T. B. ROSSETER ON EXPERIMENTAL INFECTION OF DUCKS. 399 



to him. I hope by my mounted specimens, drawings and state- 

 ments in this paper, to convince you, and through the medium of 

 the Transactions of the Quekett Club, Dr. Stiles as well, that 

 these particular Cysticercoids which he overshadows by " proba- 

 bility " and " possibility," are the actual Cysticercoids, or as he 

 calls it the larval stage of the above-named tapeworms. 



I will first briefly describe these Cysticercoids from my own 

 collection, and afterwards quote the remarks passed by Dr.. Stiles 

 in his work in connection with them. 



1. Dicranotcenia Coronula (Dujardin, 1845); Railliet, 1892 (1845, 



Tcenia coronula Dujardin). 

 Cysticercus coronula Marazek, 1890; Rosseter, 1890 and 1896. 



Description of Cysticercus. 

 Cyst ... ... ... ... ... ... Globular 



Diameter ... ... ... ... ... 0*172 mm. 



Number of hooks on embryonic rostellum ... 20 — 24 

 Size of hooks ... ... ... ... ... 0*014 mm. 



Character of hooks : bifurcated or pitchfork-shaped. 

 Habitat : Cypridse and Cyclopidse. 

 Final-host (Anas boschas dom.), figs. 1, 2, 3, 4. 

 " Several authors have found larval cestodes in fresh- water 

 mussel-crabs, which they look upon as the young stage of 

 Dicranotainia coronula, 



" Marazek has foiiDd a Cysticercoid in Cypris ovum Jur., and 

 in Cypris compressa Baird, whose hooks correspond in form, di- 

 mensions, and numbers to those figured by Krabbe ; the tail is 

 3-5 times as long as the body, and bears the six hooks — 8 fx long — 

 of the Oncosphere." 



" Kosseter describes and figures the Cysticercoid of Dior. 

 coronula from Cypris cinerea in Kent, England. 



" While this Cysticercoid is very similar to Dicr. coronula, and 

 that in all probability it represented its larval stage, it must not 

 be forgotten that the experimental proof of the relationship of 

 these organisms has not yet been forthcoming ; and, furthermore, 

 that even the adult form is very imperfectly described." — Stiles, 

 loc. cit. 



2. Drepanidotcenia gracilis ([ ? Zeder, 1803]; Krabbe, 1869); 



Railliet, 1893 (1869, Tcenia gracilis, Krabbe.) 

 Cysticercus gracilis (Yon Linstow, 1872); Rosseter, 1896. 



