448 FRESH-WATER BIOLOGY 



no (107) Male reproductive organs double and female single in each pro- 

 glottid with two vaginae functioning as large seminal re- 

 ceptacles Diplophallus Fuhrmann 1900, 



Large forms with small scolex and armed ros- 

 tellum. Testes numerous, in two lateral fields 

 fully separated by median female glands. Cir- 

 rus sac powerful, cirrus slender, very long. 

 Vagina a blind transverse canal. Uterus at 

 first transverse tube: later irregular, and finally 

 taking in entire medullary region. 



Type species. 



Diplophallus polymorphus 



(Rudolphi) 1819. 



Fig. 758. . Diplophallus. Schematic transverse Yxom the black-necked stilt; parasite not re- 

 section of ripe proglottid; /.testes: «, uterus; sr, ^^^ r „ -^t ,i »„ . '^ 



seminal receptacle; .., ovary; vt, vitellaria. (Afte^ ^^rded from North America. 

 Wolffhugel.) 



111 (106) Dioecious, entire strobila male or female; male with a double 



set, female with a single set of reproductive organs in each 



proglottid Dioicocestus Fuhrmann 1900. 



Female thicker and broader than male. Vagina irregularly alternating, reaching almost to 

 the edge of the segment. Testes numerous, divided more or less plainly into two symmetrical 

 groups. Eggs with three envelopes. ]Male ducts paired in every proglottid. Adults in 

 birds. 



Type species Dioicocestus paronai Fuhrmann 1900. 



Several species from grebe and ibis; parasite not recorded from North America. 



112 (105) Proglottids carry lateral foHate or digitate processes. Female 



genital pore, when present, separate from marginal male 

 pore. . . Family Aimabiliidae Fuhrmann 1907 . . 113 



Rostellum with simple crown of hooks. Proglottids short with lateral margins prolonged 

 into processes. Musculature weakly developed. Cirrus sac large; cirrus spinous. Duct 

 united with receptaculum seminis, designated as accessory vagina, opens in cases on surface or 

 on margin opposite male pore. 



In water birds. 



113 (114) Male sexual organs double in each proglottid. Accessory vagina 



with surface opening. Uterus a network. 



Amahilia Diamare 1893. 



Scolex very small with armed rostellum. Male reproductive organs double with one pore 

 on each side of proglottid. Cirrus armed with strong spines. Testes numerous, in median 

 field. Female organs median, single set in each proglottid. Uterus forming network con- 

 sisting of dorsoventral ring with dorsoventral anastomoses. Accessory vagina opening ven- 

 trally, communicating (?) with canal from excretory system opening on ventral surface of 

 proglottid in median line. Adults in birds. 



Type and only species imabilia lafnelligera (Owen) i8$2. 



114(113) Male organs single in each proglottid. Uterus sac-like. . . . 115 



115 (116) Rostellum thick, powerful. Male pores alternate irregularly. 

 Female pore, when present, on surface of proglottid. 



Schistotaenia Cohn 1900. 



Rostellum very large, armed with heavy hooks. Between rostellum and suckers an annular 

 thickening covered closely with small three-cornered hooks. Testes numerous, dorsal, poste- 

 rior, across entire width of proglottid, reaching maturity later than female glands. Ovary 

 and vitellarium large. Male duct runs between excretory canals, accompanying vagina which 

 ends blindly near cuticula. 



Tj^e species S. macrorhyncha in the horned grebe. Parasite not recorded from North 

 America. 



