76 THE ORIGIN OF SPECIES n 



operation which can be effected by Nature, for man 

 interferes intelligently. Reduced to its elements, 

 this argument implies that an effect produced with 

 trouble by an intelligent agent must, a fortiori, be 

 more troublesome, if not impossible, to an unin- 

 telligent agent. Even putting aside the question 

 whether Nature, acting as she does according to 

 definite and invariable laws, can be rightly called 

 an unintelligent agent, such a position as this is 

 wholly untenable. Mix salt and sand, and it shall 

 puzzle the wisest of men, with his mere natural 

 appliances, to separate all the grains of sand from 

 all the grains of salt ; but a shower of rain will 

 effect the same object in ten minutes. And so, 

 while man may find it tax all his intelligence to 

 separate any variety which arises, and to breed 

 selectively from it, the destructive agencies inces- 

 santly at work in Nature, if they find one variety 

 to be more soluble in circumstances than the other, 

 will inevitably, in the long run, eliminate it. 



A frequent and a just objection to theLamarckian 

 hypothesis of the transmutation of species is based 

 upon the absence of transitional forms between 

 many species. But against the Darwinian hypo- 

 thesis this argument has no force. Indeed, one of 

 the most valuable and suggestive parts of Mr. 

 Darwin's work is that in which he proves, that 

 the frequent absence of transitions is a necessary 

 consequence of his doctrine, and that the stock 

 whence two or more species have sprung, need in 



