THE FA CTORS OF .ORGA NIC E VOL UTION. 1 1 1 



and even species, but considers these causes if taken 

 alone as no less insufficient to account for observable 

 facts than the theory of functionally produced modifi- 

 cations would be if not supplemented by inherit- 

 ance of so-called fortuitous, or spontaneous variations. 

 The difference between Dr. Erasmus Darwin and Mr. 

 Spencer does not consist in the denial by the first, 

 that a variety which happens, no matter how acci- 

 dentally, to have varied in a way that enables it to 

 comply more fully and readily with the conditions of 

 its existence, is likely to live longer and leave more 

 offspring than one less favoured; nor in the denial by 

 the second of the inheritance and accumulation of 

 functionally produced modifications, but in the amount 

 of stress which they respectively lay on the relative im- 

 portance of the two great factors of organic evolution, 

 the existence of which they are alike ready to admit. 



With Erasmus Darwin there is indeed luck, and' 

 luck has had a great deal to do with organic modifica- 

 tion, but no amount of luck would have done unless 

 cunning had known how to take advantage of it ; 

 whereas if cunning be given, a very little luck at a 

 time will accumulate in the course of ages and become 

 a mighty heap. Cunning, therefore, is the factor on 

 which, having regard to the usages of language and 

 the necessity for simplifying facts, he thinks it most 

 proper to insist. Surely this is as near as may be the 

 opinion which common consent ascribes to Mr. Spencer 

 himself. It is certainly the one which, in supporting 

 Erasmus Darwin's system as against his grandson's, 

 I have always intended to support. With Charles 



