. The descent of man : and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings. BIRDS—GRADATION OF CHARACTERS. 429 become confluent, either in the line of the row—and then they form a longitudinal stripe—or transversely, that is, with the spots in the adjoining rows, and then they form transverse stripes. A spot sometimes breaks up into smaller spots, which still stand in their proper places. It will be convenient first to describe a perfect ball- and-socket ocellus. This consists of an intensely black circular ring, sur- rounding a space shaded so as exactly to
. The descent of man : and selection in relation to sex. Evolution; Natural selection; Heredity; Human beings. BIRDS—GRADATION OF CHARACTERS. 429 become confluent, either in the line of the row—and then they form a longitudinal stripe—or transversely, that is, with the spots in the adjoining rows, and then they form transverse stripes. A spot sometimes breaks up into smaller spots, which still stand in their proper places. It will be convenient first to describe a perfect ball- and-socket ocellus. This consists of an intensely black circular ring, sur- rounding a space shaded so as exactly to resemble a ball. The figure here given has been admirably drawn by Mr. Ford and well en- graved, but a woodcut can- not exhibit the exquisite shading of the original. The ring is almost always slightly broken or inter- rupted (see fig. 57) at a point in the upper half, a little to the right of, and above the white shade on the enclosed ball; it is also sometimes broken towards the base on the right hand. These little breaks have an important meaning. The ring is always much thick- ened, with the edges ill-de- fined towards the left-hand upper corner, the feather being held erect, in the po- sition in which it is here drawn. Beneath this thick- ened part there is on the surface of the ball an oblique almost pure-white mark, which shades off downwards into a pale- leaden hue, and this into yellowish and brown tints, which insensibly become darker and darker towards the lower part of the ball. It is this shading which gives so admirably the effect of light shining on a convex surface. If one of the balls be examined, it will be seen that the lower part is of a brown tint and is indistinctly sepa-. Fig-. 57. Part of secondary wing-feath- er of Arg-us pheasant, showing two perfect ocelli, a and b. A, B, C, D, &c., are dark stripes running- ob- liquely down, each to an ocellus. [Much of the web on both sides, es- specially to the left of the shaft, has been cut off.]. Pleas
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Keywords: ., bookcentury1800, bookdecade1870, booksubjecthumanbeings, bookyear
