446 



FRESH-WATER BIOLOGY 



98 (99) Uterus sac-like 



Anomotaeiiia Cohn 1900. 



Rostellum with double crown of hooks, w'ith long dorsal and short 

 ventral root, and long blade. Genital pores near anterior border of 

 segment. Genital canals pass between the longitudinal excretory 

 vessels and dorsal of the nerve. Vas deferens coiled, seminal vesicle 

 absent. Testes numerous, in posterior portion of segment (or rarely 

 laterally on both sides of the female glands). Adults in birds and 

 mammals. 



]Many species from both land and water birds in Europe. A . con- 

 stricta from the fish crow, determined for U. S. A. by Ransom. [Many 

 European hosts of other species are found in North America. 



Fig. 755. 



Anomoiaenia constricta. Male and female reproductive organs, 

 magnified. (After Volz.) 



99 (98) Uterus branching and in ripe proglottids incompletely divided intp 

 numerous small communicating compartments .100 



loo ^loi) One crown of hooks on the rostellum. Choanotaenia Railliet 1896. 



Scolex small. Rostellum armed with single crown 

 of hooks usually with long dorsal and short ventral 

 root. Proglottids numerous, rarely less than 30; 

 oldest often longer than wide. Genital pores irregu- 

 larly alternate near anterior border of proglottid, 

 (ienital canals pass between longitudinal excretory 

 vessels and dorsal of nerve. \^as deferens coiled, 

 seminal vesicle absent. Testes numerous, in posterior 

 region of, or more rarely laterally on each side of, the 

 female glands. Uterus subdivided into numerous 

 small communicating chambers incomplctelj' sepa- 

 rated by partitions infolded from wall so that in some 

 cases eggs appear almost as if isolated in parenchyma. 

 Adults in birds and mammals. 



A dozen species or more from North American 



hosts; land, shore and water birds represented. Ch. 



^ ^ ^, . . ^ ,., , zWzmtfj&H/HW is common in chickens and is recorded 



Fig. 756. Choanotaenia mfundibulum for North America generally. Ch. porosa occurs in ?. 



a, Hook irom rostellum; magnmed; seg- , r ^. °, . , •'., . ^ ^ j v t • i. 



ment showing reproductive organs; magni- number of aquatic birds; it is reported by Linton 



fied. (After Ransom.) from gulls at Yellowstone Lake. 



loi (100) Rostellum armed with double crown of hooks. 



Monopylidium Fuhrmann 1899. 



Reproductive organs single in each proglottid. Genital canals pass between longitudinal ex- 

 cretory vessels and dorsal to longitudinal nerve or to both excretory vessels. Testes numerous 

 (20 to 40 or more), behind ovary and vitellarium or laterally on both sides of latter. Vas 

 deferens coiled; seminal vesicle absent. Uterus breaks down into egg capsules, each con- 

 taining usually one egg. Adults in birds. 



A dozen species in European hosts which include some shore birds found in North America. 



102 (62) Reproductive glands simple, central in each proglottid; ducts 

 and pores double, one set on each side. 



Diploposthe Jacobi 1896. 



Rostellum armed with single crown of ten hooks. Suckers unarmed. Inner longitudinal 

 muscle layer, except for two or three small bundles lateral beyond excretory vessels, developed 

 in median portion consisting of about ten dorsal and ten ventral bundles of unequal size. 

 Outer longitudinal muscle layer of numerous equally developed bundles, interrupted where 

 genital canals pass through. Outside thin layer of diagonal fibers, at posterior end well- 

 developed muscle ring. Genital pores marginal, one on each side. Testes few (3 to 7) in 

 posterior portion of proglottid. Two vasa deferentia. Seminal vesicles present on each side 



