PARASITIC FLATWORMS 



419 



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



Cercariae ornatae 



219 



219(220) Eye spots present Cenaria raconosa FausL 



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, 

 e.xtending around acetabulum. Excretory tubules multi-dendritic. Tail with lateral rulUcd 

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

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



220(219) Eye spots lacking 221 



221 (222) Stylet small, without thickened region. 



Cercaria hemiloplmra Cort 19 14. 



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. (Jral 

 sucker 0.065 mm., acetabulum 0.049 mm. 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. C ystoRenous f^lands not 

 shown. X 80. b, stylet, side view. X 2yo. (.\fter Cort.) 



222 (221) Stylet heavy Cercaria platyura Lcidy 1S90. 



Length 0.8 mm., body 0.4 by 0.12 mm., 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 heav-y 

 stylet. Acetabulum 0.06 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. 



Tail short, stumpy, with F>owerfulIy developed muscles. 

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

 the Cotylocercous cercariae of Dollfus 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 Xorth 

 America. 



Cercaria trigouura Cort 191 4. 



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

 long by 0.024 mm. wide. Oral sucker 0.049 mm. long by 

 0.039 Tirn- wide. Acetabulum just back of center of 

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

 spines. Tail sht)rt, blunt, easily detached, triangular, 

 folded into groove. Just anterior i)n)minent gland ojx'n- 

 jng into the head of this groove. Stylet dorsid to oral 

 sucker. Stylet glands small but numerous. Elxcretory 

 system bicornuate, thick walled. Free in tissues of 



■ Tf,^ n ■ . ■ 1^1 snails; rediae in s;ime host. No tcndenc>' to encyst 



Fig. 724. Cercarta trtqonura.la.teTa.1 =""•". 



and ventral views. X 170. Each with noted. . i, rj#- 



stylet. X 400. (After Cort.) Found in Campdoma dcctsum from Ilartford. C uon. 



