Symbiogenesis

"The differences between prokaryotes and eukaryotes are much more deep and fundamental than, for example, those between higher animals and higher plants. Numerous facts, especially those from cytology of simplest eukaryotic organisms, support the views of Kozo-Polyansky-Margulis. The eukaryotic cell, compared to a prokaryotic cell, is already rather some sort of 'supercell.' A specific 'assembly' of a complex eukaryotic system from already largely 'prefabricated parts' took place during the process of evolution."

Boris Mikhaylovich Kozo-Polyansky (1890-1957) graduated from Moscow University and in 1918 joined a Soviet university in his native Voronezh where he became a vice president as well as director of the local botanical garden.
Victor Fet is Professor of Biology at Marshall University, Huntington, West Virginia.
Lynn Margulis is a Distinguished University Professor in the Department of Geosciences at the University of Massachusetts-Amherst.
Peter H. Raven is President of the Missouri Botanical Garden.