<P> The concept of the eukaryote has been attributed to the French biologist Edouard Chatton (1883 - 1947). The terms prokaryote and eukaryote were more definitively reintroduced by the Canadian microbiologist Roger Stanier and the Dutch - American microbiologist C.B. van Niel in 1962 . In his 1938 work Titres et Travaux Scientifiques, Chatton had proposed the two terms, calling the bacteria prokaryotes and organisms with nuclei in their cells eukaryotes . However he mentioned this in only one paragraph, and the idea was effectively ignored until Chatton's statement was rediscovered by Stanier and van Niel . </P> <P> In 1967, Lynn Margulis provided microbiological evidence for endosymbiosis as the origin of chloroplasts and mitochondria in eukaryotic cells in her paper, On the origin of mitosing cells . In the 1970s, Carl Woese explored microbial phylogenetics, studying variations in 16S ribosomal RNA . This helped to uncover the origin of the eukaryotes and the symbiogenesis of two important eukaryote organelles, mitochondria and chloroplasts . In 1977, Woese and George Fox introduced a "third form of life", which they called the Archaebacteria; in 1990, Woese, Otto Kandler and Mark L. Wheeler renamed this the Archaea . </P> <P> In 1979, G.W. Gould and G.J. Dring suggested that the eukaryotic cell's nucleus came from the ability of Gram - positive bacteria to form endospores . In 1987 and later papers, Thomas Cavalier - Smith proposed instead that the membranes of the nucleus and endoplasmic reticulum first formed by infolding a prokaryote's plasma membrane . In the 1990s, several other biologists proposed endosymbiotic origins for the nucleus, effectively reviving Mereschkowsky's theory . </P> <P> Eukaryotic cells are typically much larger than those of prokaryotes having a volume of around 10,000 times greater than the prokaryotic cell . They have a variety of internal membrane - bound structures, called organelles, and a cytoskeleton composed of microtubules, microfilaments, and intermediate filaments, which play an important role in defining the cell's organization and shape . Eukaryotic DNA is divided into several linear bundles called chromosomes, which are separated by a microtubular spindle during nuclear division . </P>

How have eukaryotic cells contributed to the evolution of multicellular higher organisms