Skip to main content
Because of a lapse in government funding, the information on this website may not be up to date, transactions submitted via the website may not be processed, and the agency may not be able to respond to inquiries until appropriations are enacted.

The NIH Clinical Center (the research hospital of NIH) is open. For more details about its operating status, please visit

Updates regarding government operating status and resumption of normal operations can be found at

1879: Mitosis observed

Image of cells dividing Walter Flemming described chromosome behavior during animal cell division.

Flemming was one of the first cytologists and the first to detail how chromosomes move during mitosis, or cell division. Dividing cells had been observed almost forty years earlier by Carl Nageli, but he misinterpreted evidence of mitosis as something abnormal in the dead cells he'd observed. Flemming observed cell division in salamander embryos, where cells divide at fixed intervals. He developed a way to stain chromosomes to observe them clearly.

Ultimately, Flemming described the whole process of mitosis, from chromosome doubling to their even partitioning into the two resulting cells, in a book published in 1882. His terms, like prophase, metaphase and anaphase, are still used to describe the steps of cell division. His work helped form the basis of the chromosome theory of inheritance.


More Information

Diagram of Mitosis

To view the PDF on this page, you will need Adobe Reader. Download Adobe Reader

« Previous Event | Next Event »



Top of page

Last Reviewed: April 22, 2013