400 T. B. ROSSETER ON EXPERIMENTAL INFECTION OF DUCKS. 



Description of Cysticercus. 

 Cyst : oval. 



Diameter of cyst: length, 0*211 ; width, 0*109 mm.* 

 Number of hooks on embryonic rostellum, 8. 

 Size of hooks : 0*075—0*078 mm. 

 Character of hooks : sickle-shaped. 

 Habitat : Cypridse and Cyclopidae. 

 Final-host : domestic duck {Anas boschas), figs. 5, 6, 7, 8. 



"Yon Linstow, 1872, found a Cysticercoid in the intestine of a 

 perch (Perca fluviatilis), which he looked upon as the young of 

 Taenia gracilis. The larva has also been found in certain fresh- 

 water crustaceans, which probably represent the regular inter- 

 mediate host. Thus Scott, 1891, noticed an object in a mounted 

 slide of Candona prostrata (Brady & Norman). Blanchard, 1891, 

 examined Scott's preparations, and, after careful comparison of 

 the hooks of the Cysticercoid, concluded that this larva belonged 

 to the life-cycle of Tamia gracilis. Marazek cites the larva for 

 Cypris compressa and Cyclops viridis. 



tl The larva referred to is in all probability the true larva of 

 this species, but no infestations have as yet been made." — Stiles, 

 loc. cit. 



Drepanidotcenia tenuirostris (Rudolphi, 1819); Railliet, 1893 



(1819, Taenia tenuirostris, Rudolphi). 

 Cysticercus tenuirostris (Hamann, 1889; Yon Linstow, 1892); 



Rosseter, 1896. 



Description of Cysticercus. 

 Cyst : oval, at times globular. 



Diameter of cyst : length, 0*211 ; breadth, 0*180 mm.t 

 Number of hooks on embryonic scolex, 10. 

 Size of hooks : 0*023 mm. 

 Character of hooks : sickle-shaped. 

 Habitat : Gammarus pulex ; Cyclops agilis. 

 Final- host : domestic duck [Anas boschas), figs. 9, 10, 11, 12, 

 13, 14. 



* This Cysticercus varies very much in size. 



f This is the mean of six specimens. I have some perfectly glol ml ar. 

 whose diameter is 0*230 mm., and another 0*211 mm. These cysts vary in 

 size, but their characteristics are unmistakable, owing to the depth of the 

 fluid cavity, which is 0*026 mm. 



