'THE ORIGIN OF SPECIES* 89 



work a modifying influence of the kind they assign as 

 the cause of these specific differences, an influence 

 which, though slow in its action, does in time, if the 

 circumstances demand it, produce marked changes ; an 

 influence which, to all appearance, would produce in the 

 millions of years, and under the great varieties of 

 condition which geological records imply, any amount 

 of change.' 



This admirable passage, written seven years before the 

 publication of the ' Origin of Species,' contains explicitly 

 almost every idea that ordinary people, not specially 

 biological in their interests, now associate with the 

 name of Darwin. That is to say, it contains, in a very 

 philosophical and abstract form, the theory of ' descent 

 with modification' without the distinctive Darwinian 

 adjunct of ' natural selection' or ' survival of the fittest.' 

 Yet it was just that particular lever, dexterously applied, 

 and carefully weighted with the whole weight of his 

 endlessly accumulated inductive instances, that finally 

 enabled our modern Archimedes in so short a time to 

 move the world. The public, that was deaf to the high 

 philosophy of Herbert Spencer, listened at once to the 

 practical wisdom of Charles Darwin. They did not care 

 at all for the a priori proof, but they believed forthwith 

 as soon as a cautious and careful investigator laid bare 

 before their eyes in minute detail the modus operandi of 

 nature herself. 



The main argument of Darwin's chief work runs 

 somewhat after the following fashion l : 



1 The reraainder of the present chapter, which consists almost 

 entirely of an exposition of the doctrine of natural selection, may 

 safely be skipped by the reader already well acquainted with the 

 9 



