LIST OF ILLUSTRATIONS 



FACING 

 . PAGE 



Charles Robert Darwin (1809-1882)" Frontispiece 



The Chevalier de Lamarck (1744-1829) 18 



Phenacodus, an Early Generalized Mammal 224 



The Dawn Horse 224 



The Three-toed Horse 228 



The American Horse 228 



August Weismann (1834) 238 



Hugo de Vries . . 246 



