How were chromosomes discovered?
The discovery of the chromosome was descriptive from the beginning and inseparably interwoven with the discoveries of the cell and the nucleus. All findings became possible only after Leeuwenhoek´s invention of the microscope in 1674. In 1831 Robert Brown described the ‘areola’ in orchids being constantly detectable in all cells. He called this areola’the nucleus of the cel’.1838 M. J. Schleiden´s incorrect epigenetic theory claimed that a cell-nucleus is created de novo from the fluid of the cell. This served as a classical antithesis to Edouard van Beneden´s 1883 discovery that chromosomes are individual entities. In 1842 Karl Wilhelm von Nägeli discovered subcellular structures that would later became known as chromosomes. He had observed the ‘idioplasma’, a network of string like bodies which he falsely assumed to form an interlinked network throughout the entire organism. In 1873 Schneider had described the indirect division of the nucleus with a ‘Kernfigur'(nuclear figure) and an ‘achromatic spindle’. In 1883, Edouard van Beneden found that after fertilization of the germ cells of the nematode Ascaris megalocephala the chromosomes of the male nucleus do not fuse with those of the oocyte nucleus. Therefore, they are distinct entities.This was the empirical foundation of Mendel´s rules, but their connection was found only several years later. Van Beneden did not yet use the word chromsome, which was later coined by Waldyer in 1888. The term reflected the staining behavior of chromosomes after using specific dyes.