4 WHAT EVOLUTION IS 



tinual flux and change. Thus the 

 present configuration of oceans and 

 of continents, of mountains and of 

 abysses, is looked upon, not as some- 

 thing stationary, but as due to opera- 

 tions whose titanic energies have been 

 exerting themselves through untold 

 ages in the past and will continue so 

 to act far into the future. These 

 happenings, and such as occur among 

 the stars, constitute what may be 

 called cosmic evolution, a body of 

 change which in the nature of things 

 preceded life and was, in a certain 

 sense, preparatory to it. It is the 

 plan of this book, not to deal with 

 this type of evolution, notwithstand- 

 ing the fact that cosmic evolution is 

 intimately bound up with the origin 

 of living things, but to consider ex- 

 clusively the kind of evolution that 

 has to do with organisms, with plants 

 and animals. Such a type of evolu- 



