bothriocephalic! worms and as such have thick-shelled eggs with an 
operculum or lid at one end. Such an egg has already been figured 
in a previous paper for a related worm, Diphyllobothrium latum, one 
of the dog tapeworms. Schistocephalus solidus, a tapeworm from the 
intestine of the duck, has similar eggs, the eggs being 44 to 54 microns 
long by 35 to 38 microns wide. 
Fig. 51. Hymenolepis anatina. Egg. Enlarged. From Braun, 1897, after Schmidt. 
The eggs of tapeworms belonging to the family Hymenolepididae 
have several thin, transparent shells or membranes, as a rule. In the 
case of Choanotaenia infundibulum (chicken, turkey; U. S.), the eggs 
(Fig. 50) are oval, with a thin membrane next to the onchosphere, then 
a thick, smooth membrane, and then one or two very thick outer mem¬ 
branes, 60 to 65 microns long by 40 to 45 microns wide, and with a 
delicate appendage at each pole. The eggs of Hymenolepis anatina 
F'ig. 52. Hymenolepis tennirostris. Egg. x 240. From Krabbe, 1869. 
(duck, swan) have the characteristic shape figured here (Fig. 51) and 
are 125 to 175 microns long by 90 microns wide. The eggs of H. tenui- 
rostris (duck, goose) are almost cylindrical and 85 microns long (Fig. 
52). Usually these tapeworm eggs are globular or subglobular to ellip¬ 
tical. The diameters of the eggs are given here in microns for the fol¬ 
lowing species: H. carioca (chicken, turkey; U. S.), 36 to 75; H. exilis 
(chicken), 56 to 65; H. cantaniana (chicken, turkey, peafowl; U. S.), 
51 
