THE FACTORS OF ORGANIC EVOLUTION. 115^ 



the substance of Mr. Spencer's most telling argument 

 against Mr. Darwin's theory that accidental variations, 

 if favourable, would accumulate and result in seemingly 

 adaptive structures. Mr. Spencer well shows that 

 luck or chance is insufficient as a motive-power, or 

 helm, of evolution ; but luck is only absence of design ; 

 if, then, absence of design is found to fail, it follows 

 that there must have been design somewhere, nor can 

 the design be more conveniently placed than in asso- 

 ciation with function. 



Mr. Spencer contends that where life is so simple' 

 as to consist practically in the discharge of only one 

 function, or where circumstances are such that some 

 one function is supremely important (a state of things, 

 by the way, more easily found in hypothesis than in 

 nature — at least as continuing without modification 

 for many successive seasons), then accidental variations, 

 if favourable, would indeed accumulate and result in 

 modification, without the aid of the transmission of 

 functionally produced modification. This is true ; it 

 is also true, however, that only a very small number 

 of species in comparison with those we see around us 

 could thus arise, and that we should never have got 

 plants and animals as embodiments of the two great 

 fundamental principles on which it is alone possible 

 that life can be conducted,* and species of plants and 

 animals as embodiments of the details involved in 

 carrying out these two main principles. 



If the earliest organism could have only varied 

 favourably in one direction, the one possible favour- 



* See concluding chapter. 



