4 THE WONDER OF LIFE 



there is more and more behaviour as we ascend, and we 

 may even discern the springs of conduct. 



It must not be supposed, however, that the history 

 discloses any straightforward progress, for it is full of 

 retrogressions and of strange culs-de-sac. The tapeworm 



FIG. 2. Extinct bipedal Reptile, Iguanodon mantelli, about 12 feet 

 high. The genus is restricted to the Wealden (Cretaceous). (After 

 Dollo.) 



is as much a product of evolution as the bird, and is as 

 well adapted to its inglorious lot as the lark to heaven's 

 gate. There have been extraordinary failures, too, in the 

 sense that many extinct types of great perfection have 

 left no direct descendants. We do not know that their 



