. The descent of man, and selection in relation to sex. Evolution; Heredity; Human beings; Natural selection. CHAP. BTRDS—GRADATION OF CHARACTERS. 453. the ocelli on all the feathers differed fundamentally from those of the peacock, in there being two on the same feather (fig. 55), one on each side of the shaft. Hence I concluded that the early progenitors of the pea- cock could not have resembled a Polyplectron. But on con- tinuing my search, I observed that in some of the species the two ocelli stood very near each other ; that in the tail-feathers of P. hardwickii they touched each ot
. The descent of man, and selection in relation to sex. Evolution; Heredity; Human beings; Natural selection. CHAP. BTRDS—GRADATION OF CHARACTERS. 453. the ocelli on all the feathers differed fundamentally from those of the peacock, in there being two on the same feather (fig. 55), one on each side of the shaft. Hence I concluded that the early progenitors of the pea- cock could not have resembled a Polyplectron. But on con- tinuing my search, I observed that in some of the species the two ocelli stood very near each other ; that in the tail-feathers of P. hardwickii they touched each other; and, finally, that on the tail-coverts of this same spe- cies as well as of P. malaccense (fig. 56) they were actually con- fluent. As the central part alone is confluent, an indentation is left at both the upper and lower ends; and the surrounding colored zones are likewise in- dented. A single ocellus is thus formed on each tail-covert, though still plainly betraying its double origin. These con- fluent ocelli differ from the sin- gle ocelli of the peacock in hav- ing an indentation at both ends, instead of only at the lower or basal end. 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. chi7iquis) they converge toward one end ; now the partial confluence of two convergent ocelli would manifestly leave a much deeper indentation at the divergent than at the convergent end. It is also manifest that if the con* irer|;cnce wei:e gjtron^ly pronounced m^ ItJie a)D^ueace cxm^ FfG. 55.—Part of a tail-covert of Pol plectron chinquis, with the two oce of natural size. :t>. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Darwin, Charles, 1809-1882. New York Hurst
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Keywords: ., bookcentury1800, bookdecade1870, booksubjecthumanbeings, bookyear
