214 MISCELLANEOUS OBJECTIONS TO THE 



on most oceanic islands. Gradations of structure, with each 

 stage beneficial to a changing species, will be favored only 

 under certain peculiar conditions. A strictly terrestrial 

 animal, by occasionally hunting for food in shallow water, 

 then in streams or lakes, might at last be converted into 

 an animal so thoroughly acquatic as to brave the open 

 ocean. But seals would not find on oceanic islands the 

 conditions favorable to their gradual reconversion into a 

 terrestrial form. Bats, as formerly shown, probably ac- 

 quired their wings by at first gliding through the air from 

 tree to tree, like the so-called flying squirrels, for the sake 

 of escaping from their enemies, or for avoiding falls; but 

 when the power of true flight had once been acquired, it 

 would never be reconverted back, at least for the above 

 purposes, into the less eflicient power of gliding through 

 the air. Bats, might, indeed, like many birds, have had 

 their wings greatly reduced in size, or completely lost, 

 through disuse; but in this case it would be necessary that 

 they should first have acquired the power of running 

 quickly on the ground, by the aid of tlieir hind legs alone, 

 so as to compete with birds or other ground animals; and 

 for such a change a bat seems singularly ill-fitted. These 

 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 

 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 developed 

 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 can not 

 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 in- 

 creased brain power. 



We will return to Mr. Mivart's other objections. Insects 

 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 



