. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. Chap. XIV. Birds—Gradation of Characters. 439. in the most perfect ocelli, traces of the junction of three or foni elongated black marks, by which the ring has been formed, may often be detected. The irregular sub-triangular or narrow mark (d fig. 59), manifestly forms, by its contraction and equalisation, the thickened portion of the ring above the white shade on a perfect ball- and-socket ocellus. The lower part of the ring is invariably a little thicker than the other part
. The descent of man, and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings -- Origin. Chap. XIV. Birds—Gradation of Characters. 439. in the most perfect ocelli, traces of the junction of three or foni elongated black marks, by which the ring has been formed, may often be detected. The irregular sub-triangular or narrow mark (d fig. 59), manifestly forms, by its contraction and equalisation, the thickened portion of the ring above the white shade on a perfect ball- and-socket ocellus. The lower part of the ring is invariably a little thicker than the other parts (see fig. 57), and this follows from the lower black mark of the elliptic ornament (b fig. 59) having origi- nally been thicker than tbe upper mark (c). Every step can be fol- lowed in the process of confluence and modification; and the black ring which surrounds the ball of the ocellus is unquestionably formed by the union and modification of the three black marks, b, c, d, of the elliptic ornament. The irre- gular zigzag black marks between the successive ocelli (see again fig. 57) are plainly due to the breaking up of the somewhat more regular but similar'marks between the elliptic ornaments. The successive steps in the shading of the ball-and-socket ocelli can be followed out with equal clearness. The brown, orange, and pale leaden narrow zones, which border the lower black mark of the elliptic ornament, can be seen gradually to become more and more softened and shaded into each other, with the upper lighter part towards the left-hand corner ren- dered still lighter, so as to become almost white, and at the same time more contracted.* But even in the most perfect ball-and- socket ocelli a slight difference in the tints, though not in the shading, between the upper and lower parts of the ball can be perceived, as before noticed; and the line of separation is oblique, in the same direction as the bright-coloured shades of the elliptic ornaments. Thus almost every minute d
Size: 1204px × 2075px
Photo credit: © Paul Fearn / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., boo, bookcentury1800, bookdecade1880, booksubjectnaturalselection
