CHAPTER XXVI 



Selection not confined to the organic world Illustrations of the action of 

 natural selection in the struggle for existence Degeneration Flight- 

 less birds Extermination of the Morioris Sedentary animals Para- 

 sites Co-operation of natural selection and the so-called Lamarckian 

 factors of evolution The influence of internal secretions upon growth 

 Increase in size beyond the limits of utility. 



THE principle of selection is, of course, by no means confined 

 to living things. The various bodies which make up the 

 inorganic world owe their actual form and arrangement largely 

 to processes of selection which are constantly going on amongst 

 them. The outline of the sea coast is the result of the selective 

 action of atmospheric and tidal agencies upon the different kinds 

 of rock of which it is composed. The softer parts are destroyed 

 first, leaving the more resistant portions to stand out in the form 

 of bluffs or promontories, and to illustrate in the inanimate 

 world the principle of the survival of the fittest. We might even 

 say that the prominent headlands exhibit adaptation, for if they 

 were not adapted by their peculiar hardness to resist the dis- 

 integrating influences of the environment they would not be 

 there, but would have perished with those portions of the land 

 which formerly occupied the bays and inlets. 



All things, in short, must be subject to the selective action of 

 their environment, and we need not hesitate to attribute to 

 natural selection a very large share in the modelling of the 

 features of the organic world as we now see it. We know what 

 we ourselves, by our so-called artificial selection, are able to do 

 in this way. The chief difference between artificial and natural 

 selection is that man selects for his own purposes and modifies 

 organisms to suit his own ends, while Nature selects to the benefit 

 of the species operated upon, which becomes thereby modified to 

 its own advantage and preservation in the struggle for existence. 

 But we cannot really draw a distinction between the two kinds 

 of selection, for even in a state of nature organisms are often 

 selected and modified to the advantage of other organisms. 



