190 TAPEWORMS OF HAL'E>! AX J) RABBITS— STILES. 



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

 the field, being arranged in two triangles. 



C. perpJexa agrees with C. rariahUifi in the general size of cirrus 

 pouch. It (litters Ironi C. variabiliN iu the earlier ai)pearance of the 

 genital anlagen in the i)osition and arrangement of the testicles. The 

 following is proposed as specitic diagnosis: 



/>/«//» o.s/.s'. — (:iHoi(vnia pct'jtle.ra (Stiles, ISl).")), Stiles & Hassall, 1890. 

 Strobila attains Tu mux. long by 10 nira. broad. Head unarmed, small, 

 abont O.o2 mm. broad, not distinctly separated from body; rostelliun 

 not observed: suckers 0.1 lli mm. in diameter. Xeck extremely short, 

 segincntiition beginning ahnost immediately back of the head, (lenital 

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

 of female glands and canals visible within 0.04 mm. of the anterior 

 extremity of the head. IMale organs: Cirrus pouch simihir to that of 

 C. vayiahilisj but smaller, about of-'8S to O..")!' mm. huig, 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 oi'gans: Agree essentially 

 with those of ('. rariabUi.s. as does the general topography; uterus 

 single or double. 



//o.s7.— Cottontail Uabbit {Lcpns .si/lraticuti) by Dassall in Bowie, 

 INIaryland. 



2'ijpes. — Bureau of Animal industry, Cestode series, Xo. 1120, desig- 

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

 raraty])es in Bureau of Animal Industry; Nos. 1110, ll.'Jl, li;i7-1130, 

 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-U; Phite XX, ligs. 1-5.) 



1892, "Ta'nia pecfhiala, Goeze," 1782, ex ])arte of Cuktice, .lonrii. (Omp. 'Sled. Vet. 

 Arch., XIII, PI). 232-233. 



1895, CtenolatiUi variahUis, Stii.es. Veterinary Magazine, II. June. p. 345. Ang. 28, 1896. 



1896, Clttotwnia variabilis (Stiles. 1895), Stile.s & Hassall, Veterinary Magazine, 



III, p. 407. 



As stated in the introduction, lu-lminthology is not so far advanced 

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

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

 all classiGcation into groui)s must be looked ujion 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 ob.served. 

 The American form which I now describe as Cittottvnia variabilis is 

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

 spe(;ies, or as a subspecies, possibly peculiar to given hosts. It is .so 

 l)erfectly distinct from the European C. pcctinata that no specialist 

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

 by side for comparison, let it is so closely allied to the European 



