170 NATURAL SELECTION ^ vin 



ties of" mankind 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 thou- 

 sand 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 physical change when certain con- 

 ditions 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 selec- 

 tion 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, deformi- 

 ties, or beauties ; it resembles them in general more than it 

 does any other individuals ; yet children of the same parents 

 are not all alike, and it often happens that they differ very 

 considerably from their parents and from each other. This 

 is equally true of man, of all animals, and of all plants. 

 Moreover, it is found that individuals do not differ from their 

 parents in certain particulars only, while in all others they 

 are exact duplicates of them. They differ from them and 

 from each other in every particular : in form, in size, in 

 colour ; in the structure of internal as well as of external 

 organs ; in those subtle peculiarities which produce differences 

 of constitution, as well as in those still more subtle ones 

 which lead to modifications of mind and character. In other 

 words, in every possible way, in every organ, and in every 

 function, individuals of the same stock vary. 



Now, health, strength, and long life are the results of a 

 harmony between the individual and the universe that sur- 

 rounds it. Let us suppose that at any given moment this 

 harmony is perfect. A certain animal is exactly fitted to 



