Genevan naturalist. Conducted a series of studies on the freshwater polyp (or hydra), which he thought to be a new zoological species as he was unaware of a paper of 1702 in which the great Dutch naturalist Antoni van Leewenhoek (1632-1723) had already announced its discovery. Thanks to his consummate manual skill, Trembley managed to cut the hydra both horizontally and vertically, providing the experimental demonstration that each half could regenerate the missing part. Was in contact with leading scientists such as René-Antoine Ferchault de Réaumur (1683-1757), Charles Bonnet (1720-1793), and Lazzaro Spallanzani (1729-1799). Elected Fellow of the Royal Society of London in 1743; the following year, published his observations in Mémoires pour servir à l'histoire d'un genre de polypes d'eau douce (Leiden, 1744), a seminal text in the development of experimental zoology. Also studied other freshwater animals, and his discovery of the reproduction of certain types of polyps through gemmation was widely discussed by his contemporaries.