188 THE ORIGIN OF SPECIES 



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 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 tear- 

 ing 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, ac- 

 cording 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, aiding 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 lam- 

 ellae 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 would have served ex- 

 clusively as a sifting apparatus. From this stage, in which the 

 lamellae would be two-thirds of the length of the plates of baleen 

 in the Balaenoptera rostrata, gradations, which may be observed 



