WORMS. 



273 



one merges, at its upper end, into a sort of blade, which 

 is slightly bent, and which tapers to an exceedingly fine 

 point. But its chief peculiarity is that the blade has a 

 double edge, not like a two-edged sword, the edges set on 

 opposite faces, but on the same face, set side by side, 

 with a groove between them ; and each edge is cut with 

 the most delicate and close-set teeth, the lines of which 

 pass back upon the blade, as in our sickles. 



PrSHIJfG FOLKS OF 8ERPVLA. 



These pencils of spear-like bristles are the organs by 

 which the protrusion of the animal is performed. Their 

 action is manifestly that of pushing against the walls of 

 the interior, which on close examination are seen to be 

 lined with a delicate membrane, exuded from the animal's 

 skin. The opposite feet of one segment protrude the pen- 

 cils of bristles, one on each side, the acute points and 

 teeth of which penetrate and catch in the lining membrane ; 

 the segments behind this are now drawn up close, and ex- 

 tend their bristles ; these catch in like manner ; then an 

 elongating movement takes place ; the pencils of the 

 anterior segments being now retraced, they yield to the 

 movement and are pushed forward, while the others are 

 held firm by the resistance of their holding bristles ; thus 

 gradually the foreparts of the animal are exposed. 



But this gradual process would ill suit the necessity of a 

 creature so sensitive to alarm, when it wishes to retreat. 

 We have already seen how, with the fleetness of a thought, 

 its beautiful crown of scarlet plumes disappears within its 



T 



