The Descent of Man

immature plumage approximately shews us the
former or ancestral condition of the species.
Although many young birds, belonging to various
families, thus give us a glimpse of the
plumage of their remote progenitors, yet there
are many other birds, both dull-coloured and
bright-coloured, in which the young closely
resemble their parents. In such cases the young
of the different species cannot resemble each
other more closely than do the parents; nor can
they strikingly resemble allied forms when
adult. They give us but little insight into the
plumage of their progenitors, excepting in so
far that, when the young and the old are coloured
in the same general manner throughout a
whole group of species, it is probable that their
progenitors were similarly coloured.
We may now consider the classes of cases, under
which the differences and resemblances
between the plumage of the young and the old,
in both sexes or in one sex alone, may be grou-