PARASITIC FLATWORMS 



413 



181 (182) Body dark brown, or blackish. 



Cercaria hyalocauda Haldeman 1842. 



Very imperfectly known. The form described under this name by Evarts (1880) has a body 

 0.47 mm. long and 0.24 mm. wide with a tail 0.55 mm. long and o.i mm. wide in maximum. 

 Cyst 0.32 mm. in diameter. Body dark brown or blackish. Two eye spots and smaller, less 

 distinct pigment mass between. Tail semitransparent, corrugated when contracted, active 

 long after detachment from body. 



^ Eyarts' description of the Uving organism shows it is much Uke C. urbanensis though easily 

 distinguishable by greater size of larva and cyst. Haldeman's account is entirely inadequate 

 to differentiate the form and suifices only to place it in this group. Taken in numbers from 

 P'hysa keterostropha Say by Evarts. 



182 (181) Body white. Doubtful form. 



Cercaria (Glenocercaria) lucania Leidy 1877. 



Length 0.5 mm. White, ovoid, with conical tail equal to or longer than body and frequently 

 moniliform. Two eyes with intermediate black pigment spot and smaller scattered pigment 

 spots near them. Produced in bright orange-colored sporocysts which are cylindrical and 

 bluntly rounded at the ends. Leidy calls this a Monosloma, and all data given agree with 

 that conclusion except that his description Usts an acetabulum which would make it a dis- 

 tome cercaria. Abundant in Planorbis parvus found near Philadelphia, Pa. 



183 (174) More than one sucker 184 



184 (250) Oral sucker well developed; genital atrium not modified. . 185 



185 (190) Second sucker ventral and at posterior end of body. 



Amphistome cercariae. 



186 



According to studies on European species the cercaria of Paramphistoma cervis lacks pockets 

 in the oral sucker and has a connection between the longitudinal excretory vessels. It belongs 

 to one subfamily. All other known cercariae in this group belong to another subfamily. 

 They have the pockets in the oral sucker and a muscular enlargement of the esophagus at 

 the bifurcation of the intestinal crura. 



186 (189) Cercariae separate, not attached in bunches. 



.... 187 



Very likely one of the species described below is the larval form of Diplodiscus temperatus 

 Stafford, see 57 (58) in this key. 



187 (188) Anterior half of body pigmented. . Cercaria inhahilis Cort 1914. 



Large, pigmented form, sluggish in movement. Swims slowly in open 

 water, does not progress on substratum. Two large eye spots with lenses. 

 Cystogenous glands thickly developed both dorsally and ventrally. Tail 

 lightly attached above acetabulum and easily lost. Location of genital or- 

 gans distinctly indicated by four dense masses of nuclei connected by fine 

 lines. 



From Planorbis trivolvis, Lawrence, Kan., and XJrbana, 111. 



Fig. 714. 



Cercaria inkabilis, mature, ventral view. Cystogenous glands not shown. 

 X 44. (After Cort.) 



