The Origin of Species by Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for Life, 6th EditionDarwin, Charles
History
The Origin of Species by Means of Natural Selection: Or, the Preservation of Favoured Races in the Struggle for Life, 6th Edition
Darwin, Charles
Evolution (Biology); Natural selection
From the highly developed structure of the shoveller’s beak we may
proceed (as I have learned from information and specimens sent to me by
Mr. Salvin), without any great break, as far as fitness for sifting is
concerned, through the beak of the Merganetta armata, and in some
respects through that of the Aix sponsa, to the beak of the common
duck. In this latter species the lamellæ are much coarser than in the
shoveller, and are firmly attached to the sides of the mandible; they
are only about fifty in number on each side, and do not project at all
beneath the margin. They are square-topped, and are edged with
translucent, hardish tissue, as if for crushing food. The edges of the
lower mandible are crossed by numerous fine ridges, which project very
little. Although the beak is thus very inferior as a sifter to that of
a shoveller, yet this bird, as every one knows, constantly uses it for
this purpose. There are other species, as I hear from Mr. Salvin, in
which the lamellæ are considerably less developed than in the common
duck; but I do not know whether they use their beaks for sifting the
water.
Turning to another group of the same family. In the Egyptian goose
(Chenalopex) the beak closely resembles that of the common duck; but
the lamellæ are not so numerous, nor so distinct from each other, nor
do they project so much inward; yet this goose, as I am informed by Mr.
E. Bartlett, “uses its bill like a duck by throwing the water out at
the corners.” Its chief food, however, is grass, which it crops like
the common goose. In this latter bird the lamellæ of the upper mandible
are much coarser than in the common duck, almost confluent, about
twenty-seven in number on each side, and terminating upward in
teeth-like knobs. The palate is also covered with hard rounded knobs.
The edges of the lower mandible are serrated with teeth much more
prominent, coarser and sharper than in the duck. The common goose does
not sift the water, but uses its beak exclusively for tearing or
cutting herbage, for which purpose it is so well fitted that it can
crop grass closer than almost any other animal. There are other species
of geese, as I hear from Mr. Bartlett, in which the lamellæ are less
developed than in the common goose.
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