64 THE EVOLVTIOM^T AT LARGE. 



long prehensile tail of the monkeys has 

 grown gradually shorter, and, being at last 

 coiled up under the haunches, has finally de- 

 generated into an insignificant and wholly 

 embedded terminal joint But, indeed, we can 

 find traces of a similar adaptation to circum- 

 stances everywhere. Take, for instance, the 

 common English amphibians. The newt 

 passes all its life in the water, and therefore 

 always retains its serviceable tail as a swim- 

 ming organ. The frog in its tadpole state is 

 also aquatic, and it swims wholly by means of 

 its broad and flat rudder-like appendage. But 

 as its legs bud out, and it begins to fit itself 

 for a terrestrial existence, the tail undergoes 

 a rapid atrophy, and finally fades away alto- 

 gether. To a hopping frog on land, such a 

 long train would be a useless drag, while in 

 the water its webbed feet and muscular legs 

 make a satisfactory substitute for the lost 

 organ. Last of all, the tree-frog, leading a 

 specially terrestrial life, has no tadpole at all, 

 but emerges from the egg in the full frog- 



