On August 5th 2010 will be 30 years that Joachim Hammerling died (1901-1980) to whom science owes him the demonstration that genetic information of Eukaryote beings is contained in the nuclei of their cells. To be precise, he carried out his investigations in 2 species of Acetabularia: A. mediterranea and A. crenulata.

Acetabularia is a marine alga, a single-cell organism with only one nucleus. We could say that are gigantic in size as their size can be up to 10 cm. Every cell of Acetabularia is composed by a rhizoid (contains the nucleus) which is added to a hard surface, a stalk and an umbrella (both develop from the rhizoid when there are proper lighting conditions). The species A. mediterranea and A. crenulata can be distinguished easily for the shape of their umbrellas. The first one has a complete umbrella while the second one has a radially divided umbrella.

The experiment of Hammerling consisted of eliminating, under darkness conditions, the stalk and the umbrella of both species. Then he extracted the nuclei of the rhizoids and transplanted them to the rhizoids of the other specie. Once the lighting conditions went back to the normality, rhizoids developed stalks and umbrellas again, but this time they did according to the nucleus received instead of the initial rhizoid. Therefore the rhizoid of A.mediterranea developed umbels which corresponded to the nucleus of A. crenulata and the rhizoid of A. crenulata developed umbels corresponding to the nucleus of A.mediterranea.

With this discovery, he demonstrated that genetic information is contained in the nucleus of cells instead of their walls. After this discovery, James Watson and Francis Crick carried out investigations about structure, composition and mechanisms of copy of the genetic material.