612 L- R. Oary. 



comes into the water the outer layers of the tail swell, and as they 

 increase in size push forward over the body "enclosing it as in a 

 wall". When the cyst has come to reach as far forward as the 

 ventral sucker, the animal contracts and decreases the size of the 

 anterior end of the body around which the cystforming- material 

 is extended until a complete capsule is formed. It would seem from 

 Reüss' description that the cercaria becomes encysted without having- 

 become attached to any substratum. 



Part IL 

 Experimental deteriMinatiou of the life history. 



When the cercariae began to be liberated from the snails kept 

 in the laboratory, and the manner of their encystment was observed, 

 it became apparent that some animal which obtains its food by 

 browsing over stones, water plants etc. along the banks of streams 

 would probably be the next host of this parasite, whether or not it 

 would prove to be the final one. The larvae of frogs, toads, and 

 newts immediately suggested themselves as animals having such 

 feeding habits. 



On Oct. 30 a number of tadpoles of Baua cateslnaua were secured 

 and several put in each jar containing infected snails. The tadpoles 

 came from a pond in the grounds of Biological Hall at the Uni- 

 versity of Pennsylvania, where Goniohasis is not found, so it seemed 

 improbable that they would be infected with the parasite which 

 was found about Princeton. As an added precaution all of the 

 tissues of three of the tadpoles were carefully examined without 

 finding parasites of any kind. When the tadpoles had been for a 

 week in the jars containing the encysted cercariae, a dead individual 

 was found. This one was examined for the presence of parasites 

 with the following results: nine worms, which from the condition 

 of the sexual organs could be recognized as young, were found in 

 the intestine of this tadpole. The other organs of the body were 

 entirely free from parasites. The worms in the intestine were about 

 2-5 mm. in length and 1 ram. in diameter at the posterior end. All 

 ot them were found in the last third of tiie intestine of the tadpole, 

 scattered throughout that part of its length. During the time while 

 they were under examination, as was also true in every other 

 instance, the worms remained attached to the intestine of the host 



