. Fresh-water biology. Freshwater biology. 440 FRESH-WATER BIOLOGY with shell gland between. Eggs thin-shelled, no lid; onchosphere with one or more mem- branes. Bladder-worm in vertebrates and invertebrates. The great majority of forms commonly designated Taenia are included here. Number and form of hooks on which older systems are based iorm unreliable means for the distinction of species. In immature forms the organs utilized in this key are undeveloped and a deter- mination can only be approximate. 55 (117) Body flattened. Distinct and regular external boundaries corre- sponding to interna
. Fresh-water biology. Freshwater biology. 440 FRESH-WATER BIOLOGY with shell gland between. Eggs thin-shelled, no lid; onchosphere with one or more mem- branes. Bladder-worm in vertebrates and invertebrates. The great majority of forms commonly designated Taenia are included here. Number and form of hooks on which older systems are based iorm unreliable means for the distinction of species. In immature forms the organs utilized in this key are undeveloped and a deter- mination can only be approximate. 55 (117) Body flattened. Distinct and regular external boundaries corre- sponding to internal grouping of organs in the strobila. 56 56 (57) Suckers carry on anterior and lateral surface auricular appendages. Vitellarium anterior to ovary. Family Tetrabothkudae Fuhrmann 1907. Scolex unarmed, without rostellum. Neck short. Proglottids except oldest always much broader than long. Reproductive organs single in each proglottid. Genital pores unilateral; genital cloaca deep. Cirrus-pouch small and nearly spherical, united with genital cloaca by muscular cloacal canal. Eggs with three transparent en- velopes. Adults in birds and mammals. Tjrpe genus. Tetrahothrius Rudolphi 1819. With characters of the family. Scolex unarmed, quadrate. Suckers large. Sexual pore always dextral. The hosts are aquatic birds, largely marine. Nearly twenty species Fig. 744. Tetrahothrius j^j-g described, a number of which occur in North American birds: Sfied (After LUheO ™^^" (S""' S'^^' h"0°' 1°°°)' ^^""^ frequent fresh-water bodies. 57 (s6) Suckers simple without appendages of any sort. ViteUaria not anterior to ovary but posterior to it, or in the same trans- verse plane with it. 58 58 (59) Genital pores median, on flat surface of proglottids. Family Mesocestoididae Fuhrmann 1907. Scolex without rostellum or hooks. Suckers unarmed. Reproductive organs single in each proglottid. Genital pores median on ventral surface. Vagina opens in front of or beside cirr
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectfreshwa, bookyear1918
