342 THE BIOLOGY OF STENTOR 



are cut off to proper length and diameter with scissors and a piece 

 of thick-walled rubber tubing, plugged with glass rod, slipped on as 

 a bulb which will not be over-responsive to pressure of the fingers. 

 These pipettes are unbreakable and can be used for years if cleaned 

 out occasionally by passing a twirling fine wire through the points. 



Sample dishes are now searched and individual stentors picked 

 up and transferred to glass block cells, one for each species if 

 desired. About 50 stentors of a kind should be isolated, if available, 

 and the isolation dish should then be surveyed, this time to 

 pipette out any contaminating organisms that may have been 

 carried over with the stentors. Block cells or their equivalent are 

 recommended because in them no organism escapes from view. 



Enemies of Stentor and reports of their predation include the 

 following: the heliozoan Actinosphcerium eichhornii (Cienkowski, 

 1865) 5 the water plant Utrichularia which captures and kills stentors 

 in its unique bladders (Hegner, 1926); rhabdocoele worms 

 (Prowazek, 1904; Gelei 1925); oligochaete worms like Chcetogaster 

 diaphanus (Lankester, 1873); the giant ciliate Bursaria truncatella 

 (Lund, 1914) ; and the smaller ciHate, Dileptus, with its proboscidial 

 stinging trichocysts. I have observed that the little scavenger 

 ciliate, Coleps, devours injured stentors; and nematodes, water 

 fleas, and hypotrichous ciliates are to be excluded as predators or 

 otherwise undesirable. 



2, Culturing 



I shall now describe my method of setting up cultures, though 

 this is not the only nor possibly the best procedure. A half-pint, 

 wide-mouthed peanut butter jar is filled to a depth of about one 

 inch with the filtered pond water. A large pinch of absorbent cotton 

 is then pulled apart to form a loose mesh and dropped in. The 

 cotton is regarded as a purified substitute for pond vegetation. 

 The isolated stentors are then washed into the jar with a squirt of 

 filtered pond water. One drop of skimmed milk, one or two boiled 

 wheat or rice grains, or fragment of a rabbit-food pellet is then 

 added as a source of nutrients, producing a population of bacteria 

 and tiny flagellates and other food organisms from the original 

 pond water which passed through the filter paper. In this way as 

 many seeding stentors as obtainable are returned to the same water 

 from which they came. Only about 100 ml of starting culture is 



