Amitosis is an obsolete term describing EUKARYOTIC cell division without nuclear envelope breakdown and formation of well-visible mitotic spindle and condensed chromosomes. The division of unicellular eukaryotes formerly regarded as amitosis is called today closed mitosis. An exception is the division of ciliate macronucleus, which is not mitotic, and the reference to this process as amitosis may be the only legitimate use of the term today. In animals and plants which normally have open mitosis, the microscopic picture described in the 19th century as amitosis most likely corresponded to apoptosis, a process of programmed cell death associated with fragmentation of the nucleus and cytoplasm. Actually, even in the late 19th century cytologists mentioned that in larger life forms, amitosis is a "forerunner of degeneration".
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