WHAT WE OWE TO DARWIN 11 



taken from a bird's foot. Long nutritive chains 

 bind the bracken on the hill-side to the brain 

 of the proprietor if he is fond of eating trout. 

 The patent-leather shoes on his feet connect him 

 with the melancholy slaughter of seals, while 

 his ivory-backed toilet-brushes implicate him in 

 the passing of the elephant. There is a ceaseless 

 circulation of matter and energy. All things 

 flow. Influence passes from A. to Z., though 

 Z. is quite unaware of A. What ripples spread 

 and spread from the introduction of rabbits into 

 Australia, or of sparrows into the United States, 

 or of the mongoose into Jamaica ! What abso- 

 lutely essential connections there are between 

 cutting down trees and a plague of insects, between 

 birds and seed-scattering, between sunlight and 

 the catches of mackerel ! 



Take an instance from " The Origin of Species " : 

 " If certain insectivorous birds were to decrease 

 in Paraguay, the parasitic insects would probably 

 increase ; and this would lessen the number of 

 navel-frequenting flies then cattle and horses 

 would become feral, and this would certainly 

 greatly alter (as indeed I have observed in parts of 

 South America) the vegetation ; this, again, would 

 largely affect the insects ; and this, as we have just 

 seen in Staffordshire, the insectivorous birds, and 

 so onwards in ever-increasing circles of complexity." 



(II) THE STRUGGLE FOR EXISTENCE. What do 

 we owe to Darwin ? In the second place, we may 

 rank his realisation of " the struggle for exist- 

 ence." From Aristotle to Lucretius, from Buffon 

 to Robert Chambers, there had been allusion to 

 the struggle for existence in nature, and every one 

 knows, for instance, how it recurs repeatedly in 



