The Rot in Sheep. 
115 
In the accompanyiiif? illustration [{fig. 10) we have repre- 
sented the sac of the Cercaria ephemera, copied from Huxley's 
translation of Von Siebold's work. In it a represents the oral 
Fig. 10. 
Cercaria-sac, sliowiug the fonnation of Cercaria;. After Huxley. 
cavity of the cyst ; b, the alimentary canal ; c, a developed 
cercana ; and d, other cercaria; in the course of formation. In 
his description of these organisms Von Siebold remarks that " the 
whole of these multifariously-shaped cercaria-sacs enclose within 
the walls of their bodies a cavity which, besides the intestinal 
ccecum (where such a structure exists), contains nothing but 
young cercarice. These young are developed, not from ova, but 
from gemma:, which differ essentially from ova. They are solid, 
round, and somewhat flattened discs, which, growing and de- 
veloping, become little caudate worms, resembling in form and 
organisation certain Trematoda (Distoma, Monastoma, &c.). 
Fig. 11. 
Magnified view of the development of Cercaris. After Huxley. 
I 2 
