Transmission electron micrographs showing annulate lamellae from a frog oocyte. Annulate lamellae consist of stacked sheets of membrane containing closely packed structures resembling nuclear pores and are most frequently encountered in oocytes. Micrograph courtesy of Richard Kessel, Figures 164 (upper) and 165 (lower) from Chapter 4 (Nucleus) of 'The Cell, 2nd Ed.' by Don W. Fawcett M.D. A PDF copy of the accompanying chapter is available on the ASCB's BioEDUCATE website.