VI PAGURIDEA—EVOLUTION OF HERMIT-CRABS 179 
hard plates, and re-acquiring, 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 Porcellana, and 
is held to be descended from such forms as Pylocheles, while isolated 
Fic. 123.—-Four stages in the development of Lupagurus longicarpus or E. annulipes, x 
20. A, Ventral view of Zoaea ; B, lateral view of Metazoaea ; C, dorsal view of Glau- 
cothoe ; D, dorsal view of adolescent stage. Ad.6, 6th abdominal appendage ; 
Mep.1, Map.3, 1st and 3rd maxillipedes. (After M. ‘I. Thompson.) 
species are known (though not well known), such as 7y/aspis, 
described in the Challenger 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 
2 Wok sean Jopecille 2 Proc. Boston Soc. Nat. Hist., xxxi., 1904, p. 147, 
