SELECTION ON MAN. 307 



seems that the best of the argument is on the side of 

 those who maintain the primitive diversity of man. 

 Their opponents have not been able to refute the per- 

 manence of existing races as far back as we can trace 

 them, and have failed to show, in a single case, that 

 at any former epoch the well marked varieties of man- 

 kind approximated more closely than they do at the 

 present day. At the same time this is but negative 

 evidence. A condition of immobility for four or five 

 thousand years, does not preclude an advance at an 

 earlier epoch, and if we can show that there are 

 causes in nature which would check any further phy- 

 sical change when certain conditions were fulfilled 

 does not even render such an advance improbable, if 

 there are any general arguments to be adduced in its 

 favour. Such a cause, I believe, does exist ; and I 

 shall now endeavour to point out its nature and its 

 mode of operation. 



Outline of the Theory of Natural Selection. 



In order to make my argument intelligible, it is 

 necessary for me to explain very briefly the theory of 

 " Natural Selection " promulgated by Mr. Darwin, 

 and the power which it possesses of modifying the 

 forms of animals and plants. The grand feature in 

 the multiplication of organic life is, that close general 

 resemblance is combined with more or less individual 

 variation. The child resembles its parents or ancestors 

 more or less closely in all its peculiarities, deformities, 

 or beauties ; it resembles them in general more than it 



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