26 INHERITANCE. Chap. XIII. 



characters lying latent. The most obvious illustration is 

 afforded by secondary sexual characters. In every female all 

 the secondary male characters, and in every male all the 

 secondary female characters, apparently exist in a latent 

 state, ready to be evolved under certain conditions. It is 

 well known that a large number of female birds, such as 

 fowls, various pheasants, partridges, peahens, ducks, &c, 

 when old or diseased, or when operated on, assume many or 

 all of the secondary male characters of their species. In 

 the case of the hen-pheasant this has been observed to occur 

 far more frequently during certain years than during others. 54 

 A duck ten years old has been known to assume both the 

 perfect winter and summer plumage of the drake. 55 Water- 

 ton 56 gives a curious case of a hen which had ceased laying, 

 and had assumed the plumage, voice, spurs, and warlike 

 disposition of the cock ; when opposed to an enemy she would 

 erect her hackles and show fight. Thus every character, even 

 to the instinct and manner of fighting, must have lain 

 dormant in this hen as long as her ovaria continued to act. 

 The females of two kinds of deer, when old, have been known 

 to acquire horns ; and, as Hunter has remarked, we see some- 

 thing of an analogous nature in the human species. 



On the other hand, with male animals, it is notorious that 

 the secondary sexual characters are more or less completely 

 Lob • when they are subjected to castration. Thus, if the 

 operation be performed on a young cock, he never, as Yarrell 

 . crows again ; the comb, wattles, and spurs do not grow 

 to their full size, and the hackles assume an intermediate 

 appearance between true hackles and the feathers of the hen. 

 Cases are recorded of confinement, which often affects the 

 reproductive system, causing analogous results. But cha- 



54 Yarrell, 'Phil. Transact.,' 1827, Isidore Geoffroy Saiot-Hilaire. in his 



J; Dr. Hamilton, in ' Proc. ' Essais de Zoolog. Gen.' ('suites a. 



I - ..' 1862, p. . Button,' 1842, pp. 496-513), has 



55 • Archiv. Skand. Beit rage zur collected such cases in ten different 

 Naturgesch.' viii. s. 397-413. kinds of birds. It appears that 



50 In his 'Essays on Nat. Hist..' Aristotle was well aware of the 



Mr. Hewitt gives analogous change in mental disposition in old 



th hen-pheasants in ' Journal hens. The case of the female deer 



Di Horticulture, July 12, 18-34, p. 37. acquiring horns is given at p. 513. 



