104 THE EVOLUTIONIST AT LARGE. 



as their unimproved forefathers had done 

 millions of aeons before. Similarly, cater- 

 pillars are still all but exact patterns of the 

 primaeval insect, while butterflies are totally 

 different and far higher creatures. Thus, in 

 spite of adult degeneracy in the ascidian and 

 adult progress in the frog, both tadpoles 

 preserve for us very nearly the original form 

 of their earliest backboned ancestor. Each 

 individual recapitulates in its own person the 

 whole history of evolution in its race. This 

 is a very lucky thing for biology ; since 

 without these recapitulatory phases we could 

 never have traced the true lines of descent in 

 many cases. It would be a real misfortune 

 for science if every frog had been born a 

 typical amphibian, as some tree-toads actually 

 are, and if every insect had emerged a fully 

 formed adult, as some aphides very nearly do. 

 Larvae and embryos show us the original 

 types of each race ; adults show us the total 

 amount of change produced by progressive 

 or retrogressive development. 



