266 DARWINISM AND THE PROBLEMS OF LIFE 



The most familiar representative of the present stem 

 is the earth-worm. It is true that most people's 

 acquaintance with this animal is superficial, as its 

 subterraneous habits prevent more than a few from 

 knowing it thoroughly. For a long time, in fact, the 

 animal, which is not merely harmless but extremely 

 useful, was decried as injurious, and there are still 

 people who kill it whenever they find it. 



Darwin was the first to show that the earth-worms 

 are indispensable to the plants. He pointed out that 

 they act as ploughs in loosening the earth. The 

 animal feeds on the digestible elements in the soil. It 

 eats its way through them, as it were, passing them the 

 whole length of its alimentary canal, and then ejecting 

 them, which is always done on the surface. Thus the 

 finer constituents of the soil are constantly brought to 

 the top by the worms, and we have always good soil 

 there. The many passages that the worm leaves 

 behind it in its travels loosen the ground more and more, 

 and as they fall in, the elements of the soil rub together 

 and grind one another. Finally, leaves and other 

 bodies are drawn by the animals into their tubes, ground 

 up, and brought to the surface again. However strange 

 it may sound, we have to admit that the whole mass of 

 the fruitful surface of the earth has passed through 

 the alimentary canal of earth-worms, and passes through 

 the same process every few years. 



Man's attempts to trap the worm have, fortunately 

 for it, hardly any success. But the defenceless animal 

 has a good deal to suffer from other enemies. Besides 



