20 INTRODUCTION 



writings, I give his authority in the text; other statements 

 I leave as they originally stood in my manuscript, occasion- 

 ally giving in the footnotes references to his works, as a 

 confirmation of the more doubtful or interesting points. 



Daring many years it has seemed to me highly probable 

 that sexual selection has played an important part in difier* 

 entiating the races of man; but in my "Origin of Species" 

 (first edition, p. 199) I contented myself by merely alluding 

 to this belief. When I came to apply this view to man, I 

 found it indispensable to treat the whole subject in full 

 detail.* Consequently the second part of the present work, 

 treating of sexual selection, has extended to an inordinate 

 length, compared with the first part; but this could not 

 be avoided. 



I had intended adding to the present volumes an essay 

 on the expression of the various emotions by man and th® 

 lower animals. My attention was called to this subject many 

 years ago by Sir Charles Bell's admirable work. This illus- 

 trious anatomist maintains that man is endowed with certain 

 muscles solely for the sake of expressing his emotions. As 

 this view is obviously opposed to the belief that man is de- 

 scended from some other and lower form, it was necessary 

 for me to consider it. I likewise wished to ascertain how 

 far the emotions are expressed in the same manner by the 

 diflEerent races of man. But owing to the length of the pres- 

 ent work, I have thought it better to reser\re my essay for 

 separate publication. 



' Prof. Hackel was the only author who, at the time when this work first 

 appeared, had discussed the subject of sexual selection, and had seen its full 

 importance, since the publication of the "Origin"; and this he did iuaTeiy 

 able manner in his various works. 



