OBSERVATIONS AND EXPERIMENTS ON EUGLENOIDINA. 175 



infect one another even in a large pond. Tadpoles of other 

 species are much less accustomed to congregate in numbers and 

 hence would not transfer their infection unless confined to a 

 small body of water. 



VIII. Species A in Tadpoles of the Green Frog, Rana clamitans. 

 Euglenoids of Species "A" were encountered in very small 



numbers in tadpoles of the green frog. For example, several 

 specimens were found in the rectum of each of four tadpoles 

 that were collected on June 14 and kept in the laboratory without 

 food until June 26. That these euglenoids may be taken in with 

 the food of the tadpole and localized in the rectum is evident 

 from the following experiment. One tadpole of the green frog 

 collected on June 14 was starved until June 28 and then fed the 

 rectal contents of three toad tadpoles containing euglenoids. 

 Two days later a considerable number (two per field) of Species 

 A were found in the recutm of this specimen a much greater 

 number than had been found in any of the several hundred other 

 green frog tadpoles previously examined. Furthermore most of 

 these specimens were pale in color like those in the toad tadpoles 

 at this time. 



IX. Specificity of Euglenoids of Species A. It seems probable 

 from the observations and experiments recorded above that 

 euglenoids of Species A are "normal" inhabitants of the recutm 

 and intestine of tadpoles of the frogs and toads that inhabit 

 freshwater ponds. Those living in different hosts may be specif- 

 ically distinct but no evidence of this was obtained. Attempts 

 to infect adult salamanders proved negative. Ten infected toad 

 tadpoles were fed to a specimen of Diemyctylus viridescens on 

 July i. Four days later no traces of euglenoids could be found in 

 the digestive tract of this specimen, indicating that this sala- 

 mander cannot be infected with its food and that these euglenoids 

 are probably unable to live in adults of this species. Another 

 specimen of this species of salamander was placed in a dish con- 

 taining millions of free-living euglenoids. Four days later, the 

 intestine of this animal contained green chlorophyll masses, but 

 no recognizable euglenoids. 



X. Euglenoids of Species B. A second type of euglenoid was 

 noted in the rectum and intestine of tadpoles of Rana pipiens 

 and R. clamitans. Euglenoids of this species, which may be 



