instance, a few red feathers appearing on the head of a male bird, and
which are at first transmitted to both sexes, would come to be transmitted
to males alone. It is not enough that females should be produced from the
males with red feathers, which should be destitute of red feathers; but
these females must have a latent tendency to produce such feathers,
otherwise they would cause deterioration in the red head-feathers of their
male offspring. Such latent tendency would be shown by their producing the
red feathers when old, or diseased in their ovaria. But I have no
difficulty in making the whole head red if the few red feathers in the male
from the first tended to be sexually transmitted. I am quite willing to
admit that the female may have been modified, either at the same time or
subsequently, for protection by the accumulation of variations limited in
their transmission to the female sex. I owe to your writings the
consideration of this latter point. But I cannot yet persuade myself that
females alone have often been modified for protection. Should you grudge
the trouble briefly to tell me, whether you believe that the plainer head
and less bright colours of female chaffinch, the less red on the head and
less clean colours of female goldfinch, the much less red on the breast of
the female bullfinch, the paler crest of golden-crested wren, etc., have
been acquired by them for protection? I cannot think so, any more than I
can that the considerable differences between female and male
house-sparrow, or much greater brightness of male Parus caeruleus (both of
which build under cover) than of female Parus, are related to protection.
I even misdoubt much whether the less blackness of female blackbird is for
protection.

Again, can you give me reasons for believing that the moderate differences
between the female pheasant, the female Gallus bankiva, the female of black
grouse, the pea-hen, the female partridge, have all special references to
protection under slightly different conditions? I, of course, admit that