The Web of Life. 67 



the sparrow pest in the United States — and yet we are slow to 

 learn. The introduction of new organisms into new surroundings 

 is always dangerous and almost every ruthless elimination is to be 

 viewed with the gravest suspicion. Even as regards flies and rats, 

 it has to be remembered that their extreme abundance is the 

 nemesis of crude or careless ways of disposing of waste. The 

 ruthless destroyer of woods and forests, who fells or burns without 

 replacing, is an enemy of mankind ; and so is the exterminator of 

 birds. " Ignorance of nature," it has been well said, " is costly, 

 by disturbing the balance of nature, man has introduced foes into 

 his own household." Whether it be voles or weeds, the getieral 

 idea is the same, we should be slow to call any introduction of the 

 new (;r elimination of the old unimportant. In no case should 

 any such step be taken without consulting naturalists who have 

 an expert understanding of the web of life. 



Theoretically, also, the idea of the web of life is of the utmost 

 importance. For as Darwin clearly discerned, survival in the 

 struggle for existence is not at random but is definitely related 

 to the already established system of linkages, to all sorts of inter- 

 dependences and solidarities. The texture of the web of life is so 

 fine that even an apparently trivial new quality may be vital to the 

 situation. The sifting that goes on is, because of the web of life, 

 in definite relation to what has been already established. The 

 character of the edifice that has been erected determines the 

 characters of the additions made to it. Evolution is no chapter 

 of accidents, but an onward progressing melody. 



