Archive image from page 446 of The descent of man . The descent of man : and selection in relation to sex descentofmanseledarw Year: 1874 BIRDS—GRADATION OF CHARACTERS. 433 (d. fig. 59), manifestly forms, by its contraction and equalization, the thickened portion of the ring above the white shade on a per- fect ball-and-socket ocellus. The lower part of the ring is invari- ably 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 originally been thicker than the upper mark (c). Every step can be followed
Archive image from page 446 of The descent of man . The descent of man : and selection in relation to sex descentofmanseledarw Year: 1874 BIRDS—GRADATION OF CHARACTERS. 433 (d. fig. 59), manifestly forms, by its contraction and equalization, the thickened portion of the ring above the white shade on a per- fect ball-and-socket ocellus. The lower part of the ring is invari- ably 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 originally been thicker than the upper mark (c). Every step can be followed in the process of conflu- ence and modification; and the black ring which surrounds the ball of the ocellus is unquestionably formed by the union and modifica- tion of the three black marks, b, c, d, of the elliptic ornament. The irregular zigzag black marks be- tween the successive ocelli (see again fig. 57) are plainly due to the breaking up of the somewhat mora regular but similar marks between the elliptic ornaments. The successive steps in the shad- ing of the ball-and-socket ocelli can be followed out with equal clear- ness. 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 rendered 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, be- tween 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-colored shades of the elliptic orna- ments. Thus almost every minute detail in the shape and color- ing of the ball-and-socket ocelli can be shown to follow from gradual changes in the elliptic ornaments; and the development of the latter can be
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