Trematodes and Cestodes 9 G-H 



Subfamily II DIPHYLLOBOTHRIINAE Ltihe 1910 



Genus I Diphyllobothrium Cobbold 1858, e.p. Liihe 1910 



Diphyllobothrium canadense, sp. nov. 



(Figs. 4, 5, 11.) 



Specific diagnosis. With the characters of the genus. Large cestodes at 

 least 235 mm. in length and 6-5 in maximum width. Scolex small, elongated, 

 rectangular in outline surficially and laterally, excepting for rounded summit, 

 0-84 mm. in length, 0-37 in width at base and 0-46 in thickness at middle. 

 Bothria long and narrow, not sharply separated posteriorly from surfaces of 

 strobila. Neck, 0-7 mm. in length. First segments, 0-045 mm. in length by 

 0-50 in width; width of segments 30 mm. from scolex, 3-0 mm., 37-5 from 

 scolex, 3-5 by 0-65 in length. At about its middle, where the segments are 

 6-5 mm. in width by 0-60 in length, the strobila is ruffled or frilled laterally. 

 Hindermost gravid segments from two or more to one and a half times as broad 

 as long anteroposteriorly. Posterior borders moderately prominent throughout. 



Cuticula 4 5/j, in thickness, outer half cirrous. Main longitudinal parenchy- 

 matous muscles scarcely arranged in fascicles, whole layer 35ju in thickness. 

 Calcareous bodies ellipsoidal in shape, at least 10 p in length. Nerve strands 22 

 to 0-23 of width of proglottis from margins. 



Rudiments of the genitalia appear 6 mm. behind the scolex, the first eggs 

 about 20 mm. Genital cloaca median, one third of the length of the segment 

 from its anterior border, 160^ in diamter by 80 in depth. Vaginal opening 

 immediately behind that of cirrus and very slightly to one side; beginning of 

 vagina alternates irregularly from right to left opposing the lower portion of the 

 cirrus-sac. 



Testes continuous from proglottis to proglottis and from side to side between 

 the consecutive, centrally located sets of female genitalia; at least 150 in number; 

 ellipsoidal in shape, the greatest diameter being transverse, 55 to 90ju in length, 

 110 to 145 in width and 60 to 90 in depth. Vas deferens 25/* in diameter; only 

 slightly coiled dorsal and somewhat posterior to the cirrus-sac, coils 0- 14 mm. in 

 length, 0-40 in width and 0-20 in depth. Seminal vesicle spheroidal, thick- 

 walled, muscular, posterodorsal to cirrus-sac and a little to one side of the med- 

 ian line directly above the beginning of the vagina, 90 to 145ju in diameter. Vas 

 deferens 18/z in diameter as it pierces the wall of the cirrus-sac in the median 

 line, only slightly enlarged and coiled in the dorsal half of the cirrus-sac. 

 Cirrus, 40 to 55^ in diameter, occupies the ventral half of the pouch. 

 Cirrus-sac ovoid in shape with the narrower end ventral; dorsal end deflected 

 slightly from the median line to the side opposite that occupied by the seminal 

 vesicle and the beginning of the vagina; 0-30 to 0-32 mm. in length (depth) 

 by 0-15 to 0-20 in diameter; connected to the dorsal body-wall by numerous 

 stout retractor muscle-fibres, many of which pierce its wall and are attached 

 to the proximal end of the cirrus proper at the middle of the sack. 



Just within its opening the vagina, slightly enlarged to a diameter of 40/x, 

 curves dorsally and somewhat aside to reach the median line and take a straight 

 course posteriorly close against the ventral wall of the medulla. Half way along 

 its course it is reduced to 22/* in diameter. Above the ovarian isthmus it gradu- 

 ally becomes enlarged to as much as 100/z in diameter to form an elongated 

 seminal receptacle, having comparatively thick walls. Spermiduct 30ju in length 

 by SM in diameter. Ovary near the posterior border and ventral musculature 

 of the proglottis, 0-50 to 1-30 mm. in width by 0-18 to 0-28 in length by 0-20 

 in thickness, irregularly lobulated laterally, the lobules intermingling somewhat 

 with the coils of the uterus; isthmus 60/z in diameter. Oooapt 28 to 30// in 

 diameter. Vitelline follicles closely crowded together, continuous from segment 

 to segment and at the margins and anterior and posterior borders of the proglot- 



