DARWIN, AND THE ORIGIN OF SPECIES 199 



were to make the head of the shoveller as long as that of the 

 Balaenoptera, the lamellae would be six inches in length ; that 

 is, two-thirds of the length of the baleen in this species of whale. 

 The lower mandible of the shoveller duck is furnished with lamellae 

 of equal length with those above, but finer; and in being thus 

 furnished it differs conspicuously from the lower jaw of the whale, 

 which is destitute of baleen. On the other hand, the extremities 

 of the lower lamellae are frayed into fine bristly points, so that they 

 thus curiously resemble the plates of baleen. In the genus Prion, a 

 member of the distinct family of the Petrels, the upper mandible 

 alone is furnished with lamellae, which are well developed and 

 project beneath the margin, so that the beak of this bird in this 

 respect resembles the mouth of a whale. 



" From the highly developed structure of the shoveller's beak 

 we may proceed, without any great break, as far as fitness for 

 sifting is concerned, through the beak of the Merganetta armata, 

 and in some respects through that of the Aix sponsa to the beak 

 of the common duck. In this latter species the laminae are much 

 coarser than in the shoveller, and are firmly attached to the sides 

 of the mandible ; they are only about fifty in number on each side, 

 and do not project at all beneath the margin. They are square- 

 tipped, and* are edged with translucent, hardish tissue, as if for 

 crushing food. The edges of the lower mandible are crossed by 

 numerous fine ridges, which project very little. Although the beak 

 is thus very inferior to that of the shoveller as a sifter, yet this bird, 

 as every one knows, constantly uses it for this purpose. There are 

 other species in which the laminae are considerably less developed 

 than in the common duck, but I do not know whether they use their 

 beaks for sifting the water. 



" Turning to another group of the same family. In the Egyptian 

 goose (Chenoplax) the beak closely resembles that of the common 

 duck; but the laminae are not so numerous, nor do they project 

 so far inwards; yet this goose uses its bill like a duck by throwing 

 the water out of the corners. Its chief food, however, is grass, 

 which it crops like a common goose. In the latter bird the laminae 

 of the upper mandible are much coarser than in the common duck, 

 almost confluent, about twenty-seven in number on each side, and 

 terminating upwards in tooth-like knobs. The palate is also covered 



