162 THE BOOK OF NATURE STUDY 



Shape. The body is for the most part cylindrical in shape, 

 and is marked out by a number of circular grooves into a corre- 

 sponding number of rings or segments, which closely resemble 

 one another. At the anterior end the segments become gradually 

 of less diameter, so that the head extremity is finely tapered. 

 This shape is of great service, for the sharply pointed tip is able 

 to insinuate itself into extremely narrow crevices in the soil, and 

 thus to bore a hole into which the rest of the body can pass without 

 difficulty. On the other hand, the posterior end is flattened 

 considerably, so as to be wider from right to left than any other 

 portion of the body. The value of this modifica- 

 tion will readily be appreciated if an attempt be 

 made to catch worms in the manner suggested 

 above. At such times worms are to be seen in 

 hundreds stretched out between the blades and 

 roots of the grass ; but they are not completely 

 -Ct outside their burrow, their broad tails are within 

 IG 'oTter^nai * ts sne ^ er ^ an d maintain a firm pressure to right and 



segments of left upon its walls. Thus they are securely anchored, 



earthworms, a, an d a t the least alarm dart backwards into safety 



with the rapidity of stretched elastic. Their safety 



thus depends upon the tail being sufficiently wide to allow secure 



grip upon the lateral walls of the tunnel. 



Breeding. The body of an adult worm is swollen and thickened 

 at a spot about one quarter of the total length from the front 

 end. The exact position of this thickening differs in different 

 species, but it usually begins near the soth segment and extends 

 over about six segments behind this. The enlargement is popularly 

 supposed to be a scar marking the place where the body has 

 reunited after accidental bisection by a spade. Its true function, 

 however, is concerned with the act of pairing. Subsequently the 

 skin of this region produces a girdle of tough slime completely 

 encircling the body, and thus resembling in shape a cask with 

 both ends knocked out. Out of this girdle the worm wriggles 

 backwards, and deposits within its cavity its own eggs and the 

 fertilising male element received from another worm. When at 

 length the worm has completely withdrawn its head from the 

 girdle the two open ends of the latter close up owing to their 



