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HH15 | (50-55 hours). 24-27 somites. Lateral body folds extend to anterior end of wing level (somites 15-17). Prospective limb areas not yet demarcated. Amnion extends to somites 7-14. Axes of forebrain and hindbrain nearly parallel. Trunk rotation extends to somites 11-13. Visceral arch 3 and cleft 3 distinct. Cleft 3 shorter than cleft 2 and usually oval shape. Optic cup completely formed; double contour distinct in region of iris. |