INTRODUCTION. 5 



each species has been independently created — is erroneous. 

 I am fully convinced that species are not immutable; but 

 that those belonging to what are called the same genera are 

 lineal descendants of some other and generally extinct 

 species, in the same manner as the acknowledged varieties 

 of any one species are the descendants of that species. 

 Furthermore, I am convinced that natural selection has been 

 the most important, but not the exclusive, means of modifi- 

 cation. 



