13 



EARTHWORMS AND OTHER ANNELIDS 



LUMBRICUS TERRESTRIS 



Almost everywhere in England earthworms are found, but most 

 are absent from the very acid types of soil which botanists call 

 mor. They live usually in the upper layers of the soil in burrows, 

 the sides of which are lined with a slime secreted by unicellular 

 glands in the skin, and if the opening be not protected by a worm 

 cast it is usually closed by leaves or small stones. Such leaves 

 may often be seen sticking up from the ground, and will be 

 found to have been pulled into the burrow skilfully, with the 

 narrowest part foremost. At night, if the weather be warm and 

 not too dry, the worms will stretch themselves out of their holes, 

 keeping the hinder end of the body fixed in the opening, so that 

 they can pull themselves back at once if danger threatens. In 

 dry weather or hard frost they burrow deep and retire to a small 

 chamber, which they line with little stones. In wet weather they 

 are sometimes flooded out, but they rarely leave their burrows 

 in other circumstances, except when they are about to die owing 

 to the attacks of parasitic maggots which are the young of 

 certain flies. The food of earthworms consists of the organic 

 matter in the soil, which they swallow, and of leaves both fresh 

 and decaying. They will also eat animal matter, and are said 

 to be very fond of fat. Charles Darwin showed the remarkable 

 effects which these insignificant creatures have upon the surface 

 of the earth. By making the soil more porous they expose the 

 underlying rocks to the disintegrating action of water, by solution 

 owing to the presence of carbon dioxide and other acids of the 

 soil, and by frost ; and the small stones which eventually result 

 from this action are made still smaller by friction and solution 

 within their bodies. Thus they help in the formation of the soil. 

 At the same time they are aiding in its removal. Their castings 

 dry and crumble, and are blown about by the wind or else are 

 washed down by the rain. On sloping ground this fine material 

 tends to be carried away downwards, and thus the denudation 

 of hills is largely due to the action of earthworms. On the other 

 hand, their work is highly beneficial to the farmer. The soil is 

 by them thoroughly mixed, submitted to the action of the air, 



157 



