354 GENERAL SCIENCE 



the length of the body. The body is shortened by the 

 contraction of the muscles running lengthwise and 

 lengthened by the contraction of the circular muscles. 

 In moving the worm extends its head and then shortens 

 its body by contraction of the longitudinal muscles. 

 Why doesn't the head slip back as these muscles 

 contract ? 



Examine the under surface of an earthworm with a good 

 lens. How are these anchors used? The worm has no 

 eyes, yet it is quite sensitive to light. How can you test 

 it to determine whether it likes light or darkness? 



MOUT 



FIG. 316. The Food-tube of an Earthworm. 



These worms get their food from plants and from .the 

 soil which passes through their bodies. They are able to 

 burrow into very hard soil. This they do by literally 

 eating their way through (Figure 316). 



The earthworm has a nervous system with a well- 

 developed sense of touch. It also has a blood circulation. 

 It has no lungs, the skin acting as an organ of breathing. 

 To facilitate the passage of air (osmosis) the skin of the 

 worm is kept moist by a secretion. During heavy rains 

 the worms often come to the surface, because as the ground 

 becomes soaked they are covered with water and cannot 

 get sufficient oxygen. There are many other kinds of 

 worms, but the earthworm is typical of the whole class. 



We must be careful not to confuse caterpillars, grubs, 

 and similar larvae with worms. Worms retain their 



