Morphology of the ypsigon stage (Crustacea Facetotecta). (A) Horizontal transmission electron microscopy section through the ypsigon shown in Figure 1C. Collage of multiple frames. (B) Two high-magnification frames from A. The epidermis is clearly overlain by an ultrathin cuticle. (C) Light microscopy. Lateral view of a molting ypsigon, 48 hours after escape from the y-cyprid. (D) Light microscopy. Lateral view of the specimen in C, but 4 hours later. The first ypsigon cuticle, laid down while still within the y-cyprid, is now being shed and replaced by the new one. The interior structure of the ypsigon does not change noticeably during the molt.