LIST OF ILLUSTRATIONS 
Charles Robert Darwin (1809-1882) . 
The Chevalier de Lamarck (1744-1829) 
Phenacodus, an Early Generalized Mammal 
The Dawn Horse 
The Three-toed Horse . 
The American Horse 
August Weismann (1834) 
Hugo de Vries. . «ww ew ee 
FACING 
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Frontispiece. 
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