(516 L- R- t'AHY, 



in the dietary of some Batrachian, would serve as the necessary 

 step between the encysted worm and the vertebrate host. With 

 such a cycle in mind, many of the aquatic forms taken in the waters 

 where infected snails were abundant were examined for the encysted 

 stage of D. femporafus. The only animal in which cysts or free 

 worms which might possibly be referred to this species were found 

 was one of the common "darters", (EtJieostomata s|).). These little 

 iish feed continually among- the rocks along the banks of the canal 

 where the infected snails abound, and can readily be taken with a 

 dip net. Nearly every one examined contained many Trematodes, 

 usually of several species. Some of these worms were identical in 

 appearence with young specimens of D. temporafus which had lately 

 left the cyst. These small fish are known to be taken as food by 

 the larger frogs, so there is thus shown a possible means of the 

 transfer. 



Another possible intermediate host would be the small tadpoles 

 which, after having eaten the cysts would be in turn eaten by an 

 adult frog. In this connection some observations made by Prof. 

 CoNKLiN on the encysted stage of Bistomnm airiventre are instructive. 

 The vertebrate host of this Trematode is a frog, toad or newt. 

 When young tadpoles were kept in the jars in which the encysted 

 worms were abundant the latter were taken up in large numbers 

 by the tadpoles. For some reason none of the young worms which 

 came from the cysts remained in the gut of the tadpoles, but all 

 of them made their way from the gut to some of the other organs 

 of the body, where they became once more encj^sted. None of the 

 organs of the body were free from the attacks of the parasite. 

 They were found in the spinal canal, liver, body wall etc. Some 

 of the tadpoles when sectioned were found to contain as many as 

 twelve encysted worms, so they would prove a fertile source of 

 infection if eaten by an adult frog, as very oftens happens under 

 natural conditions. 



The tadpoles used in these experiments were the young of 

 Uana virescens which can, in the adult stage, serve as the vertebrate 

 host of D. atriventre. From this fact it seems probable that there 

 must have been some reason connected with the size of the tadpoles 

 which caused the worms to migrate from the gut into the other 

 tissues. This occurence seems all the more singular when it is 

 compared with the behavior of the young worms of Biplodiscus 

 temporatus which had been taken into the digestive tract of tadpoles. 



