. Fresh-water biology. Freshwater biology. PARASITIC FLATWORMS 441 65 (70) Rostellum hassock-shaped with a multitude of very small hooks arranged in a double row. Family Davaineidae Fuhrmann 1907 . 66 Scolex with rostellum usually broader than high and armed with very many minute hammer- shaped hooks. Margins of suckers usually with small hooks. Genital organs usually single, rarely double in each proglottid. Testes numerous. Onchosphere with two thin membranes. 66 (67) Uterus divides into numerous separate parenchyme-capsules. Davainea R. Blanchard 1891. Rostellum armed with double row of hoo
. Fresh-water biology. Freshwater biology. PARASITIC FLATWORMS 441 65 (70) Rostellum hassock-shaped with a multitude of very small hooks arranged in a double row. Family Davaineidae Fuhrmann 1907 . 66 Scolex with rostellum usually broader than high and armed with very many minute hammer- shaped hooks. Margins of suckers usually with small hooks. Genital organs usually single, rarely double in each proglottid. Testes numerous. Onchosphere with two thin membranes. 66 (67) Uterus divides into numerous separate parenchyme-capsules. Davainea R. Blanchard 1891. Rostellum armed with double row of hooks; dorsal excretory vessels present. Reproductive organs single in each proglottid. Genital pores unilateral or occasionally irregularly alternate. Uterus breaks down into egg capsules each containing one or several eggs. Adults in mam- mals and birds. Numerous species; mostly in scratching birds. D. anatina is reported from the domestic duck in Europe. No North American records. 67 (66) Uterus not breaking up into separate parenchyme-capsules. . 68 68 (69) No parauterine organ; uterus sac-shaped. Rostellum broader than scolex with several thousand booklets. Ophryocotyle Friis 1870. Rostellum broader than rest of scolex; suckers armed only near anterior border. Reproductive or- gans single in each proglottid. Uterus sac-Uke, per- sistent. Three species in European shore and water birds some of which occur in North America. Fig. 745. Ophryocotyle proteus. Head and neck with retracted and extended infundibulum; magnified. (After Stiles.) 69 (68) Uterus coiled in posterior end of proglottid; thick-walled para- uterine organ in anterior region. Rostellum small; with not to exceed a few hundred booklets. Idiogenes Krabbe 1868. Small cestodes. Genital pores unilateral. Cirrus-pouch very large, with retractor. Para- uterine organ develops in front of uterus; eggs finally pass directly into it from uterus and it is transformed into single thick-walled egg capsule. Adults m birds. A fe
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
