296 EVENINGS AT THE MICROSCOPE 



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 

 impediment; 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 observed, 

 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 movement The 

 mere elongation of the snout is no explanation of the dis- 

 appearance 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 fur- 

 ther progress can be made unless the hinder parts of the 

 body are, by contraction, drawn up toward 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 move- 

 ments. It presently begins to elongate and contract its 

 body vigorously, apparently alarmed at its unwonted posi- 

 tion; and the mucus is thrown off in copious abundance. 

 We apply a low microscopic power to it, and catch glimpses 

 now and again, as it writhes about, of a number of tiny 

 points protruded and retracted with rhythmical symmetry 

 through the skin. Its mobility precludes our discerning 

 much more than that these points are very numerous, that 



