442 



75 (76) 



FRESH-WATER BIOLOGY 



Strobila broad, lancet-shaped. Ovary and vitellarium ante-poral, 

 alongside of testes. Drepanidotaenia Railliet 1892. 



Scolex very small, with 8 hooks. Neck wanting. No accessory sac in genital atrium. 



Type species. . . . Drepanidotaenia lanceolata (Bloch) 1782. 



Adult in intestine of ducks and geese; cosmopolitan. Bladder-worm in various Cyclopidae 

 and Diaptomus. 



Fig. 746. Drepanidotaenia lanceolata. Transverse section of proglottid; «, uterus; ut, vitellaria; 

 ov, ovary; /, testes; id, vas deferens; sr, seminal receptacle; v, vagina; magnified. (After Wolffhugel.) 



76 (75) Strobila slender or even filiform. Ovary and viteUaritim ventral to 



testes or between them. 77 



77 (78) Suckers entirely unarmed, or at most armed with hooks on margin 



only. Hymenolepis Weinland 1858. 



Rostellum well developed, rarely rudimentary 

 or absent. Accessory sac generally wanting in 

 genital atrium. Rarely as abnormality 2, 4, 

 5, or 6 testes in a single proglottid. CMeiiy in 

 land and water birds; some species in mam- 

 mals. 



A very large genus; about 50 species occur in 

 aquatic hosts found in North America. Among 

 them a few are definitely reported for North 

 America. H. compressa (Linton) 1892 from the 

 scoter and canvas-back. H. fusus in which 

 Fuhrmann places Linton's Taenia filum from 

 gulls at Yellowstone Lake. 



H. megaiops described by Ransom (with other 

 species from land birds) from the pintail duck; 

 Missouri River, Mo. 



Fig. 747. Hymenolepis megaiops. Dorsal view 

 of mature segment (no. 172). Reconstruction from 

 sections; br, retractor of cirrus-pouch; ci, cirrus; 

 cr, retractor of cirrus; dc, dorsal excretory canal; gc, 

 genital cloaca; nt, main lateral nerve; sg. shell 

 gland; t, testis; tm, transverse muscles; ut. uterus; 

 DC, ventral excretory canal; vg, vagina; vs, seminal 

 vesicle; vs', seminal vesicle of cirrus-pouch; xpl, 

 plexusof excretory vessels; y^, yolk glands. X 90. 

 (After Ransom.) 



78 (77) Suckers armed on borders and also in cavity with small hooklets; 

 sacculus accessorius always present. 



Echinocotyle Blanchard 1891. 



Rostellum armed with single crown of ten slender hooks with dorsal 

 root and blade about equal in length and ventral root rudimentary. 

 Suckers large, flat, oval, poor in musculature, armed on borders and in 

 middle with several rows of small hooklets. Muscular, spinous sacculus 

 accessorius always present. Adults in birds. 



Type species. . Echinocotyle rosseteri Blanchard 1891. 



Five spedes in shore and water birds of Europe. Hosts mostly found 

 in North America also. 



Fig. 748. 



Echinocotyle rosseteri. Head with extended rostellum; X 2!o. 

 (After Blanchard.) 



