Development 



91 



Description of Bilharzia CERCARiiE, 

 The various trematode larvse found in each genus of fresh-water 

 molluscs in Egypt are tabulated according to this classification and 

 are described in a succeeding part. Their chief interest in relation 

 to the present inquiry lies in their similarity to the Bilharzia 

 cercariae. 



i 



.^N 



Fig. 45. Fig. 46. Fig. 47. 



Various Bilharzia cercarite found in molluscs around Cairo. 

 Figs. 45, 4G, in Planorbis boissyi. Fig. 47, in BuUinus dyboicski. 



When bilharzial cercariae are seen floating in water the most 

 noticeable character is the presence of a Y-shaped tail. This 

 character is common to the group lophocerca and to the furcocer- 

 cous division of the distomes. In the former group the ventral 



