1 68 



ROBERT W. HEGNER. 



considerable period and if any changes in number, stage in life 

 history, color, etc., would take place. Table III. gives the dates 



TABLE III. 



NUMBER AND DISTRIBUTION OF EUGLENOIDS OF SPECIES A IN TADPOLES OF Rana 



pipiens COLLECTED JUNE 12 AND KEPT IN LABORATORY WITHOUT FOOD 



UNTIL DATE OF EXAMINATION. 



For method of counting see text. 



and results of examinations. One tadpole was used each day, 

 the last one being examined on the twenty-fifth day. During this 

 entire period the euglenoids persisted in the digestive tract, in 

 numbers at least as great as in tadpoles examined on the date of 

 collection. My method of counting (see p. 88) was not very 

 accurate, but it seemed to me that the number of euglenoids 

 was more numerous in tadpoles studied on later dates than at 

 first. In the meantime the other protozoa common in the rectum 

 of these tadpoles decreased markedly or disappeared entirely. 

 No encystment was noted in any of the specimens and only one 

 euglenoid was seen in division. 



The euglenoids retained their normal free-swimming shape 

 throughout the entire experiment, and were very active, swim- 

 ming about by means of their flagella or undergoing rapid meta- 

 bolic movements. No appreciable decrease was noted in the 

 intensity of the green color nor in that of the eye-spot. This was 

 probably due to the transparency of the ventral body-wall which 

 allowed light rays to enter. A few days after the tadpoles were 

 brought into the laboratory the rectum and intestine became 

 almost free from food material and their contents could easily 

 be seen through their walls. It was found that the euglenoids 



