A soil urostylid ciliate Extraholosticha sylvatica, isolated from southern China, is studied using live observation and protargol impregnation. The main ontogenetic features of E. sylvatica are as follows: (a) in the proter, only the posterior part of the parental adoral zone of membranelles is renewed, while the anterior portion is retained; undulating membranes anlage undergo, like most hypotrichs, depolymerization of old undulating membranes and differentiation of new structures; (b) the oral primordium in the opisthe and the frontoventraltransverse cirral anlagen in both daughter cells are formed with contribution of the parental midventral cirri; (c) three frontal, one buccal, three to five frontoventral, one or two frontoterminal, two or three pretransverse ventral and six to 11 transverse cirri and 16–22 midventral pairs are generated from frontoventral-transverse cirral anlagen; (d) in both the left and the right marginal rows as well as the dorsal kineties, each two anlagen are formed intrakinetally; three to six caudal cirri are formed at the posterior end of the 5th dorsal kinety anlage; (e) the macronuclear nodules fuse into a single mass during the process.
