Removal of the corpuscles of Stannius from the European eel (Anguilla anguilla L.) is followed by a fall in the concentration of plasma sodium and a rise in that of potassium and of calcium (Fontaine, 1964; Chester Jones, Henderson & Butler, 1965). It seemed possible that the corpuscles secrete corticosteroids, possibly aldosterone (Fontaine, 1963; Leloup-Hatey, 1964). A large quantity of corpuscles were therefore analysed for steroidogenetic capacity.
Fresh viscera from about 5000 eels, when gutted alive for commercial purposes, were obtained in Billingsgate Market. The corpuscles, a ventral pair on the posterior kidney, were removed in the Department of Zoology, St Bartholomew's Hospital Medical School, where the preliminary experiments were done.
Four experiments were carried out consisting of incubation of chopped corpuscles in a shaking incubator under air at 37° for 3 hr. The medium, isotonic with eel plasma, is given by Sandor et al. (1965). The substrate was a