Abstract: During the process of asexual reproduction of T. nobillis, all organelles except the striae were divided or developed before cell division. The micronueleus undertook mitosis to form two micronuclei. The macronucleus also underwent a series of morphologicall changes and finally divided. The new denticulate ring was developed as a delicate thread-like ring located between the old ring and the striate ring, then it was divided into sections usually twice as that of the old denticles in number and appeared to be somewhat tiling in arrangement. Half of the old ring retained in each daughter cell after cell division and then disppeared orderly. The adoral spiral and the contractile vacuole were also divided into two parts. Each new stria mingled with the old one so that the number of new striae are usually twice as many as the old ones. The time order of asexual reproduction of T. nobillis has also been investigated. Under the optimum temperature (22—29℃), the cycle of asexual reproduction of T. nobillis lasted 24 hours. Predivisional stage Iasted 0.5—1 hour and divisional stage, 1—3 minutes. Growth of young lasted 1.5—3 hours, of adult, 20—22 hours.