ORGANS OF INTERNAL SECRETION 315 



Better instances of this kind of phenomenon have been 

 recorded from among poultry, game birds, and ducks, which, 

 on growing senile, have been observed to acquire some of 

 the secondary male characters. Darwin ^ refers to the case 

 of a duck which, whep ten years old, assumed the plumage of 

 the drake. He also mentions an instance of a hen which in old 

 age acquired the secondary sexual characters of the cock. 

 Hunter ^ described a case of a hen pheasant which had male 

 plumage correlated with an abnormal ovary, and many other 

 such instances have been recorded. Gurney ^ states that the 

 assumption of male plumage is frequently (but not invariably) 

 associated with barrenness in female galhnaceous birds but not 

 as a rule in passerine birds. The phenomenon has been observed 

 in black grouse, capercailUe, wild duck, widgeon, merganser, and 

 various other species belonging to different orders. On the 

 other hand, Gurney records instances of a hen chaffinch with 

 male plumage and an unlaid egg, a hen redstart with male 

 plumage and a number of developing eggs, as well as similar 

 cases of hen pheasants. The male plumage may be only tem- 

 porarily assumed. Further examples of the assumption of male 

 plumage by hen birds are recorded by Shattock and Seligmann,* 

 who describe the phenomenon under the name of allopterotism. 

 Some of these cases are regarded as of the nature of partial 

 hermaphroditism. It would appear possible that the secondary 

 male characters are normally latent in the female, and that the 

 ovaries exert an inhibitory influence over their development. On 



the male type (with well-developed tissues in tlie jowl, the exact converse 

 occurring in castrated males). Herbst, who also discusses this question 

 {Formative Beize in der Tieriachen Ontogenese, Leipzig, 1901), expresses the 

 belief that the gonads in either sex exercise a definite inhibitory influence, 

 preventing the appearance of the secondary sexual characters of the 

 opposite sex. 



^ Darwin, loc. cit. 



' Hunter, " Account of an Extraordinary Pheasant," Phil. Trans. , 

 vol. Ixx., 1780. 



' Gurney, " On the Occasional Assumption of Male Plumage by Female 

 Birds," Ibis, vol. vi., 5th series, 1888. 



* Shattock and Seligmann, " An Example of True Hermaphroditism in 

 the Common Fowl, with Remarks on the Phenomena of Allopterotism," 

 Trans. Path. Soc, vol. Ivii., 1906. "An Example of Incomplete Glandular 

 Hermaphroditism in the Domestic Fowl," Proc. Roy. Soc. Med., Path. Section 

 vol. i. (November), 1907. 



