Chap. Vn.] THEORY OP NATTTRAL SELECTION. 289 



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 se- 

 curing live fish. 



Eeturning to the whales. The Hyperoodon bidens 

 is destitute of true teeth in an efficient condition, but 

 its palate is roughened, according to Laeepede, with 

 small, unequal, hard points of horn. There is, there- 

 fore, 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 lamellffi like those 

 of the domestic duck; and so onwards, until they became 

 as well constructed as those of the shoveller, in which 

 case they would have served exclusively as a sifting ap- 

 paratus. Prom this stage, in which the lamellae would 

 be twQ-thirds of the length of the plates of baleen in the 

 Balaenoptera rostrata, gradations, which may be ob- 

 served in still-existing Cetaceans, lead us onwards to the 

 enormous plates of baleen in the Greenland whale. ISTor 

 is there the least reason to doubt that each step in this 

 scale might have been as serviceable to certain ancient 

 Cetaceans, with the functions of the parts slowly chang- 

 ing during the progress of development, as are the grada- 



