WORMS. 299 



particles of soil to adlicre together, and tlicn to form a 

 cj'lindrical wall, of which tliej are the bricks, and the 

 slime the mortar; and also of greasing, as it were, the 

 whole interior of the burrow or passage thus made, so 

 that the Worm can travel to and fro in it without im- 

 pediment ; while the fact that the slime is continually 

 poured forth afresh prevents the least atom of earth from 

 adhering to its body. This you have doubtless ob- 

 served, or may observe in a moment, if you will take 

 the trouble to thrust a spade into the ground and give 

 it two or three shakes. You will presently see on all 

 sides the alarmed Earth-worms coming swiftly to the 

 surface, and will notice how perfectly sleek and clean 

 they are. 



But these contrivances are only accessories : we 

 have not yet discovered the secret of the easy move- 

 ment. The mere elongation of the snout is no exolana- 

 tiou of the disappearance of the Worm in the burrow ; 

 for you will naturally and reasonably say that this 

 elongation cannot extend beyond a certain limit; and 

 what then ? No further progress can be made unless 

 the hinder parts of the body are, by contraction, drawn 

 up towards the elongated front ; — but what holds the 

 front in place meanwhile? Why, when the muscles 

 contract, does not the taper, wedge-like muzzle slip 

 back and lose the ground it had gained ? 



This we will now look at. I take up this Worm 

 and put it in a narrow glass cell, where we may watch 

 its movements. It presently begins to elongate and 

 contract its body vigorously, apparently alarmed at its 

 unwonted j^osition ; and the mucus is thrown off in co- 

 pious abundance. We api>ly a low microscopic jjower 

 to it, and catch glimpses, now and again, as it writhes 



