OBJECTIONS TO THE THEORY 309 



conjectural remarks have been made merely to show that 

 a transition of structure, with each step beneficial, is a 

 highly complex affair; and that there is nothing strange 



I in a transition not having occurred in any particular 

 case. 



Lastly, more than one writer has asked, why have 

 some animals had their mental powers more highly de- 

 veloped than others, as such development would be 

 advantageous to all? Why have not apes acquired the 

 intellectual powers of man? Various causes could be 

 assigned; but as they are conjectural, and their relative 

 probability cannot be weighed, it would be useless to give 

 them. A definite answer to the latter question ought not 

 to be expected, seeing that no one can solve the simpler 

 problem why, of two races of savages, one has risen 

 higher in the scale of civilization than the other; and 

 this apparently implies increased brain-power. 



We will return to Mr. Mivart's other objections. In- 

 sects often resemble for the sake of protection various 

 objects, such as green or decayed leaves, dead twigs, bits 

 of lichen, flowers, spines, excrement of birds, and living 

 insects; but to this latter point I shall hereafter recur. 

 The resemblance is often wonderfully close, and is not 

 confined to color, but extends to form, and even to the 

 manner in which the insects hold themselves. The cater- 

 pillars which project motionless like dead twigs from the 

 bushes on which they feed, offer an excellent instance of 

 la resemblance of this kind. The cases of the imitation 

 jl^lj lof such objects as the excrement of birds are rare and 

 aj lexceptional. On this head, Mr. Mivart remarks, "As, 

 foi |according to Mr. Darwin's theory, there is a constant 

 endency to indefinite variation, and as the minute incipi- 



