[3] Provided that the blue classification was based on the adult plumage and not on down color.
[4] If the recessive mutation occurs first in the Z chromosome of an egg of the female it will not appear in the next generation; then if it has passed into a male, half his daughters will show it. The single factor-pair involved is carried by the sex chromosomes ZZ.
[5] One may be either sex-linked or sex-limited so far as the evidence goes.
[6] No mention is made by Baur that a heterozygous male instead of a pure silver male was used, although the male is made heterozygous in the formulæ.
[7] For activity and pugnacity in hummingbirds, see Tropical Nature, pp. 130, 213.
[8] The Naturalist in La Plata, W. H. Hudson, London, 1892, pp. 269-270.
[9] Proceedings of the Zoological Society of London, 1885, p. 431, Quelques remarques sur le dimorphisme sexuel. Jean Stolzmann.
[10] George W. and Elizabeth G. Peckham. Observations on Sexual Selection in Spiders of the Family Attidæ. Nat. Hist. Soc. of Wisconsin, Vol. I, 1889, pp, 46, 47.
[11] Loddigesia mirabilis has the tail about three times as long as the body. Similar modifications are found in the genera Sappho, Cynanthus, Lesbia, Stegnura, Discura, Gouldia, et al.
[12] Among the most remarkable of this wonderful family are the nine species of coquettes (Lophornis), which have elongated feathers, with metallic tips, springing from the sides of the neck; some have also beautiful crests. (George W. and Elizabeth G. Peckham, Additional Observations on Sexual Selection in Spiders of the Family Attidæ, Nat. Hist. Soc. of Wisconsin, 1889, vol. I, pp. 141, 142.)