

PARASITIC FLATWORMS 447 



armed with strong hooks. Female glands single, median; two vaginae. Eggs with three 

 membranes. 



The type species, D. laems, from various ducks and geese found in North America. No 

 record of any species on this continent. 





FIG. 757. Diploposthe laevis. Optical section of ripe proglottid; vd, vas deferens; /, testes; u, uterus 

 vt, vitellaria; ov, ovary; vs, seminal vesicle; v, vagina; X 22. (After Jacobi.) j 



103 (61) Uterus with median stem and lateral branches; female genital 



glands in posterior end of proglottid. 



Family TAENIIDAE Ludwig 1886. 



Scolex usually with well-developed rostellum armed with double crown of hooks, rarely with 

 rudimentary unarmed rostellum. Suckers unarmed. Terminal segments longer than broad. 

 Reproductive organs single in each proglottid. Genital pores irregularly alternate. Vas 

 deferens coiled, seminal vesicle absent. Testes numerous, scattered. Double ovary poste- 

 rior, median, posterior to which is the yolk gland. Egg with thin outer membrane, and thick 

 brown radially striated inner shell. Adults hi mammals and birds. 



Taenia Linnaeus 1758. 



Forms rightly included here are as adults characteristic parasites of higher carnivorous land 

 animals and the larval forms (cysticerci) also occur in land-living herbivorous or omnivorous 

 mammals. 



Eggs are distributed widely by surface waters. Larval stages occur rarely in aquatic mam- 

 mals, e.g., Cysticercus fasciolaris the bladder-worm of Taenia. crassicollis of the cat which Stiles 

 and Hassall, and later Linton also, have reported from the muskrat. 



104 (60) Female genital pore not adjacent to cirrus and male pore. . . 105 



105 (112) Proglottids without lateral appendages. Female genital pore is 



entirely lacking. 



Family ACOLEIDAE Fuhrmann 1907 . . 106 



Thick-bodied cestodes with rostellum usually armed. Proglottids short. Musculature 

 very powerful. Cirrus sac very large; cirrus armed with strong spines. Eggs with 3 mem- 

 branes. In birds. 



1 06 (in) Hermaphroditic forms ................. 107 



107 (no) Male and female genital organs simple .......... 108 



108 (109) Testes numerous; seminal receptacle very large; uterus a trans- 



verse tube anterior to ovary. Male genital pores regularly 

 alternate ........... Acoleus Fuhrmann 1899. 



Scolex small with armed rostellum. Reproductive organs single. Cirrus-pouch passes 



ventral of longitudinal excretory vessels and nerve. Vagina closed, functions as very large 



seminal receptacle. Adults in water birds. 



Type species ........ Acoleus armatus Fuhrmann 1899. 



From the black-necked stilt; parasite not reported from North America. 



109 (108) Testes few; seminal receptacle very small; uterus encircling 



ovary; male pores irregularly alternate. 



Gyrocoelia Fuhrmann 1899. 



Rostellum armed with single crown of hooks arranged in zig-zag row having eight angles. 

 Reproductive organs single in each proglottid. Cirrus-pouch passes between longitudinal 

 excretory vessels and dorsal of nerve. Uterus ring-like, with numerous outpocketings, and 

 with opening in terminal proglottids both dorsally and ventrally in median line of posterior 

 margin. Adults in birds. 

 In water birds; not reported in North America. 



