igO PIONEERS OF EVOLUTION. 



1850. Social Statics: especially chapter General 

 Considerations. (Higher human Evo- 

 lution.) 



1852. March. Development Hypothesis, in the 

 Leader. (Evolution of species, vid. 

 ante, p. iii.) 



1852. April. Theory of Population, etc., in West- 

 minster Review. (Higher human Evo- 

 lution.) 



1854. July. The Genesis of Science in British 



Quarterly Review. (Intellectual Evo- 

 lution.) 



1855. July. Principles of Psychology. (Mental 



Evolution in general.) 



1857. April. Progress: its Law and Cause: West- 

 minster Review. (Evolution at large.) 



1857. April. Ultimate Laws of Physiology. 

 National Review. (Another factor of 

 Evolution at large.) 



" From these last two Essays came the inception 

 of the Synthetic Philosophy. The first programme 

 of it was drawn up in January, 1858." . . . 



When seeing Mr. Spencer on the subject of this 

 letter, he took the further trouble to point out certain 

 passages in the essays originally comprised in the 

 one volume edition of 1858 which contain germinal 

 ideas of his synthesis. That they are his selection 

 will add to the interest and value of their quotation, 

 reveahng, as perchance they may, a fragment of the 



