592 



lung. Antei'ior segments very short; following segmenlis grad- 

 ually increase in size. Genital pores unilateral. Penis 60 ^ 

 to 80 u (Duj.) 110 fi (Krabbe) long by 30 u to 53 « broad, but 

 able to swell to 80 n covered with minute spines. Hooks of 

 embryo 8 fi. Internal anatomy? 



Development: Cysticercoid, probably in mussel crabs (Cy- 

 pris ovum Jur., Cypris cinerea, Cypria ophthalmica Jur. and 

 Candona Candida. 



Hosts: Tame ducks (Anas boschas dom.); Mallard duck (A. 

 boschas L.); European Golden Eye (Glaucionetta clangula). 



Geographical distribution: France (at Rennes, by Dujardiii; 

 at Alfort, by Railliet); Denmark (in Zealand by Krabbe); Gei- 

 many (in Bavaria by von Siebold, after Krabbe; in Munich by 

 von Willemoes-Stihm, after Krabbe, 1882). No epidemics re- 

 ported. 



Dujardin (1845, p. 574) described this species from parasites 

 found in ducks at Rennes; Krabbe (1869, pp. 317-318) found the 

 same species in domesticated ducks and adds a few observa- 

 tions, chiefly measurements; he pites it from Siebold's collection 

 (from Glancionetta clanula) and in 1882, p. 356, cites it from von 

 Willemoes-Suhm (from Anas boschas fera). Railliet (1893, p. 

 303) has found young tapeworms in the domesticated duck at 

 Alfort, which he determined as belonging to this species, al- 

 though the dorsal root of the hooks were much more slender 

 than those figured by Krabbe. These appear to be the only 

 observations upon the adult worm, which as at present diag- 

 nosed, is based entirely upon external characters, and which, 

 therefore, should be restudied anatomically. 



Several authors have found larval cestodes in fresh-water 

 mussel crabs which they look upon as the young stage of Dicr. 

 coronula. 



Mrazek (1890) [in a publication which on account of the lan- 

 guage I am unable to read, I quote from Moniez (1891, p. 26) 

 and Railliet (1893)] has found a cysticercoid in Cypris ovum 

 Jur. and in Cypris ophthalmica Jur. (Cypris compressa Raird) 

 which measures 140 « to 190 u in diameter, and is provided 

 with 22 to 31 hooks corresponding in form and dimensions to 

 those figured by Krabbe, except that the dorsal root is some- 

 what more slender; the tail is 3 to 5 times as long as the body 

 and bears the 6 hooks (8 /« long) of the oncosphere. Rosseter 

 (1890) describes and figures the cysticercoid of D. coronula from 

 Cypris cinerea in Kent. Moniez (1891, p. 26) states that this 

 cysticercoid is rather common in France, where he has found 

 it in Cypria ophthalmica and Candona Candida; he also records 

 it in Cy. nphthalmiia from Durham and from China. 



