De novo Origin of the Nuclear Membrane

Abstract

THE behaviour of the nuclear membrane in prophase and telophase is indeed one of the most attractive features of mitosis for the electron microscopist and cytologist¹. This was recently emphasized by Porter and Machado² in their review of the literature preceding their own electron microscope observations of mitotic onion root cells. In summary, the nuclear membrane or envelope is formed either by a coalescence of vesicles derived from the endoplasmic reticulum at the chromosome surface, or, as in the case of the onion cells, by slender lamellar units of the endoplasmic reticulum draping themselves around the chromosomes at the poles in telophase. Not one of these studies shed any light on the intriguing question posed by Bernhard³ regarding the possibility of a de novo origin for the nuclear membrane.