308 THE ANIMAL PARASITES OF MAN 



also club-shaped segments occur between normal ones, or there may be a defect 

 in one segment or in the centre of a number following one another (fenestrated 

 segments) ; bifurcated chains of segments have likewise been observed, as well as 

 incomplete or complete union of the proglottids, abnormal increase of the genital 

 pores, reversion of the genitalia. Besides the above-mentioned increase of the 

 number of suckers on the scolex (in Taeniae), there may be a decrease in the 

 number ; in other cases the crown of hooks may be absent, or abnormally shaped 

 hooks may be formed. 



CLASSIFICATION OF THE CESTODA OF MAN. 

 Order. Pseudophyllidea, Cams, 1863. 



Scolex without proboscis or rostellum. Head " stalk" absent. 



Scolex never with four, generally with two (or one terminal) bothria. 1 Vitellaria 

 numerous. Uterine opening present. Genitalia do not atrophy when uterus is 

 developed. In large majority of proglottids eggs (or, if formed, their contents) are 

 at the same stage of development. 



Family. Dibothriocephalidae, Liihe, 1902. 

 Syn. : Diphyllobothriidce, Liihe, 1910. 



Genitalia repeated in each proglottid (polyzootic Cestodes). Ventral and dorsal 

 surfaces flat. Cirrus unarmed. Cirrus and vagina if non-marginal open on the 

 same surface as the uterus. Uterus long, convoluted, often forming a " rosette," 1 

 never dilates into a uterine cavity. Eggs thick shelled, operculated, constantly 

 being formed in mature proglottids. 



Sub-family. Dibothriocephalinae, Liihe, 1899. 

 Syn. : Diphyllobothriituz, Liihe, 1910. 



Segmentation distinct. Scolex unarmed, elongated, sharply separated (generally 

 by a neck) from the first proglottis. Cirrus and vagina open ventrally. Genital 

 pores non-alternating. Vas deferens surrounded by a muscular bulb. Receptacu- 

 lum seminis large, sharply separated from the spermatic duct. 



Order. Cyclophyllidea, v. Beneden. 



Four suckers always present. Uterine opening absent. Vitellarium single. 

 Genitalia atrophy when uterus is fully developed. 



1 Bothridia or " phyllidia " are outgrowths from the scolex. They are concave and 

 extremely mobile. By some authors the term " phyllidium " is used for the outgrowth, and 

 the term " bothridium " is restricted to the muscular cup. Bothria, on the other hand, are 

 grooves more or less wide, the musculature of which is only slightly developed and is not 

 separated off internally from the parenchyma. Acetabula, or suckers in the usual sense, are 

 hemispherical cups, without lips and with musculature separated internally from the 

 parenchyma. 



