In spite of these ancient customs, the real nature of coral stayed mysterious for a long time and several fierce debates opposed supporters of coral being animal, vegetal or even mineral. It was not before the XVIIIth century, with work done by a young doctor, Jean-André Peyssonnel in Marseilles that the animal nature of coral was recognised. He wrote to the Director of the Science Academy, the famous scientist René-Antoine Perchault de Réaumur : " I noticed that what we believe to be the flower of this so-called plant is in reality an insect like a small nettle .. I was pleased to see the feet of this nettle move and, having warmed the water where the coral was, all the insects opened up" " (McConnel, 1990 ; Weinberg, 1993).

However, Réaumur, influenced by current beliefs, did not believe Peyssonnel's observations and criticised them. But the work of the Dutchman Abraham Trembly on green hydra, which had just demonstrated the animal nature of what was to be a near relative of coral, influenced Réaumur, and in the preface of his "Memories to help the history of Insects" (1742), in which he describes Trembley's for the first time, Réamur honours his work; "the care taken by Mr. Peyssonnel with his observations should have convinced me earlier that the flowers of the Count of MARSIGLI were really animals".
Coral finally became an animal.