00 1 



Auus boschas doiii. The oulv i)i>silivcl v Uiiowu host 

 foi- the adult up to Krabbe's time is. therefore, the 

 tame duck. 



Von Linstow (1872 A, pp. 535-537) afterwards found a worm 

 in the goosander (Merganser merganser [Mergus merganser]) 

 which he identified with Krabbe's species. Lonnberg (1889, pp. 

 9-10, fig. 1) found a worm in Tadorna vulpanser which he de- 

 scribed as a new variety: T. gracilis forma Tadornae. The 

 hoolis on this worm were much larger than those of the type 

 specimen, a variation which Lonnberg explains as due to host 

 influence. Lonnberg (1890, pp. 10, 30) also records this form for 

 Mergus serrator (^= Merganser serrator). 



Von Linstow (1872A, pp. 535-537) found a cysticercoid meas- 

 uring 0.14 by 0.09"ini in intestine of a perch (Perca fluviatilis), 

 which he looked upon as the young of Taenia gracilis. The 

 larva has also been found in certain fresh-water crustaceans 

 which probably represent the regular intermediate host. Thus 

 Scott (1891, p. 314) noticed an object in a mounted slide of Can- 

 donarostrata Brady & Norman, from, the Edinburg district; 

 Blanchard (1891A, pp. 303-332) examined Scott's preparation 

 from Candona rostrata, and after a careful comparison of the 

 hooks of the cysticercoid concluded that this larva belonged 

 in the life cycle of Taenia gracilis. He exiplains von Linstow's 

 linding this same larva in a perch by the fact that the fish 

 had eaten some ostracodes. He introduces the formula — the 

 length=:a — c, the base^a — b, in measuring the hooks, using it 

 as follows: For T. gracilis ab: ac=30-75. Mrazek (1891, p. 128) 

 cites the lar\'a for Cypris compre-ssa Baird and' Cyclops viridis 

 Fisch, while Moniez (1891, p. 26) mentions it from Cypria oph- 

 thalmica from China. 



The larva referred to is in all probability the true 

 larva of this species, but no infections have as yet been 

 made. 



b. Rostellum with 10 hooks. 



13. DREPANIDOTAENIA A.VATINA (Krabbp. 1869) RallliPl. 1S93. 



(18tjH, Taenia. unaliiKi Kialibe.) 



[PI. IX, figs. 100-111; PI. X. figs. 112-115.1 



Diagnosis: Stroblla attains 209iii'ii to SOOmm in length and 

 2mm to 3"i'i' in breadth; worm of TOmin in length has about 



