PREFACE 



SEVERAL years ago Lord Rosebery founded, in 

 the University of Edinburgh, a lectureship on " The 

 Philosophy of Natural History/' and I was invited by 

 the Senatus to deliver the lectures. This invitation 

 I accepted, and subsequently constituted the material 

 of my lectures the foundation of another course, which 

 was given in the Royal Institution, under the title 

 " Before and after Darwin/' Here the course extended 

 over three years namely from 1888 to 1890. The 

 lectures for 1888 were devoted to the history of biology 

 from the earliest recorded times till the publication of 

 the " Origin of Species " in 1 859 ; the lectures for 

 1889 dealt with the theory of organic evolution up to 

 the date of Mr. Darwin's death, in 1882 ; while 

 those of the third year discussed the further develop- 

 ments of this theory from that date till the close of 

 the course in 1890. 



It is from these two courses which resembled each 

 other in comprising between thirty and forty lectures, 

 but differed largely in other respects that the pre- 

 sent treatise has grown. Seeing, however, that it has 



