PARASITIC FLATWORMS 



4ig 



2i8 (223) Tail provided with fin-like fold, but of normal length. 



Cercariae ornatae 



219 



Cercaria racemosa Faust. 



219 (220) Eye spots present 



Body length 0.29 mm., width o.ii mm. Tail 0.22 mm. in length by 0.04 mm. wide at base. 

 Body ovate, oral sucker small, acetabulum somewhat smaller. Esophagus long, ceca short, 

 extending around acetabulum. Excretory tubules multi-dendritic. Tail with lateral rulBed 

 fin-folds. Stylet delicate, attenuate. In polygonal sporocysts in liver of Lymnaea proxima 

 Lea, sloughs of Bitter Root River, Fort Missoula, Montana. 



220 (219) Eye spots lacking 221 



221 (222) Stylet small, without thickened region. 



Cercaria hemilophura Cort 191 4. 



Body oval, 0.38 mm. long, 0.14 mm. wide, densely covered with 

 small spines. Tail about length of body, extensile to double body 

 length, with fin half as wide along ventral surface of distal half. Oral 

 sucker 0.065 nim., acetabulum 0.049 ^rn. in diameter. Stylet small 

 without thickened region. 



Produced in orange-colored, elongate and non-branching sporocysts, 

 much twisted together. In Physa gyrina from Rockford, Illinois 



Fig. 723. Cercaria hemilophura; a, ventral view. Cystogenous glands not 

 shown. X 80. i, stylet, side view. X 290. (After Cort.) 



222 (221) Stylet heavy Cercaria platyura Leidy 1890. 



Length 0.8 mm., body 0.4 by 0.12 ram., tail 0.36 by 0.06 mm. at base, width with mem- 

 branous alae 0.14 mm. Body ovoid, head rounded, oral sucker large (0.08 mm.) with heavy 

 stylet. Acetabulum o.o5 mm. Tail nearly as long as body, stout, tapering, corrugated, 

 with broad, costate, lateral membrane. 



Taken free in a pool with Lymnaea, at Fort Bridger, Wyo. 



223 (218) Tail short and peculiarly modified. 



Microcercous cercariae. 



Fig. 724. Cercaria Irigonura, lateral 

 and ventral views. X 170. Each with 

 itylet. X 400. (Alter Cort.) 



Tail short, stumpy, with powerfully developed muscles. 

 Not a swimming organ, but used as a prop or lever. In 

 the Cotylocercous cercariae of DoUfus the organ is still 

 further modified into a type of sucker. This latter group 

 develops in sporocysts and is mostly marine. 



Only species thus far recorded in North 

 America. 



Cercaria trigonura Cort 1914. 



Body 0.24 mm. long, 0.06 mm. wide. Tail 0.05 mm. 

 long by 0.024 mm. wide. Oral sucker 0.049 n^^i^- long by 

 0.039 Dini. wide. Acetabulum just back of center of 

 body, 0.04 mm. in diameter. Cuticula covered with fine 

 spines. Tail short, blunt, easily detached, triangular, 

 folded into groove. Just anterior prominent gland open- 

 ing into the head of this groove. Stylet dorsal to oral 

 sucker. Stylet glands small but niunerous. Excretory 

 system bicomuate, thick walled. Free in tissues of 

 snails; rediae in same host. No tendency to encyst 

 noted. 



Found in Campehma decisum from Hattfotd, Gnu. . 



