RESULTS OF CASTRATION IN DUCKS. 55 



but with both sexes patent. On the other hand maleness and 

 femaleness may each exist in the same individual in a homozy- 

 gous condition, which may be expressed in MendeHan form, thus: 



forming gametes all ^- This formula may represent only 



the primitive hermaphrodite, other formulae serving for existing 

 forms. 



Summary. 



1. The castrated drake retains his secondary sexual characters, 

 except the ability to assume the summer plumage. 



2. The castrated duck (female) assumes, more or less com- 

 pletely, the secondary sexual characters of the drake. The 

 change, however, is very gradual. 



3. It is suggested that the female owes her color to the presence 

 of some modifying element, which prevents the development of 

 the male color. It is also suggested that the modifier may 

 sometimes be responsible for sex limited inheritance. 



4. Cases in which the patency of sex has changed are pointed 

 out. This suggests that a common basis for the present contra- 

 dictory evidences regarding the determination of sex may be 

 found in the hermaphroditic condition. 



LITERATURE. 

 Bateson. 



'09 Mendel's Principles of Heredity. Cambridge, 1909. 

 Bleringhem. 



'07 Action des traumatismes sur la variation et I'heredite. Lille, 1907. 

 Braem. 



'08 Uber die Aenderung des Geschlects bei Ophryotrocha. Anat. Anz., Bd. 33, 

 1908. 

 Correns. 



'07 Bestimmung und Vererbung des Geschlechtes. Leipzig, 1907. 

 Coues. 



'96 Key to North American Birds, 1896. 

 Darwin. 



Animals and Plants under Domestication, Vol. IT. 

 Davenport. 



'06 Inheritance in Poultry. Carnegie Inst. Washington, 1906. 

 Doncaster and Raynor. 



06 Breeding Experiments with Lepidoptera. Proc. Roy. Soc, 1906. 

 Goodale. 



'10 Breeding Experiments in Poultry. Proc. Soc. Exp. Biol. Med., Vol. 7, 1910. 

 Guyer. 



'09 Spermatogenesis of the Domestic (liickcn. Anat. Anz., Bd. 34, 1909. 



