Now, supposing, on your view, that the colours of a male bird become more
and more brilliant by sexual selection, and a good deal of that colour is
transmitted to the female till it becomes positively injurious to her
during incubation, and the race is in danger of extinction; do you not
think that all the females who had acquired less of the male's bright
colours, or who themselves varied in a protective direction, would be
preserved, and that thus a good protective colouring would soon be
acquired?

If you admit that this could occur, and can show no good reason why it
should not often occur, then we no longer differ, for this is the main
point of my view.

Have you ever thought of the red wax-tips of the Bombycilla beautifully
imitating the red fructification of lichens used in the nest, and therefore
the FEMALES have it too? Yet this is a very sexual-looking character.

If sexes have been differentiated entirely by sexual selection the females
can have no relation to environment. But in groups when both sexes require
protection during feeding or repose, as snipes, woodcock, ptarmigan, desert
birds and animals, green forest birds, etc., arctic birds of prey, and
animals, then both sexes are modified for protection. Why should that
power entirely cease to act when sexual differentiation exists and when the
female requires protection, and why should the colour of so many FEMALE
BIRDS seem to be protective, if it has not been made protective by
selection.

It is contrary to the principles of "Origin of Species," that colour should
have been produced in both sexes by sexual selection and never have been