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FRESH-WATER BIOLOGY 



18 (17) Proglottid formation evident externally throughout entire worm, 



even in larval condition. . Schistocephalus Creplin 1829. 



Apex of scolex pitted, retractile. Bothria poorly developed. Segmentation complete. 

 Suckers and proglottids visible in larva. Adults in water birds; larvae in abdomen of Gaste- 



At least one adult and one larva are found in North America. No records have been 

 published. 



19 (16) Scolex more or less elongate, distinctly set off from rest of 



worm. . . . .... 20 



20 (21) 



Scolex similar in form to first proglottids, separated by sharp boun- 

 daries; no unjointed region (neck). 



Subfamily Haplobotheuinae Cooper. 



Proglottid formation evident externally only in anterior part of strobila. Large median 

 dorsal and two smaller ventro-lateral excretory vessels. Both vitellaria and testes medullary. 

 Cirrus covered with minute spines. Uterus sharply divided into uterine duct and large uterine 



Type and only genus. 



Eaplohothrium Cooper 1914. 



three proglottids; X 20; 6, 

 twenty -third, twenty-fourth, 

 and twenty-fifth proglottids, 

 lateral view, showing disappear- 

 ance of auricular appendages; 

 X 6; c, young scolex showing 

 beginning of proglottid forma- 

 tion; X 11; d, smallest plero- 

 cercoid observed; X 11. (After 

 Cooper.) 



Scolex small, simple; rectangular, excavated dorso-ventrally 

 to form simple bothria, and also slightly laterally. Apex slightly 

 extended to form low pyramidal disc; posterior end of scolex 

 modified as auricular appendages which with edges of apical disc 

 bear minute spines. No neck. Proglottids elongate and auricu- 

 lae decrease posteriad until segmentation near end is indicated 

 only by successive sets of reproductive organs. Large median 

 dorsal and two small ventro-lateral excretory trunks. Testes 

 small, numerous (80) in 2 lateral fields. No genital sinus. Cir- 

 rus and vagina open close together well anterior on ventral sur- 

 face. Uterine pore ventral also, anterior to posterior end of 

 uterine sac. Ovary horse-shoe shaped, ventral, posterior. Large 

 yolk-reservoir. 



Uterus in 2 regions formed very early, viz. : coiled thin-walled 

 uterine canal and capacious uterine sac which when filled occupies 

 ahnost entire central field of proglottid. Eggs with opercula, 

 carrying dhated larva. 



Type species. 



Haplobothrium globuliforme Cooper 1914. 



Intestine of Amia calva. The uterine sac and the armed cirrus 

 exclude this genus from the family in which it was placed formerly. 

 It certainly shows some points of resemblance to the Triaenopho- 

 rinae and has been included in a new subfamily which at present 

 stands isolated in a position intermediate between that and the 

 following family. 



21 (20) Scolex separated from first proglottids by unjointed region (neck). 



Subfamily Dlphyllobothriinae Liihe 1910 22 



Proglottid formation always evident externally. Genital organs single or double in each 

 proglottid. Vitellaria cortical; testes medullary in position. Vas deferens with muscular 

 bulb before entrance to cirrus sac. No spines on cirrus. 



Adults in intestine of Amniota; larvae so far as known in fishes, reproductive organs want- 

 ing at time of transfer to definitive host. 



22 (23) One set of reproductive organs in each proglottid. 



Diphyllobothrium Cobbold 1858. 



The most famous member of this genus is the broad fish tapeworm of man, D. latum, commonly 

 referred to as Bothriocephalus lotus, though it is very distinct from that genus as reference to 

 the section will show. This species has become established on the North .-Vmerican continent, 

 having been introduced no doubt by immigrants from infected territory in Europe. 



Possibly related species. . . . [Dibothrium] cordiceps Leidy 1871. 



Length of adult 2 m.; scolex cordiform 2 by o.5 to 0.8 mm., neck short. Widest about 

 IS to 25 cm. from head, where proglottids are 7.5 mm. long, 4.3 mm. broad, 0.5 mm. thick. 



