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Pig. 56. — Astacwi fiweiatiUs. — The structure of the cuticle. A. trans- 

 verse section of a joint of the forceps ( x 4) ; s, setee ; £, a por- 

 tion of the same ( x 30) ; C, a portion of B more highly magnified. 

 a, epiostracum ; i, ectostracum ; c, endostracum ; d, canal of seta ; 

 e, canals filled with air ; s, seta. D, section of an intersternal 

 membrane of the abdomen, the portion to the right in the natural 

 condition, the remainder pulled apart with needles ( x 20) ; E, 

 small portion of the same, highly magnified ; o, intermediate sub- 

 stance ; 1), laminae. F, a seta, highly magnified ; a and b, joints. 



