190 TAPEWORMS OF HAKES AXD RABBITS STILES. 



fact that the testicles are almost absent from the median portion of 

 the field, being arranged in two triangles. 



C. perplexa agrees with C. variabilis in the general size of cirrus 

 pouch. It differs from C. variabilis in the earlier appearance of the 

 genital anlageii in the position and arrangement of the testicles. The 

 following is proposed as specific diagnosis : 



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

 Strobila attains 57 mm. long by 10 mm. broad. Head unarmed, small, 

 about 0.32 mm. broad, not distinctly separated from body; rostellum 

 iiol observed; suckers 0.112 mm. in diameter. Keck extremely short, 

 segmentation beginning almost immediately back of the head. Genital 

 pores double, and opposite, in about the middle of the margin. Anlagen 

 of female glands and canals visible within 0.64 mm. of the anterior 

 extremity of the head. Male organs: Cirrus pouch similar to that of 

 C. variabilis, but smaller, about 0. -'88 to 0.32 mm. long, extending to or 

 slightly beyond the lateral nerves; testicles arranged in two groups in 

 each segment, one triangle being around each ovary and extending 

 laterally to the longitudinal canals. Female organs : Agree essentially 

 with those of C. variabilis, as does the general topography; uterus 

 single or double. 



Host. Cottontail Babbit (Lcput> sylvaticus] by E assail in Bowie, 

 Maryland. 



Types. Bureau of Animal industry, Cestode series, No. 1126, desig- 

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

 Paratypes in Bureau of Animal Industry; Nos. 1110, 1131,1137-1139, 

 U.S.N.M.; collection of Stiles; collection of Hassall. Other typical 

 specimens will not be distributed until more material is obtained. 



CITTOT^ENIA VARIABILIS (Stiles, 1895), Stiles & Hassall, 1896. 

 (Plate XIX, figs. 1-14; Plate XX, figs. 1-5.) 



1892, "Tcenia pectinala, GOEZE," 1782, ex parte of CURTICE, Journ. Comp. Med. Vet. 

 Arch., XIII, pp. 232-233. 



1895, CtenotceniavariabiUs, STILES, Veterinary Magazine, II. June, p. 345. Aug. 28, 1896. 



1896, Cittotcenia variabilis (&TILKS, 1895), STILES & HASSALL, Veterinary Magazine, 



III, p. 407. 



As stated in the introduction, helminthology is not so far advanced 

 that it is possible for us to determine what limits should be given to 

 genera, subgeuera, species, and subspecies, and for some time to come 

 all classification into groups must be looked upon as experimental, the 

 ideas of every author being subject to change from day to day as new 

 facts in the comparative anatomy of cestodes are published or observed. 

 The American form which I now describe as Cittotcenia variabilis is 

 one of the parasites which can equally well be considered as a distinct 

 species, or as a subspecies, possibly peculiar to given hosts. It is so 

 perfectly distinct from the European C. pectinata that no specialist 

 could fail to recognize the differences when he has the two forms side 

 by side for comparison. Yet it is so closely allied to the European 



