DeveJopmeiif 



87 



budding («) to cei'cariai, or (b) to other redioe which ultimately 

 give a brood of cercaria^. 



These four hnes of development which may be taken by a 

 digenetic trematode are graphically tabulated in fig. 40. 



From the account already given of the experimental production 

 of adult Bilharzia worms after submission of a suitable definitive 



: -'^^ 



^s /:i 



'^. J 



Fig 41. -A sporocyst from Planorbis containing (hiugliter-sporocysts. On the 

 right is a free daughter-sporocyst. 



n 



rp^ 



Fig. 42.— Daughter-sporocysts teased from Liver. 



host to infection by cercariae, it was evident that bilharzia 

 development probably followed one or other of these alternative 

 courses. In fact, the Bilharzia worms are typical digenetic trema- 

 todes, and conform to the second type of development in the 

 intermediary host. 



The Bilharzia miracidium gives rise to a sporocyst, which in 

 turn produces daughter-sporocysts (fig. 42). 



