Seite - 239 - in The Origin of Species

THEORY OF NATURAL SELECTION 239 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 27 in number on each side, and ter- minating upwards 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 tear- ing 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 the 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 com- mon 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 desti- tute 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 regu- larly 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 sift- ing the water; then into lamellae like those of the domestic duck; and so onwards, until they became as well constructed