ABSTRACTReinvestigation of the type population of the sorocarp‐forming ciliateSorogena stoianovitchaeBradbury&Olive, 1980 using the Fernández‐Galiano technique and various electron‐microscopy techniques (scanning electron microscopy, freeze‐fracture and ultrathin sections) expands the observations reported in the original description of the species,Sorogena stoianovitchaeis a colpodid ciliate with oral ciliature consisting of 25 ciliated paroral dikinetids on the right and 3‐5 small adoral organelles on the left of an elongated and domed oral slit, resembling that of the genusPlatyophrya. Sorogena stoianovitchaedivides in the free swimming condition and not in a division cyst, as is the case in the colpodids sensu stricto (s. str.), e.g.Colpoda, Bresslaua.orTillina, As shown in a detailed light‐microscopy study, morphogenesis inS. stoianovitchaeis of the stomatic mode typical for certain colpodid ciliates. Based on the wealth of new information the phylogenetic position of S.stoianovitchaeis discussed at some length and arguments are given in favor of the following classifications:S. stoianovitchaeBradbury&Olive, 1980 currently sole member of the family Sorogenidae Bradbury&Olive, 1980; order Sorogenida Foissner, 1985;subclassColpodiaFoissner, 1985; class Colpodea Small&Lynn, 1981. This investigation facilitates the discovery of further members of this genus reported primarily from the tropical and subt