434 FRESH-WATER BIOLOGY 



28 (9) Immature forms; sexual organs wanting or at least as yet only partly 



developed Sparganum Diesing 1855. 



Larval stages, without sex organs; not yet at a period in which specific determination is 

 possible. Many undescribed forms in various hosts; three known forms are hsted below. The 

 first named is not yet reported for this continent; the second and third are definitely recorded 

 for United States of America. 



Sparganum mansoni (Cobbold) 1882. 



Large forms, 8 to 36 cm. long; o.i to 12 mm. broad. Two longitudinal grooves on dorsal 

 surface; one median longitudinal groove on ventral surface. In connective tissue and body 

 cavity of man. Japan. The probable adult, Diplogonoporus grandis has been reported from 

 Porto Rico. 



Sparganum proliferum (Ijima) 1905. 



Small form, i to 12 mm. long, 2.5 mm. broad. Body usually irregular in form. Multipli- 

 cation in cysts by formation of supernumerary heads and transverse division. Encysted in 

 subdermal connective tissue and elsewhere; in man, Florida, U. S. A., and Japan. 



Sparganum sebago Ward 1910. 

 Length 25 to 36 mm., breadth 1.8 to 0.36 mm. Head with keyhole-shaped bothria. Body 

 elliptical in cross-section with sUghtly thickened margins. No segmentation developed and 

 no sex organs. In spleen and body cavity of Salmo sebago; Maine. 



29 (8, 30) Scolex with two or four sucking grooves, and also at apex four 



protrusile proboscides armed with many hooks. 



Order Trypanorhyncha. 



The four long slender cylindrical proboscides are conspicuous enough to render the deter- 

 mination of adult or larva easy. The adults are found in the spiral valve of sharks and rays; 

 the larval forms occur encysted in migratory fish. They are among the rarest of finds in 

 fresh-water collecting and are present in North America though no species are recorded as 

 yet. 



30 (8, 29) Scolex with four sucking organs (exceptionally replaced by a 



pseudoscolex) but without extensile proboscides. No 

 uterine pore 31 



31 (54) Vitellaria with very numerous follicles, distributed on each side in 



longitudinal marginal zone, rarely in the entire surface zone 

 of the proglottid Order Tetraphyllidea. 



Sucking organs 4, cup-shaped, small, or very mobile stalked or unstalked modified bothridia. 

 Small apical sucking organ frequent. Pseudo-scolex exceptionally present. External seg- 

 mentation evident, but less conspicuous at end of chain. Genital organs single in each pro- 

 glottid. No uterine pore, but uterus opens in median ventral line by rupture of wall. Testes 

 numerous. Ovary posterior, median, usually with two wings. Eggs thin-shelled, without 

 lid; embryonal development in uterus. 



Adults in intestine of cold-blooded vertebrates. 



Only family in North America in fresh-water hosts. 



Family Proteocephalidae La Rue 1911 . . 32 



Heads small. Suckers sessile and without accessory areola. Fifth sucker functional, ves- 

 tigial, or lacking. No rostellum. Genital organs in general as in other TetraphyUidea. 

 Genital pores marginal, irregularly alternating. Vitellaria lateral, follicular, follicles closely 

 grouped about a central conducting tubule. Ovary bilobed, posterior. Oocapt, ootype, shell 

 gland, and uterine passage present. Uterus with lateral outpocketings and one or more pre- 1 

 formed ventral uterine openings. Vitellaria, testes, ovary and uterus within the inner longi- i 

 tudinal muscle-sheath. 



Habitat: In fresh-water fish, amphibians, and aquatic reptiles. 



32 (53) Head without lappets or folds of tissue around suckers ^t, \ 



2,2> (46) Testes in one broad mass between vitellaria; parasitic in fresh- ' 

 water fish Proteocephalus Weinland 1858 . . 34 i 



Head globose or conical, flattened dorsoventrally. No rostellum. No spines or hooks. , 

 Suckers circular or oval. Fifth sucker functional or vestigial, rarely lacking. Musculature ' 

 well developed. Eggs with three membranes. ' 



