CH^ETOPODA 449 



F. Food. 



This manner of motion at first sight seems very wonderful (reminding 

 one- of the fairy legend of the Castle of Indolence), but in reality is not 

 at all strange when we consider that the food of the earth-worm con- 

 sists of animal and vegetable substances which are contained in the 

 soil, and for the purpose of obtaining which it is obliged constantly to 

 fill its intestine with earth. For this reason, too, the earth-worm 

 always selects for its habitat a soil which is rich in humus. The leaves, 

 blades of grass, etc., also, which at night it drags down into its runs, 

 form after they have decayed a very acceptable nutriment. 



G. Sense Activities. 



If a worm is surprised while visiting the surface of the soil, even the 

 slightest tremor of the ground is sufficient to make it escape rapidly 

 into its hole. This points to the possession of a very fine tactile sense. 

 Again, though eyes are absent, as is the case in most animals living 

 underground, the earth-worm is not insensitive to light, for if the light 

 of a lantern be thrown upon it it at once retreats. It is evidently also 

 endowed with taste and smell, for it shows a decided preference for certain 

 kinds of food (cabbage-leaves, carrots, etc.), and knows where to find 



these, even from a considerable distance. 







H. Reproduction. 



Eeproduction takes place by eggs ; these are surrounded by a mucous 

 envelope, which hardens on exposure to air. This mucus is secreted by 

 glands situated on a number of rings at the end of the anterior third of 

 the body, causing a considerable swelling of this region, which is known 

 as the "clitellum." 



I. Importance of the Earth-Worm in the Economy of Nature. 



The important part played by this despised creature in the economy 

 of Nature will be evident from its mode of life. We saw how daily it 

 takes into its body a small portion of the rich, humus-laden soil, and 

 again discharges the undigested remainder upon the surface. When 

 we next reflect that even in a small garden the same thing is done by 

 thousands of worms, we shall understand how in the course of only a 

 few years the whole top covering of mould must pass through the 

 intestines of these tiny creatures, while in the course of millions of years 

 this must have occurred thousands of times. The feeble worms slowly 

 carry the lower strata of the soil to the surface, and cause the upper 





