as known to me, may be included, it will be well to make a few
preliminary remarks.
With animals of all kinds when the adults differ in colour from the
young, and the colours of the latter are not, as far as we can see, of
any special service, they may generally be attributed, like various
embryological structures, to the retention of a former character. But
this view can be maintained with confidence, only when the young of
several species resemble each other closely, and likewise resemble
other adult species belonging to the same group; for the latter are the
living proofs that such a state of things was formerly possible. Young
lions and pumas are marked with feeble stripes or rows of spots, and as
many allied species both young and old are similarly marked, no
believer in evolution will doubt that the progenitor of the lion and
puma was a striped animal, and that the young have retained vestiges of
the stripes, like the kittens of black cats, which are not in the least
striped when grown up. Many species of deer, which when mature are not
spotted, are whilst young covered with white spots, as are likewise
some few species in the adult state. So again the young in the whole
family of pigs (Suidae), and in certain rather distantly allied
animals, such as the tapir, are marked with dark longitudinal stripes;
but here we have a character apparently derived from an extinct
progenitor, and now preserved by the young alone. In all such cases the
old have had their colours changed in the course of time, whilst the
young have remained but little altered, and this has been effected
through the principle of inheritance at corresponding ages.
This same principle applies to many birds belonging to various groups,
in which the young closely resemble each other, and differ much from
their respective adult parents. The young of almost all the
Gallinaceae, and of some distantly allied birds such as ostriches, are
covered with longitudinally striped down; but this character points
back to a state of things so remote that it hardly concerns us. Young
cross-bills (Loxia) have at first straight beaks like those of other
finches, and in their immature striated plumage they resemble the
mature red-pole and female siskin, as well as the young of the
goldfinch, greenfinch, and some other allied species. The young of many
kinds of buntings (Emberiza) resemble one another, and likewise the
adult state of the common bunting, E. miliaria. In almost the whole
large group of thrushes the young have their breasts spotted a
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