Transi 



39 



crossing (fig. 11), in front of the cafes (fig. 5), and at a bend in the 

 canal specially used for washing, which is illustrated in fig. 10. 



The same species of mollusc was quite common at some 

 distance from the village in the agricultural drains away from foot- 

 paths, but was not infected. Nearer the village, however, and 

 especially where crossed by public paths, these drains contained 

 infected snails (fig. 13). So far the molluscan intermediary has 



Fig, 



13. — A typical agricultural drain on the outskirts of Mar§ 

 snails. 



containing infected 



not been found in birkets, but it occurs not uncommonly in large 

 marshes such as that, lying to the south-west of Ismailia, which is 

 illustrated in fig. 14. 



Once a bifid-tailed cercaria has been placed in the bilharzia 

 group on account of the absence of pharyngeal bulb, further 

 determination of its systematic position can only be effectively 

 established in the first instance by experimental infection of a 

 susceptible host and the subsequent examination of the adult worm 

 resulting therefrom. 



