380 EVOLUTION, GENETICS, AND EUGENICS 



rocks, the mosses form huge sponges on the moors which keep the 

 streams flowing in days of drought. Many little plants are forever 

 smoothing away the wrinkleson the earth's — their mother's — face, and 

 they adorn her with jewels. Others that have formed coal have enriched 

 her with ages of entrapped sunlight. The grass — which began to 

 appear in Tertiary ages — protects the earth like a garment; the 

 forests affect rainfall and temper climate, besides sheltering multitudes 

 of living things, to many of whom every blow of the axe is a death- 

 knell. No plant, from bacterium to oak-tree, lives or dies to itself, 

 or is without its influence upon the earth. So among animals there 

 are destructive borers and burrowers and conservative agents, such 

 as the coral-polyps and the chalk-forming Foraminifera. 



Practical importance of a realisation of the web of life. — What 

 has Darwinism to do with human life ? The answer at this stage in 

 our inquiry is clear: we must respect the web of life if we wish to 

 master Nature. She must be humoured, not bullied. Emerson 

 included in his vision of a perfected earth the absence of spiders, but 

 the absence of spiders — which snare so many injurious insects — would 

 mean the absence of much else, man probably included. In a northern 

 county in Scotland the proprietors were justly annoyed at the injuries 

 inflicted on young trees by squirrels, and they formed a squirrel club, 

 setting a price on the beautiful rodent's head. Perhaps a wiser course 

 would have been to begin by inquiring what disturbance of the balance 

 of nature had allowed the squirrels to multiply so disastrously. But, 

 after a period of squirrel-slaughter and some jubilation thereat, a 

 cloud began to rise in the sky. The wood-pigeons were multiplying 

 worse than ever, and the farmers, at least, said with no uncertain voice 

 that they preferred the squirrels. An imperfect recognition of the 

 web of life had left out of account the notable fact that squirrels 

 destroy large numbers of young wood-pigeons. 



One of the hopeful symptoms of the last few years is the reawaken- 

 ing of an interest in woods and forests. Everyone knows how terribly 

 these have been wasted, and how the disastrous results have affected 

 rainfall and irrigation, climate and crops, and even the character of the 

 people. Here what was once a pleasant stream is now like a gravelly 

 road, and there the fertile plains are flooded ; here the wind is sweeping 

 away the soil, and there both beauty and health have departed. The 

 birds which the woods once sheltered are driven elsewhere, and the 

 insect-pests are rife among the crops. For "the cheapest and most 

 effective insecticides are birds." 



