The descent of man, and selection in relation to sex . and the surrounding coloured Fig. 54. Part of a tail-covert of Poly-plectron chinquis, with the two ocelliof nat. size. zones are likewise indented. A single ocellus is thus formed on each tail-covert, though still plainly betraying its double orioin. These con- fluent ocelli differ from the single ocelli of the peacock in having an indentation at both ends, instead of at the lower or basal end alone. The explanation, however, of this difference is not difficult; in some species of Polyplectron the two oval ocelli on the same feather stand
The descent of man, and selection in relation to sex . and the surrounding coloured Fig. 54. Part of a tail-covert of Poly-plectron chinquis, with the two ocelliof nat. size. zones are likewise indented. A single ocellus is thus formed on each tail-covert, though still plainly betraying its double orioin. These con- fluent ocelli differ from the single ocelli of the peacock in having an indentation at both ends, instead of at the lower or basal end alone. The explanation, however, of this difference is not difficult; in some species of Polyplectron the two oval ocelli on the same feather stand parallel to each other; in other species (as in P. cliinquis) they converge towards one end; now the partial confluence of two convergent ocelli would manifestly leave a much. Fig. 55. Part of a tail-covert of Poly-plectron malaccense, with tlie twoocelli, partially confluent, of nat. size. 140 SEXUAL SELECTION : BIRDS. Part IL deeper indentation at the divergent than at tlie con-vergent end. It is also manifest that if the convergencewere strongly pronounced and the confluence complete,the indentation at the convergent end would tend to bequite obliterated. The tail-feathers in both sj)ecies of peacock are en-tirely destitute of ocelli, and this apparently is relatedto their being covered up and concealed by the longtail-coverts. In this respect they differ remarkably fromthe tail-feathers of Polyplectron, which in most of thespecies are ornamented with larger ocelli than those onthe tail-coverts. Hence I was led carefully to examinethe tail-feathers of the several species of Polyplectronin order to discover whether the ocelli in any of themshewed any tendency to disappear, and, to my greatsatisfaction, I was successful. The central tail-feathersof P. Na^o
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Keywords: ., boo, bookcentury1800, bookdecade1870, booksubjectnaturalselection
