PAGURIDEA EVOLUTION OF HERMIT-CRABS 



179 



hard plates, and re-aoquiring, to a greater or less degree, a 

 secondary symmetry of form. But the story of Pagurid evolu- 

 tion does not apparently stop here. The genus Paralomis, from 

 the West Coast of America, superficially resembles Forcellana, and 

 is held to be descended from such forms as Pyloclieles, while isolated 



Fig. 123. — Four stages in the development ot Eupagurus loncjicarpus or E. annuUpes, x 

 20. A, Ventral view of Zoaea ; B, lateral view of Metazoaea ; C, dorsal view of Glau- 

 cothoe ; D, dorsal view of adolescent stage. Ab.6, 6th abdominal appendage ; 

 Mxp.l, Mxp.S, 1st and 3rd maxillipedes. (After M. T. Thompson.) 



species are known (though not well known), such as l\jlaspis, 

 described in the ChalUng&r Reports} which appear to be 

 Pagurids that have deserted their shells. 



The metamorphosis of the Hermit-crabs has recently been 

 studied by M. T. Thompson.^ 



The Zoaea (Fig. 123, A) differs from that of the Galatheidea 

 mainly in the absence of the long spines. It possesses the usual 



1 Vol. xxvii. p. 81. ^ Proo. Boston Soc. Nat. His'., xxxi., 1904, p. 147. 



