194 



PLATHELMINTHES 



Fig. 314 Schistocephalus gasterostei. A, forward 



end (Linton) ; B, fish containing the larval 



worm (Cambridge Natural History). 



S. gasterostei (Fabricius) (Fig. 314). Length up to 30 cm.i in 

 Gasterosteus and other fish and also the frog as a larva, and in water birds 

 as adult. 



SUBFAMILY 2. DIPHYLLOBOTHBIINAE. 



Scolex without hooks and with either 2 small suckers or highly modi- 

 fied suckers; segmentation distinct; cirrus and vagina open into a 



genital cloaca, the pore of 

 which is ventral and in 

 front of the uterine pore: 

 6 genera; in higher verte- 

 brates. 



1. DlPHYLLOBOTHRIUM 



Cobbold (Bothriocephalus 

 Rudolphi; Dibothriocepha- 



lus Liihe). Scolex flattened laterally with 2 deep slit-like suckers; strobila 



long; uterus a long tube coiled zigzag: over 50 species; in carnivorous 



mammals and water birds. 



D.. latum (L.) (Fig. 315). 



Length up to 9 m., with several 



thousand segments; onchosphere 



ciliated and free-swimming: larva a 



plerocercoid 30 mm. long found in 



the perch and many other fishes; 



adult worm in man, also in the cat 

 and dog, and com- 

 mon in certain locali- 

 ties, especially where 

 fish is much eaten; 

 in this country rare. 



SUBFAMILY 3. CYATHOCEPHALINAE. 



Scolex usually with a single terminal sucker; outer 

 segmentation indistinct or wanting; genital pores either 

 ventral or dorsal or both: 1 genus. 



CYATHOCEPHALTJS Kessler. With the characters of 

 the subfamily: 1 species. 



0. tnmcatus (Pallas) (Fig. 316). Length up to 20 

 mm.; with about 6 segments: in the pyloric coeca of the 

 whitefish. 



FAMILY 2. PTYCHOBOTHEIIDAE. 



Scolex without hooks, with 2 suckers more or less developed, each 

 of which may be converted into a pocket by the partial fusion of its 



Fig. 315 Diphyllobothrium latum 

 (Leuckart). A, anterior end, showing 

 suckers ; B, mature segment. 1, yolk 

 gland ; 2, birth pore ; 3, uterus ; 4, 

 ovary ; 5, excretory canal ; 6, nerve ; 

 7, testes ; 8, vaginal pore ; 9, male geni- 

 tal pore (cirrus) ; 10, uterine pore. 



Fig. 316 



Cyatho- 



cephalus 



truncatus 



(Zschokke). 



