2 INTRODUCTION. 



least a large number of naturalists m;:st admit that 

 species are the modified descendants of other species ; 

 and this especially holds good with the younger and 

 rising naturalists. The greater number accept the 

 agency of natural selection ; though some urge, whether 

 with justice the future must decide, that I have greatly 

 overrated its importance. Of the older and honored 

 chiefs in natural science, many unfortunately are still 

 opposed to evolution in every form. 



In consequence of the views now adopted by most 

 naturalists, and which will ultimately, as in every other 

 case, be followed by other men, I have been led to put 

 together my notes, so as to see how far the general 

 conclusions arrived at in my former works were appli- 

 cable to man. This seemed all the more desirable 

 as I had never deliberately applied these views to a 

 species taken singly. When we confine our attention 

 to any one form, we are deprived of the weighty argu- 

 ments derived from the nature of the affinities which 

 connect together whole groups of organisms — their geo- 

 graphical distribution in past and present times, and 

 their geological succession. The homological struct ure, 

 embryological development, and rudimentary organs of 

 a species, whether it be man or any other animal, to 

 which our attention may be directed, remain to be con- 

 sidered ; but these great classes of facts afford, as it 

 appears to me, ample and conclusive evidence in favor 

 of the principle of gradual evolution. The strong sup- 



