2 GO EVENINGS AT THE MICROSCOPE. 



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 coining 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 

 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? Xo 

 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 1 Why, when the muscles contract, does not 

 the taper, wedge-like muzzle slip back, and lose the 

 ground it had gained 1 



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

 put it into 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 

 position ; and the mucus is thrown off in copious abund- 

 ance. 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 great regu- 

 larity, through the skin. Its mobility precludes our 

 discerning much more than that these points are very 

 numerous, that they are arranged in four longitudinal 

 lines, running along the ventral side of the animal, — two 

 lines on each side, — and that in each line there is a point 

 protruded from each of the many rings of which the 

 Worm's body is made up. 



In order to see a little more of these organs we must 

 sacrifice a Worm ; having killed it, and divided the body 

 in the middle, I cut off, with sharp scissors, a small 

 transverse portion, say two or three rings, and press the 



