194 DARWINISM AND HUMAN LIFE 



may be carried through its initial stages by being 

 correlated with another more important change. 



(4) The eliminative processes that most Dar- 

 winians believe in, because they see them going 

 on, may be slow as well as quick, gentle as well 

 as severe, environmental as well as competitive. 

 The selected are not necessarily those saved from 

 the jaws of violent death; they may be simply 

 those who, in virtue of a heritable peculiarity, have 

 a rather longer and more successful life and a 

 rather larger and more successful family. The 

 only eliminative processes that can be believed 

 in as counting for much in evolution are those 

 which are discriminate and consistent. Thinning 

 turnips may serve as our diagram of indiscriminate 

 elimination (only very indirectly does it improve 

 the turnip race) ; Luther Burbank carefully 

 burning some of his most interesting creations 

 because they are not quite right for his purpose 

 may serve as our diagram of discriminate elimina- 

 tion. But while the modes of natural selection 

 are many and various, the logic of the process 

 is always the same when a heritable peculiarity 

 is of critical moment in favouring survival it will 

 tend to persist, provided (a) that its occurrence 

 is sufficiently frequent, and (b) that the dis- 

 criminate selection fostering it is kept up con- 

 sistently for a long enough period. 



ADAPTATIONS. No one can rightly appreciate 

 the theory of natural selection who does not 

 realise in some measure the universal occurrence 

 of those detailed fitnesses of structure and function 

 which are called adaptations. 1 The general idea 



1 We use the word adaptation to express a result achieved ; it is 

 sometimes used to express the process of reaching that result. 



