Early biologists observed that just before cell division, several short, stringy structures appeared in the nucleus of the cell. These structures are called chromosomes.

Here's why:

* Chromosomes are the carriers of genetic information. They contain DNA, which holds the instructions for building and maintaining an organism.

* During cell division, chromosomes must be copied and distributed equally to the daughter cells. This ensures that each new cell receives a complete set of genetic instructions.

* The stringy structures seen by early biologists are actually condensed chromosomes. During the early stages of cell division, the DNA within the nucleus is replicated and then tightly packaged into chromosomes. This condensation makes the chromosomes visible under a microscope.

So, the observation of these structures provided early evidence of the important role of chromosomes in cell division and heredity.