420 



FRESH-WATER BIOLOGY 



224 (200) Anterior end with fleshy collar and crown of spines. 



Echinostome cercariae 



225 



These cercariae develop in rediae which have collar, birth pore, arid posterior locomotor 

 appendages. They are characterized by the conspicuous collar and spines, also found in the 

 adult distome. The esophagus is long and the ceca reach to the posterior end of the body. 

 The tail is long and powerful. 



225 (228) Collar spines in a single, if sometimes slightly irregular row. 



226 



226 (227) Collar spines 42, rounded at both ends; excretory trunks doubly 



reflexed in cephahc region Cercaria biflexa Faust. 



Acetabulum in posterior third of body. Great number of cephahc glands in 2 series, 50 to 

 60 in each series, lateral to digestive ceca. Excretory tubes reflexed twice in cephahc region 

 prehminary to entering lateral trunks. Bladder long, with median swelling; scaleriform anas- 

 tomosis of excretory tubules in tail. Body length 0.45 to 0.5 mm., width 0.13 to 0.15 mm. Tail 

 about same length as body, powerful. Encysts within redia. Redia with "feet" in posterior 

 third of body. In liver tissue of Physa gyrina Say, near Buckhouse Bridge, Bitter Root River, 

 Montana. 



227 (226) Collar spines 36, acute at distal end; excretory trunks arising 



from triangular anastomosis in cephalic region. 



Cercaria trisolenata Faust. 



Deltoid anastomosis of tubules from 3 flame cells in cephalic region, preliminary to entering 

 lateral trunks. Excretory bladder obtruncate. Acetabulum spinose in posterior third of 

 body. Readily encysts in free state, easily drops tail. Body length 0.45 mm., width o.i mp. 

 Tail short, about 0.2 mm. Rediae with lateral "feet" about one-third distance from anterior 

 end. In Hver of Physa gyrina Say and Planorbis Irivolvis Say. Entire length of Bitter Root 

 River, Montana. 



228 (225) Collar spines in mature cercariae in two alternating rows; excre- 



tory trunks reflexed once 229 



229 (230) Excretory bladder long, attenuate; 43 equal spines. 



Cercaria rubra Cort 1914' 



Cysts large, spherical, thick- walled, transparent. Collar has forty-three 

 equal spines in two alternating rows; four spines on each side of mid- 

 ventral line point in. Encysted above gills in Canipeloma decisum, Hart- 

 ford, Conn. No redia found. Known only in encysted stage which is 

 really an Agamodistomum and not a Cercaria. 



Fig. 725. 



Cercaria rubra in Agamodistomum stage freed from cyst, ventra 

 view. X 130. (After Cort.) 



230 (229) Excretory bladder ovoid to depressed spheroid, excretory trunk 

 reflexed almost entire length 231 



