Description of Lacrymaria olor: Predatory ciliate, 300-500 x 20-30 microns, trunk length about 100 microns, fully stretched cells to 1200 microns long. Trunk usually slim and spindle shaped. Neck very thin and strongly contractile and/or flexible. Anterior end with a small head and an oral bulge. Two ellipsoidal to spherical macronuclei in the centre of the cell, between them lies the ellipsoidal micronucleus. One contractile vacuole each in the rear and front end of the trunk. With 2-3 microns and 10-12 microns long toxicysts in the oral swelling and in the head . Between the ciliary rows are about 8 rows of very small mucocysts. The close-knit ciliary rows at the head form a strong ciliary bundle.