32 ILLINOIS BIOLOGICAL MONOGRAPHS [320 



flatter, 0.25 to l.Omm. in length by 1 to 3mm. in width, forming an appendage 

 up to 10mm. in length; medium segments 0.1 to 0.5mm. long, posterior borders 

 prominent. Shallow median groove on the ventral surface. 



Cuticula 15 to 20^t in thickness; subcuticula 40 to GS/x. Layer of internal 

 longitudinal muscles 15 to 50^t in thickness. Nerve strands 30 to 75;u in diame- 

 ter. 25 to 30 excretory vessels in transections. 



Genital cloaca median, shallow, with a diameter of 90/i; no hermaphroditic 

 duct. Opening of vagina close behind that of cirrus and to one side but not 

 so far as that of the uterus, both alternating irregularly from side to side. 



Testes extend from the median genital ducts laterally to the edges of the 

 medulla, unbroken from proglottis to proglottis, closely crowded, 240 to 480 

 in number for each proglottis, 85 to 100/x in depth, 40 to 65 in width and 55 to 

 85 in length. Vas deferens median, dorsal, closely applied to the seminal vesi- 

 cle, the whole mass 0.30mm. in diameter, the duct itself 35 to 60/1. Seminal 

 vesicle 175 by 150/i, walls 25ju in thickness. Cirrus-sac oval in shape, immediate- 

 ly below the seminal vesicle, 0.185 to 0.203 by 0.203 to 0.212 by 0.166 to 0.185 

 mm. in dimensions. No inner seminal vesicle. Cirrus proper not sharply 

 separated from the ductus ejaculatorius; whole surrounded by numerous 

 retractor muscles. 



Vagina 45 to 60/i in diameter just within the medulla. Receptaculum 

 seminis large, 92 to 105)u in diameter. Spermiduct unites with the oviduct 

 close to the ventral wall of the medulla. Ovary with large wings consisting 

 of closely arranged tubules, whole organ 0.6mm. in width, wings 0.10 in length. 

 Ova ISfjL in diameter, their nuclei 5/x. Oocapt 35 to 40/x in diameter, oviduct 

 25 to 30/x. Vitelline gland unbroken at margins of the proglottis, from proglot- 

 tis to proglottis, and medially, excepting for small areas above and below the 

 proximal reproductive ducts; individual follicles 55 to 90 by 18 to 26/i. 

 Ootype 16 to 20^ in diameter. Shell-gland shghtly to one side of median line. 

 Uterus 85 to 135/i in diameter at its middle; the terminal portion directed 

 dorsoventrally and hned with cuticula distally ; opening at the bottom of a slight 

 invagination of the ventral body wall, formed by the rupture of a pre- 

 existing cuticular membrane. 



Eggs, 38 to 65 by 22 to 38/z. 



Habitat: As larvae in the body-cavities and occasionally in the stomach 

 and intestine of bony fishes ; adults in the intestines of wading and diving birds. 



