Secondary Sexual Characters 435 
as to make it doubtful if the development of horns was due to 
this defect. Cases of this sort are not of much value, since it is 
possible that the abnormalities observed may both be due to 
some abnormal condition of the whole and are not connected 
as cause and effect. 
The best-known cases in which the castrated female assumes 
the characters of the male are found in poultry. Many in- 
stances of this sort have been recorded.’ It has also been 
observed that when female birds, such as pheasants, fowls, par- 
tridges, peacocks, and ducks, become old, they may assume the 
secondary sexual characters of the male. Darwin cites the case 
of a duck ten years old that assumed the perfect winter and sum- 
mer plumage of the drake. Waterton gives the case of a hen 
that had ceased laying and had assumed the plumage, spurs, 
voice, and disposition of the cock. This evidence points clearly 
to the possibility of the castrated female assuming the charac- 
ters of the male. Whether the converse is true for the male is, 
as we have seen, more doubtful, but the possibility of its being 
true must be admitted. 
If the characters of the female are latent in the male, and those 
of the male are latent in the female, as these and other facts seem 
to show, the experiments with castration have an interesting 
bearing on sex determination; for if, as seems probable, the 
male characters may develop in a castrated female despite the 
fact that the female characters had already been developed, 
it shows that the question of sex determination, even if deter- 
mined in the egg, or even in the embryo, is not final and the con- 
verse change may occur even ata late stage. If it should prove 
true that in the vertebrates the castrated female develops male 
characters, but the castrated male does not develop female char- 
acters, but simply remains at a lower stage of development, we 
might perhaps assume that the male condition in this group 
is a further stage of the female condition. Internal or external 
factors may determine whether the egg or embryo remains at a 
given stage or undergoes a further change. If the former, a 
1 Darwin, “Animals and Plants,” Chap. XIII. 
