almost to be the case; but on actually measuring the old dogs and their
six-days old puppies, I found that the puppies had not nearly acquired
their full amount of proportional difference. So, again, I was told
that the foals of cart and race-horses differed as much as the
full-grown animals; and this surprised me greatly, as I think it
probable that the difference between these two breeds has been wholly
caused by selection under domestication; but having had careful
measurements made of the dam and of a three-days old colt of a race and
heavy cart-horse, I find that the colts have by no means acquired their
full amount of proportional difference.
As the evidence appears to me conclusive, that the several domestic
breeds of Pigeon have descended from one wild species, I compared young
pigeons of various breeds, within twelve hours after being hatched; I
carefully measured the proportions (but will not here give details) of
the beak, width of mouth, length of nostril and of eyelid, size of feet
and length of leg, in the wild stock, in pouters, fantails, runts,
barbs, dragons, carriers, and tumblers. Now some of these birds, when
mature, differ so extraordinarily in length and form of beak, that they
would, I cannot doubt, be ranked in distinct genera, had they been
natural productions. But when the nestling birds of these several
breeds were placed in a row, though most of them could be distinguished
from each other, yet their proportional differences in the above
specified several points were incomparably less than in the full-grown
birds. Some characteristic points of difference for instance, that of
the width of mouth could hardly be detected in the young.
But there was one remarkable exception to this rule, for the young of
the short-faced tumbler differed from the young of the wild rock-pigeon
and of the other breeds, in all its proportions, almost exactly as much
as in the adult state.
The two principles above given seem to me to explain these facts in
regard to the later embryonic stages of our domestic varieties.
Fanciers select their horses, dogs, and pigeons, for breeding, when
they are nearly grown up: they are indifferent whether the desired
qualities and structures have been acquired earlier or later in life,
if the full-grown animal possesses them. And the cases just given, more
especially that of pigeons, seem to show that the characteristic
differences which give value to each breed, and which have been
accumulated by man s selection, have not generally first appeared at an
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