PHYLUM ANNELIDA 



211 



in tubes which they make from secretions and bits of foreign 

 substances, such as sand (Fig. 84, E), lime (A, D), and mucous 

 secretions (F). Many of the tube-building species have 

 gills on the head, and when these are brightly colored they 

 often make tne bottom of the ocean look like a flower garden. 

 Some polychsetes have the dorsal surface covered with 

 spines or protective plates (C). 



CLASS 2. HIRUDINEA 



Leeches (Fig. 85), are found in fresh water, on land, and to 

 some extent in the ocean. They are without setae but have 



A B C o E 



FIG. 85. Leeches. A, attached to a turtle's leg; B, swimming; C, hiding 

 beneath a rock and protruding proboscis to catch an insect larva; D, an adult 

 carrying young attached to its ventral surface; E, egg cocoons. 



a sucker at either end. The rings on the outside of the 

 body are much more numerous (70 to 100) than the body 

 metameres (33) . On account of the thickening and distor- 

 tion of the septa, the metamerism within the body is ob- 

 scured; in fact, is not apparent except in the excretory and 

 nervous systems. The ccelom is small when compared 

 with that of chsetopods. 



The anterior sucker of a leech contains the mouth, but 

 the one at the posterior end is merely an adhesive disc, and 

 the anus opens in front of it on the dorsal side- Leeches 



