and the Darwinian Theory. 165 



beauty in different races is as important as difference in the 

 skin and hair ; and in accounting for the origin of races, it is 

 quite as important to account for the former as for the latter; 

 any theory that simply attributes the difference in the colour 

 of the skin to difference in the ideal of beauty will be met by 

 the suspicion that the difference in the ideal was preceded by 

 the difference in the colour. My own strong conviction is 

 that the true explanation is equally applicable to either set of 

 phenomena. 



Darwin's Reference to the Causes which Check the 

 Crossing of Varieties. 



In the second paragraph quoted from Darwin at the be- 

 ginning of this chapter we find mention of three causes that 

 may for a long time prevent the members of the same species 

 from freely intercrossing while occupying the same area; but 

 subsequent statements, in the same and the three succeeding 

 sections, show that he regarded geographical and local sepa- 

 ration as the forms of separate breeding that are most favour- 

 able to the production of new species. Moreover, in the two 

 sections relating to " Divergence of Character," he seems to 

 maintain that the prevention of intercrossing is not a neces- 

 sary condition for divergence of character in members of the 

 same species that are competing with each other *. In 

 Chapter XVI. of his "Variation under Domestication" several 

 causes that interfere with the free crossing of varieties are 

 enumerated ; but they are nowhere recognized as essential 

 factors in the evolution of divergent varieties and species, 

 without which diversity of natural selection would be of no 

 avail, and with which divergence will take place though there 

 is no change in the environment. They are looked upon as 

 characteristics in which many varieties more or less resemble 

 species ; but they are regarded as the results rather than the 

 causes of divergent evolution. 



Conclusion. 



We therefore rind that though Darwin has not recognized 

 segregation, which is the independent propagation of different 



* In ' Nature,' vol. xxxiv. p. 407, Mr. Francis Darwin states that in his 

 copy of Belt's ' Naturalist in Nicaragua ' the words " No, No " are pen- 

 cilled in his father's handwriting on the margin opposite the sentence : 

 " All the individuals might vary in tome one direction, but they could not 

 split up into distinct species whilst they occupied the same area and inter- 

 bred without difficulty." This seems to give a decisive answer concerning 

 Darwin's opinion on this subject. 



