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



district (Canterbury ), and is frequently commensal with C. 

 coronula. 



Unlike Hamann and Von Linstow, I have never seen Cysticer- 

 cus tenuirostris making Gammarus pulex its resting stage ; and I 

 did not discover it being nursed by Cyclops agilis until 1894 ; in 

 fact, I have never found it parasitic in any other crustacean. It 

 is far from being common in duckponds in this district. 



So far as regards Cyst, gracilis and Cyst, tenuirostris, like my 

 colleagues, Drs. Blanchard, Yon Hamann, and Von Linstow, I 

 diagnosed them by comparing the hooks and their dimensions with 

 the description and figures given by Krabbe of the hooks of the 

 Taenia, as being the larval form of these specific tapeworms ; and 

 my feeding experiments with these two Cysticercoids and that of C. 

 coronula have proved both them and myself to have been correct 

 in our decision. I have never experienced any difficulty in pro- 

 ducing, by infestation, the mature tapeworm from these Cysticer- 

 coids in ducks. 



For my method of infestation of ducks I must refer you to my 

 paper read before you in November last (1896), when I explained 

 to you that all three of these Cysticercoids had been used by me 

 in feeding ducks with Cysticercoids so as to produce Drepanido- 

 twnia venusta (Rosseter), somewhat in the light of a " control 

 experiment " so far as production by direct infestation was con- 

 cerned, and I have in that paper stated and given a resume of the 

 localisation of these Taenia in the alimentary tract of the domestic 

 duck. By " control experiment " I do not mean to assert that 

 influence was exercised to facilitate or retard the production of 

 the tapeworm by using these Cysticercoids as a factor in the 

 development of the unknown Taenia from its Cysticercus ; but the 

 Cysticercus being nursed by the same crustacean as the Cysticer- 

 coids (?) of Die. Coronula and Drep. gracilis and communal with 

 them, it was assumed, and rightly, that their presence in the 

 nurse being known and their development in the duck ascertained, 

 feeding them to the duck would furnish a clue to the solution 

 of the problem of " Infestation," and serve also as an index 

 in examining the alimentary tract for the Taenia, the product of 

 the new Cysticercus — C. venusta. Cyst, tenuirostris, with its 

 exclusively selected nurse Cyclops agilis f was also added, and by this 

 means direct infestation was produced with these three Cysticer- 

 coids, and the results in each instance, with their respective 



