FIG. 56.--Astacus fluviatilis.--The structure of the cuticle. A, transverse section of a joint of the forceps ( x 4); s, setae; B, a portion of the same ( x 30); C, a portion of B more highly magnified. a, epiostracum; b, 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; a, intermediate substance; b, laminae. F, a seta, highly magnified; a and b, joints.
[Editor's note: illustration is reproduced here approximately twice the size of the woodcut in the book.]
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