SOME AQUATIC WORMS, ETC. 1 73 



CHAPTER VII. 



SOME AQUATIC WORMS, CH^TONOTUS, AND CHIRONO- 

 MUS LARVA. 



The collector of microscopical objects from the 

 ponds and slow streams is doubtless familiar with the 

 appearance of the bristle-bearing worms (Fig. 153), 

 on account of their general resemblance to those 

 long-suffering creatures which he in his youth impaled 

 on a hook and with them sought the nearest water. 

 The extensive bristles of the aquatic worms are an 

 addition which greatly lessen their resemblance- to the 

 common earth-worm, and their transparency is another 

 characteristic. that may temporarily mislead the ob- 

 server, but their elongated bodies and general worm- 

 like aspect tell the story. 



In addition to the bristles which most members of 

 this class possess, there are usually two or more rows 

 of long, curved spines (Fig. 154), on the ventral or 

 lower surface. These can be protruded or withdrawn 

 into the body at the possessor's will, and when pro- 

 truded are used to assist the worm to crawl. They 

 are therefore called the podal spines or foot-spines. 

 They may not be noticed when retracted unless spec- 

 ially searched for, but having observed them and the 

 bristles in a row on each side above them, the student 



