how often I have
rewritten some pages you would know how anxious I am to arrive as near
as I can to the truth. I lay great stress on what I know takes place
under domestication; I think we start with different fundamental
notions on inheritance. I find it is most difficult, but not, I think,
impossible to see how, for 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 they are all protected by dull colours, derived,
as I think, from some dull-ground progenitor;