192 TAPEWORMS OF HARES AXD RABBITS- STILES. 



but gradually the uterus develops to such an extent that it suppresses 

 all the genital glands. The cirrus pouch becomes indistinct, bat the 

 vagina can be traced in nearly all segments. 



As the uterus increases in size it gives rise to proximal and distal 

 branches, but the latter are far less regular than those of the European 

 C. pectinata. In the posterior segments it is generally difficult to dis- 

 tinguish the two uteri. The ova measure CO to 04 // in diameter: the 

 bulb of the pyriform body, 12 to 16 /,/. This is the species (var. angusta] 

 upon which my paper. "A double-pored cestode with occasional single 

 pores 77 was based, and since writing that note another case of the same 

 variation was noticed. On account of the numerous variations in 

 the position of the genital pores, uterus, etc., noticed in the specimens 

 studied, I proposed to name the worm Ctenotcenia rariabilis. 



Larval stage. The young specimens described on page 201 were col- 

 lected in the same locality as the species here described, and from the 

 same host; and it seems probable that the unarmed young mentioned 

 on page 201 are the young of either C. rariabilis or C. perplexa. 



Diagnosis. Cittotcenia variabilis (Stiles, 1895), Stiles & Hassall, 1896. 

 (American representative of C. pectinata.) Strobila attains 100 to 

 180 mm. in length and 10 mm. in breadth. Head small, about 0.3 to 

 0.6 mm. in breadth ; it may or may not be denned from the neck accord- 

 ing to contraction. Neck very short, segmentation beginning almost 

 immediately back of the head; segments always much broader than 

 long. Genital anlagen appear very early, about 5 to 10 mm. from the 

 head. Genital pores double, in about the middle third of the lateral 

 margin. Male organs: Testicles about 60 to 100 in each segment, con- 

 fined between the ovaries to. the dorsal portion of the distal half of the 

 median field; cirrus pouch about 0.4 mm. long, narrow and very indis- 

 tinct, lying dorsally of the vagina on both sides of the segment. Female 

 organs: Ovary, shell gland, and vitellogene gland resemble the corre- 

 sponding organs of Moniezia; they lie median of longitudinal canals, 

 about 1.3 mm. from the lateral margin; the vagina is rather distinct, 

 lies ventrally of the cirrus pouch, and for about 0.5 mm. from the pore 

 it is surrounded by deeply staining cells; uterus may be double or 

 single (in the same specimen) and may produce proximal and distal 

 branches; ova 60 to 64 /* in diameter; bulb of pyriform body 12 to 16 //. 

 Longitudinal nerve about 0.6 mrn. from the lateral margin; ventral 

 canal large with thin lining; dorsal canal much smaller than ventral 

 canal, dorso-median of ventral canal, with thick lining; transverse 

 canals connect ventral canals [no injections made for secondary longi- 

 tudinal canals]. Genital ducts and uterus pass from median to lateral 

 field on the dorsal side of the longitudinal canals and nerves. 



Host. Cottontail Babbit (Lepus syh'aticus), by Hassall; Marsh Hare 

 (L. palustris), by Mills. 



Types. Bureau of Animal Industry, Cestode series No. 117 desig- 

 nated as type and deposited in the United States National Museum. 

 Paratypes distributed as follows: Collection of Bureau of Animal 



