PARASITIC FLATWORMS 



395 



Q9 (loo) 



Oral sucker smooth; not provided with muscular papillae around 

 anterior end ' . . . Allocreadium Looss 1900. 



Esophagus long, not dividing until just before the acetabulum. Ex- 

 cretory bladder very short, ending at posterior margin of posterior testes. 

 Ovary spherical, lateral; vitellaria exclusively ventral. Cirrus and sac 

 rather short; prostate well developed. Genital pore median. Eggs 

 without filament, large (60 to 90 ij.) with light yellow shell. 



Intestine of fresh-watfr fishes. 



Several species from stomach and intestine of sheepshead, pumpkin- 

 seed, sturgeon, sucker, dace, minnow, and gall-bladder of red-finned min- 

 now. Collected in Great Lakes region. Lake Erie, Ontario; Lake 

 Sebago, Maine. Synopsis of genus by Walhn. 



Young forms of A. commune Olsson encysted in Mayfly nymph 

 {Blasturus cupidus Say) with eggs and Uving miracidia in body cavity 

 of nymph (Cooper). 



Representative American species. 



Allocreadium lohatum Wallin 1909. 



Length 4 to 7 mm., breadth i to r.5 mm. Suckers equal, 0.46 to 0.5 

 mm. in diameter. No prepharynx; pharynx 0.24 to 0.3 mm. long by 

 0.22 mm. broad. 



Testes lobed; cirrus sac extends to center of acetabulum. Ovary 

 spherical; vitellaria postovarial, profuse, confluent behind posterior 

 testis. Receptaculum large, pyriform, between ovary and anterior testis. 

 Uterus compact, between anterior testis and acetabulum. Eggs very 

 nmnerous, 67 to 85 11 long by 46 to 57 11 broad. 



Fig. 683. Allocreadium lobatum. Uterus indicated by dotted area, 

 added from slide. X I9- (After Wallin.) 



100 (99) Six oral papillae surround anterior end. 



101 (102) Genital pore anterior to fork of intestine. 



Crepidostomum Braun 1900. 



Bifurcation of intestine just anterior to acetabulum. Excretory bladder 

 elongate. Cirrus sac muscular; pore anterior to fork of intestine; testes 

 large, round, median, halfway from acetabulum to posterior end. Vitel- 

 laria confluent behind testes. Uterus short, with few eggs, between ace- 

 tabulum, ovary, and anterior testis. In intestine of fresh-water fishes. 



Several species not adequately described. 



Representative American species. 



Crepidostomum cornutum (Osbom) 1903. 



Probably the best known species in the North American fauna is C. 

 cornutum (Osborn) from the stomach and pyloric ceca of black bass, rock 

 bass, channel cat, perch, sunfish, darter, etc. Immature forms encysted in 

 viscera of various crayfish, Ontario, Canada. The worm manifests pre- 

 cocious sexual maturity as the larger cysts contain many eggs akeady ex- 

 truded. Very young forms have been taken from Mayfly nymphs (Hexagenia) 

 by Cooper. 



Fig. 684. Crepidostomum cornutum. Ventral view; compressed. 

 Osborn.) 



X 20. (After 



