156 RUEDIGER. 



Result of microscopic examination made May 19: No amoebfe, no ciliates, but 

 swarming with flagellates. 



3. May 16. — A sample of 1,000 cubic centimeters of water from the water 

 coolers at the camp was put into a sterile flask, and the method outlined above 

 was followed out. Result of microscopic examination May 19: No amoebae, no 

 flagellates, but a large number of ciliates were present. 



The results obtained with samples 2 and 3 at once attracted my atten- 

 tion. Water from the coolers which previously had been in the receiving 

 cans yielded ciliates and no flagellates, while the water from the receiv- 

 ing cans yielded flagellates, but no ciliates. The appearance of ciliates 

 in water from the coolers is explained readily by assuming that the 

 ciliates were in the coolers when the latter were filled, or that they 

 entered that water in some other manner while the receiving cans had 

 remained free from them. However, the disappearance of the flagellates 

 which were present in the water from the receiving cans and absent 

 from the water in the coolers was not so readily explained and became 

 the subject of some study. 



EXPERIMENT 1. 



May 21. — About 10 cubic centimeters of sample 2, containing a large number 

 of flagellates, was put into a sterile test tube and about 10 cubic centimeters of 

 sample 4, containing a large number of ciliates, was added. On microscopic 

 examination many flagellates and ciliates were found. On May 22 microscopic 

 examination showed a large number of ciliates, but no flagellates. On IMay 23 

 microscopic examination showed many ciliates, but no flagellates. 



EXPERIMENT 2. 



May 23. — ^A clean bottle of 250 cubic centimeters capacity was nearly filled 

 with water, and about 10 cubic centimeters of melted nutrient agar was added 

 and sterilized. After cooling, a few cubic centimeters of sample 3, rich in 

 flagellates, and a few cubic centimeters of sample 4, rich in ciliates, were added. 

 Microscopic examination made immediately showed a small number of flagellates 

 and a small number of ciliates. 



May 24. — On microscopic examination, a moderate number of flagellates and a 

 moderate number of ciliates were found. 



May 25. — Microscopic examination revealed ciliates but no flagellates. 



May 26. — -Many ciliates, but no flagellates. 



May 27. — ^A large number of ciliates, but no flagellates. 



May 28. — Many ciliates but no flagellates. 



EXPERIMENT 3. 



May 30. — One large platinum loopful of water rich in flagellates was put into 

 the cavity of a hollowed microscopic slide, three loopfuls of water rich in ciliates 

 were added, and a cover glass placed over the cavity. Microscopic examination 

 made immediately after mixing the two showed a large number of ciliates and 

 a moderate number of flagellates. On examining the mixture two hours later, 

 ciliates only were found, all flagellates having disappeared. 



May Si.— 'Microscopic examination made about twenty-four hours after mixing 

 the two showed all ciliates encysted; flagellates were not seen. 



