Molting in a Scorpion. I. Changes in the Newly Molted Cuticle of Palamnaeus bengalensis1

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Abstract
Immediately after ecdysis the cuticle was soft, transparent, and untanned. It then consisted of a greenish-yellow epicuticular layer, rugose on its outer surface, and a presumptive exocuticle in the mesocuticular condition. The chemical constitution of the epicuticle remains to be determined. It was negative to chitin tests and positive to Sudan dyes, and was resistant to both acids and hot alkali. The presumptive exocuticle stained red with Mallory's stain and was positive for p-phenols and polyphenol oxidase. As tanning proceeded, the surface of the epicuticle became smooth and the layer differentiated into outer and inner zones, demonstrable by differential intensity of Sudan staining. At the same time when tanning of the presumptive exocuticle began, mesocuticle was secreted under it, and procuticle was secreted beneath this. Full tanning required several months and resulted in an inter-molt cuticle with dark brown exocuticle underlaid by mesocuticle. The mesocuticle itself sometimes became lightly sclerotized. Both exocuticle and mesocuticle were of the usual laminar organization. At the time of ecdysis the epidermal cells were very tall. Their height, however, decreased by more than nine-tenths, in inverse ratio to increasing thickness of the cuticle as the latter was secreted. Thus the thickness of the entire integument remained approximately the same at all times. Pore canals containing cytoplasmic projections from epidermal cells were present in the cuticle. At muscle insertions, muscle fibers passed between epidermal cells and sometimes came to displace them. The hemolymph contained granulocytes which showed changes suggesting that they might be involved in the molting process.

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