Walther Flemming identified chromosomal partitioning between mother and daughter cells. He saw that chromosomes were "doubled' when they appeared in prophase.
Flemming was the first person to detail the chromosomal movements in the process of mitosis. In 1879, he used aniline dyes to stain cells of salamander embryos. He was able to see the threadlike material as cells divide.
Much of what is known today about mitosis came from the observations by Flemming which were significant for later work in Meiosis and the theory of inheritance involving chromosomes.