out at the
corners." Its chief food, however, is grass, which it crops like the
common goose. In this latter bird the lamellae 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 lamellae are less developed
than in the common goose.

We thus see that a member of the duck family, with a beak constructed
like that of a common goose and adapted solely for grazing, or even
a member with a beak having less well-developed lamellae, might be
converted by small changes into a species like the Egyptian goose--this
into one like the common duck--and, lastly, into one like the shoveller,
provided with a beak almost exclusively adapted for sifting the water;
for this bird could hardly use any part of its beak, except the hooked
tip, for seizing or tearing solid food. The beak of a goose, as I may
add, might also be converted by small changes into one provided with
prominent, recurved teeth, like those of the Merganser (a member of the
same family), serving for the widely different purpose of securing live
fish.

Returning to the whales. The Hyperoodon bidens is destitute of true
teeth in an efficient condition, but its palate is roughened, according
to Lacepede, with small unequal, hard points of horn. There is,
therefore, nothing improbable in supposing that some early Cetacean form
was provided with similar points of horn on the palate, but rather more
regularly placed, and which, like the knobs on the beak of the goose,
aided it in seizing or tearing its food. If so, it will hardly be denied
that the points might have been converted through variation and natural
selection into lamellae as well-developed as those of the Egyptian
goose, in which case they would have been used both for seizing objects
and for sifting the water; then into lamellae like those of the domestic
duck; and so onward, until they became as well constructed as those of
the shoveller, in which case they