CH XL. NATURAL SELECTION. ' 431 



the clover did not enable the moths to enter, those plants 

 would die out like the others. And this is one of the most 

 striking facts which Mr. Darwin has pointed out ; namely, 

 that no variation will continue and increase from generation 

 to generation unless it is useful to the plant or animal which 

 possesses it ; so that if this theory be true, every beautiful 

 colour which we admire in animals and plants, every minute 

 detail in their fonn and structure, is not only to be admired 

 for its beauty, but because it is an evidence of that won- 

 derful harmony of nature which keeps every part, however 

 insignificant, exactly fitted to do its work in the one great 

 scheme of creation. 



Difficulties in Natural History explained by Natural 

 Selection. — And now, if we adopt Mr. Darwin's explanation, 

 you will see how St.-Hilaire and Cuvier could both be 

 right when the one said that all animals are formed on 

 one plan, and the other that each part of an animal is 

 exactly fitted to work harmoniously with the rest of its 

 body. For if animals have been gradually altered the one 

 from the other, it is natural they should all be made on 

 one plan ; as, for instance, if the ancestor of the bat, millions 

 of years ago, was also the ancestor of those animals out of 

 which the horse has come, then the bones of the bat's wing 

 rhay well be similar to those of the horse ; while, on the 

 other hand, if no variation can become fixed, and develope 

 into important parts or organs unless it is useful, it is clear 

 that all the parts of an animal must have been gradually 

 modified so as to fit each other and to work in the best pos- 

 sible way for its well-being. Again, it explains why the living 

 animals in a country should be of the same class, though 

 slightly different from those found fossil in the earth. For 

 if in Australia the ancestors were pouched animals, it must 



