ocr: a b Fig- 61 Portion near summit of one of the secondary wing-feathers, bearing perfect ball-and-socket ocelli. a- Ornamented upper part. b. Uppermost, imperfect ball-and-socket ocellus. CThe shading above the white mark on the summit of - the ocellus is here a little too dark.) - - C. Perfect ocellus. DARWIN: DESCENT OF MAN