603 



Anas boschas feia," the laltfr being in a bottle with others 

 which appeared to be T. rhoniboidea. Friis found the same 

 worm in wild ducks in Schleswig, and Gad and Krabbe found 

 it in tame ducks in Zealand. The worm was found three 

 times in 100 tame ducks. Krabbe (1S82, p. 353 states that Pro- 

 fessor Reinhart found this same species in 1874 in Anas acuta 

 [ — Dafila acuta] taken in Zealand. 



Mrazek (1891, pp. 110-113) describes a cysticercoid which he 

 found in Bohemia in Cypris incong-ruens and Cypris compressa 

 Baird (according to Moniez, 1891, Cypria ophthalmica); the larva 

 measured 0.40"i»> to 0.43""", and bore 10 hooks 65 fi long; the 

 tail was very long; embryonic hooks measured 10 /t. Moniez 

 (1891, p. 26) states that he found the same larva in Cypris in- 

 congruens at Lille, France, and that the species T. anatina is 

 the mosit common tapeworm of domesticated ducks of that 

 country. 



It is to J. E. Schmidt (ISDl) that we owe our chief 

 knowledge of this worm and the experimental demon- 

 stration of its life history. Schmidt infected numer- 

 ous small 2.25"™ to 2.75'""' freshwater crustaceans 

 (Cypris ovata) with the eggs of adult animals taken 

 from ducks, and followed the development in all its 

 stages. He found that the ova are eaten by Cypris; 

 the embryo escapes from its shells and passes into the 

 body cavity of the intermediate host; here it growls into 

 a roundish hollow ball which gradually elongates and 

 develops the various organs of the cysticercoid; when 

 the organs are formed, the larva retracts its scolex into 

 its cyst. In summer the entire development of the 

 cysticercoid lasts but two weeks, while in winter it 

 lasts over five weeks. 



Ducks naturally become infected by swallowing \\\v 

 mussel crabs. 



