ramifications of the tubules of the excretory system of the 

 c^rcarla, work on this system in the redia was taken up. 

 This led to the search for other stages suspected to exist 

 in the life of this species. The species chosen proved 

 to be f r/orable for both types of work. 



METHODS OF 



o v - 



The solution of the life cycle was underlain in four 



*-* > v-. * - 



ways. The first method was that of examining carefully 



i J* - - y w?w v ** JL f-A v " 



a large number of snails, Physa ooci dental is Tryon, from 

 Stow Lake, Golden Gate Park, San Francisco, in which the 

 cercariae were present to see if there might not be found 

 other stages if studied during the entire year. Careful 

 examination of four hundred of these snails showed 86-3/4 

 per cent were infected with eithsr or both the encysted 

 agamodi stoines or rediae. In addition, one other stage, the 

 daughter redia, previously never reported for e chinos tomes, 

 was found. 



The second method was experimental. It consisted of 

 feeding large numbers of encysted agamo di s tc me s to white 

 mice, New Zealand rabbits, white leghorn chicks, and mongrel 

 ducklings. They were all protected in every way from other 

 trematc de infections, the last two being incubator hatched 

 and brooder raised. They were never allowed near water or 



soil, there being always a board floor in the brooder. 



!> 



Their food was also carefully selected. Negative results 

 were obtained from the experiments with the mice, rabbits 

 and chicks, buythe ducklings gave positive results. 



