34 



GONADECTOMT IN RELATION TO THE SECONDARY 



TWO TYPES OF FEMALES RESULTING FROM OVARIOTOMY. 



In the course of the work it has been necessary to use both pure-bred 

 and cross-bred female birds. Curiously, in the case of the ducks, the 

 cross-breds after the operation have developed a more perfect resem- 

 blance to the male's plumage than the pure-bred. Not one of the lat- 

 ter (five in number)^ has produced a bird that did more than develop 

 male plumage to a certain degree, while the plumage of the least perfect 

 of the cross-breds approximates that of the male more closely than the 

 most perfect of the pure-breds. The results with the pure-breds are 

 not due to imperfect castration, for this type of plumage is maintained 

 for years, in one instance for nearly 6 years. Moreover, at autopsy the 

 birds have been found free of any ovarian tissue. During the second 

 winter the plumage is frequently more male-Uke than during the first 

 winter. Two of the pullets also failed to develop a perfect coat of male 

 feathers, though they were the ones that developed the comb and wattles 



Table 4. — Comparison of the two types of female ducks resulting from ovariotomy. 



which most perfectly resembled those of the male. They also were pure- 

 bred. Many of the cross-bred ducks, however, failed to develop into quite 

 as good replicas of the male as No. 169. A few feathers in certain parts 

 of the body retain a resemblance to the female, so that on the whole the 

 demarcation between the two groups is not altogether clear-cut, though 

 there is little difficulty in placing an individual in the proper class. 

 The difference between the two types is shown in table 4. The word 

 "drake" or "duck" is used to indicate that the character in question 

 is Uke that of the male or female respectively. 



If we survey the cases in which the male plumage is the more imper- 

 fectly developed, it appears that those regions which in the males 

 become most like the females during the summer molt are the same 

 regions that, in the castrated females, tend most strongly to retain female 

 characters. These regions are the head and ventral surface, especially 



'Two non-pedigreed females, probably but not certainly pure-bred, castrated in 1914, belong 

 to this class. 



