I.] INTRODUCTORY. 21 



"walking leaf" (an insect belonging to the grasshopper 

 and cricket order) is a well-known and conspicuous instance 

 of the assumption by an animal of the appearance of a 

 vegetable structure (see illustration on p. 47) ; and the bee. 

 fly, and spider orchids, are familiar examples of a converse 

 resemblance. Birds, butterflies, reptiles, and even fish, 

 seem to bear in certain instances a similarly striking re- 

 semblance to other birds, butterflies, reptiles, and fish, of 

 altogether distinct kinds. The explanation of this matter 

 which " Natural Selection " offers, as to animals, is that cer- 

 tain varieties of one kind have found exemption from per- 

 secution in consequence of an accidental resemblance which 

 such varieties have exhibited to animals of another kind, or 

 to plants ; and that they were thus preserved, and the de- 

 gree of resemblance was continually augmented in their 

 descendants. As to plants, the explanation offered by this 

 theory might, perhaps, be, that varieties of plants, which 

 presented a certain superficial resemblance in their flowers 

 to insects, have thereby been helped to propagate their 

 kind, the visit of certain insects being useful or indispen- 

 sable to the fertilization of many flowers. 



We have thus a whole series of important facts which 

 " Natural Selection " helps us to understand and coordi- 

 nate. And not only are all these diverse facts strung to- 

 gether, as it were, by the theory in question ; not only 

 does it explain the development of the complex instincts 

 of the beaver, the cuckoo, the bee, and the ant, as also the 

 dazzling brilliancy of the humming-bird, the glowing tail 

 and neck of the peacock, and the melody of the nightin- 

 gale ; the perfume of the rose and the violet, the bril- 

 liancy of the tulip and the sweetness of the nectar of flow- 

 ers ; not only does it help us to understand all these, but 

 serves as a basis of future research and of inference from 

 the known to the unknown, and it guides the investigator 

 to the discovery of new facts which, when ascertained, it 



