54 



The Rot in Sheep. 



which have helped rather to mystify the subject than to render 

 it plain. Most cercaria-s&cs are of simple organisation ; but, 

 notwithstanding this, they are found of various forms, according 

 to the kind of cercarice to be developed within them. 



In the accompanying illustration {fig. 10) we have repre- 

 sented the sac of the Cer carta ephemera, copied from Huxley's 

 translation of Von Siebold's work, "a" represents the oral 



Fig. 10. 



Cercaria-sac, showing the formation of Cercaria?. After Huxley. 



cavity of the cyst ; b, the alimentary canal ; c, a developed 

 cercaria ; and d, other cercariw 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 cercaria?. These young are developed, not 



Fig. ll. 



Magnified view of the development of Cereariaj. After Huxley. 



