He states that the male in summer plumage merely mimics the female but
does not become entirely like her. In certain parts of the body there are
no modifications toward the female type. In others, i.e. head, breast, and
keel region, the feathers of the male become quite like those of the
female. 'It can hardly be maintained that this is an example of assumption
by the male of the female's plumage, especially as the presence of the
testis is necessary for its appearance.' The idea here seems to be that
since the eclipse plumage is only assumed when the testis is present,
therefore it must be a male character.

Out of five females on which the operation was performed only two lived
more than a few days afterwards. One of these (a) was castrated in the
spring of 1909 when a little less than a year old, the other (b) on August
13 when twelve weeks old. In October 1909 they showed no marked
modifications. In July 1910 it was noticed that they had the male curled
feathers in the tail, and (a) had breast feathers similar to those of the
male in summer plumage, (b) was rather more strongly modified: she had a
very narrow white neck-ring, and breast feathers distinctly of male type.
The next moult began in September, and in November was well advanced. On
the whole (a) had made little advance towards the male type, but (b)
closely resembled the male in nuptial plumage. It had brilliant green
feathers on the head, a white neck-ring, much claret colour on the breast,
and some feathers indistinguishable from those of the male, and also the
male sex feathers on the tail. Goodale concludes that the female owes her
normal colour to the ovaries or something associated with them which
suppresses the male characters and ensures the development of her own
type. He considers it is quite as conceivable that selection should
operate to pick out inconspicuously coloured females as that selection of
brilliantly coloured males should bring about an addition to the female
type. But as pointed out above, selection cannot explain the dimorphism in