EXCRETORY SYSTEM IN DIGENEA. 335 



Flame-cell formula: a + /3 n = 3 + 12 or 15. 



Body 0.36 mm. long by o.io mm. wide; tail 0.36 mm. long by 

 35 fj. in diameter at base. Oral sucker 35 /j. in diameter, acetab- 

 ulum 50 fj, in diameter. Entire ventral surface of body between 

 pharynx and acetabulum sunken into elongate bowl-like sucking 

 organ. Collar spines 38, disposed in two alternating rows. 



Redia with conspicuous "feet," rhabdoccel gut, collar prom- 

 inence and birthpore. 



Prepharynx short; pharynx urn-shaped; esophagus long, capil- 

 lary; furci distended, extending to posterior tip of body. Mucin 

 glands six, with ducts tipped with piercing spines. 



Excretory tubules with double flexure; 15 flame cells along 

 the entire length of the tertiary portion. 



Cercaria trifurcata nov. spec. (Fig. 5.) 



Systematic position: stylet larva. 



Parthenita: sporocyst. 



Host : Physa gyrina Say. 



Habitat and time of collection: drainage ditch, Urbana, 111., 



1918. 



Flame-cell formula: a + ft' + a." + /3" + 7" = 3 + 3 + 3 + 3 

 + 3 or 15. 



Body 0.43 mm. long by 0.2 wide in region of acetabulum; tail 

 0.43 mm. long by 50 ju in diameter at base, fluted laterally in 

 distal half. Entire body covered with minute spines. 



Sporocyst consisting of elongate compound branches. 



Acetabulum 60 /j. in diameter; weak and ineffective; oral 

 sucker 76 /j, in diameter, directed anteriad. Prepharynx pro- 

 vided with great mass of secretory glands; pharynx and eso- 

 phagus present but inconspicuous; ceca broad sacculate pouches 

 extending some distance behind the acetabulum; mucin glands 

 several, in vitiform cluster, with granular contents, emptying 

 through long ducts at sides of stylet. 



Bladder small, crenate; main collecting tubule Y-form; 

 anterior collecting tubule of each half of body with two triplet 

 groups of flame cells and posterior collecting tubule with three 

 triplet groups of flame cells. 



