OBSERVATIONS AND EXPERIMENTS ON EUGLENOIDINA. 163 



euglenoid flagellate that I shall call Species A*, is a constant in- 

 habitant of the tadpoles of Rana pipiens from Ithaca, N. Y., 

 and that it may be a factor in the failure of certain specimens to 

 grow and undergo metamorphosis normally. So far as I have 

 been able to learn, this species has not been described although 

 Alexeieff (1912) noted what may have been specimens of this 

 form in the intestines of tadpoles. It is cylindrical and elongate 

 with blunt anterior and posterior ends and decidedly metabolic. 

 It ranges in length from 35 fj. to 45 M and in breadth from 4.8 fj. 

 to 6.4,u. The average length of ten specimens was 39.7^1 and 

 average breadth, 5.3 M- There are three flagella almost as long 

 as the body and about 50 green chromatophores, oval or circular 

 in outline, lying in a single layer near the surface of the body. 

 The nucleus is spherical and situated near the center of the 

 body. Near the anterior end is a large spherical reservoir open- 

 ing to the outside through a cytopharynx. At one side of the 

 reservoir is the red stigma. Figs. I to 3 are of three specimens 

 drawn with the camera lucida at a magnification of 1600 diame- 

 ters. The specimen in Fig. I was living when drawn, in Fig. 2, 

 killed and stained with iodine, and in Fig. 3, fixed in Schaudinn's 

 fluid and stained by the iron-haemotoxylin method. 



The tadpoles were collected in artificial ponds at the fish hatch- 

 ery of Cornell University at Ithaca, N. Y. My attention was 

 directed to their study by Dr. G. C. Embody, who had noted the 

 small size of specimens in one pond as compared with those in a 

 neighboring pond only six feet distant. These ponds were about 

 4 feet square and 18 inches deep. One was well filled with algae 

 and the other was almost free from vegetation. Egg masses of 

 Rana pipiens had been placed in these two ponds by Dr. Embody 

 at approximately the same time, about April 20. The tadploes 

 were collected seven weeks later (June 8). In Tables I. and II. 

 are presented data regarding the differences (i) between the two 

 sets of tadpoles and (2) between their rectal contents. The 

 following points may be noted. 



i. Size. (Table I.) Although the two groups of tadpoles 



* After this paper was written I learned that Dr. D. H. Wenrich had also spent 

 the summer of 1922 studying this organism. His work was largely devoted to its 

 morphology and cultivation. He has given it the name Euglenamorpha hegneri. 

 (Wenrich, 1923). 



