Irwin Loops and Other Tools In the literature you will run across reference to Irwin Loops. These are small loops constructed of wire, mounted in a wood handle. They were used by limnologists for plankton, and also used for mites and tardigrades. There appears to be no commercial source of these at present, which is unfortunate. They are extremely useful when making slides. There is one person in the U.S. who makes them by hand. Very small diameter pipettes (of the capillary tube size) are also useful when isolating tardigrades.