Comparative study of the ovicell anatomy and morphology in three cribrimorph bryozoans belonging to the genus Puellina, revealed new facts in a favour of Lang´s (1921) hypothesis on the costate origin of the brood chambers in Cribrimporpha. Among others, a closed horizontal slit in the distal ooecial wall was found that can be considered as a rudiment of the existed passage between brooding room and epistege in ancestral forms. Acanthostegous brood chambers could be precursors of true ovicells. Possible scenaria of common as well as independent evolution of the ovicells among Calloporoidea and Cribrimorpha are considered.