OBSERVATIONS AND EXPERIMENTS ON EUGLENOIDINA., 



out of the digestive tract and placed in culture dishes did not live 

 and multiply. This does not prove that they cannot maintain 

 themselves outside of the digestive tract of the tadpole but indi- 

 cates that they probably are restricted to an entozoic existence. 



Y. Can Tadpoles of Rana pipiens be Infected with Free-living 

 Euglenoids? It has been shown above that Species A can be 

 transferred from one tadpole to another with the food, therefore 

 if free-living species can live successfully in the digestive tract 

 of these tadpoles it should be possible to bring about infection by 

 including them with the food. On June 24, twenty-five tadpoles 

 of Rana pipiens about nine weeks old were placed in a culture 

 containing millions of small free-living euglenoids of a species 

 possessing 2 short flagella, obtained from a large tub at the fish 

 hatchery. In 18 hours these tadpoles had eaten every euglenoid 

 in their medium. At this time five of these tadpoles and an equal 

 number of controls were examined. The rectum of the experi- 

 mental tadpoles was of a deep green color and the intestine also. 

 Not a single specimen of the free-living euglenoids, however, 

 could be found in any of these five tadpoles. The greenish color 

 was due to minute chlorophyll bodies from 3 ^ to 8 /x in diameter. 

 These were the chromatophores of the disintegrated euglenoids. 

 Chlorophyll bodies of this type were entirely absent from the 

 five control tadpoles examined at the same time. In both experi- 

 mental and control tadpoles there were present a few euglenoids 

 of Species A and a few of a species to be described later as Species 

 B. Experimental and control tadpoles were examined on the 

 second day (5 specimens), fourth day (2), and eighth day (i). 

 No euglenoids of the free-living type were discovered. The 

 chlorophyll bodies gradually decreased in number. The conclu- 

 sion reached is that an essential difference exists between eugle- 

 noids of Species A and those of this free-living type, the former 

 being able to withstand the digestive juices of the host and to 

 maintain themselves within the digestive tract, whereas this 

 free-living species is unable to live in the same environment 

 being killed and digested by the tadpole. 



A second experiment was carried on at Baltimore during the 

 month of September. Five tadpoles of the green frog that con- 

 tained very few euglenoids were placed in a small amount of 

 water in which there were thousands of a large reddish-colored 



