to eclipse takes place between the beginning of June and the middle of
July. The reappearance of the nuptial plumage takes place in the month of
September, and while this process takes place there is no sign of change
or renewed activity in the testes. During October and November, when the
brilliant plumage is fully developed, the testes increase slowly in size
but remain yellow and firm and exude no liquid on incision.
Spermatogenesis does not commence until the end of November or beginning
of December. The testes increase greatly in size in January and February,
and again reach their maximum size by the end of March. It is shown,
therefore, that the loss of the nuptial plumage takes place in June when
spermatogenesis has ceased and the testes are diminishing in size, but the
redevelopment of this plumage takes place in September without any renewed
activity of the testis and long before the beginning of spermatogenesis.
The case of the antlers in the stag is probably very similar.

The important statement is made with regard to castration (under
anaesthetics, of course) that it was found impossible to extirpate the
testes completely. When the bird was killed some months after the
operation, a greater or lesser amount of regenerated testicular tissue was
found either on the original site of the organs or engrafted upon
neighbouring organs. This experience, it will be noted, agrees with my own
in the case of fowls. There were, however, reasons for believing that the
results observed within the first six or eight months after the operation
are not much different from those which would follow complete castration.

Castration carried out when the drake was in nuptial plumage produced the
same effect which was observed by Goodale, namely, delay, and imperfection
in the assumption of the eclipse condition, but the observations of
Seligmann and Shattock are more precise and detailed. One example
described was castrated in full winter plumage in December 1906. On July