PREFACE xv 



in 1858 and 1859 are those brought about by the 

 researches and the thoughts of Weismann ; and 

 these have given to the great theory which will 

 ever be associated with the names of the two 

 illustrious English naturalists a position far higher 

 than that ever assigned to it by Darwin himself.' 



EDWARD B. POULTON. 



OXFORD, 

 Nov. 24, 1909. 



