2i4 THE DARWINIAN THEORY 



to examine the question of species who has not 

 minutely described many." 



Subsequent to the publication of the " Origin of 

 Species" much time was taken up by successive 

 editions of the work, and much lost through ill- 

 health. Darwin himself described his books as the 

 " milestones of my life " ; and they fall into two 

 great groups — those completing the " Origin of 

 Species," and those on more or less independent 

 lines, such as the great Botanical Series. 



I. Works completing the "Origin of Species." 



This work was itself an "abstract," and this was 

 the title he proposed to give it, having originally 

 designed it to be of much greater length. How- 

 ever, yielding to the publishers, he produced it in 

 its present form. 



In 1868 appeared "Variations of Animals and 

 Plants under Domestication," in which a detailed 

 account was given of artificial breeding ; and this 

 was intended to be followed by two other works 

 dealing with variation, heredity, embryology, geo- 

 graphical distribution, &c, in similar detail ; but 

 these were never written. 



The detailed application of the theory to man was 

 inevitable ; and in the first edition of the " Origin of 

 Species " he says : "In the distant future I see open 

 fields for far more important researches. Psychology 

 will be based on a new foundation, that of the 

 necessary acquirement of each mental power and 

 capacity by graduation. Light will be thrown on the 



