34 VIGNETTES FROM NATURE. 



a bird, and so devoured, is wiped out of 

 existence for ever, with all its possible pro- 

 geny. Every butterfly which escapes, by 

 however slight a peculiarity, is enabled to lay 

 its eggs in peace, and to hand on its peculiar- 

 ities to its posterity. This sort of selection 

 is going on every day around us, and no 

 difference is too slight for it to select, no 

 resemblance is too clumsy provided it once 

 for a moment aids the insect in avoiding 

 destruction. 



Now, we all know that the eyes of birds 

 are very sharp and keen indeed. A hawk 

 soaring so high in the sky that human sight 

 fails to perceive it, will yet discriminate and 

 pounce down upon a lark in the fields below 

 a small brown bird seated upon a brown 

 clod of earth exactly like itself in colour. In 

 just the same way the insectivorous birds 

 keep a sharp look-out for moths and butter- 

 flies, upon which they swoop at once when- 

 ever they distinguish them upon the ground 

 beneath. Every day those insects whose 



