43 FRESH-WATER BIOLOGY 



3 (4) Anterior end not peculiarly modified. No suckers, hooks, or special- 



ized scolex region Amphilina Wagner 1858. 



Large, oval, flattened forms, parasitic in body cavity of fishes. Anterior end usually notched, 

 but occasionally extended in the form of a small papilla bearing the pores of a group of uni- 

 cellular glands. Male genital pore at posterior end. No cirrus sac present. Female pore 

 slightly anterior to male pore, separate from it. Uterus long, uterine pore at anterior end. 

 Embryo with circle of ten hooks at one pole. 



Not yet reported from North America but present. 



4 (3) Anterior end with unarmed, poorly developed adhesive organ, imper- 



fectly set off as scolex from rest of body. 



Family CARYOPHYLLAEIDAE Claus 1885 .. 5 



Body elongate, flattened, with nearly parallel sides and primitive scolex. Neck may be 

 present or wanting, as also a caudal appendix. All genital pores ventral, median, near poste- 

 rior end; cirrus anterior; uterus and vagina open together into a genital atrium. 



5 (6) Caudal appendix present in adult. Two distinct sucking grooves on 



rudimentary scolex Archigetes Leuckart 1878. 



Sexually mature in pligochaetes. A form which undoubtedly belongs here has been described 

 to me as found in native earthworms. It has not been recorded in the literature. The species 

 known are 2 to 6 mm. long and parasitic in the body cavity of Tubificidae. 



6 (5) No sucking grooves present. Caudal appendix lacking in adult though 



present in larval form. . Caryophyllaeus 0. F. Miiller 1787. 

 Expanded anterior end very mobile, irregularly folded but without definite sucking grooves. 

 Intestinal parasites of Cyprinid fishes. Larvae parasitic in body cavity of Tubificidae. 



7 (2) Body multiplex, usually divided externally into joints or proglottids; 



always containing successive sets of reproductive organs 

 generally corresponding to such subdivisions even in cases 

 where external proglottid markings are lacking. 



Subclass Cestoda s. str. . . 8 



Elongate, ribbon-like forms in which the reproductive organs are serially duplicated, each 

 set constituting a reproductive unit, usually though not always set off from adjacent units by 

 internal septa and external boundaries. These forms are often spoken of as the true tapeworms, 

 or polyzootic cestodes. 



8 (29, 30) Scolex with a single terminal or with two opposite sucking organs, 



never with four suckers or accessory proboscides. 



Order Pseudophyllidea . . 9 



Scolex rarely armed with hooks, never provided with rostellum, or extrusile proboscides. 

 The two sucking grooves sometimes combined by complicated growth of their margins into a 

 funnel-shaped or tubular organ which may be united with that of the opposite side to a termi- 

 nal sucker of peculiar form. External jointing is rarely lacking, but often indistinct in certain 

 regions at least. Uterine pore present, on the surface of the proglottid. Uterus in the form of 

 rosette-shaped coils or of a large sacculate uterine cavity. 



Characteritic fish parasites in one or more stages of the life history. 



Ltihe places the Caryophyllaeidae (see above), as the first family under this order, grouping 

 them as monozootic Pseudophyllidea in contrast with all other families as polyzootic. For 

 practical reasons they are treated here under the Cestodaria. 



9 (28) Adult forms with developed reproductive organs 10 



The larval forms are sometimes hard to distinguish from adults. Consult also 28(9). 



10 (13) Eggs thin-shelled, without lid. Uterine pore ventral; cirrus and 



vagina open dorsal and posterior to uterine pore, or margi- 

 nal. . . . Family PTYCHOBOTHRIIDAE Liihe 1902 . . n 



Scolex with two separate bothria, rarely replaced by a pseudoscolex. No neck; external 

 segmentation always present but incomplete or obscured by secondary folds in many cases. 

 Reproductive organs single in each proglottid. Cirrus and vaginal pores posterior to uterine 

 pore, marginal or median and then on opposite surface from uterine pore. Ovary and shell 

 gland median; testes in two lateral fields. Uterus in form of a single spacious cavity, never 



