74 THE GENETIC AND THE OPERATIVE EVIDENCE 



species, such as the doves and pigeons, in which the plumage of the 

 male is much like that of the female, but this is the exception rather 

 than the rule. At the other extreme are species like birds of paradise, 

 hummingbirds, fowls, pheasants, ducks, and many passerines, in 

 which the plumage of the two sexes is entirely different. Our knowledge 

 as to the relation between the nuptial plumage of the male and the 

 condition of the sex-organs rests largely on information gained by 

 castration in poultry and ducks and on the assumption of the nuptial 

 plumage in several species only at the mating season. 



John Hunter in 1780 described a pheasant with male plumage. His 

 account of a similar change in a pea fowl is so complete that I venture 

 to quote it in full: 



"Lady Tynte had a favorite pyed pea-hen, which had produced chickens 

 eight several times; having moulted when she was about eleven years old, she 

 astonished the lady and her family by showing the feathers peculiar to the 

 other sex, and appearing like a pyed peacock. In this process the tail, which 

 was similar to that of a cock, first appeared after moulting. In the following 

 year she moulted again, and produced the same feathers. In the third year 

 she did the same; at the same time she had spurs similar to those of a cock. 

 She died in the following winter during the hard frost, namely, in the winter 

 1775-6. She never bred after this change in her plumage. This bird is now 

 preserved in the Museum of Sir Ashton Lever." l 



"From what has been related of these two birds, may it not reasonably be 

 inferred that it seems probable that all those wild pheasants of the female sex, 

 which are found with the feathers of the cock, had changed the nature of their 

 feathers, particularly at a certain age? 



" If this idea be just, it shews that there is a disposition in the female to come 

 nearer and nearer to the male, at least in the secondary properties; or it may 

 rather be said that the female is later in producing this change than the male is; 

 for it has already been observed that both sexes when young differ not from 

 each other in these respects, but that the male appears to be the one that by 

 degrees separates from the female in its secondary properties." 



Statements in regard to the effect of castration on poultry go back, 

 it appears, to Aristotle. Yarrel in 1811 and again in 1850 has given an 

 excellent account of many of the effects produced. His account of the 

 effects on the cock seem to be based partly on hearsay, and while they 

 contain much accurate information, yet the statement that the 

 plumage of the capon is intermediate between that of the cock and hen 

 is incorrect. The further statement that by cutting the oviduct the 

 hen assumes the plumage of the capon has been shown by Sellheim to 

 be erroneous. The operation referred to by Yarrel must have been 

 one in which the ovary was removed. 



1 It might be supposed that this bird was really a cock which had been changed for a hen; but 

 the following facts put this matter beyond a doubt: First, there was no other pyed pea-fowl in 

 the country. Secondly, the hen had knobs on her toes, which were the same after her change. 

 Thirdly, she was as small after the change as before, therefore too small for a cock. Fourthly, she 

 was a favorite bird, and was generally fed by the lady, and used to come for her meat, which 

 she still continued to do after the change in the feathers. 



