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 



