THEORY OF NATURAL SELECTION 203 



sect (Ceroxylus lacerattis), which resembles "a stick grown 

 over by a creeping moss or jungeriiiaiiiiia." So close was 

 this resemblance, that a native Dyak maintained that the 

 foliaceons excrescences were really moss. Insects are preyed 

 on by birds and other enemies whose sight is probably 

 sharper than ours, and every grade in resemblance which 

 aided an insect to escape notice or detection, would tend 

 toward its preservation ; and the more perfect the resem- 

 blance, so much the better for the insect. Considering the 

 nature of the differences between the species in the group 

 which includes the above Ceroxylus, there is nothing im- 

 probable in this insect having varied in the irregularities on 

 its surface, and in these having become more or less green- 

 colored ; for in every group the characters which differ in 

 the several species are the most apt to vary, while the 

 generic characters, or those common to all the species, are 

 the most constant. 



The Greenland whale is one of the most wonderful ani- 

 mals in the world, and the baleen, or whalebone, one of its 

 greatest peculiarities. The baleen consists of a row, on each 

 side of the upper jaw, of about 300 plates or lamime, 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 r,he whole gigantic 

 palate, and serve to strain or tift the water, and thus to 

 secure the minute prey on which these great animals subsist. 

 The middle and lonsrest lamina in the Greenland whale is 

 ten, twelve, or even fifteen feet in length ; but in the differ- 

 ent 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 Balsenoptera rostrata 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 laniet 



