Descriptions of the trophic morphology and stages of division are given for Pseudomicrothorax dubius, Glaucoma scintillans, Dexiotricha colpidiopsis and D. media (sp. n.) based upon Chatton-Lwoff and protargol silver staining. Electron microscopical observations of several stages of stomatogenesis are also included.

Five major stomatogenic events are chosen as the basis of comparison among the above three genera and other holotrichous ciliates. These characteristics, constituting a stomatogenic fingerprint for the organism or group of organisms, include :

1) the number of kinetosomal fields in the early oral primordium;

2) the site(s) of origin of the oral primordium;

3) the shape of primordia at different stages of stomatogenesis (principally, kinetal versus nonkinetal organization and existance of visible differentiation gradients);

4) the patterns of movements the primordia undergo at different stages of stomatogenesis, and

5) the amount of dedifferentiation in the parental buccal system during opisthe stomatogenesis.

Stomatogenic comparisons indicate a dichotomy in types of holotrich stomatogenesis. Pseudomicrothorax as well as chlamydodontid-dysteriid cyrtophorine gymnostomes, rhabdophorine gymnostomes and trichostomes appear to rely upon the kinety as a basis of oral primordium organization. By contrast, the oral primordium of hymenostomes and certain nassulid cyrtophorine gymnostomes does not show a kinetal organization.

Stomatogenic characteristics are given which distinguish among peniculine; tetrahymenine and scuticociliate hymenostomes.