1 70 



ROBERT W. HEGNER. 



TABLE IV. 



COMPARATIVE NUMBERS OF EUGLENOIDS OF SPECIES A IN THE RECTUM OF TAD- 

 POLES OF Rana pipiens USED AS FOOD AND IN CONTROL AND 

 EXPERIMENTALLY FED TADPOLES. 



probably all in the free-swimming stage it seems certain that 

 infection of Rana pipiens tadpoles can be brought about by the 

 ingestion of active trophozoites. Such a method of infection 

 might occur in nature since tadpoles will feed upon the dead 

 bodies of other tadpoles, but this is probably not the usual method 

 since 100 per cent, of infection has been observed in entire schools 

 of young tadpoles, and, of course, there must be a resistant stage 

 for maintaining the race through the winter and for infecting the 

 first tadpoles in the spring. 



IV. Can Euglenoids of Species A be Cultivated Outside of the 

 Body of ths Tadpole? The data presented above indicate that 

 the euglenoids of Species A are regular inhabitants of the diges- 

 tive tract of Rana pipiens tadpoles. The questions suggested by 

 these results are; (i) are these euglenoids restricted to this habitat 

 or can they also maintain a free-living existence; and (2) car; 

 other euglenoids known to be free-living be colonized in the 

 rectum and intestine of tadpoles of this species. Two methods 

 of answering these questions were employed: (i) an attempt was 

 made to cultivate Species A outside of the body of the tadpole, 

 and (2) tadpoles were fed on freeliving euglenoids and their 

 digestive tract examined on subsequent days. 



Euglenoids of Species A remained alive and active for at least 

 48 hours inside of the digestive tract that had been dissected out 

 of tadpoles and kept in a small dish in water. Specimens also 

 remained alive for 72 hours in material from the rectum and in- 

 testine under a sealed cover glass. Specimens that w r ere dissected 



