THE FINE STRUCTURE OF THE NUCLEAR ENVELOPE OF AMOEBA PROTEUS

The structure of the nuclear envelope of interphase animal cells has recently been described by Watson (1) as a double nuclear membrane containing circular pores which are formed by continuities between the inner and outer membranes. These pores or gaps appear at times to permit contact between the nucleoplasm and the cytoplasm. The fine structure of the nuclear envelopes of various tissues has also been previously discussed by other investigators (2, 3, 4). Pores were first seen in Amoeba proteus by Bairati and Lehmann (5) in preparations of fragmented membranes, and by Harris and James (6) in sectioned material. These investigators described the nuclear envelope as composed of two layers, an outer continuous one and a thicker, coarsely porous inner layer. More recently, Oreider, Kostir, and Frajola (7) also described the outer layer as continuous, although containing many pores which appear as tiny ring-like structures. The present investigation was undertaken to clarify further the relationships which exist between the two layers of the nuclear envelope.