The Zoological Station of Naples was founded in 1872 by Anton Dohrn as a research institute for zoology and comparative anatomy. Although the original fields of interest were the morphology of vertebrates and comparative embryology, a department of physiology was added to the station in 1888. Osmoregulation in marine organisms has been extensively studied, notably by Bottazzi, who investigated chemical composition, electrical conductivity, surface tension, osmotic pressure and extracellular viscosity in circulating fluids in man and lower animals. Bottazzi classified aquatic animals into 2 groups, a distinction that is accepted today. More recent workers at the station include Bern, who made important contributions to the study of the essential role played by prolactin in regulation of hydromineral metabolism in euryhaline teleost fish in a freshwater environment.