THE REMARKABLE FAUNA OF A SINGLE DROP OF 



POND WATER. 



W. J. KOSTIR. 



Late in September, 1918, while collecting material for class 

 use, I obtained from the east pond of Mirror Lake on the Ohio 

 State University campus a quantity of brownish sediment so 

 rich in a variety of forms as to attract special attention. All 

 of the sediment in question was taken up by means of a long 

 pipette from a spot perhaps two inches square, where it covered 

 a layer of dead leaves on the bottom of the pond. The depth 

 of the water at this point was only a few inches; the locality 

 was one that was shaded by trees during part of the day. 



The material was not concentrated in any way, and was 

 examined almost immediately after it was brought into the 

 laboratory. In a single drop — the first o-ne examined — the 

 following forms were found to be present, all apparently in 

 healthy, normal, active condition: 



Amoeba. Two species; a larger one of the proteus type and a 

 smaller one of the Umax type. Several specimens of each. 



Arcella. A number of active specimens. 



Difflugia. Two different species, one specimen of each. 



Actinophrys. Several specimens. 



Euglena. Two species; the larger one£. deses, the smaller 



one not identified with certainty. Several of each. 

 Carteria. Many specimens of C. niultifilis. 

 Paramecium. Several specimens of P. caudatum. 

 Vorticella. Several specimens. 

 Stentor. A specimen of 5. coeruleus and one of a distinctly 



different (colorless) species. 

 Spirostomum. Two specimens of S. ambigimm. 



Several small flagellates and ciliates, not identified with cer- 

 tainty, were present in addition to these. 

 Two species of rotifers were present. They were not identified. 

 Hydra. One specimen of H. fusca. 



Ohio State University, Columbus, Ohio. 



