154 ILLINOIS BIOLOGICAL MONOGRAPHS (442 



CLESTOBOTHRIUIVI CRASSICEPS (Rudolphi 1819) 

 [Figs. 29-31, 48, 49, 58, 74, 75, 90, 103, 108] 



1909 Dibothrium crassiceps Johnstone 1909 : 87 



Specific diagnosis: With the characters of the genus. Medium sized ces- 

 todes, up to 92mm. in length, with a maximum breadth of 1.5mm. Anteriorly 

 surface of body with closely arranged transverse furrows, posteriorly segmenta- 

 tion more distict, serrate. Scolex globose, 0.64 to 1.08mm. long, 0.52 to 0.90 

 broad, and 0.68 to 1.21 thick; divided by longitudinal marginal grooves into 

 two dorsoventral hemispheres, the bothria. Latter large, prominent, oval, 

 their apertures about one-third their length from the apex and connected by a 

 saddle-shaped groove over the tip of the scolex, with prominent lips. No neck, 

 segmentation beginning immediately behind the scolex. Young segments 

 closely arranged, five to six times as broad as long; mature proglottides quad- 

 rate to twice as long as broad, frequently divided on one or both sides by 

 spurious articulations usually behind the uterus-sacs. 



Cuticula 2 to 5n thick, subcuticula 20ijl. Chalk-bodies absent. Muscula- 

 ture well developed, powerful sphincter around orifice of bothrium. Chief 

 nerve strands ventral, 15 to 20/li in diameter. Usually four longitudinal ex- 

 cretory vessels. 



Genital cloaca median, dorsal, three-fourths to one-half the length of the 

 proglottis from its anterior end, usually just posterior to the spurious articula- 

 tions; hermaphroditic duct within cloaca. 



Testes in two lateral fields in the medulla; ellipsoidal in shape, 0.125mm. 

 long by 0.04 in diameter, continuous from joint to joint, 40 to 50 in each proglot- 

 tis. Vas deferens forms a wedge-shaped mass of coils ahead of cirrus-sac and 

 alongside of the hinder end of the uterus-sac. Cirrus-sac elliptical to some- 

 what oval, 0.128 to 0.162mm. long by 0.087 to 0.116 wide and 0.098 to 0.116 

 deep, immediately behind the uterus-sac or lateral to its posterior end. Cirrus- 

 sac and vas deferens together alternate irregularly from right to left opposite 

 the hinder end of the uterus-sac. 



Opening of vagina close behind that of cirrus. Receptaculum seminis 

 present as a short diverticulum almost parallel to the oviduct at the point of 

 union of the vagina with the latter, about lOjn in diameter. Ovary bilobed, 

 the isthmus narrow and ventral, ova in same 18 by 10^. Oocapt 20/x in dia- 



