Wonderful shots of the contractile stalk. Excellent. (Super 100X quality!)
Possibly Zoothamnium or Carchesium. A few years ago I photographed something similar, and if you look at the ID discussion there (by folks who are better than I am in regards to ID) you may pick up some points that will help you determine what these are. http://www.photomacrography.net/forum/v ... php?t=6222