EUPAGURUS. 509 



caustic potash or soda till the skeleton is clean. It may- 

 then be washed and transferred to alcohol. 

 Integument. 



The structure of the integument of the Hermit Crab 

 does not differ in any respect but degree of calcification 

 from that usually found in the Crabs and Lobsters. 

 Only the chelae and the first two walking legs are 

 comparable with the calcified portions of a Crab in 

 hardness. The rest of the body is covered by a mem- 

 branous investment with slight deposits of lime in certain 

 places. 



The essential structure of the integument is as 

 follows : — * 



1. A chitinous exoskeleton, which may be shown to 

 consist of four layers. 



(a) The cuticle, a thin, structureless layer. 



(6) The pigmented layer, fine lamellae parallel 



to the surface, between which the pigment 



lies. 



(c) The calcified layer makes up the greater part 



of the hard exoskeleton. It is laminated, 

 but more coarsely than the previous layer. 



(d) A thin, non-calcified layer. 



2. The epidermis, which secretes or forms the 

 chitinous layer, and is a single layer of columnar cells. 



3. A connective tissue or dermis, in which are 

 imbedded numerous rosette glands, whose ducts pass 

 through the outer layers to the exterior, blood vessels, 

 muscle fibres and scattered cells. 



During ecdysis the Hermit Crab follows the same 



method as that of the Macrura, withdrawing the body 



first, then the limbs, and lastly the abdomen from the 



cast-off exoskeleton. 



* Vitzou. Recherches sur la structure des teguments. Arch, 

 de Zool. exper. et gen., T. X. (1882), p. 451. 



