170 NATURAL SELECTION Vir 
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 
