OBJECTIONS TO THE THEORY OF NATURAL SELECTION 187 



hundredths of an inch beneath the edge. At their bases there is a 

 short subsidiary row of obliquely transverse lamellae. In these 

 several respects they resemble the plates of baleen in the mouth 

 of a whale. But toward the extremity of the beak they differ much, 

 as they project inward, instead of straight downward. The entire 

 head of the shoveller, though incomparably less bulky, is about 

 one-eighteenth of the length of the head of a moderately large 

 Balaenoptera rostrata, in which species the baleen is only nine 

 inches long; so that if we 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 these above, but finer; 

 and in being thus furnished it differs conspicuously from the lower 

 jaw of a whale, which is destitute of baleen. On the other hand, 

 the extremities of these 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 resembles in this respect the mouth of a whale. 



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

 may proceed (as I have learned from information and specimens 

 sent to me by Mr. Salvin), 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 lamellae 

 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- topped, 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 as a sifter to that of a shoveller, yet this 

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

 are other species, as I hear from Mr. Salvin, in which the lamellae 

 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 (Chenalopex) the beak closely resembles that of the com- 

 mon duck; but the lamellae are not so numerous, nor so distinct 

 from each other, nor do they project so much inward; yet this 

 goose, as I am informed by Mr. E. Bartlett, "uses its bill like a 



