Abstract: In order to re-evaluate the stability of the pattern formation and phylogenetic assignment of the marine ciliate Certesia quadrinucleata, the morphogenesis of a Chinese population sampled from a scallop-farming pond were studied. Based on live observation and protargol silver staining method, the morphogenetic results were summarized as follows:(1) the old AZM would be kept in situ by the proter; (2) the opisthe’s oral primordium appeared de novo under the pellicle;(3) the UMs primordium appeared on the surface of the cell and provide the first frontoventral cirri in both dividers;(4) the FVT-anlagen were formed in the primary five-anlagen way and generated the new cirri in the 3:3:3:3:3 manner;(5) the anlagen of left marginal row and dorsal kineties were formed intrakinetally within the old structures, where no caudal cirri were formed. And in the present investigation, pictures of morphogenesis in dorsal side were first referred. No difference was detected between the morphogenetic pattern of Chinese population and that of American one. Comparison of morphogenetic patterns among Certesia, Diophrys, Uronychia and Euplotes, all euplotid genera with detailed morphogenetic reports, revealed three common characters: (1) the oral primordium originated de novo apokinetally; (2) the fronto-ventral-transverse cirral anlagen developed with 5-streaks method; (3) dorsal kineties formed intrakinetally. In addition, Helix E10-1 secondary structures of SSrRNA gene sequences belonged to 49 species and nine genera were predicted, which showed that there were nine patterns in the order Euplotida. Interestingly, Diophrys, Diophryosis, Euplotidium, Uronychia and Certesia shared the same Helix E10-1 secondary structure pattern, however, four patterns were revealed in the genus Aspidisca. In contrast with the finding of Strüder-Kypke et al. that sequence length of Helix E10-1 was suborder unique within the class Oligohymenophorea, sequence length and secondary structure of Helix E10-1 within the order Euplotida even among congeneric species were variable, which indicated that euplotids were rather unique in ciliated evolutionary history.