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