306 T. B. ROSSETER ON CYSTICERCUS VENUSTA. 



pond was teeming with organic life. The other duck I turned 

 down with the drake on his run, and systematically fed them 

 both with strainings from the pond, which I procured by weekly 

 visitations ; and on Saturday, the 26th September, I killed the 

 remaining duck from Gorstly Pond. The same evening, whilst 

 the body was still warm, I took out the whole of the viscera, 

 and on examining it found a cyst as large as a boy's marble 

 growing on the duodenum ; it was adhering to the mesentery 

 and the outer wall of the duodenum, and it was enveloped with 

 a thin membrane. I at once placed it in a hardening medium 

 to prepare it for cutting into sections. 



I first examined the contents of the duodenum. There were 

 a great number of T. tenuirostris, in various stages of growth, 

 making it their abode. As I proceeded down the alimentary 

 tract T. tenuirostris became more scarce and T. gracilis took its 

 place, and then as I drew near to that part of the tract where 

 the caecum is situated— in the ducks it is double or paired — 

 T. gracilis vanished, and not only the contents of the intestine, 

 but likewise the wall of the same was one mass of T. coronula 

 in various stages of growth, but beyond this the remaining 

 portion of the intestine was entirely free from the scolices of 

 these parasites. 



I spent eighteen hours in the examination of the viscera of 

 this duck, and the failure to produce the mature tape-worm of 

 this Cysticercus, for I did not find a single specimen, was 

 disappointing and somewhat disheartening, as each of the other 

 species of Cysticercus that were injected were looked upon in 

 the light of a control experiment, because they were not only 

 taken from the same pond, but, as I have said above, both 

 gracilis and coronula were commensal with it in the body 

 cavity of the Cypris. T. tenuirostris seems to exclusively make 

 the Copepods its host, as I have never seen it being nursed by 

 any other crustacean. 



Thus the third duck was a complete failure ! 



On Saturday, 18th October, I killed the drake isolated in 

 August, and fed from that date with this Cysticercus. On 

 examination neither gizzard nor duodenum contained Taeniae 

 of any description, but about two inches further down the 

 intestine I was fortunate enough to discover four specimens 

 of tape- worm, the product of, and identical with, my new 



