PAGURIDEA SYMMETRICAL HERMIT-CRABS 



1/3 



Besides the ordinary twisted Pagurids which inhabit Gas- 

 teropod shells, there are a few which preserve the symmetry of 

 the body. The interesting fylocheles miersii 1 (Fig. 118), 

 tak'en by the Investigator in the Andaman Sea at 185 fathoms, 

 inhabits pieces of bamboo ; it is perfectly symmetrical, with 

 well -developed pleopods and 

 symmetrical chelae, which, 

 when the animal is withdrawn, 

 completely shut up the entrance 

 to its house (Fig. 118, A). 



It is doubtful whether this 

 animal ever inhabited a spiral 

 shell or not in its past history ; 

 but there is no doubt that 

 a number of peculiar crabs, 

 which caused the older sys- 

 tematists much trouble, are 

 Pagurids, derived from asym- 

 metrical shell - haunting an- 

 cestors that have secondarily 

 taken to a different mode of 

 life, and lost, or partially lost 

 those characteristics of ordinary 

 Hermit-crabs which are asso- 

 ciated with life in a spiral shell. 

 These are the Lithodidae and 

 the " Robber - crab," Birgus 

 latro, of tropical coral islands. FlG . us.pyiocheies miersii, x i. A. End 



Although the liobber-Crab view of a P iece of mangrove or bamboo, 



the opening of winch is closed by the 

 and the Lithodidae bear a great chelae (c) of the Pagurid ; B, the 



certain superficial resemblance < ITia 1 1 m<>\ fro.., its house. (After 



Alcock.) 



to one another in that they 



lead a free existence, and have reacquired to a great extent their 

 symmetry, yet it is clear that they have been independently 

 derived from different groups of asymmetrical Hermit-crabs, and 

 that their resemblance to one another is due to convergence. 



Birgus latro (Fig. 119), a gigantic crab, frequently over a 

 foot in length, lives on land, and inhabits the coasts of coral 

 islands in the Indian and Pacific Oceans where cocoa-nut trees 



1 Alcouk, loc. cit. ; Borradaile, op. cit. p. 162 ; i. r>. 64. 



