species.

With respect to the baleen, Mr. Mivart remarks that if it "had once
attained such a size and development as to be at all useful, then its
preservation and augmentation within serviceable limits would be promoted
by natural selection alone. But how to obtain the beginning of such useful
development?" In answer, it may be asked, why should not the early
progenitors of the whales with baleen have possessed a mouth constructed
something like the lamellated beak of a duck? Ducks, like whales, subsist
by sifting the mud and water; and the family has sometimes been called
Criblatores, or sifters. I hope that I may not be misconstrued into saying
that the progenitors of whales did actually possess mouths lamellated like
the beak of a duck. I wish only to show that this is not incredible, and
that the immense plates of baleen in the Greenland whale might have been
developed from such lamellae by finely graduated steps, each of service to
its possessor.

The beak of a shoveller-duck (Spatula clypeata) is a more beautiful and
complex structure than the mouth of a whale. The upper mandible is
furnished on each side (in the specimen examined by me) with a row or comb
formed of 188 thin, elastic lamellae, obliquely bevelled so as to be
pointed, and placed transversely to the longer axis of the mouth. They
arise from the palate, and are attached by flexible membrane to the sides
of the mandible. Those standing towards the middle are the longest, being
about one-third of an inch in length, and they project fourteen one-
hundredths of an inch beneath the edge. At their bases there is a short
subsidiary row of obliquely transverse lamellae. In these several respects
they resemble the plates of baleen in the mouth of a whale. But towards
the extremity of the beak they differ much, as they project inward, instead
of straight downward. The entire head of the shoveller, though