way of an anemone (see Chapter III.). 



The hermit crabs are very pugnacious that is why they 

 are sometimes called " Soldier Crabs " and fight tremend- 

 ously. The object of each one's contention being generally 

 the house of his neighbour ; and the efforts to pull each 

 other out of house and home is constant. 



When one has succeeded in evicting another he slips 

 at once from his own dwelling into the vacated one, the 



