Hermann Fol

Hermann Fol (23 July 1845, Saint-Mandé – 13 March 1892) was a Swiss zoologist and the father of modern cytology. After studying medicine and zoology with Ernst Haeckel (1834–1919) at the University of Jena where he was a pupil of François Jules Pictet de la Rive (1809–1872) and René-Édouard Claparède (1832-1871), he accompanied Haeckel on a prolonged scientific journey (1866 and 1867) around the coasts of West Africa and of the Canary Islands. On his return to Europe he undertook medical studies in Heidelberg and completed them by obtaining his diploma in 1869 in Zurich and Berlin. In 1871 he studied planktonic fauna in Villefranche-sur-Mer on the recommendation of Carl Vogt (1817–1895). In 1876, he observed the penetration of a spermatozoon into an egg becoming thus a pioneer of the microscopic studies of fertilisation and cellular division. Oscar Hertwig also observed this in the same year. In 1878, Fol obtained a post of professor at the University of Geneva. In 1886, he resigned from his post in Geneva to devote himself entirely to his research in Villefranche-sur-Mer where, in 1880, he had established a small marine laboratory with Jules Henri Barrois (1852–1943). Then, financially aided by the French government to carry out a study of distribution of sponges on the Tunisian and Greek coasts, he departed Le Havre on his new yacht, l' Aster, on March 13, 1892, accompanied by several team members. After a stopover in Bénodet, the yacht disappeared at sea, and Fol was never seen again. Fol is credited with the invention of the barthometer. The barometer properly measured mercury, the pressure to which the apparatus had been submitted, and the determination of the depth of compressible liquid within the device. His invention consisted of a spherical glass reservoir of a liquid that is slightly compressible, such as water or ether. The single hole to the vessel is a capillary tube that corresponds with a minor reservoir filled with mercury.