The fine structure of the subcommissural cells and of Reissner's fibre in Myxine

Summary Reissner's fibre and the subcommisssural cells mainly from Myxine were investigated by light and electron microscope methods. The subcommissural cells carry several cilia and produce a chrome haematoxyphile secretion in the form of granules. It is probable that the nucleus as well as the mitochondria are involved in the synthesis of this material. The secretory release suggests an apocrine type in which the granules swell and form a fine-granulated, chrome haematoxyphile substance in the ventricle. Caudally in the subcommissural canal this material condenses to form Reissner's fibre, which in electron micrographs, except for a fine-granulated ground substance, does not show any structures, a limiting membrane or traces of cell organelles or remnants.Aided by grants from the Swedish Natural Science Research Council.