186 THE ORIGIN OF SPECIES 



characters, or those common to all the species, are the most con- 

 stant. 



The Greenland whale is one of the most wonderful animals in 

 the world, and the baleen, or whalebone, one of its greatest pe- 

 culiarities. The baleen consists of a row, on each side of the upper 

 jaw, of about 300 plates or laminae, which stand close together 

 transversely to the longer axis of the mouth. Within the main row 

 there are some subsidiary rows. The extremities and inner margins 

 of all the plates are frayed into stiff bristles, which clothe the 

 whole gigantic palate, and serve to strain or sift the water, and 

 thus to secure the minute prey on which these great animals 

 subsist. The middle and longest lamina in the Greenland whale 

 is ten, twelve, or even fifteen feet in length; but in the different 

 species of Cetaceans there are gradations in length; the middle 

 lamina being in one species, according to Scoresby, four feet, in 

 another three, in another eighteen inches, and in the Balaenoptera 

 rostra ta only about nine inches in length. The quality of the 

 whalebone also differs in the different species. 



With respect to the baleen, Mr. Mivart remarks that if it "had 

 once attained such a size and development as to be at all useful, 

 then its preservation and augmentation within serviceable limits 

 would be promoted by natural selection alone. But how to obtain 

 the beginning of such useful development?" In answer, it may be 

 asked, why should not the early progenitors of the whales with 

 baleen have possessed a mouth constructed something like the 

 lamellated beak of a duck? Ducks, like whales, subsist by sifting 

 the mud and water; and the family has sometimes been called 

 Criblatores, or sifters. I hope that I may not be misconstrued into 

 saying that the progenitors of whales did actually possess mouths 

 lamellated like the beak of a duck. I wish only to show that this 

 is not incredible, and that the immense plates of baleen in the 

 Greenland whale might have been developed from such lamellae 

 by finely graduated steps, each of service to its possessor. 



The beak of the shoveller-duck (Spatula clypeata) is a more 

 beautiful and complex structure than the mouth of a whale. The 

 upper mandible is furnished on each side (in the specimen exam- 

 ined by me) with a row or comb formed of 188 thin, elastic lamel- 

 lae, obliquely beveled so as to be pointed, and placed transversely 

 to the longer axis of the mouth. They arise from the palate, and 

 are attached by flexible membrane to the sides of the mandible. 

 Those standing towards the middle are the longest, being about 

 one-third of an inch in length, and they project fourteen one- 



