Ultrastructural study of the teleost fish kidney

The ultrastructure of the stroma and vascularization of hematopoietic tissue in the kidney of two fresh water teleost fish are described. The presence of reticular and phagocytic reticular cells, similar to those in the bone marrow of higher vertebrates, and sinusoids and thin-walled arteries, support the idea of a phylogenetic relationship between this organ and the bone marrow. The kidney does not appear to be homologous with mammalian lymph nodes.