58 
The Lanceolate Tapeworm — HYMENOLEPIS LANCEOLATA^ (Bloch, 1782) 
Weinland, 1858. 
[Figs. 96 to 100.] 
Specific diagnosis. — Hymenolepis (p. 51) : Strobila lanceolate, 30 to 130 mm. long by 
5 to 18 mm. broad. Head, compared with strobila, very small; rostellum protractile, 
armed with single row of 8 hooks, 31 to 35 u long. Neck 
short, often retracted with head into anterior portion of 
strobila. Segments much broader than long throughout the 
strobila. Genital pores on right-hand margin of segment 
near anterior border. Three testes in each segment; vas 
deferens enlarged to form a seminal vesicle, frequently 
S-shaped, before entering cirrus pouch; within latter a sec- 
ond vesicle; vas deferens describes a complete loop in cir- 
rus pouch before being transformed into the cirrus; cirrus 
freely protrusible, armed with spines. Female organs on 
opposite side of segment from genital pore; gravid uterus 
sac-like, with out-pocketings, filling most of the segment. 
Egg oval or spherical, with two thin membranes separated 
by an intervening space containing a small amount of albu- 
minous substance; inner membrane occasionally with polar 
papillae; outer membrane 50 by 35// to 100 by 100// in 
diameter; inner membrane 30 by 25// to 40 by 25// in diame- 
ter; embyronal hooks 8 to 15// in length. 
Habitat. — Adults in intestine of tame duck (Anas boschas 
domestica); black duck 
( Anasobscura ) ; tame goose 
(Anser anscr domesticus); 
muscovy duck ( Cairina 
moschata)’, white-headed 
duck ( Erismatura leucoce- 
phala ); pocharl ( Aylhya 
ferina ); African teal (Ay~ 
thya nyroca ); red-crested 
pochard (Aylhya rufina ); 
flamingo ( Phceni cop terus roseus). Zschokke (1902) 
has recently reported one case in man (Homo 
sapiens). 
Development. — Not experimentally determined. 
Larval stage probably lives in small fresh-water Crustacea. 
Fig. 9G. — Head and strobila 
of Hymenolepis lanceo- 
lata. Natural size. (After 
Goeze, 1782a, pi. 20, fig. 23.) 
Fig. 97.— Head with retracted rostel- 
lum and anterior portion of II. lan- 
ceolata. Enlarged. (After Railliet, 
1886, 267, fig. 163a.) 
G eogk api i ic distribution. — England , 
Denmark, France, Germany, and Austria. 
^Synonyms. — Tania anserurn Frisch, 1727 [according to Rudolphi, 1810a] ; T. anseris 
Bloch, 1779 [according to Rudolphi, 1810a]; T. lanceolata Bloch, 1782a (not T. lanceo- 
lata Chabert,; not T. lanceolata Rosseter, 1891); T. acutissima Pallas, 1781, in part; 
T. la.nceola Batsch, 1786a; Hcdysis lanceolata (Bloch, 1782) Zeder, 1803a; Hymenolepis 
(Dilepsis) lanceolata (Bloch, 1782) Weinland, 1858; Drepanidotxnia lanceolata (Bloch, 
1782) Railliet, 1892; Hymenolepis (Drepanidotxnia) lanceolata (Bloch, 1782) Cohn, 
1899; Txnia- Drepanidotxnia lanceolata (Bloch, 1782) Dadai, 1900a. 
Bibliography.— For medical and zoological discussion, see Ransom, 1904. 
