THE EARTHWORM AND ANNELIDS IN GENERAL 191 



number of small spaces. Leeches are usually aquatic, hermaph- 

 rodite, and have a direct development. Figure 99 shows a 

 common representative of this class. 



FIG. 98. A ma- 

 rine Polychaet, 

 Nereis. (From 

 Shipley and 

 MacBride, af- 

 ter Oersted.) 



FIG. 99. A leech, Hirudo 

 medicinalis. i, mouth; 

 2, posterior sucker; 3, 

 sensory papillae. (From 

 Shipley and MacBride.) 



