PREFATORY NOTE. 



THE present volume is made up of popular essays or 

 addresses on the general subject of Organic Evolution. 

 These were originally given as oral lectures before 

 University Extension societies in California, having 

 been condensed and written out in their present form 

 after delivery. Three of these papers have already 

 appeared in Appletons' Popular Science Monthly, and 

 three in The Arena. To the editors of these periodicals 

 I am indebted for the privilege of reprinting them. 



Besides the twelve essays of my own, it is my good 

 fortune to enhance the value of the volume by the in- 

 sertion of three papers of special importance, setting 

 forth the present state of knowledge concerning the 

 method of evolution and the method of heredity. The 

 first of these, on the Factors of Organic Evolution as 

 displayed in the Process of Development, is by Professor 

 Edwin Grant Conklin, of the University of Pennsyl- 

 vania ; the second, on the Physical Basis of Heredity, 

 is by Professor Frank Mace McFarland, of Leland Stan- 

 ford Jr. University ; the third, on the Testimony from 

 Paleontology, is by Professor James Perrin Smith, of 



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