1) Cyathodiniidae are ciliates morphologically characterized by the presence of a depression antero-ventrally opened, the pseudo-peristoma. Ciliation is represented by uniform cilia, arranged in transverse or oblique lines, inserted both on the external surface of the pseudo-peristoma, and onits internal surface. The Cyathodiniidae show clear nucleous duplicity, morphologically and functionally manifested. 2) The Cyathodiniidae, have not mouth and its nutrition is accomplished by osmose through a cellular membrane. 3) The Cyathodiniidae multiply by binary fission accompanied by lost of cilia and endogenous formation of two new ciliations, the plane of division is longitudinal or oblique or, according to the ideas of Chatton and Lwoff, perpendicularly to the cinetia direction. 4) Reorganisation is accomplished by endomixis which is accompanied by lost of cilia and endogenous formation of a new ciliature. 5) Endomixis is observed in individuals not differing from the neutral forms in its morphology and dimensions. 6) In the endomixis process the micronucleus, after 2 successive mitoses, form 4 nuclei, 3 of which degenerate, and the remaining forming, by division, a new micronucleus and the placenta which transform itself in a new macronucleus. 7) The process, in both genera forming the family, is identical, only differeing in the way of the degeneration of macronucleus and of the remains of the division of micronucleus. 8) Though in Cyathodinium the degeneration results from a picnose, in Cyathodinioides macronucleus and remains of micronucleus fision degenerate by disaggregation in granules, through the process of macronucleiform degeneration described by Ivanic. 9) Degeneration macronucleiform must be interpreted as an aborted evolution and not, as Ivanic suggests, an evidence of macronucleus being an organ in degeneration. 10) Cyathodiniidae are transmitted by cyst. 11) Cyathodinnidae must be considered as true Ciliates modified by parasite life, whose study must not be considered for the explanation of the phylogeny of this group. 12) Cyathodiniidae must be included in Order Holotrica, sub-order Astomatea.