Experimental Manipulations

In the 1890s, German biologist Wilhelm Roux argued that just observing what happens in nature is not enough to understand life. Biological research must become experimental. The MBLcommunity took up this call.

In order to understand the role of cells in regeneration, for example, Thomas Hunt Morgan experimented with planarians and hydras, cutting them into bits and observing what happened next.

Illustration of process of planarian regeneration HoverTouch to magnify
Regeneration of planaria
MBLRare Books Collection

As whole organisms regenerated from the pieces, he asked whether the remaining cells had been transformed to take up different functions, or whether new cells had filled the void. He urged others to join him in testing interpretations.

Diagram of process of hydra regeneration HoverTouch to magnify
Regeneration of hydra
MBLRare Books Collection

Jacques Loeb took up the call and experimented with sea urchin egg cells by placing them in different concentrations of salt water. In the right conditions, egg cells began to divide, even without fertilization by sperm, a process called parthenogenesis.

Five figures of cells dividing (without fertilization by sperm) HoverTouch to magnify
Organisms developed from unfertilized eggs
MBLRare Books Collection
Figures of slightly pyramid-shaped cells dividing (without fertilization) HoverTouch to magnify
Cells dividing without fertilization
MBLRare Books Collection

Loeb also asked how he could manipulate environmental conditions, both inside and outside organisms, to learn how they affect cells and their functions.

As experimental biologists asked new questions, using the new methods, they generated observations that raised more questions. In particular: what is going on inside cells?