EXCRETORY SYSTEM IN DIGENEA. 337 



Sporocyst simple, sausage-shaped sac. 



Prepharynx and pharynx simple; esophagus moderately long; 

 ceca typically furculate. Mucin glands two pairs, opening 

 through long ducts at sides of oral atrium. 



Excretory bladder small; collecting tubules swollen at base; 

 three pairs of flame cells with capillaries opening into each col- 

 lecting tubule, one flame cell of posterior couplet running back 

 into tail. 



Mass of germ cells just anterior to bladder. 



Cercaria robusticauda nov. spec. (Fig. 7.) 



Systematic position : furcocercous larva. 



Parthenita : sporocyst. 



Host : Physa gyrina Say. 



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



1918. 

 Flame-cell formula: a + /3 + 7 + # = 1+2+2+2 or 7. 



Minute forked-tailed cercaria with body 75 /j, in length by 25 ju 

 in width, tail trunk equally long, but with short, stubby furci. 

 Oral sucker 12 /j. in diameter, directed forward; ventral sucker 

 equal in diameter, somewhat back of middle of body, with two 

 concentric rings of spines. Blunt spines covering anterior third 

 of body. Eye-spots wanting. Morphological pharynx de- 

 generate, with glandular instead of muscular cells; esophagus 

 leading into furci which meander to posterior margin of acetabu- 

 lum. Mucin glands about six on each side, homogeneous in 

 character, opening through single ducts at each side of the oral 

 aperture. 



Excretory bladder bicornuate, with single collecting tubule 

 running into cornu on each side. Flame cells based on four-unit 

 plan, with a single cell in the anteriormost unit and a pair in each 

 of the succeeding three. 



Germ cells, consisting of a loose aggregate, in front of the 

 bladder. 



Cercaria quattuor-solenata nov. spec. (Fig. 8.) 



Systematic position: furcocercous larva. 

 Parthenita: sporocyst. 



