Abstract
The topography and anatomy of a neurosecretory system in the eel, Anguilla japonica, to which a name preoptico-subcommissural neurosecretory system is proposed, being composed of some of the large nerve cells of the preoptic nucleus, the so-called Reissner's fiber and the subcommissural organ, are described. It is morphologically demonstrated that the Reissner's fiber represents significant union of thick axons arising from the pars magnocellularis of the preoptic nucleus, along which neurosecretory material is traceable posteriorly and dorsally as far up as to the subcommissural organ at the base of the epiphyseal stalk. The organ, being incorporated in the neurosecretory system concerned, is deduced to be of functional significance as a storage-release center.
