236 ORIGIN OF SPECIES 



rendered the insect at all less like the imitated object, they 

 would be eliminated. There would indeed be force in Mr. 

 Mivart's objection, if we were to attempt to account for the 

 above resemblances, independently of natural selection, 

 through mere fluctuating variability; but as the case stands 

 there is none. 



Nor can I see any force in Mr. Mivart's difficulty with re- 

 spect to "the last touches of perfection in the mimicry;" as 

 in the case given by Mr. Wallace, of a walking-stick insect 

 (Ceroxylus laceratus), which resembles "a stick grown over 

 by a creeping moss or jungermannia." So close was this 

 resemblance, that a native Dyak maintained that the foli- 

 aceous 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 towards its 

 preservation; and the more perfect the resemblance so much 

 the better for the insect. Considering the nature of the dif- 

 ferences between the species in the group which includes the 

 above Ceroxylus, there is nothing improbable in this insect 

 having varied in the irregularities on its surface, and in these 

 having become more or less green-coloured; for in every 

 group the characters which differ in the several species are 

 the most apt to vary, whilst the generic characters, or those 

 common to all the species, are the most constant. 



The Greenland whale is one of the most wonderful animals 

 in the world, and the baleen, or whale-bone, one of its great- 

 est peculiarities. 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, 



